Numerical Study of a Concentric Tube Heat Exchanger Using Dimpled Tubes with Al2o3 NanoFluid

Abstract

The heat exchanger device such as concentric tube heat exchanger faces challenges to obtain the best thermal performance of heat exchanger devices plays important role in the performance of cooling system. The conventional coolant offer low thermal conductivity. The numerical study of dimpled tube with Nanofluids is important to improve the thermal performance system in heat exchange. In the present work, a concentric tube heat exchanger has been numerically modeled for heat transfer and a pressure drop characteristic under different flow rates are investigated. Reynolds numbers for the inner tube ranged from 1000 to 5000. The overall heat transfers were calculated in parallel heat exchanger. CFD Analyses were carried out with flue gas in the annulus side and Al2O3 Nanofluid in the inner tube side. The three-dimensional governing equations for momentum, continuity, and heat transfer were solved using a finite volume based computational fluid dynamics (CFD) code. The numerical results indicated that the Nusselt number for the spherical dimpled tube and ellipsoidal dimpled tube are 35.7% and 63.59% higher than that for the smooth tube in same Reynolds number. The friction factors in the dimpled tube increase by 52.7% and 87.27% for ellipsoidal and spherical dimples compared to the smooth tube. Heat transfer rate of spherical dimpled tube with Al2O3 Nanofluid is 40% better than in the plain tube and ellipsoidal dimpled tube with Al2O3 Nanofluid is 46% better than in the plain tube with Al2O3 nanofluid. Thus, the ellipsoidal dimpled tube could enhance heat transfer more efficiently than smooth and spherical dimpled tube with Al2O3 Nanofluid.