Why do power plants that use the Rankine cycle use the working fluids:
- sodium
- mercury
- serine
- benzene
- potassium
Can such plants use other fluids?
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$\begingroup$ Do rankine use any of these as working fluids? If you show the source for your claim, you likely have the answer why right there. $\endgroup$– martCommented Jan 13, 2017 at 10:21
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3 Answers
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I doubt many Rankine cycles use any of these as working fluids, if working fluid means the fluid that undergoes the actual phase change etc. Rankine cycle engines want fluids with a convenient boiling point - within the temp. range the machine will operate in, at a managable pressure. Most of the times this is water. Organic Rankine Cycle engines exist, these use fluids with lower boiling point to exploit lower temp. heat sources like industrial waste heat or geothermal sources. The wiki article I linked goes into the choice of the working fluid, with more explanation :
- Isentropic saturation vapor curve
- Low freezing point, high stability temperature
- High heat of vaporisation and density
- Low environmental impact
- Safety
- Good availability and low cost
- Acceptable pressures
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Yes, and the absolutely overwhelming majority of them do. The number that use any of the fluids you listed is trivial. Most use water.
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1$\begingroup$ And even the ones using sodium and potassium mostly use them for heat transfer ... to a water based Rankine cycle. $\endgroup$ Commented Nov 15, 2016 at 13:21
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There used to be utility scale mercury vapor turbines for combined cycle electricity generation. According to that wikipedia page, the increase in efficiency of steam turbines made mercury turbines obsolete.
