Prediction of effective thermal conductivity of coated metals foams using cubic unit cell

Abstract

Metal foam material draws many designers’ attention due to its excellent thermomechanical properties. Coating foam with higher conductive material can enhance those properties. The coating technique is a critical process to attain an optimum foam. The aim of this study is to develop a mathematical model to predict the effective thermal conductivity of the coated metal foam. A spherical geometry which is equivalent to cubic unit cell for foam structure was considered to have more accurate values. The dimensions of the geometry were normalized to represent the effective thermal conductivity. The foam material was carbon and the coating material was copper which has better thermal conductivity than carbon. Coating thickness layer was increased incrementally for each step by adding 5 µm. Average volume technique was adopted and the cubic unit cell was divided into three layers. The effective thermal conductivity of each layer was calculated using the series law of thermal resistance. As the coated thickness increases, the porosity decreases and the thermal conductivity increases. By decreasing the porosity from 97% to 46%, the effective thermal conductivity increases from 6 W/m.K to 176 W/m.K. The result from this study was compared to experimental data from previous study and a very good agreement was achieved. This model can be used to predict the effective thermal conductivity of any foam material coated with any other material as long as the properties of the foam and the coated material are known.