Can we use CO₂ in our fridges & AC's?

Could we use carbon dioxide as a replacement for the refrigerants we use in fridges, freezers, as well as the air-conditioning units in our homes and cars?
The software I use to plot all charts you see in the video is FREE for download here: trc.nist.gov/refprop/MINIREF/...
00:00 Homework
01:19 Recap
02:37 Isenthalpic expansion
05:55 What's the blank space?
06:25 The experiment
08:21 Dry ice
10:33 CO2 vs R-134a as a refrigerant
12:35 Refrigeration cycles
14:22 Comparing working pressures
14:57 HFC's and CFC's
15:46 What's the verdict?
Process with Pat is the place to come for perspective and to ask stupid questions. I want you to leave more knowledgeable, confident, motivated, and most importantly, curious. I also want to invigorate a field that seems tired and uninspiring, at least if you get your perspective from internet forums. These are not lectures. This is a place for you to leave thinking “Oh! That’s why...”
This channel is not only for chemical engineers - anyone who works with processes should be able to find something of value here.
#ProcessEngineering
#ChemicalEngineering
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[@xse345]

Great video 👍👍 I was surprised the temp. would drop to -72 C. So I believe frequent use of this cartridge may not be good for the valves and tubes of the bike as I doubt they can handle this low temp. and resulting thermal shock.

[@ProcesswithPat]

Yes you can seriously hurt yourself if you aren’t careful! Holding the cylinder after discharging it really burns if it doesn’t come with a cover. Interesting point about the potential effects of thermal shock on the valve!

[@ChemEngWeekly]

Clever concept idea pat! CO2 in fridges would certainly be interesting, maybe it could have an impact to offset carbon footprints…?

[@ProcesswithPat]

Doubt it… the small mass of CO2 inside the cycle would be offset by the power consumption of producing components for higher pressure as well compressing to higher pressures!

[@ChemEngWeekly]

Completely true, did not consider that!

[@carultch]

@@ChemEngWeekly Plus, the way we extract the various components of air, is to cool them down to extremely low pressures, and sort them by boiling point. This is how we get pure CO2, pure O2, pure N2, and pure forms of all inert gasses other than helium. That process alone would produce more CO2 from the energy required to operate the distillation process, than you'd extract from the atmosphere.

[@VaclavFucik]

@@carultch Hello, I am not sure what your source is, but I contacted a few refrigerant manufacturers and they gave me a different answer. National Refrigerants Inc.: "Most of the CO2 produced in the UK comes as a bi-product from making fertilizer." I guess it would be similar in other countries. Messer Inc.: "Commercial CO2 is usually recovered from high-volume, CO2-rich exhaust gas streams. The collected raw CO2 is purified and liquefied. In addition, CO2 is also extracted from natural wells in volcanic areas."

[@jamesevans225]

Very good video. Thank You!! What I learned from this video is that the components must be beefed up AND some kind of anti-dri ice mechanism must be installed. The CO2 would be cheap, safe, and not harmful to Ozone but the mechanism to make it work would be expensive. Now I'm wondering how long will a CO2 system last so that it pays for itself like solar panels. I'm also wondering if the CO2 system draws more energy due to having a beefier compressor.

[@VaclavFucik]

Hi, you summed it up pretty good - beefier CO2 components are more expensive, the refrigeration system is overall more complex in terms of control system and components, the COP (coefficient of performance) of CO2 systems is generally lower than HFCs. On the other hand, due to high pressures the CO2 piping sizes are considerably smaller. The payback time of a CO2 refrigeration system is very indiviual and depends on various factors. Mainly geographical location - areas with higher ambient temperatures have generally lower COP than colder climate areas. But this can be overcome by different system arrangements (parallel compression, ejector systems etc.). CO2 has also bigger potential for waste heat usage than HFCs (CO2 has higher discharge temperatures). As you can see, a lot of factors need to be taken into account when assessing the suitable refrigerant.

[@Mrsach15]

Very interesting video ! I was wondering what is the final volume of the cartridge at 1bar ?

[@ProcesswithPat]

Awesome. The volume doesn’t change, so I’m not sure what you mean. You mean what mass is left when the pressure inside is equal to atmospheric? You can use the ideal gas law to calculate it.

[@Mrsach15]

I mean we have a 21ml of compressed CO2 at 58 bar , what would be the volume of gaz once you decompress it ?

[@ProcesswithPat]

Then I'd use (assuming 20 Celsius) PV = nRT = mRT/M, so V = mRT/MP = 16 g × 8.314 J/mol.K × 298 K ÷ 44 g/mol ÷ 101325 Pa = about 9L