Abstract: During the initial operation phase of the automobile refrigeration system, there is a two-phase flow in the pipeline from the condenser to the expansion valve, generating bubble groups accompanied by high-frequency abnormal sound. This paper designs and verifies three different muffling schemes from the perspectives of reducing two-phase flow and dissipating sound energy. They are the installation of silencer, valve ball opening to increase the valve action value and the installation of orifice muffler. The outdoor/interior temperatures were controlled at 35/27℃. The experimental results show that the orifice muffler eliminates the high-frequency abnormal noise above 9kHz. The valve ball has the best perforating effect, basically eliminating above 8kHz, eliminating the first half of 6-8kHz and reducing the decibel value of the second half, which is acceptable to the human body. Expansion muffler can eliminate high frequency abnormal noise, and the subjective feeling is better than the original state.

Key words: refrigerant, abnormal sound, optimization