Stirling Engine Thermodynamics

[Tom Booth]

None of my razzes on you have been edited out...

Sorry, you are right, what I was referring to is still there:

"That would be a bold statement by someone too lazy to do the research and discover what makes the power piston move. When you bring your theory here Tom to the form, and someone calls you out about it, we would think you would have a fundemental understanding on the hows & whys Stirling engines work to hold up your end. When you are done shoveling snow spend an hour to find out!"

The reason I thought you had removed it was that I was using - Edit > Find - to locate the word "forum" in your post which happened to have a typo ("form" instead of forum).

What irks me to some degree is your apparent arrogance in assuming that because I am trying to bring out a rather obscure and apparently not widely recognized thermodynamic principle as it relates to the functioning of a Stirling engine, which you apparently are unable to comprehend or appreciate, that I need tutoring in basic Stirling engine operation and principles.

In your last post, you are still continuing in the same vein:

"I do understand there are those who come to the forum without the Stirling cycle understanding. You have been accommodated here."

On the contrary, if anything, I know that the principles I'm trying to get across are rather difficult to understand so I have tolerated your disparaging comments and belittling attitude toward me and/or the subject.

This thread was started with the intent of discussing thermodynamic principles as they relate to Stirling Engines. It is not entitled "Stirling Engine Basics" or "Guess how a Stirling Engine works".

As I've already stated in reply to "theropod2":

If you go back and read my first post in this thread, I've already given a very brief outline of the basic complete Stirling cycle. I see no need to go into exhaustive detail in regard to a subject everybody is already well aware of.

I would not insult the intelligence of anyone here on this forum by talking down at them as if they needed tutoring in regard to the basic principles of how a Stirling Engine works. If they don't know, then they can easily find out as this information is readily available at the click of a mouse button.

Discussing the "complete Stirling Cycle" is, IMO, a waste of time here and completely unnecessary and largely irrelevant to the topic. Presumably, everyone in here already knows the basics.

Please stop assuming I don't just because you apparently cannot understand or do not agree with the points I am trying to get across.

[Longboy]

The load must be applied gradually to give the engine time to adjust rather than causing it to stall.

Generally, people tend to run a model Stirling engine without a load, without doing any work, and as you have described previously, it does not seem possible to have such an engine do any additional work other than keeping itself going because it lacks torque.

But the reason it lacks torque is because it has been allowed to run in a no-load condition. As explained in this paper, under such no-load circumstances, the engine speeds up and its potential for power output (torque) "drops to zero".

If a load is applied gradually, then the engine will "grow stronger".

The reason that this happens is that the excess heat which was reducing the temperature differential in the no-load condition is now being diverted to power the load. As a consequence of the heat now being converted into work, less heat reaches the heat sink and the temperature differential increases. As the load is gradually increased so the temperature differential increases and so the torque increases.

In models this transition time from first revolutions to full capacitys is a matter of seconds. In a workhorse low torque Stirling these operating instructions provide for that shortcoming and state the neccesity of gradually feeding in the load. The flywheel may not have the momentum to carry it over till the heat energy is at opperational minimums. There is not much of a reserve and it takes several minutes to bring these industrial size Stirlings up to their opperational temperatures. They do not rival a typical lawnmower engine but their versatility of many fuel sources to provide its heat input is its ace in the hole. I agree with the no load/ torque reasoning but with other explanations. For an engine not under load has no reason to display its greater torque cappacities. When they dyno a car engine, at 5000 rpm with no load its torque reading is much less than a reading taken at the same rpm under a loaded condition. Temperatures go up under load but the radiator carries the waste heat away. This works for Stirling too! As for a change in the temp differential in a Stirling pulling a load I'm not convinced. I would say its load increase would have to be balanced with more heat input, this equalibrium would not change the heat differential. Its radiator would be enough for its opperational duties. If the radiator capacity is not enough, the internal temps rise and the coresponding affect on the temperature differential is now apparent.

[Tom Booth]

In models this transition time from first revolutions to full capacitys is a matter of seconds.

And, so... This proves what?

In a workhorse low torque Stirling these operating instructions provide for that shortcoming and state the neccesity of gradually feeding in the load. The flywheel may not have the momentum to carry it over till the heat energy is at opperational minimums. There is not much of a reserve and it takes several minutes to bring these industrial size Stirlings up to their opperational temperatures. They do not rival a typical lawnmower engine but their versatility of many fuel sources to provide its heat input is its ace in the hole.

Again, what's your point?

I agree with the no load/ torque reasoning but with other explanations.

Like what ?

For an engine not under load has no reason to display its greater torque cappacities.

So is this your explanation ?

When they dyno a car engine, at 5000 rpm with no load its torque reading is much less than a reading taken at the same rpm under a loaded condition. Temperatures go up under load but the radiator carries the waste heat away. This works for Stirling too!

If the rpm is the same under load, then someone must have stepped on the accelerator.

A Stirling running on a candle has no such mechanism.

The energy/heat input on a Stirling is not generally variable. It doesn't have a gas peddle.

You keep making this comparison. Stepping on the gas to get up hill etc. in an internal combustion engine. It does not apply to the situation I'm describing with a Stirling where the heat/energy input is constant but the work load is variable.

As for a change in the temp differential in a Stirling pulling a load I'm not convinced. I would say its load increase would have to be balanced with more heat input

Again, I'm referring to a situation where the heat input is constant.

You can't just manufacture heat out of thin air to bring about a balance. The extra heat to pull the load has to come from somewhere, but not the heat source as that is not variable. It has to come from the excess waste heat, if there is any. If the engine has been running with no load, there surely would be waste heat.

this equalibrium would not change the heat differential

I think it would.

A portion of the heat that was previously just running through the engine and going to waste and winding up at the heat sink, under a load, would be redirected to do work and the heat would "disappear" never reaching the heat sink.

If the heat no longer exists, if the heat is gone, if the heat has disappeared, if it is no longer going to waste and just running straight to the heat sink, increasing the temperature of the heat sink, and the heat input remains constant, then the engine would have to run cooler and more efficiently.

How could it run hotter if the heat has disappeared and no additional heat has been added ?

If the heat has disappeared by being converted into work, then it is gone. Less heat reaches the heat sink.

Its radiator would be enough for its opperational duties. If the radiator capacity is not enough, the internal temps rise and the coresponding affect on the temperature differential is now apparent.

You are apparently still thinking in terms of a gasoline, internal combustion engine where when more power is needed you step on the gas and burn more fuel and the heat input increases.

In a Stirling with a steady invariable heat source, like a candle, this is impossible.

That VITA reference I quoted does not say anything about stoking the fire to get more work out of the engine. It says nothing about increasing the heat input in any way. It says apply a load and the engine will "grow stronger" automatically.

The only way to increase the power in a Stirling is by increasing the temperature differential.

If applying a load makes the engine "grow stronger", the logical conclusion is that the temperature differential has increased upon applying a load.

The heat input has not changed. Therefor the amount of heat being lost to the heat sink must have changed.

The only logical explanation is that between the heat source and the heat sink, the heat has disappeared somewhere.

Where do you suppose it went?

It was converted into work!

[Tom Booth]

Just to show that this concept of heat being converted into work and therefore "disappearing" before it ever reaches the heat sink, (or cold end of the displacer chamber) is not just some idea I dreamed up, here are a few additional references:

I would like to emphasize that this is generally not something I've ever seen mentioned in any of the explanations I've ever read about basic Stirling engine operation. Why it isn't emphasized more often, I don't know. It seems to me to be a very important point to have in mind, especially in relation to engine efficiency and potential for power output. The more heat that can be converted into work, the less heat reaches the heat sink, the easier it is to maintain the temperature differential.

If the engine is run without a load, since relatively little heat is required to keep the engine running, there would then be a great deal of excess heat that would need to be gotten rid of necessitating a disproportionately large radiator, or some other means to use up or get rid of all the excess heat, such as restricting the heat input.

If you are interested in Stirlings for their utility as power producing engines then I think it is important to understand how and why these engines need a little coaxing in order to redirect the heat flow from the heat sink to the power output.

