Theoretical and experimental advances on heat transfer and flow characteristics of metal foams

Open cell metal foam can be applied to greatly improve thermal performance of heat sink and heat exchanger,so that it has been widely used in the fields of thermal(or heat)control system of aerospace vehicle and energy utilization system and become a very important topic for research in the aerospace thermophysics field,and more and more attentions have been attracted.The optimal design of metal foam heat transfer devices is based on the understanding the flow and heat transfer characteristics in metal foam.This article reviews some recent progresses of theoretical and experimental researches on heat transfer enhancement and flow characteristics of metal foam.We found that the pore cell simplification models of metal foams generally fall into four categories,among which the most commonly used cell model is Kelivin model.Some exploratory works performed by the current authors are also introduced,such as the effect of boundary conditions on the heat transfer enhancement;the theoretical modelling of interfacial convective heat transfer taking into account heat conduction between foam ligaments;and the flow characteristics under relatively high velocity.The analytical results show that the flow characteristics of metal foam at relatively high speed are completely different from those at low speed,a further thorough study of the heat transfer and flow characteristics of metal foam is necessarily required.In this paper,two types of partial filling techniques are discussed.The heat transfer performance of partially filled tubes was evaluated by both the performance evaluation criteria and the performance evaluation plot of enhanced heat transfer techniques oriented for energy-saving.The results show that the filling type of metal foam have a significant impact on its heat transfer enhancement performance.Therefore,the filling method of metal foam should be further studied,in order to optimize the thermophysical properties of heat transfer devices.