Stirling Engine & Heat Pump

[VincentG]

A narrow chamber of a given volume should have higher temp/pressure than a wider chamber with more distance between the walls but the same total volume?

No such temperature or pressure differences due to the chamber architecture exist.

Tom what you’re missing is that it’s pounds per square inch. So as the surface area increases, so does the overall force.

[Tom Booth]

A narrow chamber of a given volume should have higher temp/pressure than a wider chamber with more distance between the walls but the same total volume?

No such temperature or pressure differences due to the chamber architecture exist.

Tom what you’re missing is that it’s pounds per square inch. So as the surface area increases, so does the overall force.

Not sure what you're talking about.

I think I distinctly said the surface area would not change, or you could change the volume without a change in surface area of the container.

To me that suggests pressure has nothing to do with "pings" or direct impacts on the interior chamber walls but with the molecular repulsion between gas molecules.

[Fool]

.

Another thought Matt,

"Pings", contact with external surface area, if increased in frequency would transfer additional heat to the outer surface.

A narrow chamber of a given volume should have higher temp/pressure than a wider chamber with more distance between the walls but the same total volume?

No such temperature or pressure differences due to the chamber architecture exist.

Ping rate depends on density. Density depends molecules per volume. There is nothing in any equation for container surface area. Free path is independent of container shape, or surface area, because free path is way shorter than any realistic container dimensions, except for the Casimir effect in a vacuum. Density is number of molecules per cubic centimeter. It's quite high for the conditions inside our Stirling engines.

Please keep in mind that when building our Ltd Stirling engines, we are operating in the macroscopic world, not the microscope or quantum level. Sciences inability to go from quantum level to macroscopic level moves theses garage theories into the fantasy world, fairly quickly. Your apparent knowledge in both should lead you to being more humble, not more insistent. You bring in erroneous straw man arguments like that.constanly.

.

[Fool]

.

At this point I like to apologize to Tom, or maybe it's a thanks. Because of incessant erroneous whining, I researched a little and found the following describing how classical theory treats real gasses, and how they differ from ideal gasses, and when the ideal gas law is a good fit. Like Newtonian mechanics being a good fit for engineering things to be used here on Earth when it is an old erroneous outdated theory, replaced by Relativity.

https://chem.libretexts.org/Bookshelves ... lar_Forces

Also:

https://en.m.wikipedia.org/wiki/Real_gas

From Google searches, the name 'Kinetic Theory' is given to and refers to only the ideal gas law theory. The worst part of that is, when modeling real gasses, the same descriptions for molecular interactions are used, except that size and molecular forces are Incorporated. Too bad they don't call it 'kinetic real gas theory'. Now that would make sense.

Note: it is not caloric real gas theory, or Fudd's real gas theory. It has been formulated from kinetic theory.

The graphs used in those web pages are built up from data taken from real gases. Real gas data has been around since before caloric, and kinetic theory. If you are working with real gases, you will be using real gas data tables and charts, not ideal gas laws.

My guess is, and it is just a guess, if you were to calculate, formulate, Carnot's theorem using real gas equations, it would show an even lower maximum efficiency than that which we all know. It would tend make Tom's 2nd law ranting here even more worthless than we already know it is. Keeping quiet about your doubts turns out to be smarter than all the straw men and misunderstanding he brings forth. But it's just a guess.

When the volume of a gas stays constant, how could the number of particles per cubic inch change? It can't. It doesn't. The average distance between molecules must stay the same. The mean free path must stay the same. Molecular size stays the same. Attractive forces stays the same. Repulsive forces stay the same. The only thing that could possibly reduce average pressure with temperature decrease and volume constant, is speed and frequency of impacts. As Matt put it, ping rate and momentum. It is independent of inside or outside container surface area. Hence the term 'pressure', or force per square inch.

.

[Tom Booth]

According to kinetic theory there is no interaction between gas molecules at all.

Also according to kinetic theory gas molecules are dimensionless points.

