What are refrigerants? These are special fluids. They are used in air conditioners and refrigerators. The refrigerant undergoes phase changes from liquid to gas when it absorbs heat and back to liquid when the compressor compresses the gas. The ideal refrigerant is selected based on the thermodynamic properties. It must be non-aggressive, safe, non-toxic and non-combustible.
A brief history of refrigerants
The Belgian scientist Frederick Sworts first came up with the synthesis of CFCs in the late 1890s. Its discovery occurred after replacing chloride in carbon tetrachloride with futuride for the synthesis of CFC-11 and CFC-12. In the late 1920s, Thomas Midgley Jr. improved the synthesis process and set the goal of using CFCs as a refrigerant to replace the ammonia, chloromethane and sulfur dioxide that were commonly used at that time.
They were harmful, flammable, and some even toxic. The most common refrigerant was CFC, called Freon - the DuPont brand name for the R-12 refrigerator. According to the requirements of the 30s of the last century, these refrigerants seemed ideal, scientifically sound and safer, non-corrosive gases and cheap to manufacture.
Only in the 1970s, it was found that chlorine molecules completely destroy the ozone layer, and they were banned. In the 1970s, scientists found that the refrigerant ammonia interferes with the penetration of infrared rays into them, as they accumulate in the atmosphere and cause heat transfer, which leads to climate change, so this composition was banned.
In the 1990s and 2000s, CFCs were replaced by HCFCs (hydrochlorofluorocarbon), and the most common HCFC is P-22, which had much less damaging effects on ozone, but it still remained dangerous. To solve the problem of ozone depletion, scientists came up with HFCs that did not contain chlorine. However, they later realized that HFC was still damaging the environment through greenhouse gases.
Modern types of refrigeration media
The European Commission has requested that R134A refrigerant not be used for certified passenger cars sold in the European Union. This mandate was originally intended for January 1, 2011. However, since the new refrigerant was not yet available to the wide market, this period was extended until January 1, 2013.
Starting in January 2017, all newly registered vehicles were required to use alternative refrigerant. In 2018, only 60% of new European-made passenger cars use safe refrigerant. Vehicles sold outside the European Union continue to use R134A or an even more dangerous refrigerant.
Main types of refrigerants:
- CFCs - chlorofluorocarbons.
- HCFC - HydroChloroFluoroCarbons.
- HFC - HydroFluoroCarbons.
However, all of them have been or will be replaced in the near future due to environmental impacts. Currently, the HFO refrigerant is starting to replace CFCs because they have much lower global warming potentials and do not destroy ozone, although some of them are highly flammable. At present, the 4th generation of refrigerants is entering the market, which have great thermodynamic properties and are environmentally friendly.
Choosing an Alternative for R12
R12 refrigerant is still widely used for refrigeration units. Indeed, it was very difficult to choose one that could replace this universal refrigerant under operating conditions. R134A is most suitable for these purposes.
Comparison of R134A and R12:
- The power at the evaporator temperature of -7 ° C is the same for both refrigerants, and below -7 ° C, if R12 is replaced with r134A refrigerant, there will be a significant loss of cooling effect. In such cases, it is recommended to use refrigerant mixtures instead of replacing R134A. Freon 134 can also be used for low temperature situations.
- Heat transfer coefficients for R134A are higher than R12. If they exist in the same liquid phase, the heat transfer coefficient of the R134A refrigerant is higher by 27–37%, and in the gas phase it is higher by 37–45%. If they exist in two phases, liquid and gaseous, the heat transfer coefficient for R134A is higher by 28–34% in the evaporator and from 35 to 41% in the condenser.
- The cooling effect of R134A is approximately 22% greater than that of R12. Thus, the mass flow rate of R134A required per tonne of cooling is approximately 18% less than R12. This means that for a given capacity of the refrigeration system, its required amount is 18% less than when using R12. That is, in all equipment where R12 is replaced with Freon 134, the amount of refrigerant that should be charged is less than R12. However, the specific volume of R134A is slightly larger than R12; therefore, for the same amount of refrigerant, the volume occupied by R134A is greater than R12.
- The increase in the cooling effect of R134A is compensated by the increase in its specific volume. Thus, R134a charged in modified systems should be 5–10% less than R12.
