Entropy generation in a variable viscosity channel flow of nanofluids with convective cooling

The present work investigates the combined effects of thermophoresis, Brownian motion and variable viscosity on entropy generation in an unsteady flow of water-based nanofluids confined between two parallel plates with convective heat exchange with the ambient surrounding at the walls. Both first and second laws of thermodynamics are applied to analyse the problem. The nonlinear governing equations of continuity, momentum, energy, and nanoparticles concentration are tackled numerically using a semi-discretisation finite-difference method together with a Runge–Kutta–Fehlberg integration scheme. Numerical results for velocity, temperature, and nanoparticles concentration profiles are obtained and utilised to compute the skin friction, the Nusselt number, the entropy generation rate, the irreversibility ratio, and the Bejan number. Pertinent results are displayed graphically and discussed quantitatively.