Physicists help needed!!! Current technology limitations.

How about having a vessel (cargo-carrier, for instance, of any kind) with a central engine core that runs the entire length of the ship. Line up a whole lot of turbines, and have water intakes leading in from the sides infront of each one of them (like the air intakes of jet engines). That way, you avoid the problem of having diminishing power to each successive turbine. With the same amount of water passing through each turbine, the power output would be the same at each stage. Now I'm not an engineer, and there are sure to be problems with that seemingly simple idea--let me know if there are.

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Where does each turbine exhaust relative to the next turbine in line?

 

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The turbine exhausts are at 90 degrees to the next set of turbine intakes.

 

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MetaKron,

While Light may be a bit beligerant, he's right and you're certainly confused on this heat pump issue. The coefficient of performance (CP) is a ratio of the energy transferred for heating to the work (electrical energy used by the pump in this case) put into the cycle. Because you're getting energy from the environment this will be a number > 1.

CP is NOT a typical efficiency in the sense that it is calculated by energy-out/energy-in because we only consider the energy put into the pump as the "energy in", but we are getting energy "in" to the sytem through the transfer from the low temperature reservoir.

This is basic thermodynamics and these things exist (and work) all over the place in the real world. In fact your refrigerator is working on the same principle.

 

Hey, Flunch, if experimental evidence shows that it works, then I believe that it does work. It's still against the law, physical law that is. Just because it comes from a larger reservoir is meaningless when that larger reservoir is lower. This would be like saying that you experience a net gain in usable energy by pumping water from Lake Pontchatrain to a water tower because the lake is larger than the water tower.

No one has claimed to me or shown me test results that say that it takes less energy to move heat out of my refrigerator than is actually removed. I would give those results a lot of crediblity especially if the testers provided raw data and testing criteria. I will always give more credibility to experimental results than to anyone's guesses as to what the results will be.

Light couldn't explain the setup for whatever reason. Getting belligerent because you can't explain something is of course your choice, but it doesn't get any explaining done. What is clear from the Wiki articles, which I will go with for now, is that there is a number for the energy that is input into the system, and there is a number for the energy that you get out of the system. According to the laws of thermodynamics we can't get more energy out than we put in, and we can't move a given amount of heat uphill without expending that much energy to move it. Even when you conserve your investment in energy, you can only get a COP of a bit less than 2. The energy you put in pushes its own weight in heat minus losses, and is itself converted to heat. Maybe more than one, definitely less than 2.

A heat pump or any other device cannot be an isolated case of a violation of the 2nd law of thermodynamics. If there is one strong example of such a violation, that law is broken. We need to reinterpret our physical theory to take observed facts into account.

 

What? :bugeye:

 

Uh, yeah. A theory that fails to describe reality accurately is false. I accept the fact that there are limits to the accuracy of measurements, that's not the problem.

The theory may have to be revised. We may not have understood the theory well enough in the first place. It may be completely bogus.

 

MetaKron, let's try it one more time. And the only reason I lost patience with you earlier is that you seemed to making no attempt to try and understand and primarily because you took a strong know-it-all-already attitude. You aren't in a position to know all there is to know and it's annoying (for me) to deal with anyone like that. But I'll tone it down and see if we can make some progress here.

First of all, no - the laws of thermodynamics are correct and don't need revising. We just haven't gotten the operating principle of the heat pump across to you yet.

In many ways a heat pump can be compared to a hot-water solar heater. You install a solar collector on your roof and it absorbs heat from the sun. A small pump then takes that heated water into your house. In that case, I believe that you should be able to see that the small amount of energy (in electrical form) required to run the little pump is considerably less than the amount of energy ( in the form of heat) that is delivered to you.And there is no violation of thermodynamics here either. I hope you can surely see that. The principle is exactly the same as leaving a car parked in the sun ans the interior becomes heated (gains energy) without you having to expend any energy at all. The only difference in the car and the system at home that I just described is that you DO use a small amount of power, but only to deliver that energy to where you want it to be.