Carnot... showed that heat does work only by being let down from a higher to a lower temperature . But Carnot had no idea that any of the heat disappears in the process, and it was not until the doctrine of the conservation of energy was established in 1843 by the experiments of J . P . Joule that the theory of heat engines began a vigorous growth

http://encyclopedia.jrank.org/SOU_STE/STEAM_ENGINE.html

In the 1840s, scientists such as William Thomson (Lord Kelvin) and James Prescott Joule showed that when mechanical energy is generated from heat, a proportional amount of the heat disappears. The equivalence of work and heat as interconvertible forms of energy became the foundation for what is referred to as the first law of thermodynamics.

http://www.newworldencyclopedia.org/ent ... adi_Carnot

The Science of Thermodynamics treats of the relation of heat to mechanical work. In its engineering aspect it is chiefly concerned with the process of getting work done through the agency of heat. Any machine for doing this is called a Heat-Engine.

It is convenient to study the thermodynamic action of heat engines and refrigerating machines together, because one is the reverse of the other, and by considering both we arrive more easily at an understanding of the whole subject.

...In a Heat-Engine heat is supplied,... at a high temperature, and the engine discharges heat at a lower temperature... In any kind of heat-engine the heat is let down, within the engine, from a high level of temperature to a lower level of temperature, and it is by so letting heat down that the engine is able to do work, as a water-wheel is able to do work by letting water down from a high level to a lower level. But there is this important difference, that some of the heat disappears in the process of being let down: it is converted into the work which the engine does.

...Much greater efficiency can be obtained by using a fluid for working substance and by making it act so that its own expansion of volume not only does work but also causes it to fall in temperature before it begins to reject heat to the cold receiver.

...any work that it has done must have been done at the expense of heat which it has taken in during the cycle...

Heat taken in = Heat rejected + Work done by the substance.

The First Law of Thermodynamics. The principle of the Conservation of Energy in relation to heat and work may be expressed in the following statement, which constitutes the First Law of Thermodynamies:" When mechanical energy is produced from heat a definite quantity of heat goes out of existence for every unit of work done...

Thermodynamics for engineers By Sir James Alfred Ewing

The law of conservation of energy states that energy can neither be created nor destroyed. Since heat is a form of energy, when a certain quantity of heat disappears from one body it will be found to have transferred itself to some other body, providing that it has not been changed into some other form of energy. This statement of the law of conservation of energy applied to heat is called the first law of thermodynamics.

ESSENTIALS OF Applied Physics

By ROYAL M. FRYE, Ph.D. Professor of Physics, Boston University

When work is transformed into heat or heat into work,
the 'quantity of work is dynamically equivalent to the
quantity of heat.

It has also been expressed in this way :

"When equal quantities of mechanical effect are produced by any means whatever from purely thermal sources,... equal quantities of heat are put out of existence... " (Kelvin).

This law has been confirmed in a variety of ways :

1. The experiments of Joule, Rowland, and others in generating heat by the expenditure of work.

2. The experiments of Him and others, showing that when work is done by a heat-engine heat disappears.

Henry Smith Physics for university students (Volume 2)

SECOND LAW OF THERMODYNAMICS
Garnet's Heat Engine
Definition of terms

1. Heat engine.

A heat engine is any mechanical contrivance by means of which heat is converted into work.

Steam engines, gas engines, oil engines, hot-air engines are all forms of heat engines.

All heat engines exhibit the characteristic that heat disappears during the performance of work....

2. Cycle of operations.

In every form of heat engine the transformation of heat into work is effected by subjecting some suitable substance to a cycle of operations (expansion, compression, condensation, etc.), so arranged that the work done by the substance during the cycle is
greater than the work done on it, and useful external work is done at the expense of the heat supplied to the substance.

From the First Law of Thermodynamics the amount of work performed by the gas on external bodies during the cycle must be equal to the heat which has disappeared.

ADVANCED LECTURE NOTES ON HEAT
BY J. R. ECCLES, M.A.

Him determined the mechanical equivalent of heat... Thus the heat
entering the cylinder, as well as that leaving it, was determined. The heat which disappeared was found to be equivalent to the work performed by the engine.

All heat engines exhibit the characteristic that heat disappears during the performance of work. Thus, in Hirn's experiment (p. 283) it was found that during a given time the heat entering the cylinder... was greater than that carried away... the excess being proportional to the work performed by the engine.

The first law of , thermodynamics is a particular application of the more general law of the Conservation of Energy. According to this letter law, the total amount of energy in the universe remains constant, whatever changes may take place in its distribution.

The first law of thermodynamics simply states that... where heat is used up in performing work, the heat which disappears is equivalent to the work performed.

HEAT FOR ADVANCED STUDENTS BY EDWIN EDSER

when heat does work in an engine, a portion of the heat disappears.

James Clerk Maxwell. Theory of heat

compressed air expanding against air pressure cools down; this does not take place if the air expands in a vacuum. In the first case the compressed air has to exert a mechanical force to overcome the resistance of the air pressure and in the second case it does not. Thus in the first case the heat which has disappeared can be equated to the work done and thus a mechanical equivalent can be found,..

Conservation and Innovation : Helmholtz's Struggle with Energy Problems and the Birth of Theoretical Physics

This law states in effect that we cannot get energy for nothing. Whenever we get work from heat, a definite quantity of heat disappears...

Cyclopedia Of Engineering

[Longboy]

For an engine not under load has no reason to display its greater torque cappacities.

So is this your explanation ? Thats an observation you can't contradict.

Longboy wrote:
In models this transition time from first revolutions to full capacitys is a matter of seconds.


And, so... This proves what?


Quote:
In a workhorse low torque Stirling these operating instructions provide for that shortcoming and state the neccesity of gradually feeding in the load. The flywheel may not have the momentum to carry it over till the heat energy is at opperational minimums. There is not much of a reserve and it takes several minutes to bring these industrial size Stirlings up to their opperational temperatures. They do not rival a typical lawnmower engine but their versatility of many fuel sources to provide its heat input is its ace in the hole.


Again, what's your point?......That Stirling has some very well known inadaquacys and if the VITA workhorse could come to life as fast as a model that would be more desireable and comparable to a gas engine.

If the rpm is the same under load, then someone must have stepped on the accelerator.
Yes, If you increase the load you increase the throttle to maintain the rpm.
A Stirling running on a candle has no such mechanism. The energy/heat input on a Stirling is not generally variable. It doesn't have a gas peddle.

Candles running a model Stirling? Haven't seen many using candles. Modelers use the "totally adjustable heat input device". Someday you will know of this device. Doen't matter , you still increase the heat to maintain the load increase or you may lose the rpm to below its operational parameters and engine stalls. That IS an observation. I have no trouble raising or lowering the heat input in my models. You missed that in your VITA engine where the instructions say the fuel auger is "hand opperated". Don't you know what that means?

You keep making this comparison. Stepping on the gas to get up hill etc. in an internal combustion engine. It does not apply to the situation I'm describing with a Stirling where the heat/energy input is constant but the work load is variable.

...That would be because this situation you decribe does not happen. You made a change in the constants by introducing a variable and the engine will react to that change. Thats why we are in dissagreement here. My comparisions deal with your theory of more work done, more torque produced with a constant heat input. Again that can't happen, you can't get something for nothing here! That is proven with the car comparison. If you don't increase the throttle you will not get up that hill. It requires more work to be done to get to the top but like your theory it stays at the bottom! Work doesn't care what type engine is involved. And since we are talking work the comparisons support my conclussions because they all suround the fact of if you need more work done you have to increase the effort (heat input) to achieve that goal. You have yet to bring in any comparisions, examples, analogy, or parrallel to this phenominum you ascribe to Stirling!

Again, I'm referring to a situation where the heat input is constant.
.I got it, but then you have to understand the load has to be constant. You are in that equalibrium then. There is nothing then to change the temp differential.
You can't just manufacture heat out of thin air to bring about a balance. .....Then you don't read your own words! You just said in the previous line that you are "refering to a situation where the heat input is constant". If you haven't got it right , how can I interpret your meaning here??? The extra heat to pull the load has to come from somewhere, but not the heat source as that is not variable. It has to come from the excess waste heat, if there is any. If the engine has been running with no load, there surely would be waste heat.There is no EXTRA heat to pull the load......Its whatever is required to pull the load and in balance with the power requirements to pull such load.

