Experimental study on heat transfer, entropy generation, and exergy destruction of Ag, MWCNT, and GO water-based nanofluids in helical tubes

Abstract

Heat transfer convection, pressure loss, and entropy generation analysis for nanofluid flow through helical tubes are experimentally investigated. A test setup was fabricated, and three types of nanofluid, including silver (Ag), multi-walled carbon nanotube (MWCNT), and graphene oxide (GO), were prepared. Experiments were carried out in the laminar regime through four helically coiled tubes, while uniform heat flux was applied on the wall surface. The results show that Ag nanoparticles improve thermal conductivity and heat transfer coefficient between 8 and 25%, MWCNT/water enhances the heat transfer rate up to 10%, but GO nanoplates decrease heat transfer rate. Comparing entropy generation and exergy destruction for water and nanofluids reveals that utilizing nanoparticles of Ag and MWCNT reduces entropy production and exergy loss due to better thermal performance, but GO/water increases entropy production because of lower thermal conductivity compared to water. Maximum reduction in non-dimensional total entropy generation around 15% was achieved for Ag/water nanofluid. Variation of entropy generation due to heat transfer and fluid friction in addition to Bejan number and non-dimensional total entropy generation for water and nanofluids is discussed in detail.