Experimental Study on the Effect of Insertion of Copper Lessing Rings in Phase Change Material (PCM) on the Performance of Thermal Energy Storage Unit. alkej [Internet]. 2015 Dec. 31 [cited 2025 Apr. 30];11(4):60-72. Available from: https://www.alkej.uobaghdad.edu.iq/index.php/alkej/article/view/265