A doctoral thesis at the College of Engineering was conducted in a theoretical and experimental study of a heat pipe complex using phase-changing materials for graduate student Raed Saad Odeh. It was studied with the evacuated glass tube solar collector model with the use of a water storage tank in addition to paraffin wax containers, which represent the inner surface of the water tank, which is in contact with the surface of the containers. The phase changing material (BCM) can be used for heat storage, and the study was conducted in various cases with and without wax, with and without heat loads.