Irreversibility Distribution Ratio Used in Entropy Generation Equation for Convective Flows Re-visited

Abstract

The present numerical investigation describes a new consistent and accurate approach to the square cavity benchmark problems for computing entropy generation during natural or mixed convection flows. This new approach differs from the classic one in that the irreversibility distribution ratio in the dimensionless entropy generation equation is no longer arbitrarily chosen, as reported in the majority of previous research works, which is a very serious violation of the scientific rules but is precisely calculated. Indeed, the computation of the exact value of the irreversibility distribution ratio is based on two indispensable features. One concerns the thermophysical properties of the working fluid at a fixed Prandtl number or at a given reference temperature and the other concerns a reference length of the geometrical configuration considered, depending on the Rayleigh number. Comparing results indicates that the irreversibility distribution ratio, more frequently used by a significant number of researchers, is usually vastly overestimated which will involve an increase in entropy generation and, consequently, an expensive oversizing in all real processes involving flowing fluids.