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  • 101.
    Janbakhsh, Setareh
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Department of Management and Engineering, Linköping University.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Experimental investigation of a ventilation system based on wall confluent jets2014In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 80, p. 18-31Article in journal (Refereed)
    Abstract [en]

    The flow behavior of isothermal and non-isothermal wall confluent jets (WCJ) ventilation system was investigated experimentally in a mock-up office environment. Two flow regions were identified: first, a primary region is developed below the supply device, with axis along the inlet wall, and a secondary wall-jet forms along the floor. The velocity and temperature fields were recorded by traversing a hot wire and thermistor anemometers for both primary and secondary regions. The results show self-similarity characteristic of the velocity and temperature profiles for both isothermal and non-isothermal WCJ. Maximum velocity decay and its spreading rate are linear and independent of the inlet airflow rate. Minimum temperature difference and its spread also show linear decay. The spreading rates for maximum velocity are similar in both the primary and secondary regions normal to the inlet wall and floor, respectively, which is consistent with previous studies on wall jets. The variation of draught rating is evaluated via mean velocity, turbulence intensity and temperature. Although the WCJ has slow velocity decay, which enables it to cover almost the entire floor of the test room, the draught is acceptable in the occupied zone according to ISO 7730. PMV (predicted mean vote) and PPD (predicted percentage dissatisfied) are presented for the occupied zone of the room. 

  • 102.
    Janbakhsh, Setareh
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Linköpings universitet.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Linköpings universitet.
    Investigation of design parameters for an air supply device based on wall confluent jets2015Article in journal (Other academic)
  • 103.
    Janbakhsh, Setareh
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Department of Management and Engineering, Linköping University, Linköping, Sweden .
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Department of Management and Engineering, Linköping University, Linköping, Sweden .
    Numerical study of a ventilation system based on wall confluent jets2014In: ASHRAE Transactions, ASHRAE , 2014, p. 272-284Conference paper (Refereed)
    Abstract [en]

    This study presents a numerical investigation of an air supply device based on wall confluent jets in a ventilated room. Confluent jets can be described as multiple round jets issuing from supply device apertures. The jets converge, merge, and combine at a certain distance downstream from the supply device and behave as a united jet or so-called "confluent "jets. The numerical predictions of the velocity flow field of isothermal confluent jets with three Reynolds-averaged Navier-Stokes (RANS) turbulence models (RNG k-ε, realizable k-ε, and SST k - ω) are reported in the present study. The results of the numerical predictions are verified with detailed experimental measurements by hot-wire anemometer and constant-temperature anemometers for two airflow rates. The box method is used to provide the inlet boundary conditions. The study of the airflow distribution showed that a primary wall jet (wall confluent jet) exists close to the supply device along the wetted-wall and a secondary wall jet is created after the stagnation region along the floor. It is presented that the flow field of the primary and secondary wall jet predicted by turbulence models is in good agreement with the experimental data. The current study is also compared with the literature in terms of the velocity decay and the spreading rate of the primary and secondary wall jet, the results of which are consistent with each other. Velocity decay and the spreading rate of the secondary wall jet in vertical and lateral directions were studied for different inlet airflow rates and inlet discharge heights. The comparative results demonstrate that the flow behavior is nearly independent of the inlet flow rate. Inlet discharge height is found to have impact close to the inlet, where the velocity decays faster when the jet discharges at a higher level. The decay tendency is similar as the jet enters into the room for all discharge heights. 

  • 104.
    Janbakhsh, Setareh
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Department of Management and Engineering, Linköping University.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Department of Management and Engineering, Linköping University.
    Numerical study of a ventilation system based on wall confluent jets2014In: HVAC & R RESEARCH, ISSN 1078-9669, E-ISSN 1938-5587, Vol. 20, no 8, p. 846-861Article in journal (Refereed)
    Abstract [en]

    This study presents numerical investigation of an air supply device based on wall confluent jets in a ventilated room. Confluent jets can be described as multiple round jets issuing from supply device apertures. The jets converge, merge, and combine at a certain distance downstream from the supply device and behave as a united jet, or so-called confluent jet. The numerical predictions of the velocity flow field of isothermal confluent jets with three Reynolds-averaged Navier-Stokes turbulence models (renormalization group k-epsilon, realizable k-epsilon, and shear stress transport k-omega) are reported in the present study. The results of the numerical predictions are verified with detailed experimental measurements by a hot wire anemometer and constant temperature anemometers for two airflow rates. The box method is used to provide the inlet boundary conditions. The study of the airflow distribution shows that a primary wall jet (wall confluent jet) exists close to the supply device along the wetted wall, and a secondary wall jet is created after the stagnation region along the floor. It is presented that the flow field of the primary and secondary wall jet predicted by turbulence models is in good agreement with the experimental data. The current study is also compared with the literature in terms of velocity decay and the spreading rate of the primary and secondary wall jet, the results of which are consistent with each other. Velocity decay and the spreading rate of the secondary wall jet in vertical and lateral directions were studied for different inlet airflow rates and inlet discharge heights. The comparative results demonstrate that the flow behavior is nearly independent of the inlet flow rate. Inlet discharge height is found to have impact close to the inlet, where the velocity decays faster when the jet discharges at higher level. The decay tendency is similar as the jet enters into the room for all discharge heights.

  • 105.
    Jiang, Bin
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Ma, Ding
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Yin, Junjun
    Department of Geography and Geographic Information Science, University of Illinois at Urbana and Champaign, Illinois, USA.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Spatial Distribution of City Tweets and Their Densities2016In: Geographical Analysis, ISSN 0016-7363, E-ISSN 1538-4632, Vol. 48, no 3, p. 337-351Article in journal (Refereed)
    Abstract [en]

    Social media outlets such as Twitter constitute valuable data sources for understanding human activities in the virtual world from a geographic perspective. This article examines spatial distribution of tweets and densities within cities. The cities refer to natural cities that are automatically aggregated from a country’s small street blocks, so called city blocks. We adopted street blocks (rather than census tracts) as the basic geographic units and topological center (rather than geometric center) to assess how tweets and densities vary from the center to the peripheral border. We found that, within a city from the center to the periphery, the tweets first increase and then decrease, while the densities decrease in general. These increases and decreases fluctuate dramatically, and differ significantly from those if census tracts are used as the basic geographic units. We also found that the decrease of densities from the center to the periphery is less significant, and even disappears, if an arbitrarily defined city border is adopted. These findings prove that natural cities and their topological centers are better than their counterparts (conventionally defined cities and city centers) for geographic research. Based on this study, we believe that tweet densities can be a good surrogate of population densities. If this belief is proved to be true, social media data could help solve the dispute surrounding exponential or power function of urban population density.

  • 106.
    Jin, Ruiqiu
    et al.
    Department of Atmospheric Science, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, China.
    Hang, Jian
    Department of Atmospheric Science, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, China.
    Liu, Shanshan
    Department of Atmospheric Science, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, China.
    Wei, Jianjian
    Department of Mechanical Engineering, The University of Hong Kong, Pokfulam, Hong Kong.
    Liu, Yang
    Department of Atmospheric Science, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, China.
    Xie, Jielan
    Department of Atmospheric Science, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, China.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Numerical investigation of wind-driven natural ventilation performance in a multi-storey hospital by coupling indoor and outdoor airflow2016In: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 25, no 8, p. 1226-1247Article in journal (Refereed)
    Abstract [en]

    This study employed two ventilation indexes: local mean age of air and air change rate per hour, to investigate wind-induced natural ventilation of 260 wards of a multi-storey hospital building in suburb of Guangzhou using computational fluid dynamics simulations. Using the surface-grid extrusion technique, high-quality hexahedral grid cells were generated for the coupled outdoor and indoor airflow field. Turbulence was solved by the renormalisation group k-model validated against experimental data with grid independence studies. Homogeneous tracer gas emission was adopted to predict room age of air. The air change rate of cross ventilation and single-sided ventilation can reach 30-160 h-1 and 0.5-7 h-1, respectively. Due to different locations of room openings on the balconies, natural ventilation of a room can be greatly better than its neighbouring room. The wind-induced cross ventilation highly depends on the distance from the room opening to the stagnation point and on the resulting pressure distribution on the target building surface. Furthermore, it is significantly influenced by the upstream buildings, the bent shape of the target building, and the prevailing wind directions. The coupled computational fluid dynamics methodologies with integrated ventilation indexes are useful for assessing the natural ventilation performance in other complex built environments. 

  • 107.
    Johansson, Ida
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Stenqvist, Christian
    EvalPart.
    Thollander, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Energy Efficiency Networks for SMEs - Program Theory and Ongoing Evaluation2017Conference paper (Other academic)
    Abstract [en]

    It is well known from literature and experienced by practitioners that various barriers are hindering energy management practices and energy efficiency improvements in (industrial) SMEs. With relatively low-cost shares for energy end-use and other priorities, energy management and energy efficiency measures seldom become an area for attention or investments. Consequently, large cost-effective energy efficiency potentials are left untapped. The situation is not pleasing given the European 2020 strategy for "smart, sustainable and inclusive growth", in which energy efficiency is to form a centerpiece with its abilities to provide multiple benefits that goes beyond energy cost savings.

    There are good practice examples where SMEs take part in networks and thereby join forces and cooperate to build energy management capacities. For the first time formalized and applied, on a regional level in Sweden, an Industrial Energy Efficiency Network (IEEN) model currently operates with the aim to attract the participation of at least 80 SMEs in ten local networks. An ongoing evaluation approach has been initiated with the main intention to review key activities in project implementation and make proposals for improvements.