Now let's compare that solar system to a heat pump. In both cases, solar energy is used to heat our collector. In the solar system, the collector is the panel on the roof; for a heat pump, the collector is simply the outside air. Both will receive energy from the sun and store it for a period of time.

In the solar roof collector, the heat energy becomes concentrated in the water because it is somewhat trapped - just as it in in the inside of a car sitting in the sun. For a heat pump system, the energy is still collected but it's more diffused in the air - in other words it's not concentrated in one specific volume of material but rather spread out more. I believe you will also agree that a given volume of air at 30 degrees C will contain more energy than the same volume of air at 20 degrees C. And that forms the basis for the operation of the heat pump system.

The heat pump will take a huge volume (hundreds of cubic feet) of that 30 degree air, absorb a lot of the heat energy by evaporation of the refrigerant, and then blow the air back out at 20 degrees. (The actual working temperatures are different but we'll stick with those figures from our example above.)

The heat pump is not some sort of perpetual motion machine and has not created energy from nothing - it collected that energy from the air - by cooling the air. An ordinary window-type air conditioner does exactly the same thing. It "sucks" the heat from the air in a room and blows it outside. If you've ever been near one you will know what I mean. The air it's blowing outside is very warm. A heat pump works on that same identical principle and the only difference is that it's blowing the heat INSIDE the house instead of the air conditioner blowing it to the outside. In fact, you could take that very same window unit and turn it around and have it heat the room in the winter. And that's precisely what a heat pump does - it reverses to provide cooling in the summer and heating in the winter.

The laws of thermodynamics have NOT been violated in the least. All the system has done is move heat from one location to another. It has also increased the intensity of the heat, just as you felt the air conditioner do on the outside of the house. But it did not somehow miraculously "manufacture" that heat from nothing which would violate thermodynamics. The heat is already there - it just gets moved.

Now - does that help?

 

Light, you're not quite to where my problem is. My problem is not with the idea of taking heat from a larger mass at lower temperature and using it to warm a smaller mass to a higher temperature. The books do balance there. My problem is that we can describe what it does, where the energy comes from, where the accounts balance, and we can even physically prove that it works, but it contradicts things that we are taught about the way heat works. We are pushing heat uphill at a net gain for the energy expended. It takes energy to chill an area. I can see the books balancing if the cold end heat contributed energy to the cycle in a way that aided in pushing itself uphill. This would seem as if we are converting ambient heat to usable heat at a net gain.

 

OK, I think I see a little more of your problem. What you're failing to grasp is that there is NO net gain of energy - it's all already there. Just as with the solar collector, the "energy books" are balanced. And the solar collector in no way contributes energy to "pump the heat uphill" either. It simply moves the available heat. The heat pump does exactly the same. In both cases the source of the usable heat is the sun. Both of those systems simply concentrate it for delivery to where we want it to go.

In the heat pump, you are using a small amount of energy to drive the compressor which does the work of concentrating the heat that's already available. I feel you don't quite understand just how much heat is present in a large mass of air and how it can be removed - and taken elsewhere - just by dropping it's temperature a few degrees.

Question: I don't know what part of the world you live in so is it possible you've never seen the window air conditioner I was talking about? The operating principle is VERY clear if you can get to one.

 

MetaKron,

The problem you have is in how you're attempting to view the energy balance and apply an efficiency. A heat pump is not an easy device from which to derive a precise efficiency, that is why the CP is used.

The pump does the work of "pushing the heat uphill" as you put it. The available deliverable heat is the net of that, plus the heat gained from the low-temp reservoir, minus losses.

We are not converting ambient heat to usable heat at a net gain. Obviously we can't do that, that violates the 2nd law of thermodynamics... what we are doing is ADDING energy to the system via the pump.

So you have heat from low-temp reservoir (Q1) + Work of pump (W) = heat available for heating (Q2) + losses.

 

Flunch stated that we are adding energy to the system using the pump. That obviously can't be it because a pump is worse at adding energy to the system than is resistance heating. I understand very well how much heat is present in a mass of anything and how it can be removed and taken elsewhere just by, like you said. I am painfully familiar with window air conditioners. I have two of them that I use and one that I'm not sure what to do with.

