Numerical Simulation Of Multi-polluting Heat Sources Displacement Ventilation

Displacement ventilation is a completely new ventilation way, through which aims such as gaining higher air quality, econmizing energy and getting better ventilation efficiency are realized. The reasonableness of good efficiency, improved hot comfortability and economy energy all open up a promised prospect for applying the ventilation. But research on it is still quite limited. The system can't remove multi-polluting heat sources when used. Present literature do little research on multi-polluting heat sources, while more scholars concentrate on single-polluting heat sources. Therefore, the problem is raised. By establishing numerical simulation on multi-polluting heat sources in the system , effects of air-in parameters and heat sources characters on flow field and temperature field are analized.Based on experimental models, the paper sets up three-dimensional steady heat transfer and flow physical model and mathematical model on a three polluting heat sources after simplification. In flow and heat transfer simulation, K/E model is applied, effect of buoyancy is accounted in energy equation; in viscosity lamination access to the wall, wall functions are used. With software PHOENCS, changes of in-air velocity, in-air temperature, positions of inner heat sources, surface temperature and heat flux quantity are simulated and researched.The numerical simulation helps to further research in heat lamination height, vertical temperature distribution, ventilation efficiency, comfortability and energy energy economy in the system. Main results are as follows:(1) Heat lamination height rises along with air-in flow rising and decreases with air-in temperature decreased. To avoid being bio wed , when innner heat source intensity is under 280w/m2, control air-in velocity within 0.3m/s. To satisfy requests like heat lamination height and hot comfortability in working areas when the intensity reach below 150w/m2, make temperature differece between air-in temperature and working areas temperature no bigger than 4-5Cc.(2) Heat sources effects on heat lamination height and ventilation efficiency of displacement ventilation. The bigger heat source injecting velocity is, the lower heat lamination height is; the higher heat source temperature is, the lower heat lamination height is; the more obvious dispersion the heat source is, the lower heat lamination height is, but if it's dispersed to a degree, heat lamination height and ventilation efficiency will not be affected. In multi-heat sources ventilation room, if heat source intensity is no bigger than 500 w/m2, ventilation efficiency, heat lamination height and hot comfortabilityconform to the standard. So under this condition, apply displacement ventilation. To get better displacement ventilation effect, heat sources should be compactly placed.(3) Differnce between multi-heat .sources and single heat source displacement ventilation room on their heat lamination height and vertical temperature distribution and so on. When heat fluxes of the two conditions are equal, heat lamination height of multi-heat sources displacement ventilation reduces apparently, both zonal temperature and out-air temperature decrease somewhat and mushy region thichness in multi-heat sources is thicker than single heat source. Therefore, compared to single heat source, multi- heat source is disadvantageous to displacement ventilation.(4) Numerical calculating results approximately coincide with experimental data, which means computer models,boundary conditions and calculating results in numerical simulation is reliable.