Safe Integration of R-1132(E) in Refrigerant Blends: Advancing Low-GWP Cooling Technologies

Air conditioning and refrigeration are things most of us rely on daily, often without even thinking about them. Whether it’s cooling your home on a hot summer day or keeping food fresh in your fridge, these systems make life easier. But there’s a hidden downside: the refrigerants that power these systems, particularly hydrofluorocarbons (HFCs), are not environment friendly. They trap heat in the atmosphere at levels far beyond carbon dioxide, which makes them a significant contributor to climate change. This has become a global problem, and efforts like the Kigali Amendment to the Montreal Protocol are pushing to phase out HFCs and replace them with alternatives that are safer for the planet. That has left industries scrambling to find refrigerants that don’t just work well but also have minimal impact on the environment. A new type of refrigerant called hydrofluoroolefins (HFOs) has been getting a lot of attention because they degrade faster in the atmosphere and have much lower global warming potential (GWP). One HFO that stands out is R-1132(E), also known as trans-1,2-difluoroethylene. Developed by Daikin Industries, it’s been called a game-changer because its GWP is practically zero—just 0.0056. That’s astonishingly low compared to traditional refrigerants. It also performs similarly to R-32, a refrigerant that’s already popular in air conditioning systems, which means it could be used in everything from homes to electric vehicle cooling systems. On paper, it seems like the perfect choice for a more sustainable future. But as with most things that sound too good to be true, there’s a catch. R-1132(E) has a stability problem. Under certain conditions, like high heat, high pressure, or a spark, it can break down into harmful byproducts such as hydrofluoric acid. This process, called self-decomposition, is a big safety concern. While the refrigerant is environmentally friendly, its instability makes it risky for large-scale use unless these issues can be addressed.

To tackle this, a group of researchers at Daikin Industries, led by Mr. Tomoyuki Goto, Mr. Takashi Usui, Dr.  Takashi Yoshimura, and Mr. Yasufu Yamada conducted a deep dive into the problem. Their study, published in the International Journal of Refrigeration, focused on figuring out when and how R-1132(E) decomposes. They didn’t stop there—they also explored blending it with other refrigerants, like R-1234yf, to see if they could improve its stability while keeping its ultra-low environmental impact. Their work is a significant step forward. By identifying what triggers decomposition and showing how to make R-1132(E) safer, they’ve brought us closer to using this refrigerant in real-world systems. If these challenges can be fully addressed, R-1132(E) could revolutionize the cooling industry, offering an option that’s safe, efficient, and dramatically better for the environment. This type of innovation is exactly what’s needed as the world works toward more sustainable technologies.

The research team wanted to see how stable and safe R-1132(E) is when used in conditions similar to those in actual air conditioning and refrigeration systems. They aimed to pinpoint the exact situations where this refrigerant might start to break down on its own and to find ways to prevent that by mixing it with other refrigerants. To recreate possible real-world problems, they designed three different experiments. The first one was called the metal wire fusing method, which simulated what happens during an electrical short circuit inside motor windings. They used a platinum wire and heated it with an electric current to act as an ignition source, testing how the refrigerant would react. The results were pretty striking: pure R-1132(E) decomposed quickly at pressures over 1 MPa when it received an energy input of just 30 joules. But when they mixed R-1132(E) with R-1234yf, the decomposition only happened at much higher pressures and temperatures. This showed that adding R-1234yf helped slow down or suppress the decomposition reaction. In their second experiment, known as the heat source method, they tried to mimic the frictional heat that might be generated in compressor bearings or shafts. The authors used molybdenum wire, which can handle higher temperatures than platinum, to see how localized heating would affect the refrigerant. With pure R-1132(E), they observed decomposition at heat source temperatures above 800°C when the refrigerant was under a pressure of 5 MPa. However, similar to the first test, mixing in R-1234yf made a big difference. Blends containing 40% or more R-1234yf showed remarkable stability—even when exposed to extremely high ignition temperatures up to 2500°C, no decomposition was observed. The final experiment involved arc discharge tests to replicate the electrical arcs that can occur due to dielectric breakdown in air conditioning systems. They used high-voltage equipment to create arc discharges and measured how much energy was released. The findings indicated that the chance of self-decomposition increased with both higher pressures and more energetic arc discharges. Yet again, adding R-1234yf proved to be highly effective in reducing this risk. Blends that had 33% or less R-1132(E) didn’t decompose, even under the most extreme discharge conditions they tested. These experiments highlighted important connections between the composition of R-1132(E) blends, the pressures and temperatures they operate under, and the energy from potential ignition sources.

In conclusion, the study of Mr. Tomoyuki Goto and colleagues stands out because it  addressed a critical global challenge: reducing the environmental impact of refrigeration and air conditioning systems while maintaining safety and efficiency. By investigating the decomposition behavior of R-1132(E) and proposing solutions to mitigate associated risks, the research provides a pivotal step toward the adoption of next-generation refrigerants that align with international climate goals. One key implication is the potential for R-1132(E) to be used as a core component in ultra-low GWP refrigerant blends, making it a transformative option for industries transitioning away from high-GWP HFCs. With a GWP of just 0.0056, R-1132(E) represents an opportunity to dramatically reduce the carbon footprint of cooling systems. However, its inherent instability in pure form posed a barrier to widespread adoption. This study’s findings demonstrate that blending R-1132(E) with stabilizing agents like R-1234yf not only enhances its safety but also retains its environmental benefits, paving the way for its practical application. The research also has implications for the design and regulation of cooling systems. By defining the precise conditions under which R-1132(E) undergoes self-decomposition, the study provides a foundation for engineers to develop safer refrigeration technologies. The results gained can guide the creation of equipment that avoids operating conditions likely to trigger decomposition, such as excessive pressures or temperatures. This understanding is particularly valuable for manufacturers of air conditioners and refrigeration systems, enabling them to adopt environmentally friendly refrigerants without compromising safety or performance. From a broader perspective, the findings support global efforts to meet climate targets, particularly those outlined in the Kigali Amendment to the Montreal Protocol. By demonstrating that R-1132(E) can be safely utilized in blends like R-474A and R-479A, the study contributes to the transition away from harmful HFCs.