Experimental investigation of the performance of graphene nanoplatelet (GNP)-CUO/distilled water hybrid nano fluid in concentric tube and plate heat exchangers

The use of nanofluids as a working fluid is one of the preferred methods to improve the performance of heat transfer in heat exchangers used in many different applications today. This study, in which a hybrid nanofluid consisting of hybrid graphene nanoplate copper oxide (GNP-CuO) and pure water was used, was carried out in concentric tube and plate heat exchangers. Experiments in the concentric tube heat exchanger were carried out in parallel and in counter flow. In these experiments, the thermal performance of the hybrid nano fluid has been experimentally investigated. During the preparation of the hybrid nanofluid, a two-stage method was applied. GNP and CuO nanoparticles were used at a rate of 0.5% by volume, and sodium dodecyl benzene sulfonate was used as a surfactant at a rate of 0.05%. It is aimed to increase the stability of the nanofluid and to prevent the precipitation of nanoparticles with surfactant. As a result of the experiments performed at different hot fluid flow rates in a concentric tube heat exchanger, an average of 5.5% increase in parallel flow and an average of 13.7% increase in counterflow was achieved for the total heat transfer coefficient. As a result of the experiment performed at different cold fluid outlet temperatures in the plate heat exchanger, an average increase of 16.7% was achieved for the total heat transfer coefficient. With these results, it was found that the hybrid nanofluid consisting of GNP + CuO / pure water has a higher heat transfer coefficient than conventional working fluids and can be preferred for improving the thermal performance of heat exchangers.