The Secret of Refrigeration System: Liquid Mirror, How much do you know?

November 20, 2023

First, what is a liquid mirror?


The sight glass is installed between the condenser and the throttle to observe the state of the liquid refrigerant, and can also judge the quality of lubricating oil and the water content in the refrigerant from the color of the liquid. In addition, technicians can also judge whether the refrigerant circulation in the system is normal and whether there are other problems such as blockage or insufficient refrigerant by observing the flow in the sight glass, which can help technicians find and solve problems quickly.


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Second, why does the refrigeration system need a liquid mirror?


There are several important reasons for using the sight glass in the refrigeration system:


1. Judge the working state of the refrigeration system: the refrigerant will change from gas to liquid in the refrigeration cycle, and whether there are bubbles in the refrigerant of the system can be observed through the mirror. If the liquid is full, it means that the refrigerant charge is normal; If there are bubbles, the number and quantity of bubbles can help to judge the state of the unit, such as whether there is a lack of refrigerant and whether it is blocked.


2. Humidity indication of refrigeration system: The indicator element in the center of the visual liquid mirror is highly sensitive to moisture. Therefore, through the visual liquid mirror, the condition of refrigerant in the liquid pipeline in the refrigeration device and the moisture content in the refrigerant can be observed, and the indicator of the visual liquid mirror gradually changes color with the change of moisture content in the system. In addition, the sight glass is also used to observe the flow of lubricating oil from the oil separator in the oil return pipeline.


Liquid mirror indicator status:


Green: indicates that the refrigeration system does not contain dangerous water vapor.


Yellow: indicates that the water vapor content in the liquid pipeline of the refrigeration system is too high.


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3. Monitoring the operation of the refrigeration system: By observing the liquid flow in the sight glass, technicians can monitor the operation of the refrigeration system. If the liquid flow is abnormal or unstable, it may mean that there are faults or other problems in the refrigeration system, which need further inspection and repair.


Third, the choice of high-quality liquid glasses


The following factors need to be considered when choosing a high-quality goggles:


1. Material: The material of the goggles should have corrosion resistance, high pressure resistance, high transparency and high wear resistance. Common materials include glass, copper and stainless steel.


2. Visual field: The liquid scope should provide a clear visual field, which is convenient for the operator to observe the liquid flow and judge the system state.


3. Safety: The goggles should have safety performance, be able to withstand the high pressure and high temperature environment in the system, and avoid safety accidents caused by problems such as rupture or falling off of the goggles.


4. Scope of application: Liquid goggles should be suitable for different types of refrigeration systems, including conventional refrigerants and CO, etc.


Last but not least, choose a well-known brand of goggles. A well-known brand of goggles often means higher quality and more reliable performance.



Shanghai KUB Refrigeration Equipment Co., Ltd.
Address : No. 328 on the 4th plant hengyong Road, Jiading District, Shanghai
Factory Address : No. 328 on the 4th plant hengyong Road, Jiading District, Shanghai
Work Time : 8:30-17:30(Beijing time)
Phone :

86-021 -63184860-17(Work Time)

86--13916495206(Nonworking time)

Fax : 86-021-53750132
Email :


Customer Manager
Mr mick Cai
Phone : +86 13588563336
WhatsApp : +86 13588563336
Skype : kub.mick
WeChat : CP9301
Email :
Miss. Mophy Mao
Phone : +86 15001938306
WhatsApp : +86 15001938306
WeChat : kub-maomao
Email :


Mr Peter Huang
Phone : +86 15317830025
WhatsApp : +86 15317830025
Skype : kub-peter
WeChat : Shkub_01
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