生活水箱内相变材料封装结构改进及熔化性能研究  

Study on Improvement and Melting Performance of Phase Change Material Encapsulated Structure in Domestic Hot Water Tank

作　　者：俞准[1] 王姜 严中俊 庹晓糠 李水生 张国强[1] YU Zhun;WANG Jiang;YAN Zhongjun;TUO Xiaokang;LI Shuisheng;ZHAGN Guoqiang(College of Civil Engineering,Hunan University,Changsha 410082,China;China Construction Fifth Engineering Bureau Ltd,Changsha 410014,China)

机构地区：[1]湖南大学土木工程学院,湖南长沙410082 [2]中国建筑第五工程局有限公司,湖南长沙410014

出　　处：《湖南大学学报（自然科学版）》2021年第11期215-222,共8页Journal of Hunan University:Natural Sciences

基　　金：国家重点研发计划资助项目(2019YFD1101300);中建五局资助项目(900201528)

摘　　要：针对生活水箱内封装相变材料现有强化换热方法(如添加翅片或膨胀石墨)会导致蓄能密度降低与石墨沉降等问题,提出在不添加外物的基础上,对当前水箱中应用最为广泛的圆柱型封装结构进行优化改进,通过减小其底面/顶面半径比形成侧壁面倾斜的倒圆锥型结构,使得固态相变材料在重力作用下自然沉降时可充分与面积占比较大的侧壁面发生接触熔化,从而实现相变材料熔化性能的提高.为探究倒圆锥型封装相变材料熔化性能,建立相应熔化传热模型,并通过可视化实验进行验证.在该模型的基础上,对倒圆锥型和圆柱型结构封装相变材料的熔化性能进行了对比和分析.结果显示在相同体积(1.74e-04 m3)和高度(0.055 m)下,倒圆锥型结构封装相变材料完全熔化时间为2520 s,与圆柱型结构相比缩短了690 s,熔化性能提高了21.5%.倒圆锥型结构封装相变材料熔化过程中,除接触熔化外液态相变材料的自然对流也对熔化性能有显著影响,且侧壁处形成的Rayleigh-Bernard环流会削弱相变材料接触熔化性能.此外,发现在自然对流与接触熔化共同作用下,正圆锥型结构封装相变材料熔化性能与倒圆锥型结构相比更强,提高了16.7%.在实际应用中可将正圆锥与倒圆锥型封装结构结合使用,在有效利用空间的基础上实现蓄热量和蓄热效率的同时提高.The existing enhancement methods for the heat transfer of phase change material(PCM) in domestic hot water tank, such as adding fins and the expanded graphite, can lead to the reduction in the energy storage density of the encapsulation. Additionally, the graphite may settle during the melting process of PCM. To address this issue, a feasible solution is to promote the PCM’s melting performance through improving the structure of cylindrical contain-ers, which have been widely applied in domestic hot water tank, thereby taking advantage of contact melting modes without adding additional materials. In particular, an inverted conical container, which has a relatively lower ratio of the top area to the bottom area when compared to the cylindrical containers, has been proposed to encapsulate the PCM with the goal of establishing the contact melting mode between solid PCM and heated side walls when the PCM drops. To evaluate its performance, a mathematical model was developed and validated by the results obtained from a visualization experiment. Based on this model, the melting performance of the PCM encapsulated in the inverted conical container was analyzed and compared with that encapsulated in cylindrical container. The results show that the total melting time of the PCM encapsulated in the inverted conical container is 2 520 s under the same volume(1.74 e-04 m;) and height(0.05 m). It is decreased by 690 s when compared with that encapsulated in the cylindrical container, which indicates the melting performance has improved 21.5%. Except for the contact melting, the natural convection of the liquid PCM also strongly affects the melting performance of the PCM. It is found that the Rayleigh-Bernard convection in the side region results in the decrease of melting performance of the PCM. In addition, an interesting finding is that higher melting performance(i.e.16.7%) is achieved for the PCM encapsulated in the conical container when compared with that encapsulated in the inverted conical container. In this view, th

关 键 词：生活水箱 相变材料 封装结构 接触熔化 自然对流 

分 类 号：TU83[建筑科学—供热、供燃气、通风及空调工程]