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  • 51.
    Larsson, Ulf
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Linköpings universitet, Energisystem.
    Moshfegh, Bahram
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Linköpings universitet, Energisystem.
    Comparison of the thermal comfort and ventilation effectiveness in an office room with three different ventilation supply devices: a measurement study2018Inngår i: Proceedings of14th International Conference of Roomvent & Ventilation, Aalto University , 2018, s. 187-192Konferansepaper (Fagfellevurdert)
    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.  

  • 52.
    Larsson, Ulf
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Moshfegh, Bahram
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Division of Energy Systems, Department of Management and Engineering, Linköping University, Sweden.
    Comparison of ventilation performance of three different air supply devices - A measurement study2015Inngår i: 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, s. 359-366Konferansepaper (Fagfellevurdert)
    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.

  • 53.
    Larsson, Ulf
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Moshfegh, Bahram
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. 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 study2017Inngår i: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 16, nr 3, s. 244-254Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 54.
    Larsson, Ulf
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för energi- och maskinteknik. Division of Energy Systems, Department of Mechanical Engineering, University of Linköping, Linköping, Sweden.
    Moshfegh, Bahram
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för energi- och maskinteknik. Division of Energy Systems, Department of Mechanical Engineering, University of Linköping, Linköping, Sweden.
    Experimental investigation of downdraught from well-insulated windows2002Inngår i: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 37, nr 11, s. 1073-1082Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Since the climate in the Nordic countries is cold for several months a year, windows are crucial in building envelopes. The current trend to reduce heat losses by building components has resulted in many modifications to window design in order to improve thermal performance and the indoor climate. Improvements in window construction have resulted in a higher surface temperature on the inner pane and considerably lower downdraught, which in turn has created an opportunity for the unconventional design of the heating and ventilation systems. The impetus for this paper is to experimentally investigate the effect of thermal performance, window bay and displacement ventilation on the downdraught. The measurements show that the use of well-insulated windows, besides lowering energy consumption, gives rise to a higher quality of indoor climate. The results show a considerably reduced velocity and turbulent intensity by employing a well-insulated window instead of a conventional one. The influence of the window bay on the downdraught is also shown in the paper. © 2002 Elsevier Science Ltd. All rights reserved.

  • 55.
    Larsson, Ulf
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för energi- och maskinteknik.
    Moshfegh, Bahram
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för energi- och maskinteknik.
    Sandberg, Mats
    Högskolan i Gävle, Institutionen för teknik och byggd miljö.
    Thermal analysis of super insulated windows (numerical and experimental investigations)1999Inngår i: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 29, nr 2, s. 121-128Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Windows are crucial for people's experience of the indoor climate, especially in the Nordic countries with cold climate and short days during the winter. This paper reports the first results from an ongoing research project focused on an improved integration of windows with the indoor air climate and people's perception of the windows. The thermal performance of a well-insulated window has been investigated both numerically and experimentally in a full scale test room. The window under consideration is a low-emissive triple-glazing window with two closed spaces filled with the inert gas krypton. An oxidised metal with low emissivity factor coats one pane in each space. Experimental and numerical investigations on the thermal performance of the window have been conducted for different winter cases. Temperature data obtained by direct temperature measurement using thermocouples and through numerical analysis are presented. The heat transfer through a window construction depends on three mechanisms i.e., conduction, convection and radiation. In this paper the convection-conducting mechanisms have been closely investigated. The numerical predictions agree well with the results from the measurements.

  • 56.
    Liu, Linn
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Division of Energy Systems, Department of Management and Engineering, Linköping University.
    Moshfegh, Bahram
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Division of Energy Systems, Department of Management and Engineering, Linköping University.
    Akander, Jan
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Cehlin, Mathias
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Comprehensive investigation on energy retrofits in eleven multi-family buildings in Sweden2014Inngår i: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 84, s. 704-715Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rapidly growing energy use in the building sector is considered a serious problem by both the European Union (EU) and Sweden. Reducing energy demand in the building sector is important for Sweden in order to reach national energy goals for reduced energy use and CO 2 emissions in the future. This project aims to find energy efficiency potential in multifamily buildings in the Gävleborg region, which is a cold climate region in Sweden. Measurements and simulations have been made on eleven multifamily buildings from the whole region. The results include different energy efficiency measure packages, profitability analysis of individual measures and packages, and primary energy use analysis. The paper also includes CO 2 emissions reduction analysis based on different methods. The project shows that the multifamily buildings in the Gävleborg region have good potential to reduce their energy use by more than 50%, which in turn will contribute to 43% primary energy reduction and 48% CO 2 emissions reduction. 

