hig.sePublications
Change search
Refine search result
12 1 - 50 of 53
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard-cite-them-right
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • sv-SE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • de-DE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Andersson, Harald
    et al.
    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.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Experimental and numerical investigations of a new ventilation supply device based on confluent jets2018In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 137, p. 18-33Article in journal (Refereed)
    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.

  • 2.
    Antoniou, Nestoras
    et al.
    Department of Civil and Environmental Engineering, University of Cyprus, Nicosia, Cyprus; Department of the Built Environment, Eindhoven University of Technology, Eindhoven, The Netherlands.
    Montazeri, Hamid
    Department of the Built Environment, Eindhoven University of Technology, Eindhoven, The Netherlands; Department of Civil Engineering, KU Leuven, Leuven, Belgium.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Neophytou, Marina
    Department of Civil and Environmental Engineering, University of Cyprus, Nicosia, Cyprus.
    Blocken, Bert
    Department of the Built Environment, Eindhoven University of Technology, Eindhoven, The Netherlands; Department of Civil Engineering, KU Leuven, Leuven, Belgium.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    CFD and wind-tunnel analysis of outdoor ventilation in a real compact heterogeneous urban area: evaluation using “air delay”2017In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 126, p. 355-372Article in journal (Refereed)
    Abstract [en]

    Outdoor urban ventilation in a real complex urban area is investigated by introducing a new ventilation indicator – the "air delay". Computational Fluid Dynamics (CFD) simulations are performed using the 3D steady Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) approaches. The up-to-date literature shows the lack of detailed evaluations of the two approaches for real compact urban areas. This study further presents a systematic evaluation of steady RANS and LES for the assessment of the ventilation conditions in a dense district in Nicosia, Cyprus. The ventilation conditions within the urban area are investigated by calculating the distribution of the age of air. To better assess the outdoor ventilation, a new indicator, the "air delay" is introduced as the difference between the local mean age of air at an urban area and that in an empty domain with the same computational settings, allowing the comparison of the results in different parts of the domain, without impact of the boundary conditions. CFD results are validated using wind-tunnel measurements of mean wind speed and turbulence intensity performed for the same urban area. The results show that LES can accurately predict the mean wind speed and turbulence intensity with the average deviations of about 6% and 14%, respectively, from the wind-tunnel measurements while for the steady RANS, these are 8% and 31%, respectively. The steady RANS simulations overestimate the local mean air delay. The deviation between the two approaches is 52% at pedestrian level (2 m).

  • 3.
    Arghand, Taha
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Awbi, Hazim
    School of Construction Management and Engineering, University of Reading, United Kingdom.
    Cehlin, Mathias
    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.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, BMG laboratory.
    An experimental investigation of the flow and comfort parameters for under-floor, confluent jets and mixing ventilation systems in an open-plan office2015In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 92, p. 48-60Article in journal (Refereed)
    Abstract [en]

    There is a new trend to convert the workplaces from individual office rooms to open offices for motivating money saving and better communication. With such a shift the ability of existing ventilation systems in meeting the new requirements is a challenging question for researchers. The available options could have an impact on workers' health in terms of providing acceptable levels of thermalcomfort and indoor air quality. Thus, this experimental investigation focuses on the performances of three different air distribution systems in an open-plan office space. The investigated systems were: mixing ventilation with ceiling-mounted inlets, confluent jets ventilation and underfloor air distribution with straight and curved vanes. Although this represents a small part of our more extensiveexperimental investigation, the results show that all the purposed stratified ventilation systems (CJV and UFAD) were more or less behaving as mixing systems with some tendency for displacement effects. Nevertheless, it is known that the mixing systems have a stable flow pattern but has the disadvantage of mixing contaminated air with the fresh supplied air which may produce lower performance and in worst cases occupants' illness. For the open-plan office we studied here, it will be shown that the new systems are capable of performing better than the conventional mixing systems. As expected, the higher air exchange efficiency in combination with lower local mean age of air for corner-mounted CJV and floor-mounted UFAD grills systems indicates that these systems are suitable for open-plan offices and are to be favored over conventional mixing systems.

  • 4.
    Assefa, Getachew
    et al.
    Department of Industrial Ecology, School of Industrial Engineering and Management, Royal Institute of Technology, Stockholm.
    Glaumann, Mauritz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental engineering. Division of Environmental Strategies Research, Department of Urban Planning and Environment, School of Architecture and the Built Environment, Stockholm.
    Malmqvist, Tove
    Division of Environmental Strategies Research, Department of Urban Planning and Environment, School of Architecture and the Built Environment, Stockholm.
    Eriksson, Ola
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental engineering.
    Quality versus impact: Comparing the environmental efficiency of building properties using the EcoEffect tool2010In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 5, p. 1095-1103Article in journal (Refereed)
    Abstract [en]

    There are tools that are developed for the assessment of the environmental impact of buildings (e.g. ATHENA). Other tools dealing with the indoor and outdoor environmental quality of building properties (referred to as real estates in other literature) are also available (e.g. GBTool). A platform where both the aspects of quality and impact are presented in an integrated fashion are few. The aim of this contribution is to present how the performance of different building properties can be assessed and compared using the concept of environmental efficiency in a Swedish assessment tool called EcoEffect. It presents the quality dimension in the form of users' satisfaction covering indoor and outdoor performance features against the weighted environmental impact covering global and local impacts. The indoor and outdoor values are collected using questionnaires combined with inspection and some measurements. Life cycle methodology is behind the calculation of the weighted external environmental impact. A case study is presented to show the application of EcoEffect using a comparative assessment of Lindas and a Reference property. The results show that Lindas block is better in internal environment quality than the Reference property. It performs slightly worse than the Reference property in the external environmental impact due to emissions and waste from energy and material use. The approach of integrated presentation of quality and impact as in EcoEffect provides with the opportunity of uncovering issues problem shifting and sub-optimisation. This avoids undesirable situations where the indoor quality is improved through measures that result in higher external environmental impact. (C) 2009 Elsevier Ltd. All rights reserved.

  • 5.
    Assefa, Getachew
    et al.
    School of Chemical Sciences and Engineering, Royal Institute of Technology, Industrial Ecology, Stockholm, Sweden.
    Glaumann, Mauritz
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för byggnadskvalitet.
    Malmqvist, Tove
    Department of Infrastructure, Royal Institute of Technology, Built Environment Analysis, Stockholm, Sweden.
    Kindembe, Beatric
    White Arkitekter, Stockholm, Sweden.
    Hult, Marie
    Swedish University of Agricultural Sciences, Landscape Architecture, Uppsala, Sweden.
    Myhr, Ulla
    Swedish University of Agricultural Sciences, Landscape Architecture, Uppsala, Sweden.
    Eriksson, Ola
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för byggnadskvalitet.
    Environmental assessment of building properties - where natural and social sciences meet: the case of EcoEffect2007In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 42, no 3, p. 1458-1464Article in journal (Refereed)
    Abstract [en]

    The EcoEffect method of assessing external and internal impacts of building properties is briefly described. The external impacts of manufacturing and transport of the building materials, the generation of power and heat consumed during the operation phase are assessed using life-cycle methodology. Emissions and waste; natural resource depletion and toxic substances in building materials are accounted for. Here methodologies from natural sciences are employed. The internal impacts involve the assessment of the risk for discomfort and ill-being due to features and properties of both the indoor environment and outdoor environment within the boundary of the building properties. This risk is calculated based on data and information from questionnaires; measurements and inspection where methodologies mainly from social sciences are used. Life-cycle costs covering investment and utilities costs as well as maintenance costs summed up over the lifetime of the building are also calculated.

