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Peltier or stirling fan?

  1. Aug 16, 2015 #1

    sophiecentaur

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    I am having a wood burning stove installed soon. I am wondering which would be better, to put on the top and aid room circulation, an electric fan, powered from a Peltier junction or one using a Stirling Engine. Does anyone have any ideas or experience about this? I wouldn't expect 'efficiency' figures as they would be pretty speculative, I'm sure.
     
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  3. Aug 16, 2015 #2

    Bystander

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    Fragile, in my experience.
    Don't have a clue.

    Have you considered convection driven "mobiles?"
     
  4. Aug 16, 2015 #3

    sophiecentaur

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    Hmmm. Thanks for the answer. I wondered about how the Peltier would stand up to any abuse - but then, it is supposed just to sit on the top of the stove and help circulate the air; never to be moved (except for the weekly dusting!!) The Stirling would be much more sexy but I wonder about the moving parts wearing out. And it would rattle a bit - in competition with our pendulum clock.
    "Mobiles"? But the idea is to make the air circulate more and not to use the existing convection.
    I would have thought that vertical flutes along the vertical run of cast iron flue (exposed in the room) could encourage convection actually in the room but the air motion would only be in the same direction as that from the hot stove body.
    I'd really like to hear from someone who has one and I can't believe I'm the only PF member with an interest in quirky mechanisms. ?????????????
     
  5. Aug 16, 2015 #4

    OmCheeto

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    I've been interested in this for quite a few years, but haven't made the plunge yet to try either one.
    From my googling, it appears the Vulcan Fans(sterling) are no longer in production, though they are for sale via Amazon. But then again, I'm having trouble tracking down the vendor that Amazon says is supplying them: Brightfusion Ltd.
    My suspicion is that the Peltier junction types are more durable.

    As a third option, I've been thinking of making a DIY natural convection system, similar to this:
    Boilers circulation systems: natural circulation and forced circulation
    I purchased a 12vdc muffin fan a couple of months ago, and already have a raw Peltier chip, so all I need now is a boiler, some tubing, and radiator/condenser.
    Though, I'm hoping it will work without anything boiling, as I've heard that in the olden days, boilers used to explode!

    Two reasons I came up with this idea:
    1. I had a very derelict automobile a few years back, which had a nasty overheating problem, which I counteracted by activating the air conditioning system, which electrically opened the coolant system valve, and my displayed engine temperature, dropped like a rock. I had removed the belt that powered the AC unit compressor soon after I purchased the vehicle, as it never gets hot where I live. (Well, up until this year. You can ask LisaB about this weather......)
    2. One of the US Naval submarines was supposedly designed with a natural circulation reactor coolant system, so the idea has intrigued me for decades.

    I can neither confirm, nor deny, that such a system exists, of course.

    ps. Although Benjamin Franklin seemed very smart, the wood stove that bears his name, was designed at a time when there was way too much wood laying around.
    pss. Why do people ask questions about wood stoves in the middle of summer, and solar panel questions in the middle of winter?
     
  6. Aug 16, 2015 #5

    sophiecentaur

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    The problem with the Vulcan is that they probably have had to take a nicely engineered engine and cut corners that have still not brought the price down to compete with the Peltier version.
    What sort of natural convection system could you make that wouldn't involve loads of metal trunking all around the room?
    I had a nasty overheating problem, once, that was solved instantly by putting in a new radiator.

    My stove will be Wood burning and not nuclear. Or was my OP unclear / nuclear ? lol

    HAHA. If you want an installation done then you ask for it out of season. Our guy is starting in just a couple of weeks time. Ask for it in winter and you may have to wait Until Spring.
     
  7. Aug 16, 2015 #6

    OmCheeto

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    Nuclear reactor cores actually run at very wood stoveish temperatures, as I recall. ≈500°F
    But I'm mainly familiar with pressurized water reactors.
    You can Astronuc if this is still true. It's been quite a while.
    Ok. That makes sense.
     
  8. Aug 16, 2015 #7

    sophiecentaur

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    I think that the Peltier probably will be what I go for. A much simpler mechanical arrangement. A motor should run and run and the Peltier gubbins is all in a sturdy block.
     
  9. Sep 27, 2015 #8

    sophiecentaur

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    OK.
    Now I have my wood burner. It's great. I plan to buy a Peltier Fan but some of them seem to specify a maximum safe stovetop temperature. Until I buy a thermometer and observe the temperatures over a whole season, I won't know how my stove performs. I came across an Italian model that claims to have a protection system????? It can hardly lift itself off the stove (can it?) so I guess it can only involve a warning buzzer which wouldn't help if we were outside the house.
    Anyway, I am now after opinions as to whether the stovetop temperature is a serious issue.
    Also, there is a "Smart Fan" advertised that has a supplementary fan which blows across the cool sink. They claim that this improves the efficiency by cooling the Peltier cold sink but how would this necessarily make an improvement as the main fan is doing exactly the same thing. It sounds a flashy idea but can it really be doing anything significant?
    Also, I assume that the cheap versions must use brush motors but a brushless motor could last longer (if the electronics can handle the high temperatures). Is commutator / brush wear the life limiting factor?
    Sorry if this reads like a Mumsnet posting but there is some Physics in there too!
     
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