Types of refrigerants and leak detection methods
Refrigerants are also called refrigeration working fluids, commonly known as refrigerants in some areas in the south. It is a working substance that continuously circulates in the refrigeration system and achieves refrigeration through its own state changes. The refrigerant absorbs the heat of the cooling medium (water or air, etc.) in the evaporator and vaporizes, and transfers the heat to the surrounding air or water in the condenser to condense.
Types of refrigerants:
1. Inorganic compounds. Water, ammonia, carbon dioxide, etc.
2. Derivatives of saturated hydrocarbons, commonly known as Freon. Mainly methane and ethane derivatives. R22, R134a, etc.
3. Saturated hydrocarbons. Such as propane, isobutane and so on.
4. Unsaturated hydrocarbons. Such as ethylene, propylene, etc.
5. Azeotropic mixed refrigerant. Such as R502 and so on.
6. Non-azeotropic mixed refrigerant. Such as R407c, R410 and so on.
Usually according to the standard evaporation temperature of the refrigerant, it is divided into three categories: high, medium and low temperature. Standard evaporation temperature refers to the evaporation temperature under standard atmospheric pressure, that is, the boiling point.
Low pressure and high temperature refrigerant:
The evaporation temperature is higher than 0℃, and the condensation pressure is lower than 29.41995×104Pa. This type of refrigerant is suitable for centrifugal refrigeration compressors of air conditioning systems.
Medium pressure and medium temperature refrigerant:
Medium pressure and medium temperature refrigerant: evaporation temperature -50~0℃, condensation pressure (196.113~29.41995)×104Pa. This type of refrigerant is generally used in common single-stage compression and two-stage compression piston refrigeration systems.
High pressure and low temperature refrigerant:
High-pressure low-temperature refrigerant: the evaporation temperature is lower than -50°C, and the condensation pressure is higher than 196.133×104Pa. This kind of refrigerant is suitable for the low temperature part of cascade refrigeration equipment or low temperature equipment below -70℃.
How to detect refrigerant leakage?
1. Visual inspection: When oil stains are found somewhere in the system, this may be a leakage point. There are big defects. Unless the system suddenly breaks and the system leaks a large leak and the system leaks liquid colored media, visual inspection cannot be located because the leak is usually very small and many parts of the refrigeration system are almost invisible.
2. Bubble water or soapy water leak detection: Fill the system with 10-20kg/cM2 pressure nitrogen, and then apply soapy water to all parts of the system. The bubbling point is the leakage point. This method is the most common leak detection method used by maintenance workers, but the human arm is limited, the human vision is limited, and often no leaks can be seen at all.
3. Nitrogen water leak detection: Fill the system with 10-20kg/cm2 pressure nitrogen, immerse the system in water, and the bubbling point is the leakage point. This method has obvious disadvantages: the water used for leak detection is easy to enter the system, causing the materials in the system to be corroded. At the same time, the high-pressure gas may also cause greater damage to the system, and the labor intensity of leak detection is also great.
4. Fluorescence leak detection: It uses the principle that fluorescent leak detection agent emits bright yellow and green light under the irradiation of ultraviolet/blue leak detection lamp to detect fluid leakage in various systems. When in use, you only need to add fluorescent agent in a certain proportion to the system. After the system runs for 20 minutes, put on special glasses and illuminate the outside of the system with a leak detection lamp. The leak will show yellow fluorescence.
V. Gas differential pressure leak detection: The pressure difference between the inside and outside of the system is used to amplify the pressure difference through the sensor, and the leak detection result is expressed in digital, sound or electronic signals. This method can only "qualitatively" know whether the system is leaking and cannot accurately find the leak.
6. Halogen lamp leak detection: Ignite the leak detection lamp and hold the air tube on the halogen lamp. When the nozzle is close to the system leakage, the flame color changes to purple blue, which means that there is a large amount of leakage. This method produces open flames, which is not only dangerous, but the combination of open flames and refrigerants will produce harmful gases, and it is also difficult to accurately locate leaks.
7. Electronic leak detector for leak detection: Electronic leak detector is a reliable leak detector. Because of its accuracy in leak detection, it has quickly occupied the market in recent years. When using it, move the probe against the place where leakage is possible. When the device sounds an alarm, it indicates that there is a leak. Leak detection with an electronic leak detector is currently the most scientific, simple and fast leak detection method.
