Enhancement of the heat transfer performance of a double-pipe heat exchangers in various configurations using Al2O3 nanofluid: A focused review

Double-pipe heat exchangers (DPHXs) are employed in many industrial, sanitary, and food applications, which make this heat exchanger the attention focus of many researchers and developers to enhance its thermal performance. Techniques that are either passive or active, and occasionally both, are used to improve thermal performance. Because of their superior thermophysical qualities, one method to improve thermal performance is to use nanofluids rather than traditional fluids. An extensive and targeted study of the application of AlO3 nanofluid in the DPHX in its several configurations is given in this paper. Furthermore, all of the mathematical and correlational equations needed to assess the parameters of DPHXs for counterflow and parallel flow are provided in this article, as well as an overview of nanofluids, methods of preparing them, calculating their thermophysical properties, and factors affecting their performance. The results of this review showed that Al2O3 nanofluid works well to improve heat transfer in DPHXs, and the enhancement increases if it is used with other enhancement methods such as fins, despite the pressure loss increasing as a result of friction with the tube surface. Finally, compared with other metal oxide nanofluids under similar conditions, in other words, Al2O3 nanofluid showed superiority over all types except CuO nanofluid. This review focuses on Al2O3 nanofluid, making it a valuable reference for those interested in using this nanofluid as mono or hybrid in tubular heat exchangers.