    The result presentation offers extensive layers of diagrams and data tables ranging from an aggregated diagram of environmental efficiency to quantitative indicators of different aspects and factors. Environmental efficiency provides a relative measure of the internal quality of a building property in relation to its external impact vis-à-vis its performance relative to other building properties.

  • 6.
    Cehlin, Mathias
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy engineering.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy engineering.
    Numerical Modeling of a Complex Diffuser in a Room with Displacement Ventilation2010In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 10, p. 2240-2252Article in journal (Refereed)
    Abstract [en]

    A micro/macro-level approach (MMLA) has been proposed which makes it possible for HVAC engineers to easily study the effect of diffuser characteristics and diffuser placement on thermal comfort and indoor air quality. In this article the MMLA has been used to predict the flow and thermal behavior of the air in the near-zone of a complex low-velocity diffuser. A series of experiment has been carried out to validate the numerical predictions in order to ensure that simulations can be used with confidence to predict indoor airflow. The predictions have been performed by means of steady Reynolds Stress Model (RSM) and the results have good agreement both qualitatively and quantitatively with measurements. However, measurements indicated that the diffusion of the velocity and temperature was to some extent under-predicted by the RSM, which might be related to high instability of the airflow close to the diffuser. This effect might be captured by employing unsteady RSM. The present study also shows the importance of detailed inlet supply modeling in the accuracy of indoor air prediction.

  • 7.
    Chen, Huijuan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Linköpings universitet.
    Janbakhsh, Setareh
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Linköpings universitet.
    Larsson, Ulf
    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. Linköpings universitet.
    Numerical investigation of ventilation performance of different air supply devices in an office environment2015In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 90, p. 37-50Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to compare ventilation performance of four different air supply devices in an office environment with respect to thermal comfort, ventilation efficiency and energy-saving potential, by performing numerical simulations. The devices have the acronyms: Mixing supply device (MSD), Wall confluent jets supply device (WCJSD), Impinging jet supply device (IJSD) and Displacement supply device (DSD). Comparisons were made under identical set-up conditions, as well as at the same occupied zone temperature of about 24.2°C achieved by adding different heat loads and using different air-flow rates. Energy-saving potential was addressed based on the air-flow rate and the related fan power required for obtaining a similar occupied zone temperature for each device. Results showed that the WCJSD and IJSD could provide an acceptable thermal environment while removing excess heat more efficiently than the MSD, as it combined the positive effects of both mixing and stratification principles. This benefit also meant that this devices required less fan power than the MSD for obtaining equivalent occupant zone temperature. The DSD showed a superior performance on heat removal, air exchange efficiency and energy saving to all other devices, but it had difficulties in providing acceptable vertical temperature gradient between the ankle and neck levels for a standing person. 

  • 8.
    Chen, Huijuan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy engineering. Division of Energy Systems, 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 engineering. Division of Energy Systems, Department of Management and Engineering, Linköping University.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy engineering.
    Computational investigation on the factors influencing thermal comfort for impinging jet ventilation2013In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 66, p. 29-41Article in journal (Refereed)
    Abstract [en]

    Impinging jet ventilation (IN) has been proposed to achieve an effective ventilation of an occupied zone in office and industrial buildings. For IJV systems, draught discomfort is the issue of most concern since it supplies cooled air directly to the occupied zone. This study investigated a number of factors influencing draught discomfort and temperature stratification in an office environment equipped with IJV. The factors considered were: shape of air supply device, discharge height, supply airflow rate and supply air temperature. The Response Surface Methodology (RSM) was used to identify the level of the significance of the parameters studied, as well as to develop the predictive models for the local thermal discomfort. Computational fluid dynamics (CFD) was employed to perform a set of required studies, and each simulation condition was determined by the Box-Behnken design (BBD) method. The results indicated that at a low discharge height, the shape of air supply device had a major impact on the flow pattern in the vicinity of the supply device because of the footprint from impinging jet, which consequently affected the draught risk level in the occupied zone. A square-shaped air supply device was found to result in lower overall draught discomfort than rectangular and semi-elliptic shapes. The RSM analysis revealed that the supply airflow rate had a significant impact on the draught discomfort, while the shape of air supply device and discharge height had moderate effects. The temperature stratification in the occupied zone was mostly influenced by the supply air temperature within the range studied.

  • 9.
    Chen, Huijuan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy engineering. Division of Energy Systems, 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 engineering. Division of Energy Systems, Department of Management and Engineering, Linköping University.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy engineering.
    Investigation on the flow and thermal behavior of impinging jet ventilation systems in an office with different heat loads2013In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 59, p. 127-144Article in journal (Refereed)
    Abstract [en]

    This paper presents the flow and temperature field within an office using impinging jet ventilation (IJV) under different heat loads ranging from 17 to 65 W per square meter floor area. The measurement was carried out in a full-scale test room to verify the reliability of three turbulence models, i.e., the RNG k-epsilon, SST k-omega and (nu(2)) over bar - f models. It is found that all the tested models show good agreements with measurements, while the (nu(2)) over bar - f model shows the best performance, especially on the overall temperature prediction. The (nu(2)) over bar - f model is used further to investigate a number of important factors influencing the performance of the IJV. The considered parameters are: cooling effect of chilled ceiling, external heat load as well as its position, number of occupants and supplied air conditions. The interaction effect of chilled ceiling and heat sources results in a complex flow phenomenon but with a notable feature of air circulation. The appearance and strength of the air circulation mainly depends on the external heat load on window and number of occupants. It is found that with higher external heat load on window (384 W and 526 W), the air circulation has a strong tendency towards the side wall in the opposite direction to occupant, while with lower power on window (200 W) the air circulation has a strong tendency in the center of the room and extends to a larger area. When two occupants are present, two swirling zones are formed in the upper region. The effects of air circulation consequently alter the temperature field and the level of local thermal comfort.

  • 10.
    Chen, Huijuan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy engineering.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy engineering.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy engineering.
    Numerical investigation of the flow behavior of an isothermal impinging jet in a room2012In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 49, p. 154-166Article in journal (Refereed)
    Abstract [en]

    The impinging jet concept has been proposed as a new ventilation strategy for use in office and industrial buildings. The present paper reports the mean flow field behavior of an isothermal turbulent impinging jet in a room. The detailed experimental study is carried out to validate the numerical simulations, and the predictions are performed by means of the RNG k-ε and SST k-ω model. The comparisons between the predictive results and the experimental data reveal that both of the tested turbulence models are capable of capturing the main qualitative flow features satisfactorily. It is found that the predictions from the RNG k-ε model predicts slightly better of the maximum velocity decay as jet approaching the floor, while the SST k-ω model accords slightly better in the region close to the impingement zone.

    Another important perspective of this study is to investigate the influence of different flow and configuration parameters such as jet discharge height, diffuser geometry, supply airflow rate and confinement from the surrounding environment on the impinging jet flow field with the validated model. The obtained data are presented in terms of the jet dimensionless velocity distribution, maximum velocity decay and spreading rate along the centerline of the floor. The comparative results demonstrate that all the investigated parameters have certain effects on the studied flow features, and the diffuser geometry is found to have the most appreciable impact, while the supply airflow rate is found to have marginal influence within the moderate flow range. 