Convert R12 to R134A
Some early plants used ammonia as a refrigerant. However, most modern cars built before 1995 used the R12. R12 was a technologically advanced and efficient ic2 refrigerant, but it was later discovered to be an ozone-depleting gas, and its production and use were limited.
After 1995, it was replaced by the R134A, and it is still used in many cars. If the farm has an old car with an R12 air conditioning system, then motorists experience big problems replenishing such a system with leaks or maintenance. The industry launched the production of special adapters, after which the process of converting the system to R134A became simple.
Cooling system changes
To convert R12 to R134A, you need to make only a few small changes to the system. Fortunately, the compressor used in the old R12 system will still work with R134A refrigerant and will be just as efficient. The condenser and evaporator are just heat exchangers, so they also do not need to be changed to start another refrigerant.
One of the components that needs to be changed is a dryer. The last element of the system to be changed is the pressure ports. The R134A uses different ports to charge the system and measure pressure, so old R12 ports must be removed and replaced or supplemented with adapters. After acquiring the necessary equipment, remove the old refrigerant and oil. When installing the new ic2 refrigerant, RAG4A compatible PAG oil must also be added to maintain compressor lubrication.
After converting the system from R12 to R134A, it is important to check the system pressure for several days to make sure everything is working correctly. If you notice any small leaks in the system, use Red Angel A / C Stop Leak to seal the system.
Refrigerants are safer than freon
The common hydrochlorofluorocarbon R-22, used for decades, is not as good for the environment as experts once thought. The Environmental Protection Agency worked to phase out this refrigerant, and ultimately banned it completely. The abandonment of the R-22 began in 2010. By 2020, refrigerant use will be severely limited, and by 2030 completely prohibited.
The most environmentally friendly refrigerants currently available on the market are R-290 and R-600A. They are HC, or hydrocarbons, and their chemical names are “Propane” for R-290 and “Isobutane” for R-600A. They are completely halogen-free, have no ozone depletion potential and are the least dangerous in terms of the possibility of global warming. They also have high energy efficiency, but are flammable, since they are hydrocarbons. Currently, the greenest types of refrigerants are R134A, R-407C, R-410A. The manufacturers who produce these refrigerants claim that the substances are completely safe.
Freon cylinder R134A
With the discovery of the damaging effects of CFC and HCFC refrigerants on the ozone layer, this group has been widely used as a replacement. The refrigerant in the R134A refrigerator is hydrofluorocarbon (HFC), which has zero potential for depletion of the ozone layer and practically does not affect the greenhouse effect.
R134A refrigerant is a chemical compound tetrafluoroethane consisting of two carbon atoms, two hydrogen atoms and four fluorine atoms. Its chemical formula is CF3CH2F. The molecular weight of R134A is 133.4 and its boiling point is 26.1 ° C. R134A is non-combustible and non-explosive, has toxicity within normal limits and good chemical stability, somewhat high affinity for moisture.
In terms of general physical and thermodynamic properties, R134A refrigerant is very similar to R12. Therefore, it is considered an excellent replacement. The properties of R134 refrigerants are as follows:
- Auto-ignition temperature - 770 ° C.
- The level of depletion of the ozone layer is 04.
- Solubility in water 0.11 wt.% 25 C.
- The critical temperature is 122 ° C.
- Color code: light blue.
- Global Warming Potential (GWP) 1200.
- Refrigerant temperature, boiling point –26.1 ° C.
Thermodynamic properties of R-407C
According to its properties, it corresponds to the characteristics available in R-22. R-407C is a common refrigerant replacement for those who want to upgrade R-22 equipment. A mixture of hydrofluorocarbons includes pentafluoroethane, difluoromethane and 1,1,1,2-tetrafluoroethane. A widespread alternative refrigerant is popular in packaged air conditioners and brushless separation systems, as well as in lightweight air conditioning and direct expansion systems available in residential, commercial, and industrial environments. The R-407C also works in mid-temperature refrigeration systems and in many new appliances.
New equipment using nitrogen as a holding charge works best with R-407C due to the use of polyol essential oil. While the most common use of new appliances and refrigeration systems, the R-407C can be upgraded in some R-22 systems if oil change is part of the procedure. This alternative to freon is considered safe for the environment because of its zero-ozone depletion potential.
