Effect of powder shape on effective thermal conductivity of Cu–Ni porous coatings

Abstract

Porous coat is a kind of increasing heat transfer coatings based on increasing surface area and bubble nucleation. Several properties of the porous coat, including effective thermal conductivity (ETC) and porosity are influential design factors in determining the high heat flux performance. There are many factors which affect the mentioned properties and powder shape is the most important parameter. The aim of this study is to investigate the effect of powder shape and its surface roughness on thermal conductivity of Cu–Ni sintered porous coatings with three porosity levels (20, 30 and 40%). The porous samples were prepared by powder metallurgy technique in reduction atmosphere. It was found that at constant porosity, spherical powder with smooth surface and narrow range pore size distribution has higher ETC, on the other hand, irregular-jagged powder with wide range pore size distribution has lower ETC. The experimental results show that ETC values increased from 7 to 14% by increasing porosity level from 20 to 40%. Surface roughness affected ETC more than powder shape.