基于T-history曲线计算材料相变潜热方法的改进

目的改进以T-history曲线为基础计算相变材料潜热的方法。方法对相变材料降温过程用温度记录仪测得的数据,分别以高次多项式和三次样条插值法拟合,而后分别计算去离子水和水合盐的相变潜热。对于无过冷度相变材料,以拟合后降温曲线一阶导数最高点、一阶导数突变点和拐点分别作为相变起始位置计算相变潜热。结果三次样条插值法拟合后求得相变潜热值与理论值偏差小于10%,对于无过冷度的相变材料,一阶导数最高点作为相变起始点时,相变潜热计算值与理论值偏差最大为8.01%,最小为1.55%。结论采用三次样条插值拟合法计算PCM的相变潜热,最稳定且接近理论值,以一阶导数最高点为相变起始点计算无过冷度的相变材料的相变潜热结果更精确。

Improvement of Calculation Method for Material Phase Change Latent Heat Based on T-history Curve

Objective To improve the calculation method for latent heat of material phase change based on T-history curve. Methods The time-temperature data measured during cooling of phase change material by the temperature logger were fitted into curves with polynomial and cubic spline interpolation, to calculate the latent heat of deionized water and hydrated salt, respectively. For phase change material without supercooling, the first derivative maximum, the point mutation in the first derivative, and the inflection of the cooling curve after fitting were used as the beginning point of phase change to calculate the latent heat, respectively. Results The deviation from the theoretical value of fitting with cubic spline interpolation was substantially less than 10% . For phase change material without supercooling, when the first derivative maximum was used as the beginning point of phase change, the maximum deviation from the theoretical value from the calculated value of latent heat was 8.01%, and the minimum was 1.55%. Conclusion Calculation of the latent heat of PCM by fitting with cubic spline interpolation was the most stable and close to the theoretical value. When the first derivative maximum was used as the beginning point of phase change to calculate the latent heat of the phase change material, the result was more accurate.