Usually according to the standard evaporation temperature of refrigerant, it is divided into high, medium and low temperature. The standard evaporation temperature refers to the evaporation temperature under standard atmospheric pressure, that is, the boiling point.
Low-pressure high-temperature refrigerant: the evaporation temperature is higher than 0℃, and the condensing pressure is lower than 29.41995×104Pa. This type of refrigerant is suitable for centrifugal refrigeration compressors in air conditioning systems.
Medium pressure medium temperature refrigerant: Evaporation temperature -50 ~ 0 ℃, condensing pressure (196.113 ~ 29.41995) × 104Pa. This type of refrigerant is generally used in ordinary single-stage compression and two-stage compression piston refrigeration systems.
High-pressure low-temperature refrigerant: the evaporation temperature is lower than -50℃, and the condensing pressure is higher than 196.133×104Pa. This type of refrigerant is suitable for the low temperature part of the cascade refrigeration device or the low temperature device below -70 ℃.
Refrigerant R404a is a mixed refrigerant, which is composed of 44% R125, 4% R134A, and 52% R143A. Two refrigerants cannot be mixed. R22 is a primary refrigerant, and R404a is a mixed secondary refrigerant. The boiling point and pressure are different from azeotropic and non-azeotropic. The ODP of the refrigerant is 0, and the GWP is 4540.
The discharge pressure of R404A refrigerant is about 1.2 times that of R22, and the mass flow is about 1.5 times that of R22. The exhaust flow rate increases and the resistance increases. Generally speaking, the heat exchange capacity of the condenser is increased by 20% to 30% than R22.
R404A is a non-azeotropic mixture working fluid. The component concentration of the non-azeotropic mixture changes with temperature and pressure. This brings certain difficulties to the production, debugging and maintenance of the refrigeration system, and also has a certain impact on the heat transfer performance of the system. , Especially when the refrigerant leaks, the system refrigerant is recommended to be completely emptied and replaced, so as to ensure the proportion of each mixed component and achieve the designed refrigeration effect.
Refrigerant R404a temperature and pressure comparison table