Heat transfer, fluid transport and mechanical properties of porous copper manufactured by lost carbonate sintering

Over the last few decades, porous metals have received a growing interest in industry due to their unique physical and structural properties and many potential applications ranging from light weight structure, filtration, energy and sound absorption to thermal management and electromagnetic shielding. In thermal applications, high energy consumption units demand higher and higher heat transfer performance. Porous copper is an ideal option for these applications due to its high specific strength, excellent thermal conductivity and high surface area. The Lost Carbonate Sintering (LCS) method is an efficient and simple manufacturing process to produce porous copper with a large range of porosity, various pore sizes and pore shapes. The main objective of this study is to investigate the heat transfer, fluid transport and mechanical properties of porous copper fabricated by the LCS method. The permeability, thermal conductivity, heat transfer coefficient and mechanical properties were studied on a number of porous metal specimens with different porosities/relative densities, copper particle sizes, pore sizes, pore shapes and combinatorial structures. A purpose-built apparatus was used to study the effects of pore structure on permeability. The results showed that pressure drop of LCS porous copper fits well with the Forchheimer-extended Darcy equation. The permeability increased with porosity and copper particle size, but decreased with pore size. The permeability can be predicted well using the modified Carman-Konezy relationship by introducing the tortuosity of LCS porous metal for both single and double layer structures. The thermal conductivity of LCS porous copper increased with relative density and pore size, but decreased with copper particle size. The thermal conductivity decreased with the size ratio between copper particle and pore at any given porosity. An empirical equation was established to describe for this relationship. Heat transfer coefficients were measured for a large number of samples. Compared with an empty channel, introducing a porous copper sample enhanced the heat transfer coefficient by a factor of 2–10. The samples with low porosities and large pore sizes showed high heat transfer coefficients. There was an optimal porosity range for good heat transfer performance at a given pore size. The heat transfer coefficient of LCS porous copper with double-layers was sensitive to the placement-order of the layer. A segment model was developed to predict the heat transfer coefficient of multilayer structures and the predictions agreed well with the experimental results. The mechanical properties of LCS porous copper fabricated with fine copper particles were studied by compression, bending and tensile tests. The mechanical strength and apparent modulus, decreased with porosity. The porous copper samples with large pore sizes had better mechanical performance. The extended Mori-Tanaka model was used to predict the modulus and the predictions agreed well with the experimental data