Why are these refrigerants added as the liquid status?
Refrigeration systems use refrigerants as working fluids, and refrigerants generally have two forms: liquid and gas. Today we will talk about the relevant knowledge about liquid refrigerants.
Refrigerants can be divided into 3 categories: single refrigerants, non-azeotropic mixed refrigerants, and azeotropic mixed refrigerants.
Are these refrigerants liquid or gas?
The composition of the single active substance refrigerant will not change whether it is gaseous or liquid, so the gaseous state can be charged when charging the refrigerant. Although the composition of the azeotropic refrigerant is different because the boiling point is the same, the composition of the gas and liquid is also the same so that the gas can be charged;
Due to the different boiling points of non-azeotropic refrigerants, the liquid and gaseous refrigerants are different in composition. If gaseous refrigerants are added at this time, the composition of the added refrigerants will be different, for example, when only a certain gaseous refrigerant is added. So it has to add to liquid refrigerant.
That is to say, non-azeotropic refrigerants must be added with liquid, and non-azeotropic refrigerants all start with R4, which needs to be added as a liquid. Common non-azeotropic refrigerants like R401A, R403B, R404A, R406A, R407A , R407B, R407C, R408A, R409A, R410A, R41A. As for other common refrigerants, such as R134a, R22, R23, R290, R32, R500, and R600a, the refrigerant composition will not be affected by adding air or liquid.
In addition, it is important to note and emphasize again that the non-azeotropic refrigerant must add in a liquid state.
Taking R410A refrigerant as an example, its composition is as follows: R32 (difluoromethane): 50%; R125 (pentafluoroethane): 50%; when the R410A refrigerant cylinder is left standing, because of the different boiling points of R32 and R125, which will inevitably lead to the composition of vaporized refrigerant in the upper part of the refrigerant cylinder is not 50%R32+50%R125, but maybe all components are R32 due to its low boiling point. Therefore, if a gaseous refrigerant is added, it is very likely that the refrigerant added is not R410A but R32.
Then, we will briefly introduce the following common methods of refrigerant charging and related knowledge:
(1) Bubble filling method in sight glass; (2) High and low-pressure filling method; (3) Current filling method; (4) Weighing filling method. We have analyzed the pros and cons of these methods in previous articles, and this article will not repeat them.
The most accurate method of charging is by weighing, which weighs the refrigerant added to the system. This method can only be used when the required charging volume of the system is known, and the system requires full charging, which is usually the case for monolithic equipment.
In the maintenance of the refrigeration system, in most cases, gaseous or liquid refrigerant can be charged from the low-pressure side. When the refrigerant charge is large, the refrigerant can also be charged from the high-pressure side by the liquid charging method. Requires attention! If the liquid refrigerant is charged from the low-pressure side, it must be added slowly to avoid liquid hammer! If you are afraid of liquid shock, it can also be filled in a gaseous state.
The method of adding refrigerant from the low-pressure side:
- When charging gaseous refrigerant from the low-pressure side, turn the low-pressure three-way stop valve counterclockwise to the endpoint, and then connect the fluorine tube of the fluorine bottle to the low-pressure three-way stop valve.
- Open the bottle valve of the refrigerant bottle, slightly loosen the joint of the bypass wire seat of the three-way stop valve, and use the refrigerant gas to drive out the air in the fluoride pipe.
- When there is a “his, hiss” airflow sound, lock it immediately, and refrigerant charging begins.
When the injection volume reaches the specified quality, close the stop valve of the fluorine bottle, turn the low-pressure three-way stop valve counterclockwise to the endpoint, close the bottle valve of the R22 fluorine bottle, remove the fluorine tube, and the fluoride addition is over.
For more detailed refrigerant charging methods, refer to our previous article: 8 Refrigerant Charge Methods You Should Know.