Effect of eccentricity and radius ratio on fluid flow and heat transfer inside an eccentric semicircular enclosure

The problem of laminar natural convective heat transfer inside an eccentric semicircular enclosure of different radius ratio and eccentricity is investigated numerically. At the same time, combined effect of the radius ratio and eccentricity on fluid flow is also observed with isothermal upper and lower surface. Here laminar, steady natural convection heat transfer are predicted for radius ratio R*=1.75, 2.0, 2.25, 2.5. Simulation was carried out for a range of eccentricity, ɛ=0.0 to 0.6. Governing equations are solved using finite volume method with a body fitted grid with collocated variable arrangement for a range of Grashof number 10¹–10⁷ based on R ₀. Results are presented in the form of constant stream function, isothermal lines, local Nusselt number and average Nusselt number at different angular position. Eccentricity has little dominance on heat transfer rate. But significant effect of eccentricity is observed on flow field. Radius ratio has significant effect on natural convection heat transfer as well as on flow field. At higher eccentricity, bi-cellular flow is observed with one crescent-shape vortex at narrower cross section. This crescent shaped vortex is broken down into two cells with the increase of radius ratio that means transition Grashof number for bi-cellular flow to tri-cellular flow is decreased with the increase of radius ratio. Eccentricity also has the same effect on flow field. Eccentricity has little effect on heat transfer but with the increase of radius ratio, average heat transfer rate increases.