Mahdi M, Gaddoa A. Outdoor Testing of a Zig-Zag Solar Air heater with and without Artificial Roughness on Absorber Plate. Eng. J. [انترنت]. 12019 [وثق 302019];25(4):1-7. Available from: http://joe.uobaghdad.edu.iq/index.php/main/article/view/j.eng.2019.04.01