Isolated cold hole

[VincentG]

Tom, thanks for at least understanding my proposal. I've questioned the conversion of heat to work, but if it is converted than it should reduce the load on the evaporator.

[Fool]

Please give us a sketch, and a block heat flow diagram.

[Tom Booth]

You don't seem to comprehend (as usual) that between the hot plate at room temperature 80° or whatever, and the cold plate at the evaporator, the heat from the 80° side is being taken away by being CONVERTED to work.

How much is an 80 degree hot plate going to cool an 80 degree room? Zero. It takes a temperature difference.

I think you need to study up on how a Stirling engine operates, or get one and observe. You see, there is this thing inside the engine that takes COLD air and sucks that air back and forth across the HEAT EXCHANGER. You do, presumably, understand what the purpose and function of a heat exchanger is right?

This happens intermittently.

The "hot plate" is near 80° room temperature. It gets cooled by a blast of cold air that heats the air (working fluid) causing it to expand and do work. In the process "work" is produced and the gas temperature drops back down to the cold temperature.

The "hot" heat exchanger plate is composed of very thin metal, so as it is in contact with the warm air inside the room it heats back up rapidly ready for another blast of cold air.

How much is a temperature difference going to reduce power converted and efficiency? The room will not be cooled as fast as long as the hot plate is above the temperature of the cooler evaporator.

The "hot plate" is heated by the room when covered from the inside by the insulating displacer.

It is cooled when the displacer moves driving cold air across it from the inside.

Then the displacer returns so the hot plate can absorb more heat.

Since the engine is doing most of the actual cooling by converting heat into work, the air conditioner has less work to do maintaining the evaporator at a cold temperature.

You would have a similar situation on the outside. But perhaps Vincent is right and there wouldn't be enough heat left to make it worthwhile having a second engine outside. I guess that would depend on the heat generated from inside the building and the efficiency of the engine and refrigeration system.

There could also be an issue if the system is very effective and only needs to run occasionally. Getting a Stirling engine to start up repeatedly when needed.

Lots of little details to work out if one were to get serious about such a thing but nothing insurmountable, I don't think.

However, designing and building a truly integrated air conditioning system + Stirling engine(s) is no small undertaking.

[VincentG]

Please give us a sketch, and a block heat flow diagram.

I'll have some time after the weekend.

[Fool]

VincentG, thanks.

Tom,
Heat transfer depends on area thickness R-value and temperature difference.

If a 30 F cooler has a specific area it will absorb heat from the 80 F room at at a specific rate.

If that area is covered by a Stirling cold plate it will be colder than the 80 degree room. Heat transfer between the two will be less. Okay, maybe the same amount as the work done. Cooler more efficient.

The area will also be blocked by the engines hot plate. That hot plate will be a lot warmer than the coolers 30 F. The hot plate will absorb way less heat per area than the cooler. The cooler area will need to be enlarged a lot for the same amount of cooling effect. The hot plate will not be at 80 F nor 30 F, so it will need a lot larger area. The efficiency drop will reduce the effect you desire too.

[Tom Booth]

VincentG, thanks.

Tom,
Heat transfer depends on area thickness R-value and temperature difference.

If a 30 F cooler has a specific area it will absorb heat from the 80 F room at at a specific rate.

If that area is covered by a Stirling cold plate it will be colder than the 80 degree room. Heat transfer between the two will be less. Okay, maybe the same amount as the work done. Cooler more efficient.

The area will also be blocked by the engines hot plate. That hot plate will be a lot warmer than the coolers 30 F. The hot plate will absorb way less heat per area than the cooler. The cooler area will need to be enlarged a lot for the same amount of cooling effect. The hot plate will not be at 80 F nor 30 F, so it will need a lot larger area. The efficiency drop will reduce the effect you desire too.

You could simply have a heat pump inside the room creating the ∆T for the Stirling engine.

The Stirling engine can then use that ∆T to convert the heat from the condenser to work, thereby removing heat from the room.

No outside venting required.

[Fool]

I don't need to comment on that idea, because you are going to assemble one from available parts and show us how effective that is. Right?

[Tom Booth]

I don't need to comment on that idea, because you are going to assemble one from available parts and show us how effective that is. Right?

Building an integrated Stirling engine + heat pump is not a matter of simply putting parts together.

The Stirling engine heat exchangers need to be fully integrated with the heat pump heat exchangers, really, the condenser is the Stirling engine hot side and the evaporator the Stirling cold side, to put it simply.

So everything needs to be designed and built from the ground up by someone competent in both Stirling engine construction as well as heat pump/refrigeration design and construction

Competence in either one of those is a rarity. Having full competence in both is virtually unheard of, aside from financial and time constraints.

Nevertheless, I'll be giving it a try, with no help or financial support of any kind, thanks to the work of the "Carnot Limit" naysayers and "free energy" suppressive, such as yourself over the past century or more.

And if I'm successful, not much chance of it ever seeing the light of day, judging by the treatment inflicted on others who produced similar inventions, only to have the prototype confiscated or "classified" and themselves jailed or otherwise disposed of

[Fool]

Yes. I agree. Proof of concept can be built a little more simply, maybe.

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[VincentG]

If a 30 F cooler has a specific area it will absorb heat from the 80 F room at at a specific rate.

If that area is covered by a Stirling cold plate it will be colder than the 80 degree room. Heat transfer between the two will be less. Okay, maybe the same amount as the work done. Cooler more efficient.

The area will also be blocked by the engines hot plate. That hot plate will be a lot warmer than the coolers 30 F. The hot plate will absorb way less heat per area than the cooler. The cooler area will need to be enlarged a lot for the same amount of cooling effect. The hot plate will not be at 80 F nor 30 F, so it will need a lot larger area. The efficiency drop will reduce the effect you desire too.

Still have not got around to a block diagram, but I realize you get the idea from this post. The only confusion is that the hot plate only needs to stay at tmax as it is tasked with heating up the cold air after it is compressed in the tmin space of the cold plate.

The tmax of the room is sinking to the tmin of the cold plate, but along the way there is heat from the room that is being converted to work, which should reduce the overall cooling load on the covered part of the evaporator(cold plate).

Theoretical negative impact on the overall cooling system is 0, while theoretical reduction in cooling load with positive work output is possible.

[Fool]

.

The negative effect on the cooling rate, if there is a Stirling Engine between the AC unit and the rooms hot air, will be significant and large.

.

[VincentG]

Seemingly obviously, only a small portion of the evaporator would be obscured by the engine so that at worst the engine acts like a portion of the evaporator is blocked by insulation.

[Fool]

.

What percentage of evaporator blockage would provide a worthy amount of power?

.

[Tom Booth]

Often, with ordinary household heat pumps there is an evaporator/cooler inside and an evaporator/cooler outside (roles are reversible summer/winter.)

So you have a situation where there is a stretch of tubing carrying the refrigerant to the indoor or outdoor heat exchanger.

This extra length of tubing gets just as hot or cold as the tubing looping through the heat exchangers, if not hotter or colder, and makes no appreciable difference to the functioning of the heat pump or heat exchangers.

Routing additional tubing through a Stirling engine would make no difference either, other than being an additional assistance to the process, using heat before it goes to the condenser to be taken away anyway.
Likewise the engine would remove heat before the evaporator by converting it to work, therefore assisting cooling as well