Superheating the steam is done by increasing the time the steam is exposed to the flue gases. In a similar way, if the steam is superheated in the boiler, it is evident that the work is increased by area 3-3′-4′-4-3 (see diagram below): Effect of superheating If the exhaust pressure drops from P 4 to P 4‘ with the corresponding decrease in temperature at which heat is rejected in the condenser the net work is increased by area 1-4-4′-1′-2’-2-1 (see diagram below) Effect of exhaust pressure Improvements to the Rankine Cycle Efficiency Effect of Pressure and Temperature on the Rankine Cycle Referring to the diagram above and using the enthalpy values in the Rankine cycle, we can write: Rankine Cycle Efficiency then can be expressed as: In addition, feed pumps consume energy thus reducing the net work output. The Rankine Cycle EfficiencyĪs noted above, some heat is always lost from the steam to cooling water. This thermodynamic cycle is known as the Rankine Cycle. The pressure of the condensate leaving the condenser is increased in the pump thereby enabling the condensate to flow into the boiler. The exhaust steam leaves the turbine and enters the condenser where heat is transferred from the steam to cooling water. The steam expands in the turbine and does work which enables the turbine to drive the electric generator. High-pressure steam leaves the boiler and enters the turbine. A schematic diagram of a simple steam power plant is shown below: Schematic diagram of a steam power plant With the cooling water temperature very high (lake water temperature: 35☌),Įxcluding hydroelectric power plants, most power generating plants employ a type of boiler and steam turbine. ![]() ![]() Operate the Plant at full generating capacity and compute the Power Plant Efficiency when the plant is operating:
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