FLOW AND HEAT-TRANSFER TO A CIRCULAR-CYLINDER WITH A HOT IMPINGING AIR-JET

A study has been made of the flow and heat transfer to a circular cylinder from a hot impinging air jet. The problem is of fundamental interest and also has important applications; e.g. in respect to the outside vapor deposition process. Numerical solutions of the governing conservation equations have been obtained utilizing a non-orthogonal curvilinear coordinate grid. The effects of the Reynolds and Grashof numbers on the flow and heat transfer, as well as those of the wall temperature, the jet. width, and the distance between the nozzle and the cylinder have beeen investigated and correlation curves are presented. The flow is stable and symmetric over the range of parameters studied. The interaction of the buoyant impinging jet with the cylinder as well as with the surroundings makes the flow and heat transfer to the cylinder quite different from that for uniform flow. The effects of buoyancy, diffusion and cooling of the jet ahead of the cylinder, the development of the wall jet, and the recirculating bubble all affect the flow and heat transfer. The average Nusselt number increases with increasing Reynolds and Grashof numbers and narrow banded correlation curves are obtained by introducing an effective Reynolds number, which includes a buoyancy contribution. The width of the jet and the distance between the nozzle and the cylinder have a strong effect on the heat transfer.