Abstract:

Taking advantage of the fixed-temperature energy storage characteristics of phase change materials, a latent heat energy storage system with water as the heat exchange fluid and microencapsulated phase change material (MPCM) slurry as the energy storage medium was built. In this experimental system, water worked as heat transfer fluid and MPCM slurry acted as the energy storage medium. The cooling discharging characteristics of this system were characterized by the cooling rate, phase transformation completion rate, volumetric thermal release capacity and convective heat transfer coefficient. Through the comparisons between this latent thermal energy storage system and the sensible thermal energy storage system using pure water as the working medium, the influences of different flow rate of circulating water and stirring rate on the cooling discharging performance of this system was analyzed. The results indicated that the phase transformation of MPCM mainly occurred in the range of 17—19℃, and the phase transformation completion rate is approximately 90% when the slurry temperature was 20℃. The cooling discharging rate increased with the increasing the circulating water flow rate. When the flow rate of circulating water is 6 L·min^-1, the maximum cooling discharging rate of MPCM slurry reached 1.52 kW in the phase transition region, which is 70% higher than that of the sensible thermal energy storage system. In the range of 0—200 r·min^-1, the volumetric thermal release capacity and convective heat transfer coefficient of MPCM slurry can be increased by increasing the stirring rate. At the stirring rate of 200 r·min^-1, the volumetric thermal release capacity and convective heat transfer coefficient of MPCM slurry are 73.86 MJ·m^-3 and 2176 W·m^-2·K^-1, respectively, which are 1.66 and 1.87 times higher than that of sensible thermal storage system.

Key words: phase change, microcapsule slurry, thermal energy storage system, heat transfer, convection, cooling discharging

摘要：

利用相变材料定温储能特性，搭建了以水为换热流体、相变微胶囊（MPCM）悬浮液为储能介质的潜热储能系统。采用放冷速率、相变完成率、单位体积放冷量和对流传热系数表征实验系统的放冷特性，通过该潜热储能系统与以纯水为工作介质的显热储能系统的对比，分析了循环水体积流量以及搅拌速率对系统放冷性能的影响。结果表明：MPCM主要在17~19℃范围内发生相变，当悬浮液温度到达20℃时，其相变完成率接近90%；增大循环水流量可以提高放冷速率，循环水体积流量为6 L·min^-1时，MPCM悬浮液的放冷速率在相变区间最高可达1.52 kW，相较于显热储能系统提升了70%；在0~200 r·min^-1的范围内，增大搅拌速率可增大MPCM悬浮液的单位体积放冷量和对流传热系数，搅拌速率为200 r·min^-1时，MPCM悬浮液的单位体积放冷量和对流传热系数分别为73.86 MJ·m^-3和2176 W·m^-2·K^-1，比显热储能系统分别高1.66倍和1.87倍。

关键词: 相变, 微胶囊悬浮液, 储能系统, 传热, 对流, 放冷