Search

In this study, effect of viscous dissipation on entropy generation for fully developed incompressible laminar flow mixed convection in vertical parallel-plate channels with asymmetric and symmetric uniform heat fluxes was parametrically analysed. Analytical equations were derived by using continuum approach and perturbation method. A specific MATLAB code was created to solve the governing equations. The effects of Gr/Re, the Brinkman number, and the ratio of wall heat flux on the entropy generation are presented and discussed. It is concluded that viscous dissipation has a significant effect on the entropy generation for mixed convection in heated vertical parallel-plate channels. Entropy generation resulting from fluid friction goes up, however, entropy generation due to heat transfer decreases by increasing of viscous dissipation. Consequently, it can be said that, this study will contribute to literature in optimising the systems that operates under mixed convection conditions in the vertical parallel-plate configuration.

This paper presents a parametric study on the exergetic performance assessment of an electrolyte supported solid oxide fuel cell (SOFC) stack. Considering the operating and design parameters of yttria stabilised zirconia (YSZ) electrolyte supported SOFC stack, the variations of overpotentials, the rational overpotentials and the exergetic efficiencies are investigated for comparison purposes. Consequently, considering the selected operating conditions and design parameters, it is suggested that the YSZ electrolyte supported SOFC stack having higher exergetic efficiency than 30% is used. Moreover, in order to operate such a fuel cell in an exergetically more efficient manner, the minimum YSZ electrolyte thickness needs to be thicker than 150 μm. Otherwise, some durability and manufacture problems may occur. However, a decrease of operating temperatures from 1273 K to 1073 K and an increase of YSZ electrolyte thickness from 150 μm to 500 μm will result in a reduced exergetic efficiency.