EXPERIMENTAL STUDY ON HEAT STORAGE AND RELEASE OF EG/Li2CO3-Na2CO3 HIGH-TEMPERATURE PHASE-CHANGE HEAT STORAGE UNIT

In this paper, a shell-and-tube high-temperature phase-change heat storage unit used in solar high-temperature phase-change heat storage systems was designed and manufactured by using 5:95 expanded graphite EG/Li₂CO₃-Na₂CO₃ as heat storage medium. The temperature distribution, heat exchange efficiency, and energy efficiency of the heat storage unit were studied by testing the heat storage and heat release processes. It was found that a thermostatic platform appeared in the lateral temperature distribution, and a distinct layered distribution appeared in the longitudinal temperature distribution. When the heating power of the heat storage unit is 640 W, the exothermic air flow rate is 400 L/min, and the phase change material was completely melted, the total heat storage and latent heat of the phase change material are 12,321 kJ and 4466 kJ, respectively. The proportion of the latent heat was 0.36, heat storage efficiency and heat release efficiency are 0.57 and 0.47, respectively. In addition, it was also found from the experiment that the greater the heating power, the higher the heat storage efficiency of the heat storage unit, and the greater the heat release air flow, the higher the heat release efficiency.