Thermal efficiency of a closed cycle power developing system using steam as working fluid and working on Carnot cycle is given by an expression (T1 – T2)/T1. This expression of efficiency shows that the efficiency increases with an increase in temperature Tl 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) can be reduced to the atmospheric temperature if the exhaust of the steam takes place below atmospheric pressure. If the exhaust is at atmospheric pressure, the heat rejection is at 100°C.
Low exhaust pressure is necessary 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 atmosphere by continuously condensing the steam by means of circulating cold water at atmospheric temperature.
A closed vessel in which steam is condensed by abstracting the heat and where the pressure is maintained below 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 all modern steam power plants.
Steam condenser are of two types:
1. Surface condenser.
2. Jet condensers
No comments :
Post a Comment