  • 11.
    Chen, Lan
    et al.
    School of Atmospheric Sciences, Sun Yat-sen University, Guangzhou, PR China.
    Hang, Jian
    School of Atmospheric Sciences, Sun Yat-sen University, Guangzhou, PR China; Institute of Earth Climate and Environment System, Sun Yat-sen University, Guangzhou, PR China.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, BMG laboratory.
    Di Sabatino, Silvana
    University of Bologna, Bologna, Italy.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    The impacts of building height variations and building packing densities on flow adjustment and city breathability in idealized urban models2017In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 118, p. 344-361Article in journal (Refereed)
    Abstract [en]

    Improving city breathability has been confirmed as one feasible measure to improve pollutant dilution in the urban canopy layer (UCL). Building height variability enhances vertical mixing, but its impacts remain not completely explored. Therefore, both wind tunnel experiments and computational fluid dynamic (CFD) simulations are used to investigate the effect of building height variations (six height standard deviations σH = 0%–77.8%) associated to building packing densities namely λp/λf = 0.25/0.375 (medium-density) and 0.44/0.67 (compact) on city breathability. Two bulk variables (i.e. the in-canopy velocity (UC) and exchange velocity (UE)) are adopted to quantify the horizontal and vertical city breathability respectively, which are normalized by the reference velocity (Uref) in the free flow, typically set at z = 2.5H0 where H0 is the mean building height. Both flow quantities and city breathability experience a flow adjustment process, then reach a balance. The adjustment distance is at least three times longer than four rows documented in previous literature. The medium-density arrays experience much larger UC and UE than the compact ones. UE is found mainly induced by vertical turbulent fluxes, instead of vertical mean flows. In height-variation cases, taller buildings experience larger drag force and city breathability than lower buildings and those in uniform-height cases. For medium-density and compact models with uniform height, the balanced UC/Uref are 0.124 and 0.105 respectively, moreover the balanced UE/Uref are 0.0078 and 0.0065. In contrast, the average UC/Uref in height-variation cases are larger (115.3%–139.5% and 125.7%–141.9% of uniform-height cases) but UE/Uref are smaller (74.4%–79.5% and 61.5%–86.2% of uniform-height cases) for medium-density and compact models. 

  • 12.
    Cho, Y-J
    et al.
    University of Reading.
    Awbi, Hazim
    University of Reading.
    Karimipanah, Taghi
    Fresh AB, Sweden.
    Theoretical and experimental investigation of wall confluent jets ventilation and comparison with wall displacement ventilation2008In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 43, no 6, p. 1091-1100Article in journal (Refereed)
    Abstract [en]

    This paper reports CFD and experimental results of the characteristics of wall confluent jets in a room. The results presented show the behaviour of wall confluent jets in the form of velocity profiles, the spreading rate of jets on the surface, jets decay, etc. The empirical equations derived are compared with other types of air jets. In addition, the flow in wall confluent jets is compared with the flow in displacement ventilation supply, with regards to the vertical and horizontal spreading on the floor. It is concluded that the jet momentum of wall confluent jets can be more conserved than other jets. Thus, wall confluent jets have a greater spread over the floor than displacement flow. (C) 2007 Elsevier Ltd. All rights reserved.

  • 13.
    Chung, Juyeon
    et al.
    Faculty of Engineering Sciences, Kyushu University, Fukuoka, Japan.
    Lim, Eunsu
    Faculty of Science and Engineering, Toyo University, Tokyo, Japan.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Ito, Kazuhide
    Faculty of Engineering Sciences, Kyushu University, Fukuoka, Japan.
    Returning and net escape probabilities of contaminant at a local point in indoor environment2017In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 125, p. 67-76Article in journal (Refereed)
    Abstract [en]

    The quantified recirculation of a contaminant in a local domain is an essential property of the ventilation efficiency in a room. The returning probability of a contaminant (α) generated in a local domain and its net escape probability (NEP) are essential information for understanding the structure of the contaminant concentration distribution in a room and for controlling the indoor air quality. Here, we propose the fundamental definitions of α and NEP and discuss their potential relation with the net escape velocity (NEV) concept. NEP is defined at a local point and/or local domain as the probability that a contaminant is exhausted directly through an exhaust outlet and does not re-circulate to the target local point/domain again. In a computational fluid dynamics (CFD) simulation, the minimum local domain in a room corresponds to the control volume (C.V.) of discretization; hence, NEP in a C.V. is assumed as the probability in a point without volume. In this study, the calculation results of α, NEP, and NEV distributions in a simple two-dimensional model room and a three-dimensional room with push-pull type ventilation system are demonstrated and discussed.

  • 14. Elvsén, Per-Åke
    et al.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Buoyant jet in ventilated rooms: velocity field, temperature field and airflow pattern analysed with three different whole field methods2009In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 44, no 1, p. 137-145Article in journal (Refereed)
  • 15.
    Fredriksson, Jan
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    The effect of false ceiling on the cooling capacity of passive chilled beams2009In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 44, no 7, p. 1426-1430Article in journal (Refereed)
    Abstract [en]

    Passive chilled beams are often used to provide cooling or additional cooling when the ventilation system cannot cope with the whole cooling load. The advantage of passive cooling is that it is a silent cooling. Often the chilled beams are installed above a false ceiling and thereby the room is subdivided into two compartments. From the chilled beam a plume is generated. Make-up air (return air) needs to flow into the upper compartment to substitute the airflow generated by the chilled beam. Therefore openings for this purpose are installed in the false ceiling. Small openings constitute a resistance to the flow and the locations of the openings affect the flow pattern. The overall performance was studied in a mock-up of a real office by changing both the size and position of the openings for the make-up air. A uniform heating source was arranged by covering the floor with a heating foil. The best location and size of the openings were explored by both recording the heat absorbed by the beam and the temperature in the room. Minimum temperature attained in the room is the signature of the most efficient cooling. To achieve efficient cooling with a uniform floor-based heating source, two conditions must be fulfilled: a) the return opening area must be at least equal to the horizontal area of the chilled beam; b) the return air openings must be located at the perimeter of the room. In general we can expect conditions a) and b) to be applicable irrespective of type of heat, but for point sources we could achieve the best cooling by placing the return air opening above the heat source.

  • 16.
    Haapakangas, Annu
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research. Turku University of Applied Sciences, Turku, Finland.
    Hallman, David
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Mathiassen, Svend Erik
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Jahncke, Helena
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Occupational health science. University of Gävle, Centre for Musculoskeletal Research.
    Self-rated productivity and employee well-being in activity-based offices: the role of environmental perceptions and workspace use2018In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 145, p. 115-124Article in journal (Refereed)
    Abstract [en]

    Activity-based offices are increasingly popular. However, productivity and well-being in these work environments have been little researched. The aims of this study were to quantitatively determine perception and use of the activity-based office environment in relation to self-rated productivity and well-being at work, and to identify important predictors of these outcomes. Four activity-based offices in a large Swedish government agency were surveyed 12 months after implementation.Two hundred and thirty-nine respondents were included in the analyses. Linear regression models, adjusted for relevant covariates, were constructed separately for predictors measuring satisfaction with different aspect of the environment (physical environment, privacy, communication, personalization, personal storage, IT functions and cleaning) and office use (the number of daily workspace switches, different workspaces used and the time spent looking for a workspace). Satisfaction with the physical environment, privacy and communication had the strongest positive association with self-rated productivity and well-being at work. Increased workspace switching was associated with higher productivity, while an increase in self-reported time spent searching for a workspace was associated with lower productivity and well-being. However, predictors related to office use generally explained only a small proportion of variance in the two outcomes. The results suggest that office developers should focus particularly on privacy needs but also on communication, personalization, smooth workspace switching and minimization of work time spent looking for available workspaces.

