Numerical Study On The Evaporator And System Design Of Pump-Driven Capillary Phase Change Loop

With the development of electronic technology,the traditional thermal management solutions cannot meet the need of heat dissipation of high-power electronic equipment.In this paper,loop heat pipe and pump-driven two-phase loop was combined,and the influence of some parameters of evaporator of pump-driven capillary phase change loop system on the performance was studied and a pump-driven capillary phase change loop system which combines both active and passive heat dissipation technologies was designed.The specific research contents are as follows:(1)The structure model of the evaporator of a pump-driven capillary phase change loop was established,and the structure of evaporator was determined as upper evaporation and lower liquid supply.On this basis,the mathematical model of two-phase transient numerical simulation of the evaporator was established.(2)In order to study the influence of some parameters of the evaporator on the liquid-vapor interface in the wick,VOF multiphase model was used in two-phase transient numerical simulation and the transient model of evaporation-condensation phase change was realized by using UDF.The generation and movement of the liquid-vapor interface in the wick during start-up process were obtained.The heat flux and wick porosity have great influence on the phase change in the evaporator.(3)A three-dimensional calculation model of the evaporator was established,and Eulerian multiphase model was used for the transient numerical simulation.The influence of vapor groove on pump-driven capillary phase change loop was study,and optimized the parameters of the evaporator of pump-driven capillary phase change loop.Different vapor groove sizes and structures were studied,the evaporator with vapor groove in the upper wall has better performance,and the optimum sizes of groove are 0.66 mm for width and 0.33 mm for height.Simulating the evaporator with different wick porosity,the result shows that the optimum wick porosity is 0.7for the rated heat flux of 20 W/cm~2.The evaporator with different wick materials was simulated,the result shows that with the increase of thermal conductivity of wick material,the temperature of evaporator heating surface and equivalent thermal resistance decrease.At the same time,the diffusion of vapor phase increases.The double-layer wick can reduce the vapor phase diffusion and prevent the evaporator from drying out when the temperature does not exceed a reasonable range.The above conclusions provide a basis for studying the mechanism of phase change in the wick and optimizing the design of pump-driven capillary phase change loop system.(4)According to the simulation results,the size of evaporator was optimized,and the components of pump-driven capillary phase change loop system was designed and selected.Based on the design parameters,the pressure drop of the system was analyzed.