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I remember my grandmother telling me about a fridge she used to have that burned kerosene to cool down. I’ve researched the topic, and now sort of understand how it works, and it still blows me away.
For anyone out there with a deep understanding of the topic of ammonia / hydrogen / water refrigeration,
perhaps you could shoot down my idea.
Would it be possible to use the exhaust heat from an internal combustion engine to provide the energy for an air conditioner based on the same principal as granny’s fridge? If so, we could have plentiful air conditioning at no additional energy cost.
Lehman's
http://www.gasrefrigerators.com
[UnaBubba, Oct 17 2004]
experiment
http://www.metrans....ort/99-19_Final.htm
<URL fixed by admin> "A sorption compression system can utilize the exhaust heat or the heat absorbed by the cooling water." [Fussass, Oct 17 2004]
[link]
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This one is over my head, from a practical view. It seems to me that, in theory, a heat exchanger placed around, say, the lower exhaust manifolds should be able to harvest otherwise wasted energy. How that gets used to drive an AC unit, I don't know. Steam turbine? |
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[Bris], the basic principle is to create cooling through evaporation, like any refrigerative system. In the case of a kerosene fridge, an ammonia mixture permanently sealed inside the cooling unit is heated by a gas burner, which causes it to circulate inside the unit before it evaporates and creates a cooling effect. The liquid circulation of the unit is purely gravitational, so there are no moving parts to wear out, which means fewer repairs. The continuous heating, evaporating, and condensing is a never-ending cycle, so long as there is an energy source to promote evaporation. |
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The system is very low maintenance as gas refrigerators do not have a compressor. Their operation is totally silent. |
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The ammonia is heated down low in the system and cools rapidly when it is allowed to evaporate higher up, in an expansion chamber. It condenses to a liquid at this point, and is passed through the cooling chamber where it absorbs heat from inside the fridge, then circulates to the outside and passes through a heat exchanger. Using a fan to circulate air over the heat exchanger allows the heat to be carried away more efficiently. |
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It would probably work quite well in cars, though there is a steady supply of rotational force available, and manufacturers use that to run a compressor, which serves the same function as the expansion/condensation chamber. |
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This is a fabulous idea - the ammonia crystals left over from when then engine last stopped could be used for a quick a/c startup. No more hot air blowing out of the vents on startup. |
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(1) the minimum economic size of these systems is quite large |
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(2) you might need supplemental firing to boost the cooling power at certain times |
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(3) as [UB] said, other than the heat source, there are few synergies with the existing car systems |
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Any proposed solution [TIB]? |
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Perhaps the system could serve a dual purpose, as an intercooler, to cool intake air and allow more efficient running of the engine. |
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That would go further to justifying the added cost and complexity, without penalising performance in the way a supercharger would. |
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[TIB], it might be an idea to remove the words "free energy" from the title. In this house we observe the laws of thermodynamics. |
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"Waste Heat Recycling A/C For Cars" might be a better choice. |
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[UnaBubba] Yeah, sorry about the free energy reference. I should have said something more along the lines of energy recovery like you suggest.
Amazing idea – the supercharger!! When you’re not using the AC to it’s full capacity, use the remaining heat extracting potential to cool the incoming air. Maybe this idea could be applied to the power station problem too! Use the power station exhaust heat to cool incoming air? |
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[FloridaManatee] I wonder, with today’s technology, would it be possible to engineer one of these units to be much smaller and more efficient than it’s predecessors? Do you know of any company that has a modern version of this old idea?
If heat is needed when the engine is still cold, electricity could be used to heat the refrigerant solution until the engine warms up.
I agree, there are few synergies with existing cars systems. I chose exhaust heat because of the temperature differential, but perhaps the engine coolant would suffice. In that case, the AC could be integrated with the radiator, simplifying things a little. |
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There's a US company, Lehman's (I think), that manufactures LPG fridges for motor homes and areas where mains power is unavailable or undesirable. They've probably plumbed the reasonable limits of ammonia-cycle refrigerative sytems. |
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Small propane powered ones are used in campers, so they can be miniaturized. Big ones have been used with geothermal heat the same temperature as radiator coolant. There is also a lithium bromide and water cycle that would fix any toxicity issue. After the sad fate of all the other waste heat ideas this one might stand.
Here is a link to some people trying to do it with carbon adsorption. I think they proved that they could make it too big and expensive and ran out of funds. |
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You know, sometimes I just do not understand why people fishbone some ideas. |
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Fussass, that link ain't never gonna work like that. |
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Link fixed and it's a good read. The "Introduction" and "Principles of Adsorption" sections explain a lot that I didn't know about. |
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I like. A car's compressor is an expensive, leaky, noisy, fuel-hogging piece of crap that has to live in a terrible environment and be happy about it, no matter how well it's designed. Most of your coolant that permeates out of the system goes through the dynamic compressor seal, and so a system that abandons the whole thing would be a great advantage in terms of extending the useful life of the car. However, I doubt very highly that there will be enough capacity to cool the entire passenger compartment effectively. Nice as a hybrid system though. |
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Great, and whenever you really need the A/C, you have a
lot of heat hitting the car, so why not trap it as well and
add it to the heat from the exhaust? |
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It would probably do OK, cooling the whole car, [RF]. I'm not sure what the specific capacity of a car AC vs a kerosene fridge might be, but our old kero freezer used to get cold enough to make ice cream, and it was about 600 litres. |
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[TIB, Sep7, 2003] i am working in captive power plant & in advanced stage of designing comprehensive waste heat recovery systems to run CHP (Combined Heat & Power) systems. it would mean Kalina cycle/ ORC based power generator coupled with a_sorption chillers. there would be utilization of all possible heat sources, to name just one - heat recovery from large capacity step down transformer cooling oil.
as far as application to car or any automobile is concerned, just think about the significant increase in weight to be carried (the systems are bulky) which would increase fuel consumption. |
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Here's why it won't work: There has to be a minimum temperature difference between the condenser and the absorber or the system will stall. I had one of these fridges in my van, running on LPG, and if I parked in the sun, the fridge would quit after an hour or so. Nothing would coax it back into operation except allowing the whole thing to cool down for a couple of hours. Even without this problem, you have to wait an hour or so after starting the system before you get any significant cooling from it. By then, you're probably already where you were going. |
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OK, so it won't really be practical for car use, but plumbing exhaust heat through the "generator" portion of the sorbtion (sp) cycle cooling system of an RV might be useful to keep the 'fridge cold while on the road. (+) |
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