    As a joint analysis between the project management and the external evaluator, this paper aims to outline characteristics of the particular IEEN model, present intermediate results from implementation and provide further insights from the evaluation. To our awareness, program theory and ongoing evaluation has so far not been applied to IEENs. Our results show that it clarifies the change process and helps to identify unique intermediate results and challenges faced in different phases of implementation. These are important lessons with potential to enhance understanding and improve knowledge dissemination within the community of industrial energy efficiency policy analysts, project developers and evaluators in the Asian-Pacific region.

  • 108.
    Johansson, Maria
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Energisystem.
    Improved Energy Efficiency and Fuel Substitution in the Iron and Steel Industry2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    IPCC reported in its climate change report 2013 that the atmospheric concentrations of the greenhouse gases (GHG) carbon dioxide (CO2), methane, and nitrous oxide now have reached the highest levels in the past 800,000 years. CO2 concentration has increased by 40% since pre-industrial times and the primary source is fossil fuel combustion. It is vital to reduce anthropogenic emissions of GHGs in order to combat climate change. Industry accounts for 20% of global anthropogenic CO2 emissions and the iron and steel industry accounts for 30% of industrial emissions. The iron and steel industry is at date highly dependent on fossil fuels and electricity. Energy efficiency measures and substitution of fossil fuels with renewable energy would make an important contribution to the efforts to reduce emissions of GHGs.

    This thesis studies energy efficiency measures and fuel substitution in the iron and steel industry and focuses on recovery and utilisation of excess energy and substitution of fossil fuels with biomass. Energy systems analysis has been used to investigate how changes in the iron and steel industry’s energy system would affect the steel plant’s economy and global CO2 emissions. The thesis also studies energy management practices in the Swedish iron and steel industry with the focus on how energy managers think about why energy efficiency measures are implemented or why they are not implemented. In-depth interviews with energy managers at eleven Swedish steel plants were conducted to analyse energy management practices.

    In order to show some of the large untapped heat flows in industry, excess heat recovery potential in the industrial sector in Gävleborg County in Sweden was analysed. Under the assumptions made in this thesis, the recovery output would be more than three times higher if the excess heat is used in a district heating system than if electricity is generated. An economic evaluation was performed for three electricity generation technologies for the conversion of low-temperature industrial excess heat. The results show that electricity generation with organic Rankine cycles and phase change material engines could be profitable, but that thermoelectric generation of electricity from low-temperature industrial excess heat would not be profitable at the present stage of technology development. With regard to fossil fuels substituted with biomass, there are opportunities to substitute fossil coal with charcoal in the blast furnace and to substitute liquefied petroleum gas (LPG) with bio-syngas or bio synthetic natural gas (bio-SNG) as fuel in the steel industry’s reheating furnaces. However, in the energy market scenarios studied, substituting LPG with bio-SNG as fuel in reheating furnaces at the studied scrap-based steel plant would not be profitable without economic policy support. The development of the energy market is shown to play a vital role for the outcome of how different measures would affect global CO2 emissions.

    Results from the interviews show that Swedish steel companies regard improved energy efficiency as important. However, the majority of the interviewed energy managers only worked part-time with energy issues and they experienced that lack of time often was a barrier for successful energy management. More efforts could also be put into engaging and educating employees in order to introduce a common practice of improving energy efficiency at the company.

  • 109.
    Johansson, Maria T.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Linköping University.
    Improved energy efficiency within the Swedish steel industry: the importance of energy management and networking2015In: Energy Efficiency, ISSN 1570-646X, E-ISSN 1570-6478, Vol. 8, no 4, p. 713-744Article in journal (Refereed)
    Abstract [en]

    The iron and steel industry is an energy-intensive industry that consumes a significant portion of fossil fuel and electricity production. Climate change, the threat of an unsecure energy supply and rising energy prices have emphasised the issue of improved energy efficiency in the iron and steel industry. However, an energy-efficiency gap is well recognised, i.e. cost-efficient measures are not implemented in practice. This study will go deeper into why this gap occurs by investigating energy-management practices at 11 iron and steel companies in Sweden. Energy managers at the steel plants were interviewed about how they perceived their own and their companies’ efforts to improve energy efficiency and how networking among energy managers influenced the efforts to improve energy efficiency. Reported barriers to improved energy efficiency were, for example, too long payback period, lack of profitability, lack of personnel, risk of production disruption, lack of time and lack of commitment. Only three out of the eleven companies had assigned a person to work full time with energy management, and some of the energy managers were frustrated with not having enough time to work with energy issues. Generally, the respondents felt that they had support from senior management and that energy issues were prioritised, but only a few of the companies had made great efforts to involve employees in improving energy efficiency. Networking among Swedish steel companies was administered by the Swedish Steel Producers’ Association, and their networking meetings contributed to the exchange of knowledge and ideas. In conclusion, Swedish steel companies regard improved energy efficiency as important but have much work left to do in this area. For example, vast amounts of excess heat are not being recovered and more efforts could be put into engaging employees and introducing a culture of energy efficiency.

  • 110.
    Johansson, Maria T.
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Linköping University.
    Söderström, Mats
    Electricity generation from low-temperature industrial excess heat: an opportunity for the steel industry2014In: Energy Efficiency, ISSN 1570-646X, E-ISSN 1570-6478, Vol. 7, no 2, p. 203-215Article in journal (Refereed)
    Abstract [en]

    Awareness of climate change and the threat of rising energy prices have resulted in increased attention being paid to energy issues and industry seeing a cost benefit in using more energy-efficient production processes. One energy-efficient measure is the recovery of industrial excess heat. However, this option has not been fully investigated and some of the technologies for recovery of excess heat are not yet commercially available. This paper proposes three technologies for the generation of electricity from low-temperature industrial excess heat. The technologies are thermoelectric generation, organic Rankine cycle and phase change material engine system. The technologies are evaluated in relation to each other, with regard to temperature range of the heat source, conversion efficiency, capacity and economy. Because the technologies use heat of different temperature ranges, there is potential for concurrent implementation of two or more of these technologies. Even if the conversion efficiency of a technology is low, it could be worthwhile to utilise if there is no other use for the excess heat. The iron and steel industry is energy intensive and its production processes are often conducted at high temperatures. As a consequence, large amounts of excess heat are generated. The potential electricity production from low-temperature excess heat at a steel plant was calculated together with the corresponding reduction in global CO2 emissions.

  • 111.
    Joudi, Ali
    et al.
    Energy Technology, Dalarna University, Falun, Sweden; SSAB Europe, Borlänge, Sweden.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Svedung, Harald
    Energy Technology, Dalarna University, Falun, Sweden; SSAB Europe, Borlänge, Sweden.
    Rönnelid, Mats
    Energy Technology, Dalarna University, Falun, Sweden.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Energy Systems, Linköping University, Linköping, Sweden.
    Numerical and experimental investigation of the influence of infrared reflective interior surfaces on building temperature distributions2017In: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 26, no 3, p. 355-367Article in journal (Refereed)
    Abstract [en]

    Radiative properties of interior surfaces can affect not only the building heat flux but also the indoor environment, the latter of which has not been thoroughly investigated. The aim of this study is to analyse the effect of surface emissivity on indoor air and surface temperature distributions in a test cabin with reflective interior surfaces. This was done by comparing experimental and simulation data of the test cabin with that of a normal cabin. This study employs transient computational fluid dynamics (CFD) using re-normalisation group (RNG) k-epsilon model, surface-to-surface radiation model and an enhanced wall function. Boundary conditions were assigned to exterior surfaces under variable outdoor conditions. The numerical and the measurement results indicate that using interior reflective surfaces will affect the indoor air temperature distribution by increasing the vertical temperature gradient depending on the time of the day. CFD simulations with high spatial resolution results show increased interior surface temperature gradients consistent with the increased vertical air temperature gradient. The influence of reflective surfaces is potentially greater with higher indoor surface temperature asymmetry. The vertical indoor air temperature gradient and surface temperatures are important parameters for indoor thermal comfort.

  • 112.
    Kabanov, Alexey
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Livslängd hos keramisk fiber i elektriska industriugnar2018Independent thesis Basic level (university diploma), 180 HE creditsStudent thesis
    Abstract [en]

    Today's energy use is reduced as a result of current environmental policy, which requires industries to energy-efficient their manufacturing processes and reduce the use of fossil fuels. The goal of this is to reduce final energy consumption to 50% and balance future electricity supply. Energy efficiency and development are the most important aspects of industrial processes that lead to sustainability and change in environmental impact.

     

    Developments in refractory insulation materials gave great opportunities for steel industries to increase the quality of material production and reduce heat losses in furnace plants. This leads in particular to increased competitiveness and reduced energy costs. Energy saving savings create room for new investments that are used to improve the steel industry's efficiency.

     

    Insulation materials are currently used in most modern industrial heating furnaces and the problems with these insulations that they have a limited service life which imposes more accurate maintenance and higher investment costs. There are no specific methods today that can control the aging of the insulation and are limited only to visual inspection at decommissioned furnaces that can be carried out only on special occasions with planned production shutdowns.

     

    The inspections of the oven's lining usually detect larger problems than had been forecast. This causes many unplanned repairs due to production delays that affect the company's economy. This study will investigate the insulation quality of electrical furnaces on the subject line in Söderfors. During this work, risk zones will be located where the insulation is most affected during production and how a worn wool affects the efficiency and energy consumption of the oven at the company.

