Numerical Simulation On Characterizing Stratified Airflow Of Displacement Ventiletion

Compared with the traditional mixing ventilation, displacement ventilation, a new concept in air-conditioning system, has showed several remarkable advantages on many occasion. Howhever, in China, the research of displacement ventilation has just been carried out. There are a lot of problems being solved before its extensive application.In this paper, for the outdoor condition in China, basing the existing domestic and foreign production, the technique of computational fluid dynamics (CFD) is adopted to simulate the character of stratified airflow in displacement ventilation, including the influence of heat source, wall and room height to the character of stratified airflow in the room, the character of stratified humidity and contaminant in displacement ventilation and the influnce to them.To validate the result of simulation, in this paper, the experiment date of the France LET laboratory was used to contrast it. Other simulations are based on it. The indoor zero equation model and SIMPLE algorithm was used in this simulation. To reduce the griddings and save time, half of the room was simulated as its symmetry.The paper shows that the position of heat source doesn't affect the uniformity of temperature field, the influence of heatflow was mostly found in the temperature of upside indoor air, the height of temperature leap layer and temperature grads doesn't alter to the changing height of room, the heigher room advance the effect of displacement ventilation, so the displacement ventilation should more used in the large place.The stratification phenomenon also exists for the humidity in displacement ventilation room, for heat source with humidity, the moisture and relative humidity will rise with the large heat loading, so the displacement ventilation adapts to the room with heat source with more humidity.The stratified contaminant concentration exsits in displacement ventilation room, the feather flow from the heat source with pollutant takes the contaminant to the upside, the contaminant will not almost diffuse, they have not interactinal effect if there are a certain distance between them.