School of Mechanical and Resource Engineering, Wuzhou University, Wuzhou, 543002, China.
School of Engineering, University of Tasmania, Hobart, TAS, 7001, Australia.
Environ Sci Pollut Res Int. 2024 Jul;31(34):46447-46461. doi: 10.1007/s11356-024-31864-7. Epub 2024 Jan 8.
The multitube design in the shell-and-tube type latent heat thermal energy storage (LHTES) system has received intensive attention due to its promising benefits in enhancing heat storage efficiency. In this paper, single and multi-tube shell LHTES systems were experimentally investigated. First, this study experimentally compared the thermal characteristics between a multiple-tube heat exchanger (MTHX) and a single-tube heat exchanger (STHX). The STHX's geometrical parameters coincided with a virtual cylindrical domain in the MTHX, being similar to the single-tube model formulated by simplifying the numerical solution to investigate the MTHX. The experimental data was then used to validate the simplified numerical model commonly used in the literature that converted the multi-tube problem to a single-tube model by formulating a virtual cylindrical domain for each tube in the MTHX system. The results showed that there was a noticeable difference in the thermal characteristics between the actual STHX and the virtual cylindrical STHX domain in the MTHX system. The comparison indicated that the simplified numerical model could not accurately reflect the thermal performance of the MTHX system. An experimental study or three-dimensional numerical modelling was required for the thermal analysis of the multi-tube problems. Second, the effect of tube number in the MTHX was experimentally investigated. It was found that an increase in tube number boosted both charging and discharging rates without inhibiting the natural convection. The five-tube configuration decreased the total charging and discharging duration by 50% compared to the two-tube one. Finally, the effect of heat transfer fluid (HTF) operating parameters on the system performance was evaluated on the five-tube MTHX system. The results revealed that the adoption of higher HTF temperature considerably improved the charging performance. The charging time decreased by up to 41% with the HTF temperature increasing from 70 to 80 °C. Meanwhile, a variation in the HTF flow rate from 5 to 20 L/min showed a more pronounced influence on charging than on discharging due to the different dominant heat transfer mechanisms.
壳管式潜热蓄热（LHTES）系统中的多管设计因其在提高蓄热效率方面的有前景的优势而受到广泛关注。本文对单管和多管壳式 LHTES 系统进行了实验研究。首先，本研究对多管式换热器（MTHX）和单管式换热器（STHX）的热特性进行了实验比较。STHX 的几何参数与 MTHX 中的虚拟圆柱域一致，类似于简化数值解来研究 MTHX 的单管模型。然后，使用实验数据验证了文献中常用的简化数值模型，该模型通过为 MTHX 系统中的每个管构建虚拟圆柱域，将多管问题转化为单管模型。结果表明，实际的 STHX 和 MTHX 系统中虚拟圆柱 STHX 域之间存在明显的热特性差异。比较表明，简化数值模型不能准确反映 MTHX 系统的热性能。需要进行实验研究或三维数值建模来进行多管问题的热分析。其次，实验研究了 MTHX 中管数的影响。结果发现，增加管数可以提高充、放热速率，而不会抑制自然对流。与两管配置相比，五管配置将总充、放时长缩短了 50%。最后，评估了在五管 MTHX 系统中传热流体（HTF）操作参数对系统性能的影响。结果表明，采用较高的 HTF 温度可以显著提高充电性能。随着 HTF 温度从 70°C 升高到 80°C，充电时间减少了 41%。同时，由于不同的主导传热机制，HTF 流量从 5 到 20 L/min 的变化对充电的影响比对放电的影响更为显著。
