Shini Efforts on CFC-free Refrigerants

 Prologue

The damaged ozone layer of Earth has caused serious concerns from the international community. In Vienna in 1985 the Vienna Convention for the Protection of the Ozone Layer was formulated and then on September 16, 1987 in Montreal, Canada the Montreal Protocol on Substances that Deplete the Ozone Layer was adopted which came into effect on January 1, 1989. In June 1991, China formally proposed to join in the revised Montreal Protocol.

R22, the widely used refrigerant for medium-size and small-size refrigerators has been listed as control item and is used less and less gradually which will be abandoned in 2030. In order to adapt the control measures, world wide air conditioner manufacturers and refrigerant plants are thrown themselves into the R&D of substitutes of R22. It is an urgent task for this industry to find new CFC-free refrigerants replacing R22 which is considered as an excellent refrigerant originally.

 

 

New Trend of CFC-free Refrigerants

The substitution of R22 should focus on: reducing ozone depletion index and risks of the refrigerant (such as flammability and toxicity); mixing the refrigerants of high security and fatality to make the concentration of the mixture below the dangerous level; the substitute should have similar thermodynamic properties (such as operating pressure and energy efficiency) to R22 refrigerant so as to replace it rapidly and conveniently.

Judging from the current situation, there are many kinds of substitutes as shown in diagram below. Potential substitutes can be divided into synthetic and natural refrigerants. HFCnote1 is a synthetic one, and NH3, CO2, H2O and hydrocarbons and so on.

Refrigerant substitutes can be roughly divided into pure refrigerants and mixed refrigerants. For example, R134a is a kind of pure refrigerant; however, R407C and R410A are both mixed refrigerants. The composition of R407C is HFC-32 / HFC-125 / HFC-134a (3 / 25 / 52wt.%), and it is a non-azeotrope refrigerant. The composition is HFC-32 / HFC-125(50 / 50 wt.%) and it is near-azeotrope refrigerant.

Note 1: CFC is a kind of halogenated hydrocarbon which contains fluorine, chlorine and carbon.

HCF is a kind of halogenated hydrocarbon which contains hydrogen, fluorine and carbon.

HCFC is a kind of halogenated hydrocarbon which contains hydrogen, fluorine, chlorine and carbon.

CFC, HCFC and HCF are common refrigerants. However, CFC has been banned, and HCFC is gradually withdrawing the historical stage because they have a general term—Freon.

HFC is one sort of HCFs substances which excludes fluorine atoms (such as R134a, used as CFC-free refrigerant by some refrigeration industries).

Mixture is composed by two or many compounds. A new refrigerant can be produced by mixing existing refrigerants and accurate proportions.

Azeotrope mixture consists of two or many compounds which has well-proportioned gas and liquid. Simply speaking, as one- component refrigerant, fractionation will not occur in refrigeration cycle. Azeotrope refrigerant does not have temperature slip.

Non-azeotrope mixture bears change in component volume and saturation temperature. In a word, they will be fractionated.
 

Defrigerant Substitutes 

Profile and Characteristics of Different Refrigerants

Introduction and Features of R22

R22 is colorless and odorless gas approximately under room temperature. Non-corrosive and nontoxic, it can be liquefied into colorless and transparent liquid when pressurized.

Introduction and Features of R407C

As a longterm substitute of R22, R407C has a similar thermal property to R22 whose composition is HFC-134a / HFC-32 / HFC-125=52 / 23 / 25wt.%. R407C is a kind of CFC-free refrigerant that does not deplete the ozone layer. With similar compressor capacity, system temperature and pressure to R22, it is considered as a direct substitute with features as follows:

■ The refrigerant should be liquefied when added into the system. Otherwise the composition of the refrigerant will change once leakage occurs, resulting in difficulties in maintenance.

■ Essential adoption of synthetic refrigeration oil which has high hygroscopicity.

■ It has the similar working pressure to that of R22.

■ System efficiency is 5% less than that of R22.

■ Unaffordable price.

The compressor manufacturer often recommends the use of POE(Polyol Ester) as refrigeration oil.

