The "Ice Bomb" thermal engine

[swansont]

51 minutes ago, Tom Booth said:

Atmospheric pressure is omnidirectional. Equal all around 

You're missing the point. If you have a containment vessel, the air pressure is irrelevant. It's how you can have vacuum chambers. The outside pressure, on the exterior walls is atmosphere, but the interior pressure is very small (essentially zero) because your chamber (steel, aluminum, titanium, whatever, but not probably paper) is rigid, and can withstand a pressure differential. 

So water in a tube can be exposed to the actual atmosphere on only one side. There will be pressure exerted by the vessel, and the value may be 1 atm of pressure, but it will not be the atmosphere that exerts it.

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Therefore the containment vesel only needs to withstand the added pressure of the 50 lb weight. Not atmospheric pressure 

No, the containment vessel will exert 1 atm on the water before you add the weight. In the water, everything is at 1 atm. (ignoring height effects for the moment). If the water exerts 1 atm, the containment vessel had better be exerting 1 atm back at it, if you are in steady state. 

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Even a rather substantial steel container would not withstand the pressure if the outside atmosphere were removed from all but the top.

If you take a vessel not designed to withstand the pressure, then sure, it is likely to fail. Way to cherry pick an example. It's like trying to demonstrate that flight is impossible by throwing a rock.

OTOH, I have used vacuum systems, and they don't crumple. Been on a submarine, too, and survived being under several atmospheres of pressure differential. The notable part being these are devices designed specifically for the task, which a barrel (designed to hold liquid in) is not.

35 minutes ago, Tom Booth said:

Removing heat might bring the water molecules (which are otherwise repelling each other to some degree), close enough together that some other more powerful intermolecular force results in a rearrangement into a crystal like formation.

Yes, we call it ice.

[Tom Booth]

Ice, though relatively solid, is also rather elastic, subject to deformation. Particularly at temperatures near the melting point, i.e. while freezing.

I don't anticipate making an engine for this ice box experiment out of titanium.

I can see in my freezer compartment that a thin wall plastic ice tray is quite sufficient to direct the expansion of the ice upward in one direction.

As I said, it's debatable and likely depends on the rigidity of the containment vessel, but I personally don't believe that even the pressure transmitted through a six inch steel plate is without effect, or less than instantaneous.

But it's largely a moot point IMO.

Of more relevance is that heat taken away to produce power output must be added back to complete the cycle of freezing and thawing.

On 5/7/2021 at 8:08 AM, John Cuthber said:

Fundamentally, the idea  depends on having a large "cold body" that you can use for cooling.

And if you have that, you can use it to run a "stream engine". 

That, will ultimately be the final word on the subject.

[swansont]

29 minutes ago, Tom Booth said:

I can see in my freezer compartment that a thin wall plastic ice tray is quite sufficient to direct the expansion of the ice upward in one direction.

Put a few kg of mass on top and see if that's still true.

 

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Of more relevance is that heat taken away to produce power output must be added back to complete the cycle of freezing and thawing.

Well, it's a heat engine, so yeah. You convert some small fraction of the heat into work. In this case probably a very small fraction, since efficiency depends on the temperatures involved.

 

[exchemist]

39 minutes ago, Tom Booth said:

 

Of more relevance is that heat taken away to produce power output must be added back to complete the cycle of freezing and thawing.

 

Bingo! You've got it - except that in fact you have to add back MORE heat than was taken away, in order to complete the cycle. So yup, its thermodynamics are just like any other heat engine. 

2 hours ago, Tom Booth said:

Welcome back!

Just been trying to establish what goes on in this theoretical ice power engine, stage by stage, throughout the freezing and thawing, lifting and lowering. Energy flow, etc.

And answer the question, can this engine be viewed as just an ordinary heat engine. Can we use standard formulas, equations, PV diagrams etc. to model it's behavior.

I've been thinking about how removing heat can result in positive work output.