Mean free path is calculated on the basis of molecular SIZE.

Since a "dimensionless point" has no size it logically has no limited "mean free path" as far as kinetic theory is concerned.

Kinetic theory paints a picture of the "path" of gas molecules "expanding forever" (a phrase you've applied to gas molecule behavior repeatedly) until colliding with the container wall, not attracted to or interacting at all with the other gas molecules.

Real gas theory is just kinetic theory with size and forces added.

Basically.

Size and "forces" like intermolecular forces of attraction and repulsion.

There is a big difference IMO, between a picture of gases freely ricocheting off the interior walls of the engine at the speed of sound with no intermolecular forces, and that of gases in a container being basically "locked in" by their neighboring molecules to a distance many many times smaller than the width of a human hair with attractive forces between the molecules.

[Fool]

.

gases in a container being basically "locked in" by their neighboring molecules to a distance many many times smaller than the width of a human hair with attractive forces between the molecules.

Please explain how "locked in" gas molecules allow an aircraft to pass through?

It seems that one of the fundamental differences between classical thermodynamics and the new and improved Tom Booth theory is what kind of bonds if any, or freedom to move about with lots of space between, that the molecules have. Can you explain the strength of those bonds? How much energy it takes to break them? What escape velocity would the need? If so, please relate it to temperature, pressure, and density.

Tom's theory has molecules "locked in" with spring like firmness. Classic theory has real molecules:

Locked for solid.

Mobile but in close orbit for liquid.

Freely bouncing for gas. (Containment possible)

Tom's theory makes no predictions of how solid, liquid, and gas differ, classic theory does. In fact I can't find anything that Tom's theory predicts. I can with Classical Theory, mathematics, and empirical data, it already predicts better and more completely. The "locked in" gas molecules theory, fails to predicted many many things, and is in a complete opposition to almost all flowing gas and an object moving through the gas phenomenon . The same is true of any 'locked in liquid molecules' theory.

Classical theory may have many simplifications that stop it from grand unification, but it has lots of useful in the right areas simplifications that if used correctly it will be reliable in beneficial to design.

"locked in" molecules, works great for a solid, but completely fails for liquid or gas.

Your evidence for 'gas pulling in' is sadly lacking. Molecules, yes, not gas. The phenomenon, replaced by a bouncing model is way better. Liquid pooling under a cloud of gas at micro bars is acceptable, it has a gas at a positive pressure filling the container. Not contraction, pooling and low positive pressure.

Evidence for gasses always pushing is found in every phase diagram and data table out there. Gasses always have a positive 'absolute pressure'. (Do not get confused by 'gauge pressure.) Vapor pressure is always positive no matter the substance, no matter the temperature. If you disagree please show data to support your claim.

Substances either sublime or evaporate from liquid in a vacuum, regardless of the temperature. (Being liquid or solid in a vacuum depends on temperature.) Some faster than others. Some very very slowly. Some quite rapidly depending on temperature. The vapor coming from a substance in a vacuum has a positive pressure. It will move outwards in a zero gravity vacuum until hitting a container wall, or other gas molecule. That positive pressure limits evaporation, bounce back.

So it is your choice what to use. Classical theory, with all its difficulties and predictive power? Or, the useless incorrect 'locked in molecules' theory?

To me, it seems much more productive to use a reliable theory, than a useless one.

Read the thread where someone kindly translated japanese to English about a large LTD engine. It started from the Schmidt Theory, known to be inaccurate and wrong, but close. They used it for sizing. Good idea. The final engine performed close to what was desired, because of the use of the Schmidt Theory. They didn't have any problems using the theory. Their biggest hurtles were design parameters especially the piston rings.

Concentrating on piston ring designs, or suppliers, seems way more productive here than worrying about the small deviations between kinetic theory, and real gas theory, unless you are trying to earn a university certified PHD. Then the five percent or so improvements to classical theory would succeed for you, if you can get that close. Good luck. Show the math.


