Toolthaisong, Sarthit, Bundit Kritacom, and Sunchai Rampoepadongg. 2012. “The effect of the diameter ratios on the effectiveness of the concentric tube heat exchanger”. Engineering and Applied Science Research 38 (2):139-46. https://ph01.tci-thaijo.org/index.php/easr/article/view/1605.