Research On Submerged Liquid-cooled Boiling Heat Transfer And Optimization Of High-density CPU

Reducing the energy consumption of the data center cooling system is one of the key measures to achieve energy saving and emission reduction in the data center.Traditional precision air conditioners cannot solve the problems of high power,local hot spots,etc.,resulting in high energy consumption or even incomplete heat dissipation of the cooling system.On the other hand,with the rapid development of information technology,the requirements for the computing power of the server continue to improve,and the heat production of the server has increased significantly.Air cooling and water cooling technologies can no longer meet the cooling requirements of the server,posing a threat to the safe operation of the server,and the traditional cooling technology has encountered a bottleneck.According to literature reports at home and abroad,a new type of server liquid cooling technology began to appear and received attention.This paper focuses on the problem of boiling heat transfer with high heat flux and low boiling point,uses a combination of experiment,simulation and theoretical analysis to study the boiling heat transfer mechanism and application form of electronic fluorinated liquid under high heat flux density,and provides theoretical support for the application of electronic fluorinated liquid to heat dissipation of electronic components with high heat flux density.The main innovative work and related conclusions of the thesis are as follows:First,a server board liquid cooling experiment platform is built to collect data such as CPU power,core temperature,wall temperature,as well as the temperature of cooling liquid and gas pressure.The energy efficiency of the liquid cooling system is given.Through the calculation of system exergy loss and exergy efficiency,the main exergy loss aspects and waste heat utilization potential are pointed out.Based on the experimental data,the heat transfer coefficient(HTC)for phase change liquid cooling of CPU server board is established and verified by experiments.The effects of characteristic velocity and length on the Reynolds number(Re)of boiling heat transfer are analyzed,and the methods of enhancing CPU wall boiling heat transfer is given.In order to further study the cooling and heat transfer mechanism of high heat flux CPU,a high-density CPU submerged liquid cooling experiment platform is built.A prediction formula for saturated boiling HTC in the pool is established based on the liquid physical parameters and the influence of the characteristics of the heat transfer surface of the CPU,such as surface roughness and liquid contact angle.The accuracy is verified by experiments.On the basis of experimental study,a numerical model of phase change heat transfer based on pool boiling was established.The influence of CPU server board spacing on critical heat flux(CHF)is analyzed,and the minimum distance to ensure the normal heat exchange of server motherboard is given.Finally,the effects of CPU power,liquid contact angle and liquid thermal conductivity on boiling heat transfer are quantitatively analyzed,and the methods to enhance CPU heat transfer are given.This paper provides a reference for the liquid cooling mode of high-density CPU and the development of low boiling point heat exchanger,which has important value.This paper has important reference value for the development of liquid cooling of high-density CPU and low boiling point heat exchanger.