.

[Tom Booth]

.

gases in a container being basically "locked in" by their neighboring molecules to a distance many many times smaller than the width of a human hair with attractive forces between the molecules.

Please explain how "locked in" gas molecules allow an aircraft to pass through?

Sure.

Forces of attraction and repulsion between gas molecules are, or are similar to "fields" like magnetic fields of force or charge, but the attractive/repelling force is in 3 dimensions, similar to quantum locking in relationship to EACH OTHER.

But just as you can pass your hand through a magnetic field though the magnets repel or attract each other, we, (and aeroplanes) can move through the air with little resistance.

Don't have time to read or comment on the rest of your post. Maybe later.

What is the difference between WIND and still air? What lifts an aeroplane wing?

If air molecules did not move together en mass, what is wind? How would sound propagate through gas molecules in completely random motion that never influence each other?

[Fool]

.

But just as you can pass your hand through a magnetic field though the magnets repel or attract each other, we, (and aeroplanes) can move through the air with little resistance.

So you are implying that the gas molecules attracting each other, are "locked in", yet other materials can pass between them, spread them without much force, and are not attracted to them so they don't stick to each other. Seems kind of contradictory. How does the air molecule bond break, spread a great distance apart the come back together? Answer the air around it is always pushing and pushes it back together.

Forces of attraction and repulsion between gas molecules are, or are similar to "fields" like magnetic fields of force or charge, but the attractive/repelling force is in 3 dimensions, similar to quantum locking in relationship to EACH OTHER.

Molecules interact using nothing more than electric Fields. The plus's and minuses from the protons and electrons all add up to make things what they are. Those same forces allow materials to transform from energy attainment from solid to liquid to gas, etc.

What is the difference between WIND and still air? What lifts an aeroplane wing?

If air molecules did not move together en mass, what is wind? How would sound propagate through gas molecules in completely random motion that never influence each other?

All of which contradicts "locked in" molecules. The fluid must be free of static solid bonds to allow it to separate and flow, both from each other and around things.

The gravitational field of Earth pulls 'downwards' every air molecule. The molecules near sea level have on them the combined weight of all the air molecules above them in our atmosphere, about 20 miles tall. It averages near 14.7 psi.

Because of that pressure the speed of sound is about 730 miles per hour. A disturbance, causes an increase in local pressure, which pushes outwards from the origin by pushing on more air. The pressure wave propagates like separate dominos set up side by side.

Wind is caused by local heating and cooling causing a high pressure in one area which flows outwards into lower pressure areas. Wind is like a train pushing a line of cars. No coupling or pulling necessary. Push.

The air response has little to do with molecular attraction. But it has a lot to do with repulsion. Molecular repulsion is what causes bounce. But the mean free path is still way larger than the diameter and effect of attraction and repulsion.

Mean free path of air 60nm. Size of nitrogen molecule 0.305 nm. To put this perspective a car being about 7 ft wide 60/0.305c7)/5280 is a little over 1/4 mile. Your neighbors car may be closer.

Does your car feel an attraction to it? No. But try to share an intersection with it at the same time, you will feel repulsion/bounce. Only with your car it will be inelastic and much of the energy will dissipate as deformation and noise. "Heat".

.

[Tom Booth]

By "locked in" I meant the gas molecules tend to maintain a certain distance from each other, similar to the small super magnets in this video:

https://youtu.be/hcggjrJbHmk

Attraction and repulsion are not "solid static bonds".

The gravitational field of Earth pulls 'downwards' every air molecule. The molecules near sea level have on them the combined weight of all the air molecules above them in our atmosphere, about 20 miles tall. It averages near 14.7 psi.

Because of that pressure the speed of sound is about 730 miles per hour. A disturbance, causes an increase in local pressure, which pushes outwards from the origin by pushing on more air. The pressure wave propagates like separate dominos set up side by side.