It takes work to reduce the pressure of your working fluid, in this case most likely R-134. It takes work to compress it again. This is where you would supposedly lose too much energy to use this cycle to convert ambient energy to useful energy. You also have losses due to friction between the fluid and the plumbing. Those who don't understand that may understand it more easily when you think of all friction as being due to collisions between molecules.

Yes, I can understand, and I think I'm repeating myself, taking energy from a larger reservoir and concentrating it into a smaller reservoir. It's sort of like using a 200 foot water wheel on a river at a fraction of a PSI at the bottom to develop 100 PSI in a column of water 200 feet high. This analogy is not exact, and none of the analogies that I have seen so far addresses the problem that it takes work to move the caloric content to a higher and more useful level. Flunch agrees that this is impossible to do at a net gain. The Wiki article literally says that a COP of 4 means 400 percent efficiency and that a resistance heater is 100 percent efficient.

The analogy of the water wheel means that you are using the energy from the river to concentrate the energy you receive from the river. That's from a large reservoir at low intensity to a small reservoir at high intensity. If I were trying to support a hypothetical device that would produce useful energy from ambient energy, I would use just such an analogy. I would think that at least some of the jeering section would point out all the things that I have pointed out, and of course, like most crackpots, I wouldn't have a telescope for them to refuse to look through. Some people seem unable to see it when it is right in front of them.

And yes, this is a lossy process just like any other, but the loss definitely doesn't come out of the energy we supply to the pump motor. If it did, we wouldn't be seeing COPs of 3 or 4. They wouldn't reach 1. The losses have to come out of the energy that we are concentrating. No one has yet in this thread given a mechanism for concentrating that energy without expending more energy than we get out of it. There is an actual mechanism for doing this, and I guess I'll go ahead and mention it. I believe that the actual mechanism is in the vaporization and condensation of the working fluid. This gives us a mechanism for sorting out hot from cold molecules, a way to create a difference in energy levels that makes ambient heat usable. There is a temperature of evaporation difference in the energy levels between a liquid at its boiling point and the vapor after it has boiled, even when the liquid and the vapor are at the same temperature. For water this number is very high, 510 calories per gram, more than five times as much energy as it took to get it up to that temperature. The existence of these droplets makes it possible for the heat picked up from the cold end to pump the working fluid by increasing the pressure by vaporizing the droplets. At the hot end, condensation of those droplets makes it easier to compress the working fluid, even though the cycle has to start with using energy to compress it.

This I believe is the missing link that I was looking for.

 

A big part of the problem is that you are looking at it from a typical high school level. At that stage of education they present you with a large number of loosely connected facts but don't do very much in the way of tying all those principles together into actual working systems . And that's why you keep talking about violating the laws of thermodynamics and "pushing heat uphill." Since you have those air conditioners you can actually FEEL one pumping heat outdoors. The other major problem is that you don't fully understand the refrigeration cycle - as we can see form several of your statements below. So that's where you should really be applying your efforts to try and learn.

One more thing here, Flunch is correct about adding energy to the system to operate the pump, you simply fail to understand what was meant. That added heat (power to drive the compressor and fans) is largely lost due to radiation and convection and little of it is delivered to heat the house. It's purpose and use is to collect and deliver the heat from it's source (outside air) to where you want it - inside the house. That energy contributes very little to the heat you are receiving.

That's almost totally incorrect. It requires NO energy input (work) to reduce the pressure of the working fluid! That happens when the liquid enters the evaporator. And as the liquid is evaporated and changed to a gas is precisely where it is absorbing (collecting) the heat which will later be released by compressing the gas into a liquid again. That does require energy to drive the compressor and is exactly where more heat is released from the phase change (gas to liquid) than is required to force the phase change. That is the very heart of the refrigeration process!!!

