Refrigerant (refrigerant) is a substance in a refrigeration machine or heat pump that participates in heat transfer and changes its state of aggregation (liquid, vapor), which distinguishes it from coolants, which also participate in heat transfer, but do not change their state of aggregation conditions (for example, water in the heating system of a house).
The history of the invention
The main refrigerants used in household refrigerators belong to the class of freons, which replaced ammonia and methyl chloride, which are a deadly poison, as well as an explosive and flammable substance. The idea of using difluorochloromethane (R22) as a refrigerant belongs to Thomas Midgley Jr., who first launched a refrigeration machine using this refrigerant in 1928.
Subsequently, the use of this group of chlorine-containing refrigerants gained great popularity, and their concentration increased, which led to the destruction of the ozone layer, and these heat carriers began to be eliminated and replaced with the safest ones.
What is freon?
Freons -are a group of chemicals used as refrigerants. Fluorine-containing hydrocarbons with a negative (most often) boiling point are designated by the letters R-***, where R is Refrigerant, and *** - numbers indicating the number of fluorine, hydrogen, carbon atoms, as well as letters indicating the presence of bromine or iodine.
Basically, three types of refrigerant are used in household refrigerators, where the boiling point of individual ones can drop below 100 degrees.
One of the first types of refrigerant to replace ammonia, which often killed people when it leaked. And despite the fact that the R12 refrigerant had a huge impact on the ozone layer, since it was used a lot in household refrigerators, (compared to modern ones) it, unlike its predecessors, did not pass through microcracks and did not create frequent leaks, since it was used with mineral oils. At the moment, this type of refrigerant is found only in refrigerators that are 30 years old or older.
He replaced the good old R12 and was supposed to become a super deputy. But many manufacturers of the once popular Minsk refrigerators still produced today shuddered when they heard about this type of refrigerant, which brought them a lot of repetitions and significantly tarnished their reputation. It's all about the waxing of the synthetic oil that was in the compressors. Clots of paraffin clogged the capillary tube, like cholesterol plaques in human blood vessels, and caused the refrigerator to break down, and the craftsmen had to arrange dances with tambourines (we will talk about them in lesson 9) to bring the refrigerator to normal condition.
The most modern type of refrigerant is the “refrigerant of the future,” as scientists called it. But that was not the case, since this type of refrigerant also had its pros and cons. One of the advantages that supporters cited in its favor was a small dose of refueling. Which later became one of its disadvantages. After all, even with the most insignificant leak, the refrigerator stopped turning off, since it could not reach the desired temperature in the right place, despite the fact that the overall temperature in the chamber could be normal or lower. In addition, the repair of these units became more complicated, since very experienced and old craftsmen also needed scales with an accuracy of 0.5-1 grams. But they have not yet fully recovered from the purchase of a monometric manifold, which they had to purchase with the advent of R134 refrigerant. Even more grumbling and remembering how good it was with R12 refrigerant, a hose and a cylinder - romance.
Also, one of the disadvantages of R600a gas is that it is also fire and explosive in a ratio of 31 grams per 1 cubic meter of air. That is, 0.5 liters of R600a gas poured onto the floor is enough to cause an explosion to destroy the entire kitchen area. But, fortunately, the charging rate for this refrigerant for household refrigerators does not exceed 40-50 grams.
Comparison of refrigerants
The boiling point of R600a refrigerant is about -12 ℃, at normal atmospheric pressure of 1 ATM. At the same time, most thermostats turn off the refrigerator compressor when the temperature reaches -20 ℃. This tells us that for normal operation of the R600 refrigerator, the pressure when the compressor is running must be negative (small vacuum), at - 5 PSI. But at the same time, the R134a refrigerant has a boiling point of -26 ℃, which is higher than the 20 ℃ we need for the thermostat to operate. Which tells us that it is necessary to have positive pressure in the suction line, about 5 PSI. And for R12 refrigerant, boiling is achieved at about 30 ℃. Therefore, the pressure should be 5 PSI.
Transportation and storage
To transport the refrigerant to the repair site, metal disposable cylinders are used, which can be divided into two groups:
Small cylinders (from 300g to 1kg) - used by novice craftsmen or for rare types of refrigerants, since the price in this container is higher (in terms of 1 liter), but it is much easier to transport and carry it to applications.
Standard cylinders (13.6 kg) are the most common volume, but if you need 3 of these cylinders, then many problems arise during transportation. And if you are also involved in industrial refrigeration and air conditioning, then you need at least 2 more types of refrigerant.
Many craftsmen transfer refrigerants from a larger cylinder into small ones. In this case, the large cylinder should be heated with the outlet turned upside down, so that only liquid refrigerant flows, and the small cylinder must first be vented and then cooled. To create sparseness.
Attention! This method is not safe, and it is better to use small disposable cylinders or carry a large cylinder.
When transferring, you should always leave room for the refrigerant to expand. In hot weather (during field work), periodically release the pressure in the cylinder and do not leave it in the car in the sun, as you may find a car without windows and be short of a couple of cylinders.