  • 17.
    Hang, J.
    et al.
    University of Hong Kong.
    Li, Y. G.
    University of Hong Kong.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Buccoliere, Riccardo
    Universita di Lecce.
    Di Sibatino, Silvana
    University of Salento.
    The influence of building height variability on pollutant dispersion and pedestrian ventilation in idealized high-rise urban areas2012In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 56, p. 346-360Article in journal (Refereed)
    Abstract [en]

    Studies are still required to understand how rural/marine wind remove ground-level pollutants released uniformly in street networks of high-rise urban areas. The link between building height variability and pollutant removal process still remains unclear. Several idealized urban-like neighbourhoods made of 9-row and 18-row small-scale high-rise square arrays (building width B = street width W, building packing density λp = 0.25) were first numerically studied with a parallel approaching wind and neglecting thermal effects. Normalized pollutant transport rates and pedestrian purging flow rate were applied to quantify the contribution of pollutant removal by mean flow and turbulent diffusion and their net purging capacity.

    Results show that the prediction of isothermal turbulent flows agreed generally well with wind tunnel data. For 9-row arrays with building height variations (standard deviation of 0–57.1%) and the same average canopy height (H0 = 2.33W), pollutant removal mainly depends on mean flows. Larger standard deviations tend to induce better pedestrian ventilation. In comparison to small and large standard deviations, medium values of 14.3–42.9% may experience smaller purging capacity by horizontal mean flows but significantly enhance that by vertical mean flows. For arrays with uniform heights, lowering aspect ratios (H/W = 2.33 and 2.67–1.5) or increasing street lengths (9-row to 18-row) may enhance the contribution of removing pollutants by turbulent diffusions across canopy roofs which may be similarly important as that by mean flows. Although further investigations are still required, this paper clarifies the relationship between building layouts, height variability and removal potential of ground-level pollutants in high-rise urban-like geometries.

  • 18.
    Hang, Jian
    et al.
    University of Hong Kong.
    Li, Yuguo
    University of Hong Kong.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Wind Conditions and Ventilation in high rise long Street Models2010In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 6, p. 1353-1365Article in journal (Refereed)
    Abstract [en]

    We regarded high-rise cities as obstacles and channels to wind. We first studied wind conditions and ventilations in idealized high-rise long street models experimentally and numerically with a constant street width (W = 30 mm), variable street heights (H = 2 W, 2.5W, 3W, 4W), variable street lengths (L = 47.4W, 79W. 333W, 667W) and a parallel approaching wind. The flow rates penetrating into windward entries are a little larger than the reference flow rate in the far upstream free flow through the same area with windward entries in all models. The stream-wise velocity decreases along the street as some air leaves upwardly across street roofs. Near the leeward entry, there is a downward flow which brings some air into the street and results in an accelerating process. In the neighborhood scale long streets (L = 47.4W and 79W), wind in taller streets is stronger and the ventilation is better than a lower one. For the city scale long streets (L = 333W and 667W), a constant flow region exists where the vertical velocity is zero and the stream-wise velocity remains constant. In such regions, turbulent fluctuations across the street roof are more important to air exchange than vertical mean flows. In a taller street, the process to establish the constant flow conditions is longer and the normalized balanced horizontal flow rate is smaller than those in a lower street. In the city scale long streets, the turbulence exchange rate can be 5-10 times greater than the mean flow rate. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.

  • 19.
    Hang, Jian
    et al.
    Department of Mechanical Engineering, The University of Hong Kong, Hong Kong.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Li, Yugo
    Department of Mechanical Engineering, The University of Hong Kong, Hong Kong.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Flow mechanisms and flow capacity in idealized long-street models2010In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 4, p. 1042-1053Article in journal (Refereed)
    Abstract [en]

    It is an open question whether a street network of a city has a certain flow capacity characterizing the flow that can pass through the street network. It s our hypothesis that at least the simple street network has a certain flow capacity. With the purpose of exploring this we studied numerically and experimentally the flow capacity in some idealized long-street models continuously lined with buildings and exposed to a parallel approaching wind. The height of all the models is the same (H = 69 mm). Three groups of models were studied: models with the same uniform street width (W = H) but different lengths (L = 21.7H, 43.5H, 72.5H); models with the same length (L = 43.5H) but different uniform width (W = H, 2H, 4H); and models with a change of width at half distance, L/2. In the last of the three cases, the width of the upstream half was always the same (W1 = H), but there was a wider (W2 = 1.25H, 1.5H, 2H) or narrower (W2 = 0.75H, 0.5H) downstream half. We normalized flow rates by a reference flow rate equal to the flow rate through an opening far upstream with the same area as the windward entry. The normalized flow rate through the windward entry was about 1.0 in all cases. For a sufficiently long-street models, a flow balance is established, creating a fully developed region with a constant horizontal flow (flow capacity) and zero vertical mean velocity. The street length does not affect the flow capacity but as expected the width of the street affects the flow capacity.

  • 20.
    Hang, Jian
    et al.
    epartment of Mechanical Engineering, The University of Hong Kong, Hong Kong.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    LI, Yuguo
    epartment of Mechanical Engineering, The University of Hong Kong, Hong Kong.
    Age of air and air exchange efficiency in idealized city models2009In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 44, no 8, p. 1714-1723Article in journal (Refereed)
    Abstract [en]

    Wind can provide relevantly clean external (rural) air into urban street network, i.e. city ventilation. The local mean age of air denotes the time it takes for the external air to reach a location after entering the urban canopy layer. The air exchange efficiency denotes the efficiency of flushing the street network with external air. However, difficulties exist in calculating the local mean age of air in a city due to open boundaries. The traditional experimental homogeneous emission method is adapted here in a CFD method to predict the urban local age of air and analyze the air exchange efficiency for city ventilation. Three simple city models are considered, including a round city model, a square city model and a long rectangular city with one main street parallel to the approaching wind or with two crossing streets. The difference in the city shape results in significant difference in the local mean age of air. In the round city of one narrow street, two inflows through street openings converge close to the city centre and exits through the street roof, so the air close to the city centre is relatively old and the air exchange efficiency is low (30%). For a round city with two crossing streets, a slightly non-parallel wind to the main street generates younger air and the higher air exchange efficiency in the city.

