New HFO/CO2 blends in the pipeline

The refrigeration and air-conditioning sector has long been divided into two distinct camps, that promoting natural refrigerants and that developing low-GWP fluorocarbons. But could this be about to change?
According to ACR News, research on blends of HFOs and carbon dioxide has been undertaken. Commercial applications of such blends have been limited in the past, because of high glide and limited benefits over other solutions, but Honeywell has recently patented blends containing these components. Glide is now better understood and refrigerant combinations with markedly different boiling points may now be less of an issue.
Honeywell’s patents suggest past work with both HFO1234yf and HFO1234ze in combination with CO2 as a potential replacement for R134a and in different percentages for R22, R407C or R410A amongst others. Honeywell describes them as non-flammable and suitable as drop-in replacements with some minor system modifications.

Manufacturer Mexichem has also been looking at three-component blends of HFO1234ze and CO2 with R52, R152a, R161, R134a and hydrocarbons. Mexichem also sees them as a potential replacement for a range of HFCs including high-GWP R404A. The company is currently looking at using 3-10% CO2 in the final blends as it boosts the pressure of the system, thus increasing refrigeration capacity and also counters the flammability of HFOs. Mexichem is also focusing on mobile air-conditioning applications.