Toolthaisong, S., B. Kritacom, and S. Rampoepadongg. “The effect of the diameter ratios on the effectiveness of the concentric tube heat exchanger”. Engineering and Applied Science Research, vol. 38, no. 2, May 2012, pp. 139-46, https://ph01.tci-thaijo.org/index.php/easr/article/view/1605.