Removing heat might bring the water molecules (which are otherwise repelling each other to some degree), close enough together that some other more powerful intermolecular force results in a rearrangement into a crystal like formation.

The energy to do the lifting then, comes from this intermolecular force.

Exactly.

The intermolecular force in the case of water comes mainly from hydrogen bonding. It happens that, because of the relative positions and angles the molecules need to take up, to maximise the energy released by forming these bonds, they have to move apart somewhat, compared to their average spacing in liquid water. Hence we get expansion on freezing. (One or two other materials also expand on freezing, but it is very unusual.) 

 

[Tom Booth]

58 minutes ago, exchemist said:

Bingo! You've got it - except that in fact you have to add back MORE heat than was taken away, in order to complete the cycle. So yup, its thermodynamics are just like any other heat engine. 

Right, only because the energy is provided by freezing in a freezer, the heat can be gotten for free, by just thawing the ice with ambient heat, perhaps, with some heat also contributed by the freezer.

The freezer is a heat pump, or functions in exactly the same way.

The hot condenser pipes on the back of the fridge provide us back the same heat previously removed from the water.

If careful about removing the engine from the freezer for thawing out, most of the cold in the freezer can be retained.

1 hour ago, swansont said:

Put a few kg of mass on top and see if that's still true..

I was shooting for more like around 20 kilograms.

For that the container might need to be slightly stronger than your average plastic ice tray.

[exchemist]

8 minutes ago, Tom Booth said:

Right, only because the energy is provided by freezing in a freezer, the heat can be gotten for free, by just thawing the ice with ambient heat, perhaps, with some heat also contributed by the freezer.

The freezer is a heat pump, or functions in exactly the same way.

The hot condenser pipes on the back of the fridge provide us back the same heat previously removed from the water.

If careful about removing the engine from the freezer for thawing out, most of the cold in the freezer can be retained.

However the electricity you use to run the freezer will exceed the power output of the ice engine.

[iNow]

1 minute ago, exchemist said:

However the electricity you use to run the freezer will exceed the power output of the ice engine.

Which brings us full circle back to the very first reply in this thread where I said: 

 

On 5/7/2021 at 12:41 AM, iNow said:

What is the energy source for cooling the water below freezing point?

 

[swansont]

2 minutes ago, exchemist said:

However the electricity you use to run the freezer will exceed the power output of the ice engine.

Right. Which means the energy would be better put to use on a more efficient device.

[Tom Booth]

4 minutes ago, swansont said:

Right. Which means the energy would be better put to use on a more efficient device.

The night sky?

https://www.fieldstudyoftheworld.com/persian-ice-house-how-make-ice-desert/

 

[exchemist]

7 minutes ago, Tom Booth said:

The night sky?

https://www.fieldstudyoftheworld.com/persian-ice-house-how-make-ice-desert/

 

Yes, that would be the principle employed by the natural ice engines you get at the tops of mountains or in deserts, as @sethoflagospointed out a while back. You can certainly exploit the temperature difference between day and night to run an engine.

Just don't imagine you can run a heat engine with only a heat source and no heat sink. That is wacko - like poor Tesla.  

[Tom Booth]

2 minutes ago, exchemist said:

Yes, that would be the principle employed by the natural ice engines you get at the tops of mountains or in deserts, as @sethoflagospointed out a while back.

I must have missed that.  not in this thread is it?

What's these "natural ice engines". Never heard of that before, I don't think.

Google returns nothing on "natural ice engine".

[DeepSeaBase]

I don't think you can make a bomb out of the device because there is very little energy contained in the system. A bomb has to have more energy contained in the system than the container holds. A bomb often doesn't have a container at all. Dynamite is basically all bomb, the container is just some wrapper to hold the bomb together.

When ice expands it will exert some force on the container, the energy in the system is the force required to break the container.

As soon as the ice breaks the container the system loses all energy. It doesn't release that energy anywhere, it has no energy.

30 minutes ago, Tom Booth said:

The night sky?

https://www.fieldstudyoftheworld.com/persian-ice-house-how-make-ice-desert/

While I am fascinated by these myself, their performance is grossly over-exaggerated.

