Phase change heat storage technology can solve the problem of solar energy intermittency and instability
and is a very promising energy storage technology. However
the efficiency of the heat storage unit is related to the phase change material and the heat transfer structure. In this paper
the heat storage capacity and phase change process of composite phase change materials in a double helical tube heat storage device were studied. The effects of different operating conditions (flow rate and inlet temperature) on the heat storage device in the melting stage were investigated by experiments. The numerical simulation method is used to explore the evolution of the temperature field inside the heat storage unit
and the structure of the heat storage unit is optimized to solve the problem of slow melting area in the heat storage unit. The results show that the change of flow rate has little effect on the melting and power of composite phase change materials. The inlet temperature has a significant effect on the melting of phase change materials. When the temperature increases from 80 ℃ to 90 ℃
the melting time of the composite phase change material is shortened by 30.23%. The maximum storage energy is 5.26 MJ. Experiments and simulations show that there is a slow melting zone. The effects of different coil diameters and compression ratios on the thermal performance of the heat storage unit are analyzed. The results show that when the coil diameter is 88 mm and the compression ratio is 21∶10∶21
the heat transfer of the heat storage unit is more uniform
the complete melting time is shortened by 71.3%
the average heat flux density is increased by 42.5%
and the slow melting zone is completely melted in 22578 s.
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