Vapor-liquid separation technology in refrigeration/heat pump systems

doi:10.16085/j.issn.1000-6613.2022-1004

Abstract

Abstract:

The vapor compression refrigeration/heat pump systems realize heat transfer by using vapor-liquid phase change. The application of vapor-liquid separation technology has always been a research focus, in order to control the degree of dryness and mass flow distribution of the two-phase refrigerant to ensure the stability and improve the performance of the systems. In this paper, the research status of vapor-liquid separation technology in vapor compression refrigeration/heat pump systems is reviewed. The application modes of vapor-liquid separation technology are summarized, the main functions and working mechanisms of different application modes are discussed. Finally, the key research directions are prospected. It is found that the main functions of vapor-liquid separation technology included ensuring the reliability of systems, improving the performance of heat exchangers, separating components of zeotropic mixture refrigerant, and improving the circulation process. However, the existing research is not paid enough attention to the performance improvement of vapor-liquid separators. CFD simulation technology is an effective method to study the internal separation mechanism and optimize the structure of vapor-liquid separators. The development of application modes of vapor-liquid separation technology, the optimization research of phase separation heat exchangers and the design optimization of vapor-liquid separators will become the key research directions in the future.

Key words: refrigeration/heat pump system, vapor-liquid separation, application mode, working mechanism, performance optimization

摘要：

蒸气压缩制冷/热泵系统利用气液相变实现热量转移，如何应用气液分离技术对两相工质进行干度调控与流量分配，保证系统运行稳定性并提高系统性能一直是研究的热点。本文综述了蒸气压缩制冷/热泵系统中气液分离技术的研究进展，总结了系统中气液分离技术的应用方式，讨论了不同应用方式中该项技术的主要功能与工作机制，并对重点研究方向进行展望。研究发现气液分离技术的主要功能有保障系统运行可靠性、提高换热器性能、对非共沸混合工质进行组分分离以及改进循环流程等，对气液分离器性能提升方面现有的研究尚有不足，计算流体动力学（CFD）仿真模拟是研究其内部分离机理和对气液分离器进行结构优化的有效方法。气液分离技术应用方式的开发、相分离换热器优化研究与气液分离器的设计优化将会成为今后研究的重点方向。

关键词: 制冷/热泵系统, 气液分离, 应用方式, 工作机制, 性能优化

CLC Number:

TB657.7

WU Heng, LI Yinlong, YAN Gang, XIONG Tong, ZHANG Hao, TAO Kui. Vapor-liquid separation technology in refrigeration/heat pump systems[J]. Chemical Industry and Engineering Progress, 2023, 42(3): 1129-1142.

吴恒, 李银龙, 晏刚, 熊通, 张浩, 陶骙. 蒸气压缩制冷/热泵系统中的气液分离技术[J]. 化工进展, 2023, 42(3): 1129-1142.

Figures/Tables 15

气液分离器位置	主要技术	重力式	离心式	过滤式	惯性式	精馏式
压缩机前	传统气液分离器	√	√		√
	再循环蒸发器	√
	喷射器增效循环	√	√
冷凝器内	分液冷凝器	√		√	√
冷凝器后	高压储液器	√
	自复叠循环	√				√
	多蒸发温度制冷循环	√	√
膨胀阀间	补气增焓循环	√	√		√
	多级压缩循环	√
蒸发器前	气体旁通蒸发技术	√		√	√
蒸发器内	气体旁通蒸发技术	√		√
	新型蒸发传热强化技术	√

2≤G(g/s)≤5

0.5≤x≤0.65

η = 11908.41 d D 1.46 R e m - 0.64 W e - 0.17 8.59 < R e m < 22.65 R e m = G d A μ 1 + x ρ l ρ g - 1

Mo等^[27]（2014）

空气/水

1≤u_g(m/s)≤30

0.0015≤u_l(m/s)≤0.2

η = 99.84 - 0 . 97 W e (4.42 < R e < 44.23) η = 59.76 + 0.049 W e (R e = 176.91) η = 33.55 + 0.33 W e - 9.91 × 10 - 4 W e 2 (R e = 294.9) η = 21.45 + 0.16 W e - 1.56 × 10 - 4 W e 2 (R e = 589.70)

陈雪清等^[28]（2014）

空气/水

4≤u_g(m/s)≤34

0.006≤u_l(m/s)≤0.125

η = 25 + u g ρ g g σ l ρ l - ρ g 4 - 0.5 W e 6 + 4 × 10 - 19 u 1 ρ l d 0 σ l 0.16 - 0.1