The ice factories in Persia were not actually creating conditions for ice, but rather were exploiting conditions for ice that already existed.

They were basically ice caves with some human infrastructure to give them a nudge.

There's more energy in a refrigerator today than what Persia was nudging with huge architectural feats to help nature create ice for them.

[swansont]

1 hour ago, Tom Booth said:

The night sky?

https://www.fieldstudyoftheworld.com/persian-ice-house-how-make-ice-desert/

 

How much cycles will you get per night?  

Now, imagine running a heat engine at a higher temperature (i.e. at 373K instead of 273), and using the same heat sink. What happens to the efficiency?

[exchemist]

1 hour ago, Tom Booth said:

I must have missed that.  not in this thread is it?

What's these "natural ice engines". Never heard of that before, I don't think.

Google returns nothing on "natural ice engine".

Yes it's on this thread a couple of pages back. I was referring to the mechanism that causes frost shattering of rock. Water gets into cracks, freezes at night, jacking open the crack, thaws again, refreezes and jacks it open a bit more, etc.  

I was being a bit figurative, as it is not a constructed engine as such, but it does operate in a cycle, exploits a heat source and heat sink and does mechanical work, using water as the working fluid, by exploiting the ice/water phase change.

So if you put it like that, it has all the elements of an engine. 

28 minutes ago, Tom Booth said:

No.

In the first experiment I performed, running the engine on a cup of hot water. The entire engine was covered with insulation, so only the mouth of the cup containing the hot water contacted the bottom of the engine.

Someone suggested that partially insulating the bottom plate (hot side) might have effectively increased the temperature difference by retaining more heat at the bottom.

So I tried again with the bottom mostly exposed and just the top (cold sink side) insulated. It made no difference. In both instances the engine ran at higher RPM and more energetically than with the "sink" (top cold plate) exposed to ambient air.

More interesting in some ways was that with the engine running on ice, and the ice kept well insulated. The partly melted ice re-froze repeatedly after the engine ran for about five minutes.

But last time I tried posting the video of the experiments, the discussion was locked, and the moderator said not to start another topic on that subject.

 

That's because videos are a crap way of communicating experiments. To analyse what you did, we need to see a precise description of the exact set up, with a diagram.  

Whatever you did, you did NOT run it without a heat sink. That I guarantee.  

[sethoflagos]

Post deleted

 

 

Edited May 10, 2021 by sethoflagos
OP has lost interest in OP

[Ora Todd]

On 5/8/2021 at 2:27 PM, Tom Booth said:

Marvelous! so if the "refrigerator" is Very very well insulated. A Dewar within a Dewar wrapped in Aerogel blankets that how to  wash a burrito blanket a few times and our machine does lots and lots of heavy lifting we could keep the process of intermittently harvesting atmospheric heat going on for some time on  https://theburritoblanket.net/how-to-wash-a-burrito-blanket/ without having to run the refrigerator at all.

If it is then you still need to water to freeze

[Tom Booth]

8 hours ago, exchemist said:

However the electricity you use to run the freezer will exceed the power output of the ice engine.

Well, that's the Crux of the issue isn't it.

The ice engine though, is, so to speak "charged" by melting the ice, outside the freezer, with Ambient heat in the atmosphere. And, it's also, with the ratchet system, possible to gain back some energy as the weight is lowered back down.

Put back into the freezer, energy is returned in two ways. 1) as the ice forms lifting the weight and 2) the heat pulled out of the ice is concentrated as high grade heat:

 

Now, I'm not sure exactly how all that adds up, but the different forms of energy that can be harvested with this odd ball arrangement just seems to keep adding up.

And for the most part, once the freezer is cold, by being careful about how we take the engine in and out, it could stay pretty cold for some time without needing to run at all.

While the ice engine is running continuously.

Now a refrigerator compressor, as we all know, has to work pretty hard and draws quite a few amps.

