Thermal performance of tube exchanger enhanced with hexagonal ring turbulators

Heat transfer and fluid flow characteristics in a round tube fitted with Hexagonal ring turbulators were studied. Hexagonal ring turbulators with the different inner diameters (diameter ratio 0.6, 0.7 and 0.8) and Pitch Diameter Ratio of 1, 2 and 3 were used as flow blockage geometry. Parameters varied during the tests were diameter ratio, Pitch Diameter Ratio, and Reynolds number. Air with ambient temperature was used as a working fluid in a test tube in which the inner wall is maintained at uniform heat flux. The Reynolds number was varied from 6,000 to 24,000. Use of Hexagonal ring turbulator as turbulator significantly enhances the heat transfer from the heated wall of the tube to air across the test section. Among the tested inserts, insert with Hexagonal Ring Turbulator (diameter ratio 0.6 and Pitch Diameter Ratio 1) achieve maximum heat transfer rate at higher Reynolds number and friction factor at lower Reynolds number which is at 3.01 times and 32.7 times of those compared to the smooth tube respectively. Insert with HRT (diameter ratio 0.8 and PDR 1) offers the highest overall performance factor (1.34) at lower Reynolds number.