Experimental Study on Operating Characteristics of Nitrate Salt-Based Latent Heat Thermal Energy Storage Unit
Experimental Study on Operating Characteristics of Nitrate Salt-Based Latent Heat Thermal Energy Storage Unit
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DOI：
10.1016/j.applthermaleng.2021.117846
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发表时间：
2021-12
影响因子：
6.4
通讯作者：
Zhenxing Han;C. Wickramaratne;D. Yogi Goswami;C. Jotshi
中科院分区：
文献类型：
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作者：
Zhenxing Han;C. Wickramaratne;D. Yogi Goswami;C. Jotshi
无机盐是中高温热应用的潜在相变材料。了解它们在潜热储能过程中的行为，对于储能装置的设计和能量转换利用系统的构建是至关重要的。以NaNO 3（质量分数为46%）和KNO 3的低共熔混合物为相变储能材料，构建了一种基于硝酸盐的潜热储能单元，对其充放电过程的运行特性进行了实验研究。测定了共晶硝酸盐的热物理性质。在装料过程中，由于盐的凝固，盐的热阻增大，在盐熔化过程中，空气出口温度基本保持不变，但在出料过程中，空气出口温度逐渐降低。当进气温度从260 °C提高到270 ° C和280 °C时，熔化时间分别缩短了31.0%和38.1%。当进气温度从210 °C降低到200和190 °C时，凝固时间分别缩短了22.2%和33.3%。当空气流量从0.964 g/s增加到1.446和1.962 g/s时，熔化时间分别缩短了32.4%和57.4%，而凝固时间仅分别缩短了8%和16%。通过热损失评估可以计算出充放比，以描述充放过程中的热能变化。结果表明，加料比随熔盐的熔化几乎呈线性增加。空气质量流量对此参数有显著影响。随着进气温度的升高，进气温度的影响逐渐减弱。由于热损失和气流的耦合作用，气流参数对放电率的影响很小。贮存的有效性表明了盐的潜热被利用的程度。当进气温度从210 °C降低到190 °C时，它从29.7%增加到52.8%。该研究为硝酸盐相变特性和基于硝酸盐的潜热储能单元提供了深入的见解。
Inorganic salts are potential phase-change materials for medium- and high-temperature thermal applications. It is essential to acquire knowledge of their behavior in latent heat thermal energy storage for the design of storage devices and the construction of an energy conversion and utilization system. In this study, a eutectic mixture of NaNO3(mass ratio of 46%) and KNO3was selected as phase change material, and a nitrate salt-based latent heat thermal energy storage unit was built to experimentally investigate its operating characteristics during charging and discharging. The thermophysical properties of the eutectic nitrate salt were measured and presented. The air outlet temperature remained almost unchanged during the melting of salt in the charging process, but it decreased gradually during the discharging process because the thermal resistance increased with the salt solidification. The melting time was shortened by 31.0% and 38.1% when the air inlet temperature was increased from 260 °C to 270 and 280 °C, respectively. The solidification time was shortened by 22.2% and 33.3% when the air inlet temperature was reduced from 210 °C to 200 and 190 °C, respectively. When the air mass flow rate was increased from 0.964 g/s to 1.446 and 1.962 g/s, the melting time was shortened by 32.4% and 57.4%, respectively, while the solidification was only shortened by 8% and 16%, respectively. The charging ratio or discharging ratio can be calculated through heat-loss evaluation to depict the thermal energy change in a charging or discharging process. The results indicated that charging ratio increased almost linearly with the melting of the salt. The air mass flow rate had a significant impact on this parameter. The influence of the air inlet temperature was gradually weakened with the increasing air inlet temperature. Owing to the coupling effect of heat loss and airflow, the influence of air parameters on the discharging ratio was weak. The effectiveness of storage indicates the extent to which the latent heat of salt can be utilized. It increased from 29.7% to 52.8% when the air inlet temperature was reduced from 210 to 190 °C. This study provides insights into the phase-change characteristics of the nitrate salt and the nitrate salt-based latent heat thermal energy storage unit.