The Research For Matching Between Condensing Outside The Pipe And Boiling Heat Exchange Of The Dielectric Liquid In Two-phase Immersion Liquid Cooling System

At present,the scale of data center is expanding,and a large number of electronic chips with high power level are integrated,so the heat dissipation of chips is inevitably concerned.The traditional air cooling technology has low cooling capacity and high energy consumption,which limits its application in data centers.The liquid in the two-phase immersion liquid cooling system directly contacts the electronic components,which realizes the dual utilization of liquid sensible heat and latent heat.It has the advantages of compact structure,low heat transfer thermal resistance and high heat dissipation efficiency.Therefore,it has a good application prospect in the field of electronic component heat dissipation.At present,the research on two-phase immersion liquid cooling system mainly focuses on the enhanced heat transfer of pool boiling and the properties of liquid,but there is less research on the condensation heat transfer characteristics of dielectric liquid vaporization outside the condenser pipe and the condensation and cooling water circulation system in the system,which is the basis for the stable and continuous heat dissipation of electronic components by the two-phase immersion liquid cooling system.Therefore,the research on the matching of boiling heat transfer and condensation heat dissipation based on the two-phase immersion liquid cooling system is of certain significance in this paper.Firstly,a two-phase immersion liquid cooling experimental platform is built in this paper.Taking the typical dielectric liquid HFE-7100 as the heat exchange medium,and the pool boiling curve is tested,which laid a foundation for the efficient and safe application of heat dissipation of the system.The variation law of condensation heat transfer performance of HFE-7100 outside different types of pipes with cooling water inlet temperature and cooling water flow is studied experimentally.The experimental results show that the condensation heat transfer coefficient of HFE-7100 outside the smooth pipe increases with the increase of cooling water inlet temperature,while the3D-reinforced pipe is opposite;The condensation heat transfer coefficient outside the smooth pipe and the 3D-reinforced pipe increases with the increase of water flow,but tends to be stable with the increase of water flow.The condensation heat transfer mechanism of HFE-7100 outside different types of condensing pipes is analyzed to provide reference for continuously enhanced heat transfer and setting the cooling water operation parameters of the system.Then,the matching degree between the heat exchange of condensation and cooling water circulation system and the boiling heat transfer of dielectric liquid pool boiling system in unit time for different operating conditions is experimentally studied,and analyze the negative consequences of the heat dissipation of the condensing and cooling water system being significantly higher or lower than the heat transfer of the pool boiling system,and then the importance of operating the system under the heat transfer matching condition is emphasized.The energy efficiency of the system is analyzed by using the Coefficient of Performance(COP)and Power Usage Effectiveness(PUE).And the system can obtain the highest COP(or the lowest PUE)when the heat is just matched.In the case of system heat matching,the COP of the system gradually decreases with the increase of cooling water flow rate,while the trend of PUE changes in the opposite direction.According to the minimum cooling water flow under the condition of heat matching,optimizing the cooling water flow can improve the COP of system operation.Finally,the exergy analysis method is introduced to study the available energy of the system,so as to reduce the irreversible loss in the heat transfer process and improve the heat recovery value of the outlet cooling water.Exergic efficiency was correlated with the Standardized Mean Time to Failure through net efficiency,and the proximity between the availability of the two-phase immersion liquid cooling system during the whole operation period and the availability of the ideal state is quantified.Based on the experimental data,the effect of cooling water operating parameters on the net efficiency of the system is studied.Based on experimental data to investigate the effect of cooling water operation parameters on the net efficiency of the system,the results show that increasing both cooling water inlet temperature and flow rate contribute to the net efficiency of the system,with the effect of cooling water inlet temperature being more significant.Then,the operation strategies with PUE and net efficiency as the optimization objectives are proposed respectively,and the energy cost and loss cost of the system under different operation strategies are quantified by economic analysis method.For the system designed in this paper,the reduction of loss cost is significantly greater than the increase of energy cost.It is reasonable to increase the available energy during the whole operation period of the system by increasing energy consumption.