Hi all

I'm currently training to become a refrigiration engineer to repair ice cream machines, I've read "refrigiration 101" and found it very helpful.

I understand that the compressor pushes high pressured vapour through the condenser where it gains heat from the surrounding air and condenses to a liquid, it's then pushed along the lines to a expansion valve, on the other side of the expansion valve the high pressured liquid becomes low pressured and therefore has a lower boiling point, into the evaporator where it gains the heat from the surrounding area and changes to a vapour, low pressured vapour then goes back into the compressor where it all starts again,

My question is: we use R404a refrigirant. I believe the boiling point is -46 degrees. I nderstand the relationship between increasing the pressure increases the boiling point but at the evaporatornthe R404a is at 1.5 bar so not much of a pressure increase, we only need the area around the evaporator to reduce to 4 degrees, so how does the refrigirant reach the required -46 degrees to change to a vapour ? Surely the pipes etc would all reach -46 degrees too ?

Thanks for time !

Jack