EXPERIMENTAL AND COMPUTATIONAL STUDY OF HEAT TRANSFER FROM THE REAR AND FRONT OF BLUNT MOVING BODIES

Abstract

The flow behind and in front of blunt bodies is a very important field of investigations. The heat transfer from rear and front of these bodies has not been widely investigated, in spite of its important applications, which include many of the present world interests. The present experimental and computational work has been carried out to. study the effect of air-stream velocity, blockage ratio and body length (in direction of fluid flow) on heat transfer from the rear and front of these bodies to the flowing air around them. A test rig and eight different models have been designed and constructed for the experimental work. The test rig consists of a centrifugal air blower fitted with a variable opening gate, honeycombs, working section, orifice meter and measuring devices. The wind tunnel (6 pieces) is a horizontal rectangular duct having the same cross-section as that of the blower outlet. The working section, which contains the test model, is the fourth piece of the main duct. The eight test models have different dimensions and similar construction. Each test model consists of a heating brass plate, main heater, guard heater, asbestos insulation and wooden frame. The heating plate is a rectangular plate of 5 mm thickness and its height and width were chosen according to the considered blockage ratio. It is provided with 23 copper-constantan thermocouples for measuring the temperature distribution on its surface. To prevent heat losses from the back of the main heater, a similar heater is used as guard heater. Four pairs of thermocouples are placed and embedded in the insulation between the heaters to balance the heat flow between them. To minimize the heat loss from the brass plate and the ma in heater edges, a tape of asbestos is used to surround them. There are twelve thermocouples used to calculate this heat loss.