应用于空分纯化系统的相变储热器建模及分析

Modeling and analysis of latent heat storage unit used in air separation purification system

为实现空分纯化系统污氮气余热的回收再利用,设计了一种采用相变储热器的新型空分纯化系统,同时提出了相应的相变储热器设计方法。首先,对空分纯化系统进行数据采集,并通过回归获得污氮气温度、流量等参数的特性函数。随后,建立了非稳态变温热源下的相变储热器动态数学模型,并推导相变材料在污氮气特性函数作用下的温度通用表达式。其次,以储、放热整体循环的最大放热量为目标函数,采用微分进化算法优化储热器内相变材料熔化温度、质量等关键参数。最后,通过穷举计算了单、双级相变储热器中相变温度与余热利用率之间的关系。计算结果表明,对于单级相变储热器,最佳的相变温度为59.67℃,最大余热利用率约为0.41;对于双级相变储热器,第一级和第二级的最佳相变温度分别为73.68℃和46.04℃,最大余热利用率约为0.52。本研究为提升空分纯化系统能效奠定了理论基础。

In order to achieve recovery and reuse of waste heat in air separation purification system,a novel type of air separation purification system using latent heat storage unit was designed,and the corresponding design method for the latent heat storage unit was proposed.First of all,data collection was performed on the air separation purification system,and the characteristic functions of pollutant nitrogen parameters such as the temperature and flow rate were obtained by regression.Then,a dynamic mathematical model of the latent heat storage under the unsteady-state pollutant nitrogen heat source was established,and the general temperature expression of the phase change materials was derived.Subsequently,taking the maximum heat release capacity of latent heat storage unit in the whole cycle as the objective function,the differential evolution algorithm was used to optimize the key parameters such as the melting temperature and quality of phase change materials.At last,the relationship between the melting temperature and the waste heat utilization rate in the single-stage and double-stage latent heat storage units was calculated by exhaustion.The results showed that for the single-stage latent heat storage,the optimal melting temperature is about 59.67℃,and the maximum waste heat utilization rate is about 0.41.For double-stage latent heat storage,the optimal melting temperatures are 73.68℃and 46.04℃,respectively,and the maximum waste heat utilization rate is about 0.52.This study provided theoretical guidance for improving the energy efficiency of air separation purification system.