Numerical simulation of nanofluid turbulent flow in a double-pipe heat exchanger equipped with circular fins

Abstract

In this study, the thermal and flow characteristics of a nanofluid were evaluated numerically in a circular finned double-pipe heat exchanger. A 3D CFD model was employed to study the effects of nanofluid properties and fin configuration on the friction coefficient, Nu number and thermal performance. The effects of Al2O3 nanoparticles at the volume concentration of 1–2% were considered for both Newtonian and non-Newtonian turbulent flow in the annulus side with an insulated outer surface and constant heat flux inner tube. A numerical analysis is conducted for different values of Re numbers of 5000–100,000, fin heights (1, 2 and 3 mm) and fin pitches (80, 160 and 320 mm). The results showed that the use of circular fin increases the heat transfer 36% and 30% for Newtonian and non-Newtonian nanofluid, respectively. The Nu number was increased by enhancing Al2O3 volume concentration and Re number. A thermal performance evaluation was carried out to study the conflict between heat transfer and pressure drop. Although the simultaneous use of the fins and nanoparticles improves the thermal behavior of Newtonian fluid but decreases the thermal performance for non-Newtonian fluid due to a penalty in pressure drop. Therefore, in this research adding nanoparticles to non-Newtonian fluid is suggested without any inserts in the annulus.