Abstract
The natural convection flow of water between two coaxial cylinders where the inner cylinder generates a constant heat source is numerically studied. The outer cylinder is cold while the top and bottom walls are thermally insulated. For a laminar flow and an inclination angle equal 0 degrees, 45 degrees, 90 degrees the results are determined in the form of contours of the isotherms and streamlines, average Nusselt number in the annular space. The results show that the average Nusselt number is growing with increasing Rayleigh numbers. The best heat transfer is obtained for the inclination angle 90 degrees.