NATURAL CONVECTIVE HEAT TRANSFER FROM AN INCLINED ISOTHERMAL SQUARE CYLINDER WITH AN EXPOSED TOP SURFACE MOUNTED ON A FLAT ADIABATIC BASE

Natural convective heat transfer from an isothermal inclined cylinder with a square cross-section and which has an exposed top surface and is, in general, at an angle to the vertical has been numerically studied. The cylinder is mounted on a flat adiabatic base plate, the cylinder being normal to the base plate. The situation considered is an approximate model of that which occurs in some electrical and electronic component cooling problems. The flow has been assumed to be steady and laminar and it has been assumed that the fluid properties are constant except for the density change with temperature which gives rise to the buoyancy forces, this having been treated by using the Boussinesq approach. The solution has been obtained by numerically solving the governing equations, these equations being written in terms of dimensionless variables using the height, h, of the cylinder as the length scale and T-w - T-F as the temperature scale, T-F being the undisturbed fluid temperature far from the cylinder and T-w being the uniform surface temperature of the cylinder. These dimensionless governing equations subject to the boundary conditions have been solved using the commercial cfd solver, FLUENT. The flow has been assumed to be symmetrical about the vertical center-plane through the cylinder. The solution has been used to derive the values of the mean Nusselt number for the cylinder, Nu. The solution has the following parameters: the Rayleigh number, Ra, the dimensionless cylinder width, i.e., the ratio of the width to the height of the heated cylinder, W = w/h, the Prandtl number, Pr and the angle of inclination of the cylinder relative to the vertical, phi. Results have only been obtained for Pr = 0.7. Values of phi between 0 degrees and 180 degrees and a wide range of Ra and W have been considered. The effects of Ra, and phi on the mean Nusselt number, Nu, for the entire cylinder and for the mean Nusselt numbers for the various surfaces that make up the cylinder have been examined.