     

    The purpose of this study is to elaborate methods based on predictive maintenance, production efficiency, and efficiency of the ovens, helping the company to have better control over its facilities that provide room for new investment, which primarily aims to balance the energy use of heating ovens, but mainly to respond on the question of how fast ceramic wool degradation occurs.

     

    The result achieved in this work describes the aging of wool that does not occur constantly but varies due to a number of conditions and that the right amount of chemical composition determines the insulation quality. In order to be able to follow the aging, a new measurement method is applied in practice that provides an accurate state of insulation condition and can predict future accidents.

  • 113.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Experimental Evaluation of Intermittent Air Jet Ventilation Strategy : Cooling Effect Analysis2016In: IAVEQ 2016: 9th International Conference on Indoor Air Quality Ventilation & Energy Conservation In Buildings, Songdo, South Korea: IAQVEC Committe , 2016Conference paper (Other academic)
    Abstract [en]

    In the built environment climate control is the most energy intensive component and in trying to reduce energy use, occupant satisfaction is compromised.  Identifying strategies that balance the energy use and occupant satisfaction is important. One strategy is optimizing elevated air movements with intermittent air jet strategy (IAJS). The strategy enhances human convective and evaporative cooling resulting in good indoor climate and low energy use. Understanding the systems cooling capabilities is thus important to justify its practical implementation. In this paper, the potential cooling effect of the strategy is estimated with different calculation methods: thermal manikin measurements, measurements with thermal comfort data logger and estimation of the cooling effect with a web application tool (CBE thermal comfort tool). As shown in this study, the obtained cooling effect may differ by as much as 1 oC between estimation/calculation methods. This may have both implications on energy use and occupant satisfaction. 

  • 114.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Experimental study of an intermittent ventilation system in high occupancy spaces2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Spaces with high occupancy density like classrooms are challenging to ventilate and use a lot of energy to maintain comfort. Usually, a compromise is made between low energy use and good Indoor Environmental Quality (IEQ), of which poor IEQ has consequences for occupants’ health, productivity and comfort. Alternative strategies that incorporate elevated air speeds can reduce cooling energy demand and provide occupant’s comfort and productivity at higher operative temperatures. A ventilation strategy, Intermittent Air Jet Strategy (IAJS), which optimizes controlled intermittent airflow and creates non-uniform airflow and non-isothermal conditions, critical for sedentary operations at elevated temperatures, is proposed herein.

    The primary aim of the work was to investigate the potential of IAJS as a ventilation system in high occupancy spaces. Ventilation parameters such as air distribution, thermal comfort and indoor air quality are evaluated and the system is compared with a traditional system, specifically, mixing ventilation (MV). A 3-part research process was used: (1) Technical (objective) evaluation of IAJS in-comparison to MV and displacement ventilation (DV) systems. (2) An occupant response study to IAJS. (3) Estimation of the cooling effect under IAJS and its implications on energy use. All studies were conducted in controlled chambers.

    The results show that while MV and DV creates steady airflow conditions, IAJS has  cyclic airflow profiles which results in a sinusoidal temperature profile around occupants. Air distribution capability of IAJS is similar to MV, both having a generic local air quality index in the occupied zone. On the other hand, the systems overall air change rate was higher than a MV. Thermal comfort results suggest that IAJS generates comfortable thermal climate at higher operative temperatures compared to MV. Occupant responses to IAJS show an improved thermal sensation, air quality perception and acceptability of indoor environment at higher temperatures as compared to MV. A comparative study to estimate the cooling effect of IAJS shows that upper HVAC setpoint can be increased from 2.3 – 4.5 oC for a neutral thermal sensation compared to a MV. This implies a substantial energy saving potential on the ventilation system. In general, IAJS showed a potential for use as a ventilation system in classrooms while promising energy savings.  

  • 115.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Ameen, Arman
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Hayati, Abolfazl
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Yang, Bin
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Cooling energy simulation and analysis of an intermittent ventilation strategy under different climates2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 156, p. 84-94Article in journal (Refereed)
    Abstract [en]

    Energy use on heating, ventilation and air conditioning (HVAC) accounts for about 50% of building energy use. To have a sustainable built environment, energy efficient ventilation systems that deliver good indoor environmental quality are needed. This study evaluates the cooling energy saving potential of a newly proposed ventilation system called Intermittent Air Jet Strategy (IAJS) and compares its performance against a mixing ventilation (MV) system in a classroom located in three cities with different climates, Singapore with ‘hot and humid’, Ahvaz with ‘hot and dry’ and Lisbon with “moderate” climate. The results show a significant reduction of cooling energy need and flexibility in control strategies with IAJS as a primary system in hot and humid climates like Singapore. Hot and dry climate with short cool periods like Ahvaz show possible application and considerable energy savings with IAJS as a primary system under optimized variable setpoints, but moderate climates have an increased risk of occupant discomfort likely due to increased draft especially during the cool season.  Thus, IAJS as a secondary system that operates only during cooling season may be conducive for moderate climates like Lisbon. Additionally, the results show that supply fan energy savings can also be realized if well implemented. 

  • 116.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Ameen, Arman
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Yang, Bin
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Energy simulation and analysis of an intermittent ventilation system under two climates2017In: 10th International Conference on Sustainable Energy and Environmental Protection: Energy Efficiency / [ed] Krope J., Olabi, A.G., Goričanec D. & Božičnik S., Maribor: University of Maribor Press , 2017, p. 1-10Conference paper (Refereed)
    Abstract [en]

    Energy use on heating, ventilation and air conditioning (HVAC) accounts for about 50% of total energy use in buildings.  Energy efficient HVAC systems that do not compromise the indoor environmental quality and at the same time meet the energy reduction directives/policies are necessary and needed. The study herein, evaluates the energy saving potential of a newly proposed ventilation system in spaces with high occupancy density, called Intermittent Air Jet Strategy (IAJS). The aim of the study was to evaluate through simulations the potential energy savings due to IAJS as compared to a mixing ventilation (MV) system in a classroom located in a ‘hot and humid’ climate (Singapore), and in a ‘hot and dry’ climate (Kuwait). The analysis is based on IDA Indoor Climate Energy simulation software. The results herein demonstrate significant reduction of cooling energy use of up 54.5% for Singapore and up to 32.2% for Kuwait with IAJS as compared to MV. Additionally, supply fan energy savings can also be realized if well implemented.

  • 117.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Keus van de Poll, Marijke
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Ljung, Robert
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Disruption of writing by background speech: a classroom experiment2014Conference paper (Other academic)
    Abstract [en]

    Irrelevant background speech impairs cognitive capabilities such as writing. Laboratory studies wherein participants were tested alone in sound attenuated rooms, showed that ordinary speech, even with relatively low intelligibility (Keus van de Poll, Ljung, Odelius, Sörqvist, 2014), is more distracting than meaningless speech (Sörqvist, Nöstl, & Halin, 2012). Yet, so far research has paid little attention to the manifestation of these effects in classroom environments. The aim of the present study was to investigate the effects of irrelevant background speech on writing in a realistic classroom setting. The hypothesis was that irrelevant background speech would have distracting effects on text production, especially on writing fluency and typing errors. In an experimental within-subjects design, college students (in groups of 10-12 participants), sitting in a classroom, were asked to write short essays (5 minutes per essay) in the software program scriptlog. One essay was written in silence and one in the presence of background speech. As expected, background speech had a (slight) effect, although more participants are needed to increase the experimental power. Comparisons with previous studies on the effects of speech on writing are made and future directions are discussed.

  • 118.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Keus van de Poll, Marijke
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Ljung, Robert
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology. Linnaeus Centre HEAD, Swedish Institute for Disability Research, Linköping University, Sweden.
    The effect of heat stress on writing performance in a classroom2014In: Indoor Air 2014 - 13th International Conference on Indoor Air Quality and Climate, 2014, p. 183-188Conference paper (Refereed)
    Abstract [en]

    Studies have shown that heat stress impairs performance. This depends on the mental loading capacity of the task performed and the exposure time. This is a study of a common task in schools and offices: writing task. It also analyses the occupants’ perceived thermal comfort. The experiment was done in two heat conditions: 20 and 25 centigrade. The between participant design was used. ScriptLog was used to perform the writing task, while questionnaires and a Sudoku task were paper based tasks. The results show that the predicted mean vote (PMV) between conditions was significant (p<0.02) and participants perceived the 20 º C condition to be draughty. They however preferred a little more air movements in both conditions. Writing performance only showed a significant difference (p = 0.03) on deleted characters but the other variables considered did not show any significant differences but showed a strong tendency that with a long exposure time it would eventually be impaired.  This shows that writing despite being a complex task is not a high mental loading task and is not quickly impaired by heat stress.

  • 119.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Liu, Shichao
    University of California, Berkeley, USA.
    Schiavon, Stefano
    University of California, Berkeley, USA.
    Potential adaptive behaviour to counteract thermal discomfort in spaces with displacement ventilation or underfloor air distribution systems2016In: Proceedings of the 14th international conference of Indoor Air Quality and Climate, Ghent, 2016Conference paper (Refereed)
    Abstract [en]

    Building occupants behave in various adaptive ways to restore thermal comfort when in a state of thermal discomfort. These adaptive actions affect building energy use and indoor environmental quality. This paper reports part of a draft risk study, here we focus on potential adaptive behaviour to counteract discomfort in rooms with displacement ventilation (DV) and underfloor air distribution (UFAD) systems. The most likely adaptive behaviours to be taken are: adjust clothing, open/close windows, adjust thermostat and change workstation. No conclusive relationship was found on whether these behaviours are influenced by overall or ankle thermal sensation. Females stated more frequently than males that they would open/close windows, while more males expressed the intention to use heaters and complain to building managers.

