Numercal Simulation On The Indoor Air Quality Of Displacement Ventilation

Since the energy crisis in 1970's, because of the request of energy-saving, the use of air-condition rate and the flux of fresh breeze has been reduced within the scope of whole world.However, such a reduction of fresh wind supply causes an increase of concentration of indoor pollutants and sometimes generates a nonuniform distribution of air temperature and contaminants concentration, the indoor air quality declined. According to the investigation, people spend more and more time indoors in modern society, the indoor environment quality becomes more and more important. The indoor air quality relates to the body health and work efficiency of the indoor personnel directly. Adopting the traditional mixture ventilation, it is difficult to improve the indoor air quality due to the limit of the fresh breeze's mass flow,unless we consume more energy. Therefore, how to solve the thermal comfort and indoor air quality (IAQ) problems without consuming too much energy is a very challenging topic. As a new ventilation style, the displacement ventilation can improve the indoor air quality and has relatively small energy consumption,so its application becomes more and more extensive.In the dissertation,the physical and mathematical model for a assembly room with displacement ventilation system are established.Turbulent flow in the air-condition room is described by using the standed k ?εturbulence model linked with the wall function,and the finite volume method is used to discrete the governing equation. According to different working conditions,The velocity field,temperature field and CO2 concentration field in the room are simulated by the software FLUENT.The impacts of air-in temperature,velocity and different location of the diffuser on indoor-air quality are analyzed.In addition,at the same boundary condition,the displacement ventilation and mixture ventilation's effects is discussed.Finally,comparing with available experimental date,the feasibility and correctness of the simulation method used in this paper is proved.The numerical method and the result of in this paper can provide theory basis and designing reference for the control application of displacement ventilation system.In addition,it can also provide the guiding significance for the designing of airflow organization in the air-conditioned room,evaluating of air quality in the room,and directing the energy-saving in construction. .