Experimental investigation on the heat transfer enhancement in a novel latent heat thermal storage equipment

Latent heat thermal energy storage (LHTES) is a potential and promising technology for efficient utilization of renewable energy. In order to achieve efficient heat storage and release capacity, a novel and compact LHTES equipment which is integrated with several parallel U-tube rectangular heat storage units (HSUs) has been developed and investigated experimentally. The thermal storage equipment developed here can be applied in many areas such as low-temperature waste heat recovery, solar heat utilization, agricultural green house heating, etc. Filled with modified paraffin enhanced by large porosity copper foam in the HSUs in the LHTES equipment, the maximum heat storage capacity and rate reached 1.907 MJ and 198.7 W respectively when the inlet temperature of heat transfer fluid (HTF) was set to be 85 °C. In addition, the dissipation rate was 13.3 W in the condition of 100% opening ratio of air convective channel and the ambient temperature of 23 °C. This outstanding thermal performance of the developed equipment was the combinative contribution of copper foam and U-tube structure in the rectangular thermal storage units due to the thermal conductivity improvement of the modified PCM and extension of the heat transfer area of the heating tube. Furthermore, the thermal storage equipment has advantages of good integrity, compactness and flexibility to meet the requirement of large-scale thermal energy storage and controllable heat dissipation by assembling the number of the heat storage units in the equipment.