Heat transfer analysis of CuO-ZnO/water hybrid nanofluid in a Shell and tube heat exchanger with various tube shapes

Abstract

Heat exchangers are widely used in various applications, including heating and cooling systems. Adding nanoparticles to the base working fluid can enhance the fluid's thermophysical properties, thereby increasing the thermal performance of heat exchangers. Further heat transfer enhancement can be done by using a hybrid nanofluid, which contains two or more different nanoparticles. The findings of the paper can be utilized to enhance the thermal efficiency of a shell and tube heat exchanger with different tube shapes and by using CuO-ZnO/ water hybrid nanofluid as a working fluid. Numerical simulations were conducted to model thermal heat exchangers with different configurations. Copper tubes of circular, hexagonal, and elliptical geometry were considered for the experiment. The model is solved using Ansys software with a finite volume approach. The solver employs an upwind-based multidimensional linear approach and upwind discretization schemes. The water inlet velocity in the Shell ranges from 0.5m/sec to 3.2 m/sec at a Reynold number of 10,000 to 15,000 whereas the velocity of cold fluid in the tube varies from 1.4 to 2 m/sec. All experiments were conducted with a 0.01–0.1 %vol % CuO-ZnO (80:20)/ water hybrid nanofluid. The hybrid nanofluid on the tube side is used to cool hot fluid (water) on the shell side. Hybrid nanofluid inlet temperature was maintained at 30°C to cool hot water at 60°C. Hexagonal tube geometry increases the contact surface area, resulting in a 22.11 % increase in heat transfer rate compared to round tubes and an 18.42 % increase compared to round tubes. Experimental and numerical results for the convective heat transfer coefficient, Nusselt number, and pressure drop were also reported.