Scharinger-Urschitz Georg, Schwarzmayr Paul, Walter Heimo, Haider Markus
Institute for Energy Systems and Thermodynamics, TU Wien, Getreidemarkt 9/E302, 1060, Vienna, Austria.
Appl Energy. 2020 Dec 15;280:115893. doi: 10.1016/j.apenergy.2020.115893. Epub 2020 Oct 12.
This work examines a high temperature latent heat storage system, which could find use in future concentrated solar power and other combined heat and power plants. In contrast to lab-based fully charged or totally discharged states, partial load states will be the principal operation states in real-world applications. Hence, a closer look on the partial load states and the effective power rates are worthwhile for a successful implementation of this storage type. A vertical finned shell and tube heat exchanger pipe with a combination of transversal and longitudinal fins is applied. Sodium nitrate with a melting temperature of 306 is used as phase change material and thermal oil serves as heat transfer fluid. Temperatures in the storage and the heat transfer fluid as well as the mass flow are measured for data analysis. The state of charge formulation is based on an enthalpy distribution function, where the latent heat of fusion is spread over a specific temperature range. The data show consistently high power rates for all partial load cycles at any state of charge. The mean power rate for charging is 6.78 kW with an 95.45 % confidence interval of 1.14 kW for all cycles. The discharging power rate is -5.72 kW with a 95.45 % confidence interval of 1.36 kW for all cycles. The lowest power rate is measured for the full cycle at the end of charging/discharging. It is caused by a narrow volume, which is not penetrated by fins, near the perimeter of the cylindrical heat exchanger. The state of charge formulation correlates with the storage capacity and enables state of charge based cycling. With the energy balance of the storage, the data validity is proven and further storage parameters are determined. The energy density is as high as 110 kW h m and a power rate of 2.28 kW m for the finned tube is confirmed. These values are highly promising for further development and application of latent heat storage systems.
本研究考察了一种高温潜热存储系统，该系统可应用于未来的聚光太阳能发电及其他热电联产电厂。与基于实验室的完全充电或完全放电状态不同，部分负载状态将是实际应用中的主要运行状态。因此，深入研究部分负载状态和有效功率率对于成功应用这种存储类型具有重要意义。采用了一种带有横向和纵向翅片组合的垂直翅片管壳式换热器管。熔点为306℃的硝酸钠用作相变材料，导热油用作传热流体。测量存储装置和传热流体中的温度以及质量流量以进行数据分析。充电状态公式基于焓分布函数，其中熔化潜热分布在特定温度范围内。数据表明，在任何充电状态下，所有部分负载循环的功率率始终很高。所有循环的充电平均功率率为6.78kW，95.45%置信区间为1.14kW。所有循环的放电功率率为-5.72kW，95.45%置信区间为1.36kW。在充电/放电结束时的全循环中测量到最低功率率。这是由于圆柱形换热器周边附近有一个狭窄区域，翅片未穿透该区域。充电状态公式与存储容量相关，并实现基于充电状态的循环。通过存储装置的能量平衡，证明了数据的有效性，并确定了进一步的存储参数。翅片管的能量密度高达110kW·h/m³，功率率为2.28kW/m²。这些值对于潜热存储系统的进一步开发和应用非常有前景。
