How do hydrocarbon refrigerants like propane and butane compare to natural refrigerants like CO2 and ammonia?

Hydrocarbon refrigerants like propane and butane have similar thermodynamic properties to natural refrigerants like CO2 and ammonia, but they have a lower GWP. They are also more compatible with existing HFC-based systems, making them a more drop-in replacement. However, hydrocarbons are still flammable and require special safety considerations, whereas natural refrigerants like CO2 and ammonia are non-flammable.