Heat Transfer Performance of Porous Copper Fabricated by the Lost Carbonate Sintering Process
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Heat Transfer Performance of Porous Copper Fabricated by the Lost Carbonate Sintering Process Liping Zhang1, David Mullen2, Kevin Lynn2 and Yuyuan Zhao1 1 Department of Engineering, University of Liverpool, Liverpool L69 3GH, UK 2 Thermacore Europe Ltd, Ashington, Northumberland NE63 8QW, UK ABSTRACT The heat transfer coefficients of porous copper fabricated by the lost carbonate sintering (LCS) process with porosity range from 57% to 82% and pore size from 150 to 1500 µm have been experimentally determined in this study. The sample was attached to the heat plate and assembled into a forced convection system using water as the coolant. The effectiveness of the heat removal from the heat plate through the porous copper-water system was tested under different water flow rates from 0.3 to 2.0 L/min and an input heat flux of 1.3 MW/m2. Porosity has a large effect on the heat transfer performance and the optimum porosity was found to be around 62%. Pore size has a much less effect on the heat transfer performance compared to porosity. High water flow rates enhanced the heat transfer performance for all the samples. Key words: Porous media, heat transfer, porous copper, LCS INTRODUCTION Porous metals with open cells have many potential applications in thermal management because of their huge internal surface area and high permeability for fluids. One such application is as heat exchangers in the cooling systems for electronic devices [1-3]. The cooling system is composed of the porous metal medium and a gas or liquid coolant flowing through its internal channels. Porous copper is an ideal medium for use as heat exchangers because of the high thermal conductivity of copper. At present most commercial porous copper used as heat exchangers is produced by powder metallurgy through sintering copper particles together without using any fillers. This conventionally particle-sintered porous copper usually has a low and narrow porosity range well below 50% [4-6]. The particle-sintered bronze samples [4] with porosities from 40% to 46% can enhance the heat transfer performance of the system up to 15 times for water and up to 30 times for air in comparison with an empty channel. The porous copper fabricated by investment casting or by the powder metallurgy using polymer fillers has a high and narrow porosity range over 80%. Several investigations [1, 7, 8] reported that an increase in either porosity or pore size generally reduced the heat transfer coefficient although pore size had much less effect than porosity. The porous copper samples with high porosities from 88% to 94% can enhance the heat transfer about 17 times in comparison with an empty channel. These porous copper samples showed heat transfer coefficients 2 to 3 times of those of the FeCrAlY and Al foams with a similar porosity and a similar coolant flow rate. Due to the limitations of the manufacturing methods, however, the current copper foams have a porosity either less than 50% or higher than 80%. The heat transfer performance of porous copper in the me
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