Why we create a vacuum in the low pressure fresh water generator ?

The vacuum is created in the LP fresh water generator to reduce the evaporation temperature of the water.

At1 atm , T=100 C

At0.2 atm , T=60 C

So we don't need heaters for the evaporation of the water, that' why the diesel engine cooling water outlet (85 C) is used as the heating agent in the generator.

by using an air ejector(venturi effect)