Koolnapadol, N., S. Sripattanapipat, S. Skullong, P. Wiriyavitsajjar, W. Thungwinyoo, and C. Suppasubsiri. 2018. “Numerical heat transfer study in a round tube with inclined rectangular rings”. Journal of Research and Applications in Mechanical Engineering 4 (2):183-91. https://ph01.tci-thaijo.org/index.php/jrame/article/view/138662.