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Confirmation and prevention of vapor bypass in absorption heat pump with U-pipe pressure separation device caused by upward side two-phase flow
International Journal of Refrigeration ( IF 3.9 ) Pub Date : 2021-06-15 , DOI: 10.1016/j.ijrefrig.2021.06.014
Chaoyi Zhu , Xiaoyun Xie , Yi Jiang

A U-pipe is the key pressure separation device in a lithium bromide absorption heat pump (AHP) connecting the high-pressure condenser and the low-pressure evaporator. A recent study reported that two-phase flow occurs in the upward side of the U-pipe, which reduces the overall density of the fluid and impairs the pressure separation ability of the U-pipe. The liquid seal function of the U-pipe fails, and the vapor can flow directly from the high-pressure condenser to the low-pressure evaporator, causing a vapor bypass problem. This study experimentally investigates the U-pipe vapor bypass mass flow rate under vacuum conditions. The mass flow rate ratio of the bypassed vapor to the main liquid fluid in the U-Pipe can be as high as 10 %. The effect of this bypassed vapor on the AHP performance is investigated through simulations and field tests. The cooling coefficient of performance (COP) drops by 0.05 to 0.1 when vapor bypass occurs, providing evidence for the existence of U-pipe vapor bypass in AHPs. A practical method is suggested to solve this problem and to improve the cooling COP of the AHP by more than 6%.



中文翻译:

U型管分压装置吸收式热泵蒸汽旁流的确认与防止上侧两相流

U型管是溴化锂吸收式热泵(AHP)中连接高压冷凝器和低压蒸发器的关键压力分离装置。最近的一项研究报告说,U 形管向上侧发生两相流,这降低了流体的整体密度,削弱了 U 形管的压力分离能力。U型管的液封功能失效,蒸气可以直接从高压冷凝器流向低压蒸发器,造成蒸气旁通问题。本研究通过实验研究了真空条件下 U 形管蒸汽旁路质量流量。U 型管中旁通蒸汽与主要液体流体的质量流量比可高达 10%。通过模拟和现场测试研究了这种旁路蒸汽对 AHP 性能的影响。当蒸汽旁路发生时,冷却性能系数(COP)下降了 0.05 到 0.1,为 AHP 中存在 U 管蒸汽旁路提供了证据。提出了一种实用的方法来解决这个问题,并将 AHP 的冷却 COP 提高 6% 以上。

更新日期:2021-08-15
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