Experimental and numerical study on characteristics of super-linear mass flow rate and asymmetric cavitation in novel rotary-baffle curved-channel electronic expansion valve for refrigerator

Abstract

Capillary tubes, as the expansion devices in refrigerators, are unable to actively match cooling capacity and load, which will increase the energy consumption. Moreover, due to the limitations of miniature valve needle machining accuracy and structural strength, orifice-type EEVs are not suitable for low mass flow rate in refrigerators. A novel rotary-baffle curved-channel electronic expansion valve (RBCC-EEV) is proposed to replace capillary tube to achieve flow regulation in household refrigerators. Based on the special structure and regulation principle of RBCC-EEV, characteristics of mass flow rate and cavitation are studied experimentally and numerically, respectively. Experimental results show that, as opening ratio (OR) increases, the synchronous changes in the inlet area and length of the curved channel lead to a super-linear variation in mass flow rate, with increase rate growth from 0.018 kg h−1 OR−1 to 0.061 kg h−1 OR−1. Numerical results show that, under centrifugal forces, the pressure difference along the normal direction of the streamline leads to the differences in degree of cavitation, which is called asymmetric cavitation phenomenon. In addition, under the influence of this phenomenon, the prematurely cavitation of refrigerant near the inside surface will block the inlet of curved channel early, resulting in a 3.4 % decrease in mass flow rate.