Can steam engines use an alternative to water and what effect on efficiency would that have.?
Water causes problem in steam engines because of corrosion and emulsification of the lubricating oil. If it were possible to use an oil this would solve these problems.
Answers:
you would need another fluid that would easily boil, be stable (not combust), be non-toxic since it may leak, and be readily available for it to be workable. As far as i know water is the only thing that fits the task.
no oil would not work, the heats required would bake the oil to the surfaces of the tubes in the boiler providing steam to the engine preventing heat transfer,oil contamination is a serious problems in boiler even a small amount of contamination can seriously damage the boiler. Steam boilers have been around in one form or another since the ancient Greek times and only water has successfully worked, The US Navy and Foster Wheeler did tests but found no other liquid suitable.
Corrosion can be kept at bay with suitable water treatment, but most marine boilers are designed with a life span between 9 & 15 years, I am just retubing one now that is 25 years old
The steam engine is an example of a heat engine so many alternatives could be used instead. Air has been used in many such engines and in theory you could use a chemical like 'freon' which used to be used in refrigerators. None has been as efficient as water as it has a very high specific heat capacity. Most of the alternative liquids have problems mentioned in the alternative answers.
I suppose R-134a, alcohol, and acetone would all work. The advantage of a water steam system is that it can start at ambient pressure without becoming a gas too quickly. If one were to adjust the pressure accordingly, one could get a nearly arbitrary boiling point desired for a particular operating point. Be sure to investigate boiling heat transfer. Surface imperfections are a very important detail often overlooked.
How to answer this?
Steam as you appear to think of it is low pressure wet steam first used by the original steam engines of yesteryear, about 150 of them. Further down the time line came multi pistons multi pressure steam which was still steam when made to concentrate.
The pistons were driven by high, medium and low pressure steam where the latter was lower than atmospheric pressure.
Yes. A leak was air going in and not steam coming out.
Enter steam turbines using dry steam that was invisible but had the cutting power of a saw if you stumbled across it.
Nothing can be used and reused like steam where its useful stages are measured, - Superheated Dry, Dry, Dry Wet, Wet and Boiling Water. I have maintained all of these and never had piston trouble on any for the three years I was working there.
And this included a two-hundred year old Beam Engine.
Location - Met Water Board Lee Bridge London 1948-50
For low-temperature work (as in the final stages of a power plant) say below a hundred degrees C, various organic liquid/vapour systems work well enough. For high-temperature work, mercury has been used. (The mercury condenser boils water, which is used to drive turbines in later stages) But confining the mercury is very difficult since tiny leaks expose the operators to dangerous levels of mercury vapour, it being an accumulating poison.
The prime determinant of thermal efficiency is the temp. in and out. The nature of the working fluid is irrelevant. It comes down to a matter of convenience, and water is convenient. Though high-temperature steam starts to break down into hydrogen, and hydrogen makes metals brittle, a problem for turbine blades.
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Answers:
you would need another fluid that would easily boil, be stable (not combust), be non-toxic since it may leak, and be readily available for it to be workable. As far as i know water is the only thing that fits the task.
no oil would not work, the heats required would bake the oil to the surfaces of the tubes in the boiler providing steam to the engine preventing heat transfer,oil contamination is a serious problems in boiler even a small amount of contamination can seriously damage the boiler. Steam boilers have been around in one form or another since the ancient Greek times and only water has successfully worked, The US Navy and Foster Wheeler did tests but found no other liquid suitable.
Corrosion can be kept at bay with suitable water treatment, but most marine boilers are designed with a life span between 9 & 15 years, I am just retubing one now that is 25 years old
The steam engine is an example of a heat engine so many alternatives could be used instead. Air has been used in many such engines and in theory you could use a chemical like 'freon' which used to be used in refrigerators. None has been as efficient as water as it has a very high specific heat capacity. Most of the alternative liquids have problems mentioned in the alternative answers.
I suppose R-134a, alcohol, and acetone would all work. The advantage of a water steam system is that it can start at ambient pressure without becoming a gas too quickly. If one were to adjust the pressure accordingly, one could get a nearly arbitrary boiling point desired for a particular operating point. Be sure to investigate boiling heat transfer. Surface imperfections are a very important detail often overlooked.
How to answer this?
Steam as you appear to think of it is low pressure wet steam first used by the original steam engines of yesteryear, about 150 of them. Further down the time line came multi pistons multi pressure steam which was still steam when made to concentrate.
The pistons were driven by high, medium and low pressure steam where the latter was lower than atmospheric pressure.
Yes. A leak was air going in and not steam coming out.
Enter steam turbines using dry steam that was invisible but had the cutting power of a saw if you stumbled across it.
Nothing can be used and reused like steam where its useful stages are measured, - Superheated Dry, Dry, Dry Wet, Wet and Boiling Water. I have maintained all of these and never had piston trouble on any for the three years I was working there.
And this included a two-hundred year old Beam Engine.
Location - Met Water Board Lee Bridge London 1948-50
For low-temperature work (as in the final stages of a power plant) say below a hundred degrees C, various organic liquid/vapour systems work well enough. For high-temperature work, mercury has been used. (The mercury condenser boils water, which is used to drive turbines in later stages) But confining the mercury is very difficult since tiny leaks expose the operators to dangerous levels of mercury vapour, it being an accumulating poison.
The prime determinant of thermal efficiency is the temp. in and out. The nature of the working fluid is irrelevant. It comes down to a matter of convenience, and water is convenient. Though high-temperature steam starts to break down into hydrogen, and hydrogen makes metals brittle, a problem for turbine blades.
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