A numerical study of entropy generation in radiative Casson nanofluid flow

Abstract

Abstract In this study, we investigate entropy generation in a Casson nanofluid flow over a moving wedge. The system is subjected to radiation‐conduction interaction while the fluid transport properties are variable. In some earlier studies, fluid transport properties like viscosity and thermal conductivity, if not constant, depended on the fluid temperature. However, in this study, we assume fluid transport properties that depend on the nanoparticle volume fraction. In addition, we assume free nanoparticle movement and thermophoretic diffusion at the concentration boundary. We linearize the transport equations, and solve using a spectral collocation technique. We present an analysis of the accuracy and convergence rate of the method and give a comparison with earlier studies. The impact of some parameters on entropy generation, drag coefficient, heat, and mass transport is discussed. The study shows, among other results, that irreversibility due to heat transfer is a potent factor in the entropy generation rate. An increase in the variable viscosity increases fluid motion and species concentration but reduces the fluid temperature. The variable thermal conductivity parameter reduces the temperature profiles, but the variable mass diffusivity leads to an increase in the nanoparticle concentration profiles. Here, we assume linear variable transport properties that are dependent on the nanoparticle concentration. Future extensions could, for example, focus on exponential variable transport properties, with nanoparticle concentration‐dependence.

Keywords

• Brownian motion
• entropy generation
• radiation‐conduction interaction
• spectral local linearization method
• thermophoresis
• variable viscosity