I can agree with all that. "Like dominos set up side by side". Not flying off in all directions completely independent of one another. Of course they need to be close enough to attract in the first place. A single gas molecules in a vacuum has no attraction to other gas molecules that are not there.

Mean free path of air 60nm. Size of nitrogen molecule 0.305 nm. To put this perspective a car being about 7 ft wide 60/0.305c7)/5280 is a little over 1/4 mile. Your neighbors car may be closer.

Well, to put that in perspective for our concerns, 60nm is a few millionth of an inch.

So what are the chances of a gas molecule traveling from the hot plate of a Stirling engine to the face of the piston without running into another gas molecule?

I would say, probably zero in any one cycle, other than via a "domino effect" similar to how energy is transmitted through a Newton's Cradle. But with the metal balls "attached" together by springs i.e. balance of attractive and repulsive forces like the magnets in the above video.

So, as a practical consideration for engine design, keeping cold air on the cold side of the engine and hot air on the hot side, separated by a regenerator probably has no bearing on the "path" of individual gas molecules traveling between the hot plate and piston. The individual molecule never does and never could make any such trip.

The kinetic theory image often shown of gas molecules ricocheting off the interior walls of a container hardly ever interacting with each other at all is apparently incorrect.

https://youtu.be/robEY-idcLU

I think it is more like those magnets that can be pulled apart or pushed together or scattered by an outside force but left to themselves assume a symmetrical pattern, again, like the small super magnets in the above video.

Relatively speaking the nucleus of an atom and it's electrons are "miles" apart, so the atom is "mostly empty space" as well, does that mean the electrons are not effectively "locked" into an orbit around the nucleus?

Not really all that different from the spring-ball model of a solid.

https://youtu.be/p6VeDd0ukXI

Just longer, weaker "springs" not so tightly bound and further apart but still kept at a certain distance from one another by the balance of attractive and repulsive forces.

This seems to be a more realistic picture of how gases actually behave, not flying off "forever" in straight lines, completely independent of one another until they collide with a solid object, like the inside wall of the engine or face of the piston.

[Fool]

.

The following might help :


https://en.m.wikipedia.org/wiki/Intermolecular_force

The following has bolding emphasis added by me:

Intermolecular forces are repulsive at short distances and attractive at long distances (see the Lennard-Jones potential).[20][21] In a gas, the repulsive force chiefly has the effect of keeping two molecules from occupying the same volume. This gives a real gas a tendency to occupy a larger volume than an ideal gas at the same temperature and pressure. The attractive force draws molecules closer together and gives a real gas a tendency to occupy a smaller volume than an ideal gas. Which interaction is more important depends on temperature and pressure (see compressibility factor).

In a gas, the distances between molecules are generally large, so intermolecular forces have only a small effect. The attractive force is not overcome by the repulsive force, but by the thermal energy of the molecules. Temperature is the measure of thermal energy, so increasing temperature reduces the influence of the attractive force. In contrast, the influence of the repulsive force is essentially unaffected by temperature.

When a gas is compressed to increase its density, the influence of the attractive force increases. If the gas is made sufficiently dense, the attractions can become large enough to overcome the tendency of thermal motion to cause the molecules to disperse. Then the gas can condense to form a solid or liquid, i.e., a condensed phase. Lower temperature favors the formation of a condensed phase. In a condensed phase, there is very nearly a balance between the attractive and repulsive forces.

That super magnet video had no demonstration for velocities greater than escape velocity. And almost zero bounce demonstration.

It was good for liquid representation, where attractive force is in ballance with repulsive force and velocity. In orbit, velocity can be thought of as causing centrifugal force. Escape velocity can be thought of as having too much centrifugal force.

Thermal energy completely overcomes the attractive force so much so that it has little effect on gasses when not near boiling temperatures or pressure. That is the basic real reason the ideal gas law is so accurate. Large distances, and high speed, between gas molecules.

The range of molecular attraction in a gas is considered to be very small, essentially negligible, because gas molecules are typically far apart due to their high kinetic energy, meaning there is minimal attractive force between them; this is especially true for ideal gases where molecular attraction is assumed to be zero.

