In condensers used in thermal power plants, steam is normally used in shell side and cooling water on the tube side, because of the reason that

• compared to the mass flow rate of cooling water, the rate of condensation of steam is invariably smaller.
• maintaining vacuum on tube side is more difficult than that on the shell side.
• water velocity can be increased conveniently to increase the overall heat transfer co-efficient because of its lower specific volume compared to steam.
• condenser can act as a storage unit for condensed steam.