Numerical study on the thermal performance of the shell and tube heat exchanger using twisted tubes and Al2O3 nanoparticles

In the present study, the influence of twisted tubes and Al2O3 nanofluid on the thermal performance of the shell and tube heat exchanger is numerically studied. It employed computational fluid dynamics (CFD) with different turbulence models (realizable k-ε and realizable k-ε 2nd order). To verify the present solution, the results were compared with the published study in which the first-order realizable k–ε model was nominated as the acceptable method. In this study, mass flow rates ranging from 0.5 kg/s, 1 kg/s, and 2 kg/s were considered to investigate the thermal performance. Furthermore, pure water and the Al2O3 nanofluid 5%,10%, 15%, and 20% were used for twisted tubes, and only pure water was employed for smooth tubes heat exchangers with 6 baffles and without baffles. The results demonstrated using twisted tubes instead of smooth tubes, the coefficient of heat transfer increased by about 20%, but the pressure drop increased by about 14%. The results presented that the simultaneous use of 20% nanofluid and twisted tubes (instead of the pure water and smooth tubes with 6 baffles) leads to about an 8% increase in heat transfer coefficient and reduces the pressure drop by about 40%. Therefore, using nanofluids and twisted tubes can increase the thermal performance and reduce the economic costs of the pump compared to the old heat exchangers with various baffles.