Advanced Refrigerants R410a and R134a in HVAC

Refrigeration was named one of the most significant engineering achievements of the last century, ranking alongside computers, spacecraft and the Internet. Nearly 20% of energy consumption worldwide is due to the demand for refrigeration and air conditioning. Refrigerants are the vital working fluids at the heart of the vapour-compression cycle, moving heat from a lower to higher temperature. Although, the search for the ideal refrigerant may seem to be a modern endeavour spurred by the need to replace the chlorofluorocarbons (CFCs) in the 1980s or more recently to find low-Global Warming Potential (GWP) fluids. These discoveries renewed the urgency to reduce the use of CFCs and led to the adoption of the Montreal Protocol on substances that deplete the ozone layer.

The original Montreal Protocol called only for a 50% reduction in the production of five of the most-common CFCs (including R-11 and R-12) as well as three Halons (used as fire extinguishing agents) and some in the refrigeration industry felt that the remaining 50% of CFC production should be reserved for refrigerant usage. But, subsequent amendments to the Montreal Protocol mandated the complete phase-out of the CFCs as well as several HCFCs.

Thus, began the “third generation” of refrigerants, characterized as “ozone protection.” With the ozone hole and Montreal Protocol the refrigeration industry was suddenly faced with finding replacements for the CFCs. R-134a and R-123 had been identified as possible CFC replacements by the refrigerant manufacturers. Natural refrigerants concern about safety but other factors such as GWP, ODP, Breakdown by-products, availability and option in high ambient have no issues.

Natural refrigerants seem to be sustainable refrigerants for sustainable environment. The refrigerant industry has been moving to introduce advanced commercial refrigerant technologies for some time, yet the adoption of these technologies has been slow. Such systems may deploy refrigerants such as hydrocarbons, ammonia, carbon dioxide, and hydro-fluoroolefins as alternatives to HCFC or HFC refrigerants that are commonly used. The Methodology includes a framework to incentivize the increased uptake of these available alternatives in commercial refrigeration (Figure 1).

Advanced refrigerants

Refrigerants are used in a wide range of Heating, Ventilation, Air Conditioning and Refrigeration (HVAC&R) applications, as well as chemical processing, foam blowing agents, aerosols, chemical solvents and fire suppression. Understanding the global refrigerant market and trends is an important component of current efforts to transition toward lower GWP refrigerants. The global refrigerants market is large, complex and is projected to grow rapidly. Understanding end uses and the types of refrigerants that are used is important for improving refrigerants to most efficiently meet this growing market demand.

R410a

410A is a new environmentally friendly refrigerant gas. It does not destroy the ozone layer and the working pressure is about 1.6 times compared to the common R22 air conditioning, refrigeration and higher (warm) efficiency.

R-410A is a member of the hydro-fluorocarbon (HFC) class of refrigerants and is composed of equal parts R-32 and R-125. Its chemical formula is CH₂F₂ + CHF₂CF₃. Classified as a zeotropic refrigerant blend (meaning its constituent substances boil at different temperatures), R-410A is considered to be “near-azeotropic” This means that despite the disparity between its components’ boiling temperatures, it results in very little glide – which describes the temperature difference between the start of the first substance’s boiling process and the conclusion of the second’s. R-410A is primarily used in commercial and residential HVAC systems.

R410a is an HFC blend designed for new R22 applications. R410A is the dominant refrigerant in residential heat pumps. Even though refrigerant R410A does not contribute to the depletion of the ozone layer it has a GWP (AR5) of 1924. The refrigerant permits to reduce the GWP from 2090 kg eq CO₂ to 675 kg eq CO₂. Pure synthetic and natural refrigerants such as R32 or propane (R290) can be used as alternate refrigerant, but their thermodynamic properties are different and a mixture of HFC/HFO mixture R452B and R454B are proposed as alternate refrigerant. The performance test was done on multiple options like split air conditioner, water-to-air heat pump, ducted heat pump, roof top air conditioner using fixed scroll compressor and thermal expansion valve. The R-410A system operates more efficiently, reducing wear and tear on the compressor.

R134a

R134a refrigerant is commonly used in various cooling and air conditioning applications. It was originally developed to replace R12 in car AC systems. It has also been used to replace refrigerants R12 and R500 in coolers. It is also used as medium temperature systems in residential buildings and commercial contexts. R134a refrigerant is suitable for:

• Medium and high temperature cooling
• Air conditioning in residential buildings
• Light air conditioning
• Vehicle air conditioning and industrial applications, such as centrifugal coolers.

