Double-diffusive laminar natural convection and entropy generation of Carreau fluid in a heated enclosure with an inner circular cold cylinder (Part II: Entropy generation)

In this paper, entropy generation of double-diffusive natural convection, studying Soret and Dufour effects and viscous dissipation in a heated enclosure with an inner cold cylinder filled with non-Newtonian Carreau fluid has been simulated by Finite Difference Lattice Boltzmann Method (FDLBM). This study has been conducted for certain pertinent parameters of Rayleigh number (Ra = 10 ⁴ and 10 ⁵), Carreau number (Cu = 1, 10, and 20), Lewis number (Le = 2.5, 5 and 10), Dufour parameter (D _f = 0, 1, and 5), Soret parameter (S _r = 0, 1, and 5), Eckert number (Ec = 0, 1, and 10), the Buoyancy ratio (N = −1, 0.1, 1), the radius of the inner cylinder (R _d = 0.1 L, 0.2 L, 0.3 L, and 0.4 L), the horizontal distance of the circular cylinder from the center of the enclosure (Ω = −0.2 L, 0 and 0.2 L), the vertical distance of the circular cylinder from the center of the enclosure (δ = −0.2 L, 0 and 0.2 L). Results indicate that the augmentation of Rayleigh number enhances different entropy generations and declines the average Bejan number. The increase in the power-law index provokes various irreversibilities to drop significantly. The rise of Soret and Dufour parameters enhance the entropy generations due to heat transfer and fluid friction. The rise of Eckert number enhances the summation entropy generations. The increase in Lewis number augments the total summation entropy generations gradually. The enhancement of the buoyancy ratio causes the summation entropy generations to increase considerably. The rise of Carreau number declines the total entropy generation gradually. The least value of the total entropy generation in the vertical position of the cylinder occurs at δ = −0.2 L. The increase in the size of the cylinder augments the total entropy generation substantially. The minimum values of the total entropy generations are observed in the center position (δ = 0) in different horizontal positions.