Study on thermal conductivity of paraffin-expanded graphite composite phase change materials

doi:10.11949/0438-1157.20201769

Abstract

Abstract:

It is a common method to improve the thermal conductivity of paraffin-based phase change materials that adding expanded graphite (EG) to paraffin (PA). It is valuable for the application of PA-EG composite to predict its thermal conductivity accurately. Through the analysis of the microstructure characteristics of PA-EG composite phase change materials with EG mass fraction less than 20%, a micro model based on the uniform dispersion of EG fibers in PA was established, the phase change process of uniformly dispersed structural units was numerically simulated, the influence of EG mass fraction and its particle size on the equivalent thermal conductivity of uniform dispersion unit was analyzed, and a prediction model was proposed for the thermal conductivity of the PA-EG phase change materials suitable for different preparation methods. The experimental results of PA-EG composite phase change materials with EG mass fraction less than 20% are in good agreement, with the maximum error of 15.1%.

Key words: paraffin, expanded graphite, composite phase change materials, heat transfer, phase change

摘要：

在石蜡（PA）中复合添加膨胀石墨（EG）是提高石蜡基相变材料导热性能的一种常见方法，准确预测PA-EG复合相变材料的热导率对于其应用十分重要。通过对EG质量分数小于20%的PA-EG复合相变材料微观结构特征的分析，建立了基于EG纤维在PA中均匀分散的微观结构几何模型，数值模拟了完全均匀分散PA-EG单元体的相变过程，分析了EG质量分数及其粒径对PA-EG复合相变材料等效热导率的影响规律，并提出了可适用于不同制备方法的PA-EG复合相变材料热导率预测模型。模型预测结果与已报道EG质量分数小于20%的PA-EG复合相变材料实验结果能较好吻合，误差小于15.1%。

关键词: 石蜡, 膨胀石墨, 复合相变材料, 传热, 相变

CLC Number:

TB 33

Ken LIN, Xiaoyong XU, Qiang LI, Dinghua HU. Study on thermal conductivity of paraffin-expanded graphite composite phase change materials[J]. CIESC Journal, 2021, 72(8): 4425-4432.

林肯, 许肖永, 李强, 胡定华. 石蜡-膨胀石墨复合相变材料热导率研究[J]. 化工学报, 2021, 72(8): 4425-4432.

Figures/Tables 9

Fig.1 Microstructure of PA-EG composite phase change material

Fig.2 Assumption of PA-EG microscale structure

Table 1 Materials properties

Materials

Density/(kg/L)

Thermal

conductivity/

(W/(m·K))

Melting

latent

heat/(kJ/kg)

Specific

heat

capacity/

(kJ/(kg·K))

Fig.3 Grid independence test of PA-EG unit

Fig.4 Melting section of PA-EG units

Fig.5 Calculation results of PA-EG units and their fitting

Fig.6 Melting rate of pure PA materials with different thermal conductivity

Fig.7 Deduction of dispersion coefficient α from experimental results of PA-EG composite phase change materials[10,14,17,19,21,35-36]

Fig.8 Comparison of experimental results and estimated results of PA-EG composite phase change material [15,18]

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