Thermal performance assessment of alumina/graphene oxide hybrid nanofluid in annular passage of multiple configurations

The current study investigated the effect of both the intrinsic and extrinsic parameters of annular flow on the thermal performance of alumina/graphene oxide (Al₂O₃/GO) for fully developed turbulent flow by A 3-D CFD model. A fully circular annular pipe (the cross-section is a full circle for both the outer pipe and inner rod) and an annular pipe with a diamond-shaped inner rod were considered in the study. An aqua-based hybrid nanofluid containing Al₂O₃: GO nanocomposite of 80%: 20% mass mixing ratio, respectively, was tested in comparison with the distilled water (DW) as a heat transfer fluid in both annular passages. The hybrid nanofluid of volumetric concentrations 0.1%, 0.3%, 0.5%, and 0.75% was selected from a published work, and its density and specific heat were calculated theoretically by the current research. The effect of heating location on thermal performance was investigated by alternating a uniform heat flux boundary at the inner rod and outer pipe. The CFD model was verified experimentally using a DW run experiment with a fully circular annular pipe with inner heating under a Reynolds number range between 3000 and 8500. The results generally concluded that the annular pipe with a diamond-shaped inner rod has a higher shape performance index than the fully circular annular pipe, and the inner heating has a higher heat transfer coefficient than that of the outer heating for all nanofluid concentrations in both pipe configurations.