Great Idea but the savings I think are flawed

Discussion in 'NZ Computing' started by Tony, Jul 22, 2005.

  1. Tony

    Tony Guest

    Really cool invention brings teens awards

    They seem to think that if it runs off the Battery then no extra Petrol is

    "Today, the young inventors say, U.S. drivers use about 7.9 billion gallons of
    fuel each year to run their air-conditioners, which draw power from the
    engine. By adopting their contraption - which taps into the electrical system,
    using fans to blow hot air through five Peltier chips and then releasing cold
    air - they say the country stands to save 3.9 billion gallons of fuel
    annually, or about $10 billion based on current gas prices. "

    May be the Peltier and fans are more efficient than the normal Air Con pump,
    plus the saving of not using Freon that often has to be replaced..
    Tony, Jul 22, 2005
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  2. Tony

    thing2 Guest

    The peltier system is a heat pipe system, it holds a change of state
    refrigerent charge.

    Ive not kept up with engineering advancements as I am not in IT but,

    Compressing a superheated gas into an even more superheated gas and then
    cooling it is energy intensive so in-efficient. Internally the same fan
    would be used as at present so no savings there.

    The big savings would be negating the need for a compressor running off
    the engine, counterbalanced by an external fan to disapate the waste
    heat. peltier stuff is good, but I dont think it is efficent for its
    size, so the heat exchanger might turn out to be the size of say the car
    roof. Imagine a 2 metre square heat exchanger on the roof......its
    weight, and cost....drag factor......ho hum......


    thing2, Jul 22, 2005
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  3. You can't superheat a gas, because it's already a gas.
    Lawrence D'Oliveiro, Jul 22, 2005
  4. Tony

    Tony Guest

    You did not look at the Link..?
    Tony, Jul 22, 2005
  5. Tony

    thingy Guest can.

    We are breathing one now.

    Its an enginering/thermodynamics term.

    Superheated describes any substance in its gaseous state where its
    temperature is above its boiling point temperature at that pressure.

    So at sea level (1013mba) if steam is at 104 Deg C it has 4 degrees
    superheat. At 104 Deg C is behaves as a gas.

    There is a huge transfer of energy in a change of state, ie liquid to
    gas but no temperature change, this is how air con etc works so well for
    its small size.

    Superheat is always given to ensure there are no droplets of liquid
    carried through to the compressor, you cannot compress a liquid, so
    you'd blow the compressor.

    Here endith the lesson.


    thingy, Jul 22, 2005
  6. Tony

    thingy Guest

    Yes briefly.

    A few pics does not give enough info to show they had a scientific test bed.


    thingy, Jul 22, 2005
  7. No, it describes the substance in the phase it should have _below_ the
    phase-transition temperature. So superheated water is water heated to
    above its boiling point (100?C at sea level) which is still liquid. Once
    it boils, it's not superheated any more.
    Lawrence D'Oliveiro, Jul 23, 2005
  8. Here's what the OED says:

    superheated /su:p<schwa>"hi:tId, sju:-/ ppl a.M19. [f. as prec. +
    1 Of steam or vapour: heated above its temperature of saturation. Also
    more widely, heated above the temperature of a phase transition without
    the change of phase occurring. M19.
    2 gen. Excessively heated or hot. M19.

    << end quote

    Next phase transition after gas would be plasma, after a fashion ?!?

    But there is also such a term as superheated steam that is in common use
    to describe steam considerably hotter'n 100C which has nothing whatever
    to do with change of state or saturation. This is the stuff that rips
    the meat off your bones in nuclear reactor and ship engine room


    Regardless of all that, to go back to the original article referenced,
    this is supposed to save petrol exactly how? Like, the electricity in
    the car is free and comes like mana from heaven unlike the energy that
    drives the AC compressor?
    Or does it have to be generated in a lossy operation by burning petrol?
    Maybe Mormon cars are different, who knows ...

    The technology gets rid of freon? I haven't been able to get freon for
    my air conditioning for years and years, had to go through a very costly
    conversion some 5-6 years ago when the old Volvo had lost its freon ...
    Then again, thins are likely to be environmentally backwards in the good
    ole US of A.

    From what I can gather, using peltier chips/cells adds a huge energy
    demand to the process of carrying away heat, and I'd like to see the
    figures how this would be more efficient than the old fashioned way.

    Peter Huebner, Jul 23, 2005
  9. Tony

    ~misfit~ Guest

    I was under the impression that steam isn't a gas, rather a vapour. I'm not
    sure if there's a gaseous state for water (H2O) or whether that much heat
    breaks down the molecular bonds and it becomes oxygen and hydrogen. I did
    study 6th form chemistry but didn't get UE in it. Mainly due to a crap
    teacher who made it about as interesting as watching paint dry. I ceased to
    listen to him before long and didn't sit the exam.
    ~misfit~, Jul 23, 2005
  10. Water is the 'odd man out'. Water _should_ be gaseous at room
    temperature going on molecular weight (to demonstrate, look at methane
    or carbon dioxide, both much heavier and yet they are gasses) - but
    water isn't because of that weird molecular shape that makes it an
    electrical dipole which results in its aggregate states being different
    from what they should be.
    In fact, water in its liquid state is so incredibly densely packed,
    molecule wise, that it's actually larger in its solid state. Only
    substance known to man ... a.f.a.i.k.

