Basic Principles Air Conditioning

We see in the lives of everyday physical phenomena that seem simple and of no particular interest, and yet ...
Everyone has seen a full pot of water boil!
Well that's what happens in the evaporator of your car, the water absorbs heat from the burner up to 100 ° (1 bar air pressure) and then vaporizes the refrigerant fluid in the evaporator absorbs heat from the air and evaporates (vaporizes 134a, for a car, at 0 and 3 bar abs), this air being stirred can be seen from the cold air !!
We all have at one time or another out a bottle of fresh water from the fridge (not for drinking pastis !!! it is the sin!) What can we notice?
Water forms on the bottle, that's happened?
Well, the vaporous moisture from the room air and being closer to the cold bottle saw its temperature drop to move from the vapor state to the liquid state.

We speak of condensation!
It happens the same with the refrigerant flowing through the condenser, with fans who brew the air through the condenser, the refrigerant is removed from the heat to get to the point where it passes the vapor state, in liquid form!
It is c ... no?
The refrigerant circuit is a closed and sealed circuit so that state changes that I just described, occur.
It is necessary to use a refrigerant which has the appropriate physical characteristics, amongst others,
it must be evaporated at low temperature by absorbing heat.
For circulating the refrigerant, a compressor is used, the compressor draws steam (since the liquid is incompressible) from the evaporator and compresses it to send it to the condenser:
Now things get complicated a bit!
Some of you have already heard of "the characteristic ideal gas equation":
PV / T = constant
where P = pressure, V = Volume and T = Temperature
I'll try to keep it simple: in a compressor when the piston rises, the volume decreases in the cylinder so the gas pressure and temperature also increase (shown with a bicycle pump).
The report PV / T = constant is met.
If the pressure is dropped abruptly through a throttle valve, the pressure drops, the temperature drops and the volume increases, the report is still respected.

Operation:
A fluid in the refrigeration circuit is drawn into low pressure and low temperature to the compressor. It is in the vapor phase.
The compressor compresses the high-pressure and high-temperature vapor. The vapors pass from the vapor state to the liquid state in the condenser by removing heat. We are still in high pressure (HP) with a fairly warm temperature and 100% liquid.
The fluid passes through the expansion valve where its pressure and hence its temperature drops, the fluid is at low-pressure, low-temperature liquid state, fluid passes into the evaporator where it will absorb the ambient heat and thus move from liquid state to the still low vapor pressure and low temperature and again be sucked by the compressor.

DO OUTSIDE AWAY FROM ANY FLAME
Take a bottle of butane or propane full and open very, very slightly the valve. Put a metal plate at 10 cm in front of the faucet for 2 seconds, the plate has become very cold.
The outlet pressure is low, its temperature also increased and the volume (external volume is greater than the internal volume of the bottle)
It happens the same with the regulator of your system:

The refrigeration cycle
1 - Condenser
2 - regulator
3 - Evaporator
4 - Compressor