带喷射器的跨临界CO_(2)热泵系统仿真研究

Simulation Study of Trans-critical CO_(2) Heat Pump System with Ejector

利用自行搭建的跨临界CO_(2)热泵实验台对系统的整体热力性能进行了相关的实验研究,分析比较了气冷器CO_(2)出口温度、蒸发温度对跨临界CO_(2)热泵系统(SBC)制热系数(C_(oph))的影响。在此基础上建立了带喷射器的跨临界CO_(2)热泵系统(SEC)对应的热力学模型,利用Matlab编写系统循环程序,对系统性能进行数值模拟,分析当改变工作流体压力、工作流体温度和蒸发温度等参数时,喷射系数、喷射器出口工质干度和C_(oph)的变化规律。结果表明:仿真值与实验值较为吻合,建立的系统热力学模型准确性高;在工作流体温度由31℃升高到38℃时,SEC的最大C_(oph)比SBC的最大C_(oph)高出24.8%;在蒸发温度由5℃升高到13℃的过程中,SEC的最大C_(oph)比SBC的最大C_(oph)高出28%,喷射器大大减少了CO_(2)工质在膨胀过程中所产生的节流损失,对系统性能的提升有显著作用。

A self-built trans-critical CO_(2)heat pump system was used to carry out thermal performance experimental study,and the influence of CO_(2)outlet temperature and evaporation temperature on the heating coefficient(C_(oph))of a trans-critical CO_(2)heat pump system(SBC)was analyzed and compared.On this basis,the corresponding thermodynamic model of the trans-critical CO_(2)heat pump system with an ejector(SEC)was established.The system cycle program was written by Matlab,and the system performance was numerically simulated.The variation of injection coefficient,working medium dryness and C_(oph)at ejector outlet was investigated with the change of working fluid pressure,working fluid temperature,evaporation temperature and other parameters.Results show that the simulation value is in good agreement with the experimental data,and the established system thermodynamic model has high accuracy.When the working fluid temperature increases from 31℃to 38℃,the maximum C_(oph)of SEC is 24.8%higher than that of SBC.While the evaporation temperature increases from 5℃to 13℃,the maximum C_(oph)of SEC is 28%higher than that of SBC.The ejector greatly reduces the throttling loss caused by CO_(2)working medium in the expansion process and plays a significant role in improving the system performance.