Entropy analysis for non-linear viscoelastic fluid in concentric rotating cylinders

An analytical solution is presented for the forced convection and entropy generation of a viscoelastic fluid obeying the Phan-Thien–Tanner (PTT) constitutive equation in a concentric annulus with relative rotation of the inner and outer cylinders. Two different types of boundary conditions are considered: at the first case both cylinders are isothermal and kept at different temperatures and in the second case the heat flux is kept constant at the outer cylinder and the inner one is isothermal. Analytical expressions for dimensionless temperature profile (Θ), dimensionless entropy generation number (NS), and the Bejan number (Be) are obtained. The effect of velocity ratio (β), the group parameter (Br/Ω), the Brinkman number (Br), and fluid elasticity () on the above parameters are investigated. The results show that the total entropy generation number decreases as the fluid elasticity increases. The results also show that entropy generation number increases with increasing Brinkman number.