You're missing my reasons in my comparason with other engine types. I understand you are saying your example has a constant heat input level Tom. But the load has to be constant as well to keep the engine running and continue doing work and a Stirling engine is no different here than a I/C engine. That would be its balance. Make a change in any one of these factors: heat input or load and the balance changes. The obsevation made is 1) less heat input, engine falls below opperating rpm's and stalls. Feed it more heat (throttle in car engine, another log under Stirling displacer tube) and it goes into balance again. 2) load decreased, engine run at higher RPM's. Feed in more load, rpm drops to opperational zone, balance achieved.

Quote:
this equalibrium would not change the heat differential


I think it would.

A portion of the heat that was previously just running through the engine and going to waste and winding up at the heat sink, under a load, would be redirected to do work and the heat would "disappear" never reaching the heat sink.

If the heat no longer exists, if the heat is gone, if the heat has disappeared, if it is no longer going to waste and just running straight to the heat sink, increasing the temperature of the heat sink, and the heat input remains constant, then the engine would have to run cooler and more efficiently.
You are having all kinds of problems putting the Stirling dynamics together here Tom. The heat that disapperes is totally different from the waste heat. You just said here that the "disappeared heat NEVER reaches the heat sink"! So how could it possibly be......"REDIRECTED"???
How could it run hotter if the heat has disappeared and no additional heat has been added ?

Again your lack of understanding Stirling here! No additional heat has been added??? But you keep on telling me we have a "constant heat input" here. Exactly how do you come to these conclusions when you ,yourself, tear them apart here? All the heat is supplied by the burner under the displacer cyl. to do the work. There is no waste heat recycled to help drive the load. Heat being removed from the engine is outside of the sealed air in the engine. It can't get back in to do any work.

I would say a small portion of a Stirlings heat energy is used up (disapeared) working a load. The majority of Stirling heat is disappated to the atmophere. Change any of the constants, you changed the equalibrium, that will change the temp differential but driving a constant load with constant heat input means differential also is constant. Engine is within opperational parameters.

That VITA reference I quoted does not say anything about stoking the fire to get more work out of the engine. It says nothing about increasing the heat input in any way. It says apply a load and the engine will "grow stronger" automatically. Unbelievable! I wouldn't have you change a light bulb. You continue to prove my point that you don't understand the Vita instructions here. You don't get what a "hand opperated auger" is!

The only way to increase the power in a Stirling is by increasing the temperature differential.

If applying a load makes the engine "grow stronger", the logical conclusion is that the temperature differential has increased upon applying a load.

..thats fine, constant heat input and letting the engine rise to its opperating temperature! But you have it backwards! The load is a user of heat. Your temp differntial just DECREASED! What they are tell you is the VITA engine can start with a load now cause it is warming up to the point of accepting more load. Again it is rising to its maximum capacitys. You read the instructions incorrectly or at least interpret what they are telling you. Its the other way around Tom. You apply the load after the engine grows stronger to carry the load. Not put on a load so the engine gets stronger. I didn't see anything in the Vita instructions about feeding a load so the engine can get stronger.

VITA: The load
can be increased as the engine grows stronger

.........the operating word here is "AS"! Does not say as you do, " add a load to make the engine stronger". That doen't make sense! You just showed me that you have shortfalls in understanding mechanics.

1. Heat engine.

A heat engine is any mechanical contrivance by means of which heat is converted into work.

......This is your quote that supports my use of the I/C engine for comparison here.

When work is transformed into heat or heat into work,
the 'quantity of work is dynamically equivalent to the
quantity of heat.

.........This is your quote that supports my use of balance and equalibrium in Stirling function.

All heat engines exhibit the characteristic that heat disappears during the performance of work. Thus, in Hirn's experiment (p. 283) it was found that during a given time the heat entering the cylinder... was greater than that carried away... the excess being proportional to the work performed by the engine.

...This is your quote that refutes your conclussion that Stirling heat is redirected to drive the load.

If applying a load makes the engine "grow stronger", the logical conclusion is that the temperature differential has increased upon applying a load.

Congrates Tom! Now even you know why your theory is in the trash! A Stirling driving a load runs cooler I believe you said.

[Tom Booth]

Longboy,

I don't know if you enjoy arguing just for arguments sake or what, but how many times do you need to be proven flat wrong ?

For an engine not under load has no reason to display its greater torque cappacities.

So is this your explanation ? Thats an observation you can't contradict.

You are basically agreeing with me here I think. Under a load the engine has more torque. I've provided a logical explanation for this based on thermodynamic principles.

You seem to have some sort of ax to grind. Going to ridiculous lengths just to disagree or try to prove me wrong.

Tom says: "Expanding gas pushes against the piston"

Longboy says: "no way!"

Tom provides half a dozen references that state explicitly "Expanding gas pushes against the piston". in the exact same context using the same words with the exact same meaning.

Longboy says: "I agree with the references but you are still wrong" though the references state exactly the same thing using exactly the same wording, including the outlawed "against" word, though this is a perfectly common and easily understood word.

The painter leaned his ladder against the house. The cat rubbed up against her leg. The doctor placed his stethoscope against the patients chest. The policeman told the robber to put his hands against the wall.

I'm getting just a little tired of your inane nit picking and circular arguments that go nowhere, make no sense or are just plain misinformation that flies in the face of everything ever written about these engines in the past 100 years of more.

Now I say that a Stirling increases in torque when under a load.

Again, you try to prove me wrong by AGREEING with the observation and the references but saying that the reason is: "For an engine not under load has no reason to display its greater torque capacities".

What is that supposed to mean ?

The engine has some reasoning faculty ?

You claim the engine doesn't increase in torque because the heat is converted into work to power the load, increasing the temperature differential, but because it doesn't want to cooperate without having a reason ?

Again, you can't prove my conclusions wrong by agreeing with them and then giving some ridiculous alternative "explanation" that explains nothing.

But hay, if you want to think the engine has some decision making capability, if that works for you, its OK by me. The results are the same. Apply a load. The engine "displays its greater torque capacities".

Longboy wrote:... Stirling has some very well known inadaquacys and if the VITA workhorse could come to life as fast as a model that would be more desireable and comparable to a gas engine.

Neither a small nor a big Stirling is comparable to a gas engine. A gas engine is not powered by a temperature differential. As far as "inadequacies" That VITA engine puts out 5 Kw. (5000 watts) quite adequate for the application IMO considering it is little more than an over-sized tin can engine.

If the rpm is the same under load, then someone must have stepped on the accelerator.
Yes, If you increase the load you increase the throttle to maintain the rpm.

Obviously, though you neglected to mention it, stating that the heat increases due to the load rather than burning more fuel.

Candles running a model Stirling? Haven't seen many using candles. Modelers use the "totally adjustable heat input device". Someday you will know of this device. Doesn't matter

Again, are you making an argument just for arguments sake ?

Typically, Stirling engines, model or otherwise, use a constant heat source. Very frequently just a candle. If you claim you haven't seen many I'd say you are being disingenuous.

You missed that in your VITA engine where the instructions say the fuel auger is "hand opperated". Don't you know what that means?...

Unbelievable! I wouldn't have you change a light bulb. You continue to prove my point that you don't understand the Vita instructions here. You don't get what a "hand opperated auger" is!

Like I said, I'm growing weary of trying to correct your unfounded arguments. You go on and on wasting time, spouting misinformation and making nonsensical arguments. Try actually reading the reference:

The air pump as well as all other accessories needing power are driven directly from the rotating engine shaft.

Other accessories requiring shaft power. are the auger feeding the fuel, the combustion air blower, and the cooling water pump and radiator fan.. With these accessories, the engine is able to work without any other source of power, and needs only fuel to operate.

Typical operating instructions are as follows:

1. Make sure the engine is in good operating condition and
the hopper is full of fuel.

2. Start a fire in the burner with kindling (e.g., wood shavings,
dried leaves), and operate the air blower by hand
until the interior of the burner is sufficiently hot to
receive and ignite the fuel from the fuel feed.

3. Hand operate the combustion air blower and the fuel auger
until the heater head of the engine reaches a moderate
temperature (about 300[degrees]C). The engine is now ready to
start.

Naturally you have to feed the fuel by operating the fuel auger by hand BEFORE THE ENGINE STARTS! Not after the engine is running.

VITA: The load can be increased as the engine grows stronger

.........the operating word here is "AS"! Does not say as you do, " add a load to make the engine stronger". That doesn't make sense!

Maybe to you it doesn't.

There is a correlation between increasing the load and the engine "growing stronger". Just as there is a correlation between removing the load and the power output "dropping to zero". Or removing the load and the engine speeding up and overheating.

