Numerical Simulation And Experimental Study Of Pump-Driven Two-Phase Flow Heat Transfer System With Water As Working Fluid

With the continuous development of power electronics technology,electronic equipment is gradually developing towards miniaturization and high power,which leads to the significant increase of the dissipated power or heat flux of electronic power components.The traditional cooling methods such as air cooling and liquid cooling can no longer meet the requirements of heat dissipation,and the problem of heat dissipation and cooling has become the bottleneck restricting the development of power components.In view of the characteristics of high power electronic equipment,such as high heat flux,high requirement of temperature uniformity,and discrete distribution of heat sources,this paper proposes to use distilled water as working fluid,power components are arranged on the evaporator,and pump-driven two-phase flow heat transfer system is used to carry out heat dissipation and cooling,and the effects of different mass flow rate,heat flux and PPI on the heat transfer performance and temperature uniformity of the evaporator were systematically studied with steady state conditions.In addition,in order to obtain the dynamic response characteristics of the heat transfer system at a given mass flow rate,a simulation model of the pump-driven two-phase flow heat transfer system was built based on Matlab/Simulink platform to study the dynamic characteristics of the system under a given mass flow rate and variable power conditions,and the reference experience and data beneficial to engineering practice were obtained.Through the experimental research and simulation analysis of the pump driven two-phase flow heat transfer system,the main work completed in this paper and the main conclusions are as follows:（1）The plate evaporator filled with foam metal was designed,processed and fabricated.Aiming at the heat dissipation and cooling requirements of high-power electronic components,a pump-driven two-phase flow heat transfer system was designed and built.On this basis,the steady state heat transfer of the evaporator filled with foam metal with different mass flow rate,heat flux and PPI was studied by using distilled water as working fluid.（2）The results of steady-state heat transfer experiment show that in the pump-drive two-phase flow heat transfer system,the mass flow rate of circulating working fluid and the heat flux on the evaporator are the key parameters that affect the temperature uniformity on the evaporator substrate and the heat transfer performance of the evaporator.In terms of temperature uniformity,the temperature uniformity on the evaporator substrate gradually deteriorates with the increase of heat flux（8.93k W/m²～45.39k W/m²）when the mass flow rate remains constant.When the heat flux is constant,the temperature uniformity on the evaporator substrate is improved with the increase of mass flow rate(9.9×10^-5kg/s～5.8×10^-4kg/s).In terms of the heat transfer performance of the evaporator,the equivalent surface flow boiling heat transfer coefficient on the inner wall of the evaporator is jointly affected by the heat flux of the evaporator and the flow pressure drop of the working fluid in the evaporator,that is,the comprehensive heat transfer performance of the evaporator is mainly affected by the combined action of the above two mechanisms,so that under different mass flow rate conditions,the equivalent flow boiling heat transfer coefficient on the inner wall of the evaporator shows different trends with the increase of heat flux.（3）Under the same mass flow rate and heat flux,the equivalent flow boiling heat transfer coefficient of the inner surface of the evaporator filled with 40PPI foam copper is larger than that of the 20PPI foam copper.At the same time,the temperature uniformity on the 40PPI evaporator substrate is better than that on the 20PPI evaporator substrate.The uniformity of temperature distribution on the evaporator mainly depends on the pressure drop of the working fluid in the evaporator along the flow direction.Under the same conditions,the smaller the flow pressure drop of the working fluid in the evaporator,the better the temperature uniformity on the evaporator.In order to effectively improve the uniformity of temperature distribution on the evaporator substrate,it is suggested that the equivalent flow velocity of two-phase working fluid in the evaporator should be strictly controlled in engineering practice.Therefore,small mass flow rate and high mass quality operation mode or large mass flow rate and low mass quality operation mode can be adopted to effectively control the temperature uniformity of evaporator substrate.（4）Under the same conditions,the correctness of the simulation analysis model of pump-driven two-phase flow heat transfer system based on Matlab/Simulink platform is verified by comparing with the experimental data;On this basis,the dynamic characteristics of the simulation model with the change of parameters such as circulating mass flow rate and heating power are analyzed systematically,and the influence rules of different parameters on the dynamic characteristics of the heat transfer system are obtained,which accumulates experience data for the efficient control and regulation of the system in engineering practice.