    Your use of vapour confused me at first (don't forget, English is my 4th
    language risen to first <g>) so the old OED got a workout again:

    1 Matter in the form of a tenuous fluid, either as a gas or as a
    suspension of minute droplets, esp. as produced by the action of heat on
    moisture. LME.
    2 A substance in the form of a gas or of a suspension of minute
    droplets; spec. a fluid that fills a space like a gas but, being below
    its critical temperature, can be liquefied by pressure alone. Also
    loosely (chiefly poet.), smoke; a smoky substance emitted from burning
    material. LME. <<< end quote

    Ah, that explains it. I had thought vapour was a gas below its critical
    temp that had liquefied into suspended droplets - and I am spot on in
    one of the ways it's used after all. Vindication first thing after
    breakfast feels soo good <grin> (Yeah, I'm having breakfast after 12
    So, h2o at 105 degrees is definitely beyond vapour ...

    And you're right, there is a temp where molecular gasses break down into
    their component gasses. Quite different between different gasses I am
    Plasma is, where the atoms break up into their components ... somewhere
    in excess of 5000 degrees i.i.r.c.

    cheers, -P.
    Peter Huebner, Jul 24, 2005
  11. Tony

    ~misfit~ Guest


    That clears that up then. Hope you enjoyed your breakfast. I usually skip it
    and go straight onto lunch. ;-)
    ~misfit~, Jul 24, 2005
  12. Two meanings of steam:
    (1) Water in the gaseous state (usual technical meaning)
    (2) Those visible clouds you see coming out of a boiling kettle or other
    cooking vessel in the kitchen.

    (1) is very definitely a gas. (2) contains droplets of water
    recondensing after the steam (meaning (1)) hits the colder air. Steam
    (meaning (1)) is invisible, and if you look closely (not _too_
    closely--be careful!) at the spout of a kettle, you can see a gap
    between the spout and the point where the "steam" (meaning (2)) becomes
    visible. That gap is filled with steam (meaning (1)) which hasn't
    condensed yet, and which can scald you--hence the warning to be careful.
    Lawrence D¹Oliveiro, Jul 24, 2005
  13. Tony

    thing2 Guest

    Been there seen that, a leak produces an invisibale supersonic jet of
    gas, a really nasty way to go.

    Though better than having the entire valve blow and filling the engine
    compartment with steam, then you get 100% burns (lungs as well) if you
    are unlucky it takes a few days to die.


    thing2, Jul 25, 2005
  14. Tony

    thing2 Guest

    Not within the context of this thread.

    1) To heat excessively; overheat.
    2) To heat (steam or other vapor not in contact with its own liquid)
    beyond its saturation point at a given pressure.
    3) To heat (a liquid) above its boiling point without causing vaporization.

    The first two are the the most common terms and the 2nd one usually used
    in engineering and heat transfer this is the relevent one to the thread.

    Off hand I'm not even sure 3) is practically possible.


    thing2, Jul 25, 2005
  15. Tony

    thing2 Guest

    ~misfit~ wrote:

    Steam at saturation temperature (at its boiling point for that pressure)
    is a vapour, once it has superheated it behaves like a gas.


    thing2, Jul 25, 2005
  16. Oh, it most certainly is possible. Just for example, many owners of
    microwave ovens have encountered it, sometimes to unfortunate effect.
    Lawrence D'Oliveiro, Jul 25, 2005
  17. (Bruce Sinclair)
    It's also the only technically correct meaning
    Lawrence D¹Oliveiro, Jul 25, 2005
  18. Yes and no. I cook a lot with pressure cookers. Initially you get
    vaporization, but then the boiling point of the water goes up to around
    116-120 degrees once it's under pressure and it stops evaporating at
    that point. So, say you've started with 1.5 cups of water to begin with,
    after the 4 l pot is up to working pressure you still have about half
    that as liquid and it stays that way, ~superheated~.

    Peter Huebner, Jul 25, 2005
  19. That's not superheated, since the pressure cooker has raised the boiling
    point. Superheating only happens when the temperature of the liquid
    rises _above_ the boiling point, and it stays liquid
    Lawrence D¹Oliveiro, Jul 25, 2005
  20. Tony

    ~misfit~ Guest

    I remember my physics teacher telling me something about an energy gradient
    or jump (not his words) where, to raise H²O 1°C from 99° to 100° takes x
    amount of energy to go from 100° to 101° takes something like 10 times x.
    Therefore steam condensing gives of relatively massive amounts of energy.

    Or something.
    ~misfit~, Jul 25, 2005
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