  • 57.
    Liu, Linn
    et al.
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Sweden.
    Rohdin, Parrik
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Sweden.
    Moshfegh, Bahram
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Division of Energy Systems, Department of Management and Engineering, Linköping University, Sweden.
    Investigating cost-optimal refurbishment strategies for the medieval district of Visby in Sweden2018Inngår i: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 158, s. 750-760Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a methodology, using Life Cycle Cost (LCC) optimization and building categorization, to achieve a systematic study of the cost-optimal energy efficiency potential (CEEP) for 920 listed buildings in the medieval district of Visby in Sweden. The aim is to study the CEEP and CO2 emission reductions for this city that is included in the World Heritage List by UNESCO. The total CEEP is found to be 31% (20.6 GWh) resulting in a CO2 reduction of 57% (33.3 kton). The categorization method showed that the buildings could be divided in four clusters depending on building material, geometry and layout. The LCC analysis revealed that the energy efficiency measure packages were cluster specific. It is shown that multi-story wood buildings (Cluster II) have lowest specific LCC, and would arguably be the starting point for a renovation process. Presently most of the studied buildings are connected to the district heating (DH). The results show that heat pump (HP) and wood boiler (WB) is cost-optimal heating system for multi-story stone and wood buildings, respectively. In order for the DH to compete with HP and WB, the DH price needs to be reduced by 23% and 16%.

  • 58.
    Liu, Linn
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. 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
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Evaluating indoor environment of a retrofitted multi-family building with improved energy performance in Sweden2015Inngår i: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 102, s. 32-44Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The building sector within both the EU and Sweden accounts for about 40% of total energy use. It is therefore important to introduce energy efficiency measures in this sector in order to meet the national implementation of the Building Performance Directive. Retrofits that result in improved energy performance are important in order to meet national energy targets, but the impact on the indoor environment has to be considered. Properly chosen energy efficiency measures may affect the indoor environment positively. One retrofitted multi-family building, located in the city of Linköping, Sweden, was chosen as the study object. The building represents a common type of construction in Sweden. This study presents an evaluation of both the indoor environment and energy use of the retrofitted building in comparison with a similar non-retrofitted building from the same area. The results show that the building has potential to reach a 39% reduction of space heating demand. The indoor environment has been improved compared to the non-retrofitted building. Adding external blinds from 15 May to 15 September between 10am-12pm on the east side and 12pm-3pm on the west side seems to be the best option for improving the indoor climate during summer. 

  • 59.
    Liu, Linn
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Division of Energy Systems, Department of Management and Engineering, Linköping University, Sweden.
    Rohdin, Patrik
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Sweden.
    Moshfegh, Bahram
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Division of Energy Systems, Department of Management and Engineering, Linköping University, Sweden.
    LCC assessments and environmental impacts on the energy renovation of a multi-family building from the 1890s2016Inngår i: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 133, s. 823-833Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The 2020 and 2050 energy targets increase requirements on energy performance in the building stock, thus affecting both listed and non-listed buildings. It is important to select appropriate and cost-optimal energy efficiency measures, using e.g. Life Cycle Cost (LCC) optimization. The aim of this paper is to find cost-optimal packages of energy efficiency measures (EEMs) as well as to explore the effects of specific predesigned energy target values for a listed Swedish multi-family building from the 1890s. The purpose is also to show the effects on energy use, LCC, primary energy use and CO2 emissions of different energy targets, discount rates, electricity prices and geographic locations. The results show that separate energy targets could be an effective way to simplify the implementation for listed buildings. Furthermore, a cost-optimal package of EEMs is more sensitive to changes in discount rate than in electricity price. The energy renovation has impact on the primary energy use and CO2 emissions. The lower the discount rate is, the more EEMs will be implemented and the easier the national energy targets may be achieved. A higher electricity price also leads to more EEMs being implemented but at the same time higher running costs. 

