Numerical Study Of Indoor Air Quality In A Underfloor Supply Air Conditioning Room

In this day, people spend more and more time in the office and require the better indoor environment quality, the application of air-conditioning system become more widespread. How to improve indoor air quality and save energy efficiency, as well as large space of local thermal environment of personal control has become an important direction of the development of the office building air conditioning. One of the way to solve this problem is to use the underfloor ventilation system. Indoor air quality in an enclosure with underfloor ventilation systems were investigated using three-dimensional Computational Fluid Dynamics (CFD) analysis in this paper.Numerical simulations were performed on a full-sized environment chamber with changes in the supply velocity and various return air system. The influence of these factors on the indoor air diffusion, temperature field and the pollutants' concentration field were studied.The results reveal when the supply velocity was lower than 0.9m/s, indoor air diffusion was displacement ventilation, the actived pollution(CO₂)was stratified distribution along the room height, Indoor air quality was better; when the supply was higher than 0.9m/s, indoor air diffusion was mixing ventilation, it was not conductive to the exclusion of the actived pollution(CO₂),but was in favor of the exclusion of the passived pollution(benzene).The results also reveal that when the the thermal length scale of the supply jet was less than 1, the return air system has some influences on the indoor air distribution. when the return air sysem was top return, the temperature gradient along the room height direction was lower than the floor return, and the top return was in favor of the exclusion of the actived pollution(CO₂). When the thermal length scale of the supply jet was more than 1, the return air system has few influences on the indoor air distribution and the exclusion of the actived pollution(CO₂). At the various of the thermal length scale of the supply jet, the data show that the two return air systems effected on the the ventilation efficiency of benzene were both almost 1, but when the floor return, the ventilation efficiency of benzene was larger.