Heat Transfer Enhancement Inside Elliptic Tube by Means of Rings Inserts

Heat transfer, friction factor and enhancement efficiency characteristics in an elliptic tube fitted with elliptic rings have been investigated experimentally.  In the experiments, air was used as the tested fluid with a Reynolds number range of 10000 to 32464. The experimental results show a considerable increase in friction factor and heat transfer over the plain tube under the same operation conditions. Over the range investigated, the Nusselt numbers for both employed enhancement devices with different pitches are found to be higher than that of the plain tube. It was found that the best overall enhancement was achieved with pitch = 3d. The results obtained are correlated in the form of Nusselt number and friction factor as a function of Reynolds number and pitches. The results were compared with circular tubes have the same test conditions to show the difference between the circular and elliptic tubes. Key words : Heat transfer enhancement; Elliptic tube