  • 120.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Entrainment and its Implications on Microclimate Ventilation Systems: Scaling the Velocity and Temperature Field of a Round Free Jet2019In: Indoor Air, ISSN 0905-6947, E-ISSN 1600-0668, Vol. 29, no 2, p. 331-346Article in journal (Refereed)
    Abstract [en]

    Research on microclimate ventilation systems, which mostly involve free jets, point to delivery of better ventilation in breathing zones. While the literature is comprehensive, the influence of contaminant entrainment in jet flows and its implications on the delivery of supplied air is not fully addressed. This paper present and discuss entrainment characteristics of a jet issued from a round nozzle (0.05 m diameter), in relation to ventilation, by exploring the velocity and temperature fields of the jet flow. The results show a trend suggesting that increasing the Reynolds number (Re) reduces ambient entrainment. As shown herein, about 30% concentration of ambient air entrained into the bulk jet flow at Re 2541 while Re 9233 had about 13% and 19% for Re = 6537/12026 at downstream distance of 8 diameters (40 cm). The study discusses that “moderate to high” Re may be ideal to reduce contaminant entrainment, but this is limited by delivery distance and possibly the risk of occupant discomfort. Incorporating the entrainment mixing factor (the ratio of room contaminants entrained into a jet flow) in performance measurements is proposed and further studies are recommended to verify results herein and test whether this is general to other nozzle configurations.

    The full text will be freely available from 2019-11-30 00:01
  • 121.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Measurement of Entrainment into an Axisymmetric Jet using Temperature as a Tracer: A Pilot Study2018In: Excellent Indoor Climate and High Performing Ventilation / [ed] Risto Kosonen, Mervi Ahola and Jarkko Narvanne, 2018, p. 397-402Conference paper (Refereed)
    Abstract [en]

    The current extended abstract is a pilot study of an ongoing experimental and theoretical investigation of ambient entrainment of room air into an axisymmetric free jet using temperature as a tracer. The project aims to investigate, by revisiting the concepts and fundamentals of axisymmetric free Jets and entrainment in ventilation applications, particularly focusing on how to optimize performance of low mixing air distribution systems and to test methods of measuring entrainment in such systems. The study aims to explore a scalar field method using temperature as a tracer to estimate entrainment in axisymmetric free Jets. The results obtained show jet characteristics that slightly differ from what is reported in velocity field measurements and other scalar field studies. Thus, a call is made herein for further investigations to understand entrainment and appropriate methods to determine jet characteristics and its mixing effect. Additionally, more studies are needed to verify whether earlier results are representative of entrainment conditions for low mixing ventilation systems whose operation mode depend on near-filed characteristics of jets.

  • 122.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Sattari, Amir
    School of Technology and Business Studies, Dalarna University, Sweden.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, BMG laboratory.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Experimental study on contaminant entrainment in air distribution systems with free jets2017In: Healthy Buildings Europe 2017, ISIAQ , 2017, article id 0040Conference paper (Refereed)
    Abstract [en]

    This is a preliminary study to an ongoing experimental and theoretical study of ambient entrainment of room air into axisymmetric free jets. The study herein aims to understanding characteristic behaviour of free jets, especially in low mixing ventilation technologies in order to get the best of such applications. In this paper, we explore the interaction of a free jet and its ambient, the effect on jet development, characteristics and behaviour at different Reynold numbers. Measurements were done with Particle Image Velocimetry (PIV) under isothermal conditions. As shown, at lower Reynolds numbers the jet is mostly laminar but is unstable consequently shortening the penetration distance into the ambient. As the Reynolds numbers increase the instability reduces and the penetration distance increases, but entrainment increases as vortices are generated closer to the nozzle exit. The current study suggests that’s further investigation is needed to define limits within which low and high mixing can be achieved with free jets, as this will have practical implications on optimization and implementation of free jets.

  • 123.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Center for the Built Environment, University of California, Berkeley, Berkeley CA, USA.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Experimental Evaluation of Intermittent Air Jet Ventilation Strategy: Cooling effect and the associated energy saving2016Conference paper (Refereed)
    Abstract [en]

    The potential to reduce building energy demand is high especially on building services like ventilation and air conditioning. This potential lies in identifying ventilation strategies that can provide both the required indoor climate and lower the energy use. One of the strategies is optimizing elevated air movements to enhance human convective and evaporative cooling which, as shown in literature, results in reduced energy use on cooling. This paper evaluates the cooling potential and the resulting energy saving of a novel air supply system called intermittent air jet strategy (IAJS). As shown in this study, IAJS with velocities of 0.4 m/s at the breathing height provides a cooling effect equivalent to reducing the ambient temperature in a mixing ventilation system by up to 1.5 oC to achieve a neutral sensation. This translates to a 13% reduction on the cooling demand. The strategy is also shown to have an energy saving potential of up to 50% on the supply fan. 

  • 124.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Center for the Built Environment, University of California, Berkeley, Berkeley CA, USA.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Keus van de Poll, Marijke
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Ljung, Robert
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    The influence of heat, air jet cooling and noise on performance in classrooms2015In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 14, no 3, p. 321-332Article in journal (Refereed)
    Abstract [en]

    The quality of indoor environments influences satisfaction, health, and work performance of the occupants. Additional understanding of the theoretical and practical value of individual indoor parameters in relation to health and performance aids indoor climate designers to obtain desired outcomes. This also results in expenditure savings and increased revenue: health care and improved productivity. Here, we report two experiments that investigated how heat, cooling strategy and background noise influence performance in a full-scale classroom mockup setting. The results show that heat and background noise are detrimental to logic-based tasks and to writing, whilst cooling manipulations can protect performance. Implications for indoor environment design are discussed.

  • 125.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Ljung, Robert
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Sorqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology. Linnaeus Centre HEAD, Swedish Institute for Disability Research, Linköping University, Sweden.
    Perception of intermittent air velocities in classrooms2014In: Indoor Air 2014 - 13th International Conference on Indoor Air Quality and Climate, 2014, p. 189-191Conference paper (Refereed)
    Abstract [en]

    Classrooms normally host a large number of people and the heat generated provides a challenge cool. Traditional cooling methods by increased low temperature supply airflow rate or use of heat sinks are expensive and mostly inefficient. The strategy of controlled air movements in the occupied zone may prove cheaper and desirable. This research investigates recirculation of room air to provide intermittent velocity cooling in classrooms. The objective of this experiment was to assess how occupants perceive the recirculated intermittent air velocity conditions in classrooms and when the variations should be introduced in the room for optimal results. This was done with a between participant design, accessing how they perceived indoor air quality (IAQ) and the thermal comfort in two velocity conditions: constant low air velocity condition (< 0.15 m/s) and intermittent air velocity condition (0.4 m/s). As shown here; intermittent air velocity has a positive effect on the perceived thermal comfort (p < 0.04) and perception of air quality: less draughty and improved humid perception. The participants perceived the conditions with intermittent velocity to give comfortable feelings and better air quality.  The variations also showed better performance if they were provided at the start of occupancy as opposed to during or after a temperature build up. This strategy can be used in environments where it is rather uneconomical to provide cooling like spaces hosting a group of people: movie theatres, auditoriums, classrooms and perhaps in restaurants.

  • 126.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Ljung, Robert
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Experimental evaluation of an intermittent air supply system – Part 2: Occupant perception of thermal climate2016In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 108, p. 99-109Article in journal (Refereed)
    Abstract [en]

    A newly proposed intermittent air jet strategy (IAJS) provides satisfactory indoor climate while promising a substantial energy saving potential, as shown in technical (objective) measurements. The strategy creates non-uniform airflow and non-isothermal conditions critical for sedentary operations at elevated temperatures. The current study explored human perception of thermal environment under an IAJS. Assessment of thermal sensation, thermal comfort, and thermal acceptability were collected based on responses from 36 participants. Participants sat in a classroom setup and performed sedentary work. Their clothing had an insulation of 0.51 clo (T-shirt on upper body). Participants were exposed to homogeneous (v < 0.15 m/s) and nonhomogeneous (0.4 m/s < v < 0.8 m/s) velocity conditions across three temperature conditions: 22.5 °C, 25.5 °C and 28.5 °C. The participants found air speeds to be undesirable at lower temperatures, but reported an improved thermal sensation, comfort and acceptability at higher temperatures. As shown here, IAJS generated neutral operable conditions between 24.8 °C and 27.8 °C, within an air speed range of 0.4 m/s to 0.8 m/s. Additionally, air movements induced thermal alliethesia resulting in improved comfort and acceptance of the thermal climate even at lower air speeds in warm temperature conditions. Hence, the current study supports the energy saving potential with IAJS in view of the human perception of the indoor environment.

