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43 votes

Why use steam instead of just hot air?

Because boiling a volume of water creates a much bigger volume of steam this volume increase is about 1700 times. According to the gas laws doubling the absolute temperature of a volume of gas only ...
ratchet freak's user avatar
37 votes

Why did steam locomotives not transfer power by cogwheels?

Steam piston engines can generate a lot of torque from stationary and the pistons can be physically remote from the boiler, so in most cases it is most convenient to have the pistons directly drive ...
Chris Johns's user avatar
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27 votes
Accepted

Why use steam instead of just hot air?

I would say that using a warm pressurized gas is not very feasible. Ratchet freak already mentioned how you can get much more volume out of heating water into steam than just heating up air until it'...
JMac's user avatar
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15 votes

Why use steam instead of just hot air?

Hot air engines are feasible, and have a 200 year history behind them, starting in 1816 with the Reverend Robert Stirling. The other answers are largely correct : steam offers more energy per unit ...
user_1818839's user avatar
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14 votes

Why did steam locomotives not transfer power by cogwheels?

Here is a picture of the crankshafts inside a modern internal combustion engine: The purpose of these is to convert the back-and forth motion of the piston into rotational motion. It's very much the ...
N. Virgo's user avatar
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12 votes
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Why did steam locomotives not transfer power by cogwheels?

I would like to point out that modern cars do not use cogwheels for transmission, they use shafts. Cogwheels are used for the gearing and differential. But bar mechanisms were used mostly because ...
joojaa's user avatar
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10 votes

Why use steam instead of just hot air?

There are really countless possible answers to this. I'd like to add one that hasn't been made clear yet. If you are doing a closed cycle, where you aren't letting steam/gas out into the atmosphere, ...
Cort Ammon's user avatar
9 votes
Accepted

Why use steam water and not other fuild in steam engines?

There's some interesting information on a number of alternative working fluids here, including ammonia, alcohol, mercury, sulpur dioxide, freon, and many others. Refrigerants are used today in ...
Mark's user avatar
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7 votes

Why use steam instead of just hot air?

While toy steam engines often require that one pre-fill the boiler, and then only operate until the boiler is nearly empty, most practical steam engines require that every gram of steam which leaves ...
supercat's user avatar
  • 369
7 votes
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On steam locomotives with six driving wheels, why are the rear set of wheels placed further apart from the other two?

In the ones pictured, there are no trailing axles - they are a 2-6-0 and a "tenwheeler" 4-6-0 respectively. The ones shown have the firebox between the two rear drive axles. .That was an ...
Phil Sweet's user avatar
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5 votes

Why did steam locomotives not transfer power by cogwheels?

for a while, steam locomotives actually used gears and cylinder/piston sets which drove crankshafts. These were called geared locomotives and they were used to haul heavy loads up particularly steep ...
niels nielsen's user avatar
4 votes

Why is more steam required to turn a steam turbine when electric power consumption is higher

Because you can't get something for nothing? If the generator is generating more electrical power then that energy has to come from somewhere. The more power you try to pull from a generator the ...
Andrew's user avatar
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4 votes

Why use steam instead of just hot air?

Do a web search on "Rankine cycle". The real key is that in a practical heat engine, you need to pump in cold working fluid, heat it, let it do work (and cool) as it expands, and then repeat. If you ...
TimWescott's user avatar
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4 votes

Why use steam instead of just hot air?

For Air: Consider the ideal gas law PV = nRT rearranged to be V = (nRT)/P. n and R are considered constant, and for our purposes, P is also constant. Thus, to increase the volume, (i.e. create a ...
Jerm's user avatar
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4 votes

Why did steam locomotives not transfer power by cogwheels?

Steam generates full torque at zero speed as has been mentioned elsewhere, so like in an electric car (which has very much the same sort of characteristic), there is little to be gained from a gearbox,...
Dan Mills's user avatar
  • 251
4 votes

estimating the surface area of a steam coil immersed in a tank

One thing to consider is that pipes used for heating like this are normally « finned » to increase the surface area - fins can be small discs fitted to the pipe or even wire loops - both increase the ...
Solar Mike's user avatar
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4 votes

Why do steam and diesel engines have differing cylinder configurations?

