Experimental study of a phase change thermal energy storage with copper foam

In this paper, a copper foam is implemented in a shell-and-tube heat exchanger as phase change thermal energy storage unit and studied experimentally. Visualization enables the melting/solidification front to be seen, followed and recorded. Bottom and top injection for charge and discharge are compared, vertically and horizontally. It appears that vertical charge and discharge are faster than horizontal ones and that top charge and discharge are faster than bottom ones, thus assessing the significance of volume expansion and natural convection for heat transfer in the phase change material. Moreover, the tested copper foam enhanced geometry is compared with other heat exchangers such as finned copper tube, tube surrounded by carbon foam and a simple tube. It is shown that copper foam combines low-density with high heat transfer performance since it is as efficient as copper fins with half the copper mass, and far more efficient than other presented heat exchangers. Besides, a method for estimating solidification and melting time is proposed. Based on a thermocouple network, this method rests upon measured temperatures inside the phase change material.