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Did the British get the steam engine wrong?
Dennis told us in Philadelphia that Engineers have had the steam engine wrong for hundreds of years. The following is a closer examination of that claim by Tom Napier: Did the British get the steam engine wrong?
Tom Napier says no.
One of Dennis Lee's more amazing claims is that 350 years of steam engine development has been completely wrong. He claims that a more efficient engine can be made by injecting super- heated water, rather than steam, into a cylinder. He also claims that this engine doesn't need a condenser.
The description of this new steam engine is taken from the section headed "The Heat Engine and the ABR" in Lee's booklet, "Finally . . . technology which leaves the competition in the cold." Some relevant material will also be found in the earlier section in the same booklet, "Free energy from the air, a layman's explanation" and "Technical version of the free energy concept."
An explanation of how the conventional reciprocating steam engine works is important background information. A steam engine consists of a Boiler, heated by burning oil or coal, which generates high pressure steam; a Cylinder in which a piston is driven by steam pressure; a Condenser which converts the steam back to a liquid; and a Feed Pump which returns the water back to the boiler. (The engine described here has steam applied to only one side of the piston, some steam engines apply steam alternately to both sides of the piston.)
The piston starts at the closed end of the cylinder. A valve is opened, connecting the cylinder to the boiler. High pressure steam flows from the boiler into the cylinder and forces the piston towards the open end of the cylinder. At this point the cylinder is full of steam at the same pressure and temperature as the steam in the boiler. The valve is closed but, because the steam is at high pressure, it continues to press against the piston. However, as it does so, its pressure drops and it becomes cooler. If the cylinder is long enough the piston will continue to move until the steam pressure drops to atmospheric pressure. A little of the steam may condense to hot water but only a little since condensing steam gives out so much heat that this keeps the rest of the steam in the cylinder too hot to condense.
At this point the piston starts to move back towards the closed end of the cylinder. If we did nothing else the steam in the cylinder would become compressed and would heat up again. Ultimately it will become even hotter than it was when it came out of the boiler. This heat comes from the mechanical energy which we have put into it by pushing the piston in. This is more than the energy we got out when the steam pushed the piston out in the first place so this, obviously, is not a useful engine. (In fact it is a crude heat pump.) We need to do something with the steam in the cylinder.
One thing we could do would be to open a valve and to let the piston push the steam out into the air. If one has lots of water available to refill the boiler, and isn't worried too much about fuel costs, this works well. Early railroad engines did it to save carrying around a condenser. Yes, the other place we can push the unwanted steam is into a condenser. This takes the low pressure (e.g. one atmosphere), low temperature (e.g. 212 F) steam and, by removing heat from it, condenses it back into hot water. To do this it needs to have somewhere cooler to lose heat to. Since the surrounding air is much cooler than 212 F it makes a great place to dump the heat. But where is that heat coming from. Well, water is odd stuff, it takes a huge amount of energy to convert water into steam and every bit of that energy has to be taken back out to convert steam back into water.
This is why the steam in the cylinder doesn't condense on its own. It takes 970 Btu of energy to convert one pound of water into steam and you have to take back out 970 Btu to convert one pound of steam into water. To put this into perspective, suppose we had a pound of steam in our cylinder and 1% of it condensed into water. That would give out 9.7 Btu which is sufficient to raise the temperature of the remaining steam by about 25 degrees. This is going to stop any more steam from condensing.
Since the condenser can dispose of this excess heat it converts the steam to water and its pressure remains low. When we open the valve to the condenser the piston is actually sucked towards the closed end of the cylinder, extracting a little more energy from the cycle. That valve is then closed, the valve to the boiler is opened and the cycle restarts. This is called the Rankine cycle in books on heat engines.
However, there is a more subtle reason why we want to condense the steam. In a closed system the average amount of water in the boiler remains the same. High pressure steam leaves the boiler but if we pumped high pressure steam back into the boiler this would take just as much energy as we got from the steam leaving the boiler; we wouldn't have gained anything. However, if we pump in water, condensed steam, we have to generate just as much pressure to get the water to flow in but the total volume is much lower. The energy required to pump in a low volume (water) at a high pressure is much less than the energy released by letting out a high volume (steam) at the same pressure. We end up with left over energy.
A conventional steam engine could operate with a boiler temperature up to 705 F; the pressure is high enough to stop the water all boiling. Above this temperature the water will not remain liquid, no matter how much pressure is applied.