  • 127.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Ljung, Robert
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Human perception of room temperature and intermittent air jet cooling in a classroom2017In: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 26, no 4, p. 528-537Article in journal (Refereed)
    Abstract [en]

    Environments with high temperatures and under steady conditions are perceived poor. The introduction of airflow variations in such environments improves the perception. However the risk of draught is high and to avoid this, variations in high velocity supply is used. This method is far more energy efficient than cooling the entire space as only the occupants are cooled. This paper discusses two studies on occupant cooling conducted at the University of Gävle.  The experiments were performed in a full scale mockup classroom and a total of 85 students participated. In Study 1, students sat in a classroom for about 60 minutes in one of two heat conditions: 20 and 25 º C. In Study 2, the indoor parameters of 25 º C were maintained but airflow variation in the sitting zone was manipulated. In both studies, the participants performed various tasks and answered questionnaires on their perception of the indoor climate. As shown here, higher room temperature deteriorates human perception of the indoor climate in classrooms, and the use of intermittent air jet cooling improves the perception of indoor climate just like cooling by reducing the room air temperature. This study contributes to further knowledge of how convective cooling can be used as a method of cooling in school environments so as to improve on building energy use. 

  • 128.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Center for the Built Environment, University of California, Berkeley, USA.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Experimental evaluation of an intermittent air supply system: Part 1: Thermal comfort and ventilation efficiency2016In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 95, p. 240-250, article id 4263Article in journal (Refereed)
    Abstract [en]

    Spaces with high occupancy density e.g.; classrooms, auditoriums and restaurants, provide challenges to ventilate at a lower energy use due to elevated temperatures. To meet occupants’ thermal comfort requirements traditional systems use a lot of energy. Alternative ventilation strategies that optimize high air movements in the occupied zone allow human activities at elevated temperatures while attaining improve occupants’ perception and acceptance of the indoor climate at a low energy use. This paper presents an experimental evaluation of a novel ventilation strategy for high occupancy spaces that provides fresh air and thermal comfort in the sitting zone through a controlled intermittent air jet system. The strategy uses ceiling mounted high momentum air jet diffusers (AJD) made from ventilation duct fitted with nozzles that generate confluent jets. The jets coalesce into a single two-dimensional jet which is directed downwards in the sitting zone. This paper presents an experimental evaluation/analysis of the proposed system with regard to ventilation efficiency and thermal comfort measurements in a classroom mockup. Results show that the system qualifies to be used as a primary ventilation system and has local air change index > 1 inside the jet, and a ventilation efficiency > 50%. The system also provides better thermal climate than mixing and displacement ventilation at elevated temperatures.

  • 129.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Yang, Bin
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Occupants’ perception of air movements and air quality in a simulated classroom with an intermittent air supply system2019In: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 28, no 1, p. 63-76Article in journal (Refereed)
    Abstract [en]

    The study reported herein builds on occupant response to an intermittent air jet strategy (IAJS), which creates periodic airflow and non-isothermal conditions in the occupied zone.  Previous research has highlighted the benefits of IAJS on thermal climate and supports energy saving potential in view of human thermal perception of the indoor environment. In this study, the goal was to explore occupant acceptability of air movements and perceived indoor air quality, and to determine a way of assessing acceptable air movement conditions under IAJS. Thirty-six participants were exposed to twelve conditions: three room air temperatures (nominal: 22.5, 25.5 and 28.5 oC), each with varied air speeds (nominal: <0.15 m/s under mixing ventilation (MV), and 0.4, 0.6 and 0.8 m/s under IAJS) measured at the breathing height (1.1 m). The results show that participants preferred low air movements at lower temperatures and high air movements at higher temperatures. A model to predict percentage satisfied with intermittent air movements was developed, and predicts that about 87% of the occupants within a thermal sensation range of slightly cool (-0.5) to slightly warm (+0.5), in compliance with ASHRAE standard 55, will find intermittent air movements acceptable between 23.7 oC and 29.1 oC within a velocity range of 0.4 – 0.8 m/s.  IAJS also improved participants’ perception of air quality in conditions deemed poor under MV. The findings support the potential of IAJS as a primary ventilation system in high occupant spaces such as classrooms. 

  • 130.
    Karimipanah, Taghi
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Larsson, Ulf
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Investigation of flow pattern for a confluent-jets system on a workbench of an industrial space2014In: Indoor Air 2014: 13th International Conference on Indoor Air Quality and Climate, 2014, p. 192-199Conference paper (Refereed)
    Abstract [en]

    A new air supply terminal based on confluent jets was installed on a workbench, in vicinity of a CNC machine, of an industrial space. The flow pattern and temperature field was carried out by CFD calculations and infrared camera imaging technique. A main goal of this technique is to save energy therefore the jet should distribute the air where it is desired. This is possible because the confluent jets system uses the benefits of both mixing (high momentum for better spreading of the air jet) and displacement (cleaner air in occupied zone). The results show that thermal comfort and air quality analysis relies on consistent facts and is in good agreements with the existed standards. It was shown that the supply terminal is able to spread the fresh air to the needed work area. This is an advantage of the high momentum air distribution system used in this investigation.

  • 131.
    Karlsson Falk, Susanne
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Identifiering av energianvändningen hos en kontorsfastighet i en svensk tätort: - en fallstudie med beräkningsinslag2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The current climate changes require a global response immediately. Every year the use of energy increases, which means that more and more greenhouse gases are released. Which in turn helps accelerate global warming. To reduce the energy use will not be an easy task for mankind. Household and service accounts for about 40% of Sweden’s energy use, and office buildings prove to be among the most energyintensive. Previous research shows that heat-, ventilation- and cooling systems along with lightning are the systems that provide the highest energy consumption and that there is also a great savings potential. In this study, the energy use of a property in a Swedish urban area has been investigated and how the energy is being used by the different systems has been identified. The purpose of this research is to see which measures can give the greatest cost-effective savings. Method used is a case study, which was an energy survey, combined with a literature review of relevant information. Data collection consisted of information from the property owner,inspection of the building and electricity measurements. The result shows that there are great savings to be made. If proposed measures are implemented (see section 4.6), energy consumption for heating can be reduced by 144,9 MWh/year or 32,4%. Energy used by lightning can be reduced by 46,8 MWh/year or 40,3%and other measures can be reduced by 41 MWh/year or 53%. Measures that can be performed for free were considered the most cost-effective, such as lowering the indoor temperature or turning off equipment between days. For measures with investment cost, isolation of the attic was considered most cost -effective with a payoff time of 5 years. To invest in sun cells would reduce the bought electricity with 56,8 MWh/yr. Due to lack of information, assumptions and simplifications were made that could have caused sources of error.

  • 132.
    Khosravi Bakhtiari, Hossein
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Department of Construction, Gavlefastigheter Company, Gävle, Sweden.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Akander, Jan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Thermal Comfort in Office Rooms in a Historic Building with Modernized HVAC Systems2018In: Proceedings of the 4th International Conference On Building Energy & Environment, COBEE 2018: RMIT University, Melbourne, Australia, Feb 5-9th 2018 / [ed] Kiao Inthavong,Chi Pok Cheung, Guan Yeoh, Jiyuan Tu, Melbourne: Conference On Building Energy & Environment , 2018, p. 683-688, article id 230Conference paper (Refereed)
    Abstract [en]

    SUMMARY

    Envelopes with low thermal performance are common characteristics in European historic buildings, leading to higher energy demand and insufficient thermal comfort. This paper presents the results of a study on thermal comfort in the historic office building of City Hall in Gävle, Sweden. It is equipped with two modern heat recovery ventilation systems with displacement ventilation supply devices in offices. District heating network heats the building via pre-heat supply air and radiators. Summer cooling comes from electric heat pump, rejecting heat into the exhaust ventilation air. A building management system controls HVAC equipment. Methodology includes on-site measurements, data logging on management system and evaluating the occupants’ perception of a summer and a winter period indoor environment using a standardized questionnaire. In conclusion, thermal comfort in this historic building is poor although it is equipped with modern ventilation systems and there should be possibilities for improving comfort, by improved control strategies.

    Keywords — Historic Buildings, On-site Measurements, Standardized Questionnaire, Thermal Comfort

  • 133.
    Kifleyesus, Biniam Okbaendrias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Eneregy Management In Industries: Analysis of Energy Saving potential by Steam conedensate recovery2017Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    When speaking about energy it means speaking about life, activity, economy, growth and environmental issues. The issue of energy has been the main article all over the world in recent years, this is due to the importance of energy to life and its impact on the environment. For example, Paris climate change meeting in 2015 is one of the recent global meeting which directly related to the energy use by nations. The meeting was mainly focused up on the restriction of greenhouse gas emission which implies that industries should think about other alternative energy resources rather than fossil fuel for positive impact on climatic change. This is one of the cases that led industries into greater competition in the global market. Industries must consider energy alternatives which is safe for the environment and by using such energy a competitive product with better quality and quantity should be produced. This challenge has motivated industries to look and study the energy that they are using currently.

    Studies and researches show that one of the main and most abundant energy resources that most of these industries can get is by improving the energy efficiency or managing the energy that they currently use. The main aim of this thesis is to provide Arizona chemical plant (Kraton) at Sandarne on the potential energy saving by managing their energy use. The first wisdom in energy utilization is managing and using the energy they possess efficiently. In Arizona plant at Sandarne, the product named “Pitch” (a natural viscoelastic polymer or rosin) is a fuel used as the primary energy supply for the production of steam by boilers. The steam may be utilized well but the energy in the condensate (after steam loses its latent heat) is not addressed well enough. Hence this paper has studied on how significant is the energy lost by the steam condensate is and how its recovery can be used to save energy and cost.