Introduction and Features of R410A

As a kind of non-azeotrope mixed refrigerant which excludes chlorine, R410A is colorless gas under room temperature and pressure and it is a compressed and liquefied gas stored in the cylinder. It is also a CFC-free refrigerant that does not deplete the ozone sphere.

R410A has much higher pressure compared with R22, so R410A can not be used in typical R22 compressor.

The compressor manufacturer often recommends the use of POE(Polyol Ester) as refrigeration oil.

R410A has similar critical pressure but different properties compared with R22. However, one of the important factors that R410A can replace R22 is that it has higher coefficient of performance (COP).

 

 

From the comparison above, R410A is more likely to be the substitute of R22.

Introduction and Features of R134a

R134a is one of the internationally recognized substitutes of R12 which is also used to confect other mixed refrigerants, such as R404A and R407C.

R134a is a kind of effective and safe substitute of R12 in refrigeration industry because of its thermal and physical properties as well as low toxicity. It is pure refrigerant that ca be applied in flooded system and does not change when leakage occurs. Compared with R22, it has lower working pressure. Without structural problems about stress vessel, it is cheaper than R407C and R410A.

The compressor manufacturer often recommends the use of POE(Polyol Ester) and PAG(Polyalkylene Glycol) as refrigeration oil.

There are many factors to be considered when selecting refrigerants, because the choice will influence to some extent the overall operation of the system, reliability, costs and market acceptance. Different transmission performance due to different heat conductivity and hypotension will cause significant influence in system design and performance. Large centrifugal coolers have completely chosen R134a, and screw units are now transferring to R134a. Candidate refrigerants for the small-size air cooler and water cooler are R407C and R410A.

 

 

 

Shinis Efforts and Achievements on CFC-free Refrigerants

Shini has been committed to providing customers the product of higher quality, more energy-efficient and environmentally friendly, leading and promoting industrial development. We realized the substitute of HCFC22 (R22) which adopted by the cooler is an urgent issue a few years ago, and commenced to solve this problem. After continuous experimentation, adjustment, validation and finalization of all series of products within years, Shini has finished employing the CFC-free refrigerant in the chiller which takes leading position in the industry.

Shinis screw-type chiller employs R134a. With significant advantages in compressing consumption, large system will have better energy-saving benefits when adopting R134a instead of R22. As shown in tables below, the machine uses R134a has lower energy consumption: 

 

 

 

Shinis SICC-A chillers use R407C. Capability and energy efficiency bears attenuation inevitably when R22 is replaced by R407C, as shown below:

 

 

 

Due to use of optimized compressor specially employed by R407C, optimized heat exchange design and stricter process control, Shinis SICC-A series have nearly the same capability and efficiency when using R407C compared with R22. It exerts the system performance of R407C.

 

Shinis SIC series chillers use R410A, which is widely used in home air-conditioners all around the world and is getting more and more acceptance in medium and small-size air-cooled and water-cooled units. Regarding the performance of R410A, Shinis SIC series units that adopt R410A have lower energy consumption compared with those use R22. It is more energy-efficient.

 

What to be added is the refrigeration oil that the CFC-free refrigerant uses is synthetic oil because of its different properties with R22. Synthetic oil is easily affected by impurities such as moisture, oxide layer and grease which calls for attention during construction. Clean new pipes instead of used ones should be employed to prevent water and so on. Circulation of nitrogen is essential at one end of the pipe when welding. CFC-free refrigerants can not mix with other refrigerants of refrigeration oil, and it should be liquid as adding to the system.

 

Conclusion

R410A will be a long term substitute of R22 as regarding its development. It is still under development and testing, to which air-conditioning manufacturers in each country are paying close attention. In view of the system performance, what will be certain is that R410A is better than R22; however, obtaining of the compressor is the key point in real practices. Re-design of the compressor is necessary because the working pressure of R410A is 56%~65% higher than that of R22.

In order to meet environmental requirements, Shini balances aspects such as safety, environment, efficiency and costs according to its own characteristics and actual needs endeavoring new refrigerant substitutes. Considering technical and economic factors, Shini has chosen those refrigerants above as developing direction and insist in green environment, energy saving, reducing discharge and enhance recovery; it also focus on training and research to achieve double wins of the enterprise and customers.