Entropy-energy analysis of forced convection in a porous-saturated circular tube considering temperature-dependent viscosity effects

The temperature-dependent viscosity effect on forced convection in a circular tube filled with a porous medium is investigated theoretically. The Darcy flow model is employed and the viscosity-temperature behaviour is described by an inverse-linear model. It is found that the effect of the variation impacts the Nusselt number significantly while the pressure drop was not influenced that much. Expressions for the entropy generation, Bejan number, heat transfer irreversibility, and fluid flow irreversibility are presented in terms of the Brinkman number, the Peclet number, the viscosity variation number, and the dimensionless heat flux