The Experts below are selected from a list of 9498 Experts worldwide ranked by ideXlab platform
Christopher Yu Hang Chao - One of the best experts on this subject based on the ideXlab platform.
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numerical and experimental study of velocity and temperature characteristics in a ventilated enclosure with underfloor ventilation systems
Indoor Air, 2005Co-Authors: Man Pun Wan, Christopher Yu Hang ChaoAbstract:UNLABELLED Airflow and temperature distributions in an enclosure with heat sources ventilated by floor Supply Jets with floor or ceiling air exit vents were investigated using experimental and numerical approaches. These ventilation configurations represent the floor return or the top return underfloor ventilation systems found in real applications. Experiments and numerical simulations were performed on a full-sized environmental chamber. The results reveal that the temperature stratification in the enclosure highly depended on the thermal length scale of the floor Supply Jets. When the thermal length scale of the Supply Jet was >>1, temperature stratification was minor for all tested heat densities and air distribution methods. Significant vertical temperature gradients occurred when the Jet thermal length scale was <<1. Changes in air distribution methods also became significant for temperature stratification at small Supply Jet thermal length scales. Temperature stratification also affected the terminal height of the momentum-dominant region of the vertical buoyant Supply Jets. The applicability of these results to underfloor ventilation design was also discussed. PRACTICAL IMPLICATIONS In designing underfloor ventilation systems, Supply Jet conditions and heat load density have to be considered to avoid thermal discomfort because of excessive temperature stratifications. This study demonstrated, by both numerical simulations and experiments, that thermal length scale can be used as a design indicator to predict thermal stratifications under a floor return and a top return underfloor ventilation setting.
Bingfeng Yu - One of the best experts on this subject based on the ideXlab platform.
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Numerical study on temperature stratification in a room with underfloor air distribution system
Energy and Buildings, 2007Co-Authors: Qiongxiang Kong, Bingfeng YuAbstract:Abstract In this study, numerical prediction using computational fluid dynamics (CFD) was utilized to investigate air temperature stratification in a room with an underfloor air distribution (UFAD) system. The numerical modeling using CFD computation was validated with physical test in a full size experimental room with an UFAD system. The different Supply air conditions and heat loads were discussed. The results show that the effect of three parameters, heat load, Supply volume flux and Supply air velocity, on room air temperature would be expressed by the length scale of the floor Supply Jet. When the length scale increased from 0.8 to 1.56 m, the ratio of vertical temperature difference between 2.5 and 0.1 m at the occupied zone to the difference between return and Supply air temperature decreased from 0.62 to 0.25. When there was only one local heat source in the room, there was a thermal stratified interface at the occupied zone. The interface height was about 1.42 times the length scale. The results may suggest ways to optimize UFAD design and operation.
Leon R. Glicksman - One of the best experts on this subject based on the ideXlab platform.
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Determining thermal stratification in rooms with high Supply momentum
Building and Environment, 2017Co-Authors: F.a. Dominguez Espinosa, Leon R. GlicksmanAbstract:Abstract Computational Fluid Dynamics simulations of a typical occupied office were performed to study the effects of ventilation parameters (Supply momentum and heat gain intensity) and inlet geometry (height and area of the Supply) on the temperature profile of the air in the space. A knowledge of this profile is critical to ensure that the occupants are comfortable according to commonly used standards. Different room configurations were characterized in terms of their Archimedes number, which compares the effects of buoyancy and Supply momentum, and dimensionless geometric variables. A high Archimedes space was found to be divided into a warm region of uniform temperature above the occupants and a zone where the temperature increases approximately linearly with height. In a low Archimedes space the air is mixed by the Supply Jet in the lower part of the room, especially near the outlet, resulting in this area having uniform temperature. However, the Supply Jet was found to be less efficient at mixing the air near the ceiling, resulting in higher temperatures in this zone than with higher Archimedes numbers. For a given Archimedes number, as the Supply area increased, the air temperature was found to decrease in the lower part of the room but to increase near the ceiling. A high inlet increased the vertical mixing in the room. Correlations were proposed to establish the temperature profile within 5% of the temperature rise of the room. The inputs of the correlations are readily available in multi-zone software, facilitating their integration in this kind of software. The proposed correlations will allow the user of the multi-zone software to evaluate comfort conditions more accurately, while maintaining the high speed, simplicity and design flexibility of the multi-zone models.
Man Pun Wan - One of the best experts on this subject based on the ideXlab platform.
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numerical and experimental study of velocity and temperature characteristics in a ventilated enclosure with underfloor ventilation systems
Indoor Air, 2005Co-Authors: Man Pun Wan, Christopher Yu Hang ChaoAbstract:UNLABELLED Airflow and temperature distributions in an enclosure with heat sources ventilated by floor Supply Jets with floor or ceiling air exit vents were investigated using experimental and numerical approaches. These ventilation configurations represent the floor return or the top return underfloor ventilation systems found in real applications. Experiments and numerical simulations were performed on a full-sized environmental chamber. The results reveal that the temperature stratification in the enclosure highly depended on the thermal length scale of the floor Supply Jets. When the thermal length scale of the Supply Jet was >>1, temperature stratification was minor for all tested heat densities and air distribution methods. Significant vertical temperature gradients occurred when the Jet thermal length scale was <<1. Changes in air distribution methods also became significant for temperature stratification at small Supply Jet thermal length scales. Temperature stratification also affected the terminal height of the momentum-dominant region of the vertical buoyant Supply Jets. The applicability of these results to underfloor ventilation design was also discussed. PRACTICAL IMPLICATIONS In designing underfloor ventilation systems, Supply Jet conditions and heat load density have to be considered to avoid thermal discomfort because of excessive temperature stratifications. This study demonstrated, by both numerical simulations and experiments, that thermal length scale can be used as a design indicator to predict thermal stratifications under a floor return and a top return underfloor ventilation setting.
Qiongxiang Kong - One of the best experts on this subject based on the ideXlab platform.
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Numerical study on temperature stratification in a room with underfloor air distribution system
Energy and Buildings, 2007Co-Authors: Qiongxiang Kong, Bingfeng YuAbstract:Abstract In this study, numerical prediction using computational fluid dynamics (CFD) was utilized to investigate air temperature stratification in a room with an underfloor air distribution (UFAD) system. The numerical modeling using CFD computation was validated with physical test in a full size experimental room with an UFAD system. The different Supply air conditions and heat loads were discussed. The results show that the effect of three parameters, heat load, Supply volume flux and Supply air velocity, on room air temperature would be expressed by the length scale of the floor Supply Jet. When the length scale increased from 0.8 to 1.56 m, the ratio of vertical temperature difference between 2.5 and 0.1 m at the occupied zone to the difference between return and Supply air temperature decreased from 0.62 to 0.25. When there was only one local heat source in the room, there was a thermal stratified interface at the occupied zone. The interface height was about 1.42 times the length scale. The results may suggest ways to optimize UFAD design and operation.