Ozone Depletion Potential R-404A
In this refrigerant, it is 0, just like R-407C and R-134A. It is often used for refrigeration systems that require temperatures from -45 ° C to 15 ° C. It is most useful in the commercial and industrial transport industries because of its wide range of operating temperatures. It is very similar to the R-22 and offers more advanced features. Since the R-404A does not have a quick reaction to air or water, it is considered safe for many purposes. It is also non-combustible, colorless and odorless.
However, as with any refrigerant, users should always take appropriate precautions to protect themselves. Direct contact with R-404A can still cause frostbite, and excessive exposure to fire or high temperatures can cause the tank to rupture. R-404A is quite common and available for purchase in stores that specialize in providing products for heating and cooling.
The mixture of two hydrofluorocarbon refrigerants, difluoromethane and pentafluoroethane, is a non-ozone-depleting refrigerant that provides better energy efficiency than R-22 and R-407C and does not use chlorine in its composition. It is considered more suitable as a replacement for the R-22 due to its higher pressure and cooling capacity.
Feature R-410A
If users decide to purchase devices that use the R-410A, the process is usually quite simple. In fact, many air conditioning and refrigeration companies manufacture units specifically for use with the R-410A. Although it is most popular in commercial refrigeration units, air conditioners, and refrigerators, it is important to note that this alternative to freon will not work in A / CR-22 units.
The characteristic of R-410A refrigerants indicates that they have a higher pressure, so a different manifold pressure gauge is required than the one normally used with R-22. The refrigerant must be charged in liquid form and only in short bursts. R-410A is sold under several brands: AZ-20, Suva410A, GenetronR410A, Forane410A, EcoFluo rR410 and Puron. It is quite easy to buy on the Internet and in specialized stores.
Vehicle conditioning
The 2006 EU Directive requires all new cars sold in the EU to be equipped with low global warming potential (GWP) refrigerants. The limit is set to the value of GWP 150, which currently can provide YF. Its advantage is the property of self-utilization - it completely decomposes in the atmosphere after about eleven days.
Despite the fact that HFO1234yf was adopted as a new refrigerant, Germany has doubts. Daimler and some other German manufacturers and also regulatory agencies believe that YF is dangerous due to its high flammability. In response, Germany approved some Daimler vehicles to continue working on the R134A, which contradicts the EU directive.
The European Commission even threatened lawsuits against Germany for not being able to fully implement the new emission rules for refrigerants. GM and Toyota have publicly announced their support for YF and stated that they consider this substance to be safe.
The cost of new systems
The additional cost of the new YF refrigerant is in the range of EUR30–50. YF systems are less efficient, and this requires the additional use of an internal heat exchanger.
Since the cost of the production process for YF is higher than R134A, a green tariff is assumed for this product for many years, especially starting in 2018, when all newly registered vehicles in the European Union will have to use a refrigerant other than R134A.
Price increase from February 1, 2018:
- R452a + 20%.
- R410a + 20%.
- R448a + 15%.
- R449a + 15%.
System Upgrade R-22
Replacing R22 with R134A is a fairly simple process. First of all, full R22 should be removed from the system. Then you need to remove all the lubricating oil from the system (the maximum amount of oil remaining inside the system is 5% of the total amount present in it). Mineral oil should be replaced with synthetic ester based. The dehumidifier and oil filter must also be replaced.
The amount of R134A required in the system is from 90 to 95% R22. Labels should be placed on systems that have been upgraded with R134A describing the new refrigerant and lubricating oil. Despite the easy process, it is important to complete it carefully. R-22 residues in the system can lead to cross-contamination. It for R-22 and R-134A can make the car cooling system less reliable and increase the pressure of the compressor head to dangerous levels, which will lead to a complete system failure. In addition, R-134A requires a special oil mixture - polyarylene.
In 1987, the Montreal Protocol was announced, which is an international treaty in many countries, designed to help combat the damaged layer of the O-zone. One of his initiatives was to phase out CFCs around the world. In 1994, the United States stopped using the R-12 in the automotive industry. R-12 has been replaced by an alternative to HFC R-134a. In 2010, under the Montreal Protocol, the United States announced the cessation of the use of R-22 in future applications. All new machines will focus on the HFC R-410A, which is chlorine-free.