Iranian Journal of Chemical Engineering (IJChE)

Abstract In this paper, three-dimensional incompressible laminar fluid flow in a rectangular microchannel heat sink (MCHS) using Al2O3/water nanofluid as a cooling fluid is numerically studied. CFD prediction of fluid flow and forced convection heat transfer properties of nanofluid using single-phase and two-phase model (Eulerian-Eulerian approach) are compared. Hydraulic and thermal performance of microchannels are investigated according to the results of the friction factor, pumping power, average heat transfer coefficient, thermal resistance, average temperature of the walls and entropy generation. In addition, due to the CFD results, two correlations for predication of Nusselt number and friction factor are presented. Comparing the predicted Nusselt number using single-phase and two-phase models with experimental data shows that the two-phase model is more accurate than single-phase model. The results show that increasing the volume fraction of nanoparticles leads to increases the heat transfer coefficient and reduces the heat sink wall temperature, but it leads to the undesirable effect of increase in pumping power and total entropy generation.

Abstract In this study, forced convection heat transfer of non-Newtonian nanofluids in a horizontal tube with constant wall temperature under turbulent flow conditions was investigated using computational fluid dynamics tools. For this purpose, non-Newtonian nanofluids containing three types of nanoparticles (Al2O 3, TiO 2 and CuO) with carboxymethylcellulose aqueous solution as a liquid single phase with three average particle sizes of 10, 25 and 40 nm nanofluids were investigated. Effects of nanoparticle type and Peclet number on the convective heat transfer coefficient were investigated in fully turbulent region of a horizontal tube. A correlated equation was obtained for Nusselt number using the dimensionless numbers by applying the simulation results. Results showed that the correlated data were in very good agreement with the experimental ones obtained from the literature. The maximum error was 12%.

Abstract In the current study, numerical simulation of laminar flow and heat transfer of water mixture with carbon nanotubes (CNT) as nanofluids in a 90 degree curved pipe are considered. The incompressible Navier-Stokes and energy equations are solved numerically in a body fitted coordinates system using a control volume technique. An interfacial layer-based model is applied to predict the thermal conductivity of nanofluid. The axial velocity contours, secondary flow patterns and temperature fields for different values of the particles concentrations are examined in detail. Furthermore, the effects of nanoparticles concentration on the heat transfer are studied. The results indicate that due to the secondary flows induced by curvature effects, the heat transfer rate is improved, and enhanced remarkably further using nanofluids. Furthermore, the nanoparticles, especially at higher concentration levels, generate more uniform cross sectional temperature distributions.