Performance of Scroll Expander for CO2 Refrigeration Cycle
Performance of Scroll Expander for CO2 Refrigeration Cycle
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发表时间：
2006
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通讯作者：
M. Fukuta;T. Yanagisawa;O. Kosuda;Y. Ogi
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作者：
M. Fukuta;T. Yanagisawa;O. Kosuda;Y. Ogi
由于跨临界二氧化碳制冷循环具有较大的节流损失，通过膨胀机回收节流损失对于改善循环性能是有效的。膨胀机有很多种形式，如涡轮式、旋叶式、螺杆式和涡旋式。其中，涡卷机是性能较好的膨胀机之一。在这项研究中，为了检查涡旋膨胀机的二氧化碳制冷循环的可行性，二氧化碳涡旋膨胀机的性能进行了研究，从理论和实验。由于跨临界CO2制冷循环中膨胀机的泄漏对制冷机的性能影响很大，是膨胀机内从超临界区到两相区的跨临界流动，因此在理论研究中首先讨论了膨胀机跨临界泄漏流量的计算方法。计算结果表明，当泄漏间隙尺寸为10 μm，转速为3600 rpm时，涡旋膨胀机的总效率可达60%左右。另一方面，利用热水器涡旋压缩机的机械元件制作了涡旋膨胀机样机，并对其性能进行了测试。尽管压缩机的涡旋元件没有任何重大修改而使用，但获得了80%的容积效率，并且总效率达到约55%。
Since trans-critical carbon dioxide refrigeration cycles have a large throttling loss, recovering the throttling loss by an expander is effective for improvement of the cycle performance. There are many types of expander such as turbo, rotary vane, screw and scroll. Among them, the scroll machine is one of the expanders having good performance. In this study, in order to examine feasibility of the scroll expander for the carbon dioxide refrigeration cycle, the performance of the carbon dioxide scroll expander is investigated both theoretically and experimentally. Since a leakage in the expander influences its performance greatly and is a trans-critical flow from a supercritical to a twophase region in the expander for the trans-critical carbon dioxide refrigeration cycle, a calculation method of the trans-critical leakage flow rate in the expander is discussed at first in the theoretical study. The calculation results showed that the total efficiency of the scroll expander becomes about 60% when the leakage gap size is 10 μm and the rotational speed is 3600rpm. On the other hand, a prototype of scroll expander was made using a mechanical element of a scroll compressor for a water heater and its performance was measured. The volumetric efficiency of 80 % was obtained and the total efficiency reached about 55 % although the scroll element of the compressor is used without any major modifications.