How to use the refrigerant in a chiller and related knowledge
For a chiller Refrigeration System, as long as it is installed correctly and reliably, with no leaks at pipe connections or other points, the system can operate effectively for a long time without needing refrigerant replenishment. If a refrigerant leak occurs in the chiller, we should first identify the leak, resolve it, and then replenish the refrigerant.
I. Causes of Insufficient Refrigerant
1. Newly installed chillers were not charged with refrigerant as required.
2. Poor system airtightness, leading to refrigerant leakage.
3. Improper operation or maintenance, causing refrigerant leakage.
II. Effects of Insufficient Refrigerant Charge on Chillers
1. If both the suction pressure and discharge pressure of the compressor are lower than normal values, it may indicate insufficient refrigerant charge.
2. Under insufficient refrigerant charge, the compressor will operate below its rated load, resulting in light-load or even no-load operation, with current lower than the rated value.
3. Insufficient refrigerant charge reduces the evaporation rate in the evaporator, leading to decreased Cooling Capacity and poor refrigeration performance, causing slow or no temperature drop in the room or cold storage.
4. If the thermal expansion valve of the chiller shows little or no frost formation, or in air conditioning conditions, little or no condensation, it may also indicate insufficient refrigerant charge.
5. Similarly, if the evaporator shows little or no frost, or in air conditioning conditions, little or no condensation, it suggests insufficient refrigerant charge.
When a chiller exhibits signs of insufficient refrigerant, the entire refrigeration system should be thoroughly inspected to determine the specific cause or location of the leak. After troubleshooting, refrigerant should be replenished according to specifications to restore normal operation.
Note the differences between refrigerants R22 and R134a:
Analysis of Application Characteristics of R22 and R134a:
1. The Global Warming Potential (GWP) of R134a is 0.25, while that of R22 is 0.36—both are greenhouse gases.
2. The Ozone Depletion Potential (ODP) of R134a is 0, while that of R22 is 0.06, making R134a an environmentally friendly refrigerant.
3. The specific volume of R134a is 1.47 times that of R22, and its latent heat of evaporation is lower, so the cooling capacity of an R134a unit is only 60% of an R22 unit. In terms of cost per unit of cooling capacity, R22 units are about 60% cheaper than R134a units.
4. The thermal conductivity of R134a is 10% lower than that of R22, requiring larger heat exchangers in R134a units.
5. R134a is highly hygroscopic—20 times more so than R22—necessitating higher-performance dryers in the system to prevent ice blockage.
6. R134a has a stronger swelling effect on rubber materials than R22, leading to higher leakage rates in practice. It is also more corrosive to copper, causing "copper plating" in the system, which requires the addition of inhibitors.
7. R134a systems require dedicated compressors and ester-based lubricants. These lubricants, due to their high hygroscopicity, foaming tendency, and diffusivity, are less stable in performance compared to the mineral oils used in R22 systems.
8. R134a and other HFC refrigerants, along with their specialized ester-based lubricants, are more expensive than R22, resulting in higher operational and maintenance costs. Other HFC refrigerants, such as R410A, R440A, and R407C, though more efficient than R134a, also have drawbacks such as high operating pressures, stricter requirements for piping components, the need for optimized heat exchangers and unit design, and higher investment and maintenance costs. These factors make them less suitable for large-scale refrigeration applications in developing countries at this stage. This is why international agreements have extended the deadline for developing countries to phase out HCFCs—a result of collective efforts by these nations.
In conclusion, an ideal refrigerant does not exist in the short term. At this stage in China, R22 remains superior to R134a and other eco-friendly refrigerants in terms of efficiency, stability, and cost-effectiveness for large-scale refrigeration applications. Until an ideal refrigerant is developed, R22 can still be used until 2040.