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  • 1.
    Jin, Ruiqiu
    et al.
    Department of Atmospheric Science, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, China.
    Hang, Jian
    Department of Atmospheric Science, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, China.
    Liu, Shanshan
    Department of Atmospheric Science, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, China.
    Wei, Jianjian
    Department of Mechanical Engineering, The University of Hong Kong, Pokfulam, Hong Kong.
    Liu, Yang
    Department of Atmospheric Science, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, China.
    Xie, Jielan
    Department of Atmospheric Science, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, China.
    Sandberg, Mats
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Numerical investigation of wind-driven natural ventilation performance in a multi-storey hospital by coupling indoor and outdoor airflow2016Ingår i: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 25, nr 8, s. 1226-1247Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 2.
    Joudi, Ali
    et al.
    Energy Technology, Dalarna University, Falun, Sweden; SSAB Europe, Borlänge, Sweden.
    Cehlin, Mathias
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Svedung, Harald
    Energy Technology, Dalarna University, Falun, Sweden; SSAB Europe, Borlänge, Sweden.
    Rönnelid, Mats
    Energy Technology, Dalarna University, Falun, Sweden.
    Moshfegh, Bahram
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Energy Systems, Linköping University, Linköping, Sweden.
    Numerical and experimental investigation of the influence of infrared reflective interior surfaces on building temperature distributions2017Ingår i: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 26, nr 3, s. 355-367Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 3.
    Kabanshi, Alan
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Wigö, Hans
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Ljung, Robert
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Miljöpsykologi.
    Sörqvist, Patrik
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Miljöpsykologi.
    Human perception of room temperature and intermittent air jet cooling in a classroom2017Ingår i: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 26, nr 4, s. 528-537Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 4.
    Kabanshi, Alan
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Energisystem och byggnadsteknik.
    Yang, Bin
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Sörqvist, Patrik
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Miljöpsykologi.
    Sandberg, Mats
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Energisystem och byggnadsteknik.
    Occupants’ perception of air movements and air quality in a simulated classroom with an intermittent air supply system2019Ingår i: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 28, nr 1, s. 63-76Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 5.
    Sandberg, Mats
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Energisystem och byggnadsteknik.
    Kabanshi, Alan
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Energisystem och byggnadsteknik.
    Wigö, Hans
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Energisystem och byggnadsteknik.
    Is building ventilation a process of diluting contaminants or delivering clean air?2019Ingår i: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this paper is to discuss the performance of air distribution systems intended for dilution of contaminants (e.g. mixing ventilation) and those intended for delivery of clean air to local regions within rooms (e.g. personalized ventilation). We first start by distinguishing the systems by their visiting frequency behaviour. Then, the performance of the systems with respect to their possibility to influence contaminant concentration in the room or regions within the room is dealt with. Dilution capacity concept for mixing systems is discussed, and delivery capacity concept for systems intended to deliver clean air locally is introduced. Various ways for supply of clean air to regions within the room are presented and their pros and cons are discussed. In delivery capacity systems, the most important single parameter is the entrainment of ambient air into the primary supply flow. Therefore, methods of determining entrainment in these systems need to be defined and the results should be included when describing the performance of the air terminal devices.

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