Superheating the Steam to High Temperatures

Superheating the Steam to High Temperatures:
The average temperature at which heat is added to the steam can be increased without increasing the boiler pressure by superheating the steam to high temperatures. Superheat allows heat addition at average temperature than using saturated steam only. From Carnot analysis this should result in higher cycle efficiency .A turbine operating with less moisture is more efficient and less prone to blade damage .
Note: superheating : ?is of turbine increase and less blade damage.

• Superheating the steam to higher temperatures has very desirable effect: It decreases the moisture content of the steam at the turbine exit as can be seen in T-s diagram.
• The temperature to which steam can be superheated is limited by metallurgical consideration.
Increasing the Boiler Pressure
• The average temperature during the heat addition process is to increase the operating pressure of the boiler, which automatically raises the temperature at which boiling take place.
• This, in turn, raises the average temperature at which heat is added to the steam and thus raises the thermal efficiency of the cycle.
• This, in turn, raises the average temperature at which heat is added to the steam and thus raises the thermal efficiency of the cycle.


EX(2): A steam power plant operates between boiler pressure of (42 bar) condenser pressure (0.036 bar) .Calculate the cycle performance if the steam is sup
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