In other words. Real gasses have little influence from their attraction. They don't 'contract'. They always push. Lower pressures are pushed together by higher pressures. When a gas volume decreases, it is because it is compressed by some outside force, outside the gas volume.

.

[Fool]

.

It is kind of misleading to say distances between gas molecules are large as the distances are constantly changing. They get close enough to bounce.

It would be better to say average distances are large, compared to range of forces or molecular size. They spend more time in flight away from the forces, than bouncing off one another.

.

[Tom Booth]

.

The following might help :


https://en.m.wikipedia.org/wiki/Intermolecular_force

The following has bolding emphasis added by me:

Intermolecular forces are repulsive at short distances and attractive at long distances (see the Lennard-Jones potential).[20][21] In a gas, the repulsive force chiefly has the effect of keeping two molecules from occupying the same volume. This gives a real gas a tendency to occupy a larger volume than an ideal gas at the same temperature and pressure. The attractive force draws molecules closer together and gives a real gas a tendency to occupy a smaller volume than an ideal gas. Which interaction is more important depends on temperature and pressure (see compressibility factor).

In a gas, the distances between molecules are generally large, so intermolecular forces have only a small effect. The attractive force is not overcome by the repulsive force, but by the thermal energy of the molecules. Temperature is the measure of thermal energy, so increasing temperature reduces the influence of the attractive force. In contrast, the influence of the repulsive force is essentially unaffected by temperature.

When a gas is compressed to increase its density, the influence of the attractive force increases. If the gas is made sufficiently dense, the attractions can become large enough to overcome the tendency of thermal motion to cause the molecules to disperse. Then the gas can condense to form a solid or liquid, i.e., a condensed phase. Lower temperature favors the formation of a condensed phase. In a condensed phase, there is very nearly a balance between the attractive and repulsive forces.

That super magnet video had no demonstration for velocities greater than escape velocity. And almost zero bounce demonstration.

It was good for liquid representation, where attractive force is in ballance with repulsive force and velocity. In orbit, velocity can be thought of as causing centrifugal force. Escape velocity can be thought of as having too much centrifugal force.

Thermal energy completely overcomes the attractive force so much so that it has little effect on gasses when not near boiling temperatures or pressure. That is the basic real reason the ideal gas law is so accurate. Large distances, and high speed, between gas molecules.

The range of molecular attraction in a gas is considered to be very small, essentially negligible, because gas molecules are typically far apart due to their high kinetic energy, meaning there is minimal attractive force between them; this is especially true for ideal gases where molecular attraction is assumed to be zero.

In other words. Real gasses have little influence from their attraction. They don't 'contract'. They always push. Lower pressures are pushed together by higher pressures. When a gas volume decreases, it is because it is compressed by some outside force, outside the gas volume.

.

You're obviously just cherry picking, bastardizing, and probably intentionally misinterpreting your own reference:

Effect on the behavior of gases

Intermolecular forces are repulsive at short distances and attractive at long distances

This describes a spring like force. Repulsive when compressed ("short distances") and ATTRACTIVE when expanded ("long distances").

You change: "increasing temperature reduces the influence of the attractive force" to "Thermal energy completely overcomes the attractive force"

etc. etc.

Ignoring or corrupting what you don't like and twisting relative to absolute.

I can't be bothered.

I would use the same reference to support my previous statements, but without needing to disingenuously alter rewrit and reinterpreting the text.

No point in further discussion with you as you just put your own spin on anything and everything to have it conform to your own preconceptions.

I'm only interested in how a Stirling engine actually works. Not artificially propping up of one (mostly obsolete) theory or model.

The attractive and repulsive forces (including kinetic "bouncing") are in relative balance until heat is added REDUCING the attractive force relative to the repulsive. Obviously the molecular attraction is not non-existent or without influence as you (and Kinetic theory) portray.

