Unsteady flow and heat transfer of pseudo-plastic nanoliquid in a finite thin film on a stretching surface with variable thermal conductivity and viscous dissipation

Abstract

This paper studies flow and heat transfer of pseudo-plastic nanoliquid in a finite thin film over an unsteady stretching surface with variable thermal conductivity and viscous dissipation effects. Four different types of nanoparticles, Cu, Al2O3, CuO and TiO2 are considered with sodium carboxymethyl cellulose (CMC)-water used as a base fluid. Unlike most classical works, a modified Fourier's law of heat conduction for power-law fluids is adopted by assuming that the thermal conductivity is power-law-dependent on the velocity gradient. Similarity transformations are applied to reduce the governing partial differential equations into a system of nonlinear ordinary differential equations, which are solved numerically by a shooting method coupled with Runge–Kutta method and BVP4C. The effects of solid volume fraction, types of nanoparticles, power-law index, unsteadiness parameter, modified Prandtl number and Eckert number on film thickness, velocity and temperature fields are graphically illustrated and discussed.