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The present communication deals the entropy generation by cause of heat and mass transform in an unsteady mixed convective radiative squeezing flow of a Casson fluid confined between two parallel disks in the presence of diffusion‐thermo and thermal‐diffusion effects and temperature jump. The lower disk is taken to be porous and the upper one is impermeable. The governing PDE is converted as nonlinear ordinary differential equations (ODE) by using well‐established similarity transformations; then, the reduced nonlinear ODE are solved by shooting method with Runge‐Kutta fourth‐order approach. The influence of distinct nondimensional fluid and geometric‐related parameters on the velocity profiles, temperature, concentration, entropy generation number, and Bejan number are studied in detail and represented in the form of graphs. The entropy of the Casson fluid is increased with the Eckert number, whereas the concentration profile is decreased by squeezing Reynolds number. The current results are correlated with existing results for the viscous case and found to be in better agreement.

The effect of sensible heating of the phase‐change material (PCM) before melting and subcooling after solidification, on the performance of the latent heat storage system (LHSS), is studied in terms of first‐ and second‐law efficiencies for the overall charge–discharge cycle. The external heat transfer irreversibilities on account of the interaction between the heat transfer fluid and the storage element are characterized and the optimum phase‐change temperature for maximum second‐law efficiency is studied. The performance of the LHSS operation is assessed with and without sensible heating before melting and subcooling after solidification. It is observed that the optimum phase‐change temperature is higher, and, the overall second‐law efficiency is greater for LHSS with sensible heating and subcooling beyond a certain phase‐change temperature compared to latent heat storage alone. In addition, the first‐law overall efficiency is found to exhibit a minimum and a pre‐heated discharge stream is shown to result in a substantial improvement of the second‐law efficiency. © 1998 John Wiley & Sons, Ltd.

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The present article deals the entropy generation due to heat and mass transfer of an unsteady MHD flow of a Casson fluid squeezed between two parallel disks. The upper disk is taken to be impermeable and the lower one is porous. The flow field equations are reduced to non-linear ordinary differential equations by using similarity transformations and the resulting ODE problem is solved by shooting technique with Runge-Kutta 4thorder method. The effects of various non dimensional fluid and geometric parameters on the velocity components, temperature, concentration, entropy generation number, Bejan number, skin friction and Nusselt number are illustrated through graphs and tables. It is noticed that the temperature of the fluid is enhanced with Eckert number, whereas the concentration of the fluid decreased with Casson fluid parameter. The present study is applicable to nuclear engineering cooling systems, wire and blade coating, extrusion of polymer fluids, optical fibers, magnetohydrodynamics and optimization of chemical engineering processes.

In this article, we performed the entropy generation of free convective chemically reacting second‐grade fluid confined between parallel plates in the influence of the Hall and Ion slip with heat and mass fluxes. Let there be a periodic suction/injection along with the plates, the governing flow field equations are reduced as a set of coupled nonlinear ordinary differential equations by using appropriate similarity transformations then solved numerically with shooting method based on Runge‐Kutta 4th order scheme. The results are analyzed for velocity in axial and radial directions, temperature distribution, concentration distribution, entropy generation number, Bejan number, mass and heat transfer rates with respect to distinct geometric, and fluid parameters and shown graphically and tables. It is observed that the entropy generation is enhanced with Prandtl number, whereas decreases with a second‐grade parameter, the effects of Hall and Ion slip parameters on velocity components, temperature and entropy generation number are the same. The entropy generation number the fluid is enhanced with the suction‐injection parameter whereas, the concentration of the fluid decreases with the increasing of chemical reaction parameter.

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