Forced Convection Heat Transfer at an Inclined and Yawed Square Plate—Application to Solar Collectors

Abstract

Experiments have been performed to determine the average heat transfer coefficients for forced convection airflow over a square plate that is inclined and yawed relative to the oncoming flow. The experiments involved mass transfer and were carried out via the naphthalene sublimation technique, with air as the working fluid. By means of the analogy between heat and mass transfer, the results are presented in a form that can be used directly for heat transfer applications. The experiments encompassed a wide range of angles of yaw and angles of attack, and extended over a Reynolds number range from about 20,000 to 100,000. It was found that owing to three dimensional flow effects, the transfer coefficients were remarkably insensitive to both the angle of attack and the angle of yaw. This enabled all the results to be correlated by the equation j = 0.931Re−1/2 (where j = (h/ρcpU∞)Pr2/3) with an accuracy of ±2 1/2 percent. The correlation equation was applied to the determination of the heat transfer coefficient for wind-related heat losses from a flat plate solar collector. It was demonstrated that the currently standard computational equation (which is, in reality, not well suited to the application) substantially overestimates the heat transfer coefficient.