But one way to lighten the load on the compressor is to cool the condenser tubes, shown above.

Keeping them relatively cool, by drawing off the heat, makes compressing the refrigerant much easier and more effective.

What better way to draw off the heat than by using it to also run a heat engine.

If we're going to draw all that heat out of the ice, of necessity, to run the ice engine, though it primarily produces power by being charged with freely available ambient heat.

Now that we have got that heat, highly concentrated in one place, why throw it away?

But a better arrangement of the condenser coils would be to spiral them in a tight loop on the heat input side of our heat engine.

 

Edited May 11, 2021 by Tom Booth

[sethoflagos]

28 minutes ago, Tom Booth said:

Put back into the freezer, energy is returned in two ways. 1) as the ice forms lifting the weight and 2) the heat pulled out of the ice is concentrated as high grade heat:

The heat content of low pressure gaseous refrigerant is just waste heat. Only the Work term counts. 

[Tom Booth]

And earlier, didn't someone say that there was "less heat" to be removed from the freezer for some reason?

27 minutes ago, sethoflagos said:

The heat content of low pressure gaseous refrigerant is just waste heat. Only the Work term counts. 

Not sure what your trying to say here exactly.

By low pressure gaseous refrigerant, you mean the refrigerant in the expansion tubes where heat is removed from the freezer?

Do you know how a refrigerator works?

The refrigerant that just picked up all that heat is compressed to a high pressure and high heat in the condenser in the back of the refrigerator.

It's only "waste heat" to a refrigerator. Still quite suitable to run a heat engine when so conveniently concentrated in one place.

It's only of no use to a refrigeration system.

27 minutes ago, sethoflagos said:

Only the Work term counts. 

The "Work term"?

You'll need to break that down or explain what you mean.

Work, in the sense of "WORK" in thermodynamics, goes out of the freezer as the ice swells and does "work" lifting a weight or turning a wheel for a generator or whatever.

But some additional heat is inevitably going to need to be removed from the freezer from time to time. That "waste heat" can be recovered from the condenser with a heat engine.

If you think that can't be done because it's waste heat, well, it's only waste heat if it goes to waste. Right?

The condenser on a fridge gets plenty hot to run a heat engine. And it could be designed to get a lot hotter, without actually getting hotter, because the heat engine would also turn THAT HEAT into "work" as well and in the process help keep the coils and therefore also the refrigerator colder.

Edited May 11, 2021 by Tom Booth

[sethoflagos]

32 minutes ago, Tom Booth said:

By low pressure gaseous refrigerant, you mean the refrigerant in the expansion tubes where heat is removed from the freezer?

Yes

33 minutes ago, Tom Booth said:

Do you know how a refrigerator works?

I've only designed refrigeration cycles down to 80 K, not the deep cryogenic stuff.

37 minutes ago, Tom Booth said:

The refrigerant that just picked up all that heat is compressed to a high pressure and high heat in the condenser in the back of the refrigerator.

Yes, so the refrigerant can be condensed upstream of the expansion valve.

42 minutes ago, Tom Booth said:

It's only "waste heat" to a refrigerator. Still quite suitable to run a heat engine when so conveniently concentrated in one place.

You're not recovering the heat from the cooling stage here, you're recovering excess heat produced by a low efficiency cheap domestic compressor. It is still waste heat.

 

 

[Tom Booth]

11 minutes ago, sethoflagos said:

You're not recovering the heat from the cooling stage here, you're recovering excess heat produced by a low efficiency cheap domestic compressor. It is still waste heat.

So where exactly do you think the heat removed from the inside of the refrigerator goes?

Granted, more efficient compressors may be available than typically found in a domestic refrigerator.

The refrigerant still circulates in a loop.

A refrigerator is the same as a heat pump. It's job is to move heat from inside the refrigerator to the outside.

The heat cannot dissipate to the outside without being elevated in temperature. Since heat only flows from hot to cold. Therefore, the refrigerant gas is compressed. The heat is concentrated so it is warmer than the outside air, that way it will transfer to the outside.

