Steam condenser is an equipment in which the exhaust steam from the steam turbine is condensed by means of coolant (water).
Thermal efficiency of a closed cycle power developing system using steam as working fluid and working on carnot thermodynamic cycle is given by an expression (T1 – T2)/T1. This expression of efficiency shows that the thermal efficiency increases with an increase in temperature (T1) and decrease in temperature (T2). The maximum temperature T1 of the steam supplied to a steam prime mover is limited by material considerations.
The temperature T2 (temperature at which heat is rejected from the steam condenser) can be reduced to the atmospheric temperature if the exhaust of the steam takes place below the atmospheric pressure. If the exhaust of the steam is at atmospheric pressure, the heat rejection is at 100°C temperature.
Low exhaust pressure need to be maintained to obtain low exhaust temperature. But the steam cannot be exhausted to the atmosphere if it is expanded in the engine or turbine to a pressure lower than the atmospheric pressure. Under this condition, the steam is exhausted into a vessel known as condenser where the pressure is maintained below the atmospheric pressure by continuously condensing the steam by means of circulating cold water at atmospheric temperature.
In a closed vessel, steam is condensed by absorbing the heat and where the pressure is maintained below the atmospheric pressure is known as a condenser. The efficiency of the steam plant is considerably increased by the use of a condenser. In large turbine plants, the condensate recovery becomes very important and this is also made possible by the use of condenser.
The steam condenser is one of the essential components of many modern steam power plants.
Steam condenser are of two types. They are
1. Surface condenser and
2. Jet condensers
Comparison between surface condenser and jet condenser can be in aspects like floor space, power input for air pump and water pump, construction, maintenance and efficiency.
|1||In jet condenser cooling water and steam are mixed up.||In surface condenser cooling water and steam aren’t mixed up.|
|2||Requires small floor space.||Requires large floor space.|
|3||The condensate cannot be used as feed water to boiler unless it is free from impurities.||The condensate can be used as feed water to boiler as it is not mixed with cooling water.|
|4||For jet condensers more power input is required for air pump.||For surface condenser less power input is required for air pump.|
|5||Less power input is required for water pump.||More power input is required for water pump.|
|6||Requires less quantity of coolant (water) for cooling purpose.||Requires large quantity of coolant (water) for cooling purpose.|
|7||The condensing plant is simple for construction and maintenance.||The condensing plant is complicated for construction and maintenance.|
|8||Not suitable for high capacity plants due to low vacuum efficiency.||Suitable for high capacity plants as vacuum efficiency is high.|