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Temperature and Power Plant Output?

  1. Jan 12, 2017 #1
    This is probably a very basic engineering question, but I'm from an energy policy background and the resources I've found (such as this) are quite detailed.

    Internal combustion engines such as automobile engines and aircraft (jet and piston powered) produce more power in colder environments and less power in hotter environments, and I've read descriptions of steam turbine warships being designed with more powerful engines for use in tropical environments to keep their speed competitive. I'm just wondering in general how the output of power plants (internal combustion, Rankine and Brayton cycle, etc.) change in response to the temperature of their environment.
     
  2. jcsd
  3. Jan 12, 2017 #2

    jack action

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    It changes in two ways (for any engine, in power plants or vehicles):

    1. To increase the efficiency of any heat engine (no matter the thermodynamic cycle) you can increase the temperature of the hot source or lower the temperature of the cold sink. The hot source is always as high as possible (combustion), but the cold sink temperature depends on the ambient temperature (you can't cool to a lower temperature). So a higher ambient temperature will reduce the efficiency of any cycle. More on Wikipedia.

    300px-Heat_engine.png

    2. For an engine with an open cycle which uses ambient air as an oxygen source for its combustion, when the ambient air is cooler it is less dense, so it takes less space. This means that you can put more air in the same engine volume (i.e. higher mass flow rate) and burn more fuel with it. This leads to more power. Tough, the engine is not more efficient, it just has the ability to burn more fuel.
     
  4. Jan 13, 2017 #3

    JBA

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    Small correction, this should state "it is more dense"
     
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