COMPUTATIONAL STUDY OF LAMINAR HEAT-TRANSFER DOWNSTREAM OF A BACKWARD-FACING STEP

Laminar heat transfer in a separating and reattaching flow was numerically studied by simulating the flow and heat transfer downstream of a backward-facing step. A series of computations was conducted in which three principal parameters governing the heat transfer in this geometry (i.e. channel expansion ratio ER, Reynolds number Re and Prandtl number Pr) were systematically changed. As a result, detailed relations between these parameters and the fundamental heat transfer characteristics have been elucidated. Some important findings are: (1) the distribution of the local Nusselt number depends strongly on all of these parameters; (2) the peak of the local Nusselt number does not necessarily locate at or very near the point of flow reattachment, in contrast to the common belief; and (3) if the Prandtl number is considerably low, the peak itself does not even appear and hence the heat transfer enhancement, usually assumed around the flow reattachment point, can never be expected in such cases.