We have all heard, at one point or another, about the use of gases in our cooling appliances, be it ACs or refrigerators.
We do have some idea that they play an important role in the cooling process. Oftentimes, servicing such appliances may include filling in the gas, which may have leaked, causing low or no cooling. So, what is this gas, and why does your refrigerator need it?
What is a refrigerant?
All refrigerators need a ‘refrigerant’, which is basically a fluid that is used to absorb heat from its surroundings and get rid of it elsewhere. This process is repeated in cycles, thus cooling the desired areas.
Refrigerants transform between liquid and vapor states to absorb and lose heat constantly, and in this way, they lower the temperature of the target environment.
How do refrigerants work inside a refrigerator?
So, the refrigerant or ‘gas’ that your refrigerator uses simply absorbs the heat inside the refrigerator to expand from liquid to gas state, thus cooling down the refrigerator cavity. The refrigerant is then compressed in the compressor to turn it back into a liquid, and that is where it loses its heat, thus removing it from the refrigerator cavity.
This is the principle on which it operates. However, the exact process used in most household refrigerators is called a ‘vapor compression cycle.’ The vapor compression cycle starts when the refrigerator’s ‘gas’ or refrigerant circulating inside enters its compressor. At this point, it acts like a low-pressure gas or vapor, and it is at a temperature a little below that of the refrigerator’s interior.
This refrigerant, in its vapor form, is compressed by the compressor and leaves the compressor in the form of a high-pressure, high-temperature vapor. This superhot vapor then flows under high pressure through the refrigerator’s condenser or coils. These coils, usually located outside of the refrigerator, lose heat to the outside environment.
This process turns the hot vapor refrigerant back into liquid form. This liquid refrigerant leaves the condenser still under pressure but at nearly the outside ambient temperature.
The refrigerant in its liquid form passes through an expansion valve, which is a narrowed point or constriction in the tube, and enters a low-pressure region, which causes some of the refrigerants to almost instantly expand into a vapor.
Next, the air from the freezer compartment, which is actually warmer than the refrigerant, is blown using a fan at the evaporator tubes, causing the refrigerant to expand and turn completely into vapor. Finally, this complete vapor state refrigerant goes back to the compressor to repeat this cycle.
This is how the gas or refrigerant is circulated in a household refrigerator to cause cooling and maintain the desired cool temperature.
Properties of a refrigerant
This refrigerant fluid is usually a synthesized chemical. Before choosing the refrigerant that will be used in an appliance, a lot of its properties need to be observed.
From the above vapor compression cycle process, we may be able to ascertain that the refrigerant needs to be able to absorb and lose heat quickly and possess other thermodynamic properties that enable it to transform to the desired state of a low boiling point liquid and a compressible gas or vapor within the temperature ranges that can be created or are already available inside and around a refrigerator.
Besides these thermodynamic properties, refrigerators are used inside homes and are often used by kids and elders, too; hence, their effects on people need to be minimal. A refrigerant must, therefore, be non-corrosive and non-toxic in nature so that it does not harm the skin or eyes of users upon leakage. It should not poison or contaminate food or give off undesirable or toxic vapors.
Further, given that refrigerators need electricity to run and are regularly opened, closed, and sometimes moved around in the house, the refrigerant should also be non-flammable to avoid catching on fire or causing explosions due to short circuits or sparks.
Finally, there are economic concerns; for instance, the cooling liquids used in a spacecraft cannot be used in a refrigerator as they may be prohibitively expensive. Thus, it must also be possible to manufacture the refrigerant at scale economically so that it does not contribute too much to the costs of assembling a refrigerator.
Evolution of refrigerants (Old Vs. Modern Refrigerants)
The very first refrigerants that were used in the first home refrigerators in the 1920s were Sulphur Dioxide and Methyl Formate. However, both of these were corrosive and toxic to the eyes and skin, causing lesions and even loss of eyesight. They were a hazard to have inside a home. Hence, their use was abandoned as soon as CFCs or Chloro Fluoro Carbons became available in the 1930s.
The most common refrigerants that we have used in the past and those still in use today include:
1. CFCs (or Chloro Fluoro Carbons)
You may have heard of CFCs. These are the culprits when it comes to our Ozone Layer Depletion problem. The earth has an Ozone Layer high up in the atmosphere, which protects us from the UV rays of the sun. However, the Chlorine in CFCs reacts with this layer and destroys the ozone, creating gaps or holes in the ozone layer that allow UV rays to enter and cause diseases such as skin cancers and a host of other health issues.
CFCs are the oldest, but today, they are some of the least used refrigerants. They were widely adopted in the 1930s as a non-toxic alternative to earlier toxic refrigerants. However, once the Ozone hole in our atmosphere was discovered, it became necessary to phase them out.
Today, CFCs have almost completely been phased out for our own safety.
The company DuPont used to produce the most popular CFC refrigerant, “R-12,” which was sold under the brand name ‘Freon.’ Freons or Chloro Fluoro Carbons, however, do not find a place among modern refrigerants and were phased out between the 1990s and the early 2000s.
2. HCFCs (or Hydro Chloro Fluoro Carbons)
CFCs were replaced by HCFCs or chlorocarbons. The most popularly used HCFC is the ‘R-22’. However, the benefits from this switch were not tremendous.
HCFCs still contain Chlorine, which badly affects our atmosphere by depleting the Ozone layer.
Unfortunately, however, a large number of cooling appliances, like air conditioners in India, still run on HCFCs.
3. HFCs (or Hydro Fluoro Carbons)
Hydro Fluoro Carbons were created to solve the problem of ozone depletion caused by Chlorine. HFCs are free of Chlorine and, hence, do not contribute to the depletion of the Ozone layer.
However, these are still contributors to global warming. R-134a, whose chemical name is HFC-134a (1,1,1,2-Tetrafluoroethane), is the most common HFC used in refrigerators.
This is still widely available in refrigerators currently being used. Other commercially available HFCs include R-32 and R-410A. They are also more energy efficient than HCFCs.
4. HCs (or Hydro Carbons)
Hydrocarbons are the latest stage of the evolution of refrigerants. They do not have any Halogen molecules (Chlorine, Fluorine, etc), thus making them completely safe for the ozone layer. Also, their contribution to global warming is almost negligible, making it the best available refrigerant as far as the safety of the environment goes.
They also have very good energy efficiency; however, the one big negative is the fact that hydrocarbons are highly flammable. There have been reports in the early days of leakage and explosion due to a spark. However, safer systems were put in place, and in recent years, appliance manufacturers have been doing a satisfactory job of protecting consumers from flammability, and these could be gradually accepted as the best available refrigerants currently.
The commonly available HC refrigerants in India are Propane ‘R-290’ and Iso-Butane ‘R-600A’. While R-290 is used in air conditioners, R-600A is commonly used in refrigerators.
On the whole, while the flammability of HCs remains a negative issue, we are pretty certain that the evolution of refrigerants will continue to make them even safer and environmentally friendly as the scientific community and research make progress and governments tighten regulations.
Conclusion: So, What type of coolant gas do most refrigerators use?
We hope we were able to provide a clear picture of the role, importance, and environmental effects of refrigerants. Currently, if you are looking for the most environmentally friendly option available, then Hydro Carbons like Propane and Iso-Butane would be the answer.
Related: Troubleshooting Refrigerators: How To Fix Your Fridge?