Numerical Simulation Velocity Profile And Structural Optimization Of Ahu Mixing Box Section

The indoor air quality has a direct impact to human health. Many researches suggest that the common existence of the indoor pollutant concentration over-standard can cause people headache, sleepy and so on.According to this current condition, a series of standards of air quality have issued to provisions the daily average concentration of indoor PM10 should not exceed 0.15mg/m3. The concentration of PM10 in central air conditioning system in public places should be less than or equal to 0.08 mg/m3. As the air filters are important parts in central air conditioning system, the selection and operation condition directly affect the filtering efficiency. The reduce of filter efficiency due to two reasons, the first is the variety of filters which are not detailed classification, the designer select the unreasonable filter. The second is the unreasonable operating conditions can reduce the filtering efficiency.Air Handling Units are important equipments in air conditioning system. With the flexible structures, performance-to-price ratio is quite appropriate and some else advantages, Air Handling Units are widely applied to various central air-conditioning system. However, because of the requirements of spatial dimension and the effect of structure design, there still exit the problem of uneven distribution of air in Air Handling Units can reduce the filter efficiency.The numerical simulation of the Mixing Box and filtering Sections which are commonly used in engineering of AHU (Air Handling Unit) of 5 factories were analyzed in this study, the airflow distribution uniformity in the entrance of the air filter was analyzed by using of analogue computation. On the basis of evaluation indicator, the results manifest that on the condition of the least fresh air ratio, only C factory can satisfy the evaluation indicator, the uneven-essσ=0.079, the velocity of every measuring point is in the fluctuating range1.358～2.038m/s; On the different conditions of fresh air ratio, when the fresh air ratio is 50% the uniformity is the best; The bigger of the air filter, the more homogeneous of the air flow will be, the better effects of filtration will be shown. According to the simulation results, this article gives structural optimizations to Air Handling Units and air filters.