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Inha researchers propose mixture of R-1234yf and R-134a as non-flammable, low GWP alternative to R-1234yf for MACs

13 December 2012

Researchers from Inha University in South Korea have proposed a solution to the recently re-ignited debate over the safety (flammability) of R-1234yf, targeted for use as a low global warming potential (GWP) replacement for R134a for mobile air conditioning (MAC) systems. An azeotropic mixture of 88.5-90% R-1234yf and 10-11.5% R134a can solve the flammability issue associated with R-1234yf while still delivering a low (<150) GWP refrigerant, they say.

Over the last several years, the automotive industry has been tracking to replace the MAC refrigerant R-134a, which has a global warming potential (GWP) of 1,430, with the lower-GWP refrigerant R-1234yf (GWP = 4). Three separate SAE-led efforts had validated the choice.

In September, however, Daimler derailed the adoption of R-1234yf when its internal testing raised concerns about its flammability and thus questions on its safe usage as a replacement refrigerant in MAC systems. Daimler said that it would not use the chemical in its products. (Earlier post.) Subsequently, a fourth SAE International Cooperative Research Program (CRP) was launched to further analyze the safety of R1234yf. (Earlier post.)

The team from Inha University is proposing an azeotropic mixture—a liquid mixture of two or more substances that retains the same composition in the vapor state as in the liquid state when distilled or partially evaporated under a certain pressure—of R-1234yf and R-134a as a replacement.

In a study, they measured the drop-in performance of R-134a, R-1234yf and R-1234yf/R-134a mixtures at three compositions of 5%, 10%, and 15%. Their test results showed that the COP, capacity, discharge temperature of R-1234yf and R-1234yf/R-134a mixture are similar to those of R-134a. For R-1234yf/R-134a mixture, flammability decreases as more R-134a is added and at compositions of more than 10% of R-134a, the mixture becomes non-flammable.

Since HFO1234yf/HFC134a mixture with 10-11% HFC134a is non-flammable and azeotropic and has no ODP and GWP of less than 150 meeting the requirement of European mobile air-conditioner directive, it can be used as a long term environmentally friendly solution for various HFC134a applications including mobile air-conditioners with minor modifications.

—Lee et al.

At present, Inha University holds the Korean patent on the formulation, but there is no international patent—anyone can use it free outside of Korea, noted Dr. Dongsoo Jung of Inha’s Department of Mechanical Engineering and corresponding author of a paper describing the work.

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