Thermal Mixing of Shear-Thinning and Newtonian Fluids in a T-Channel Using Impinging Streams

Abstract

AbstractIn this work, thermal mixing of shear-thinning (i.e. CMC solutions) and Newtonian fluids has been numerically investigated in a rectangular T-channel for a specified heat flux boundary condition at the mixing zone walls. The influence of the Reynolds number (10 ≤ Re ≤ 50), power-law index (0.6161 ≤ n ≤ 1), Nusselt number (a dimensionless form of convective heat transfer coefficient for external air flow, 103 ≤ Nuo ≤ 104), and ambient temperature (−2.7 ≤ θa ≤ 1.3) is studied on the mixing behaviour. The flow is assumed to be steady, laminar, and incompressible. The new results are presented in terms of isotherm contours, mixing index, and required channel length to achieve complete mixing. The mixing index decreases along channel length for both shear-thinning and Newtonian fluids. Better mixing is seen at high power-law index, ambient temperature, and Nusselt number and low Reynolds numbers. The length required to achieve the 95% of the ambient temperature or the exact ambient temperature is shorter for mildly shear-thinning fluids (high power-law index) and Nusselt number, and low Reynolds numbers. Also, for the case of heating (high ambient temperature), the complete mixing demands a shorter channel length than that in the case of cooling.KeywordsMixing characteristicsAmbient temperatureNusselt numberChannel lengthDegree of mixing