The maximum efficiency of either the Diesel or a steam engine cycle is (assuming you can treat steam as an ideal gas): $$\eta_{Diesel} = 1 - \frac{1}{(\frac{V_{Max}}{V_{Min}})^{k-1}} \left[\frac{r_c^...
Mark's user avatar
  • 5,333
4 votes

Why use steam instead of just hot air?

As said, boiling water creates much more gas. To make a useful engine for the kind of applications that steam engines are used in, you want to build lots of pressure to be able to move heavy stuff, e....
The_Sympathizer's user avatar
4 votes

Were steam locomotive fitted with centrifugal governor?

A governor is a poor application for steam locomotives because the throttle is constantly adjusted by the driver. Speeds, loads, and steam pressure change constantly, plus a major part of driving a ...
Tiger Guy's user avatar
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4 votes

On the steam locomotives, why was the driver's cabin not located in the front of the boiler for better visibility?

There have been some locomotives with this design, it's called "Cab forward." As the article says, Southern Pacific railroad in the US had some cab forward locomotives, which solved crew ...
Ward - Trying Codidact's user avatar
3 votes

Rate of flow of steam going from one pressure to another

You can use the Hagen-Poiseuille equation to determine the flow rate as a result of a pressure gradient. A caveat in using this equation is that the flow has to be laminar, i.e. inertial effects can ...
nluigi's user avatar
  • 202
3 votes

Rate of flow of steam going from one pressure to another

You stated that most things you found are too complex for your basic understanding, is it safe to assume that the answer you are seeking may be an educated guess? If so I would go with Bernoulli $$g ...
idkfa's user avatar
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3 votes
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How long a spiral copper tube would need to be in a monotube boiler in order to achieve 0.02 kg of steam per second?

I'm not going to answer your question, because no wall thickness or length of tube will meet your needs. Coiled copper is for cooling something, not for making steam. You can cool hot water by ...
Tiger Guy's user avatar
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3 votes

Which has more density: 100 °C steam or 100 °C dry air?

There's an air of 'lmgtfy' about this question... Wolfram Alpha is a great resource for quickly finding information like this. You can see that the steam is significantly less dense than the air, at ...
Jonathan R Swift's user avatar
2 votes
Accepted

Why do steam and diesel engines have differing cylinder configurations?

Steam engines can expand the steam only so much before the water vapor starts to condense. In addition, the volume of the vapor increases significantly as it expands, making it difficult to obtain ...
user16622's user avatar
  • 314
2 votes

How to protect a pressure gauge from condensation in a vacuum steam boiler?

Have you tried a gauge guard? It's a simple diaphragm that allows pressure to transmit, without the liquid crossing the barrier.
Mark's user avatar
  • 5,333
2 votes

Why do steam and diesel engines have differing cylinder configurations?

The difference of few large cylinders or many small cylinders has less to do with running on steam or diesel, but more with the era in which the engines were built. Early engines (both steam and ...
JanKanis's user avatar
  • 254
2 votes

How did the snifting valve in Newcomen's steam engine work?

The snifter valve allowed air and some steam to escape - this did not differentiate between air and steam, just opened briefly when steam was entering. See https://en.wikipedia.org/wiki/...
Solar Mike's user avatar
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2 votes

Determining gas properties in a steam and air gas mixture

Considering that air and steam behave as ideal gases, you can write the following equations: $$ P V = nRT $$ $$ P_A V = n_A RT$$ $$ P_W V = n_W RT $$ where I use subscripts $_A$ and $_W$ for air and ...
Toulousain's user avatar
2 votes

How to calculate saturated steam flow rates?

With steam in general and absolutely with any phase changes and pressure changes, you need to use enthalpies instead of specific heat. If there are phase changes, specific heat neglects the enthalpy ...
ericksonla's user avatar

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