Heat transfer enhancement of a multichannel flat tube-copper foam latent heat storage unit

Abstract

In latent heat storage units, phase change materials are often combined with metal foams to enhance heat transfer due to their low thermal conductivity. However, the current metal foam structure cannot solve the problems of long melting time and uneven melting caused by natural convection. To obtain superior heat storage structures, this paper uses a multichannel flat tube as the heat exchange element and designs units with a variable volume ratio of gradient copper foam. This tube is divided into parts A and B and has a decreasing porosity along the vertical direction from top to bottom. Results of orthogonal tests show that low porosity, a large volume ratio of part A, and a large gradient can improve the performance. An average porosity of 0.84, gradient of 9%, and part A volume ratio of 80% are selected as the optimal structural parameters. Compared with a homogeneous porosity structure having a porosity of 0.96 under original working conditions, the optimal structure has 48.64% higher heat storage capacity and 54.13% shorter melting time. Meanwhile, compared with a homogeneous porosity structure having the same porosity of 0.84, the optimal structure has an 11.37% higher heat storage capacity and 4.09% shorter melting time.