精馏型自复叠制冷系统回热器混合位置影响类型

The Influence Types of the Mixing Position in the Recuperators of an Auto-Cascade Refrigerator Operating With a Rectifying Column

本文通过两种典型工况下的数值模拟,深入分析了精馏型自复叠制冷系统的回热器混合位置对循环性能的两种影响类型,并在自行搭建的实验台上进行了实验验证。理论分析和实验结果均表明,回热器中存在混合位置的稳定区域和不稳定区域,其内部高低压制冷剂的温度分布和夹点的位置与精馏柱底流出的工质流量密切相关,该工质流量对系统性能的影响存在两种类型。当精馏柱底流出工质流量较大时,夹点通常出现在整个回热器的冷端或中间部分,一般可以得到较大的制冷量,或实现较低的制冷温度。由于这种类型的稳定区域较小,混合位置的变化对系统性能影响较大。当精馏柱底流出工质流量较小时,夹点通常出现在整个回热器的热端部分,制冷量较小,或制冷温度较高。但由于这种类型的稳定区域大大增加,混合位置的变化对系统性能影响较小。

Based on two case studies, the paper simulated two influence types of the mixing position of the low pressure refrigerants in recuperators of an auto-cascade refrigerator operating with a rectifying column. Tests have been conducted on a purpose-built experimental setup to verify the impact of the mixing position on the performance of the refrigerator. The theoretical and experimental results showed that the stable and unstable regions can be found along the recuperators. The temperature profiles of the low and high pressure refrigerants in the recuperators as well as the position of the pinch point are strongly affected by the flowrate of the refrigerant flown from the bottom of the rectifying column. The influence of the mixing position on the performance of the refrigerator can be divided into two types. When the flowrate is large, the pinch point usually exits at the middle or the cold end of the recuperator, and large cooling capacity or low refrigerating temperature can be obtained. The performance of the refrigerator is apt to be affected by the location of the mixing position in this type due to the relatively narrow region of the stable region. When the flowrate is low, the pinch point usually exits at the hot end of the recuperator, and only low cooling capacity or high refriger- ating temperature can be obtained. But the performance of the refrigerator is not apt to be affected by the location of the mixing position in this type due to the relatively broad region of the stable region.