How does a heat pump compressor increase pressure in the sealed system?

[GreenWombat]

Hi Russ. In your contribution (Saturday, 24 August), you wrote that the pressure drop across the evaporator was “too small to be visible on the P-V diagram and can be ignored.” For me, that was brilliant because it resolved the contradiction of (1) the pressure-volume diagram showing constant volume and (2) refrigerant moving across the evaporator without any pressure drop.

My error: I meant "the pressure-volume diagram showing constant pressure"