Analysis of the Physical Behavior of Refrigerant-Flow Induced Noise in an Automotive HVAC System by a Coupled Simulation

Under the blazing sun in summer, it occasionally exhibits excessive tonal noise in the automotive cabin when refrigerant system is turned on. After that, a transient noise can be perceived for a while. Hissing noise is generated by the jet of refrigerant from the thermal expansion valve (TXV) and then can propagate and interact with downstream components such as the pipe and evaporator. Finally, significant airborne noise can be emitted. However, the mechanism of noise generation is still incompletely understood because it is difficult to reveal all by experiments. In this paper, hissing noise simulation method coupled with CFD, FE and BEM are developed. The pipe, evaporator and heating, ventilation and air-conditioning (HVAC) unit are scanned and modeled. Using this method, frequency characteristic of fluid and structure and also acoustic characteristic of HVAC unit case was analyzed to get insights into the nature of hissing noise. Some physical behaviors of hissing noise were obtained by simulation.