Now Lee's "improved" steam engine works as follows (All of this is taken directly from his own literature.): It uses a rotating valve mechanism to inject a "shot glass" of water at 700 F into the cylinder. This "flashes into steam" and drives the piston. "The volume is thus increased and work is expended, so that the temperature of the water is now lower than the boiling point at that little pressure and the steam condenses into a liquid, falling out a weep hole in the bottom of the shaft as much cooler liquid, to be recycled, with no condenser necessary." Well, if that's not wishful thinking, I don't know what is.
Flaw number One. Water at 700 F (which would be under a pressure of 218 atmospheres) is not going to "flash into steam" when the pressure is released. Remember, it takes 970 Btu to convert a pound of water into steam. To make the numbers easy, let's assume we start with a pound of hot water (OK, it's a beer mug, not a shot glass.) That water needs to get 970 Btu from somewhere before it can become steam. This heat can't come from the water, 970 Btu would cool it by 970 degrees and we'd end up with a block of ice in our cylinder. It can't come from the cylinder unless it is even hotter than the boiler.
So perhaps some of the water will become steam. As that steam expands it will cool down; that's not going to supply any heat. Let's ignore that factor for the moment and suppose that we end up with some water and some steam at one atmosphere pressure and 212 F. The 700 F water has cooled by 488 degrees so we got 488 Btu out of it. That's enough to convert just over half the water to steam so we end up with a cylinder containing half a pound of steam and half a pound of hot water. An exact calculation would take some messy calculus and better steam tables than I have but the general idea is that we won't get much energy out of that shot glass of hot water.
Flaw number Two. So we have expanded down to one atmosphere and we have a mixture of steam and water. What's going to happen to it? Well we can pump the water back into the boiler but that's going to leave a cylinder with a lot of steam in it at 212 F. It's not going to condense, it's just going to sit there. No amount of hand-waving about "the temperature of the water is now lower than the boiling point at that little pressure" is going to do away with the need to extract heat from the steam to condense it.
Perhaps James Watt knew what he was doing after all. Before he invented the condenser, steam engines sprayed cold water into the cylinder to condense the steam but they had to be built near coal mines because they used so much fuel.
Now this argument is based on water since that is what Lee has specified in his description. However, since he can't get 700 F out of his heat pumps he wants to use a refrigerant as his working fluid so he can run the boiler at 250 F instead. While the numbers will be different the same general principle applies; it takes a lot of energy to convert a liquid into a gas and the same amount has to come back out to convert it back again.
The only way to avoid using a condenser is to run with an open cycle like the early steam trains. Now the working fluid becomes a non-renewable resource. If it is water, it doesn't cost much to replace it but if it is a refrigerant, once the tank is empty the engine will stop. (Beware of engine demonstrations which stop after a few minutes, any low boiling point liquid will drive an engine; until there's none left!)
Oddly enough, the idea that the working fluid would condense on its own is not new. In 1881 an inventor named John Gamgee tried to sell his "zeromotor" to the US navy. He proposed to boil ammonia (the best available refrigerant in those days) with the heat from sea water. No problem with that, ammonia has to be kept cold or under pressure to keep it a liquid. He too thought that the ammonia gas in the cylinder would become a liquid again on its own accord and that it could then be pumped back into the boiler. He may even have been able to demonstrate a working model, until the ammonia ran out. The last I heard, the US Navy was still using oil or nuclear reactors to drive their ships.
Any heat engine can, at best, go round a Carnot cycle. Its best possible efficiency is (Thot-Tcold)/Thot. If Thot comes from a heat pump, its best possible CoP is Thot/(Thot-Tcold). These two expressions cancel; in reality the energy out will always be less than the energy in.
Copyright © 1997, T. M. Napier
back to Eric's main Dennis Lee page
This page has been hit times. since Sept 24 1996.
Comments can be sent to firstname.lastname@example.org I'm happy to publish critical responses to my claims.
The above page got the following response:
I'm reading the
materials that attempt to refute Dennis Lee's claims and I'm seeing
tremendous gaps in logic. The article by T.M. Napier, by the way, at
http://www.phact.org/e/dennis31.htm, is just full of holes. He
explains, for example, that, "Remember, it takes 970 Btu to convert a pound
of water into steam." But he completely misses the important point: that's
only true at sea level pressure! At much higher pressures, it takes
significantly more Btus to convert water into steam. Thus, at 218
atmospheres, we're talking tens of thousands of Btus. Mr. Napier seems to
have no clue whatsoever as to what he's talking about.
