This report contains review of thorough study of refrigerants and their effects on environment. Beginning with the history of Refrigerants their evolution and trend of shifting from CFCs to modern refrigerants to avoid Global Warming caused by Depletion of Ozone layer.
A refrigerant is a fluid which is used in vapor compression cycle to transfer the heat by absorbing/losing it from conditioned space to atmosphere. The object to be cooled is usually at a lower temperature than atmosphere and the job of the fluid is to work against second law of thermodynamics i.e. to transfer heat from low temperature to higher temperature. Various physical, chemical, economical and safety limits place an upper limit to use a fluid as commercial refrigerant. Hence, so far there’s no perfect or ideal refrigerant existing with desired properties.
History and background of refrigerants:Earlier, when vapor compression cycle was discovered refrigeration found its applications in large cooling spaces so at that time ammonia and carbon dioxide were used as refrigerants. Later when refrigeration made its way to smaller applications like domestic and commercial purposes sulfur dioxide and methyl chloride entered the market.
Later, CFCs replaced all these refrigerants and attracted the market due to their extensive use in refrigeration applications. But CFCs phased out due to their ozone depletion effects. Shifting from CFCs to HFCs and PFCs lessened the ozone depletion effect however the Global warming potential of these gases are way high as compared to CO2.
Properties of an ideal refrigerantThere are some standard properties to manufacture an ideal refrigerant which are as follow.
Cost of refrigerants
Enthalpy of vaporization
Some new refrigerants have been discovered like iso-butane (R-600a) and propane (R-290) having zero ozone depletion effect and GWP (Global Warming Potential) as low as CO2. However, these refrigerants are flammable and explosive causing a risk of safety. That’s why they are being commercially used with (LEL) Low Explosive Limit concentration to avoid any accident. Around 2020 75% of the manufacturers are expected to use these refrigerants commercially. With the passage of time some international Unions phased out refrigerants having GWP more than 150 (GWP is 100 year warming potential of gas in kg per kg of CO2 ) R-32 has zero Ozone depletion effect but still some GWP so there could be better refrigerant which will ultimately be perfect for environment.
HFC phase down and introduction of R-32:R-410A has been in use for many years and is very efficient but has the highest GWP i.e. 2088. According to HVAC-R, it cannot be banned completely but its areas of applications can be changed. In 2015, they started to look for an alternative refrigerant that can be used and will be more environmental friendly. Daikin took this step and launched R-32 in March 2015.
It has less impacts on environment. Now, the HVAC-R industry decided to use this. For this purpose they need to change the whole industry. They need new people who are well informed with this refrigerant and know how to design it and install it. And this is how R-32 started its journey in making this world a little better. It was used to manufacture R-410A and hence it was readily available but the main problem was what type of unit can be used for it. Daikin solved this problem and launched inverter units.
R-32 future uses:Everybody knows refrigerants are used to produce cooling. The Netherlands Environmental Assessment Agency has stated that the rate of increase in heat (global warming) will be more than decreasing heat in our buildings in coming years. This greenhouse effect will shoot up fast after year 2020.
To solve this problem, Daikin, a well renowned company as a manufacturer of air conditioners has started to work on refrigerants that will not cause this problem. They are using energy-efficient inverter technology that will reduce global warming and have sold about 10 million units since then. This is less than half the amount of CO2 emitted by cars in Japan.
Daikin has selected R-32 best for use if we want to save our planet. It is very beneficial and important for multi-split and single type air-conditioners. Daikin has proved to global market that if we use R-32, global warming will be reduced by at least 800 million tons (19%) of CO2 which is not possible with other refrigerants.
As the benefits of R-32 is explained above, it is very efficient in conveying heat. Thus, by using it electricity consumption can be reduced by at least 10% than the original compared to other refrigerants e.g. R-22.
It has the highest value of ATEL (22%) as compared to other refrigerants i.e. R-410A (17%) and R-22 (5.9%). It makes it safe and fit for future use.
Comparison of R-32 with other refrigerants up till now with facts and figuresThe basic reason to select the refrigerant R-32 is that it is a next generation refrigerant because of the changes in refrigerant gas legislation, from 2025 no gas having GWP of more than 750 can be used commercially and R-410A has lower availability, making R-32 a better choice. Here is the comparison of R-32 with other refrigerants, on the basis of following considerations.
Ozone Deletion Potential and Global Warming PotentialR-32 has no ozone depletion potential as it is chlorine free refrigerant. Also, it has very less i.e. 675. it has one third GWP as compared to R-410A almost 68% less. This is not the only refrigerant having less GWP value but also, we have HFO blends, ammonia and propane, but these are not easily available and need careful handling.
Temperature and pressure constraintsEvery refrigerant has particular values for the temperature and pressure on which they work, but R-32 has no special constraints for temperature and pressure as R-410A operates at high pressure i.e. 50% higher than R-22. R-32 has higher critical temperature in turn has higher COP.
Volumetric cooling capacityR-32 has higher heat of vaporization than other refrigerants so it requires less mass flow rate for per unit cooling capacity. Hence having high volumetric cooling capacity. It can reduce the charging volume by 30% as compared to R-410A.
R-32 has higher efficiency than other refrigerants and it consumes almost 10% less electricity. It has 1.5 times greater refrigeration effect as compared to R-410A and R-22.
FlammabilityR-32 mildly flammable refrigerant according to ASHRAE standard, which makes it easier to handle.
ToxicityAll refrigerants have toxicity index, separating them into categories of higher to lower toxicity, R-32 has lower toxicity than other hydrocarbon refrigerants and falls in category of type.
So, according to the above comparison, R-32 is the future refrigerant to be used commercially and domestically, not to forget the other refrigerants having less impact on the environment, such as R-152a and 600 series, these refrigerants have higher COPs than R-32 and some of these refrigerants have lower evaporator pressures than R-32. But R-32 is favorable over these as it can operate on almost same parameters as R 400 series, with no special requirements. It reduces the size of outdoor units in case of splits to about 18%. Also, it is readily available as it is used in different refrigerant blends.
Applications of R-32:R-32 or HFC-32 is included in a category of refrigerants which are environmental friendly and addresses economic considerations:
- It plays no role in ozone depletion i.e. zero ozone depletion potential
- It has low global warming potential, approximately one-third of R-410A
- It helps to save energy with best results and has superior energy efficiency than many other refrigerants
- It has less toxicity similar to refrigerant R-410A and R-22 and categorized as level A, hence safe for use
- It has higher refrigeration capacity leading to a compact design (single component refrigerant) which makes it easy to recover and easy to handle
- As this refrigerant is not blended, it can be easily charged and reused
- It has low flammability and low thermal conductivity making it fit for many applications
- It is used in the manufacturing of some other refrigerants for example R-410A and hence easily and readily available
- It’s co-efficient of performance is higher due to greater latent heat of vaporization. Higher the latent heat of vaporization lower the mass flow rate per unit cooling capacity
- It’s amount of charge is much smaller as the density is low (than R-410A)
- It has high critical temperature which is beneficial for higher COP’s
There is still a need of an ideal refrigerant which may not affect the environment adversely fulfilling the physical and chemical properties along with safety and health requirements. To handle overall global effects on environment people should shift their trend towards using zero ODE and zero GWP refrigerants so that our future generations may not be threatened of environment issues predicted by US clean air act. "hydrofluoroolefin", HFO-1234yf is so far the best refrigerant and must be fully commercialized.