    The plant produces about an average of 11.42 ton of steam each hour in a year. This steam can be returned or fully recovered (100%) as condensate from the law of conservation of mass since only energy is lost from the steam. But the plant returns a maximum of about 3ton of condensate each hour. This amount is relatively low compared to the amount of condensate recovery possibility. Recovery possibility of condensate return showed that the plant at Sandarne can return at least 8.5 ton of condensate  each hour. In comparison with the current return estimated 5.5 ton of condensate is being lost simply as waste each hour leading to about 400 SEK minimum cost loss. The calculation of cost is in minimum because the charge from water supply and condensate effluent disposal charge are not considered. In this paper only recovery from the easily recoverable steam condensate is being considered (25% of the system) which resulted in payback time of the proposed investment 1.88 years without considering the above explained charges.

    It is much motivating study considering the generalized approach and over simplified method. If a deeper investigation is made on the potential, it can be clearly shown that how significant the potential is in securing and sustaining energy and environmental issues. Ensuring the security and sustainability of energy which addresses the environmental issue precisely will help the plant to stay on the race of global market competition.

     

    Keywords: Energy efficiency, Boiler efficiency, Energy management, Condensate recovery,

  • 134.
    Kobayashi, Tomohiro
    et al.
    Department of Architecture, School of Engineering, Osaka City University, Japan.
    Sugita, Kazuki
    Department of Architecture, School of Engineering, Osaka City University, Japan.
    Umemiya, Noriko
    Department of Architecture, School of Engineering, Osaka City University, Japan.
    Kishimoto, Takashi
    Kyoto Institute, Kinden Corporation, Japan.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Numerical investigation and accuracy verification of indoor environment for an impinging jet ventilated room using computational fluid dynamics2017In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 115, p. 251-268Article in journal (Refereed)
    Abstract [en]

    The impinging jet ventilation (IJV) system has been proposed as an air distribution strategy to provide a better thermal environment with a medium supply momentum than displacement ventilation (DV) system. However, no simplified prediction method that is practically applicable has been established to date. The ultimate goal of this study is to establish a calculation model to predict the vertical temperature profile in an IJV system. The authors aim to propose a one-dimensional model, where the room is divided into several control volumes. To perform this, the turbulent thermal diffusion between control volumes needs to be well understood. Therefore, a knowledge about the effect of each design factor such as the supply air velocity on the turbulent thermal diffusivity needs to be acquired through a parametric study. Computational Fluid Dynamics (CFD) is effective for this purpose. As a first step, the accuracy of CFD simulations is verified by conducting a full-scale experiment. The velocity profiles inside the impinging jet and the indoor temperatures are measured and compared with the CFD results. It is shown that the shear-stress transport k-ω model has a sufficient accuracy to analyse the target room, and an appropriate grid layout is established as well. The convection-radiation coupling CFD prediction where the external temperature is used as a boundary condition is adopted as the best method for the numerical study in this research. Finally, a parametric study on the supply air velocity is performed based on this setting and its effect on the thermal stratification is presented. 

  • 135.
    KUBWIMANA, Valens
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Evaluating sustainability of electricity access in Rwanda (2009 to 2013)2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Sustainable energy supplies have been a key to economic development and the transition from agricultural economies to modern industrial and service-oriented societies. Energy as essential to improved social and economic welfare is a key for reducing poverty and raising living standards. However, still 1.2 billion people have no access to electricity [1] and providing sustainable energy access to these people is a real challenge. How Rwanda is performing in terms of providing sustainable electricity to its rural people? This thesis evaluates the relative performance of Rwanda from 2009 to 2013 in providing sustainable electricity access. The evaluation of sustainability of electricity access situation was undertaken using Principal Components Analysis technique (PCA) whereby a theoretical framework defining sustainability of electricity was constructed and a set of indicators has been selected basing on analytical soundness, measurability and ability to describe electricity sustainability phenomenon and also basing on the availability of data to define and determine the sustainability. The study shows that the sustainability for electricity access in Rwanda has been improved for the evaluated period of time (2009-2013). The results conclude that the sustainability of electricity access situation has gone up and this is due to the introduction of many programs that have been instigated and Government commitment to improve the electrification rate. Some strategies, commitments and laws such as electricity law, National energy policy and national energy strategic plan; economic development and Poverty Reduction Strategy as well as Renewable Energy Feed In –Tariffs and electricity access roll-out program that were executed in these period seems to be instrumental in achieving better performance in terms of electricity sustainability.

  • 136.
    La Fleur, Lina
    et al.
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Rohdin, Patrik
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Energy performance of a renovated multi-family building in Sweden2017In: Mediterranean Green Buildings and Renewable Energy: Selected Papers from the World Renewable Energy Network's Med Green Forum / [ed] Sayigh, Ali, Springer, 2017, 1, p. 531-539Chapter in book (Other academic)
    Abstract [en]

    Increased attention is being directed towards reducing energy use in buildings, and implementing energy-saving measures when renovating buildings has become of central importance. The aim of this chapter is to study the effects on heat demand of a deep renovation of a Swedish post-war, multi-family building. The studied building was renovated in 2014, and the renovation measures included thermal improvement of the climate envelope and installation of a mechanical supply and exhaust air ventilation system with heat recovery. The effect on heat demand is studied through a whole-building energy simulation, using IDA Indoor Climate and Energy. The IDA model is empirically validated with regard to its ability to predict indoor temperature and energy use. The results indicate a technical potential for a 50.3% reduction of heat demand from implemented renovation measures, but measured data indicate that actual energy use is around 15% higher than the technical potential. The reasons for this gap could be overestimated heat recovery efficiency or airing.

  • 137.
    La Fleur, Lina
    et al.
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Rohdin, Patrik
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Measured and predicted energy use and indoor climate before and after a major renovation of an apartment building in Sweden2017In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 146, p. 98-110Article in journal (Refereed)
    Abstract [en]

    This article presents a case study of a renovated Swedish apartment building with a common design built in 1961. The aim is to present numerical predictions, validation and evaluation of energy use and indoor climate for the building before and after renovation. Comprehensive field measurements were carried out before and after the renovation to be used as input data in the building energy simulation tool IDA ICE and for validation of model results. Indoor temperature is predicted with maximum standard deviation of 0.4 °C during winter. Annual heat demand is in good agreement with measurements. The building had an annual climate normalized district heat demand of 99.0 MWh before renovation and 55.4 MWh after, resulting in a 44% reduction. A slight under-prediction of the saving potential is noted, since the indoor air temperature has increased after the renovation. The results also show that assumptions of user behavior have significant impact on the energy-saving potential, and that choice of renovation measures, such as level of insulation, and efficiency of the ventilation heat recovery system need careful consideration. Choice of system boundaries also has a major effect on climate and resource impact from selected renovation measures. 

  • 138.
    La Fleur, Lina
    et al.
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Rohdin, Patrik
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Energy use and perceived indoor environment in a Swedish multifamily building before and after major renovation2018In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 10, no 3, article id 766Article in journal (Refereed)
    Abstract [en]

    Improved energy efficiency in the building sector is a central goal in the European Union and renovation of buildings can significantly improve both energy efficiency and indoor environment. This paper studies the perception of indoor environment, modelled indoor climate and heat demand in a building before and after major renovation. The building was constructed in 1961 and renovated in 2014. Insulation of the façade and attic and new windows reduced average U-value from 0.54 to 0.29 W/m2·K. A supply and exhaust ventilation system with heat recovery replaced the old exhaust ventilation. Heat demand was reduced by 44% and maximum supplied heating power was reduced by 38.5%. An on-site questionnaire indicates that perceived thermal comfort improved after the renovation, and the predicted percentage dissatisfied is reduced from 23% to 14% during the heating season. Overall experience with indoor environment is improved. A sensitivity analysis indicates that there is a compromise between thermal comfort and energy use in relation to window solar heat gain, internal heat generation and indoor temperature set point. Higher heat gains, although reducing energy use, can cause problems with high indoor temperatures, and higher indoor temperature might increase thermal comfort during heating season but significantly increases energy use. © 2018 by the authors.

  • 139.
    Lane, Anna-Lena
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. SP Technical Research Institute of Sweden.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Gustavsson, Thorbjörn
    SP Technical Research Institute of Sweden.
    ByggaE – Method for Quality Assurance of Energy Efficient Buildings2017In: International Journal of Energy Production and Management, ISSN 2056-3272, E-ISSN 2056-3280, Vol. 2, no 2, p. 133-139Article in journal (Refereed)
    Abstract [en]

    Policies for energy efficiency requirements in buildings have become more stringent according to EU2020 goals. Despite policy regulations, requirements for energy efficiency are not met in many new buildings. Some of the reasons for this energy performance gap are related to the building process. The aim with this paper is to describe a purposed method for quality assurance of sustainable buildings according to energy efficiency. The proposed method is called ByggaE, where ‘Bygga’ is the Swedish word for ‘build’ and E is the first letter in ‘energy efficient’. It is a tool intended to lower the energy performance gap related to the building process by guiding the client and providers through the process to fulfill goals. The essence of ByggaE is the formulation of requirements by the client and the working process of identifying, handling and following up critical constructions and key issues. This working process involves all participants in the building project by using appropriate quality guidelines and checklists for documentation, communication and verification. ByggaE is a step forward ensuring that the building fulfills the defined functions and that conscious decisions are taken when goals have to be changed during the building project. The next steps are to ensure the usefulness of the method in practice by more testing and to spread knowledge about the method.