Once again Flunch is correct and you seem to have overlooked that I said the exact same thing. The article is correct about those numbers, But you just fail to understand the idea that the input power is ONLY being used to concentrate and move the heat. You cannot compare it to the way you would determine the efficiency of an engine - energy in the fuel compared to what's delivered to the wheels of a car. A refrigeration machine is NOT an engine And I believe that's where your greatest hang-up is. It's an entirely different kind of device. Repeating: it is only a device to collect, concentrate and move heat around - NOT an engine.

Careful! You're actually talking about yourself here.

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Incorrect again. The losses DO occur in the power we are supplying to run the compressor and fans. (You really do need to study refrigeration a lot more.)

You are finally getting a little closer. I've been trying to tell you all along that the "secret" lies in the expansion and compression of the working fluid. But it has no relation to "sorting out the hot and cold molecules" as in the story about Maxwell's demon. It's just very simple evaporation and condensation. Very, very basic stuff, really. Evaporation absorbs heat, condensation releases it. Again, that's the very heart of ANY refrigeration device - air conditioner, heat pump, household refrigerator, freezer, ice maker, etc. And once you really understand how those devices work, you'll be well on the way to seeing how a heat pump works.

You've actually made a little progress because you began by asserting it was MY claim that the things actually worked. So you've gained a little knowledge.

 

MetaKron, what you are talking about is called the "latent heat of vapourization" - the energy difference between the liquid and gas states of a fluid at the same temperature. You don't quite seem to have it yet but Light is right, you do seem to be making a little headway in your understanding of this cycle.

This statement shows your lack of understanding, though I admit I was being a little loose with my turbomachinery nomenclature. The compressor increases the pressure of the fluid in a typical heat pump - a direct input of energy to the fluid. This energy is added to the energy that was gained from the cold temperature reservoir (which is carried by the fluid in the form of the latent heat of vapourization and any increase in temperature realised).

Some of this total energy is released to the hot temperature reservoir (i.e. your house) when the fluid goes through the condensation process. The fluid goes through a further decrease in energy when it expands through a valve and returns back to the cold temperature reservoir. By this time the temperature is low enough for it to start absorbing heat again from the environment and the cycle continues.

I'm not sure you have a firm grasp on that so I thought it warranted a quick run-through.

 

OK, first, my English may not be clear enough even though I am at least third or fourth generation American and most of my ancestors were English speakers. Mostly I think we're talking past each other. I have never claimed to believe that the heat pump claim was to remove more heat from the cold-side reservoir than was there, even if it may have sounded like that. I just don't believe that strict interpretation of the 2nd law allows for what heat pumps do. So what if I don't get that completely, I'm not sure that anyone does. Even in the simplest of propositions, complications can exist. About all you and Light have told me is where the heat comes from, which I already know in great detail. What I don't think either of you understand is how that heat is pumped uphill at a net gain in usable heat over the amount of energy you supply to the pump.

I am quite aware of how refrigeration works. A fluid with just the right latent heat of vaporization makes refrigeration a lot more efficient in any given space because you can use that to sink and source more heat faster. Compress the fluid and it gets hot. Push that fluid through whatever heat exchanger is best, like the hot side of your air conditioner. It cools during that phase. It cools even more when it is allowed to expand, and the chilled fluid is then pumped through the cold side. There it gains heat. That hot stuff has to be compressed again to be able to reject heat when it goes through the hot side exchanger again. This scheme also will not work unless there is some kind of constriction where the fluid circulates from the hot side to the cold side else the compressor will not be able to maintain pressure against the hot side. In the simplest setup one compressor motor will both create the pressure against the hot side and the vacuum against the cold side. Yes, I realize that this goal can also be accomplished by using a narrower guage of tubing on the hot side. Also, I am talking about a very basic model for mechanical refrigeration.

I would bet that the heat pump scheme cannot work at all with a working fluid that does not exist as a liquid part of the time and a vapor part of the time. One funny thing is that when you compress a liquid like Freon (do I have to say R-134 to be politically correct?) some of it becomes droplets because you've raised its boiling point. The rest becomes hotter both because the droplets have released their energy and the fluid is compressed. On the other end, when the Freon expands, it becomes colder. Droplets form because the freon got colder, which is a mixed advantage and disadvantage because this reduces the pressure, making the gaseous portion even colder, but the droplets release heat, which makes things warmer again. We've lowered the boiling point of the Freon, so the temperature can drop further before droplets form.

