Effect of Finite Width on Heat Transfer and Fluid Flow about an Inclined Rectangular Plate

Abstract

Wind tunnel experiments were performed to study the heat transfer and fluid flow characteristics for finite-width rectangular plates inclined at various angles of attack to an oncoming airflow. Plates having ratios of spanwise width to streamwise length of 0.4 and 2.5 were employed, and the angle of attack was varied from 90 deg (normal incidence) to 25 deg. The Reynolds number range extended from about 20,000 to 90,000. The naphthalene sublimation technique was used in the transfer coefficient determinations, and the fluid flow patterns adjacent to the plate were made visible by the oil/lampblack technique. The flow field was found to be highly complex and three dimensional, with stronger three-dimensional effects in evidence for the narrow plate. A stagnation zone, centered in the plate cross section at normal incidence, moved forward and ultimately disappeared as the plate was inclined at smaller angles of attack. The dimensionless heat (mass) transfer coefficient, expressed in terms of the Colburn j-factor, varied as the square root of the Reynolds number for all angles of attack, both for the narrow and the wider plates. For the wider plate, the transfer coefficients are completely independent of the angle of attack in the range investigated, while for the narrow plate there is an overall variation of twenty percent. An algebraically simple correlation of all the results, accurate to ± 10 percent, is given to facilitate their use in applications such as the wind-related heat loss from flat plate solar collectors.