The load can be increased as the engine grows stronger. This happens automatically if the engine is attached to loads such
as centrifugal water pumps or generators

The illustration shows, and the text states (above) that the load is attached to the engine from the start, unless it is a heavy variable load such as saws and milling machines in which case the load must be applied gradually.

Clearly, if the load must be applied gradually so as to give the engine time to "grow stronger" then this "growing stronger" does not happen except with the application of the load.

1. Heat engine.

A heat engine is any mechanical contrivance by means of which heat is converted into work.

......This is your quote that supports my use of the I/C engine for comparison here.

All of your comparisons involve increasing the fuel intake and therefore increasing the heat input. As you have already admitted: "Yes, If you increase the load you increase the throttle to maintain the rpm"

If you put your car in neutral and rev up the engine with no load, I'm quite certain it would also tend to overheat rather quickly.

When work is transformed into heat or heat into work, the 'quantity of work is dynamically equivalent to the
quantity of heat.

.........This is your quote that supports my use of balance and equalibrium in Stirling function.

It states, in context, that heat is transformed into work and the heat disappears. This does not support your assertion that a load added to an engine that was being run without a load would result in hotter operating temperatures.

All heat engines exhibit the characteristic that heat disappears during the performance of work. Thus, in Hirn's experiment (p. 283) it was found that during a given time the heat entering the cylinder... was greater than that carried away... the excess being proportional to the work performed by the engine.

...This is your quote that refutes your conclussion that Stirling heat is redirected to drive the load.

It doesn't refute what I said at all. Heat IN > Less Heat out.

You are confused by the word "excess". apparently. But it is quite apparent that the "excess" referred to here is the difference between the higher heat input and the lower heat output. The "excess" having been converted into work.

If applying a load makes the engine "grow stronger", the logical conclusion is that the temperature differential has increased upon applying a load.

Congrates Tom! Now even you know why your theory is in the trash! A Stirling driving a load runs cooler I believe you said.

Right. A Stirling driving a load runs cooler.

You seem easily confused by words.

I stated that "the temperature differential" increases. I did not say that the heat increases.

There is a big difference.

The temperature differential increases due to the LOWER temperature at the heat sink. The temperature at the heat source remains constant. The average temperature is lower.

Under load, doing work, the heat is converted into work and disappears, never reaching the heat sink. The average operating temperature is lower. More heat is converted into work so less heat needs to be dissipated at the heat sink.

Without doing work, the heat is not converted into work, more heat reaches the heat sink raising the temperature of the heat sink. The heat input is constant. The average operating temperature increases.

There is no contradiction in saying that the temperature differential increases but the overall operating temperature decreases.

[Tom Booth]

You have yet to bring in any comparisions, examples, analogy, or parrallel to this phenominum you ascribe to Stirling!

I don't know as there is any better analogy than that already given in the previous reference:

In any kind of heat-engine the heat is let down, within the engine, from a high level of temperature to a lower level of temperature, and it is by so letting heat down that the engine is able to do work, as a water-wheel is able to do work by letting water down from a high level to a lower level. But there is this important difference, that some of the heat disappears in the process of being let down: it is converted into the work which the engine does.

Sticking with this general analogy, lets make it a little more applicable to a Stirling engine specifically.

Imagine a water wheel powered by a flow of water into a tank. The power wheel itself is floating on the water in the tank. The water level in the take can be equated to the temperature differential.

The lower the water level, the farther the water has to fall, the more power to the power wheel.

Now you have to keep in mind what was stated above: "there is this important difference, some of the heat disappears in the process of being let down: it is converted into the work"

It is difficult to imagine the water powering a water wheel just "disappearing" but if this analogy is applied to a Stirling, that is what happens.

Now imagine a siphon that draws water out of the tank at the same rate (or more realistically, a slightly slower rate) than water is being let down into the tank to power the wheel.

If when under a load, some of the "water" powering the water wheel just "disappears" then less water will be spilling off the water wheel entering the tank but the siphon will continue to draw off water at the same rate. The water level will gradually drop. The water will now have to fall further to reach the power wheel. The energy delivered to the wheel will therefore increase.

If the load is removed, the water entering the tank will no longer "disappear". The water level in the tank will gradually increase. The water will not have as far to fall to reach the power wheel. Since the water is not falling as far, less energy will be delivered to the wheel.

Add back the load and again, the incoming water "disappears" and the water level drops. Power to the wheel increases.

I'm not going to go to all the trouble of animating this. You will have to use your imagination, but here is the setup as I've described.

The water level in the tank can be equated to the temperature differential in a Stirling. The Stirling power output depends on the temperature differential in much the same way that this water wheel power output depends on the water level in the tank.

http://prc_projects.tripod.com/stirling_load_illustration.html

The inlet pipe is the heat input. The siphon is the heat sink. The water is the heat itself. The water level is the temperature differential.

I don't know how I could make this any clearer.

[Longboy]

I don't know if you enjoy arguing just for arguments sake or what, but how many times do you need to be proven flat wrong

.......once would be fine. When exactly are you going to start? I think it would nice of you to start with that VITA engine. The one that has a fuel auger on an engine you say does nothing about increasing the heat input in any way. Or you might wanna try how to get something outta nothing by adding a load with the same heat input makes an engine stronger. But this time try to remember the phraze " AS the engine gets stronger". Maby you would like to throw in another one of YOUR QUOTES:

SECOND LAW OF THERMODYNAMICS
Garnet's Heat Engine
Definition of terms

1. Heat engine.

A heat engine is any mechanical contrivance by means of which heat is converted into work.

Steam engines, gas engines, oil engines, hot-air engines are all forms of heat engines.

[/quote]......and start explaining why the car going up the hill is not a valid comparison. Also please tell the audience why you would back me up with your quotes as you burried yourself with same. I really don't need your help here! Any day now before I need another haircut!

[Longboy]

Obviously, though you neglected to mention it, stating that the heat increases due to the load rather than burning more fuel.

Show me in thermo law that heat doen't increase by burning more fuel then. The load is a USER of heat. It doen't contribute to an INCREASE in heat.

Again, are you making an argument just for arguments sake ?

Typically, Stirling engines, model or otherwise, use a constant heat source. Very frequently just a candle. If you claim you haven't seen many I'd say you are being disingenuous.

This goes right to your lack of obsevation. I want you to go to "You Tube" and let me know how many Stirlings have a candle for heat supply vs those that use the "totally adjustable heat input device". Everyone else reading here is going to and quickly find out and see that not only do you not read what you write, but you don't have any credibility here also by making statements that aren't so.

Like I said, I'm growing weary of trying to correct your unfounded arguments. You go on and on wasting time, spouting misinformation and making nonsensical arguments. Try actually reading the reference:

...I would grow weary if I was you too Tom! But actually I would rather hear what you know about what a fuel auger does. You like to read but just don't comprehend. That would be because you said:

That VITA reference I quoted does not say anything about stoking the fire to get more work out of the engine. It says nothing about increasing the heat input in any way.

This is just telling everyone here that for Tom, if it isn't written down in the instructions, if it doesn't say anything about stoking then it isn't so! Don't talk about mechanical things here Tom your not qualified.

Naturally you have to feed the fuel by operating the fuel auger by hand BEFORE THE ENGINE STARTS! Not after the engine is running.

I think you mis spoke here Tom. Are you saying once the engine is running you no longer feed it fuel?

Quote:
VITA: The load can be increased as the engine grows stronger
.........the operating word here is "AS"! Does not say as you do, " add a load to make the engine stronger". That doesn't make sense!


Maybe to you it doesn't.....Me and the rest of the world understand "cart before the horse"!

There is a correlation between increasing the load and the engine "growing stronger". Just as there is a correlation between removing the load and the power output "dropping to zero". Perhaps you understand "an engine not under load has no reason to display its greater torque" correlation now.Or removing the load and the engine speeding up and overheating.

Yes I agree and explained this correlation in terms of balances. If we have constant heat input and remove the load the engine speeds up. Where I disagree with you here is the engine overheating. That would be only a "maby". For in a good design the radiator should carry away that heat under increasing heat input, constant heat input, running with load, or speeded up by removing load.

The illustration shows, and the text states (above) that the load is attached to the engine.... You have to pay attention here, better read that again Tom! Does not say load "IS" already attached. It says "IF" the load is attached"......from the start, unless it is a heavy variable load such as saws and milling machines in which case the load must be applied gradually. You can start up the VITA engine without any load whatsoever.

