Numerical Analysis on Nanofluid Mixed Convection in Triangular Ducts Heated by a Constant Heat Flux

Abstract

The enhancement of heat transfer represents a very important issue regarding several industrial heating or cooling equipments. This goal can be achieved by means of different techniques; for example, by adopting passive methods like changing flow geometries or by enhancing the thermal conductivity of the working fluids. Thus, an innovative way of improving the thermal conductivity of base fluids consists into introduce suspended small solid nanoparticles. In this paper a numerical investigation on laminar mixed convection with Al2O3/water based nanofluids in a triangular channel is presented. Duct surfaces were heated by means of a constant and uniform heat flux. The analysis was performed in laminar steady state regime for particle size in nanofluids equal to 38 nm, by adopting a single-phase model approach. The base fluid was water and alumina (Al2O3) nanoparticles were dispersed at different concentrations. Different Richardson number values were considered in order to solve a 3-D model of triangular duct. Results are presented for the fully developed regime flow in terms of surface shear stress and heat transfer convective coefficient, Nusselt number and required pumping power profiles. Comparisons with results related to the fluid dynamic and thermal behaviors are carried out in order to evaluate the enhancement due to the presence of nanoparticles in terms of volumetric concentration. The increase of average convective heat transfer coefficients and Nusselt number values for increasing values of Richardson number and particle concentration is observed by analyzing the obtained results. However, also wall shear stress and required pumping power profiles increase as expected.