Experimental investigations on heat transfer enhancement in a double pipe heat exchanger using hybrid nanofluids

Abstract Heat exchanger (HE) is an instrument that facilitates the operation of HE between two fluids that are at various temperatures. Double-pipe HEs are used in many organizations because of their low installation, design, maintenance costs, flexibility, and their suitability for high pressure applications. Heat transfer (HT) augmentation techniques (passive, active or compound techniques) are used in heat exchangers to reduce the HT surface area, to increase HT capacity and to reduce pumping power. Passive augmentation techniques are much cheaper and do not involve any external power input. They aim to improve the effective surface area, the residence time of the HT fluid and its thermal conductivity by the usage of nanofluids. Nanofluids are used for cooling applications in organizations, transportation, nuclear reactors, electrical and electronic devices and for biomedical applications. Hybrid nanofluids have higher thermal conductivity, low PD and frictional losses and pumping power as compared to the mono nanofluids. In this present work, experiments are conducted in a double pipe HE using TiO 2 , and SiC-water nanofluids by varying the volume concentration and cold fluid mass flow rate ranging from 17.5 to 34.5 lpm by making constant hot fluid mass flow rate. Further, experiments are conducted using TiO 2 –SiC/water hybrid nanofluids. Influence of nano and hybrid nanofluids on the overall HTC and friction factor are experimentally investigated. From the experiments, TiO 2 –SiC/water hybrid nanofluid with nanoparticle ratio TiO 2 :SiC = 1:2 is found to be optimum as the heat transfer enhancement is more with less improvement in friction factor. The overall heat transfer, and friction factor enhancement is 22.92 %, and 11.20 % higher respectively when compared with base fluid for TiO 2 :SiC = 1:2.