  • 140.
    Larsson, Ulf
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Linköpings universitet, Energisystem.
    On the performance of stratified ventilation2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    People nowadays spend most of their time indoors, for example in their homes, cars, in trains, at work, etc. In Sweden, the energy demand in the built environment is a growing issue. The building sector accounts for 40% of total energy use and 15% of total CO2 emissions, and around one-third of the energy use in the world is related to providing a healthy and good comfort indoors. To achieve acceptable indoor climates new designs for the ventilation systems have been proposed in recent decades, among them stratified ventilation systems.

    Stratified ventilation is a concept that often allows good performance for both indoor air quality and thermal comfort. Stratified ventilation systems are effective in reducing cross contamination, since there is virtually no mixing in the space; the temperature and the pollutant concentration increase linearly from the heat source with the height of the occupied zone. There are many different ventilation supply devices using the stratified principle, such as displacement supply device (DSD), impinging jet supply device (IJSD) and wall confluent jet supply device (WCJSD).

    The main aim of this thesis is to analyze and compare different supply devices based on stratified ventilation, with different setups, related to thermal indoor climate, energy efficiency and ventilation efficiency. The ultimate goal is to contribute to an increased understanding of how ventilation systems with stratified supply devices perform.

    Two scientific methods have mainly been used in this thesis, i.e., experimental and numerical investigations. For numerical experiments the CFD (Computational Fluid Dynamics) code ANSYS and FIDAP have been used. Experimental studies have been performed with thermocouples, Hot-Wire Anemometry (HWA) and Hot-Sphere Anemometry, thermal comfort measurement equipment and tracer gas measurement equipment.

    This thesis mainly focuses on three research questions: Interaction between a supply device based on stratified ventilation and downdraft from windows; Flow behavior, energy performance and air change effectiveness for different supply devices based on stratified ventilation; and Thermal comfort for different supply devices based on stratified ventilation.

    Research question one showed that the arrangement of displacement supply device and window in cold climate has significant effect on the flow pattern below the window. Different supply airflow rates have an effect on both the velocity and the temperature of the downdraft. In this case the velocity decreased by approximately 9.5% and the temperature in the downdraft decreased 0.5°C when the flowrate from the supply device increased from 10 to 15 l/s.

    Research question two showed that airflow patterns between different air supply systems were essentially related to characteristics of air supply devices, such as the type, configuration and position, as well as air supply velocities and momentum. For WCJSD, IJSD and DSD, positions of heat sources (such as occupant, computers, lights and external heat sources) played an important role in formation of the room airflow pattern. One interesting observation is that the temperature in the occupied zone is lower and a more stratified temperature field implies a more efficient heat removal by a stratified air supply device. The results revealed that the lowest temperature in the occupied zone was achieved for DSD, but with IJSD and WCJSD slightly warmer, while the system with a mixing supply device (MSD) showed a much higher temperature. The results confirm that air change effectiveness (ACE) for the DSD, WCJSD and IJSD is close to each other. However, MSD shows lower ACE in all the present papers than IJSD, WCJSD and DSD.

    Research question three showed that ventilation systems with stratified supply devices in almost all of the studied cases showed an acceptable level for predicted percentage dissatisfied (PPD), predicted mean vote (PMV) and percentage dissatisfied due to draft (DR). If comparing ventilation systems, using IJSD, WCJSD or DSD with MSD always showed thermal comfort better or at the same level.

  • 141.
    Larsson, Ulf
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Linköpings universitet, Energisystem.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Linköpings universitet, Energisystem.
    Comparison of the thermal comfort and ventilation effectiveness in an office room with three different ventilation supply devices: a measurement study2018In: Proceedings of14th International Conference of Roomvent & Ventilation, Aalto University , 2018, p. 187-192Conference paper (Refereed)
    Abstract [en]

    People spend a significant part of their time in an indoor environment, whether at home, school or workplace. The aim of this paper is to experimentally study the ventilation effectiveness (mean age of air, MAA) and thermal comfort (PMV and PPD) of three different ventilation supply devices, i.e., mixing supply device (MSD), displacement supply device (DSD) and wall confluent jet supply device (WCJSD) in an office room.

    This paper is based on analysis from full-scale measurements performed in a laboratory at University of Gävle. The size of the room corresponds to a typical office module for one person. The test room has dimensions of 4.2 x 3.0 x 2.4 m with a volume of 31.24 m3, with the size of the room corresponding to a typical office. Different heat sources are used to simulate the office environment, which corresponds to 31.75 W/m2.

    The PMV and PPD are comparable to MSD, WCJSD and DSD as it turns out that MSD has poorer comfort than DSD and WCJSD. DSD and WCJSD have more or less the same thermal comfort performance. When comparing the local mean age of air (MAA) for the studied supply devices, the air is significantly much younger for the DSD and WCJSD than for MSD.  

  • 142.
    Larsson, Ulf
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Division of Energy Systems, Department of Management and Engineering, Linköping University, Sweden.
    Comparison of ventilation performance of three different air supply devices - A measurement study2015In: Ventilation 2015: Proceedings of the 11th International Conference on Industrial Ventilation / [ed] Li Z., Li X., Zhang X., and Taipale A., International Conference on Industrial Ventilation , 2015, Vol. 1, p. 359-366Conference paper (Refereed)
    Abstract [en]

    People today spend a significant part of their time in an indoor environment, whether it be home, school, vehicle or workplace. This has put greater demands on indoor air, in terms of both air quality and thermal comfort. The main objective of building ventilation is to take care of pollutants and lower their concentration, but it is also used to cool or heat indoor air. However, exchanging air in a room creates indoor air movements, which can have a major influence on the perception of thermal comfort inside the building. The use of ventilation systems also affects energy use and CO2 discharge to the environment. Therefore it is important to optimize the ventilation system with respect to both indoor climate and energy demand. The aim of this paper was to study the behavior of three different ventilation supply systems, i.e., mixing supply device, displacement supply device and confluent jet supply device, in an office room. The measurements for the present paper were carried out in a special test room at the University of Gᅵᅵvle, Sweden. The room is well insulated and specially designed for full-scale experiments. The size of the room corresponds to a normal office, to produce a heat-load corresponding to an occupied office room with a computer and a person-simulator placed in the middle of the room. The lighting system was working inside the office room during all the experiments. Twelve different cases have been studied experimentally with different airflow rates, supply air temperature and supply devices. The results show that the confluent jets ventilation with the device placed at 2.2 m provides the highest value of ventilation efficiency, followed by displacement ventilation, while the lowest ventilation efficiency is found in the mixing ventilation system. The temperature gradient looks like what one can expect for both mixing and displacement, and confluent jet is a combination of these two. The results also show that the confluent jets ventilation system provides lower air temperature in the occupied zone compared to both displacement and mixing ventilation.

  • 143.
    Larsson, Ulf
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Comparison of ventilation performance of three different air supply devices: a measurement study2017In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 16, no 3, p. 244-254Article in journal (Refereed)
    Abstract [en]

    People today spend a significant part of their time in an indoor environment, whether it be home, school, vehicle or workplace. This has put greater demands on indoor environment, in terms of both air quality and thermal comfort. The main objective of building ventilation is to take care of pollutants and lower their concentration, but it is also used to cool or heat indoor air. The aim of this paper was to study the behavior of three different ventilation supply devices, i.e. mixing supply device, displacement supply device and confluent jet supply device, in an office room. Different cases have been studied experimentally with different airflow rates, supply air temperature and supply devices. The results shows that mostly that we can expect, but the results show a very small difference in ventilation efficiency between the different systems and in theory there should be a larger difference. © 2017 Informa UK Limited, trading as Taylor & Francis Group.

  • 144.
    Li, Biao
    et al.
    Harbin Institute of Technology, School of Municipal and Environmental Engineering, China; School of the Built Environment, University of Reading, Reading, United Kingdom.
    Luo, Zhiwen
    School of the Built Environment, University of Reading, Reading, United Kingdom .
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Liu, Jing
    Harbin Institute of Technology, School of Municipal and Environmental Engineering, China; State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, China .
    Revisiting the 'Venturi effect' in passage ventilation between two non-parallel buildings2015In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 94, p. 714-722Article in journal (Refereed)
    Abstract [en]

    A recent study conducted by Blocken et al. (Numerical study on the existence of the Venturi effect in passages between perpendicular buildings. Journal of Engineering Mechanics, 2008, 134: 1021-1028) challenged the popular view of the existence of the 'Venturi effect' in building passages as the wind is exposed to an open boundary. The present research extends the work of Blocken et al. (2008a) into a more general setup with the building orientation varying from 0° to 180° using CFD simulations. Our results reveal that the passage flow is mainly determined by the combination of corner streams. It is also shown that converging passages have a higher wind-blocking effect compared to diverging passages, explained by a lower wind speed and higher drag coefficient. Fluxes on the top plane of the passage volume reverse from outflow to inflow in the cases of α = 135°, 150° and 165°. A simple mathematical expression to explain the relationship between the flux ratio and the geometric parameters has been developed to aid wind design in an urban neighborhood. In addition, a converging passage with α = 15° is recommended for urban wind design in cold and temperate climates since the passage flow changes smoothly and a relatively lower wind speed is expected compared with that where there are no buildings. While for the high-density urban area in (sub)tropical climates such as Hong Kong where there is a desire for more wind, a diverging passage with α = 150° is a better choice to promote ventilation at the pedestrian level. 

