Effect of tube material on convective heat transfer of various nanofluids

This work presents the convective heat transfer and friction loss characteristics of novel functionalized graphene-based and metal oxide nanofluids. The convective heat transfer in circular tubes of different materials (copper, aluminium and stainless steel 316) was used at constant wall heat flux of 23,870 W m(-2). An innovative approach was used to prepare highly dispersed propylene glycol-treated graphene nanoplatelets-water (GNP1) and trimethylolpropane tris amine-water (GNP2) by functionalization method. The measured thermal conductivity of GNP1 and GNP2 nanofluids showed incredible performance which increased up to 32% and 31% higher than that of basefluid. By comparing material effect, copper tube showed the highest HTC up to 119% in GNP1 at 0.1 mass%, while in aluminium and stainless steel 316 tube the highest heat transfer coefficient (HTC) was 110.2% and 100.68%. Besides, alumina and silicon dioxide nanofluids also presented decent increment in HTC which was up to 29.1% and 31.6%, respectively. The highest rise in friction factor for GNP1 and GNP2 was obtained up to 10.2% and 10%, respectively. For alumina and silicon dioxide nanofluids, the friction factor was measured up to 5.92% and 7.14% at velocity range of 1-3 m s(-1). The maximum enhancement in Nusselt number (Nu) for GNP, GNP2, alumina and silicon dioxide nanofluids was achieved up to 84%, 72%, 26% and 28%. The results suggest that the copper tube which is a good conductor of heat could be used in the heat exchangers and functionalized GNP nanofluids can be used as the heat exchanging fluids in heat transfer applications which could give a decent substitute to traditional working fluids in heat exchangers and in thermal fluid systems.