  • 60.
    Lundström, Hans
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för inomhusmiljö.
    Sandberg, Mats
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för inomhusmiljö.
    Moshfegh, Bahram
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för energi- och maskinteknik.
    Temperature dependence of convective heat transfer from fine wires in air: a comprehensive experimental investigation with application to temperature compensation in hot-wire anemometry2007Inngår i: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 32, nr 2, s. 649-657Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Heat transfer from a fine wire to air has been experimentally investigated. High accuracy measurements, where both the air temperature and wire temperature have been varied systematically and independently have made it possible to map the behavior of the heat transfer process for different velocities, air temperatures, and wire temperatures. Based on these results a compensation method is proposed which makes it possible to temperature compensate hot wires of large aspect ratio and at low Reynolds numbers for anemometry measurements with velocity calibration only at one air temperature.

  • 61.
    Milić, Vlatko
    et al.
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Ekelöw, Klas
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Moshfegh, Bahram
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    On the performance of LCC optimization software OPERA-MILP by comparison with building energy simulation software IDA ICE2018Inngår i: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 128, s. 305-319Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    From an economic point of view, it is crucial to minimize the life cycle costs (LCC) of buildings undergoing energy renovations, hence an optimization approach is needed. Building energy use and power demand as well as energy efficiency measures are important issues while performing an LCC optimization. Thus it is of great importance to accurately predict the building energy use and power demand before and after energy renovation. This paper aims to address the performance of an in-house LCC optimization software, OPERA-MILP, which has a rather fast optimization procedure. The aim is fulfilled through comparison with building energy simulation software IDA ICE before and after cost-optimal energy renovation. Three historic buildings with different layout and construction properties are used as a case study. The results show good agreement in the calculations of buildings’ power demand and energy use between OPERA-MILP and IDA ICE. The percentage difference in calculated annual energy use and buildings’ power demand with OPERA-MILP compared to IDA ICE is shown to be maximum 11% and 8% for the studied climate zones, respectively. Total impact on LCC is estimated to be equal to or less than 8%.

  • 62.
    Rundstrom, Daniel
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för energi- och maskinteknik.
    Moshfegh, Bahram
    Department of Mechanical Engineering, Linköping University, Linköping, Sweden.
    Investigation of Heat Transfer and Pressure Drop of an Impinging Jet in a Cross-Flow for Cooling of a Heated Cube2008Inngår i: Journal of heat transfer, ISSN 0022-1481, E-ISSN 1528-8943, Vol. 130, nr 12, artikkel-id 121401Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this study is to investigate the thermal performance and the cost measured in pressure drops of a targeted cooling system with use of an impinging jet in combination with a low-velocity channel flow on a heated wall-mounted cube. The effects of the Reynolds numbers of the impinging jet and the cross flow, as well as the distance between the top and bottom plates, are investigated. A steady-state 3D computational fluid dynamics model was developed with use of a Reynolds stress model as turbulence model. The geometrical case is a channel with a heated cube in the middle of the base plate and two inlets, one horizontal channel flow and one vertical impinging jet. The numerical model was validated against experimental data with a similar geometrical setup. The velocity field was measured by particle image velocimetry and the surface temperature was measured by an infrared imaging system. This case results in a very complex flow structure where several flow-related phenomena influence the heat transfer rate and the pressure drops. The average heat transfer coefficients on each side of the cube and the pressure loss coefficients are presented; correlations for the average heat transfer coefficient on the cube and the pressure loss coefficients are created. [DOI: 10.1115/1.2969266]

