The Study On HVAC Pipe Acoustic Characteristics

With the development of modernization,the pace of life and work has become more and more fast.The time when people stay in building is far greater than the time people living in outdoor,so the building indoor environment plays an important role in people's work efficiency and health.Air conditioning system is widely used in public buildings and civil buildings.The air conditioning system can provide a comfortable building thermal environment and good air quality for people,but at the same time can produce noise.The pipeline of the air conditioning system has a critical effect on the noise propagation inside the building.When the noise of air conditioning system reaches a certain value,the acoustic environment in building indoor and outdoor will be affected by the noise of air conditioning system.From the two aspects of sound transmission of HVAC pipe and turbulence noise caused by air flow in the pipeline,the simulation analysis of air conditioning pipeline is carried out by using HVAC knowledge and acoustic knowledge and the optimization scheme is put forward.To summarize the main contents of this paper,this paper studied from the acoustic characteristics of air conditioning pipeline such as following aspects :1?Extend the theory of transmission loss,calculate the transmission loss of the main air pipe parts in the HVAC system,Analysis the transmission loss of the SPL spectrum calculated with different angle,uniform and variable cross-section,different local pressure loss coefficient and other factors on the effect of sound transmission loss in the elbow.2?Calculated the transmission loss of variable reducing pipe,including the expansion type and tapered,tianyuandifang pipeline.And compared with the trumpet tube theory,transmission theory is not necessarily consistent with all the noise frequency,the transmission loss will appear abnormal point.3?Calculate the transmission loss of three-way pipe,find that the transmission loss in three-way pipe existence a universal law,the transmission loss in three-way pipe will increased with the change of the import / export area ratio.With the inlet and outlet sectional area of rectangular three pass,the noise transmission loss of Y shape 90 degree three-way pipe pass is greater than Y shape 45 degree three pass,and the T shape three-way pipe pass noise transmission loss is minimum.4 ? To calculate the modal frequency of end tuyere,from fluid mechanics standpoint to analysis the fluid field,transform time-domain to frequency-domain,calculate the sound field of the terminal tuyere than propose optimization measures.Compare with the end air noise before and after optimization,the results shows that the surface howling control are better.