Numerical Study of the Effect of Hybrid Nanofluid Volume Fractions on the Thermal Hydraulic Efficiency of a Concentric Double Pipe Heat Exchanger

A key problem in sustainable thermal system design is to improve the efficiency of heat transfer. The application of nanofluids, especially the hybrid nanofluids has become a promising method of enhancing the performance of heat exchangers because of their great thermophysical characteristics. This paper has presented a numerical analysis to determine the rate of heat transfer, the overall heat transfer coefficient, and pressure drop of four hybrid nanofluids namely CNT-SiC/water, MgO-Fe3O4/water, Al2O3-TiO2/water and CuO-SiO2/water in the counter-flow concentric pipe heat exchanger in turbulent flow regime. The simulations were carried out with Reynolds numbers that ranged between 2000 and 15000 and volume fractions of 2, 4, and 6 percent.The findings show that Reynolds number and concentration of nanoparticles have a strong effect on thermal performance. The overall heat transfer coefficient of CNT-SiC/water, MgO-Fe3O4/water, CuO-SiO2/water and Al2O3-TiO2/water enhanced by 34.27, 30.66, 28.27 and 27.39 percent respectively than pure water at 6% of volume concentration. Accordingly, the rate of heat transfer was enhanced by 26.18%, 23.31%, 21.48%, and 20.85%. CNT-SiC/water hybrid nanofluids showed the most significant thermal enhancement among the considered fluids that were studied. The results confirm that hybrid nanofluids considerably enhance the heat transfer performance at the expense of increased pressure loss with a significant level of importance of thermal-hydraulic optimization in practice.