I think that the latent heat of vaporization, crossing and re-crossing that threshold, causes an excursion that turns uphill into downhill. When the Freon condenses on the hot side, it removes some of itself from the vapor, which reduces the workload on the compressor while raising the temperature or at least increasing the amount of heat that can be removed from the system. The fluid portion also conducts heat out of the mix a lot faster when it is in contact with the walls of the tubing. The better the unit can handle the fluid that condenses, the better your unit is going to work. This is not as easy as it sounds. Mixed fluid and vapor going through a jet into the expansion phase can cause the flow to stutter. This can be bad for the compressor and the tubing and compromise efficiency.

As opposed to a window air conditioning unit that is expected to be more or less a quick and dirty design, a heat pump to work at all is going to have to take maximum advantage of this. Even not knowing the details, this means more parts, more weight, more controls, more know-how. So they are expensive and a useful one probably won't fit in your window. It certainly won't weigh just under 40 pounds unless much more expensive materials and parts are used. One thing that you learn by any real exposure to manufacturing processes is that it is fairly difficult to put "just one more small part" into a system. Also, things that are relatively simple for a bright tinkerer to do, like run the cold side through a reservoir of water heated by solar or other, are difficult to impossible for a manufacturer because they add a lot of complications and don't sell. Integrated off-the-shelf units are the craze, and even a manufacturer with a multi-million dollar budget works hard to scrimp on maintenance, so anything that needs much attention is out, even if paying two technicians full-time wages would save a million dollars on energy costs. It's also hard to find people who can maintain a plant like that.

If I sound like I don't understand things, a lot of it is because I can't download everything I know into a few short messages. Also, understanding the refrigeration cycle does not mean understanding how to get 400 watts of heat out of a device for a 100 watt input even if there is a massive source of heat at a low temperature to draw from. The latent heat of vaporization thing didn't occur to me until later in the conversation. It isn't in the Wiki article.

 

Even a condensor in the line adds to the cost and weight of the mechanism. I can see where effective cooling could be had without one. Ideally the Freon that passes through the hot side would condense to a liquid and be introduced to the cold side as a liquid and allowed to expand. You need the pressure to be lower than the hot side, and the expansion tends to raise the pressure, just as the condensation on the hot side tends to lower the pressure, which helps the compressor do its work, but also tends to eliminate the difference in pressure between the hot side and the cold side. That's a balancing act. A condensor makes it more efficient because it it a lot easier to push liquids than gases and the liquid carries a lot more energy per mass or volume, or a larger deficit in energy as seems to be the case here.

I don't seem to remember a lot of what I read about refrigeration, and it's fun to go back and try to figure it out on my own because I can generate ideas that often aren't included in the reading material. It helps me realize things like the idea that a condensor can be a variety of things and I have to figure out what it does to know the concept. The condensor in a refrigeration unit is also where the freon is kept when it is turned off. It takes time for as much of the liquid as will condense runs back into it.

This reminds me of these "made simple" books from a few decades ago. Do they have a new series by now? It was sort of like a "for idiots" series, but after you read them, you knew all of the details that fit the print. They broke down systems in component parts and explained how each worked in detail. The reader would then know how a three-phase motor, a rocket, a refrigeration unit, or whatever the device was worked, and they included technical and mathematical details.

 

Once again, you are making progress - and that's good.

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The difficulties you're having is not from a lack of information but result from not yet fully intergrating the information you already have. You are still laboring under a few (but important) misconceptions.

One minor thing I noticed in passing is that you aren't aware of window-sized heat pumps. I don't know where you live but they are VERY common in parts of the country in apartments and condos. The reason is that they provide both heating and cooling from the same unit and avois the complexities of providing furnaces in individual living quarters. It also saves the time and effort of installing electric resistance heaters along baseboards, though that is still quite popular too.

