EXPERIMENTAL STUDY OF HEAT TRANSFER ENHANCEMENT WITH A SINGLE INCLINED PERFORATED OBSTACLE IN A RECTANGULAR CHANNEL

Measurements were carried out to investigate the enhancement in the heat transfer and the influence of flow friction in a rectangular channel using a single inclind perforated obstacle (baffle) affixed on the bottom surface which was heated with a uniform heat flux. A horizontal rectangular channel with an aspect ratio, hight/width, of 1:5 was examined. The obstacle was attached to the heated surface and properly aligned in the favorable direction of the flow. Both solid (witout perforation) and perforated obstacles were used. The effects of perforation, obstacle length, and gap between obstacle and upper surface were studied. The open-area ratio (3) of 0, 0.023, 0.038, 0.115, and 0.167 were investigated and Reynolds number ranged from 15000 to 45000. The experiments covered a range of obstacle length to the height ratio (UH) from 2.0 to 6.0, and gap to channel height ratio (B/H) from 0.3 to 0.7. Inclined perforated obstacle combines three major heat transfer techniques, e.g. boundary layer separation, internal flow swirls, and jet impingement. The result showed that the maximum heat transfer enhancement and friction factor were about 3.7 and 11.0 times more than that smooth channel, respectively, and these of values were achieved using obstacle with (3 = 0.023, UH = 2.0, and B/H= 0.3. The greatest efficiency index was found for the obstacle with 13 = 0.167, L/H=6.0, and B/H = 0.7, where, a maximum efficiency index of about 1.6 was found. New correlation were obtained for the influence of the parameters on both Nusselt number enhancement and flow friction factor ratios.