Thermal Mixing of Impinging Laminar Streams of Shear-Thinning Fluids

Abstract

Thermal mixing behavior of shear-thinning fluids with the specified heat flux boundary condition at mixing zone walls is studied numerically to investigate the effect of Reynolds number (10 to 50), power-law index (0.6161 to 1), Nusselt number (10⁴ to 10⁶) for external air flows and dimensionless ambient temperature (?2.7 to 1.3). The temperature is a passive tracer that quantifies the degree of mixing in this study. Detailed kinematics shows the formation of recirculation zones at the mixing channel walls. Length required to achieve the well mixed condition (i.e., a flat temperature profile across the channel height) is shorter at low Reynolds number, convective heat transfer coefficient and ambient temperature, and high power-law index values. In the impingement zone, a faster reduction in mixing index has been observed with respect to mixing length at high power-law index and low Reynolds numbers, while Nusselt number and ambient temperature exert only a weak influence. Under appropriate conditions, significant energy exchange between the system and surroundings can occur and has been analyzed in detail in this work. This work finds its applications in the improved mixing as practiced in the processing and production of food-stuffs, fine chemicals, personal care products, etc.