R22 refrigerant has excellent performance and is widely used in air-conditioning refrigeration and refrigeration ice-making equipment, but it has disadvantages such as destroying the atmosphere and polluting the environment. Now more and more refrigeration equipment such as ice machines and air conditioners use R404A refrigerant. Although R404A and R22 have similar refrigeration performance, there is a big difference in actual use. The difference between the environmentally friendly refrigerant R404a and R22 is as follows:
R22 uses mineral lubricating oil, and R404a uses PVE ester oil. Ester lubricants have high affinity with water and poor dehydration. Therefore, contact with outside air should be avoided as much as possible during use. After the container is opened, it should be used as soon as possible. After use, it must be sealed and stored; Store in a well-ventilated place; avoid contact with skin and eyes, and avoid inhalation of vapor and spray.
2. Exhaust pressure
The exhaust pressure of R404A refrigerant is about 1.2 times that of R22, and the mass flow rate 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 20% to 30% larger than that of R22.
3. Saturation pressure
a. The saturation pressures of R404A and R22 are different at the same temperature, so the operating mechanism of R404A thermal expansion valve is different from that of R22. At the same time, due to the different compatibility of R404A refrigerant and lubricating oil to the sealing material, the expansion valve sealing material should be changed accordingly. Therefore, in the selection of the thermal expansion valve, an expansion valve suitable for R404A refrigerant should be selected.
b. Since the saturation pressure of R404A is higher than that of R22, the design pressure of the pressure vessel in the system must be changed to ensure safety. Such as accumulators and gas-liquid separators. At the same time, the safety valves and fusible plugs installed on the system accessories will also be changed accordingly. Since the gas density of R404A is about 50% greater than that of R22 under the same displacement, the pipe diameter should be larger than R22 when using R404A refrigerant for piping design.
c. Since the saturation pressure of 404A is different from R22, the air tightness test pressure should be greater than R22. At the same time, the vacuum degree of the system should be higher than R22, and the water content should be lower than R22. When the refrigerant is charged, it should be charged in a liquid form to prevent the configuration of R404A from changing.
4. Other differences
a. For the same compressor, the current using R404A is greater than R22, so the diameter of the AC contactor, thermal relay and cable of the compressor should be adjusted. In terms of system protection, the setting value of the high-pressure pressure switch is adjusted from the original 2.45MPa to 2.7MPa.
b. R404A is a non-azeotropic mixing 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 affects the heat transfer performance of the system. In particular, when the refrigerant leaks, the system refrigerant needs to be completely emptied and replaced, so as to ensure the proportion of each mixed component and achieve the designed refrigeration effect, otherwise it will get worse.
c. Because R404A refrigerant and lubricating oil itself have good compatibility with water, the requirements of the system for moisture, residues, and cleanliness are improved compared with R22 refrigerant. R404A system moisture control and impurity control It is a relatively important indicator, and the corresponding filtering device in the system needs to be changed.
5. Advantages and disadvantages of R404a and R22
In summary, the overall performance of R404a environmentally friendly refrigerant is slightly worse than that of R22 refrigerant. The biggest disadvantage of R22 refrigerant is that it destroys the ozone layer and pollutes the environment. The biggest advantage of R404a is that it is environmentally friendly and non-polluting, and its performance is close to R22. It is the best solution for replacing R22 in the future. Sunde Ice Maker responds to the national environmental protection call. The 0.3 to 5 ton ice maker uses R404a refrigerant.