Compressing a fluid which is in gaseous state requires a huge amount of energy,so before compressing the fluid it should be converted into liquid state. A condenser is used for this purpose, which rejects heat to the surrounding and converts steam into liquid. Ideally there will not be any pressure change during this heat rejection process, since the fluid is free to expand in a condenser. Changes in fluid are shown in the p-v and T-s diagram below.

Pump

At exit of the condenser fluid is in liquid state, so we can use a pump to raise the pressure.During this process the volume and temperature (2-3 deg.C rise)of fluid hardly changes, since it is in liquid state. Now the fluid has regained its original pressure.