  • 145.
    Lidberg, T.
    et al.
    School of Technology and Business Studies, Dalarna University, Falun, Sweden.
    Olofsson, T.
    School of Technology and Business Studies, Dalarna University, Falun, Sweden; Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Trygg, Louise
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Department of Management and Engineering, Linköping University, Linköping, Sweden.
    System impact of energy efficient building refurbishment within a district heated region2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 106, p. 45-53Article in journal (Refereed)
    Abstract [en]

    The energy efficiency of the European building stock needs to be increased in order to fulfill the climate goals of the European Union. To be able to evaluate the impact of energy efficient refurbishment in matters of greenhouse gas emissions, it is necessary to apply a system perspective where not only the building but also the surrounding energy system is taken into consideration. This study examines the impact that energy efficient refurbishment of multi-family buildings has on the district heating and the electricity production. It also investigates the impact on electricity utilization and emissions of greenhouse gases. The results from the simulation of four energy efficiency building refurbishment packages were used to evaluate the impact on the district heating system. The packages were chosen to show the difference between refurbishment actions that increase the use of electricity when lowering the heat demand, and actions that lower the heat demand without increasing the electricity use. The energy system cost optimization modeling tool MODEST (Model for Optimization of Dynamic Energy Systems with Time-Dependent Components and Boundary Conditions) was used. When comparing two refurbishment packages with the same annual district heating use, this study shows that a package including changes in the building envelope decreases the greenhouse gas emissions more than a package including ventilation measures.

  • 146.
    Lidberg, Tina
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Högskolan Dalarna.
    Influences from Building Energy Efficiency Refurbishment on a Regional District Heating System2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Improving energy performance of existing buildings is an important part in decreasing energy use and in turn reduce the greenhouse gas emissions caused by human activity and the primary energy use.

    To be able to evaluate how energy refurbishment influences the greenhouse gas emissions and the primary energy use a wider system perspective is needed that puts the building in its context. This thesis deals with energy refurbishment packages performed on multi-family buildings within district heated areas and how they influence greenhouse gas emissions and primary energy use when the district heating use is altered.

    A simulated building is used to evaluate several energy refurbishment packages. The results are used as input data for models of district heating systems to cost optimize the district heating production. The results from the cost optimization are used to evaluate the impact on greenhouse gas emissions and primary energy use.

    The results show a difference between measures that saves district heating without increasing the use of electricity and measures that increases the use of electricity while district heating is saved. For example, a building refurbishment package including only building envelope improvements saves the same amount of district heating as a package including only mechanical ventilation with heat recovery. Despite this, the emissions of greenhouse gases and the use of primary energy is to a greater extent reduced in the first package because the use of electricity remains unchanged.

    Comparing energy refurbishment packages performed on the same building, but within different district heating systems, show the importance of the design of the district heating system. Depending on the fuel types used and to which extent electricity is co-produced in the district heating system, the results of implementing the energy refurbishment packages vary. The largest reduction of greenhouse gases and primary energy use occurs when a refurbishment package is performed on a building in a district heating system with high share of biofuel and no electricity production.

  • 147.
    Lidberg, Tina
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Högskolan Dalarna, Energiteknik.
    Ramírez Villegas, Ricardo
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental engineering. Högskolan Dalarna, Energiteknik.
    Olofsson, Thomas
    Högskolan Dalarna, Energiteknik.
    Eriksson, Ola
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental engineering.
    An approach to illustrate strategies for improved energy efficiency at the municipal level2014In: Proceedings from the 14th International Symposium on District Heating and Cooling / [ed] Anna Land, Swedish District Heating Association, 2014, p. 50-55Conference paper (Refereed)
    Abstract [en]

    This work focuses on how implementation of wellknown refurbishment strategies, applied on multifamily buildings in a post-war housing complex in Sweden can affect the generation of district heating. Both the energy use and the power load were considered.

    The study was performed in Borlänge municipality, Sweden, where the municipality owns both the energy and the housing companies. The strategies for energy efficiency were simulated with IDA-ICE for the Tjärna Ängar area, a housing complex built between 1969- 1971, with access to documented information about the buildings and energy audit. The results of the building simulation were implemented in a simplified model of the local district heating system.

    The results indicate how different renovation strategies affect the demand of energy and power load within the district heating system and can be used to provide indicators for different scenarios. The larger goal of the research is how to maximize the economic and environmental efficiency of improvement strategies on a municipal level as well as how to find appropriate energy optimization methods that can be proposed by building contractors. The initial study presented here was conducted within the research program Reesbe.

  • 148. Lim, Eunsu
    et al.
    Ito, Kazuhide
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Performance evaluation of contaminant removal and air quality control for local ventilation systems using the ventilation index Net Escape Velocity2014In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 79, p. 78-89Article in journal (Refereed)
    Abstract [en]

    A concept of ventilation efficiency, Net Escape Velocity (NEV), developed by authors presents the net and integrated velocity of contaminant transport by convection and diffusion effect at a point within the room. The NEV is the effective ventilation rate with a velocity scale determining the contaminant concentration at a target point and can be expressed by vector and scalar quantities. It is the most important characteristic of NEV concept. An expanded concept of NEV (NEV*), under an assumption that the inflow flux of a contaminant on the control volume is a contaminant generation, was proposed. We believe that the NEV and NEV* distributions can provide helpful information for ventilation design to control contaminants. The purpose of this study was to demonstrate the advantage and contribution of NEV* to current ventilation design procedure by using numerical analysis. Here, it was evaluated by the NEV* that the contaminant removal performances of local ventilation systems which are a kitchen exhaust hood in a kitchen environment, a push-pull hood in an industrial environment and an adsorptive building material in a test chamber. The distributions of the NEV* as vector quantities under the different flow and diffusion fields were analyzed to investigate contaminant leakage across the hypothetical boundaries of the control target domain of the local ventilation hood and to investigate the contaminant concentration reduction performance of the adsorptive building materials. 

  • 149. Lin, Man
    et al.
    Hang, Jian
    Li, Yuguo
    Luo, Zhiwen
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Quantitative ventilation assessments of idealized urban canopy layers with various urban layouts and the same building packing density2014In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 79, p. 152-167Article in journal (Refereed)
    Abstract [en]

    This paper investigates urban canopy layers (UCLs) ventilation under neutral atmospheric condition with the same building area density (Ap = 0.25) and frontal area density ()V = 0.25) but various urban sizes, building height variations, overall urban forms and wind directions. Turbulent airflows are first predicted by CFD simulations with standard k-e model evaluated by wind tunnel data. Then air change rates per hour (ACH) and canopy purging flow rate (PFR) are numerically analyzed to quantify the rate of air exchange and the net ventilation capacity induced by mean flows and turbulence. With a parallel approaching wind (0 = 0), the velocity ratio first decreases in the adjustment region, followed by the fully-developed region where the flow reaches a balance. Although the flow quantities macroscopically keep constant, however ACH decreases and overall UCL ventilation becomes worse if urban size rises from 390 m to 5 km. Theoretically if urban size is infinite, ACH may reach a minimum value depending on local roof ventilation, and it rises from 1.7 to 7.5 if the standard deviation of building height variations increases (0%-833%). Overall UCL ventilation capacity (PFR) with a square overall urban form (Lx = Ly = 390 m) is better as 0 = 0 than oblique winds (0 = 15, 30, 45), and it exceeds that of a staggered urban form under all wind directions (0 = 0 -45), but is less than that of a rectangular urban form (Lx = 570 m, Ly -= 270 m) under most wind directions (0 = 30 -90). Further investigations are still required to quantify the net ventilation efficiency induced by mean flows and turbulence. 

  • 150.
    Linder, Noah
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Lindahl, Therese
    The Beijer Institute of Ecological Economics, Royal Swedish Academy of Sciences, Stockholm, Sweden; Stockholm Resilience Centre, Stockholm University, Stockholm, Sweden.
    Borgström, Sara
    Sustainable Development, Environmental Science and Engineering, Royal Institute of Technology, Stockholm, Sweden.
    Using Behavioural Insights to Promote Food Waste Recycling in Urban Households-Evidence From a Longitudinal Field Experiment.2018In: Frontiers in Psychology, ISSN 1664-1078, E-ISSN 1664-1078, Vol. 9, no MAR, article id 352Article in journal (Refereed)
    Abstract [en]

    Promoting pro-environmental behaviour amongst urban dwellers is one of today's greatest sustainability challenges. The aim of this study is to test whether an information intervention, designed based on theories from environmental psychology and behavioural economics, can be effective in promoting recycling of food waste in an urban area. To this end we developed and evaluated an information leaflet, mainly guided by insights from nudging and community-based social marketing. The effect of the intervention was estimated through a natural field experiment in Hökarängen, a suburb of Stockholm city, Sweden, and was evaluated using a difference-in-difference analysis. The results indicate a statistically significant increase in food waste recycled compared to a control group in the research area. The data analysed was on the weight of food waste collected from sorting stations in the research area, and the collection period stretched for almost 2 years, allowing us to study the short- and long term effects of the intervention. Although the immediate positive effect of the leaflet seems to have attenuated over time, results show that there was a significant difference between the control and the treatment group, even 8 months after the leaflet was distributed. Insights from this study can be used to guide development of similar pro-environmental behaviour interventions for other urban areas in Sweden and abroad, improving chances of reaching environmental policy goals.

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