Study on the noise reduction of refrigerant flow at outlet of capillary tube (relationship between two-phase flow and noise issue)

Recently, Noise reduction for indoor air conditioning units has become necessary. This paper discusses: (1) Exploration at the noise source of capillary tube and outlet plenum. (2) the reason for high-and-low-frequency noise of fluid flow based on R22 fluid flow pattern. (3) the method of noise reduction dependent on supercooling of refrigerant R22 by setting an additional cooler up-stream of the capillary tube. According to the above items, it is necessary for the noise reduction to control bubble contents at an outlet of the capillary tube.