Enhanced Heat Transfer Performance of an Automobile Radiator With GNP/H2O-EG Nanofluids: Enhancement in Heat Transfer with Graphene Nanofluids

Radiators are used in automobiles to transfer heat from the engine coolant to ambient air. Despite the name, most radiators transfer bulk of their heat via convection. The demand to enhance the heat transfer rate can be addressed either by increasing the surface area or by increasing the convective heat transfer coefficient (CHTC). With regard to higher surface area many types of compact heat exchangers have been proposed. In order to increase the CHTC innovative heat transfer fluids are required in which conventional heat transfer fluids have lower thermal conductivity. In this regard, nanofluids show an enhanced thermal conductivity than that of the conventional heat transfer fluids which yields a higher CHTC. Over the past few decades, carbon based nano materials such as carbon nanotubes (CNTs), graphene nanoplatelets (GnP), graphene oxide, nano diamond were utilized in order to increase the thermal conductivity of conventional heat transfer fluids due to their high intrinsic thermal conductivity. Recently many research works have been performed with graphene based nanofluids due to its low interfacial thermal resistance and high aspect ratio resulting in higher thermal conductivity enhancement of nanofluids. The experiments on CHTC and overall heat transfer coefficient (OHTC) of an automobile radiator using various nanofluids as a coolant are reported by several researchers. Nowadays anti-freeze fluids (ethylene glycol and water-ethylene glycol mixture) are widely used in automobile radiators in order to avoid freezing during winter. The general recommendation is water-ethylene glycol mixture containing 30% (by volume) of ethylene glycol. In the present work, H2O-EG (70:30 by volume) seeded with GnP was used as the coolant. Few-layered GnP with an average thickness of 4–8 nm was selected due to the (1) high intrinsic thermal conductivity (2) high surface area (3) 2D structure (4) low interfacial thermal resistance (5) lower size nanoplatelets can carry more atoms in their surface which in turn higher heat transfer rate. This book will be useful for proposing the superior heat transfer fluids on automotive cooling applications.