Heat transfer and entropy generation analysis of internal flow of nanorefrigerant with slip condition at wall

Abstract

Heat transfer enhancement has always been the main purpose in designing the heat exchangers in various industrial applications. In addition, nanofluids have shown potential as industrial cooling fluids due to the enhanced heat transfer characteristics particularly in heat exchanger applications. Whilst enhancing heat transfer using nanofluids, there is a trade-off of causing higher irreversibility and pressure drop. Therefore, in order to have a better view of thermal performances, it is necessary to consider other aspects of the thermal system in addition to heat transfer factors such as pressure drop and entropy generation. In the present study, the heat transfer characteristics and entropy generation analysis of a laminar nanofluid flow in a 3 mm horizontal circular tube subjected to a uniform heat flux and slip boundary condition is evaluated numerically using ANSYS Fluent software. Two types of nanofluids that are obtained from dispersing of Al2O3 and SiO2 nanoparticles in pure HFE7000 are considered with particle volumetric concentrations of 0, 1, 4 and 6% and Reynolds numbers of 400, 800, 1200 and 1600. Results indicate that mean pressure drop reduces about 25% by using the slip boundary condition at the wall. In addition, while using a slipping wall pipe with slip length of 100 µm and 6% volume concentration of Al2O3 dispersed in HFE7000, total entropy generation decreases about 20% in comparison to pure HFE7000 flowing in a no-slip pipe.