太阳能热发电复合相变蓄热材料的实验研究  

Experimental Investigation on Phase Change Thermal Storage Material Composite for Solar Energy Thermal Power

作　　者：李勇[1] 郭蓓[1] 黄官飞[1] 谭书鹏[1] 河合武 宫保修一 束鹏程[1] 

机构地区：[1]西安交通大学能源与动力工程学院,西安710049 [2]日本揖斐电株式会社

出　　处：《西安交通大学学报》2014年第3期49-53,95,共6页Journal of Xi'an Jiaotong University

摘　　要：针对相变材料无机盐KNO3/NaNO3(摩尔比50/50)导热系数低,影响了蓄热系统充放热过程传热效率,制备了适用于太阳能热发电系统的无机盐/膨胀石墨复合相变材料,对复合相变材料的微观结构和热物性进行了分析,并搭建充放热测试平台对相变材料分别进行了热性能研究。结果表明:复合相变材料中的无机盐均匀分布在膨胀石墨中,其相变潜热与基于复合材料中无机盐质量分数的计算值相当,添加膨胀石墨后相变材料的导热系数得到了改善;在充热过程中纯无机盐的换热方式以自然对流为主,同一蓄热单元内沿轴向上下位置温差较大,不同蓄热单元内相同位置完成充热过程所需时间从上到下依次增加,而对于无机盐/膨胀石墨复合相变材料(质量比90/10)充热过程以导热为主;与纯无机盐不同,同一蓄热单元内沿轴向上下位置温度变化趋势基本一致,不同蓄热单元相同位置完成充热过程所需时间几乎没有差别。添加膨胀石墨后,相变材料的充热过程所需时间减少较小,而放热过程所需时间减少约45%,传热介质流量的变化对复合相变材料充/放热过程影响较小。Low thermal conductivity of inorganic salt KNO3/NaNO3 （mole ratio 50/50） usually leads to low heat transfer efficiency of thermal energy storage （TES） system. Thus a phase change material （PCM） composite with inorganic salt and expanded natural graphite （ENG） for solar energy thermal power is prepared. The micro-structures and thermal properties are analyzed, and an experimental heat charging/discharging system is set up for testing the heat transfer performance of the PCM. The results show that the solid inorganic salt is uniformly distributed on the ENG powder inside PCM composite and the latent heat of PCM composite gets equal to the calculation of the mass ratio of inorganic salt. The thermal conductivity of PCM is enhanced after inserting ENG. The heat transfer in pure PCM is mainly controlled by natural convection, which results in a large temperature difference from top to bottom along the axial direction in the same TES unit, and the time for completing charging at the same positions in different units increases from top to bottom. For PCM composite（mass ratio 90/10）, the heattransfer is mainly driven by thermal conductivity in charging process. The temperature variations are almost the same at the same locations in the radial direction in a unit, and the time for completing charging at the same positions in different units remains constant. After adding ENG into inorganic salt, the time for PCM completing charging decreases slightly, while the time for discharging reduces by 45 %. The changed oil flow rates exert little influence on the heat transfer in PCM composite.

关 键 词：KNO3 NaNO3 膨胀石墨 相变材料 太阳能热发电 

分 类 号：TK512.4[动力工程及工程热物理—热能工程]