Gilani, S., H. Al-Kayiem, and D. Woldemicheal. “Effect of Conical Pin Arrangement on Heat Transfer Efficiency of a Free Convective Solar Air Heater”. Journal of Mechanical Engineering and Sciences, vol. 10, no. 2, Sept. 2016, pp. 2053-64, doi:10.15282/jmes.10.2.2016.10.0194.