| Energy and Enviromental Engineering |
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| Constrained melting heat transfer of composite phase change materials inside spherical container |
| LIU Min jie1, ZHU Zi qin1, XU Can ling1, FAN Li wu1, LU Hai1,2, YU Zi tao1,3 |
| 1. Institute of Thermal Science and Power Systems, Zhejiang University, Hangzhou 310027, China;2. Electric Power Research Institute, Yunnan Electric Power and Research Institute (Group), Kunming 650217, China；3.Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Hangzhou 310027, China |
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Abstract The constrained melting heat transfer of dodecanol based composite phase change materials (PCM) with addition of graphite nanoplatelets inside a spherical container, as a typical shape, was analyzed quantitatively by experiments in order to examine the influence of highly conductive fillers on melting heat transfer of composite PCM. By adopting the transient melt fraction by mass during melting as a means for comparison, a parametric study was conducted on the mass fraction of graphite nanoplatelets as well as the isothermal heating boundary condition. Results show that the melting heat transfer of the composite PCM experiences a transition from convection dominated to conduction dominated with the mass fraction increasing. And within the studied cases, although the thermal conductivity of the composite PCM is enhanced to some extent, such enhancement is not sufficient to compensate the loss of natural convection due to the increased viscosity but to slow down the melting process. An experimental correlation for the melt fraction was proposed in terms of the characteristic dimensionless groupings, such as the Fourier, Stefan and Grashof numbers, with predictive deviation less than 15%．
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Published: 18 September 2016
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球形容器内复合相变材料的约束熔化传热过程
为评估高导热填料对复合相变材料熔化传热过程的影响,采用实验方法定量分析典型球形容器中添加石墨纳米片的十二醇基复合相变材料的约束熔化传热过程.以熔化过程中的瞬时质量熔化率为比较对象,对石墨纳米片的质量分数和恒温加热边界条件进行参数化研究.实验结果表明,随着质量分数的增加,复合相变材料的熔化传热过程从以自然对流为主导逐渐转变为以导热为主导.在所研究的工况范围内,虽然复合相变材料的导热系数有一定程度的提高,但不足以弥补黏度增长所引起的自然对流削弱效应,反而使得熔化过程有所减缓.通过数据拟合得到了熔化率随傅里叶数、斯蒂芬数和格拉晓夫数等特征无量纲数变化的实验关联式,其预测结果的误差小于15%.
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