  • 63.
    Rundström, Daniel
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för energi- och maskinteknik.
    Moshfegh, Bahram
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för energi- och maskinteknik.
    Investigation of flow and heat transfer of an impinging jet in a cross-flow for cooling of a heated cube2006Inngår i: Journal of Electronic Packaging, ISSN 1043-7398, E-ISSN 1528-9044, Vol. 128, nr 2, s. 150-156Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The current trends toward the greater functionality of electronic devices are resulting in a steady increase in the amount of heat dissipated from electronic components. Forced channel flow is frequently used to remove heat at the walls of the channel where a PCB with a few high heat dissipating components is located. The overall cooling strategy thus must not only match the overall power dissipation load, but also address the requirements of the "hot" components. In order to cool the thermal load with forced channel flow, excessive flow rates will be required. The objective of this study is to investigate if targeted cooling systems, i.e., an impinging jet in combination with a low velocity channel flow, can improve the thermal performance of the system. The steady-state three-dimensional (3-D) model is developed with the Reynolds-Stress-Model (RSM) as a turbulence model. The geometrical case is a channel with a heated cube in the middle of the base plate and two inlets, one horizontal channel flow, and one vertical impinging jet. The numerical model is validated against experimental data obtained from three well-known cases, two cases with an impinging jet on a flat heated plate, and one case with a heated cube in a single channel flow. The effects of the jet Re and jet to-cross-flow velocity ratio are investigated. The airflow pattern around the cube and the surface temperature of the cube as well as the mean values and local distributions of the heat transfer coefficient are presented.

  • 64.
    Rundström, Daniel
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för energi- och maskinteknik. Department of Management and Engineering, Linköping Institute of Technology, Sweden.
    Moshfegh, Bahram
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för energi- och maskinteknik. Department of Management and Engineering, Linköping Institute of Technology, Sweden.
    Large-eddy simulation of an impinging jet in a cross-flow on a heated wall-mounted cube2009Inngår i: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 52, nr 3-4, s. 921-931Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A large-eddy simulation (LES) is performed in order to predict the mean velocity field, the turbulence characteristics and the heat transfer rate of an impinging jet in cross-flow configuration on a heated wall-mounted cube. The WALE model was used to model the subgrid-scale tensor. The results from the LES are compared with a Reynolds stress model (RSM) and against earlier measurements with identical set-up. A comparison between the results from the predictions and the measurements shows that in general the LES has better agreement with the measurements compared to the RSM and particularly in the stagnation region of the impinging jet. (C) 2008 Elsevier Ltd. All rights reserved.

  • 65.
    Rundström, Daniel
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för energi- och maskinteknik. Department of Mechanical Engineering, Linköping University, Linköping, Sweden.
    Moshfegh, Bahram
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för energi- och maskinteknik. Department of Mechanical Engineering, Linköping University, Linköping, Sweden.
    RSM and v̄2-f study on the flow behaviour of an impinging jet in a cross-flow on a wall-mounted cube2007Inngår i: Progress in Computational Fluid Dynamics, An International Journal, ISSN 1468-4349, E-ISSN 1741-5233, Vol. 7, nr 6, s. 311-322Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The current trends of electronic devices are resulting in a steady increase in the dissipated heat from the components. One possible cooling method is to use an impinging jet and a low-velocity channel flow. The objective is to investigate the performance of the v(2) - f model and RSM in order to predict the time-average velocity and the Reynolds stresses. The case is a channel with a cube in the middle of the base plate and two inlets, one horizontal channel flow and one vertical impinging jet above the cube. The turbulence models are validated against earlier PIV measurement with identical set-up.

  • 66.
    Steen Englund, Jessika
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Akander, Jan
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Björling, Mikael
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Miljöteknik.
    Moshfegh, Bahram
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Division of Energy Systems, Department of Management and Engineering, Linköping Unviersty, Linköping, Sweden.
    Assessment of Airflows in a School Building with Mechanical Ventilation Using Passive Tracer Gas Method2017Inngår i: Mediterranean Green Buildings & Renewable Energy: Selected Papers from the World Renewable Energy Network’s Med Green Forum / [ed] Sayigh, Ali, Springer, 2017, 1, s. 619-631Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    The focus of this study is to assess the airflows in a school building built in 1963 in Gävle, Sweden, which is subject to energy conservation measures (ECMs) in a forthcoming renovation. Today, the school building is mainly ventilated by several mechanical ventilation systems, which are controlled by a constant air volume (CAV) strategy. Schedules and presence sensors impose a high operation mode during the day and a low operation mode at night, on weekends and on holidays. The homogeneous tracer gas emission method with passive sampling is used to measure the average local mean age of air (τ) during different operation modes. Temperature, relative humidity and CO2 concentration are simultaneously measured. The calculated relative uncertainty for the average local mean age of air in every measured point is approx. ±20 %. The results during low operation mode show an average value of τ of approx. 8.51 h [corresponding to 0.12 air changes per hour (ACH)], where τ in various zones ranges between 2.55 and 16.37 h (indicating 0.06–0.39 ACH), which is related to the unintentional airflow in the school. The results during mixed operation mode show an average value of τ of approx. 4.60 h (0.22 ACH), where τ in various zones ranges between 2.00 and 8.98 h (0.11–0.50 ACH), which is related to both unintentional and intentional airflows in the school. Corridors, basement and attic rooms and entrances have lower τ compared to classrooms, offices and other rooms. High maximums of the CO2 concentration in some rooms indicate an imbalance in the mechanical ventilation systems. During a regular school week of mixed operation, which includes both high and low operation modes, it is found that mainly the low operation modes show up in the results. The dynamics of the highly varying airflows in the building cannot be identified using the passive sampling technique.

