Mixed convection and entropy generation in a vertical annular space

Abstract

Present research efforts mainly focus on the nature of irreversibility, in terms of entropy generation, inside a vertical cylindrical annulus. Laminar mixed convective flow of a Newtonian fluid is considered. We seek for the closed form of analytical solutions by solving the simplified governing equations in cylindrical coordinates. Isothermal boundary condition is applied. Analytical expressions for the velocity and temperature are derived which essentially expedite to obtain expressions for local and average entropy generation in the annular space. Further ‘entropy generation minimization’ is applied to calculate the optimum radius ratio (Π_opt) as a function of group parameter ($\text{Br}\text{/Ω)}$ and the ratio of Grashof and Reynolds numbers (Gr/Re). Finally a correlation is proposed for calculating optimum radius ratio.