Numerical Simulation Of The Dispersion Of Pollutants And Optimization Of Ventilation System Of The Underground Garage

At present，most underground car parks have been building in basements of thehigh．rise or the multi-storey buildings in order to solve the problems of undergroundgarage．Vehicle activities when starting or stopping result in the emission of a numberof harmful substances．Among them the carbon monoxide（CO）which affects humanbeings most severely is the main one．The enclosed nature in the underground garagesmakes the contaminants emitted from cars being difficult to diffuse．So the mechanicalventilation systems are installed in almost all underground garages The purpose ofventilation in the underground garage is to dilute the contaminants emitted from cars toindoor criterion of carbon monoxide concentration limit．In order to ensure the good airquality and save energy in garage，we need to determine reasonable forms of ventilationand air distribution.Based on computational fluid dynamics theory and software FLUENT astheoperational platform, numerical simulation analysis of the air distributionandcontaminant density field of the ventilation of an underground garage is made inthisthesis. In order to improve indoor air quality of underground garage and save energyofventilation system, frequency control of VAV of underground garage is researched.There are four aspects of work done as following:Firstly, a brief review on the aspects of how to improve ventilation efficiency ofunderground garage and the conditions of numerical simulation researches on airdistribution in underground garage by scholars is made at home and abroad.Secondly, the application CFD software FLUENT simulates air distribution inventilation underground garage. The simulations on basis of the κ ε two-equationturbulent model widely used in engineering are made by the method of control cubagewhich has a plainness concept. Discrete equation systems are solved with the SIMPLEalgorithm. The velocity and the CO density distributions in the underground garage aredrew. The results of the simulations are analyzed. In order to analyse the differencesbetween them, the measured data are compared with the data of the results ofsimulations. At last, the feasibility and reliability of the numerical simulation aredemonstrated.Thirdly, two improvement programs are pointed out, against the main factors ofaffect the efficiency of ventilation underground garage. Based on the ventilation effect revealed by the post-processing graphics educed by CFD simulation, the velocity fieldand the CO density field distributions for two improved system prove that theimprovement systems have wonderful effectiveness.Fourthly, By dynamic numerical simulation of the three ventilation programs in theunderground garage, the dynamic changes of the velocity field and the CO densityfield distributions are found out. And then, the dynamic calculation methods of thisprogram and relevant experiences will be made.By the example of project, the processof variable frequency control used in underground garage ventilation system isintroduced. The energy saving potential of the project is also analyzed.