A comprehensive review on convective heat transfer of nanofluids in porous media: Energy-related and thermohydraulic characteristics

Abstract

Convective heat transfer is one of the most important mechanisms of heat exchange in many of industrial devices, which covers a major part of energy-related topics. With providing large surface areas as well as intensification of flow mixing, porous media can enhance convective heat transfer in different applications. On the other hand, suspensions containing nanoparticles (i.e., nanofluids) considerably improve the thermal conductivity of liquids. Consequently, employing both nanofluids and porous materials can significantly increase the performance of various thermal equipment. In this article, the studies carried out on convection heat transfer of nanofluids in the problems involving porous media are reviewed. In this regard, three different convective heat transfer processes including natural, forced, and mixed convection mechanisms, are considered. In many of the geometries, an optimum nanoparticle concentration is observed in thermal systems. In three types of convection heat transfer, Nusselt number is enhanced by the increase of the Darcy number. In the free and mixed convection processes, the increment of the buoyancy force often reduces the heat transfer rate. In the natural convection, the Nusselt number has a reverse relationship to the porosity. In the case of using nanofluids in porous media, most of the studies have employed numerical or analytical approaches, and experimental investigations in this area are very sparse. In addition to studying the behavior of nanofluids in porous media, various flow regime models and heat transfer mechanisms are studied individually, which is missed in the open literature.