CYLINDER MOVING IN PRESSURE-INDUCED AND BUOYANCY-INDUCED CHANNEL FLOW- A NUMERICAL STUDY OF TRANSPORT DUE TO 3 AIDING OPPOSING MECHANISMS/

The flow and heat transfer associated with the convective cooling of a heated cylinder moving in a channel with buoyancy- and pressure-induc ed flow has been numerically investigated. Three distinct transport me chanisms arise in this case due to material motion, forced flow, and b uoyancy. Considered in this study are uniform flows at the inlet of th e cooling channel in the same, as well as in Be opposite, direction as the movement of the cylindrical rod. This problem is of interest in s everal manufacturing processes such as hot rolling, continuous casting , extrusion, wire drawing, and glass fiber drawing. The transport proc esses are time dependent at the initial stages, following the onset of motion, and usually attain steady state conditions at large time. The temperature distribution in the solid is of particular interest in ma terials processing. A detailed numerical study is carried out, assumin g an axisymmetric, transient circumstance with laminar flow. The gover ning full, elliptic equations are solved, employing the finite volume method. The conjugate problem, coupling the transport in the solid mat erial with that in the fluid, is solved. The effect of thermal buoyanc y on tire heat transfer and on the flow for different orientations is studied in detail. Of particular interest is the numerical imposition of the boundary conditions. Not much work has been done in this regard with the combined effects of material motion, buoyancy, and forced fl ow present. When the flow opposes the movement of the rod, either due to pressure-induced flow or due to buoyancy, a recirculating region ar ises near the rod surface. This recirculation region plays a major rol e in the heat transfer and thus affects the resulting temperature deca y in the moving rod. Validation of the numerical results is carried ou t by comparisons with earlier experimental results, indicating fairly good agreement.