He then goes on to say, "That water needs to get 970 Btu from somewhere
before it can become steam." This is simply not true. You can turn water to
steam by lowering the pressure of the container (expanding the volume). You
don't have to add energy. Is Napier brain dead here, or am I missing
He furthermore misses the whole point about *volume* and *pressure*. As the
volume of the cylinder expands, the pressure drops, and if dropped far
enough, the steam condenses. This is a no-brainer, and yet high-and-might
Napier missed it outright!
At this point, I find Napier's rantings no more credible than Lee's. If this
is the refutation from the "educated" science mind, I tend to agree with
Lee's assessment that modern science is blind and brainwashed. I was hoping
to find more credible information on your site, but so far, all I find is
snobby-sounding hogwash from so-called scientists. How can they hope to
refute free energy charlatans if they don't even understand physics
==================== the following response is from Tom Napier:
Subject: Problems with the Fischer engine
Date: 30 Aug 1999
You have perfectly demonstrated the dilemma faced
by the scientific
skeptic. He can explain a subject in rigorous detail with all the
exceptional cases and provisos mentioned; this loses the reader's interest
rather quickly. The alternative is to simplify things and to concentrate
on the main point. This suits most readers but is frequently pounced on
by the hypercritical. As the argument goes, what the skeptic wrote does
not apply in every special case therefore everything he has written can be
You say, "At much higher pressures, it takes
significantly more Btus to
convert water into steam." This is simply wrong. The latent heat of
vaporization of water (also called the enthalpy of vaporization) is not
directly affected by the pressure. Raising the pressure raises the
temperature at which water boils. The latent heat is roughly inversely
proportional to the absolute temperature. (Reference, the CRC Handbook of
Physics and Chemistry.) Over normal temperature ranges this effect can
be ignored, which is what I did in my article. At 572 F (300 C), for
example, it takes about 40% LESS heat energy to vaporize a pound of water
than it does at 212 F. The 218 atmospheres you quote is the critical
pressure of water, at which point the water is at a temperature of 705 F.
It then requires negligible energy to convert it to a vapor at the same
temperature and pressure. This is very different from the "tens of
thousands of Btus" which you mention. However, as soon as the piston
moves the pressure and temperature will fall and it will require a
significant input of additional heat energy to convert the water to steam.
This energy can only come from the water itself, cooling it. As I showed
in my article, there is insufficient energy in the water to convert more
than a fraction of it to steam even if the pressure is reduced to
atmospheric pressure. Thus my article was qualitatively correct even if
the numbers were not exactly right.
Your third paragraph ("the pressure drops,
and if dropped far enough,
the steam condenses.") contradicts your second one ("You can turn water to
steam by lowering the pressure of the container (expanding the volume).")
Presumably you are referring to adiabatic expansion in the first case and
to expansion at constant temperature in the second case. I worked out an
example just to check this.
Suppose you start with steam at one atmosphere and
100 C. If you lower
its pressure adiabatically to, say, half an atmosphere its temperature
will fall to approximately 45 C. The vapor pressure of water at 45 C is
about 0.093 of an atmosphere so that at 0.5 atmospheres pressure some
steam will condense. Of course the real situation is much more
complicated since the condensing steam gives out heat and at the same time
reduces the pressure. I'd probably have to write a simulation program to
see what really happens and that's too much trouble. By definition,
adiabatic expansion requires no external heat energy but in this case you would
need to do work against atmospheric pressure to cause the expansion.
During adiabatic expansion the gas may do external work or require external work, depending on the external pressure, but no heat energy enters or leaves the gas.
In the second case, suppose you had water at, say,
20 C. Its vapor
pressure is about 0.023 atmospheres. You can convert it to steam (or
water vapor, I'm using both terms interchangeably) at 20 C by doing work
to reduce the pressure below 0.023 atmospheres and by supplying more heat
at 20 C.
By the way, you have to be very careful what you
mean by "lowering the
pressure." It can mean allowing a gas, e.g. steam, to expand and to do
work, as in a steam engine. It can also mean applying an external source
of energy to reduce the pressure of the gas. The first converts heat
energy into mechanical energy while the second converts mechanical work
into heat energy by cooling the gas. If you want to convert the steam
back into water (so you can pump it back into the boiler) you either have
to cool it or compress it or both.
There is no magic way of completing the cycle in a
steam engine which
can make it more efficient than the thermodynamic limit given by the input
and output temperatures. Neither is there any way to get round the second
law of thermodynamics and to extract net energy from the environment.
Tom Napier (Whose neurons have not yet all
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