CO_2跨临界循环中膨胀过程的对比与分析

COMPARISON STUDY AND ANALYSIS OF EXPANDING PROCESS IN CO_2 TRANSCRITICAL CYCLE

本文对于CO_2超临界流体的等嫡膨胀和等焓膨胀过程进行了热力学分析、计算和对比,发现等熵膨胀过程与等焓膨胀相比,增大了有效制冷量,增大的数值略大于所回收的膨胀功。而且对于减小节流损失的回热循环和膨胀机循环进行了分析和对比,对于选用原则给出了具体的判定方法。本文还进行了膨胀机中膨胀过程的热力学分析,分别得出了超临界区和两相区的膨胀功来源,及变化规律。经分析,本文作者认为可以采用“闪蒸破碎模型”简化汽液两相流绝热膨胀基本特性方程。最后,本文对膨胀机实际工作的不可逆因素进行了分析。

The isentropic and isenthalpic expanding processes of in CO2 transcritical cycle were analyzed and compared thermodynamically. We find that the effective refrigeration capacity of the cycle with isentropic expanding process is higher than the cycle with isenthalpic expanding process. The increment is slightly larger than the recovered expanding power because of the transcritical cycle. More over, two methods-applying internal heat exchanger and using expander instead of throttling valve, which can decrease the throttling loss were compared and analyzed. As a result, the application principle was provided. In addition, the expanding power resource and its changing rule were thermodynamically analyzed and calculated. Furthermore, the irreversibility factors of the real expander working process were analyzed.