Likewise, cooling the gas has the opposite effect. Reducing repulsive forces relative to the attractive forces.

When a gas is compressed to increase its density, the influence of the attractive force increases. If the gas is made sufficiently dense, the attractions can become large enough to overcome the tendency of thermal motion to cause the molecules to disperse. Then the gas can condense to form a solid or liquid

This directly contradicts your previous assertion that gases will never condense by pressure.

[Fool]

.

This describes a spring like force. Repulsive when compressed ("short distances") and ATTRACTIVE when expanded ("long distances").

No. It is not like spring forces. Springs get stronger when stretched to further distances. Electric fields, being what molecular forces are, get weaker when molecules are further apart. In fact they get weaker very quickly. Bonds that hold solids and liquids together are even weaker yet. They are only significant at a very limited and small range compared to molecular size.

Likewise, cooling the gas has the opposite effect. Reducing repulsive forces relative to the attractive forces.

No. Heating and cooling have no effect on attractive or repulsive forces. It only changes the speed of the molecules. On average.

For the three states of matter, sold-locked in, liquid-moble in orbit, Gas-free to escape each other if not contained (above their relative escape velocities). On average.

The bond lengths only change from temperature for solids and liquids. For gasses there is no bond, they are above the escape velocity, making and breaking the bond as they fly by.and bounce.

This directly contradicts your previous assertion that gases will never condense by pressure.

There is no contradiction. Gasses can only condense into liquid if both their temperature and pressure (dictating density) are correct. If compression is adiabatic, temperature will rise above the temperature needed for condensation at the new pressure. This is directly observable on a phase diagram.

Only after cooling back down to room temperature will propane or CO2 liquify under pressure. The heat of compression, adiabatic temperature rise, must be removed.



The rest of your post is wrong and has nothing to do with science or my scientific discourse.

.

[Tom Booth]

.

This describes a spring like force. Repulsive when compressed ("short distances") and ATTRACTIVE when expanded ("long distances").

No. It is not like spring forces. Springs get stronger when stretched to further distances. Electric fields, being what molecular forces are, get weaker when molecules are further apart. In fact they get weaker very quickly. Bonds that hold solids and liquids together are even weaker yet. They are only significant at a very limited and small range compared to molecular size.

Likewise, cooling the gas has the opposite effect. Reducing repulsive forces relative to the attractive forces.

No. Heating and cooling have no effect on attractive or repulsive forces. It only changes the speed of the molecules. On average.

For the three states of matter, sold-locked in, liquid-moble in orbit, Gas-free to escape each other if not contained (above their relative escape velocities). On average.

The bond lengths only change from temperature for solids and liquids. For gasses there is no bond, they are above the escape velocity, making and breaking the bond as they fly by.and bounce.

This directly contradicts your previous assertion that gases will never condense by pressure.

There is no contradiction. Gasses can only condense into liquid if both their temperature and pressure (dictating density) are correct. If compression is adiabatic, temperature will rise above the temperature needed for condensation at the new pressure. This is directly observable on a phase diagram.

Only after cooling back down to room temperature will propane or CO2 liquify under pressure. The heat of compression, adiabatic temperature rise, must be removed.



The rest of your post is wrong and has nothing to do with science or my scientific discourse.

.

Again, you twist and alter and intentionally misinterpret everything with your straw man arguments.

I say "spring LIKE" in respect to being attractive or repulsive. So you straw man that over to "stronger" or weaker, which, true or not, was not the point at all.

As far as attractive and repulsive, you ignore my use of "relative to" and where I make clear kinetic "speed of the molecules" however that may be interpreted would be on the "repulsive" side of the balance.

Etc. etc. you, I think, have serious reading and comprehension problems or are just being intentionally obtuse for the sake of argument, as always. You don't care what's true or accurate in reality.

Bottom line for me is the "classical" theories do not explain observations seen on the bench.

That gases DO infact have attractive forces that have a real influence is well recognized and helps explain some of the experimental observations better than the old kinetic theory.

