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Numerical Study of Flow and Heat Transfer with ZnO-Water Nanofluid in Flattened Tubes

Abstract The usage of nanofluids and modification of tube geometry are the two most prominent heat transfer enhancement methods employed to improve the performance of thermal devices. In this work, the combined effect of these methods has been studied by CFD modelling of developing and Graetz laminar flow in flattened tubes with ZnO – water nanofluid. For the purpose of comparison, simulation with water and circular tube has also been carried out. Performance evaluation has been done using PEC, PER and entropy generation. Results reveal that tube flattening has more pronounced effect on both heat transfer and flow compared to that of nanofluid. An optimum tube flattening in terms of aspect ratio and nanofluid concentration has also been identified for this kind of flow. Flattened tube with aspect ratio 6 with 1 % ZnO-water nanofluid has been found to yield the highest entropy generation reduction of 13.24 %