R134a refrigerant is a hydro-fluorocarbon (HFC) compound with the chemical formula CH₂FCF₃. It is composed of carbon, hydrogen, and fluorine atoms Due to its composition, R134a is classified as a greenhouse gas with a relatively high global warming potential (GWP) However, it is less harmful to the ozone layer than chlorofluorocarbons (CFCs) and hydro-chlorofluorocarbons (HCFCs). To address environmental concerns, regulations and restrictions have been implemented to control the use and release of R134a refrigerant. These regulations aim to minimise its impact on climate change and encourage the adoption of more environmentally friendly alternatives. One of the significant advantages of R134a refrigerant is its compatibility with existing cooling systems. It can be used as a drop-in replacement for older refrigerants like R12 (CFC) and R22 (HCFC), making it a convenient choice for retrofitting existing equipment without major modifications.

R134a refrigerant possesses several key properties contributing to its popularity in the cooling industry (Figure 2). Firstly, R134a is non-flammable, making it a safe choice for various applications Unlike some other refrigerants, it does not pose a fire hazard, ensuring the safety of both users and equipment. Secondly, R134a exhibits high chemical stability, providing long-lasting performance in cooling systems. It is resistant to degradation and can maintain its effectiveness over an extended period. Furthermore, R134a is non-toxic, ensuring the safety of human health it does not pose significant risks if accidentally released or inhaled, making it suitable for residential, commercial, and automotive use. Another essential property of R134a refrigerant is its low Global Warming Potential (GWP). Although it is not entirely climate-friendly, R134a has a relatively lower global warming impact than other refrigerants, such as R410A or R404A. Moreover, R134a exhibits excellent thermodynamic properties, enabling efficient heat transfer in cooling systems. It provides effective cooling performance while minimising energy consumption, contributing to overall system efficiency.

Different detailed applications of R134a are as follows

• Domestic Refrigeration: 134a refrigerant is commonly used in household refrigerators and freezers to keep food fresh and preserve quality. Its properties allow for efficient cooling and temperature maintenance.
• Automotive Air Conditioning: R134a is widely employed in automotive air conditioning systems to provide comfort during hot weather It helps cool the cabin space and regulates temperature for a pleasant driving experience.
• Commercial Refrigeration: R134a is utilised in commercial refrigeration units, such as supermarkets, restaurants, and cold storage facilities. It ensures the proper storage and preservation of perishable goods on a larger scale.
• Industrial Cooling: R134a is employed in various industrial processes that require cooling, such as chemical manufacturing, pharmaceutical production, and food processing. It helps maintain optimal temperatures for efficient operations
• HVAC Systems: R134a is used in Heating, Ventilation, and Air Conditioning (HVAC) systems for residential and commercial buildings. It enables efficient cooling and temperature control, ensuring comfortable indoor environments.

Comparison of R134a with other commercially used refrigerants

• R134a vs R22: R22 is an older refrigerant phased out due to its ozone-depleting properties. R134a often replaces R22 in existing systems, offering compatibility and improved environmental performance.
• R134a vs Hydrocarbons: Hydrocarbon refrigerants, such as R290 (propane) and R600a (isobutane), have gained attention for their low GWP and ozone-friendly nature. However, they are flammable and require additional safety measures during handling and installation, unlike non-flammable R134a.
• R134a vs HFOs: Hydrofluoroolefin (HFO) refrigerants, such as R1234yf and R1234ze, are considered the next generation of environmentally friendly refrigerants They have extremely low GWPs and zero ozone depletion potential However, their adoption is still in progress, and R134a remains a widely available and proven option.

Conclusion

The use of natural refrigerants such as carbon dioxide, ammonia and hydrocarbons in vapour compression system should be entertained as they are more environmentally friendly refrigerants, however, their flammability issue requires safe equipment design, safe handling, servicing and transportation practices along with safe refrigerant charge.

Dr. (Prof.) D.B. Jani received Ph.D. in Thermal Science (Mechanical Engineering) from Indian Institute of Technology (IIT) Roorkee. Currently he is a recognized Ph.D. Supervisor at Gujarat Technological University (GTU). He has published more than 180 Research Articles in reputed International Conferences and Journals. He has also published 5 reputed books in the area of thermal engineering. Presently, he is an Associate Professor at GEC, Dahod, Gujarat Technological University, GTU, Ahmedabad (Education Department, State
of Gujarat, India). His area of research is Desiccant cooling, ANN, TRNSYS, and Exergy.