In this paper a numerical investigation on laminar forced convection flow of a water-Al2O3 nanofluid in a rectangular microchannel, taking into account the viscous dissipation, is accomplished. A constant and uniform heat flux on the external surfaces has been applied and a single-phase model approach has been employed. The analysis has been performed in steady state regime for particle size in nanofluids equal to 38 nm. The CFD commercial code Ansys-Fluent has been employed in order to solve the 3-D numerical model. The geometrical configuration under consideration consists in a duct with a rectangular shaped crossing area. A steady laminar incompressible flow with viscous dissipation and different nanoparticle volume fractions has been considered. The base fluid is water and nanoparticles are made up of alumina (Al2O3). Thermo-physical properties of the nanofluid are considered constant with temperature. The length the edge and height of the duct are 0.030 m, 1.7 × 10−7 and 1.1 × 10−7 m, respectively. A constant and uniform heat flux q on the top wall is applied, the others are adiabatic and at the inlet section uniform temperature and velocity profiles are assumed. The results showed the increase of the convective heat transfer coefficients, in particular, for high concentration of nanoparticles and for increasing values of Reynolds number. However, the disadvantages are represented by the growth of the wall shear stress and the required pumping power, observed in particular, at high particle concentrations.
Natural convection flow from a horizontal circular cylinder with uniform heat flux in presence of heat generation