Clearly, if the load must be applied gradually so as to give the engine time to "grow stronger" then this "growing stronger" does not happen except with the application of the load.

.......We agree but possibbly only on a time line of events here. If the manual has grow stronger in quote marks thats just telling me they're talking down to the peasant running the machine. What kind of a millwright would use that term grow stronger? The engine accepts a greater load because it has warmed up to its opperational zone. It is now in its opperational zone irregardless of the greater load now fed upon it. The engine needs time to warm up. The formula is Torque over Time = Horsepower.

Quote:
In a workhorse low torque Stirling these operating instructions provide for that shortcoming and state the neccesity of gradually feeding in the load. The flywheel may not have the momentum to carry it over till the heat energy is at opperational minimums. There is not much of a reserve and it takes several minutes to bring these industrial size Stirlings up to their opperational temperatures

I think I can interpret your statement so on this issue we are close.

All of your comparisons involve increasing the fuel intake and therefore increasing the heat input. As you have already admitted: "Yes, If you increase the load you increase the throttle to maintain the rpm"

If you put your car in neutral and rev up the engine with no load, I'm quite certain it would also tend to overheat rather quickly.

That is true to get the balance. This addressed your constant heat input with an increase in load. Now we lost the balance, something changed and the engine will react. I agree with your car analogy here. Take the load off and it will rev. But like in the Stirling example a good design and higher than needed radiator capacity keeps the overheating to "maby" status.

Quote:
When work is transformed into heat or heat into work, the 'quantity of work is dynamically equivalent to the
quantity of heat.

.........This is your quote that supports my use of balance and equalibrium in Stirling function.


It states, in context, that heat is transformed into work and the heat disappears. This does not support your assertion that a load added to an engine that was being run without a load would result in hotter operating temperatures.

This sounds more like your theory of an engine driving a load running cooler interpreted by you in a disagreement that I say it runs hotter. You're going to have to make the quote back to me on this.

It doesn't refute what I said at all. Heat IN > Less Heat out.

You are confused by the word "excess". apparently. But it is quite apparent that the "excess" referred to here is the difference between the higher heat input and the lower heat output. The "excess" having been converted into work.

We just disagree on words used here. I understand your meaning with that explaination.

Right. A Stirling driving a load runs cooler.

You seem easily confused by words.

I stated that "the temperature differential" increases. I did not say that the heat increases.
I say no heat increase, no load driven, no cooler running. Takes more heat input to drive a load. Thats a given in Thermo law. Once that heat input is sufficiant to pull the load we have the balance. With a balance there is no change in temp diff.
There is a big difference.

The temperature differential increases due to the LOWER temperature at the heat sink. The temperature at the heat source remains constant. The average temperature is lower.
You explain your reasoning well here. But til you explain using thermo law how you can drive an increase load with a constant heat input it won't fit into your theory!
Under load, doing work, the heat is converted into work and disappears, never reaching the heat sink. The average operating temperature is lower. More heat is converted into work so less heat needs to be dissipated at the heat sink.

Without doing work, the heat is not converted into work, more heat reaches the heat sink raising the temperature of the heat sink. The heat input is constant. The average operating temperature increases.Very little of the source heat is converted to work and the majority of heat is lost to the atmosphere thru the radiator.

There is no contradiction in saying that the temperature differential increases but the overall operating temperature decreases.

I know its hard to find references that tell us under what conditions would the heat differential change in Stirling. Is it just theory? Is there some instrumented test out there showing such in these engines? We are stalled now. If you can find examples or conditions showing where the heat differential changes bring them forward. They may not be there at all.

[Tom Booth]

I don't know if you enjoy arguing just for arguments sake or what, but how many times do you need to be proven flat wrong

.......once would be fine.

Your words: "The air does not work against a power piston"; "I know the heated air does not push, pull with or against the piston"; "the expanding gasses DO NOT push the piston at all"

Wrong, wrong, wrong,... and you seem to have already admitted you were wrong: quote: "(and I see my word "push" here so you got me)!"

Your words: "....All these refs, with illustrations or animated engines next to the text, talk about the ALPHA Stirling. And since this is not the engine you refer to you can't use it to make your case."

Wrong. The references were about the Stirling Cycle and apply to ALL Stirling engines.

Your words: "This is a sticking point with you that I already addressed being related to your repeated use of "against". Time to drop it!"

Wrong, as per your previous admission: "(and I see my word "push" here so you got me)!"

You know you were wrong but just can't admit it. Instead you waste time with your denials trying to sidestep the issue.

Your posts are full of contradictions.

In your first post you state: "An overheated Stirling will stall, there is no longer a sufficient heat differential to move the mechanism."

A few posts later you assert: "........I'm sorry you haven't made any engines, but any build up of heat is not detrimental to a running model."

A few posts later: ".....Well you pick something up from my posts about how overheating looses the temp differential. And I would find many in agreement. For they know an overheated engine will not run but they see I was talking about a running engine where this heat build up is not an issue..........why didn't you see that? The heat builds up but the engine does not stall. Why doesn't the engine stall Tom??? "

So you go from: "An overheated Stirling will stall, there is no longer a sufficient heat differential to move the mechanism." to "The heat builds up but the engine does not stall."

This is just typical.

You have repeatedly contradicted yourself, just to adopt an opposing viewpoint for the sake of argument, with no consistency whatsoever.

Now you very forcefully and rather abusively make the assertion: "Unbelievable! I wouldn't have you change a light bulb. You continue to prove my point that you don't understand the Vita instructions here. You don't get what a "hand operated auger" is!"

Wrong. The auger is not a "hand operated auger". Again you know you were wrong but just won't admit it. Instead you go on and on trying to make an argument.

Now again you are nit picking over simple words: "...the operating word here is "AS"!".

That's exactly right "AS". Not before or after but together. One dependent upon the other.

AS I ran the garden hose the barrel filled up with water. AS it rained, the puddle got deeper. AS the water boiled, the steam rose from the pot. AS the wind blew the leaves fell. AS the storm got worse the snow got deeper.

"The load can be increased as the engine grows stronger"

Not wait till the engine gets stronger then apply the load, but simultaneously, AS the load is applied the engine increases in torque, AS the engine increases in torque, the load can be increased. However you say it, there is clearly a dependence or correlation there.

When exactly are you going to start? I think it would nice of you to start with that VITA engine. The one that has a fuel auger on an engine you say does nothing about increasing the heat input in any way.

Obviously, the auger feeds the fuel in at a steady rate once the engine is running: "Once the engine is up to full power and doing its work, the operator needs only to keep the fuel hopper full"

Your assertion that the auger is "hand operated" is wrong.

But lets just say that that reference is open to some interpretation.

The other references I've provided should clear up the matter. Most notably:

...Much greater efficiency can be obtained by using a fluid for working substance and by making it act so that its own expansion of volume not only does work but also causes it to fall in temperature before it begins to reject heat to the cold receiver.

Thermodynamics for engineers By Sir James Alfred Ewing

I don't think that this is open to interpretation. "its own expansion of volume not only does work but also causes it to fall in temperature" resulting in "greater efficiency".

Then there is the equation:

Heat taken in = Heat rejected + Work done by the substance.

Clearly, from that equation, if the gas does more work less heat is rejected. If the gas does less work, more heat is rejected.

Lets put some real numbers into that equation just to make this clear:

Heat taken in = 100 units.

Heat rejected + the heat transformed into work must also equal 100 units.

If heat transformed into work is less (say 10 units), heat rejected is more (90 units). If the heat that "disappears" by being transformed into work is more (say 35 units) then heat rejected to the cold sink is less (65 units).

100 = 10 + 90
100 = 35 + 65

If there is no load on the engine, then heat transformed into work is zero. Therefore 100% of the heat must be rejected to the heat sink.

100 = 0 + 100.

If there is a load on the engine, then some of the heat is transformed into work and less heat is rejected to the heat sink:

100(heat in) = 35(work performed) + 65(heat out)

......and start explaining why the car going up the hill is not a valid comparison.

Mostly because in an internal combustion engine the power (heat and pressure) are generated internally. The temperature of the exhaust gases have no bearing on the functioning or the power output of the engine. An internal combustion engine is not powered by a temperature differential.