  • 67.
    Weinberger, Gottfried
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Amiri, Shahnaz
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Department of Management and Engineering, Division of Energy Systems, Linköping University, Linköping, Sweden.
    Moshfegh, Bahram
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Department of Management and Engineering, Division of Energy Systems, Linköping University, Linköping, Sweden.
    On the benefit of integration of a district heating system with industrial excess heat: an economic and environmental analysis2017Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 191, s. 454-468Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Energy-related cooperation using industrial excess heat (IEH) in district heating (DH) networks shows economic and environmental benefits. A rarely investigated approach is the energy cooperation which incorporates a jointly operated CHP plant also producing process steam for nearby industry. The present study aims to evaluate economic and environmental effects on the Hofors DH system with jointly operated CHP plant when the nearby steel mill extends the supply of recovered IEH. Various IEH supply opportunities with different capacities of hot water and steam were designed and compared with existing IEH utilization, plant heat and electricity production and DH system performance. The energy system model MODEST is used for cost-optimization. A parametric study is used to analyze influences of increasing IEH cost and fluctuating electricity prices. The results show advantages for the DH system to utilize IEH for deliveries of DH and process steam and the cogeneration of electricity. Economic and environmental benefits are decreased total system cost (-1.67 MEUR/a), less use of fuels and electricity, and reduced CO2 emissions with a maximal reachable amount of 28,200 ton/a when the use of biofuel is assumed as limited resource and the substituted marginal electricity production is based on coal condensing power plants. The results also show that industrial steam is a preferred heat supply source as long as the steam cost is below the alternative heat production cost, irrespective of the electricity price. While the cost-effective utilization of industrial hot water for DH is more sensitive and affected by a beneficial CHP production based on higher electricity price segments, it is also shown that utilization of continuously supplied industrial hot water is limited during seasons of low DH demand.

  • 68.
    Weinberger, Gottfried
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Moshfegh, Bahram
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Investigating influential techno-economic factors for combined heat and power production using optimization and metamodeling2018Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 232, s. 555-571Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper investigates the interaction of a wide range of electricity and fuel prices and technical factors of combined heat and power production in a district heating system. A linear programming-based optimization model with the objective to minimize system cost was used to study the energy systems in the cities of Gävle and Sandviken in Sweden. The comprehensive outcomes from optimization and parametric studies have been analyzed using a polynomial-based metamodel. System costs include variable costs for the production and revenues for sale of heat and electricity. The metamodel is used as an analytical and explanatory tool to interpret input-output relationships. Municipal district heating systems of Gävle and Sandviken in Sweden are studied as an interconnected regional system with improved and new combined heat and power plants. The results show that effects from electricity and fuel prices are important, but that variations in energy system cost may also be caused by many cross-factor interactions with technical factors. A comparative system performance analysis with defined cases and optimal factor setting shows a substantial increase in the electricity production, here by up to 650 GWh annually. The profitability of investing in a new plant depends highly on the considered investment risk and electricity and fuel market prices. CO2 emission savings by up to 466 kton annually can be accomplished if marginal electricity production from coal-condensing power plants is avoided and biofuel is released at the same time.

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