Study on thermal storage performance of a novel conical spiral tube heat storage system

Abstract

Due to the structural advantage of the conical spiral tube, which is narrow at the top and wide at the bottom, it helps to improve the thermal response rate of the heat storage system. Therefore, this study proposes a novel conical spiral tube heat storage system. The software Fluent is used to conduct three-dimensional unsteady state calculations and investigate the effects of the conical ratio, taper, and length-to-diameter ratio on the phase change material (PCM) thermal storage performance. The results indicate that when the conical ratio is increased from 1.0 to 3.0, the PCM heat storage capacity is reduced by 1.05%, the melting time is shortened by 17.60%, the average heat storage rate is increased by 20.10%, and the heat storage efficiency is reduced by 0.10%. Continuing to increase the conical ratio, the optimization of the performance is not obvious. Subsequently, a conical ratio of 3.0 heat storage tank is used as the reference unit. When the tank taper is increased from 0 to 0.22 and the length-to-diameter ratio is increased from 1.44 to 1.85, the melting time is shortened by 7.59% and 32.62 %, the heat storage capacity is reduced by 3.45% and 9.24%, the average heat storage rate is increased by 4.47% and 34.69%, and the heat storage efficiency is reduced by 0.02% and increased by 7.99%, respectively. Continuing to increase the taper from 0.22 to 0.32 does not result in an effective improvement of the performance. This study is a good guide for the optimization of the thermal storage performance of spiral tube heat storage systems and the efficient use of solar energy.