In a Stirling, on the other hand, the amount of heat rejected to the heat sink does effect the temperature differential.

You more or less admit this when you said earlier: "I agree with your car analogy here. Take the load off and it will rev. But like in the Stirling example a good design and higher than needed radiator capacity keeps the overheating to "maybe" status."

Most small Stirling engines do not have a radiator with water circulating through it like a car engine. Rev a car engine and the water pump also runs faster as it is driven by the engine. Typically, a Stirling engine has a heat sink with a limited capacity for dissipating heat.

Again, you agree, more heat needs to be dissipated with no load.

Turning around and saying yeah, but, you can just put an over-sized radiator on it - doesn't alter the fact that more heat needs to be dissipated in a no-load condition.

[Tom Booth]

Obviously, though you neglected to mention it, stating that the heat increases due to the load rather than burning more fuel.

Show me in thermo law that heat doen't increase by burning more fuel then.

Can't you keep anything straight ?

Typically, Stirling engines, model or otherwise, use a constant heat source. Very frequently just a candle. If you claim you haven't seen many I'd say you are being disingenuous.

This goes right to your lack of observation. I want you to go to "You Tube" and let me know how many Stirlings have a candle for heat supply vs those that use the "totally adjustable heat input device". Everyone else reading here is going to and quickly find out and see that not only do you not read what you write, but you don't have any credibility here also by making statements that aren't so.

LOL...

Quote:
In a workhorse low torque Stirling these operating instructions provide for that shortcoming and state the neccesity of gradually feeding in the load. The flywheel may not have the momentum to carry it over till the heat energy is at opperational minimums. There is not much of a reserve and it takes several minutes to bring these industrial size Stirlings up to their opperational temperatures

I think I can interpret your statement so on this issue we are close.

You are quoting yourself here. LOL...

I know its hard to find references that tell us under what conditions would the heat differential change in Stirling. Is it just theory? Is there some instrumented test out there showing such in these engines? We are stalled now. If you can find examples or conditions showing where the heat differential changes bring them forward. They may not be there at all.

I've made my case.

As I've already mentioned, this is an Aspect of Stirling engines that does not seem to have been widely recognized or investigated, which is why I've brought the issue here in the hope that someone else might have made some observations or conducted some experiments in this area.

Many of my references in support of "my theory" are very old. Some from the 1800's when these engines were more widely used and their theory of operation was better understood. Otherwise it is based on fundamental thermodynamic concepts and a few anecdotal accounts, such as the VITA engine operating instructions and the Solar Stirling patent.

But I think this is more than just "my theory".

I've seen many studies of Stirling engines being tested for their efficiency "under no-load conditions".

I think such testing does not apply to a Stirling engine and the conclusions reached from such tests would be misleading.

If the load on a Stirling engine has a direct effect upon the temperature differential then the efficiency of the engine could not be determined under no-load conditions.

These engines were once used for power production, and that, constructed out of materials with inferior heat conduction capacity.

I think that the idea that these engines are inherently inefficient, have no torque or any real practical power output is sheer nonsense that has apparently resulted from a lack of understanding about how these engines actually operate.

They run on a temperature differential. That temperature differential cannot be maintained without a load on the engine. These engines are designed for the purpose of converting pure heat into work. If there is no load on the engine then no heat is converted into work and the temperature differential is quickly lost giving a false impression that no real power output is possible.

I think when talking about Stirling engines and their potential power output, the saying applies: "Use it or loose it".

If you run a Stirling for any length of time without giving it some actual work to do then its capacity to do work is quickly lost due to a build up of heat which diminishes the temperature differential.

On the other hand, give it some work to do and the excess heat is converted into work, the temperature differential gradually increases and the potential power output gradually increases.

I've made my case.

If you have some actual evidence to refute this, fine. But making ridiculous assertions like the one above (and below), apparently just to be argumentative is a waste of time:

This goes right to your lack of observation. I want you to go to "You Tube" and let me know how many Stirlings have a candle for heat supply vs those that use the "totally adjustable heat input device". Everyone else reading here is going to and quickly find out and see that not only do you not read what you write, but you don't have any credibility here also by making statements that aren't so.

No need to go to You Tube. I can't imagine anyone hear not having already seen a Stirling engine running on a candle. Probably their own. What universe do you live in ?

[Longboy]

Your posts are full of contradictions.Your attempt at equating certain words as synonyms has not worked. Overheat = heating up? The following have all been addressed with no contradiction

In your first post you state: "An overheated Stirling will stall, there is no longer a sufficient heat differential to move the mechanism."

A few posts later you assert: "........I'm sorry you haven't made any engines, but any build up of heat is not detrimental to a running model." You equate a build up of heat as meaning the same as overheated, I do not! For an overheated engine doesn't run. Your VITA engine heat builds up and it runs.

A few posts later: ".....Well you pick something up from my posts about how overheating looses the temp differential. And I would find many in agreement. For they know an overheated engine will not run but they see I was talking about a running engine where this heat build up is not an issue..........why didn't you see that? The heat builds up but the engine does not stall. Why doesn't the engine stall Tom??? " do you have an answer here???
Some more questions you avoid.
So you go from: "An overheated Stirling will stall, there is no longer a sufficient heat differential to move the mechanism." to "The heat builds up but the engine does not stall."
No contradiction here either. You just don't get the concept of overheating stalls an engine verses heat building up in your VITA does not stall. A running engine is not in an overheated condition. If this is not true explain it then. Or you can avoid it like your track record of no response.

You have repeatedly contradicted yourself, just to adopt an opposing viewpoint for the sake of argument, with no consistency whatsoever.I've been consistent in proding you for answers as you have been by running away from questions.

Now you very forcefully and rather abusively make the assertion: "Unbelievable! I wouldn't have you change a light bulb. You continue to prove my point that you don't understand the Vita instructions here. You don't get what a "hand operated auger" is!"If this bothers you so much maby you'll understand what about you bothers me. And thats avoiding You Tube, blowing off Stirling cycle and just not answering questions!

Wrong. The auger is not a "hand operated auger". Then instead of telling me what it isn't, define what kind of an auger it is then Tom. Again you know you were wrong but just won't admit it. I don't have to cuzz you never answered the auger question, never gave your position for me to reconsider. Instead you go on and on trying to make an argument. Thats what its about here, making the argument. Thats how one supports his position other wise you are just blowing smoke. Then I'll assume you can't make the argument by not answering the question. I asked you 3 times about this auger and you haven't answered. I don't think it to much to ask for your position on this auger thing. I asked you to go to You Tube and you refuse. Time to bring in more of Tom and less of quotes by others cuzz you sound like an encyclopedia! Its not enough to quote out of books and following with 10 words of your own saying "thats the way it is". Where is the passion in that? It comes across to me as something I find contemptable and that you are no where near on par in these posts.

Now again you are nit picking over simple words: "...the operating word here is "AS"!". Its not a nit pick as you and I go to war over certain words. words used are important to get an idea across. overheat does not mean the same as heating up to me but you call it a contradiction!

That's exactly right "AS". Not before or after but together. One dependent upon the other.

Now you made the argument and supported your use of "as". Now I understand you and it ok to disagree on things here. The understanding is more the point!

"The load can be increased as the engine grows stronger"

Not wait till the engine gets stronger then apply the load, but simultaneously, AS the load is applied the engine increases in torque, AS the engine increases in torque, the load can be increased. However you say it, there is clearly a dependence or correlation there.

Thanks Tom, this is one rare response after all my proding and sarcasim to get answers from you. I understand and agree here. At least the cart and horse are side by side now!

Obviously, the auger feeds the fuel in at a steady rate once the engine is running: "Once the engine is up to full power and doing its work, the operator needs only to keep the fuel hopper full"

Your assertion that the auger is "hand operated" is wrong.

But lets just say that that reference is open to some interpretation.

Again thanks here too. Well if this auger is not manually (hand) opperated. Would you agree that the opperator controls the feed, can adjust the feed to meet operating conditions but the auger is powered by the engine?

Then there is the equation:


Quote:
Heat taken in = Heat rejected + Work done by the substance.



Clearly, from that equation, if the gas does more work less heat is rejected. If the gas does less work, more heat is rejected.

Lets put some real numbers into that equation just to make this clear:

Heat taken in = 100 units.

Heat rejected + the heat transformed into work must also equal 100 units.

