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Larsson, U. & Moshfegh, B. (2018). Comparison of the thermal comfort and ventilation effectiveness in an office room with three different ventilation supply devices: a measurement study. In: Proceedings of14th International Conference of Roomvent & Ventilation: . Paper presented at Roomvent & Ventilation 2018, Aalto University, Espoo, Finland, June 2-5 2018 (pp. 187-192). Aalto University
Open this publication in new window or tab >>Comparison of the thermal comfort and ventilation effectiveness in an office room with three different ventilation supply devices: a measurement study
2018 (English)In: Proceedings of14th International Conference of Roomvent & Ventilation, Aalto University , 2018, p. 187-192Conference paper, Published 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.  

Place, publisher, year, edition, pages
Aalto University, 2018
Keywords
Mixing ventilation, Displacement ventilation, Wall confluent jet ventilation, Thermal comfort, Ventilation effectiveness
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-27913 (URN)9789525236484 (ISBN)
Conference
Roomvent & Ventilation 2018, Aalto University, Espoo, Finland, June 2-5 2018
Available from: 2018-07-26 Created: 2018-09-17 Last updated: 2018-09-17Bibliographically approved
La Fleur, L., Rohdin, P. & Moshfegh, B. (2018). Energy use and perceived indoor environment in a Swedish multifamily building before and after major renovation. Sustainability, 10(3), Article ID 766.
Open this publication in new window or tab >>Energy use and perceived indoor environment in a Swedish multifamily building before and after major renovation
2018 (English)In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 10, no 3, article id 766Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
MDPI AG, 2018
Keywords
Building energy simulation, Energy use, Indoor environment, Multifamily buildings, Renovation, Thermal comfort, building, climate conditions, energy efficiency, European Union, heating, indoor air, questionnaire survey, sensitivity analysis, simulation, ventilation, Sweden
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-26394 (URN)10.3390/su10030766 (DOI)000428567100193 ()2-s2.0-85043467953 (Scopus ID)
Funder
Swedish Research Council Formas
Available from: 2018-04-03 Created: 2018-04-03 Last updated: 2018-06-04Bibliographically approved
Andersson, H., Cehlin, M. & Moshfegh, B. (2018). Experimental and numerical investigations of a new ventilation supply device based on confluent jets. Building and Environment, 137, 18-33
Open this publication in new window or tab >>Experimental and numerical investigations of a new ventilation supply device based on confluent jets
2018 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 137, p. 18-33Article in journal (Refereed) Published
Abstract [en]

In developed countries, heating, ventilation, air conditioning (HVAC) systems account for more than 10% of national energy use. The primary function of a HVAC system is to create proper indoor environment. A number of ventilation strategies have been developed to minimize HVAC systems’ energy use whilst still maintaining a good indoor environment. Among these strategies are confluent jet ventilation and variable air volume. In this study, an air supply device with a novel nozzle design that uses both of the above-mentioned strategies was investigated both experimentally and numerically at three different airflow rates. The results from the numerical investigation using the SST k - ω turbulence model regarding velocities and flow patterns are validated by experimental data carried out by Laser Doppler Anemometry. The results from both studies show that the flow pattern and velocity in each nozzle is directly dependent on the total airflow rate. However, the flow pattern does not vary between the three different airflow rates. The numerical investigation shows that velocity profiles for each nozzle have the same pattern regardless of the airflow rate, but the magnitude of the velocity profile increases as the airflow increases. Thus, a supply device of this kind could be used for variable air volume and produce confluent jets for the airflow rates investigated.

Keywords
Confluent jets, Laser Doppler anemometry, SST k, Validation study, Ventilation supply device, ω turbulence model
National Category
Energy Engineering
Identifiers
urn:nbn:se:hig:diva-26571 (URN)10.1016/j.buildenv.2018.03.038 (DOI)000433649700003 ()2-s2.0-85044917956 (Scopus ID)
Funder
Knowledge Foundation
Note

Funding: University of Gavle, Repus Ventilation AB and the Knowledge Foundation

Available from: 2018-05-15 Created: 2018-05-15 Last updated: 2018-06-25Bibliographically approved
Liu, L., Rohdin, P. & Moshfegh, B. (2018). Investigating cost-optimal refurbishment strategies for the medieval district of Visby in Sweden. Energy and Buildings, 158, 750-760
Open this publication in new window or tab >>Investigating cost-optimal refurbishment strategies for the medieval district of Visby in Sweden
2018 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 158, p. 750-760Article in journal (Refereed) Published
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%.

Place, publisher, year, edition, pages
Elsevier Ltd, 2018
Keywords
Bottom-up methodology, Cost-optimal energy efficiency potential, Energy efficiency measures package, LCC optimization, Medieval district, Refurbishment, Stone/wood buildings, Buildings, Carbon dioxide, Costs, Emission control, Life cycle, Reduction, Wooden buildings, Bottom up, Efficiency measure, Energy efficiency
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-25593 (URN)10.1016/j.enbuild.2017.10.002 (DOI)000423636600064 ()2-s2.0-85032208314 (Scopus ID)
Funder
Swedish Energy Agency
Available from: 2017-11-24 Created: 2017-11-24 Last updated: 2018-03-15Bibliographically approved
Weinberger, G. & Moshfegh, B. (2018). Investigating influential techno-economic factors for combined heat and power production using optimization and metamodeling. Applied Energy, 232, 555-571
Open this publication in new window or tab >>Investigating influential techno-economic factors for combined heat and power production using optimization and metamodeling
2018 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 232, p. 555-571Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Metamodel; Optimization; Energy system cost; Sensitivity analysis; Cogeneration; District heating
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-28141 (URN)10.1016/j.apenergy.2018.09.206 (DOI)
Available from: 2018-10-10 Created: 2018-10-10 Last updated: 2018-10-11Bibliographically approved
Milić, V., Ekelöw, K. & Moshfegh, B. (2018). On the performance of LCC optimization software OPERA-MILP by comparison with building energy simulation software IDA ICE. Building and Environment, 128, 305-319
Open this publication in new window or tab >>On the performance of LCC optimization software OPERA-MILP by comparison with building energy simulation software IDA ICE
2018 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 128, p. 305-319Article in journal (Refereed) Published
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%.

Place, publisher, year, edition, pages
Elsevier Ltd, 2018
Keywords
Building energy simulation, Energy renovation, Historic buildings, IDA ICE, LCC optimization, OPERA-MILP, Computer software, Electric power utilization, Energy efficiency, Ice, Integer programming, Life cycle, Building energy simulations, Buildings, computer simulation, construction method, historic building, life cycle analysis, numerical model, optimization, performance assessment, software
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-25837 (URN)10.1016/j.buildenv.2017.11.012 (DOI)000423004900027 ()2-s2.0-85037059457 (Scopus ID)
Funder
Swedish Energy Agency, P31669-3
Available from: 2017-12-19 Created: 2017-12-19 Last updated: 2018-03-13Bibliographically approved
Jahedi, M., Berntsson, F., Wren, J. & Moshfegh, B. (2018). Transient inverse heat conduction problem of quenching a hollow cylinder by one row of water jets. International Journal of Heat and Mass Transfer, 117, 748-756
Open this publication in new window or tab >>Transient inverse heat conduction problem of quenching a hollow cylinder by one row of water jets
2018 (English)In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 117, p. 748-756Article in journal (Refereed) Published
Abstract [en]

In this study, a two-dimensional linear transition inverse heat conduction problem (IHCP) was solved using the Generalized Minimal Residual Method (GMRES) in quenching process by water jets. The inverse solution method was validated by set of artificial data and solution sensitivity analysis was done on data noise level, regularization parameter, cell size, etc. An experimental study has been carried out on quenching a rotary hollow cylinder by one row of subcooled water jets. The inverse solution approach enabled prediction of surface temperature and heat flux distribution of test specimen in the quenching experiments by using measured internal specimen temperature. Three different boiling curves were defined in the quenching process of a rotary cylinder. Result obtained by the inverse solution showed clear footprint of rotation in surface temperature and heat flux on each revolution of cylinder and temperature variation damping from quenching surface toward interior of specimen.

Keywords
Inverse heat conduction problem Generalized minimal residual method Water impinging jet Quenching Moving surface
National Category
Energy Engineering Applied Mechanics
Identifiers
urn:nbn:se:hig:diva-25563 (URN)10.1016/j.ijheatmasstransfer.2017.10.048 (DOI)2-s2.0-85032855752 (Scopus ID)
Projects
7644 Ett nytt kylningskoncept – del II
Funder
Swedish Energy Agency
Available from: 2017-11-22 Created: 2017-11-22 Last updated: 2018-03-13Bibliographically approved
Akander, J., Cehlin, M. & Moshfegh, B. (2017). Assessing the Myths on Energy Efficiency When Retrofitting Multifamily Buildings in a Northern Region (1ed.). In: Ali Sayigh (Ed.), Sustainable High Rise Buildings in Urban Zones: Advantages, Challenges, and Global Case Studies (pp. 139-161). Cham: Springer Publishing Company
Open this publication in new window or tab >>Assessing the Myths on Energy Efficiency When Retrofitting Multifamily Buildings in a Northern Region
2017 (English)In: Sustainable High Rise Buildings in Urban Zones: Advantages, Challenges, and Global Case Studies / [ed] Ali Sayigh, Cham: Springer Publishing Company, 2017, 1, p. 139-161Chapter in book (Other academic)
Abstract [en]

In the light of EU’s requirements to achieve a major cut in energy use by 2050, Sweden has the same target. The built environment must by 2020 reduce energy use by 20 and 50 % by 2050. The size of the future building stock will naturally increase and regardless of how energy efficient future buildings will be, the energy performance of the old stock must be improved in order to reach those goals. In major renovation projects involving multifamily buildings in large residential areas in the cities, 50 % reduction can be achieved. This is cost-effective and profitable even if the rent is increased.

Gävleborg is a sparse region in the North, with few cities. Multifamily buildings are generally much smaller than in large cities and owners are reluctant to impose changes that increase rents due to the housing situation in the region. In consequence, the Regional Council and the University of Gävle set out to assess the potential and feasibility of reducing energy use and carbon dioxide emissions in this region’s multifamily buildings. Eleven real buildings were investigated, each having various ownership forms, different technical attributes and heating sources. Energy audits and measurements were conducted to assess the condition of each building. Performances of the buildings and proposed improvements were simulated with building energy simulation programs, whilst life cycle cost analyses were conducted to study viability. Carbon dioxide emission (CO2) reductions were estimated for each improvement.

Based on the results, a concluding discussion is made on whether or not some myths on energy use and retrofitting are true. The following is concluded: It is possible to reach a 50 % reduction, but it is not economical with the costs involved and with today’s energy prices and moderate price increase over time.

Retrofitting or improvements made in the building’s services systems (HVAC) are more economical than actions taken to improve performance of building by constructions. HVAC improvements give about 20 % reduction in energy use. However, mechanical ventilation systems with heat recuperation are not economical, though these may or may not substantially reduce use of thermal energy.

Solar energy is, despite the latitude of the region, economically viable—especially PV solar energy. Photovoltaic panels (PVs) are becoming viable—the combination of PVs and district heating is beneficial since saving electricity is more important than thermal energy in district-heated areas.

Place, publisher, year, edition, pages
Cham: Springer Publishing Company, 2017 Edition: 1
Keywords
Retrofit, Multifamily buildings, Energy savings
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-23209 (URN)10.1007/978-3-319-17756-4_8 (DOI)2-s2.0-85028882688 (Scopus ID)978-3-319-17755-7 (ISBN)978-3-319-17756-4 (ISBN)
Projects
EKG-f
Funder
Swedish Energy Agency
Note

Funders of the EKG project: Swedish Energy Agency, Regional Council of Gävleborg and University of Gävle. 

Available from: 2017-01-02 Created: 2017-01-02 Last updated: 2018-03-13Bibliographically approved
Steen Englund, J., Akander, J., Björling, M. & Moshfegh, B. (2017). Assessment of Airflows in a School Building with Mechanical Ventilation Using Passive Tracer Gas Method (1ed.). In: Sayigh, Ali (Ed.), Mediterranean Green Buildings & Renewable Energy: Selected Papers from the World Renewable Energy Network’s Med Green Forum: (pp. 619-631). Springer
Open this publication in new window or tab >>Assessment of Airflows in a School Building with Mechanical Ventilation Using Passive Tracer Gas Method
2017 (English)In: Mediterranean Green Buildings & Renewable Energy: Selected Papers from the World Renewable Energy Network’s Med Green Forum / [ed] Sayigh, Ali, Springer, 2017, 1, p. 619-631Chapter in book (Refereed)
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.

Place, publisher, year, edition, pages
Springer, 2017 Edition: 1
Keywords
Homogeneous tracer gas emission technique, Local mean age of air, Air change rate, Air leakage, School building
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-24006 (URN)10.1007/978-3-319-30746-6_47 (DOI)2-s2.0-85029047826 (Scopus ID)978-3-319-30745-9 (ISBN)978-3-319-30746-6 (ISBN)
Note

Entire publication doi: 10.1007/978-3-319-30746-6

Available from: 2017-05-12 Created: 2017-05-12 Last updated: 2018-03-13Bibliographically approved
Larsson, U. & Moshfegh, B. (2017). Comparison of ventilation performance of three different air supply devices: a measurement study. The International Journal of Ventilation, 16(3), 244-254
Open this publication in new window or tab >>Comparison of ventilation performance of three different air supply devices: a measurement study
2017 (English)In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 16, no 3, p. 244-254Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Taylor and Francis Ltd., 2017
Keywords
air exchange efficiency, confluent jet ventilation, displacement ventilation, measurement, Mixing ventilation, Air quality, Efficiency, Indoor air pollution, Measurements, Mixing, Ventilation, Air exchange efficiencies, Building ventilations, Jet ventilations, Supply air temperature, Ventilation efficiency, Ventilation performance, Fighter aircraft
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-24325 (URN)10.1080/14733315.2017.1299519 (DOI)000406118900008 ()2-s2.0-85016093683 (Scopus ID)
Available from: 2017-06-16 Created: 2017-06-16 Last updated: 2018-09-17Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3472-4210

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