Forced convection on solar collector arrays

Experiments were performed in a wind tunnel to determine the local and average heat transfer coefficients for forced convection of air over an array of three inclined rectangular plates. In addition to the measurement of heat transfer coefficients, flow visualization by the use of tufts was done to survey the nature and direction of the flow at the surface of the plates. The local Reynolds number ranged from 5500 to 750,000 and the Reynolds number based on the length of the plate ranged from 480,000 to 850,000. Three angles of attack (30, 45, and 60 deg) and two inter-plate distances between adjacent plates were investigated at zero yaw angle for each of the three plates positioned in the array. The aspect ratio of each plate was 1:1.19. The convection heat transfer coefficient was determined at 25 different locations on the surface of each plate by using an electrically-heated surface probe built for that purpose. The experimental precision in measuring h is within + or - 2%. The local convective heat transfer coefficients obtained were also integrated over the area of the plate to yield average values.