Slaiman, Qasim J. M., and Abbas N. Znad. “Enhancement of Heat Transfer in The Tube-Sid of A Double Pipe Heat Exchanger by Wire Coils”. Nahrain University College of Engineering Journal, vol. 16, no. 1, June 2017, pp. 51-57, https://oldjournal.eng.nahrainuniv.edu.iq/index.php/main/article/view/237.