Non-isothermal laminar flow and heat transfer between disks corotating in a fixed enclosure

This is a numerical investigation of the coupled laminar flow and heat tran sfer in the space between a pair of disks attached to a hub rotating about a vertical axis in a fixed cylindrical enclosure, A temperature variation i s imposed in the fluid by setting the disks at different uniform temperatur es, the temperature of the bottom disk being higher than that of the top di sk. The Boussinesq approximation is used to characterize buoyancy forces in the momentum conservation equations. The different types of interdisk flow that arise as a function of angular v elocity are described. At low Reynolds numbers the flow is primarily driven by gravity-induced buoyancy. As the Reynolds number increases, free convec tion yields to centrifugally-induced buoyancy. At sufficiently high Reynold s numbers, convection patterns induced by the strong shear at the enclosure wall dominate the interdisk flow and heat transfer but centrifugal buoyanc y continues to influence the 3-D flow structure with respect to the isother mal case. One of the effects of buoyancy is the appearance of a new transit ion in the bifurcation diagram previously investigated by the authors for t he isothermal flow case. Here, centrifugal buoyancy favors the generation o f a 3-D flow which features a strong breaking of its symmetry properties wi th respect to the interdisk midplane, as in the isothermal case. Heat transfer rates are calculated for a range of Reynolds numbers and inte rdisk spacings. Special attention is paid to the high Reynolds number force d convection regime which is of practical interest. It is shown that the sc ales derived from heat and mass transfer analyses of the freely rotating di sk apply to the present problem. In many of the present cases, 2-D (axisymm etric) and 3-D calculations yield very similar values for the overall heat transfer rates. This is especially the case for those flows with a wavy 3-D structure, meaning flows which, on average, are symmetrical with respect t o the interdisk midplane. However, examples are also provided where the flo w is strongly 3-D, requiring computationally intensive calculations to obta in accurate predictions of the corresponding heat transfer rates. (C) 1999 Elsevier Science Ltd. All rights reserved.