Experimental Study On The Enhancement Of Flow And Boiling Heat Transfer In Copper Foam

The open-cell metal foam was a new type of functional material prepared by a special process.It had many advantages such as: low density,high porosity,high specific surface area,and high specific thermal conductivity,moreover,the connectivity between the pores was good,the porosity was high and et al,which making it had excellent heat exchange performance has huge application prospects in the field of heat dissipation of electronic devices.In this paper,the purpose was to provide cooling for the heat dissipation of high heat flux power electronic components,copper foam with different structural parameters(porosity and pore density)was taken as the research object,deionized water was selected as the working fluid,and the single relative flow and two-phases boiling heat transfer performance of copper foam were systematically studied.The effects of structural parameters,mass flow rate and inlet supercooling on heat transfer and flow resistance performance were analyzed.First,the structural of different copper foam samples under different are characterized,including: Scanning Electron Microscope(SEM)was used to obtain the internal pore structure of copper foam samples;and contact angle measuring instrument was used to measure the contact angle of the copper foam sample to understand the surface wettability of copper foam,that is,the hydrophilic and hydrophobic properties of copper foam.Secondly,using deionized water as the experimental working fluid,a single-phase flow and heat transfer test system with copper foam was designed and built.The experimental results showed that the copper foam sample had a porosity of 80% and a pore density of 90 PPI.The pressure drop was the smallest,and the heat transfer coefficient was the largest,and the maximum heat transfer coefficient is 6 times that of the empty channel.Increasing the pore density of the copper foam was helpful to improve the heat transfer coefficient,but at the same time,it needed to pay more pump power loss at the cost.Thirdly,deionized water was used as the working medium,a two-phase boiling heat transfer test system with copper foam was designed and built.The study found that: in the range of medium and high heat flux,low porosity samples can effectively suppress the increase in wall superheat.Compared with the sample with copper foam pore density of 90 PPI(Pore Per Inch),and the pore density of 45 PPI,which was more conducive to the smooth discharge of the generated bubbles.Increasing the mass flow rate and the supercooling of the inlet caused the superheat of the wall surface of the Onset of Nucleate Boiling(ONB)to appear delayed,however both of them were beneficial to the boiling heat transfer coefficient and critical heat flux(Critical Heat)Flux,CHF),thereby improve the boiling heat transfer performance of copper foam.Finally,through the analysis of the pressure pulsation results,the copper foam sample with lower pore density and lower porosity can effectively suppress the pressure drop pulsation and ensure that the flow boiling of the internal pore structure of the copper foam was a stable flow boiling state.Increasing the mass flow rate can also improve the boiling heat transfer performance of copper foam,but it is easy to cause a larger pressure drop.