99.What is the function of cooling water? How many types of cooling systems are there?

A circulating water system at atmospheric temperature is used to remove exhaust medium temperature is Cooling water system.

Condenser cooling water system and Auxiliary Cooling water system are the 2 main cooling water systems in use in a power plant.

Condenser cooling water system is a once through system when sea water is used for cooling. This is the most common practice in the world. However river water with cooling towers are also used in inland plants.  Natural cooling tower and forced cooling tower are two types.

Bearing lub oil, Turbine operating oil, lub oil, etc are cooled in a tubular heat exchangers using a closed circuit cooling water system. This cooling water is mostly raw water used for water treatment plant.