Heating elements

Discussion in 'Electronics & Electrics' started by alvarez, Sep 18, 2006.

  1. alvarez

    alvarez Member

    Jun 25, 2006
    Geelong 3218
    Does anyone know of any heating elements that could get hot enough to boil a smal amount of water but dont draw a massive ammount of power i.e from a pc power supply under load with a basic pc,

    Would the hot side of peltiers get hot enough?
    Also i cant have some 240 volt thing obviously something i can wire up my self
  2. Goth

    Goth Grumpy Member

    Jun 22, 2002
    You can get 12V immersion heaters and stuff like that that can boil water, designed for car use.

    I'd get something like that and adapt it. Not sure what the power consumption would be like however.
  3. Butcher9_9

    Butcher9_9 Member

    Aug 5, 2006
    Perth , St James
    well a kettle uses up to 2k watts to heat 2 litres so i would say about 2 watts per mL but that is only if it has good insulating
  4. blakeyboysmith

    blakeyboysmith Member

    Dec 11, 2004
    isn't heat capacity of water something like 4.2j per gram per degree from memory...

    so to raise it from 25-100 degrees means you need 315 joules per gram of water... or 0.0875 watt-hour per gram.
    now you also have heat losses in the system and also the issue of a phase change (liquid to gas) that mean extra energy... but as a first approximation this may help you...

    so really you need to decide how much water....

    i'm guessing this is for a coffee or something so maybe like 400mls or something... as an estimate. 35watt-hour... now i can't quite remeber the way watt-hours work but i think that means at 12 volts at 3 amps (assuming 100% efficency realisitcally 50-60% is more likely)... which doesn't seem enough to me.
  5. LethalCorpse

    LethalCorpse Member

    Mar 23, 2003
    Cambridge, Massachusetts
    The watt-hours is a measure of how long it will take to boil at a given power, so (neglecting heat losses, which won't be insignificant) it will take one hour to boil that 400g of water, or half an hour at 75W, or fifteen minutes at 150W, or 7.5 minutes at 300W. You will lose rather a high percentage of the heat to atmosphere, meaning it will take longer to boil, or not boil at all if the heat losses at any point in the boiling period outstrip the heat applied. I'd consider 300W to be the minimum that could boil that amount of water in anything approaching a reasonable time.

    You'd be far better off to use the element from a kettle, or indeed, the whole kettle. If you want this to be PC controlled, look for some of the mods people have done to run pumps in their PCs for water cooling. It'd be very easy to build a PC controlled relay with a 240V output. If not, you can buy a kit from Jaycar that will do it for you.
  6. OCMunkee

    OCMunkee Member

    Jun 28, 2004
    Melbourne, VIC

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