Freon in commercial refrigeration
Freon in commercial refrigeration
Freon refrigerant in commercial refrigeration has the following commonality.
①Non-toxic, good thermal and chemical stability, and can adapt to different cooling temperature and cooling capacity requirements.
②The molecular weight is large, the specific gravity is large, and the heat transfer performance is poor.
③The adiabatic index is small and the final compression temperature is relatively low.
④It is very corrosive to metal materials, but it is corrosive (swelling) to non-metal materials such as natural rubber, resin, and plastic.
⑤ Poor water solubility, the system needs to strictly control the water content to prevent ice blocking or corrosion due to hydrolysis of acidic substances.
6 When exposed to an open flame, it will decompose hydrogen fluoride, hydrogen chloride or phosgene which is toxic to the human body, so open flames are strictly prohibited in the production and use places.
⑦ is odorless and has strong permeability, so it is easy to leak in the system, and the leak is not easy to be detected.
usually use halogen lamps or electronic halogen leak detectors for leak detection. The other physical and chemical properties of Freon in commercial refrigeration have certain regularity: those with more H atoms are highly flammable; those with more Cl atoms are toxic; those with more F atoms have good chemical stability; fully halogenated hydrocarbons are present. It has a long life in the air. Mclinden (Mclinden) and Didion (Didion) described the above-mentioned law with a triangle diagram. The most powerful effect on ozone destruction is Freon which contains chlorine atoms (and bromine atoms) and has long atmospheric life. CFC Class is a typical among them, becoming the first batch of refrigerants to be eliminated. Their replacement must consider GWP and safety at the same time. For example, the European Parliament stipulates that the GWP of refrigerants used in car air conditioners should be less than 150b. Safety includes toxicity and flammability, and flammability is considered in the same way as hydrocarbons.
1. R22 (CHFzCl) and R22's substitute R22 are HCFC substances
The environmental index ODP is 0.05, the GWP is 1810, and the safety level is Al. The standard evaporation temperature of R22 is =40.8℃, and the solidification temperature is -1160℃. Its saturation pressure characteristic is similar to ammonia, and its cooling capacity per unit volume is also similar to ammonia. The final compression temperature is not as high as that of ammonia, but it is high in the Freon category. If it works under high pressure, the compressor must take cooling measures. The solubility of water in R22 is only 0.06% (Wt). Excessive water content in the system may cause ice blockage and corrosion in commercial refrigeration ( copper plating ). Therefore, it is stipulated that the moisture content of R22 products is limited to 25ppm or less. The refrigeration system must pass through a strict dry place before charging with refrigerantTreatment (drying if necessary); The system is equipped with a dryer to absorb the water that penetrates into the system during operation at any time. The dryer should be replaced in time according to the moisture content indicated by the moisture observation glass, or the desiccant should be regenerated. R22 is a polar molecule and has a strong swelling effect on organic matter. The seals of the system should be made of fluorine-resistant materials such as chlorohydrin rubber or CH-l-30 rubber, polytetrafluoroethylene. R22 has limited dissolution with lubricating oil. On the high temperature side of the system, R22 and oil are completely dissolved; on the low temperature side, when the mixture of R22 and oil is below the dissolution critical temperature, the liquid in the evaporator or low pressure reservoir will be stratified, the upper layer is mainly oil, and the lower layer is mainly R22 , So there must be special oil return measures. In order to ensure smooth oil return, the dry evaporator generally adopts R22 up and down ; the refrigerant in the pipe must have sufficient flow rate; especially for the rising return gas riser, the minimum oil-carrying speed must be considered when designing the pipe diameter . In addition, an oil separator should be installed on the compressor exhaust pipe to minimize the oil brought into the system from the compressor during operation. The ODP of R22 is greater than zero and is a transitional substance. R410A is the currently used alternative. R410A (R32/125, 50/50) is a near-azeotropic mixed refrigerant, ODP=0, GWP=2100, safety level Al. The standard boiling point of R410A is -52.5℃, and the phase transition slip temperature is 0.2℃. The maximum pressure in the cycle is obviously greater than R22, about 50% higher, and the minimum pressure is also higher than R22, so the unit volume refrigeration capacity is large, the compressor required for the same refrigeration capacity is small, and the required pipe diameter is also small. In order to adapt to the high pressure in commercial refrigeration, the system using R410A must be redesigned. Theoretically, the COP of the R410A refrigeration cycle is lower than R22, but its heat transfer performance is very good. After optimized design, its COP is slightly higher than the device using R22. R410A has a larger GWP than R22, which is its disadvantage. Long-term alternatives to R22 that can be considered are: R161 (GWP=12, safety level A3), R290 (GWP-20, safety level A3), R32 (GWP-1675, safety level A2) and ammonia.
Company website: www.ihdjx.com Free order hotline: +86 18019567573 Contact: Mr. Shao 26066250@qqn n3
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