非共沸工质冷凝过程中的气液分离及气相膨胀压缩特性研究

Taking aim at the current problems of two phase expansion, a new subcritical vapor compression cycle based on the vapor expansion - compression combined technique is introduced. By using the incomplete condensation, component separation and the adjustable temperature-entropy property of zeotropic mixtures, the expansion work is recovered efficiently, and hence the cycle performance is improved. The new vapor compression cycle is going to be researched in the following aspects: 1) By using theoretical analysis, the temperature-entropy property of zoetropic mixture is studied quantitatively, the effect of component, composition and molecular groups on it will be confirmed. 2) By experimental researching and numerical modeling, the mechanism of component separation of zotropic mixture through T-junction is investigated. The effects of thermo-physical parameters and flow parameters of working fluid as well as the geometrical parameters of T junction on the component separation will be determined. 3) By theoretical computing, the optimal working fluids for different working conditions will be determined, then, the synergic relationship between the entropy production of individual thermodynamic process and the total entropy production of the cycle is investigated. By finishing these researches, the law of zeotropic mixtures' phase-change heat transfer and vapor-liquid separation could be deeply comprehended. The researches are of important scientific significance and application value.

针对亚临界蒸汽压缩逆循环两相区膨胀功回收难度大、效率低的现状，在非完全冷凝及气液分离的基础上，考虑气体膨胀和压缩过程对工质温熵特性的要求，提出了气体膨胀压缩耦合的非共沸工质蒸汽压缩逆循环，以求实现提高膨胀功利用率、提升循环性能及扩大亚临界逆循环应用范围的目标。研究内容如下：1）通过理论分析，对非共沸工质温熵特性进行定量研究，明确工质组元、组份、分子基团与混合工质温熵特性的内在关联；2）通过实验与数值模拟，对非共沸工质两相流在T型管内的流动与分离过程进行深入研究，明确工质热物性参数、流动参数及流道几何参数等对组份分离特性的影响；3）通过理论计算，针对不同工况筛选适宜的非共沸工质，研究各热力过程不可逆损失与循环整体熵增的协同关系，明确系统特征参数。该研究可丰富和发展热力循环过程、相变换热、气液两相流、相分离过程传热传质等相关领域的研究，具有重要的科学意义和应用价值。

为了实现蒸汽压缩逆循环膨胀功的回收、循环性能的提升，引入气体膨胀过程，构建了基于气体膨胀压缩耦合的非共沸工质蒸汽压缩逆循环，并对该循环的关键热力过程，即气体膨胀压缩与气液分离，进行理论和实验相结合的研究。理论上结合基团贡献法，研究非共沸工质的温熵的特性，明确了非共沸工质组元、组份及分子基团与其温熵特性的关联，建立了特定温熵特性下混合工质组员与配比的预选方法。实验方面，则建立T形管相分离实验台，研究了混合工质热物性参数、流动特性参数及T形管几何结构参数对非共沸工质气液两相组分分离的作用机制，建立了多种工况下混合工质在T形管内的气液相分离及组分分离模型，完成了T形管结构的优化。在此基础上，研究了逆循环中气液分离点与混合点处的温度、压力及支路流量与膨胀压缩单元功回收量的关系，明确了膨胀压缩过程进气组份变化对功回收效率的影响，并针对不同工况，以循环效率为目标，结合多种智能优化算法，完成了非共沸工质的筛选。以上研究丰富和发展了热力循环过程，具有重要的科学意义和应用价值。