Numerical heat transfer study in a round tube with inclined rectangular rings

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N. Koolnapadol
S. Sripattanapipat
S. Skullong
P. Wiriyavitsajjar
W. Thungwinyoo
C. Suppasubsiri


This paper deals with a numerical study on heat transfer and flow characteristics in a round tube inserted with inclined rectangular rings (IRR). The IRR elements at attack angle of 45 were mounted periodically into the test tube. Air was employed as the test fluid with Reynolds number from 3,000 to 18,000. The study reveals that the insertion of IRR elements can create two counter-rotating vortices along the tube that help increase the turbulence intensity apart from conveying the colder fluid from the core region to the heated-wall region. The IRR insert provides the high heat transfer and pressure drop increase than the smooth tube alone. Also, the tube fitted with IRR has considerably higher thermal performance than the smooth tube. The highest thermal performance for using the 45 IRR is found to be 2.12 at BR=0.2 and PR=0.5.


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Koolnapadol, N., Sripattanapipat, S., Skullong, S., Wiriyavitsajjar, P., Thungwinyoo, W., & Suppasubsiri, C. (2018). Numerical heat transfer study in a round tube with inclined rectangular rings. Journal of Research and Applications in Mechanical Engineering, 4(2), 183–191. Retrieved from


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