A theoretical model on the effective stagnant thermal conductivity of an adsorbent embedded with a highly thermal conductive material

Abstract

The effective stagnant thermal conductivity of an adsorbent bed plays an important role in the system performance of adsorption cooling systems and other applications. It is proposed that embedding the adsorbent with a highly thermal conductive material by forming a coating layer on the adsorbent molecules could increase the overall heat transfer rate resulting in a higher COP and SCP. A theoretical model based on the area-contact approach was developed in this study to predict the effective stagnant thermal conductivity of a surface coated porous material. This modified area-contact model can also be employed in different applications where surface coated porous materials are used. It was found that the coating layer thickness, c, the solid/fluid thermal conductivity ratio, λ, and the porosity, α, are factors that can affect the effective stagnant thermal conductivity. When λ = 103, the effective stagnant thermal conductivity was improved by about 4.3 times for α = 0.4 and 9.7 times for α = 0.8 with a deformed factor, α = 0.002 and a coating layer thickness, c = 0.05. An FEM simulation model was built showing that the modified area contact model has better agreement with the simulation result than the area contact model. It is suggested that this modified area contact model can be applied to predict the effective stagnant thermal conductivity of a surface coated porous material. © 2013 Elsevier Ltd. All rights reserved.