Experimental Study Of Flow And Heat Transfer For R114 In Metal Foam Material

With the rapid development of electronic technology,the power electronic devices tend to develop in the direction of miniaturization and high power density,the traditional air or water cooling solution is unable to meet the growing cooling requirements,The thermal management issue becomes one of the bottleneck of limiting the continuous development of electronic equipment,and domestic and foreign scholars have been exploring new type of cooling scheme.Metal foam,as a kind of novel functional material that is prepared by a special process,have both the metal properties and some nonmetal special physical properties,and have some advantages such as low density,high porosity,high specific surface area and high conductivity.Among them,the open cell metal foam can be used as the component material of light and efficient radiator because of the good connectivity between holes.Due to the high hole rate fluid can flow and penetrate through the internal holes,and it has great application prospect in the electronic engineering,civil aviation,aerospace and other fields.In order to provide a cooling solution for high heat flux of electronic components,the plate type heat exchanger,which is filled with the metal foam with different substrate materials,different hole density and porosity,was adopted in this project,and the high temperature refrigerant R114 was chosen as working fluid to experimentally study the fluid flow and heat transfer of R114 within the metal foam.The relationships between solid skeleton material of metal foam,pore structure parameters and the heat transfer,fluid flow performance of refrigerant R114 were systematically studied,and the main research contents and the experimental conclusions could be drawn as follows:(1)The plate type heat exchanger filled with the metal foam was designed and fabricated,and the heat transfer and fluid flow performance of exchanger were experimentally studied by using refrigerant R114 as working fluid.The performance of six pieces of metal foam of aluminum and copper with hole density within 10 ppi~20 ppi and porosity within 0.921~0.959 were conducted under the conditions of heat flux within 26.3~90.3kw·m-2 and mass flow rate within 0.0153~0.0397kg·s-1,and the equivalent surface heat transfer coefficients were obtained under different working conditions.(2)Under the same conditions,the plate type heat exchanger with low hole density,high porosity metal foam has better performance in terms of uniform substrate temperature;With the same hole density and porosity,the exchanger with aluminum foam has better uniform substrate temperature than that with the copper foam.(3)With the same mass flux rate,the equivalent surface heat transfer coefficient of the heat exchanger gets increased with the increase of heat flux;on the other hand,with the same heat flux,the equivalent surface heat transfer coefficient gets increased with the increase of mass flux as well;under the same experimental conditions,the bigger the hole density,the lower the porosity and the greater the solid skeleton lead to the greater of the equivalent surface heat transfer coefficient for the plate heat exchanger.(4)For the two-phase flow of R114 with small mass quality(x?1),the pressure drop on the heat exchanger was almost a constant with the increase of heat flux if the mass flow rate is kept as a constant;on the other hand,the pressure drop of the heat exchanger gets increased with the increase of mass flow rate if the same heat flux conditions were applies for the single liquid R114.The greater the hole density of metal foam,the greater the pressure drop for the heat exchanger.(5)The comparisons between experimental data and correlations were made for the single phase heat transfer of R114,and a new correlation was proposed for heat transfer of R114 within metal foam based on the experimental data.