Implication of fluid rheology on the hydrothermal and entropy generation characteristics for mixed convective flow in a backward facing step channel with baffle

Abstract

The present study numerically investigates a two-dimensional, steady, laminar, incompressible and mixed convective flow of non-Newtonian fluid through a backward facing step channel with different baffle configurations. The power-law model is used to capture the confluence of fluid rheology and buoyancy for varying step to baffle distance, varying number of baffles and different arrangement (inline and staggered) of baffles. Different values of power-law index viz. n = 0.5, 0.8, 1, 1.2 and 1.5 are considered to encompass the shear-thinning (n < 1), shear-thickening (n > 1) as well as Newtonian fluids (n = 1) as a special case. The Reynolds number is fixed equal to 100 whereas the Richardson number has been varied within the range of 0.1–1 in the present investigation. The results obtained from the present investigation reveal the implications of power-law index, Richardson number and baffle configuration on the reattachment length, Nusselt number, pressure drop and entropy generation. The results show that the length of the recirculation zones formed in the backward facing step channel increases with increase in Richardson number and decreases with increase in power-law index. It is also found that the variation of heat transfer rate, pressure drop and entropy generation characteristics for varying step to baffle distance, different number of baffles and different arrangement and number of pairs of baffle is dictated by the interplay of power-law index and Richardson number. The findings of this study bear utility towards designing efficient thermodynamic system that can deliver maximum heat transfer with minimum irreversibility.