Two-Phase Flow Visualization in the throttle of expansion valve

Recently, there has been an increase in demand for low-noise air conditioner. The reduction of noise generating from the expansion valve in an air-conditioner is particularly important. In order to design a low-noise operating valve, it is necessary to understand the flow characteristics of the refrigerant passing through the throttle of the valve. Therefore, we manufactured an expansion valve with a new throttle design. We compared the performances of the original and new throttle design by monitoring the refrigerant flow conditions and the acoustic noise generation. As results, it was confirmed that refrigerants flow of the upstream of throttle influences in predominance. The reduction in the noise power spectra in the high frequency domain has been made, which is the one that poses particular problems for the human ear.