R 744 CO2 Refrigerant

I don't know what info would best suit your situation, but here is a link with basic pressure-temperature and pressure-enthalpy charts:

http://www.achrnews.com/Articles/Feature_Article/97d657d6f5d5a010VgnVCM100000f932a8c0____

I do thank you I have found out a great deal of quality information. Love this site.

Since this is CO₂, and being that the pressures that Roy referred to could put it into the supercritical range (over 1085 psia and 31ºC), I'm thinking that there would be some serious deviation from typical refrigeration systems?

M&M Refrigeration, who I think is in Baltimore, has supplied the machinery for several cold storage plants with two stage, ammonia/CO2 systems. As I recall, after you get down to about -4 F CO2 works pretty good on the low stage.

There are others, but I don't have their names right now.

I have heard said the EU has decreed CO2 be used for automotive AC, but found no proof of it. I wonder how you can get 50-55 degree air out of something so cold as the temperatures CO2 would probably have to run at.

CO2 might become a great refrigerant, but operates some terrific pressures.

It is sad ammonia has gotten such a bad rap - another victim of the the media, the trial lawyers, and the government bureaucracy.

CO2 has no ozone depletion potential and insignificant global warming potential. Other principal benefits of CO2 are that it is a natural substance, it is cheap, readily available, not poisonous in any common concentration, and nonflammable. Carbon dioxide (CO2) is considered to be an alternative to HFC refrigerants due to its nonflammability,non-toxicity and small global warming potential. In UK some supermarkets have already switched over to the CO2 systems. It is emerging as one of the potential natural refrigerants. Sulphur dioxide (SO2), Carbon dioxide (CO2) are other natural refrigerants which are in use since many years. But their applications are mostly in marine engineering. To commercialize these natural refrigerants several researchers are working but still there is a long way to go on this issue.