参比温度曲线法的改进与实验研究

Improvement and Experimental Study of the T-history Method

相变蓄热材料应用广泛,其热物性的测量至关重要。本文基于参比温度曲线法的基本思想,从相变蓄热材料的理论步冷曲线特征和实际测量过程出发,针对相变阶段中能量平衡方程的显热因素和相变结束阶段降温过程的温差因素进行分析和改进,得到了改进后的计算方程。并以十二水磷酸氢二钠、月桂酸和硬脂酸三种相变材料为例进行相变材料步冷曲线的实验研究,结合改进后的计算方程进行相变潜热值的计算。结果表明:改进后的方程对潜热的计算值与DSC测量值相比更接近,误差控制在10%以内。参比温度曲线法的改进对于相变蓄热材料的快速开发和调制具有一定的实践指导意义。

Phase-change heat-storage material( PCM) is widely used in many fields,and its thermophysical properties are the key factor for its application. In this study,an improvement of the T-history method is presented,based on the basic principle of the T-history curve method,the theoretical step curve of the PCM and the actual step-curve measurement process. Firstly,according to crystalline-melting thermodynamic conditions,a certain degree of supercooling is necessary for crystal crystallization; therefore,there is sensible heat between the phase-change-start phase and the phase-change-end phase. Then,the energy-balance equation was improved by considering the sensible heat effect on the energy-balance equation in the phase-change stage,and the temperature-difference effect on the energy-balance equation in the cooling process of the phase-transition phase. Secondly,the phase-change material was placed in a constant-temperature water source at 70 ℃ until it melted. Then,it was placed in a constant-temperature box at 10 ℃. The step curve was obtained with a twosecond interval measurement. Finally,the experimental results for three phase-change materials,sodium dodecahydrate disodium phosphate,lauric acid,and stearic acid,were calculated according to the improved equations to verify the improvement of the T-history method. The results show that the calculated value of the latent heat is closer to that of the differential-scanning calorimetry process,and the error is less than 10%. Therefore,the improvement of the T-history method has a certain practical significance for the development and testing of phase-change thermal energy storage material.