Suppose you have a sealed can of liquid refrigerant 134-a. This can is allowed to be in thermal equilibrium with the room which is at 25°C. The lid is then slowly opened so that some refrigerant will escape. This would gradually decrease the pressure of the refrigerant as it is exposed to the atmosphere which is at 1 atm. The pressure would decrease isothermally during the compressed liquid state, but upon reaching its saturation pressure at 25°C, further decrease in pressure would decrease its temperature down to -26°C at 1 atm. I understand that, at the compressed liquid state, the temperature remains constant (despite the decrease in pressure) since it is allowed to have heat transfer with its surroundings. What I don't understand is why does temperature only decrease, as pressure decreases, during the saturated state? Why can the heat transfer from the surroundings be able to keep the temperature constant at the compressed liquid state but not at the saturated state?
This has to do with the R134 thermodynamics properties PVT.
please look at the PVT diagram of R134 in any thermodynamics book and you will see the different phases of the fluid as a function of PVT
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