Phase Change Materials (PCM) are those which are capable of reacting to variations in temperature, pressure and other environmental conditions. But the PCM’s low heat conduction makes it difficult to satisfy the demand for charging and discharging. Accordingly, optimization of Thermal Storage Unit (TSU) is required. In this paper, the PCM loading velocity of an oval pipe with variable length and many internal pipes was analyzed by means of numerical simulation. It is shown that the natural convection is very significant for the thermal exchange of PCM and PCM. Furthermore, the rate of melting in the lower section of the heat reservoir is slower than that in the upper section. Horizontal oval tubes are used for external tubes to improve fusion speed, and vertical oval tubes are needed for internal tubes. Through the modification of the construction, it can shorten the heat storing time by 182.5 sec, and by adopting the three inner tube construction, the heat storing speed is increased by 48.56 %, and the time is decreased by 480.5 s.

中文翻译：

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多管蓄热系统数值模拟研究

相变材料 (PCM) 是能够对温度、压力和其他环境条件的变化做出反应的材料。但PCM的低导热性使其难以满足充放电的需求。因此，需要优化蓄热单元（TSU）。本文通过数值模拟的方法，对变长椭圆管和多内管的PCM加载速度进行了分析。结果表明，自然对流对于相变材料和相变材料的热交换非常重要。此外，储热器下部的熔化速度比上部的熔化速度慢。外管采用水平椭圆管，以提高融合速度，内管需采用垂直椭圆管。通过结构改进，可缩短蓄热时间182.5秒，采用三内管结构，蓄热速度提高48.56%，时间缩短480.5秒。