What is the difference between the R22 and R404A cold storage systems?

In the past, many R22 refrigerators used R22 refrigeration, but now more and more R404A refrigerant is used, so why do cold storage use relatively high R404A refrigerant?What is the difference between the R22 and R404A cold storage systems?
First of all, R22 refrigerant is a non-environmentally friendly refrigerant, and developed countries in Europe and America have been eliminated from use.Although R404A GWP refrigerant is high, not a really environmentally friendly refrigerant, but relatively R22 is more environmentally friendly.In addition, the latent heat of R404A refrigerant is larger than R22, the thermal efficiency and refrigeration efficiency are higher, the system circulation volume is small, the filling amount is less than R22, the refrigeration speed is faster than R22, and the corresponding temperature under the same pressure is lower than R22. Therefore, many refrigeration equipment is used in cold storage with R404A refrigerant.

R22 and R404A cold storage system differences

1, R404A cold storage system and lubricating oil itself are very soluble with water, so the requirements for water and residues and cleanliness of the system are improved compared with the R22 cold storage system. Water control and impurity control of R404A system are a relatively important index, and the corresponding filter device in the system should be changed.
2, R404A cold storage system is about 1.2 times that of R22, the mass flow rate is about 1.5 times that of R22, and the exhaust flow rate increases and the resistance increases.In general, the condenser has a heat exchange capacity of 20% ~ 30% greater than the R22.
3,The saturation temperature of R404A cold storage system at the same temperature is different from R22, so the action mechanism of R404A thermal expansion valve is different from that of R22.At the same time, due to the R404A refrigerant and the solvent of lubricant to the different sealing materials, the sealing materials of the expansion valve should also be changed accordingly. Therefore, the R404A special expansion valve should be selected in the selection of thermal expansion valve.
4, Due to the high saturation pressure of R404A cold storage system than R22, the higher pressure vessel pressure resistance in the system, such as reservoir and gas-liquid separator.The safety valve and fuse setting value installed on the system accessories should also be changed accordingly.Since the gas density of R404A is about 50% greater than R22 under the same exhaust amount, the pipe diameter is larger than R22 using the R404A cold storage system.
5, The same compressor, the current of the R404A cold storage system should be greater than R22,, so the line diameter of the AC contactors, heat relays and cables of the compressor shall be adjusted.For system protection, the high pressure pressure switch set is adjusted from 2.45MPa to 2.7MPa.
6, Because the saturation pressure of the 404A cold storage system is different from R22, the air tightness test pressure is greater than R22. The vacuum is higher than R22, water content is lower than R22. The refrigerant shall be filled in liquid form to prevent the R404A configuration changes.
7, R404A is non-coboiling mixed work quality, the composition concentration of non-coboiling mixture varies with temperature and pressure, which brings certain difficulties to the production, debugging and maintenance of the refrigeration system, will also have a certain impact on the system heat conduction performance, especially when the refrigerant leakage, the system refrigerant needs to be completely replaced, so as to ensure the proportion of the mixed components, and to achieve the design refrigeration effect, otherwise it will get worse and worse.
The 8, R404A cold storage system, different from R22 lubricating oil, must be replaced by R22 with PVE ester oil.Eester lubricating oil and water have high affinity and poor dehydration, so contact with external air should be avoided as far as possible in use. The container shall be used as soon as possible, sealed, stay away from oxidant, strong alkali and strong acid and kept in well ventilated place; avoid contact with skin and eyes and vapor and spray.