# Pressure changes and external pressure

The questions I'm about to ask are standard thermodynamics but within a context of a refrigeration cycle if that is of any use to you. Anyways, I'm going to be going over my thoughts of how it works and I hope to get some corrections if something is wrong.

So let's say my liquid has a temp/pressure relationship of 125F/278 psig. It's a saturated liquid since if more thermal energy is added, it will then become a liquid-vapor mixture. In any case, it is travelling through a pipe at a pressure of 278 psig and some thermal energy is lost. Thus, it will become a 110F subcooled liquid.

At this point, it now will go through this tube and enter a pin-hole opening (just think of it as a valve). The tube coming out from the pin-hole opening (connected to the outlet) has a reading of 69 psig. The temp/pressure relationship for the same liquid at this pressure is 40F/69 psig. What I'm reading mentioned something called flash gas but I'm trying to connect it all at this point.

Fact A: Increasing the pressure of molecules in our volume (the pipe) of a state (vapor, liquid) will result in an increase of KE resulting in an increase of temp and also the opposite

Fact B: The liquid exiting the pin-hole opening will be 110F degrees and in liquid form. 110F is way above the boiling point for 69 psig so boiling will occur.

Q1: So based on the above, how are Fact A/B connected?

Q2: If the liquid boils it will decrease temperature from 110F degrees based on evaporation. The question is, how long will this evaporation/cooling go on for?

Q3: Even if the temperature of the liquid gets to 40F, won't the vapor emitted from the boiling be higher? In other words, after the boiling of the liquid I might have a liquid-vapor mixture left. Its temperature might go down to 40F however, the vapor pressure will be much higher than that of the tubing's 69 psig which doesn't make sense to me since a liquid-vapor mixture can only exist at the noted equilibrium of 40F/69 psig.

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