储能科学与技术

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基于T-history法的脂肪酸相变材料的凝固-熔化动力学模型及关键参数研究

刘思麟(), 曹晓玲(), 张沛璐, 冷子瑜   

  1. 西南交通大学机械工程学院，四川 成都 610031
  • 收稿日期:2024-03-01 修回日期:2024-04-03
  • 通讯作者: 曹晓玲 E-mail:liusilin@my.swjtu.edu.cn;xlcao@swjtu.edu.cn
  • 作者简介:刘思麟（1999—），男，在读硕士研究生，研究方向：相变储能，E-mail：liusilin@my.swjtu.edu.cn；
  • 基金资助:
    国家自然科学基金(52108097);中央高校基本科研基金(2682022CG007);国家重点研发计划课题(2022YFC3802704)

Determination of kinetic parameters of fatty acid phase change materials based on T-history method

Silin Liu(), Xiaoling Cao(), Peilu Zhang, Ziyu Leng   

  1. School of Mechanical Engineering, Southwest Jiaotong University, Chengdu 610031, Sichuan, China
  • Received:2024-03-01 Revised:2024-04-03
  • Contact: Xiaoling Cao E-mail:liusilin@my.swjtu.edu.cn;xlcao@swjtu.edu.cn

摘要：

相变材料的熔化、结晶特性对相变储能具有重要意义，现有相变模型设定相分数与温度区间呈线性关系，未能考虑温度变化速率对相变过程的影响，因而在有关应用中的预测准确率较低。本文为研究温度与温度变化速率共同作用下的两相转化规律，对相变过程进行了理论分析，以相分数作为关键参数，通过固相和液相的PCM组分之间的可逆反应建立凝固-熔化动力学模型。设定Avrami方程作为模型中的反应函数，以Arrhenius方程作为模型中的速率函数。选用建筑领域常用的脂肪酸类相变材料—正癸酸、月桂酸、辛酸作为实验材料，采用T-history法，通过等温结晶实验对Avrami方程进行拟合验证。在经过验证证实Avrami方程与等温结晶实验所获得数据之间呈现出高度一致性与可靠性之后，通过非等温实验测试获得相变材料在不同温度与温度变化速率下的热力学信息，结合热分析动力学方法，对模型中的关键动力学参数进行研究测定。研究结果表明：活化能与常数因子变化趋势一致且存在互补效应，不同相变材料的活化能与常数因子大小不同，随相变过程进行，变化情况不同。反应级数随着温度变化速率的增大而减小，且凝固过程的反应级数普遍大于熔化过程。

关键词: Avrami模型, 相变动力学模型, T-history法, 动力学参数

Abstract:

The existing phase transition models artificially set the phase fraction to be linearly related to the temperature interval, failing to consider the influence of the temperature change rate on the phase transition process, and thus the prediction accuracy is low in the relevant applications. In this paper, in order to study the two-phase transformation law under the joint effect of temperature and temperature change rate, a theoretical analysis of the phase change process is carried out, and a solidification-melting kinetic model is established through the reversible reaction between the PCM components in the solid and liquid phases with the phase fraction as the key parameter. The Avrami equation was set as the reaction function in the model, and the Arrhenius equation was used as the rate function in the model. Fatty acid phase change materials commonly used in the construction field: n-decanoic acid, lauric acid, and octanoic acid were selected as experimental materials, and the Avrami equation was fitted and verified by isothermal crystallization experiments using the T-history method. After verifying that the Avrami equation shows a high degree of consistency and reliability with the data obtained from isothermal crystallization experiments, the thermodynamic information of the phase change materials at different temperatures and rates of temperature change was tested by non-isothermal experiments, and the key kinetic parameters in the model were studied and determined by combining with the kinetic method of thermal analysis. The results show that the activation energy and the constant factor change in the same trend and there is a complementary effect, and the activation energy and the constant factor of different phase change materials have different sizes, and the changes are different with the phase transition process. The number of reaction levels decreases with the increase of temperature change rate, and the number of reaction levels in the solidification process is generally larger than that in the melting process.

Key words: Avrami model, phase transition kinetic model, T-history method, kinetic parameters

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