Comparison of a single stage and a multistage latent heat storage for domestic hot water delivery.

In this paper we assess the potential to use multiple PCM in combination with a compact heat exchanger for direct domestic hot water (DHW) delivery purposes for e.g. district heating substations. The results of the measurements on a compact thermal energy storage device based on multiple phase change materials (PCM) with different melting temperatures are compared to a geometrical identical system with a single PCM with one melting temperature. The experimental campaign was performed in the thermo-technical laboratory (TTL) located at the VITO in Mol, Belgium. To assess the potential for prolonged DHW delivery, both tanks are charged by circulating Heat Transfer Fluid (HTF) at 70°C for 6 hours. This ensures that PCM in all tanks are completely melted. Afterwards, circulation through the storage units is suspended and the HTF is cooled until the temperature reaches 20°C. Finally, the HTF is again circulated through the storage units, entering the bottom tank, and data is logged. Measurements on the storage units show that the use of multiple phase-change materials, arranged in a cascading way clearly enhance the efficiency of the heat transfer and thus the overall performance of the storage unit. Instant delivery of domestic hot water is possible at the desired temperature also after several hours of idling.

本文评估了将多种相变材料（PCM）与紧凑型换热器结合用于直接生活热水（DHW）供应的潜力，例如应用于区域供热变电站。基于具有不同熔化温度的多种相变材料（phase change materials，PCM）的紧凑型热能存储装置的测量结果，与几何结构相同但仅使用单一熔化温度相变材料的系统进行了对比。实验在位于比利时莫尔市VITO的热工实验室（TTL）开展。为评估延长生活热水（DHW）供应时间的潜力，两个储罐通过在70℃下循环传热流体（HTF）6小时进行充热，确保所有储罐中的相变材料完全熔化。随后，停止通过存储单元的循环，并将传热流体（HTF）冷却至20℃。最后，传热流体再次循环通过存储单元（从底部储罐进入），并记录数据。对存储单元的测量表明，采用级联方式排列的多种相变材料可显著提高传热效率，从而提升存储单元的整体性能；即使在闲置数小时后，仍可在所需温度下即时供应生活热水。