Entropy analysis of unsteady magnetohydrodynamic thin liquid film flow of Maxwell nanofluids with variable fluid properties

Abstract

The flow and heat transfer phenomena of a viscous fluid in a thin film over an expanding flat surface possesses optimistic applications in a large number of technological processes. Heat and mass transfer rate within the thin film bears an unequivocal factors on the performance of coating process and the chemical nature of the product. This article concerns with the study of unsteady boundary layer magnetohydrodynamic thin film flow of Maxwell nanofluid past over an exponentially stretching surface subject to slip effect on velocity and suction/injection at the boundary. The heat transfer mechanism is influenced by the thermal radiation, temperature dependent thermal conductivity, viscous dissipation of energy and a non-uniform heat source/sink. We have analyzed the entropy generation of the system by paying due attention to the variable fluid properties and film thickness. The system of arising time dependent coupled nonlinear partial differential equations governing the fluid flow are converted into a system of ordinary differential equation by utilizing suitable self-similar transformations. The reduced two-point boundary value problem is then solved with the aid of well known Runge–Kutta–Fehlberg integration technique based shooting method. The mathematical model suggests an extra kinematic boundary condition which is utilized to compute the thickness of the thin film by employing the Newton–Raphson method. The investigation highlights that the arising controlling parameters such as magnetic parameter, radiation parameter, viscosity parameter, thermal conductivity parameter have strong effect on velocity field, temperature field, Nusselt number, and the thickness of the thin film. Moreover, the Bejan number, a measure of thermal irreversibility, is highly affected by the variation of the magnetic field strength, thermal radiation, dissipation of energy, thermal conductivity parameter, viscosity parameter and heat source/sink.