  • 21.
    Hang, Jian
    et al.
    Department of Atmospheric Sciences, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, China.
    Wang, Qun
    Department of Atmospheric Sciences, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, China .
    Chen, Xieyuan
    Department of Atmospheric Sciences, 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.
    Zhu, Wei
    Department of Atmospheric Sciences, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, China .
    Buccolieri, Riccardo
    Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, University of Salento, Lecce, Italy.
    Di Sabatino, Silvana
    Department of Physics and Astronomy, University of Bologna, Bologna, Italy .
    City breathability in medium density urban-like geometries evaluated through the pollutant transport rate and the net escape velocity2015In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 94, no P1, p. 166-182, article id 4213Article in journal (Refereed)
    Abstract [en]

    This paper investigates pollutant removal at pedestrian level in urban canopy layer (UCL) models of medium packing density (λ<inf>p</inf> = λ<inf>f</inf> = 0.25) using computational fluid dynamics (CFD) simulations. Urban size, building height variations, wind direction and uniform wall heating are investigated. The standard and RNG k-ε turbulence models, validated against wind tunnel data, are used. The contribution of mean flows and turbulent diffusion in removing pollutants at pedestrian level is quantified by three indicators: the net escape velocity (NEV), the pollutant transport rate (PTR) across UCL boundaries and their contribution ratios (CR).Results show that under parallel approaching wind, after a wind-adjustment region, a fully-developed region develops. Longer urban models attain smaller NEV due to pollutant accumulation. Specifically, for street-scale models (~100 m), most pollutants are removed out across leeward street openings and the dilution by horizontal mean flows contributes mostly to NEV. For neighbourhood-scale models (~1 km), both horizontal mean flows and turbulent diffusion contribute more to NEV than vertical mean flows which instead produce significant pollutant re-entry across street roofs. In contrast to uniform height, building height variations increase the contribution of vertical mean flows, but only slightly influence NEV. Finally, flow conditions with parallel wind and uniform wall heating attain larger NEV than oblique wind and isothermal condition.The paper proves that by analysing the values of the three indicators it is possible to form maps of urban breathability according to prevailing wind conditions and known urban morphology that can be of easy use for planning purposes. 

  • 22.
    Hayati, Abolfazl
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Mattsson, Magnus
    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.
    Evaluation of the LBL and AIM-2 air infiltration models on large single zones: three historical churches2014In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 81, p. 365-379Article in journal (Refereed)
    Abstract [en]

    Air infiltration in ancient churches and other historical and monumental buildings is of great importance considering moisture transfer, energy consumption, thermal comfort and air pollutants that induce surface soiling. Two of the most established models for predicting air infiltration rate in buildings are the Lawrence Berkeley Laboratory (LBL) model and the Alberta air Infiltration Model (AIM-2). Being originally developed mainly for dwellings, their applicability to large single zone buildings is evaluated in this study by comparing model predictions with field measurements in three historical stone churches that are naturally ventilated only through infiltration. The somewhat more developed AIM-2 model yielded slightly better predictions than the LBL model. However, an LBL version that allows inclusion of the Neutral Pressure Level (NPL) of the building envelope produced even better predictions and also proved less sensitive to assumptions on air leakage distribution at the building envelopes. All models yielded however significant overpredictions of the air infiltration rate. Since NPL may be difficult to attain in practice, the AIM-2 model was chosen for model modification to improve predictions. Tuning of this model by varying its original coefficients yielded however unrealistic model behaviors and the eventually suggested modification implied introducing a correction factor of 0.8. This reduced the median absolute prediction error from 25% to 11%. Thus, especially when the NPL is not at hand, this modification of the AIM-2 model may suit better for air infiltration assessment of churches and other buildings similar to the tested kind.

  • 23.
    Holmgren, Mattias
    et al.
    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.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Occupant perception of “green” buildings: Distinguishing physical and psychological factors2017In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 114, p. 140-147Article in journal (Refereed)
    Abstract [en]

    Studies have found a preference bias for “environmentally friendly” or “green” artifacts and buildings. For example, indoor environments are more favorably viewed when the building is labeled/certified “green”, in comparison with one that is not labeled/certified, even though the two environments are actually identical. The present study explored how physical properties of the indoor environment (high vs. low temperature) and labeling (“green” vs. “conventional”) interacts in their effect on environment perception. Participants performed a series of tasks in four indoor environments with different labels (low vs. high carbon footprint) and different temperatures (23°C vs. 28°C). Label and temperature were manipulated orthogonally. The participants’ environmental concern was also measured. The environmentally concerned participant assigned higher thermal acceptance and satisfaction scores to the environment labeled “low carbon footprint” (i.e., “green” certified) compared to the environment labeled “high carbon footprint” (i.e., not “green” certified), but only in the cooler thermal environment. Environmentally indifferent participants’ perception of the environment did not differ depending on label or room temperature. The results suggest that a “green” label positively influence the perception of the indoor environment for occupants, but only when the temperature is within the acceptable range as proposed in guidelines for “green” buildings.

  • 24.
    Iqbal, Ahsan
    et al.
    Danish Building Research Institute, Aalborg University, Copenhagen, Denmark .
    Afshari, Aliresa
    Danish Building Research Institute, Aalborg University, Copenhagen, Denmark .
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Heiselberg, Per
    Indoor Environmental Engineering, Aalborg University, Aalborg, Denmark .
    Discharge coefficient of centre-pivot roof windows2015In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 92, p. 635-643Article in journal (Refereed)
    Abstract [en]

    Use of centre-pivot roof windows is very common in single family houses in Nordic Europe. Unfortunately the wind-driven airflow characteristics of this kind of windows are missing in the scientific literature. In the present study, the airflow rate through the window was specified by using the discharge coefficient. Wind tunnel measurements using a modelled centre-pivot roof windowwas used in the present study. For smaller sash opening angles the value of discharge coefficientwas approaching unity and the discharge coefficient decreased with increase in the sash opening angle. The value of 0.6 was only obtained when the window was without sash. Hence, the inclusion of sash improved the airflow characteristics of the window due to increased value of the dischargecoefficient. The discharge coefficient also depended on turbulence in the flow. In the absence of external wind, the turbulence was described by the value of Re. Only for higher values of Re the still-air discharge coefficients became independent of the flow direction and the air velocity. Whereas for wind driven natural ventilation the ratio of average air speed within the opening and the reference wind speed (velocity ratio) was used to define the fully developed turbulent flow. Constant values of wind-driven discharge coefficients were obtained when the average air speed within the opening was equal to or greater than the reference wind speed i.e. the velocity ratio greater than unity. Moreover, when the velocity ratio was greater than unity, the still-air discharge coefficients became identical to the wind-driven discharge coefficients.

  • 25.
    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. 

  • 26.
    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.

  • 27.
    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.

  • 28.
    Karimipanah, Taghi
    Centre for Built Environment, Royal Institute of Technology, Gävle, Sweden .
    Deflection of wall-jets in ventilated enclosures described by pressure distribution1998In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 34, no 3, p. 329-333Article in journal (Refereed)
    Abstract [en]

    The pressure field in fluid systems reflects the flow configuration. Measurements of the pressure along the perimeter of a slot ventilated room have been conducted for different room sizes. The momentum of the jet at the end of the room is decreased with increasing room length. The impingement region (region where the influence of the opposing wall is present) starts, independent of room size, when the distance from the supply device is about 70% of the room length. Corner flows could not be predicted by CFD using the linear eddy viscosity or standard stress models. However, these effects may be captured by using a second moment closure turbulence model with a new near wall approach now available in literature.

  • 29.
    Karimipanah, Taghi
    et al.
    Air Innovation AB, Sweden .
    Awbi, Hazim
    Indoor Environment and Energy Research Group, Department of Construction Management and Engineering, University of Reading, Reading RG6 6AW, United Kingdom .
    Theoretical and experimental investigation of impinging jet ventilation and comparison with wall displacement ventilation2002In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 37, no 12, p. 1329-1342Article in journal (Refereed)
    Abstract [en]

    This paper focuses on evaluating the performance of a new impinging jet ventilation system and compares its performance with a wall displacement ventilation system. Experimental data for an impinging jet in a room are presented and non-dimensional expressions for the decay of maximum velocity over the floor are derived. In addition, the ventilation efficiency, local mean age of air and other characteristic parameters were experimentally and numerically obtained for a mock-up classroom ventilated with the two systems. The internal heat loads from 25 person-simulators and lighting were used in the measurements and simulations to provide a severe test for the two types of ventilation systems. In addition to a large number of experimental data CFD simulations were used to study certain parameters in more detail. The results presented here are part of a larger research programme to develop alternative and efficient systems for room ventilation.

