Effects of Secondary Flows on the Convective Heat Transfer from a Heated Block inan Airstream

摘要

A detailed investigation into the secondary flow effects on the convective heattransfer from a heated, low profile, block in an airstream is presented. The block surfaces are heated by driving a direct current though stainless steel strips, adhered in a series circuit configuration on the block's surfaces. Measurements of the temperature distributions, on the front, top, rear, and lateral block surfaces, are taken via an automated data acquisition system equipped with 79 resistive type temperature sensors. The temperature sensors are installed between the stainless steel strips and the block substrate material. From the temperature measurements, local surface coefficient of heat transfer values are reduced, by performing an energy balance on a small region of stainless steel in the vicinity of each sensor. An overall, three-dimensional, convection heat transfer description for the block, at a Reynold's number (based on the block height) of approximately 21000 is presented. Also investigated are the heat transfer effects produced by varying freestream flow Reynold's number and average Grashof number. Further elaborating the flow field conditions present on the block's cover surface, flow visualization studies, using a modified ink-dot and oil of wintergreen method, are conducted. These studies are performed at freestream flow Reynold's numbers of 15000, 22000, 33000, and 51000.