TRANSIENT NATURAL-CONVECTION OVER A HEAT GENERATING VERTICAL CYLINDER

A numerical solution for the transient natural convection over heat generating vertical cylinders of various thermal capacities and radii is presented. A fully implicit finite difference technique is used to solve the non-linear set of equations. The rate of propagation of the leading edge effect is given special consideration. It is found that this rate, predicted by the one-dimensional conduction solution, is slower than that resulting from the boundary layer solution. Also, it increases as the radius and thermal capacity of the cylinder decrease, and as the surface heat flux increases. The transient boundary layer thickness is found to exceed its steady-state value while the transient average heat transfer coefficient is found to reach a minimum, as low as 53% of its steady-state value for the highest value of the modified Grashof number studied. Excellent agreement with previous experimental steady-state data as well as with one-dimensional theoretical results is obtained.