Without engine noise, the cabin of an electric vehicle is quiet, but on the other hand, it becomes easy to perceive refrigerant-induced noise in the automotive air-conditioning (A/C) system. When determining the A/C system at the design stage, it is crucial to verify whether refrigerant-induced noise occurs in the system or not before the real A/C systems are made. If refrigerant-induced noise almost never occurs during the design stage, it is difficult to evaluate by vehicle testing at the development stage.
This paper presents a 1D modeling methodology for the assessment of refrigerant-induced noise such as self-excitation noise generated by pressure pulsation through the thermal expansion valve (TXV). The GT-SUITE commercial code was used to develop a refrigerant cycle model consisting of a compressor, condenser, evaporator, TXV and the connecting pipe network. In order to simulate the vertical motion of the valve by the refrigerant fluid force, every component such as ball valve, spring and friction of TXV was modeled in detail. A spring-mass-damper model was used to calculate the balance of forces acting on the valve. A ball valve model was also used to calculate fluid forces passing through the valve in the detailed model. Finally, flow rate, thermal and hysteresis characteristics of TXV were calibrated to match the TXV performance data.
Using this model, the 1D Navier-Stokes equations were solved by an explicit solver with a small time step to predict the behavior of refrigerant pressure pulsations. This paper discusses the correlation of the simulation results with measured data at vehicle level and also compares calculated pressure pulsations in the refrigerant cycle with different TXVs.