作者

工质

工作应用范围

分液效率关联式

Li等^[22]（2021）

R134a

2≤G(g/s)≤5

0.5≤x≤0.65

η = 11908.41 d D 1.46 R e m - 0.64 W e - 0.17 8.59 < R e m < 22.65 R e m = G d A μ 1 + x ρ l ρ g - 1

Mo等^[27]（2014）

空气/水

1≤u_g(m/s)≤30

0.0015≤u_l(m/s)≤0.2

η = 99.84 - 0 . 97 W e (4.42 < R e < 44.23) η = 59.76 + 0.049 W e (R e = 176.91) η = 33.55 + 0.33 W e - 9.91 × 10 - 4 W e 2 (R e = 294.9) η = 21.45 + 0.16 W e - 1.56 × 10 - 4 W e 2 (R e = 589.70)

陈雪清等^[28]（2014）

空气/水

4≤u_g(m/s)≤34

0.006≤u_l(m/s)≤0.125

η = 25 + u g ρ g g σ l ρ l - ρ g 4 - 0.5 W e 6 + 4 × 10 - 19 u 1 ρ l d 0 σ l 0.16 - 0.1

作者	制冷剂	容量/模式	气液分离器类型	主要结论
Elbel等^[31]（2004）	R744	9~13kW/制冷	重力式	R744的传热系数在干度大于0.5后下降明显，气体旁通可降低蒸发器内平均干度，使得传热系数增大140%，蒸发器压降减小35%
Tuo等^[33]（2012）	R134A	1.81~2.92kW/制冷	惯性式（T型管）	气体旁通使过热区域传热面积减小，改善制冷剂分布均匀性，气体旁通适用于压降大且制冷剂分布不均匀的蒸发器
Shikazono等^[34]（2010）	R410A	4~16kW/制冷	过滤式（金属微槽）	所用气液分离器在体积为传统气液分离器的1/7时，即可使蒸发器的压降相较于传统制冷循环下降50%以上
Fan等^[32]（2020）	R410A	1.9~5.3kW/制热	重力式	制热模式下，蒸发器入口干度较小，可将气液分离器放在蒸发回路中；压缩机频率为60Hz时，气体旁通可以使蒸发器压降减小36.9%，制热能力提升7.1%，气体旁通适用于容量更大的系统
Fan等^[35]（2021）	R32	4~10kW/制热	过滤式（金属微槽）	气体旁通使蒸发器压降减小25.6~84.6kPa，蒸发器熵产减小3.1%~25.3%，气液分离器相对位置、蒸发器回路数等会对气体旁通蒸发器的性能产生影响

作者	制冷剂	应用工况	气液分离器的应用方式	主要结论
Fan等^[67]（2021）	R32	结霜除霜	气体旁通蒸发器	蒸气旁通减小蒸发器压降，使结霜质量降低9.67%，平均加热能力提高7.0%
Han等^[68]（2022）	R410A	结霜除霜	压缩机前气液分离器	将电子膨胀阀开度调小后，可以在防止湿压缩现象的同时最大限度地提高除霜性能
Ma等^[69]（2022）	R410A	结霜除霜	气液分离器与高压储液器组合，实现热交换	吸气与高温流体进行热交换，提升回气温度，可使结霜时间延缓约30min
Qin等^[70]（2021）	R1234yf/R41/R14 (0.64/0.17/0.19)	低温制冷	三次组分分离以提高低沸点工质纯度	通过三级自复叠循环实现-100℃低温制冷，COP为0.2713
Liu等^[71]（2021）	R290/R170（0.5/0.5）	低温制冷	附加气液分离器改进自复叠循环	通过辅助分离器使更多的低沸点工质进入蒸发器，使自复叠循环COP提高16.1%
Wang等^[72]（2015）	R22、R290、R32	低蒸发温度制热	喷射器增效改进闪蒸器补气增焓循环	R22、R290和R32的单位容积加热量分别提高6.0%~8.4%、7.3%~10.2%和6.7%~8.2%
Zhu等^[73]（2018）	CO₂	高温制热	气液分离辅助喷射器增效循环	通过喷射器增效回收膨胀功，出水温度为90℃时其COP可达3.3
Zhang等^[74]（2022）	R245fa	高温制热	二级压缩结合多级闪蒸器补气增焓循环	在冷凝温度为125℃时，与传统闪蒸器补气增焓循环相比，其COP提高18.05%
Feng等^[75]（2021）	R134a	频繁启停	热交换气液分离器，将部分高压液罐盘绕在气液分离器内	系统启动时，通过热交换可以使停机时储存在气液分离器内的制冷剂迅速蒸发，使启动时间缩短54.76%，平均COP增加13.84%

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