基于双流体的喷射制冷系统性能研究

Ejector refrigeration is one of the most promising technologies, but it has very low thermal efficiency. A new ejector refrigeration system (NERS) with binary fluids is presented in this project, in which the traditional ejector refrigeration system (TERS) using a same fluid has been changed. Owing to the characteristics of the ejector refrigeration with binary fluids and of wet compression of ejector, it makes possible to increase refrigeration efficiency in NERS, and furthermore to use air cooling condenser to extend the application of ejector refrigeration. For a working pair R245fa/R600a, the working fluid R245fa at the throat of the ejector is utilized to entrain refrigerant R600a exiting from the evaporator. The comparision between NERS and TERS is conducted under the same operation condition, the calculation results show that coefficient of performance (COP) of NERS can be increased by more than 50% compared with that of TERS. As the most important component, the design of ejector is crucial to influence the performance of the whole system. A new numerical method of modeling ejector is presented, which is based on the thermophysical properties, vapor-liquid equilibrium characteristics and mixture heat model of fluids. According to this method, the numerical calculation of an ejector with two phase high speed flow is performed and the design is subsequently made. Approach on sieving principle of binary fluids is proposed, and the corresponding optimum composition is determined. In this project, theoretical calculations and experiments of a ejector refrigeration system with binary fluids are conducted to indicate that NERS has several advantanges over already known TERS when driven by low grade thermal energy, it meets the requirements of energy conservation and environmental protection.

喷射制冷是一种很有发展前途的制冷方式，但效率偏低。本项目提出了基于双流体的喷射制冷系统，改变了传统喷射制冷喷射器中工作流体和引射流体是同类流体的状况。利用双流体喷射制冷和喷射器适应湿压缩的特点，给出了新的喷射制冷系统，实现了风冷冷凝方式，扩大了喷射制冷的适用范围,并提高了制冷效率；以R245fa/R600a 工质对为例，用R245fa作为工作流体，通过喷射器引射制冷工质R600a，经前期理论模拟计算，新系统较常规喷射制冷系统在相同工况下，制冷COP 可提高50%以上；喷射器是喷射制冷循环的关键部件，根据流体的热物性、相平衡特性和混合热模型，提出一种新的喷射器数值计算方法，完成高速两相流动喷射器的数值计算和设计；确定双流体工质对筛选原则和溶液的最佳配比；对喷射制冷系统变工况性能进行模拟计算和实验研究，以低品位热源作为驱动热源，证实基于双流体的喷射制冷系统的优越性，满足节能和和环保两大主题。

喷射制冷是一种很有发展前景的制冷技术，它可以利用低品位热制取冷量，但是其效率偏低。双流体喷射制冷系统能有效提高喷射制冷系统的性能。项目提出了双流体喷射制冷系统和喷射器的设计计算方法。选用R134a/R32工质对，将双流体喷射制冷系统与常规单级、双级喷射制冷系统进行对比研究，结果表明，在相同的工况下，双流体喷射制冷系统的COP比常规单级系统高28％-65％，并且新系统在较低蒸发温度下有更优越的性能；双流体喷射制冷系统在蒸发温度较低的工况下性能劣于常规双级喷射制冷系统，在蒸发温度较高的工况下，双流体喷射制冷系统性能优于常规双级喷射制冷系统。双流体喷射制冷系统COP随着发生温度和蒸发温度的升高而升高，随着冷凝温度的升高而降低。研制了双流体喷射制冷系统实验台，能单独运行单级喷射制冷循环和双流体喷射制冷循环。实验结果表明在相同的工况下，R32单级喷射制冷系统性能比R134a单级喷射制冷系统好，与理论研究结果相符；在相同工况下，双流体喷射制冷系统性能比单级喷射制冷系统的性能高。以低品位热源作为驱动热源，用理论和实验的方法验证了双流体喷射制冷系统的优越性。本项目基于双流体的喷射制冷系统性能研究的成果具有重要的学术价值和工程实际意义。