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I was curious if water is the most efficient fluid for use in generating steam power. I thought it might be, since it has the highest latent heat of evaporation of any fluid. I wasn't sure if other properties were more important, though, like he density of the fluid or its boiling point.

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  • $\begingroup$ What is your definition of “efficiency”? $\endgroup$
    – Solar Mike
    Jan 8, 2023 at 7:34
  • $\begingroup$ @SolarMike Producing more net energy/power? That's how I figured efficiency is measured, production. I was curious if something was technically better than water for steam engines. $\endgroup$
    – user27657
    Jan 8, 2023 at 9:18
  • $\begingroup$ Efficiency can be many things, like quickest time or lowest power use. If you are not clear then are ee expected to guess? $\endgroup$
    – Solar Mike
    Jan 8, 2023 at 9:20
  • $\begingroup$ @SolarMike Title has power in it. That's what I mentioned in the comment. Power is in the tags, and in the question description. So I'm not sure how much clearer I can be, or why you need to guess. $\endgroup$
    – user27657
    Jan 8, 2023 at 14:25
  • $\begingroup$ @SolarMike I found this, which defines power efficiency more exactly: rapidtables.com/electric/efficiency.html Sorry for not being more exact about what I meant before, I took it for granted that this is how power efficiency is defined. $\endgroup$
    – user27657
    Jan 8, 2023 at 14:45

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Is it the most efficient? Maybe or maybe not, but it is an outstanding medium to turn into vapor for use in a turbine. It is extremely plentiful, the heat of vaporization is high, and it is easy to work with. It isn't toxic or corrosive and is easy to dispose of. Pumps to work with water are ubiquitous, and cheap to make because you can use the medium to cool the packing - it's generally okay to have a water pump that leaks a bit. The technology to maintain water boiler chemistry is well known and hasn't changed significantly in at least 50 years.

There are other liquids that can be used to transfer heat (brine, glycol, even liquid sodium) but they all have negative qualities and none are used for turning to vapor in a relatively open system, which is what a steam cycle is. Refrigerants are chosen for their properties of evaporation at varying pressures, no one tries to run a turbine with them.

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  • $\begingroup$ These are good points, thank you. I would like to know about the efficiency, though. If there were a liquid with a higher LHoE, would it be more efficient, for example? $\endgroup$
    – user27657
    Jan 8, 2023 at 2:43

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