EXPERIMENTAL STUDY OF HEAT TRANSFER CONTROL AROUND AN OBSTACLE BY USING A RIB

Abstract

This paper investigates the effect of the presence of a rib on the end-wall heat transfer of an obstacle by liquid crystal thermography. An obstacle with a rectangular cross section is placed in a rectangular channel and blocks the entire height of it (AR = 4). A rib with a square cross section is placed at two positions, i.e., in the upstream and downstream areas of the obstacle, respectively. An important parameter in dealing with the control of heat transfer around an obstacle using a rib is the spacing between them. The spacing S, normalized by the spanwise width of the obstacle, has the values 1.25 and 0.625. The effect of the rib height, normalized by the channel hydraulic diameter, e/Dh, is also investigated by considering two values of it, i.e., 0.078 and 0.039, respectively. The results show that the local heat transfer especially in the upstream region of the obstacle is substantially modified by the upstream rib, e/Dh and S/d. The local heat transfer in the downstream region is more affected by the rib height, e/Dh. The local heat transfer in the upstream area of the obstacle is found nearly unaffected by the downstream rib regardless of the rib height e/Dh and S/d. It is found that the local heat transfer in the downstream area of the obstacle is modified differently and it is strongly affected by the rib height e/Dh and S/d. The heat transfer pattern due to the flow reattachment in the downstream area is significantly modified by the rib height e/Dh. The area influenced by the enhancement is found to be more affected by S/d. A larger enhancement area reflected a stronger impact associated with the heat transfer mechanism for e/Dh = 0.078. (Less)