The hydrothermal performance of non-Newtonian fluids in superhydrophobic microchannels

Abstract

Investigating the thermal performance of non-Newtonian fluids is of great importance as these fluids are ubiquitous in industry. In this regard, we perform a series of numerical simulations to investigate the effect of superhydrophobic microstructures in a microchannel containing Newtonian, shear-thinning, and shear-thickening fluids on their hydrothermal performances. To this end, three different cases are considered. In the first case, the upper wall is subjected to various heat fluxes and temperatures in the range of 104-106 W/m2 and 303.15-323.15 K, respectively. In the second case, the working fluid's Reynolds number varies while the upper wall's thermal condition is fixed. In the last case, the temperature of the computational zone is set to a constant value. As the air pockets are absent near the upper wall, the thermal energy is transferred without any loss, increasing the working fluid's temperature and, consequently, plummeting the viscosity and resulting in smaller shear stresses. It is revealed that this channel can reduce the pressure drop up to 31.9% and 29.9% for constant heat flux and constant temperature conditions, respectively. The higher the Reynolds number, the lesser the drag reduction performance. The rise in the computational zone's temperature can profoundly improve the pressure drop plummeting performance. For all cases, the recirculation of the air within the bottom surface features is responsible for slip velocity and smaller shear stress at the bottom wall. The results show that the overall performance of the proposed channel is better than the smooth one.