The Rankine Cycle

Increasing the Efficiency of the Rankine Cycle
Three ways:
Lowering the condenser pressure
Superheating the steam to high temperatures
Increasing the boiler pressure
Lowering the Condenser Pressure
Lowering the operating pressure of the condenser automatically lower the temperature of the steam, and thus the temperature at which heat is rejected.
The effect of lowering the condenser pressure on the Rankine cycle efficiency is illustrated in figure



EX(1): Calculate the turbine work output and a feed water pump work input of fluid for Rankin cycle ,in which steam leaves the boiler at (2 MN/m2),(350? ),the steam exhaust to condenser at ( 7 k N/m2),calculate (?th)?
Cooling Towers
A cooling tower is equipment used to reduce the temperature of a water stream by extracting heat from water and emitting it to the atmosphere. Cooling towers make use of evaporation whereby some of the water is evaporated into a moving air stream and subsequently discharged into the atmosphere. As a result, the remainder of the water is cooled down significantly.
Cooling towers are able to lower the water temperatures more than devices that use only air to reject heat, like the radiator in a car, and are therefore more cost-effective and energy efficient. The makeup water source is provided to replenish water lost in evaporation. Hot water from the condenser is sent to the cooling tower. The water exits the cooling tower and is sent back to the exchanger or other unit to produce cooling
Classification of cooling Towers:
The cooling towers are mainly classified according to the method by which air is introduced into the tower. In order to make the study of towers more convenient there are some other criteria on which the cooling towers may be classified. These classifications are given here,

1) Classification on the basis of direction of air-to-water flow
2) Classification on the basis of air flow generation methods
3) Classification on the basis of Heat transfer methods
Classification on the Basis of Air Flow Generation Methods:
The natural draft cooling tower makes use of the difference in temperature between the ambient air and the hotter air inside the tower. As hot air moves upwards through the tower (because hot air rises), fresh cool air is drawn into the tower through an air inlet at the bottom. Due to the layout of the tower, no fan is required and there is almost no recirculation of hot air that could affect the performance