The effect of temperature-dependent viscosity on entropy generation in curved square microchannel

The effect of temperature-dependent viscosity on the thermodynamic performance of the curved square microchannel in laminar flow is numerically investigated in terms of entropy generation. The classical Navier–Stokes equations and constant wall temperature boundary conditions are adopted; aniline and ethylene glycol are selected as the working fluids. The results show that the Nusselt number, heat transfer entropy generation number and frictional entropy generation number are less for the temperature-dependent viscosity than for the constant viscosity when aniline is heated. However, the opposite conclusions can be drawn when aniline is cooled. The total entropy generation number extrema exist for the cases of aniline heated and cooled. The differences between the results obtained with and without considering temperature-dependent viscosity is more obvious when aniline is cooled than when aniline is heated. The difference between the Brinkman numbers obtained with and without considering temperature-dependent viscosity grows as the mass flow rate increases when ethylene glycol is heated. The temperature-dependent effect on entropy generation is more pronounced for ethylene glycol than for aniline, since the former has larger viscosity than the latter.

► Variable viscosity reduces irreversibilities when heating for most liquids.
► Variable viscosity enhances irreversibilities when cooling for most liquids.
► The total entropy generation number extrema exist for aniline.
► The extremum appears earlier when fluid is heated than when fluid is cooled.
► Variable viscosity weakens viscous heating effect when heating for most liquids.