Numerical Investigation on the Internal Flow Field of Electronic Expansion Valve as the Throttle Element

摘要

As one of the key components of the heat pump system, the electronic expansion valve mainly plays the role of throttling and reducing pressure in the heat pump system. The refrigerant flowing through the orifice will produce complex phase change. It is of great significance to study the internal flow field by means of CFD calculations. Firstly, a three-dimensional fluid model is established and the mesh is divided. Secondly, the phase change model is selected, the material is defined and the boundary conditions are determined. According to the principle of the fluid passing through thin-walled small holes, the flow characteristics of electronic expansion valve are theoretically analyzed. Then the flow characteristics of expansion valve are numerically calculated, and a bench for testing mass flow rate of the expansion valve is built. Then the theoretical value, CFD value and experimental value are compared to verify the correctness of the established three-dimensional fluid model. The flow rate changes of expansion valve are studied under the condition of changing geometric parameters such as the cone angle of the valve spool and the radius of circular arc at the end of the valve seat. According to the momentum theorem, the steady hydraulic force is theoretically deduced. Then the changes of steady hydraulic force are studied under the conditions of different inlet pressure and outlet pressure. At the same time, there also analyzes the effects of the conditions of different valve spool cone angle and valve seat arc radius on steady hydraulic force on the valve spool. Finally, transient analysis is carried out by using dynamic mesh technology. The speed of spool movement is defined by User Defined Function (UDF). Under constant pressure difference conditions, the influence of the spool movement on the hydraulic force and outlet flow of the valve is studied. And the change of the internal pressure field are shown.