[Fool]

.

I'm not twisting your words. I'm extrapolating them to show where they erroneously lead. You started with, locked in, then springs, then magnets. You keep twisting and turning to my points. My points are valid.

The bottom line is that for microstates atoms and molecules have positive and negative electric fields that both attract and repel each other.

Microstates, of solids have bonds and are locked in and have macrostate properties of tensile, compressive and shear strength. They also have coefficients of expansion from temperature, and stress verses strain, to name a few.

Liquids lack much tensile strength, but have similar compressive strength. They move around and are fluidic. They have viscosity.

Gases have no attraction. They have very little, but measurable and useable, compressive strength. They have instead of tensile strength, pressure, pushing. They never pull. They are not bound or in orbit with any other molecule. They bounce off all other molecules, if they didn't they would become liquid, and condense.

Molecules always both attract and repel. Gasses always push, but it isn't from molecular repulsion, except for bouncing. It is from being above the escape velocity. If released in open space, gasses will all expand forever, molecules never bouncing off each other ever again.

Unless you understand simple laboratory experiments demonstrating that gasses always push, you will never understand correctly, thermodynamics. Gasses always pushing was one of the earliest thermodynamic observations.

Try the following. Bell jar with a cup of room temperature water in it. Apply a piston pump to it. Expand the volume inside the pump cylinder. The pressure drops in the cylinder lower than the bell jar. The higher pressure in the bell jar pushes air and water molecules into the cylinder.

Compress the cylinder. Check valves appropriately close and open, volume heads towards zero. Pressure builds up above atmospheric, and the higher pressure in the cylinder pushes the air with some water gas out.

Since the pressure inside the bell jar is lower, some more water evaporates. The gasses inside the bell jar become a higher percentage of water. If the pump continues the air is fully removed and only water vapor, and in the cup liquid, is inside the jar.

At some point the temperature of the liquid in the cup becomes higher than the boiling point at the new pressure level. Boiling indicates that steam/vapor is being produced at low a temperature.

If the pump is stopped. The boiling stops. If the pump is restarted the boiling resumes.

Now think. How does the pump get vapor to come out of the jar by pulling on nothing. If the vapor/gas isn't filling the bell jar and pipe leading to the pump, it won't fill the pump cylinder. That filling, the bell jar, requires a positive pressure.

If the pump continues, ice will form in the liquid water cup. This becomes the triple point. The temperature and pressure at which all three coexists. Solid/ice, liquid/water, and gas/steam/vapor.

If the pump continues. All the liquid will eventually be gone. Positive pressure, but low, all the way to totally ice.

Once the liquid is gone the ice continues to sublime. That means that the ice is producing steam/vapor/gas that fills the bell jar, and pipe, with enough positive pressure to be pushed and pumped out. This is called freeze drying. It can be continued until the ice is completely gone. At that point there will be only a few atoms of water and glass molecules to fully fill the bell jar and pipe. But it is still a positive pressure.

Gasses always push. Solids sublime and liquids evaporated even at very low temperatures, if the pressure is low enough. But they still always push.

Put a balloon in a bell jar with a mechanism to open and close the balloon remotely. Put it in. Open the balloon. Same pressure in and out. Elasticity of the balloon pushes out air, or lets some in.

Close the balloon. Pump some air out from the bell jar. Balloon inflates. Air in the ballon is pushing.

Open the balloon. The balloon deflates. Rubber solid will contract. Close the balloon. Pump some more out. Balloon inflates. Air inside balloon again is pushing out.

This may be repeated to see how low the effect can be observed. Gasses always push. Never "contract".

Right now the above is just a thought experiment, but I've seen a similar demonstration, so i figure it will work, at least for a couple cycles.

Classical theories aren't perfect. But you do need to use them correctly. They explain most things very well and, and for most benches. The appearance that your bench shows an anomaly, is reason for you to do more, better, and different tests. People have suggested that.


.