Comparison And Exploration On Calculation Methods Of Aerodynamic Noise Generated In Air Conditioning Duct System

The air conditioning system is indispensable to build the comfortable indoor environment,as it has been widely applied in many fields,such as housing,commerce and industry.While providing the suitable temperature and humidity,the noise problem caused by it is also attracting more and more attention,for that will not only affect work efficiency,reduce the quality of life,but also have a negative impact on physical health.The noise of HVAC system involves all aspects of the whole air conditioning system,instead of only a single component.Compared with the fan noise,there are relatively few studies on the noise of pipes and vent,whose actual effects should not be ignored.This topic focuses on the noise problem of air flow in air conditioning duct:First of all,this paper compares the contents of HVAC noise mentioned in our Practical Heating Air Conditioning Design Manual^[1],the ASHRAE Handbook^[2]and the CIBSE guide B^[3],finding that the obvious difference is the calculation of aerodynamic noise through the branch take-off.Then,the experimental test was carried out to explore the difference between the aerodynamic noise calculation of the two algorithms for branch take-off.After setting up the test table to measure the aerodynamic noise value in the branch take-off and comparing the experimental data with the theoretical formula calculation results,it is found that the result of the method in ASHRAE Handbook is closer to the actual situation.Meanwhile,the pressure field and sound pressure distribution inside the branch take-off are simulated by the joint numerical simulation of CFD and LMS virtual lab,which found that the algorithm result from ASHRAE Handbook is in better agreement with the simulation data from the comparison between simulated and theoretical results,proving the desirability of the algorithm in ASHRAE Handbook.By means of numerical simulation,the three factors which may affect the noise of branch take-off,such as section shape of duct,transition angle of pipeline and the proportion of flow distribution,are explored,and t he relationship between the above factors and the value of noise is obtained,finally.