  • 30.
    Karimipanah, Taghi
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö. Fresh AB, Sweden; University of Reading, UK.
    Awbi, Hazim
    University of Reading, United Kingdom .
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Blomqvist, Claes
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Investigation of air quality, comfort parameters and effectiveness for two floor-level air supply systems in classrooms2007In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 42, no 2, p. 647-655Article in journal (Refereed)
    Abstract [en]

    The method of distributing the outdoor air in classrooms has a major impact on indoor air quality and thermal comfort of pupils. In a previous study, ([11] Karimipanah T, Sandberg M, Awbi HB. A comparative study of different air distribution systems in a classroom. In: Proceedings of Roomvent 2000, vol. II, Reading, UK, 2000. p. 1013-18; [13] Karimipanah T, Sandberg M, Awbi HB, Blomqvist C. Effectiveness of confluent jets ventilation system for classrooms. In: Idoor Air 2005, Beijing, China, 2005 (to be presented).) presented results for four and two types of air distribution systems tested in a purpose built classroom with simulated occupancy as well as computational fluid dynamics (CFD) modelling. In this paper, the same experimental setup has been used to investigate the indoor environment in the classroom using confluent jet ventilation, see also ([12] Cho YJ, Awbi HB, Karimipanah T. The characteristics of wall confluent jets for ventilated enclosures. In: Proceedings of Roomvent 2004, Coimbra, Portugal, 2004.) Measurements of air speed, air temperature and tracer gas concentrations have been carried out for different thermal conditions. In addition, 56 cases of CFD simulations have been carried to provide additional information on the indoor air quality and comfort conditions throughout the classroom, such as ventilation effectiveness, air exchange effectiveness, effect of flow rate, effect of radiation, effect of supply temperature, etc., and these are compared with measured data.

  • 31.
    Knez, Igor
    et al.
    University of Gävle, Department of Education and Psychology, Ämnesavdelningen för psykologi.
    Thorsson, Sofia
    hysical Geography, Department of Earth Sciences, Göteborg University, Sweden.
    Thermal, emotional and perceptual evaluations of a park: Cross-cultural and environmental attitude comparisons2008In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 43, no 9, p. 1483-1490Article in journal (Refereed)
    Abstract [en]

    The main objective of the present study was to examine the influence of culture (Sweden vs. Japan) and environmental attitude (urban vs. open-air person) on participants' thermal, emotional and perceptual assessments of a park, within the physiological equivalent temperature (PET) comfortable interval of 18-23 degrees C. It was predicted that persons sharing different cultures and environmental attitudes might psychologically differently evaluate a Swedish and a Japanese park despite similar thermal conditions. Consistent with this prediction, Japanese were shown to evaluate the weather as warmer and less good for out-door activity than did Swedes, although and according to the PET index participants in both cultures experienced similar comfortable thermal conditions. Japanese were also shown to evaluate the park as more pleasant and warmer place than did Swedes. However, the Japanese felt emotionally less pleasant at the site than did Swedes. An interaction between culture and environmental attitude indicated tentatively a difference in environmental attitude (urban vs. open-air person) between the two countries as regards the place-related wind sensitivity. All these findings are discussed in terms of culture and environmental attitude suggesting that thermal, emotional and perceptual assessments of a physical place may be intertwined with psychological and cultural processes, rather than fixed by general thermal indices developed in line with the physiological heat balance models. (C) 2007 Elsevier Ltd. All rights reserved.

  • 32.
    Kobayashi, Tomo
    et al.
    Department of Architectural Engineering, Osaka University, Division of Global Architecture, Osaka, Japan.
    Sagara, Kazunobu
    Department of Architectural Engineering, Osaka University, Division of Global Architecture, Osaka, Japan.
    Yamanaka, Toshio
    Department of Architectural Engineering, Osaka University, Division of Global Architecture, Osaka, Japan.
    Kotani, Hisahi
    Department of Architectural Engineering, Osaka University, Division of Global Architecture, Osaka, Japan.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Power transportation inside stream tube of cross-ventilated simple shaped model and pitched roof house2009In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 44, no 7, p. 1440-1451Article in journal (Refereed)
    Abstract [en]

    The ultimate goal of this work is to establish a prediction method based on Power Balance Model for prediction of flow rate through cross-ventilated building. For the establishment of Power Balance Model, the lost power across stream tube sections must be determined in advance. However, the loss of power in the stream tube was not well studied by other researchers but this concerned critical step forms the focus of the present CFD study in which transported power in stream tubes formed at two selected models: (i) a suspended rectangular model, and (ii) a pitched roof single-storey house model standing on a flat ground surface, was documented. For the development of a new method applying to predict the lost power, decrease of the transported power across the stream tubes through both types of models will finally be shown in this paper.

  • 33.
    Kobayashi, Tomohiro
    et al.
    Ritsumeikan University.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Kotani, Hisashi
    Osaka University.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Experimental investigation and CFD analysis of cross-ventilated flow through single room detached house model2010In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 12, p. 2723-2734Article in journal (Refereed)
    Abstract [en]

    Cross-ventilation is a complicated flow problem and difficult to control because wind exhibits a large degree of variation. The paper focuses on three items: a) to clarify and understand some of the basic characteristics of airflow as the influence of the opening size on the windward vortex and the leeward wake; b) to explore what information about the flow above the ground can be retrieved from pressure measurements on the ground; and c) to explore the accuracy of CFD. To meet these objectives, wind tunnel tests and CFD analyses were carried out. The studied object was a detached-house model provided with two openings. The size of these openings was changed in a wide range from narrow cracks to large openings. In the experiments, pressure measurements on the ground and PIV measurements were made. The internal flow was visualized with the sand erosion method. Pressure measurement on a floor surface is a relatively easy and an inexpensive method. In this experiment, the windward and leeward areas in particular were investigated to understand flow pattern and to confirm correspondence between flow pattern and recorded pressure on the ground. Those measurements show the difference in flow at different size openings in terms of the vortex on the windward side and the wake. When the size of the opening exceeded a certain value the near wake on the leeward side disappeared and on the windward side the vortex disappeared. The pressure distribution, flow pattern, and velocity profile are shown and compared between measurement and CFD.

  • 34.
    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. 

  • 35.
    Kus, Hulya
    et al.
    University of Gävle, Department of Technology and Built Environment.
    Nygren, Kjell
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för byggnadskvalitet.
    Norberg, Peter
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för byggnadskvalitet.
    In-use performance of rendered autoclaved aerated concrete walls by long-term moisture monitoring2004In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 39, no 6, p. 677-687Article in journal (Refereed)
    Abstract [en]

    The importance of long-term performance and durability of building materials and components has received increasing consideration with regard to a sustainable built environment. Degradation due to exposure to environment conditions, particularly driving rain, play a significant role in the service life of porous materials used in external wall components. Microenvironment monitoring data are presented in this paper to show how different surface coatings can contribute to moisture performance of external walls made of autoclaved aerated concrete (AAC). Renderings modifed with hydrophobic products on AAC substrate prove to have less wetting and better drying properties than unmodified renderings according to the performance assessment based on the amount and duration of moisture measured in the material.