The heat from the inside could be transfered to a heat engine just as well in exactly the same way.

Edited May 11, 2021 by Tom Booth

[sethoflagos]

10 minutes ago, Tom Booth said:

So where exactly do you think the heat removed from the inside of the refrigerator goes?

Into the suction port of your compressor where you heat it up with your costly electricity.

[Tom Booth]

13 minutes ago, sethoflagos said:

Into the suction port of your compressor where you heat it up with your costly electricity.

The compressor could be driven by anything. How it's driven is irrelevant. How much it cost is irrelevant. The compressor could be powered by a driveshaft from a paddle wheel in a nearby river.

The compressor could operate perfectly, contributing no heat whatsoever. The heat from the evaporator from inside the refrigerator is still concentrated in the condenser on the outside to be dissipated.

The compressor gets hot, because it's packing all that refrigerant into the condenser at high pressure which concentrates all the heat removed by the evaporator.

---------

Personally, I'm more interested in Air cycle system refrigeration, than vapor compression.

It produces a much greater temperature differential and uses no dangerous, ozone depletion or greenhouse gas.

In applications where both poles of the temperature differential can be utilized, it's efficiency is good.

 

[exchemist]

6 hours ago, Tom Booth said:

Well, that's the Crux of the issue isn't it.

The ice engine though, is, so to speak "charged" by melting the ice, outside the freezer, with Ambient heat in the atmosphere. And, it's also, with the ratchet system, possible to gain back some energy as the weight is lowered back down.

Put back into the freezer, energy is returned in two ways. 1) as the ice forms lifting the weight and 2) the heat pulled out of the ice is concentrated as high grade heat:

 

Now, I'm not sure exactly how all that adds up, but the different forms of energy that can be harvested with this odd ball arrangement just seems to keep adding up.

And for the most part, once the freezer is cold, by being careful about how we take the engine in and out, it could stay pretty cold for some time without needing to run at all.

While the ice engine is running continuously.

Now a refrigerator compressor, as we all know, has to work pretty hard and draws quite a few amps.

But one way to lighten the load on the compressor is to cool the condenser tubes, shown above.

Keeping them relatively cool, by drawing off the heat, makes compressing the refrigerant much easier and more effective.

What better way to draw off the heat than by using it to also run a heat engine.

If we're going to draw all that heat out of the ice, of necessity, to run the ice engine, though it primarily produces power by being charged with freely available ambient heat.

Now that we have got that heat, highly concentrated in one place, why throw it away?

But a better arrangement of the condenser coils would be to spiral them in a tight loop on the heat input side of our heat engine.

 

No. You continue to add confusion. I start to fear this may be deliberate on your part, to keep the Tesla dream alive.

Suppose the ice engine converts 5% of the heat input from the ambient surroundings into lifting the weight.

The other 95% is exported by the ice engine into the compartment of your freezer.  

Your freezer then re-exports this heat back into the ambient surroundings. To do that, it does work, input in the form of electrical power.

So the amount of heat coming out of the freezer radiator is the 95% of the heat that the ice engine took from the surroundings, PLUS the extra heat due to the energy input from the electricity consumption of the freezer.  

The theoretical minimum this extra will be is the missing 5% that the ice engine converted to work. In practice, it will more - quite a lot more, since neither the ice engine nor the freezer heat pump will achieve Carnot efficiency.   

It does not matter how you dress it up, or make it complicated to obscure what is going on. That is the bottom line. You will end up consuming more energy from electricity than the work the ice engine does. 

Edited May 11, 2021 by exchemist

[Tom Booth]

7 hours ago, exchemist said:

No. You continue to add confusion. I start to fear this may be deliberate on your part, to keep the Tesla dream alive. 

It can be confusing, but I'm trying to sort it out myself, not intentionally trying to confuse anyone.

Some applicable hard mathematics or PV / entropy charts to clear things up, is what I was hoping for.