If heat transformed into work is less (say 10 units), heat rejected is more (90 units). If the heat that "disappears" by being transformed into work is more (say 35 units) then heat rejected to the cold sink is less (65 units).

100 = 10 + 90
100 = 35 + 65

If there is no load on the engine, then heat transformed into work is zero. Therefore 100% of the heat must be rejected to the heat sink.

100 = 0 + 100.

If there is a load on the engine, then some of the heat is transformed into work and less heat is rejected to the heat sink:

100(heat in) = 35(work performed) + 65(heat out)

.........I agree and explained that the majority of the heat in the engine is lost to the atmosphere and a smaller amount of its heat is used up to do work.

[Longboy]

Longboy wrote:
Quote:
Obviously, though you neglected to mention it, stating that the heat increases due to the load rather than burning more fuel.

Show me in thermo law that heat doen't increase by burning more fuel then.


Can't you keep anything straight ?

its not an oversight, I don't agree heat increases because of the load.

Quote:
Quote:
In a workhorse low torque Stirling these operating instructions provide for that shortcoming and state the neccesity of gradually feeding in the load. The flywheel may not have the momentum to carry it over till the heat energy is at opperational minimums. There is not much of a reserve and it takes several minutes to bring these industrial size Stirlings up to their opperational temperatures
I think I can interpret your statement so on this issue we are close.


You are quoting yourself here. LOL...

Ya I know. Just to show we were close on something brought up earlier.

Quote:
I know its hard to find references that tell us under what conditions would the heat differential change in Stirling. Is it just theory? Is there some instrumented test out there showing such in these engines? We are stalled now. If you can find examples or conditions showing where the heat differential changes bring them forward. They may not be there at all.


I've made my case.

As I've already mentioned, this is an Aspect of Stirling engines that does not seem to have been widely recognized or investigated, which is why I've brought the issue here in the hope that someone else might have made some observations or conducted some experiments in this area. Its tough talking and persuading others on these less known subjects!
Many of my references in support of "my theory" are very old. Some from the 1800's when these engines were more widely used and their theory of operation was better understood. Otherwise it is based on fundamental thermodynamic concepts and a few anecdotal accounts, such as the VITA engine operating instructions and the Solar Stirling patent. Perhaps I wasn't the most idea adversary in the discussion here and this forum is not well attended. Only a couple others chimed in.

No need to go to You Tube. I can't imagine anyone hear not having already seen a Stirling engine running on a candle. Probably their own. What universe do you live in ?

Not looking for your imagination here, just to open your eyes up by observation. They don't use candles and you will find that out.

But I think this is more than just "my theory".

I've seen many studies of Stirling engines being tested for their efficiency "under no-load conditions".I haven't looked as deep into Carnot.

I think such testing does not apply to a Stirling engine and the conclusions reached from such tests would be misleading.

If the load on a Stirling engine has a direct effect upon the temperature differential then the efficiency of the engine could not be determined under no-load conditions....I think a test could be done though. Longboys free wheeling engine and Toms loaded engine. Lab testing is very strict so it would be apples to apples. If they both run at same RPM and have constant heat input, you check their opperating temps with an infared thermometer at two different points to establish the temp differential. Some conclussions could be made and we would see if the differential is the same in both or if a change is present between the two engines under these opperating conditions.

These engines were once used for power production, and that, constructed out of materials with inferior heat conduction capacity.Those materials ( cast iron) are time tested, still used today and perform well for their applicational dutys.

I think that the idea that these engines are inherently inefficient, have no torque or any real practical power output is sheer nonsense that has apparently resulted from a lack of understanding about how these engines actually operate.Stirling is old and failed in the marketplace compared to steam engines. There are better powerplants. Nobody goes down to the depot to see the Stirling train! More people use the I/C engine in comparassions because they are everywhere and discount the Stirling.

They run on a temperature differential. That temperature differential cannot be maintained without a load on the engine. These engines are designed for the purpose of converting pure heat into work. If there is no load on the engine then no heat is converted into work and the temperature differential is quickly lost giving a false impression that no real power output is possible.

I think when talking about Stirling engines and their potential power output, the saying applies: "Use it or loose it".

If you run a Stirling for any length of time without giving it some actual work to do then its capacity to do work is quickly lost due to a build up of heat which diminishes the temperature differential.

On the other hand, give it some work to do and the excess heat is converted into work, the temperature differential gradually increases and the potential power output gradually increases.

I've made my case.

If you have some actual evidence to refute this, fine. But making ridiculous assertions like the one above (and below), apparently just to be argumentative is a waste of time:

We can close out the subject then. My experience and observations tell me other things. That Stirlings run fine without any additional load to bare. They don't tend to overheat when running without a load because the waste heat is dispersed at a rate that maintains its opperational zone. This also means the temp differential is satifactory, it is running with no load. There is no build up of heat to the point of overheating and stalling due to design and opperating conditions presented. Model Stirlings can run continuously without a load and do not overheat. Heat input is variable in Stirling. The load does not contribute to increasing temperatures, the load is a net user of heat. Models can but but do not use candles for their heat input!

[Tom Booth]

Mr Longboy or Mr. Green,

I no longer have any interest conversing with you.

Perhaps you took offense due to my opening remark:

If heat is being converted into work then the more work the engine is made to perform the cooler it should run. Maybe the problem with many model Stirling engines overheating is that they are being run without a load of any kind and therefore the heat, rather than being transferred to the load on the engine to do work is just building up and causing the engine to overheat.

In general, I was referring to the various small LTD or "Tin Can" type engines, not those model engines built by knowledgeable and experienced model builders, often quite beautiful of glass and polished brass intended solely for display, meticulously crafted and carefully load balanced so that the limited heat input and large heat sink and cooling fins insure that the engine can be displayed and operated and no overheating takes place.

If I stepped on the toes of any model builders here with this comment, I apologize.

Nevertheless, overheating in MANY (not all) model Stirling engines is a common and well recognized problem. I'll offer a few examples among hundreds if not thousands posted on websites and message boards all over the internet:

How to Build a Stirling Engine

Tips and Warning

* You can use ice and put it on top of the vessel to ensure the Stirling engine mechanism doesn’t overheat.

http://www.buildables.net/how-to-build- ... ngine.html

Boyd's Tin Can Stirling Hot Air Engines
Changes To The Original Plans
Keep That Displacer Piston On!

By adding a "Hook" to the end of the 1/8" rod on the
displacer piston, In the event you "over heat" the engine the displacer piston will not fall off inside the displacer cylinder.
In other words, You won't have to "tear the entire engine apart if a "over heat" happens.

http://www.boydhouse.com/stirling/tips/index.html

How to Build a Stirling Engine

Do not forget to place ice on the top part of the vessel to avoid overheating.

http://www.iqio.org/how-to-build-a-stirling-engine

"Put an ice cube on it" seems to be the most widely recommended solution.

I have NEVER in all of my research and reading about Stirling Engines over the past several years (which has been considerable) seen anyone talking about, suggesting or referring to the facts I've been coming across recently upon researching the thermodynamics of these engines (i.e. increased work output reduces waste heat, heat converted into work "disappears", adding a load to a Stirling engine results in the engine "growing stronger", removing the load from a Stirling Engine causes it to overheat. etc.)

Upon putting together all this new information, It occurred to me that perhaps, as I stated: "Maybe the problem with many model Stirling engines overheating is that they are being run without a load of any kind and therefore the heat, rather than being transferred to the load on the engine to do work is just building up and causing the engine to overheat."

You seem to have taken offense at this statement and jumped in full bore, attacking me, apparently viewing yourself as coming to the defense of model builders everywhere or something. Again, I apologize if there was any misunderstanding, but I did not come here to fight or engage in any heated debate or bar room brawl. I meant no offense towards any model builders and did not mean to suggest that there is anything wrong with, or any inherent "problem" with model Stirling engines intended only for display.

My interest in Stirling engines is primarily utilitarian. I would like to get some power out of a small, not too difficult to build engine for something like charging some batteries for an alternative energy system using an inverter. Or perhaps for transportation, such as a hybrid Stirling-electric vehicle where the steady running Stirling keeps the batteries charged and an electric motor is used for driving and acceleration.

