4 ms·

We have yet to find a refrigerant that is not either toxic, explosive, or destructive to the ozone layer / a potent greenhouse gas. My understanding is that new

We have yet to find a refrigerant that is not either toxic, explosive, or destructive to the ozone layer / a potent greenhouse gas. My understanding is that new consumer systems use propane because its relatively safe and not toxic or causing dangerous emmissions.

cyberax 2y ago
Supercritical CO2 is a great refrigerant. It's neither toxic, nor destructive to ozone, nor is it a particularly dangerous for GW.
- userbinator 2y ago
  CO2 was superseded by other refrigerants because it's less efficient (incidentally, ammonia is one of the most efficient), and the (very) heavy equipment required to utilise it due to the extremely high pressures is also costly.
  - cyberax 2y ago
    I believe, CO2 is actually more thermodynamically efficient if used in supercritical freezers? It's just much more difficult to work with, as you need all the tubing to withstand about 90 atmospheres of pressure.
  - grigri907 2y ago
    CO2 is less common today, but has hardly been "superceded." I specialize in energy modeling for industrial refrigeration systems, and have studied several new industrial cold storage projects comparing CO2 to freon and ammonia. Their efficiency is on par with ammonia systems, within a few percentage points. I'll agree that the equipment is heavy-duty, but disagree if you mean "massive." The energy density of CO2 is so high that suction lines can be 2"-4", 6"-8" is common for ammonia. Modern systems use many (a dozen+) small recip compressors instead of larger HP screw compressors. When all is said and done, CO2 systems are small enough that they are frequently contained to a single rack and placed on the roof of a building, whereas a comparable ammonia system requires its own engine room and a significantly larger footprint. The biggest opportunity for CO2 to outperform ammonia is in heat recovery and reuse. I had a customer who was exploring selling his (waste) heat as a utility to a neighboring food processor.
uticus 2y ago
> use propane It's called R-290 [0], but yes this is the same as in "propane grill." I'm a "consumer," but the technicians I talk to about replacing a residential HVAC have mentioned that consumer HVAC systems need new fire detection (maybe also suppresion?) systems on the A/C side just because of the new ingredient. Again, not propane for the heating side, but for cooling. Crazy. [0] https://www.superradiatorcoils.com/blog/r-290-pros-cons-comparisons-r22-r134a-r404a https://www.superradiatorcoils.com/blog/r-290-pros-cons-comp...
- SoftTalker 2y ago
  I wonder why they don't just put the whole chilling unit outside and use a chilled water loop into the interior air handler.
  - tristor 2y ago
    You could do that, but you'd need to build a heavily insulated place to have the A-coil/evap head, as it stands right now the efficiency loss would be too much. Additionally, the current HVAC model also acts as a rudimentary de-humidification system for buildings which helps reduce the "felt" temperature and maintain humidity levels beyond just cooling.
timewizard 2y ago
The problem with R290 systems is they generally do not get service ports. As service ports tend to leak. So they're fully sealed systems. This is great for small scale refrigeration applications but for any indoor air cooling or commercial refrigeration it's effectively unusable.
marcosdumay 2y ago
"Any leak will kill you through a horrible and painful process" is not on the same level of problems as "destructive to the ozone layer / a potent greenhouse gas".

cyberax 2y ago

Supercritical CO2 is a great refrigerant. It's neither toxic, nor destructive to ozone, nor is it a particularly dangerous for GW.

userbinator 2y ago
CO2 was superseded by other refrigerants because it's less efficient (incidentally, ammonia is one of the most efficient), and the (very) heavy equipment required to utilise it due to the extremely high pressures is also costly.
- cyberax 2y ago
  I believe, CO2 is actually more thermodynamically efficient if used in supercritical freezers? It's just much more difficult to work with, as you need all the tubing to withstand about 90 atmospheres of pressure.
- grigri907 2y ago
  CO2 is less common today, but has hardly been "superceded." I specialize in energy modeling for industrial refrigeration systems, and have studied several new industrial cold storage projects comparing CO2 to freon and ammonia. Their efficiency is on par with ammonia systems, within a few percentage points. I'll agree that the equipment is heavy-duty, but disagree if you mean "massive." The energy density of CO2 is so high that suction lines can be 2"-4", 6"-8" is common for ammonia. Modern systems use many (a dozen+) small recip compressors instead of larger HP screw compressors. When all is said and done, CO2 systems are small enough that they are frequently contained to a single rack and placed on the roof of a building, whereas a comparable ammonia system requires its own engine room and a significantly larger footprint. The biggest opportunity for CO2 to outperform ammonia is in heat recovery and reuse. I had a customer who was exploring selling his (waste) heat as a utility to a neighboring food processor.

uticus 2y ago

> use propane It's called R-290 [0], but yes this is the same as in "propane grill." I'm a "consumer," but the technicians I talk to about replacing a residential HVAC have mentioned that consumer HVAC systems need new fire detection (maybe also suppresion?) systems on the A/C side just because of the new ingredient. Again, not propane for the heating side, but for cooling. Crazy. [0] https://www.superradiatorcoils.com/blog/r-290-pros-cons-comparisons-r22-r134a-r404a https://www.superradiatorcoils.com/blog/r-290-pros-cons-comp...

SoftTalker 2y ago
I wonder why they don't just put the whole chilling unit outside and use a chilled water loop into the interior air handler.
- tristor 2y ago
  You could do that, but you'd need to build a heavily insulated place to have the A-coil/evap head, as it stands right now the efficiency loss would be too much. Additionally, the current HVAC model also acts as a rudimentary de-humidification system for buildings which helps reduce the "felt" temperature and maintain humidity levels beyond just cooling.

timewizard 2y ago

The problem with R290 systems is they generally do not get service ports. As service ports tend to leak. So they're fully sealed systems. This is great for small scale refrigeration applications but for any indoor air cooling or commercial refrigeration it's effectively unusable.

marcosdumay 2y ago

"Any leak will kill you through a horrible and painful process" is not on the same level of problems as "destructive to the ozone layer / a potent greenhouse gas".