Heat Transfer Characteristics Of Underfloor Plenum

Nowadays, the issue of building energy consumption and indoor air quality arouse more and more attention. Research on underfloor air supply (UFAD) system has been conducted and applied gradually for it can provide better indoor thermal comfort and indoor air quality more efficiently.In view of the past, the air temperature in the plenum is lower than the floor's. They through heat transfer leads to the air temperature in the plenum rose, the methods which caculate the space load of the UFDA, are considered the influence of underfloor (UF) plenum gain heat, but the methods is too unaccurate. This paper study the UF plenum and other building envelope heat transfer process. To study the heat transfer process of UF plenum that needs to start from the air temperature on the floor surface, The floor surface temperature and other envelope temperature, mainly influenced by solar radiaton heat, so the window area is directly related to receiving heat from the solar radiation heat. It makes the heat sources proportion in the space distribution changes, and also affects the supply air temperature and the envelope temperature in the room. Leading to the space air conditioning load have changed.This paper study the air temperature in plenum and the envelope temperature in the room, through the situation by following:change ration of window-wall areas, change size of room, change the characteristics, change intensity of solar radiation and so on. Mainly use the Matlab programming software to calculate the nonlinear heat balance equations, the results obtained and analyzed the temperature. Finally, we use the computational fluid dynamics to study how the outlet temperature on the floor changes, and also verify the theoretical results.The results show that, the certain, the UF plenum air heat gain along with the increase of ration of window-wall areas and the decrease of room area rise. The hollow window's resistance of heat transfer bigger than the ordinary window's. So, its UF plenum air heat gain more than the ordinary window's. At 9 o'clock of solar radiation intensity is smaller than at 12 o'clock of solar radiation intensity, so its UF plenum air heat gain less than the 12's.