Experimental Analysis to Mitigate Flow-Induced Noise in Expansion Devices

摘要

Flow-induced noise produced by expansion devices can be very disturbing to the user, especially when the device is in the close vicinity of the occupants. This paper characterizes the relationship between flow-induced noise and the flow regime, which may aid the design process of future geometry improvements of thermostatic expansion valves (TXV). A refrigerant loop using pumped R134a with appropriate pre-conditioning sections to vary inlet and outlet conditions is connected to a TXV and an automotive microchannel evaporator. The experiment is set up in a semianechoic chamber using microphones, accelerometer, and high-speed pressure transducers. Noise spectrum analysis is performed using the Fast-Fourier-Transform method. Visual access is made through transparent test sections. To the authors' best knowledge, it is the first-time noise measurements have been linked with two-phase flow regime information for TXV with an adjacent evaporator published in the open literature. A gurgling noise vibrating at 4.4 kHz and 6.0 kHz and a hissing noise at 10.3 kHz is observed. The gurgling noise mostly appeared in the wavy and slug flow regimes, while the hissing noise appeared in all kinds of flow regime. The acceleration signal and microphone signal matched each other perfectly, meaning that the acceleration signal could be used to simulate the flow-induced noise. This paper also proposes some possible geometry improvements based on the results, which could be applied to the industry after further experimental testing.