But since air conditioning is required anyway, you simply buy ONE unit, stick it in a window, plug it in and you immediately have both heating and coolilng. "Extra parts???" The only difference between just an air conditioner and a heat pump is a 4-way valve and a couple of short lengths of copper tubing.

Sure, heat of vaporization is the key to any refrigeration system!! The reason you didn't see it mentioned anywhere is because it is so elemental that all the writers assume that everyone already knows that. (It's about as basic a principle as you can find.)

The following two statements of yours clearly show that you still do not completely understand the refrigeration process even though you make every attempt to claim that you do:

"I would bet that the heat pump scheme cannot work at all with a working fluid that does not exist as a liquid part of the time and a vapor part of the time."

And, "On the other end, when the Freon expands, it becomes colder. Droplets form because the freon got colder, which is a mixed advantage and disadvantage because this reduces the pressure, making the gaseous portion even colder, but the droplets release heat, which makes things warmer again."

Of course it won't work without being a liquid at times and a vapor at other times. That IS what allows it to use the heat of vaporization. Unless there is that phase change, the device is useless.

Yes, as the freon expands it get colder (another basic principle) but NO droplets form in the evaporator where this expansion is taking place. It enters the evaporator already in a liquid state through an expansion valve or capillary tube (which is simply a very small diameter piece of tubing) and there it does nothing but evaporate - turns into a gas. There is NO condensation taking place which releases heat - none.

The only place condensation takes place is in the condenser (thus it's name) and that's all the way over on the other side of the process.

Seriously, once you get past these few little things you'll have a reasonably good understanding of the subject.

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Well, actually, I believe that a heat pump or refrigeration unit would work without the phase change, but the heat pump would show no gain over the efficiency of a heating coil. If it is all you have for some reason, it is possible to build a refrigerator that uses just a compressible gas. I think there are applications that make this a requirement, and of course there are the Hilsch vortex type cooling units.

If I insist that the heat pump violates or appears to violate the 2nd law, and that it sounds like a crackpot claim, this is not the same thing as insisting that results of actual tests do not show that it works. I can insist that theory shows that it can't work, but I give in to exhaustive, repeated, independent testing.

I was only vaguely aware of window units that could work as heat pumps also. I don't think that Walmart carries them but I know of a store that might. They have to be more expensive and more complex, if for no other reason than to pay for the development program. I guess it would also have to be a Fedder's and not a Goldpak. You can do things with a refrigeration unit that you can't get away with using a heat pump, like letting mixed vapor and liquid move through a poorly designed condensor. Since its function is gravity dependent and sensitive to vibration, it would be almost mandatory that a car's AC unit be able to tolerate that. It reduces efficiency, but it would still work.

The Wiki explanation is very sketchy and the heat of vaporization is a very basic and essential part of a good explanation.

 

Yeah, I can see that's your biggest hang-up. But it's only because you still don't completely understand it. There can never be a violation of the 2nd law.

The only problem is that you are thinking of it as a closed system with only a single source of energy - the electrical power. If that were true, it really would be a violation. But for some reason - known only to you - you cannot seem to understand that it uses that energy ONLY for the purpose of gathering additional energy.

And I thought you were getting so close...

 

There are almost as many ways to rephrase that as there are writers. I never claimed that the heat pump even appeared to violate the first law, which is the conservation law. It is a subset of the law of conservation of matter and energy which states that matter and energy cannot be created or destroyed, only converted from one form to another.

Here are some versions:

Energy spontaneously tends to flow only from being concentrated in one place
to becoming diffused or dispersed and spread out.

I don't think much of this Wiki article but here is a quote. This is pretty much how I have understood the second law:

A system operating in a cycle cannot produce a positive heat flow from a colder body to a hotter body (Clausius)

These two statements imply to me that according to this law it takes more than 100 watts of energy to pump 100 watts of heat uphill. I'm cool with getting the rest of the watts that it takes out of the cold side reservoir.