I think that model Stirling engines are great and interesting and nice to have and watch run and all that, but I think it is important for people to understand that the characteristics of a typical model engine, either a sooty tin-can model or an all shinny and beautiful glass and brass model are such that either their heat input is intentionally limited (i.e. glass for example, is more a heat insulator than a heat conductor) or they apparently lack torque and potential for power production, more due to the fact that they are being run in a no-load condition and quickly loosing their temperature differential rather than any inherent incapacity.

Now I don't really wish to continue fighting with you but having said all that, there are some additional comments you have made I feel need to be addressed, just in my own self defense:

You have repeatedly insinuated: "...you don't understand how a Stirling runs."; "...........Well Tom I am truly sorry...............that you still don't know much about these engines! No prize for you."; "What happens in the Stirling cycle Tom?"; ".........I would use that line too if I didn't know the Stirling cycle... If you can't explain what happens in the Stirling cycle I understand."; "I'm trying but had to find out if you have down the Stirling cycle.... Any teacher in school would hand you the paper back and tell you to complete the explanation of the Stirling cycle. Responding with "irrelevant" shows you don't have it."; "I do understand there are those who come to the forum without the Stirling cycle understanding. You have been accommodated here. Others have read this thread and see my prodding and razzing to get from you the Stirling cycle was in vain." etc.

As I've pointed out, and as some of my references state: "The Stirling engine only makes power during the first part of the cycle... In part one of the cycle; the pressure of heated gas pushing against the piston performs work."

If the engine is "running on ice" instead of a heat source, this does not change the equation. The energy to power the engine is still coming primarily from the HEAT being applied to the engine, not the heat sink. Although the role played by the ambient temperature is reversed from that of heat sink to heat source, the energy to push the piston is still coming primarily from the expansion of the heated air working against the piston.

It is during this phase of the cycle that heat is converted into work so that the heat "disappears" and therefore that quantity of heat will never reach the heat sink, which is the concept under examination here in relation to the thermodynamics of the Stirling engine.

I'm not going to cater to your insults and insinuations. I have no need to prove anything to you or anyone else regarding my understanding of the rest of the cycle. The rest of the cycle has little or no relevance in regard to this particular question.

"Heat is added to the gas inside the heated cylinder causing pressure to build. This forces the piston to move down. This is the part of the Stirling cycle that does the work." "its own expansion of volume not only does work but also causes it to fall in temperature"; " if it is made to do work while expanding, the temperature will drop". "if it is allowed to do mechanical work while expanding, it will cool"; "to cool a gas... have it do work... against a piston in an engine"

This only happens during the first phase of the cycle where the heated, expanding gas does work. I see no need to confuse or divert attention away from this by laboring over what happens during the rest of the cycle just to answer your insults and insinuations.

Longboy wrote:

"You just showed me that you have shortfalls in understanding mechanics."; "Don't talk about mechanical things here Tom your not qualified."

You know nothing about me or my qualifications, mechanical or otherwise. But as a matter of fact I've been an engine mechanic most of my life, starting out with my own repair shop in my parents garage in high school. My qualifications have gotten me several jobs working full time as an engine mechanic. Engine mechanics has been my trade a good part of my life. And who are you anyway to dictate who can or can't talk about what here, regardless of their qualifications ? Are you the forum moderator ? Do you own the domain stirlingengineforum.com ?

You come off more like a "Troll" who knows little to nothing about these engines beyond having purchased some models off Ebay.

Given your apparent lack of understanding of basic Stirling engine principles, which you have already confessed early on: (i.e. "How all the containment flows with in the engine I don't know. Temps and pressures change and the engine works.") I don't see how you could have possibly built any working models unless it was from a kit.

Instead you go on and on trying to make an argument.

Thats what its about here,...

No, I don't believe anyone comes here to this forum to pick a fight or engage in senseless debates over irrelevant nonsense.

People either come here to find out about Stirling engines, discuss the topic with others with a like interest, learn something or share what they have learned. This is not a debate club where you make an argument just for arguments sake.

making the argument. Thats how one supports his position other wise you are just blowing smoke. Then I'll assume you can't make the argument by not answering the question. I asked you 3 times about this auger and you haven't answered.

I've posted the link and quoted the relevant passages. Who cares ? This is just another irrelevant argument you have thrown up based on nothing. The paper clearly states the auger is mechanically driven while the engine is running not hand operated.

I don't think it to much to ask for your position on this auger thing. I asked you to go to You Tube and you refuse. Time to bring in more of Tom and less of quotes by others cuzz you sound like an encyclopedia! Its not enough to quote out of books and following with 10 words of your own saying "thats the way it is". Where is the passion in that? It comes across to me as something I find contemptable and that you are no where near on par in these posts.

I've watched dozens of Stirling engine videos on You Tube and elsewhere. I've already seen any number of engines you might like to count running on either a steady flame from a candle, oil lamp, sterno can or some other constant source of heat, such as the sun. There are several references to small model Stirling engines running on a candle right in this forum.

You make this absurd and grandiose assertion: "Candles running a model Stirling? Haven't seen many using candles. Modelers use the "totally adjustable heat input device". Someday you will know of this device." ; "This goes right to your lack of observation. I want you to go to "You Tube" and let me know how many Stirlings have a candle for heat supply vs those that use the "totally adjustable heat input device". Everyone else reading here is going to and quickly find out and see that not only do you not read what you write, but you don't have any credibility here also by making statements that aren't so."

I'm sorry, but I feel no inclination to cater to your apparent lunacy. My statement was that Stirling engines are not generally equipped with a carburetor or a throttle or a gas peddle to regulate the fuel or heat input while the engine is in operation. If someone wishes to focus more sun on the engine, add another candle, turn up the flame or whatever they can certainly do so, but generally speaking a Stirling engine runs on a constant heat input. You don't "step on the gas" in a Stirling engine.

Even if you did, or could with your mysterious "totally adjustable heat input device" it would not change the thermodynamic principles involved (i.e. heat energy changing form and "disappearing") Whatever the heat input, whatever the efficiency of the heat sink to dissipate heat, whatever the work load on the engine, the formula is the same. i.e. Heat dissipated = Heat In minus whatever heat "disappears" as a result of being converted into work.

The more heat converted into work the less heat there is left over to cause overheating. An engine running with no-load would have a tendency to overheat as no heat is being converted into work so more heat would build up or would have to be dissipated with some additional heat sink. like an ice cube or a fan or larger cooling fins.

I'm not going to go searching for some information on You Tube or anywhere else to try and find support for or against your nonsensical assertions.

As I've stated before: "I have no intention of going in search of some nonexistent reference in an effort to find support for your assertion."

Perhaps I wasn't the most idea adversary in the discussion here and this forum is not well attended. Only a couple others chimed in.

Your insistence on taking an adversarial position, apparently with no regard for truth or reality one way or the other, but just to be argumentative is pretty hard for me to take. I imagine the same would be true for others. Who would care to wade through page after page of petty bickering and nonsense just to post here ?

You pretty much diverted the topic into a grammar lesson to define the meaning of common words like "against" and "as". You insist on asserting ideas and concepts that are patently false and have no correspondence with reality whatsoever.

i.e. The expanding hot air does not push the piston in a hot air engine. ; Stirling Engine heat input is "totally adjustable" and anyone who says that they more often run on a constant heat input has no credibility because it just isn't so.

It isn't up to me to go looking for evidence to refute such nonsense.

I could care less about my, or anyone else's "credibility" here. This is a Stirling engine forum not the CIA. I could care less about your supposed "totally adjustable heat input device" that most modelers supposedly use. As if one needed to be initiated into the secret order of the knights of Stirling sercetorum seclorum or something to have the privledge of knowing whatever foolish thing it is you are talking about.

"Someday you will know of this device...." woo woo

"Everyone else reading here is going to and quickly find out and see.... you don't have any credibility here...

Oh,... I'm so scared!

I might loose "credibility" on a Stirling engine forum if I don't go and do as Mr Longboy dictates.

I'm not wasting any more of my time with you here Mr "Longboy" or "Green" or whatever your name is. I've had quite enough of your nonsense.

[Longboy]

....."Reading a bunch of golf magazines.....does not make one a better golfer". (from "The Court-Martial of Billy Mitchell") We kept it going for two weeks but it was time to end and we posted our final thoughts yesterday. Got totally irritated with each other about three of those days and pulled it back to continue. Nobodys mind was changed and its "OK" Tom. The sun still came up today! Our talk was not a waste and ended civily. I enjoyed the banter. Dave.