Decreasing Condenser Pressure Increases Efficiency

Ch 9, Lesson B, Page 9 - Decreasing Condenser Pressure Increases Efficiency

• If we operate the condenser at a lower pressure, QC drops by a large amount and QH increases by a modest amount.
• Both of these effects lead to a higher work output for the cycle and a higher thermal efficiency.
• But, there are a couple of potential problems with this approach to improving the thermal efficiency.
• For starters, the quality of the turbine effluent drops and this can result in damage to the turbine.
• This could be balanced by superheating the working fluid in the boiler.  We will discuss that forther in the next lesson.
• The other problem with reducing the condenser pressure becomes apparent when the operating pressure drops below atmospheric pressure.
• When a piece of equipment operates below atmospheric pressure, any leak will cause air to enter the system.
• This can be devastating.
• It also turns out that building equipment to operate at vacuum pressures, that is pressures below atmospheric, is expensive.
• As a result, it is very unusual to find a condenser in a power plan that operates below atmospheric pressure.