喷射器增效自复叠制冷系统的工质分布迁移机理及动态特性研究

Applying zeotropic refrigerants based autocascade refrigeration cycle in low temperature refrigeration system is an efficient energy saving technical approaches. This project proposes an ejector enhanced autocascade refrigeration system which has more evident advantage of energy-saving. We will carry out deep theoretical and experimental research with simulating and experimental methods on the system in terms of the dynamic operating characteristics and the mechanism of mixture refrigerant distribution and migration. We will investigate the coupled relationship among the system component configurations, internal parameters and external parameters in order to obtain relevant system optimization theory and method. In addition, we will conduct the research of mixture refrigerant mass distribution characteristics under steady operation and start/stop operations, and reveal the internal mechanism of static and dynamic separations of the mixture refrigerant composition and their inter-transformation for getting the optimum control method and scheme of mixture refrigerant migration during start/stop operations. Furthermore, we will study the structure optimization and operation performance of the liquid-gas ejector at variable operating conditions, and present the variation features of ejector efficiencies with the structure parameter, mixture composition and operating conditions, and thus acquire the theoretical prediction model of ejector efficiencies and the optimal designing method of ejector. Finally, we will investigate the temperature pull down capability of refrigeration system and the variations of system energy efficiency during on-off cycles, and achieve the optimal control strategy and technical scheme for realizing the high efficient and reliable operation of the refrigeration system. The prospective research results of this project will provide the theory basis and methodological support on the actual establishment and application of the ejector enhanced autocascade refrigeration system, and advance the development of the theory and technique with respect to the liquid-gas ejector.

自复叠制冷循环是实现低温制冷的有效技术途径，本项目提出了一种节能优势明显的喷射器增效自复叠低温制冷循环系统。拟采用计算模拟和实验方法对系统的动态工作特性及工质的分布与迁移机理进行深入的理论和实验研究。研究系统的配置参数、内部参数及外部参数之间的基本耦合关系，获得系统优化匹配理论与设计方法；研究系统稳态运行与启停动态过程中工质分布特性，阐明工质组分静态与动态分离及其转移的内在机理，确立改善系统性能的最佳启停机工质迁移调控方法与技术方案；进行喷射器的结构优化和变工况性能研究，揭示喷射器效率随关键结构参数、工质配比和工况条件的变化规律，获得喷射器效率的理论预测模型及喷射器优化设计方法；探索系统的开机动态降温特性与间歇运行能效规律，获得实现系统高效稳定运行的最佳运行控制策略与技术方案。预期研究结果将为系统的实际构建与应用提供理论依据与技术支持，同时促进喷射器方面的理论研究与应用发展。

本项目采用了计算机仿真和实验方法对喷射器增效自复叠制冷系统的动态工作特性及工质的分布与迁移机理进行深入的理论和实验研究。通过对喷射器增效自复叠制冷循环建立热力学仿真模型，准确预测了不同工况下的两相喷射器工作性能，并获得了制冷循环性能随工况参数和工质浓度的变化规律，明晰了新型制冷循环的性能优势，为后续实验提供了理论指导；搭建了喷射器增效自复叠制冷系统实验台并进行了相关稳态性能实验，研究了制冷剂配比、节流阀开度等操作参数对系统稳态运行特性和喷射器性能特性的影响规律，掌握了系统主要部件优化匹配原则；与此同时，研究了系统的降温和间歇运行的动态工作特性，掌握了系统配置与操作参数对冰箱降温速度、开机率的影响规律，获得了实现系统高效稳定运行的最佳运行策略；此外，还进行了关键部件喷射器的结构优化和变工况性能研究，掌握了喷射器结构参数与系统动态运行特性的基本耦合机制；通过气相色谱法研究了系统中制冷剂浓度分布特性以及启停过程中循环浓度的变化规律，获得了操作参数对制冷剂浓度分布特性的影响规律，以及系统降温过程制冷剂浓度的变化特性，同时还明确了系统制冷剂循环浓度与充注浓度之间的偏差规律，提出了制冷剂循环浓度的预测实验关联式；在上述研究的基础上，进一步制作了基于喷射器增效原理的低温冰箱样机，探索了新样机间歇运行的系统动态特性，明确了相对于常规低温冰箱，该系统可有效降低样机的耗电量，具有显著的节能潜力。课题组在喷射器增效循环方向发表的已标注基金号的国际期刊论文有21篇，均已为SCI检索并引用，取得了一定的研究成果，且基于该课题研究已申请10项发明专利，其中9项已授权。此外，依托本课题共培养了5名博士生和2名硕士生。本课题从更深的层次上揭示了喷射器增效制冷循环的热力学原理和系统工作基本规律，进一步丰富了喷射器增效技术的理论体系，同时为喷射器在低温冰箱领域的应用打下了良好基础。