高温熔盐热物性的动态测定与误差修正方法

Dynamic measurement of thermophysical properties of molten salt and error correction method

针对目前高温熔盐相变蓄热材料热物性参数测定方法的不足,在借鉴Stefan模型和Lamvik模型的基础上,利用相变材料相变时相界面移动速率与液固相热物性参数之间的关系,设计了一套高温熔盐熔点附近热物性的动态测定装置,并提出了一种基于数值模拟的测定误差修正方法。利用该装置对已知热物性的熔盐硝酸钠、硝酸钾及溴化锌进行了动态实验测定,并利用数值模拟对测定结果进行了修正。修正后的结果和参考值之间的误差比修正前要显著减小,硝酸钠和硝酸钾的热导率、热扩散率误差均小于5%。表明该修正方法可以有效地降低测定过程中由于非一维导热、边界条件不稳定所造成的测定误差,将动态测定与该修正方法结合起来能提高测试精度,为其他熔盐热物性的深入研究提供了基础数据和理论依据。

Since the data of thermophysical properties of high temperature phase-change heat storage materials are limited and the measurement methods are lacking,an apparatus based on the Stefan model and Lamvik model was designed to determine dynamically the thermophysical properties of high-temperature molten salt at the melting point based on the relationship between the speed of the moving phase-transition interface and the thermophysical properties of liquid-solid phase in the melting and solidification processes.An error correction method was put forward to correct the result by simulating dynamic testing processes and implemented numerically by using user defined functions（UDFs）.Some samples of sodium nitrate,potassium nitrate and zinc bromide with known thermophysical properties were measured and the results were corrected.Compared the experimental results and corrective results of thermal conductivity and thermal diffusivity of sodium nitrate and potassium nitrate with the values recommended in literature,the errors are less than 5%.The results of three molten salts show a significantly smaller error between the calculation and the test result after the correction than before the correction,and the thermal conductivity confirms that the error correction method significantly reduces the error from non-one-dimensional heat conduction and unstable temperature boundary conditions.The combination of dynamic measurement with the error correction can improve the accuracy of apparatus and reduce the requirements for testing devices.The reliability of the method is confirmed experimentally.This study may offer basic data and theoretical foundation for further investigation on thermophysical properties of other high temperature molten salts.