In this study, a CFD approach is used to investigate the characteristic of the underfloor air distribution (UFAD) system. The first objective of this study is to establish suitable boundary conditions for this system. The solid wall boundary temperature and the scheme of the air supply velocity are varied in the numerical simulation model to see their effects on the properties of the indoor environment. Secondly, since the cold air is delivered from the bottom, the indoor environment is divided into three zones, the occupied, unoccupied, stratified zones. The stratified zone is between the occupied and unoccupied zones. The thermal stratification plane lies at a certain level in the range of stratified zone. The level of the thermal stratification plane is determined with the stratification height (SH). The throw height (TH), which is the height of the jet air supply, also lies in the range of the stratified zone. Both SH and TH become lower at the higher solid wall boundary temperature. The boundary condition of higher air supply velocity also increases the SH and TH. Finally, the numerical simulation results are similar to experimental measurements by applying the recorded temperature before the UFAD system is turned on as the solid wall boundary temperature; and using the different air supply velocity for the air supply devices.

In this study, a CFD approach is used to investigate the characteristic of the underfloor air distribution (UFAD) system. The first objective of this study is to establish suitable boundary conditions for this system. The solid wall boundary temperature and the scheme of the air supply velocity are varied in the numerical simulation model to see their effects on the properties of the indoor environment. Secondly, since the cold air is delivered from the bottom, the indoor environment is divided into three zones, the occupied, unoccupied, stratified zones. The stratified zone is between the occupied and unoccupied zones. The thermal stratification plane lies at a certain level in the range of stratified zone. The level of the thermal stratification plane is determined with the stratification height (SH). The throw height (TH), which is the height of the jet air supply, also lies in the range of the stratified zone. Both SH and TH become lower at the higher solid wall boundary temperature. The boundary condition of higher air supply velocity also increases the SH and TH. Finally, the numerical simulation results are similar to experimental measurements by applying the recorded temperature before the UFAD system is turned on as the solid wall boundary temperature; and using the different air supply velocity for the air supply devices.

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