Heat Transfer Characteristics of Longitudinal Perforated and Unperforated Ribs Under Impingement Jets

Impingement heat transfer is considered as heat transfer enhancement technique. Impinging jets are used in many applications where high heat transfer rates are required. An experimental study was conducted to investigate heat transfer under impingement of a multiple circular jet array with longitudinal perforated rib surfaces (LPRS) and longitudinal solid rib surfaces (LSRS). Heat transfer results were obtained using an infrared thermal imaging technique. The equipment for the experiments consist of blower, frequency controller, plenum section, impinging jet plate, Dantec 2D LDA system, 3-D traverse system, an infrared thermal imaging system, and LabVIEW software system. In order to generate the impinging jets, circular sharp-edged holes are used. A 3×5 array of jets is issued from the nozzles through the orifice plate. Fifteen in-line jet-nozzles are equally spaced over the orifice plate with the jet diameter (d) of 5mm. The impingement section is open on all four sides providing free outflow of the spent air. The heat transfer results of the rib surfaces are compared with those of a smooth plate. Best heat transfer performance was obtained with the LPRS arrangements.