Entropy analysis with the Cattaneo-Christov heat flux model for the Powell-Eyring nanofluid flow over a stretching surface

The recent trend of research in fluids' transport along with heat transfer processes is focused on entropy minimization in thermal systems. This leads to the introduction of nanofluids as operating fluids, use of non-Newtonian fluid models, the type, shape, and sizes of nanoparticles, and the effect of variable thermophysical properties. In the present research, a numerical investigation is carried out for the entropy generation in a time-dependent, thermodynamically stable Powell-Eyring nanofluid flow over a flat, porous and nonlinear horizontal stretching surface. The Cattaneo-Christov model for the heat flux is assumed for the thermal boundary layer analysis. The effects of the uniform thermal radiation, nanoparticle's shape and the boundary slip is also included in the mathematical model. The governing equations a re abridged under the assumptions of the usual boundary layer flow and the Roseland approximations. Partial differential equations are first transformed to a system of ordinary differential equations by using appropriate similarity transformations. The Keller box scheme is then adopted to find the approximate solutions for the reduced ordinary differential equations. Two different classes of nanofluids, copper-water (Cu-H2O) and titanium-water (TiO2-H2O) are considered for our analysis. Numerical results are presented graphically to study the effect of various thermophysical parameters. Numerical results show material parameters, velocity slip, nanoparticle concentration and fluid injection increase the thermal boundary layer thickness and reduce the rate of heat transfer at the surface. Moreover, increasing the strength of these reduces fluid movement within the boundary layer and increases the overall entropy of the system.