Evaluating the effects of cavitating refrigerant flow on noise radiation from electronic expansion valve: a numerical study

The electronic expansion valve (EEV) is a critical component in air conditioners, responsible for regulating refrigerant flow rate and controlling the cooling or heating performance. However, it is also a significant source of noise. When the valve opening ratio is low, the increased flow velocity of the refrigerant can cause pressure to drop below the vapor pressure and result in a cavitation flow. This type of flow is known to produce higher levels of flow noise compared to single-phase liquid refrigerant flow. A Large Eddy Simulation is utilized to compute the internal flow of the EEV, incorporating a homogeneous mixture model to model cavitation phenomena. The structural vibration of the EEV and its inlet/outlet pipe wall is computed using high-resolution finite element methods with excitation force from internal wall pressure fluctuations. The near and far field noise radiation from the structure is calculated using finite and boundary element methods, respectively. The developed numerical methods are applied to two operating conditions: single-phase and two-phase. The results indicate that the noise radiation from the EEV is 6.5 dB higher in the cavitating flow than in the single liquid flow, closely matching the measured data. The current numerical methodology is expected to be useful in designing low-noise EEV units.