Entropy Generation Analysis of Open Parallel Microchannels Embedded Within a Permeable Continuous Moving Surface: Application to Magnetohydrodynamics (MHD)

Abstract

This paper presents a new design of open parallel microchannels embedded within a permeable continuous moving surface due to reduction of exergy losses in magnetohydrodynamic (MHD) flow at a prescribed surface temperature (PST). The entropy generation number is formulated by an integral of the local rate of entropy generation along the width of the surface based on an equal number of microchannels and no-slip gaps interspersed between those microchannels. The velocity, the temperature, the velocity gradient and the temperature gradient adjacent to the wall are substituted into this equation resulting from the momentum and energy equations obtained numerically by an explicit Runge-Kutta (4, 5) formula, the Dormand-Prince pair and shooting method. The entropy generation number, as well as the Bejan number, for various values of the involved parameters of the problem are also presented and discussed in detail.

Heat transfer and second law analyses of forced convection in a channel partially filled by porous media and featuring internal heat sources

“…(25a, b and c) would decrease the mathematical complexity of the model and could be used in this work similar to Refs. [51][52][53]. However, to predict the local and total entropy generation rates more accurately, the local temperature is used in the denominator of these equations.…”

“…When Be is less than 1 2 and approaches to zero, the irreversibility due to the viscous effects dominates the processes and if 1 2 Be = the entropy generation due to the viscous effects and the heat transfer effects are equal [53].…”

Reducing Entropy Generation in MHD Fluid Flow over Open Parallel Microchannels Embedded in a Micropatterned Permeable Surface

“…Moreover, a no-slip condition is applied between open microchannels, whereas a slip condition is applied to the open parallel microchannels. Thus, in the present micropatterned surface design, based on EBSM techniques of gas or liquid flow [7,8,25,27], the slip boundary condition is applied inside the open microchannels. Experimental evidence recommends that, for water flowing through a microchannel, the surface of which is coated with a 2.3 nm thick monolayer of hydrophobic octadecyltrichlorosilane, an apparent hydrodynamic slip is measured just above the solid surface.…”

“…Recently, the use of open microchannels instead of the usual closed microchannels has been recommended, since the open microchannels are open to the ambient air on the top side, which can offer advantages, such as maintaining the physiological conditions for normal cell growth and introducing accurate amounts of chemical and biological materials [6,7]. Taking advantages of microfabrication techniques due to making appropriate slip boundary condition along hydrophobic open microchannels together with biotechnological application areas of open microchannels motivates us to consider carefully a practical design for controlling the entropy production of various microscale systems in a MHD flow field.…”

“…In another study, they [29] have analysed the second law analysis of MHD flow over embedded microchannels in an impermeable surface. Recently, Yazdi et al [7] have investigated entropy generation analysis of electrically conducting fluid flow over open parallel microchannels embedded within a continuous moving surface in the presence of applied magnetic field where the free stream velocity was stationary and the fluid was moving by an external surface force.…”