Numerical Study on Thermal and Fluid Dynamic Behavior of Confined Impinging Slot Jets with Nanofluids in Partially Filled Configuration of Metal Foam

Abstract

In this work a numerical analysis on confined slot impinging jets constituted by a partially filled configuration of metal foam in mixed convection is illustrated. The employed working fluids are pure water or Al2O3/water based nanofluids A two-dimensional model is constructed and several Peclet numbers (equal to 100, 200, 350, 750, 1500) are assumed. Rayleigh numbers is fixed equal to 30000. The nanoparticle volume concentrations are in a range from 0% to 4% and the nanoparticle diameter is considered equal to 30nm. The target surface is characterized by a constant temperature, evaluated according to the value of Rayleigh number. The distance of the target surface is five times greater than the slot jet width. Three different values of ratio between the total system and the metal foam length have been assumed. The thermal and fluid-dynamic properties of nanofluids are estimated by a single-phase model approach. The model of local thermal non equilibrium (LTNE) is assumed in order to replicate the behavior of the metal foam characterized by a number of pores per inch (PPI) equal to 20 and a porosity of 0.9005. Results show increasing values of the convective heat transfer coefficients for increasing values of Peclet number and nanoparticle concentration. This behaviour is more evident at low Peclet number values. In conclusion, the ratio between the thermal and pumping power is calculated in order to find a trade-off between the increase of heat transfer and pressure drop.