基于气液喷射泵的太阳能喷射制冷系统的构建及特性研究

Solar refrigeration is one of the most rational ways to utilize solar energy and solar-driven ejector refrigeration system with thermal storage system is becoming a hot research topic. Currently, the steady-state thermodynamic performance of subcritical cycle is always studied with various refrigerants. In this project, the transcritical cycle and subcritical cycle of this system is taken as research objects. Considering that the circulation pump has the difficulty in raising the pressure of condensed fluid to supercritical state in subcritical cycle , a vapor- liquid injector is posed to take the place of the of circulation pump in the system, hence a solar bi-ejector refrigeration system based on vapor-liquid injector is established. The concrete research contents mainly include: theoretically analyzing and calculating the performance of the added vapor-liquid injector in the system; illuminating the influence mechanism of key thermodynamics parameters on system performance; establishing optimization evaluation method for the system, and optimizing the operating parameter and working medium from the view of thermodynamics and economics; building the dynamic model of the system considering the coupling of multi-components such as heat exchanger and ejector, and simulating system’s performance change and dynamic characteristics considering the change of climate and load; experimentally testing the dynamic characteristics the system. The smooth implementation of this project will provide theoretical reference for the promotion of solar ejector refrigeration system. Therefore, this project has important theoretical significance and engineering application value.

太阳能制冷是利用太阳能的最合理方式之一，带有蓄热装置的太阳能驱动喷射制冷系统正成为研究热点。目前对该系统的研究多为对采用多种制冷工质的亚临界循环进行稳态热力学性能研究。本项目分别以这种系统的亚临界循环和跨临界循环为研究对象，并针对在跨临界循环中，循环泵难于将冷凝液体的压力提升到超临界状态的难点，提出以气液喷射泵替代系统中的循环泵，构建了基于气液喷射泵的太阳能喷射制冷系统。具体研究内容包括：理论分析和计算系统新增加的气液喷射泵的性能；阐明关键热力学特性参数对系统性能影响机理，建立系统的优化评价方法，从热力学角度和热经济学角度来优化运行参数和工质；建立系统换热器和喷射器耦合的动态模型，模拟研究在气候变化和负荷变化条件下，系统的性能变化和动态特性规律，实验测试系统的动态特性规律。项目的顺利实施将为太阳能喷射制冷系统的推广应用提供理论参考，具有重要的理论意义和工程应用价值。

太阳能制冷是未来可再生能源利用的重要方式，喷射式制冷系统是其应用系统形式之一。本项目在揭示喷射器及气液喷射泵的热力学机理的基础上，建立了描述其工作过程的热力学模型；通过对喷射制冷系统的高级㶲分析指出系统改进的方向；对制冷系统进行了成本分析、热经济学分析及多目标优化，多角度优化了系统运行参数和工质；最后通过建立系统换热器和喷射器耦合的动态模型，基于simulink模拟研究了喷射制冷系统性能的动态变化特性。研究结果表明，对于以水为工质的喷射制冷系统，汽液喷射泵可有效替代循环泵将冷凝液输送回发生器；喷射制冷系统有30%左右的㶲损失是可避免的，喷射器中可避免的㶲损失占比接近50%，有较大的可提升空间；制冷成本在使用不同制冷剂时有较大差别，使用制冷剂R123的制冷成本高出了R717的180.50%，对于所研究的5种制冷剂，无论质量流速如何，蒸发温度和冷凝温度均存在最优值使制冷成本达到最小值，而发生温度越低，其制冷成本越低。系统产品的单位㶲经济学成本和㶲经济系数，则随蒸发温度和发生温度的上升呈现单调递增性，随冷凝温度的上升递减，制冷剂R123的数值一直最高；无论在哪种工况温度条件下，制冷剂R123的㶲经济系数一直是最高的，而㶲经济系数最低的制冷剂种类随工况温度不同而不断改变；综合系统的性能系数COP、㶲损失ED和投资成本COST的多目标优化研究结果表明，各制冷剂的最优蒸发温度在10~11℃，最优冷凝温度在32~33℃，最优发生温度不超过84℃；通过改变工质泵转速、电子膨胀阀开度、冷冻水温度、冷却水温度和发生器热媒温度发生阶跃变化时系统的动态响应，研究了蒸发压力、冷凝压力、喷射系数等关键值的动态响应。项目的研究成果对研制性能优异的喷射制冷系统及对喷射制冷系统自动控制策略的制定有一定的理论意义和实用价值。