Effects of electronic expansion valve tube arrangement on reduction of two-phase refrigerant throttling noise

Abstract

The two-phase throttling noise in electronic expansion valves (EEVs) of a multi-split air conditioner may exhibit different intensities due to the variable EEV tube arrangements. The purpose of this study is to experimentally investigate the influence of EEV tube arrangement on the throttling noise, and to find a suitable tube arrangement for noise reduction. A throttling noise testing rig is constructed to investigate the influence of tube arrangement including the inclination angle of inlet tube and the refrigerant flow direction. The test conditions for tube arrangement include an inlet tube inclination angle of 0°–90° as well as the flow direction from tube P (parallel to the valve needle direction) to tube V (vertical to the valve needle direction) and from tube V to tube P; and the test conditions for refrigerant include a mass flow rate of 30–90 kg h−1 and an inlet quality of 0.02–0.4. The experimental results show that, the increase of inlet tube inclination angle may weaken the throttling noise, and the sound pressure level (SPL) of throttling noise is decreased by 20.1 % as the inlet tube inclination angle increases from 0° to 90°; and the refrigerant flow direction from V–P (tube V to tube P) instead of P–V (tube P to tube V) may attenuate the throttling noise. The tube arrangement with inlet tube inclination angle of 90° and flow direction from V–P is suggested for minimizing the throttling noise in multi-split air conditioners.