  • 36.
    Larsson, Ulf
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för energi- och maskinteknik. Division of Energy Systems, Department of Mechanical Engineering, University of Linköping, Linköping, Sweden.
    Moshfegh, Bahram
    University of Gävle, Department of Technology and Built Environment, 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 windows2002In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 37, no 11, p. 1073-1082Article in journal (Refereed)
    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.

  • 37.
    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. 

  • 38. 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. 

  • 39.
    Lin, Eunsu
    et al.
    Kyushu University Japan.
    Ito, Kazuhide
    Kyushu University japan.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    New Ventilation index for evaluating imperfect mixing conditions: Analysis of Net Escape velocity based on RANS approach2013In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 61, p. 45-56Article in journal (Refereed)
    Abstract [en]

    The concentration of contaminant in a room is not always uniformly distributed and hence it is important to evaluate the ventilation efficiency at various points or domains in the room to optimize and reduce the ventilation rate and the air-conditioning load of the room. Various ventilation indices have been developed to evaluate the ventilation efficiency of a point or a domain based on the contaminant concentration, for example, the age of air, the Scale for Ventilation Efficiency series, Visitation Frequency and Purging Flow Rate.

    This paper presents a new concept of ventilation index, Net Escape Velocity (hereafter NEV), as an index for ventilation efficiency in an indoor environment. NEV represents the effective velocity at which the contaminant is transported/diluted from a target point. The objectives of the present work are to clarify the definition and concept of NEV on the basis of CFD simulation and to investigate the calculation methods of NEV. NEV is defined by contaminant concentration, convective flux and diffusion flux at a point. Using NEV normalized by the convection velocity at a target point, we can obtain information of the turbulent diffusion effect for removal/dilution contaminant and of the direction of diffusion flux which is the same or not with convective flux. It can be said that NEV is an index of ventilation efficiency that can evaluate the ventilation performance at a point and enable understanding of the forming structure of a contaminant concentration at a point.

  • 40. 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. 

  • 41.
    Malmqvist, Tove
    et al.
    oyal Institute of Technology, Department of Urban Studies, Environmental Strategies Research, Stockholm, Sweden.
    Glaumann, Mauritz
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för byggnadskvalitet.
    Environmental efficiency in residential buildings - A simplified communication approach2009In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 44, no 5, p. 937-947Article in journal (Refereed)
    Abstract [en]

    For all actors involved with planning, developing and managing buildings, the environmental impact relating to energy use and the quality of the indoor environment are both aspects of major concern. It is crucial that a reduction in the environmental impact of a building is not achieved through compromising the indoor environment. This paper presents a method to assess user satisfaction related to the indoor environment and the environmental impact related to the energy use of the building, i.e. the environmental efficiency of the building. This environmental efficiency comprises two indices that are calculated separately but displayed in the same diagram to facilitate communication of complex information. This approach forms part of the Swedish life cycle based environmental assessment tool for buildings, EcoEffect. The present paper presents and exemplifies the environmental efficiency of buildings using data from 26 Swedish multi-family residential buildings and proposes a number of reference values. The concept can be used as an overarching objective for environmental management of a property firm's building stock or for evaluating targets set in the planning process for a new building. It can also be used for environmental rating of buildings, which would probably increase the communication value further. The aggregated indices are rough but proportionately straightforward to calculate and easily communicated. In addition, they address the environmental impacts of buildings in a much more comprehensive way than the current practice.

  • 42.
    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
    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.
    On the performance of LCC optimization software OPERA-MILP by comparison with building energy simulation software IDA ICE2018In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 128, p. 305-319Article in journal (Refereed)
    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%.

  • 43.
    Nilsson, Håkan O.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Thermal comfort evaluation with virtual manikin methods2007In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 42, no 12, p. 4000-4005Article in journal (Refereed)
    Abstract [en]

    Computational fluid dynamics has become an important tool in the prediction of thermal comfort in occupied spaces. Despite its ability to predict temperature and velocity fields, it is more difficult to evaluate the degree of thermal comfort experienced by an occupant. This article describes the construction of a new numerical thermal manikin, with new comfort evaluation methods based on data from thermal manikin measurements as well as subjective results from several hundred experiments. The level of thermal comfort is highly dependent on the local environment. Human beings respond differently to local heat transfer in different parts of their bodies. It is suggested for that reason that local results from manikins should be presented in new clothing independent comfort zone diagrams. The research presented in here is intended to be used to evaluate system solutions that provide improved thermal climate in many different everyday situations, e.g. all types of buildings and vehicles.

  • 44.
    Olsson, Stefan
    et al.
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Malmqvist, Tove
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Glaumann, Mauritz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental engineering.
    An approach towards sustainable renovation: a tool for decision support in early project stages2016In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 106, p. 20-32Article in journal (Refereed)
    Abstract [en]

    Reducing greenhouse gas (GHG) emissions through energy reduction in buildings is a high priority for policy-makers in the European Union and elsewhere. However, although long-term sustainability targets exist on the societal level, it is not obvious how these targets may trickle down to individual sectors and further down to specific organizations or buildings. The aim of this paper is to illustrate an approach for evaluating renovation measures in order to identify appropriate target levels in early project stages and what is needed to achieve a number of proposed sustainability targets. The evaluation approach is supported by a tool that can be seen as an aid to making rough estimations of the environmental impacts. Sustainability target levels in a Swedish context are presented for three issues: operational energy use, GHG emissions due to total energy use for building operation, and embodied GHG emissions due to production of materials. The approach to support well-grounded retrofit decisions is shown with a case study. The tool developed, in combination with a suggested step-by-step evaluation approach, provides an effective way to evaluate various potential improvements, and their consequences, in early project stages. However, other tools with similar functionality may be used. Results from the case illustration imply that it is possible to achieve the proposed sustainability targets for operational energy use by implementing nine measures. However, the targets for GHG emissions for operational energy use and embodied GHG emissions were not achieved because of an energy supply with too high a share of non-renewable fuels.

  • 45.
    Ramí­rez-Villegas, Ricardo
    et al.
    Dalarna University, School of Technology and Business Studies, Falun, Sweden.
    Eriksson, Ola
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental engineering.
    Olofsson, Thomas
    Dalarna University, School of Technology and Business Studies, Falun, Sweden; Umeå University, Department of Applied Physics and Electronics, Umeå, Sweden.
    Assessment of renovation measures for a dwelling area - Impacts on energy efficiency and building certification2016In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 97, p. 26-33Article in journal (Refereed)
    Abstract [en]

    The European Union has an ambitious plan to reduce energy use and emissions by the year 2030. The building and real estate sectors have a great potential to help reduce emissions by energy efficiency. However, different energy sources and environmental standards affect the decision making of these major renovations in the existing stock. This study investigates how different renovation strategies affect the energy rating of a selected Building Environmental Assessment Tool and analyses the consequences in terms of greenhouse gas emissions for the local district heating system. Both building energy simulations and energy systems cost optimization were used to determine the energy use and local emissions. The results of different renovation scenarios were used to evaluate the rating in the selected tool and the impact in the district heating local emissions. The used methodology illustrates how energy efficient renovation impacts on the district heating system’s local emissions. However, a bias towards resource classification within the Swedish Building Environmental Tool, Miljöbyggnad, needs to be addressed in order to assess the impact of local emissions.

  • 46.
    Rossi, Barbara
    et al.
    MS2F, ArGEnCo Department, University of Liège, Belgium .
    Marique, Anne-Francoise
    LEMA, ArGEnCo Department, University of Liège, Belgium .
    Glaumann, Mauritz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental engineering.
    Reiter, Sigrid
    LEMA, ArGEnCo Department, University of Liège, Belgium .
    Life-cycle assessment of residential buildings in three different European locations, basic tool2012In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 51, p. 395-401Article in journal (Refereed)
    Abstract [en]

    The paper deals with the development of a tool used for the life cycle assessment of residential buildings located in three different European towns: Brussels (Belgium), Coimbra (Portugal) and Lulea (Sweden). The basic tool focuses on the structure and the materials of the buildings and permits the evaluation of the Embodied energy, Embodied carbon and yearly energy consumption. For that purpose, a different set of original data is taken into account for each location, in which the monthly temperatures, energy mix, heating and cooling systems are defined. The energy consumption, being for heating space or water, for cooling or for lighting is transformed into CO2 emissions to deduce the Operational carbon as well. The influence of the energy mix can therefore be assessed in the basic tool. As a matter of fact, the heating and cooling systems habitually used in the three countries are also of great importance. The District Heating system, is, for instance, incorporated in the basic tool. The presence of solar water heater or photovoltaic panels is also strongly influencing the operational carbon. After a short literature review on building LCA and the description of the basic tool, the software Pleiades + Comfie combined with Equer is used to achieve the complete LCA for one building using two different load bearing frames. The results of the calculations for Brussels climate are verified against these software results. The dependence of the results to parameters such as climate, energy mix and habits is then discussed in the companion paper.

  • 47.
    Sadrizadeh, Sasan
    et al.
    Division of Fluid and Climate Technology, School of Architecture and the Built Environment, KTH Royal Institute of Technology, Stockholm, Sweden; Department of Energy Performance, Indoor Environment and Sustainability of Buildings, Danish Building Research Institute, Aalborg University, Copenhagen, Denmark.
    Afshari, Alireza
    Department of Energy Performance, Indoor Environment and Sustainability of Buildings, Danish Building Research Institute, Aalborg University, Copenhagen, Denmark.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Håkansson, Ulf
    Skanska AB, Stockholm, Sweden.
    Nielsen, Peter
    Department of Civil Engineering, Aalborg University, Aalborg, Denmark.
    Numerical simulation of the impact of surgeon posture on airborne particle distribution in a turbulent mixing operating theatre2016In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 110, p. 140-147Article in journal (Refereed)
    Abstract [en]

    Airborne particles released from surgical team members are major sources of surgical site infections. To reduce the risk of such infections, ultraclean-zoned ventilation systems have been widely applied, as a complement to the ventilation of the main operating theatre. The function of ventilation in an operating theatre is usually determined without considering the influence of the staff members’ posture and movements. The question of whether the surgeon's posture during an on-going operation will influence particle distribution within the surgical area has not yet been explored in depth or well documented. In the present study we analysed data from investigation of two positions (bending and straightened up), which represent the most common surgeon and staff-member postures. The investigation was performed by applying the computational fluid dynamics methodology to solve the governing equations for airflow and airborne particle dispersion. Ultraclean-zoned ventilation systems were examined as an addition to the conventional operating theatre. We examined three distinct source strengths (mean value of pathogens emitted from one person per second) due to the variety of staff clothing systems. In the upright posture, the screen units reduced the mean air counts of bacteria and the mean counts of sedimenting bacteria to a standard level for infection-prone surgeries in the surgical area. However, the performance of this system could be reduced drastically by improper work experience. Surgical garments with a high protective capacity result in lower source strength and thus reduces the particle concentration within the surgical area. These results are useful for developing best practices to prevent or at least reduce the infection rate during a surgical intervention.

  • 48.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Hang, Jian
    Yat-Sen University .
    Luo, Zhiewen
    University of Reading.
    Gong, Jian
    Nanchang Hangkong University.
    Natural ventilation assessment in typical open and semi-open urban environments under various wind directions2013In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 70, p. 318-333Article in journal (Refereed)
  • 49.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Mattsson, Magnus
    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.
    Hayati, Abolfazl
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, BMG laboratory.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, BMG laboratory.
    Khan, Mubashar
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Viewpoints on wind and air infiltration phenomena at buildings illustrated by field and model studies2015In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 92, p. 504-517Article in journal (Refereed)
    Abstract [en]

    Ventilation and infiltration caused by wind are difficult to predict because they are non-local phenomena: driving factors depend on the surrounding terrain and neighbouring buildings and on the building orientation with respect to the wind direction. Wind-driven flow through an opening is complex because wind can flow through the opening or around the building, in contrast to buoyancy driven flow. We explored wind and air infiltration phenomena in terms of pressure distributions on and around buildings, stagnation points, flow along façades, drag forces, and air flow through openings. Field trials were conducted at a 19th-century church, and wind tunnel tests were conducted using a 1:200 scale model of the church and other models with openings.

     

    The locations of stagnation points on the church model were determined using particle image velocimetry measurements. Multiple stagnation points occurred. The forces exerted on the church model by winds in various directions were measured using a load cell. The projected areas affected by winds in various directions were calculated using a CAD model of the church. The area-averaged pressure difference across the church was assessed. A fairly large region of influence on the ground, caused by blockage of the wind, was revealed by testing the scale model in the wind tunnel and recording the static pressure on the ground at many points. The findings of this study are summarized as a number of steps that we suggest to be taken to improve analysis and predictions of wind driven flow in buildings.

  • 50.
    Wallhagen, Marita
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental engineering.
    Glaumann, Mauritz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental engineering.
    Malmqvist, Tove
    Royal Institute of Technology, Division of Environmental Strategies Research, Department of Urban Studies, School of Architecture and the Built Environment, Stockholm.
    Basic building life cycle calculations to decrease contribution to climate change: Case study on an office building in Sweden  2011In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 46, no 10, p. 1863-1871Article in journal (Refereed)
    Abstract [en]

    This study examined whether simplified life cycle-based calculations of climate change contributions can provide better decision support for building design. Contributions to climate change from a newly built office building in Gävle, Sweden, were studied from a life cycle perspective as a basis for improvements. A basic climate and energy calculation tool for buildings developed in the European project ENSLIC was used. The study also examined the relative impacts from building material production and building operation, as well as the relative importance of the impact contributions from these two life cycle stages at various conditions.

    The ENSLIC tool calculates operational energy use and contributions to climate change of a number of optional improvement measures. Twelve relevant improvement measures were tested. The most important measures proved to be changing to CO2 free electricity, changing construction slabs from concrete to wood, using windows with better U-values, insulating the building better and installing low-energy lighting and white goods. Introduction of these measures was estimated to reduce the total contribution to climate change by nearly 50% compared with the original building and the operational energy use by nearly 20% (from 100 to 81 kWh/m2 yr). Almost every building is unique and situated in a specific context. Making simple analyses of different construction options showed to be useful and gave some unexpected results which were difficult to foresee from a general design experience. This process acts as an introduction to life cycle thinking and highlights the consequence of different material choices.

12 1 - 50 of 53
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard-cite-them-right
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • sv-SE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • de-DE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf