Watts to Degrees Centigrade?????

Discussion in 'Homework Help' started by HighVoltage!, Nov 5, 2015.

  1. HighVoltage!

    Thread Starter Member

    Apr 28, 2014
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    Does anyone know how to mathematically convert Watts(heat) to Degrees Centigrade through a certain time frame/mass ?
     
    Last edited: Nov 6, 2015
  2. WBahn

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    Mar 31, 2012
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    Sure. Just change the 'W' at the end to '°C' and you are done.

    Oh, mathematically.

    Just multiply the value in watts by "1 °C/W".

    This is like asking someone how to mathematically convert gallons to pounds. At best you are relying on people being able to use their crystal balls to read your mind, at worst the question itself is nonsensical.

    Try to ask your question again, taking the time to tell us what the hell you are trying to do.
     
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  3. OBW0549

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    Mar 2, 2015
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    I forget the exact formula, but if I'm not mistaken it's the same one used to convert apples to oranges.
     
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  4. DerStrom8

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    Feb 20, 2011
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    [​IMG]
     
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  5. bertus

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    HighVoltage! and panic mode like this.
  6. WBahn

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    What an aptly named website for this question! :D
     
  7. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    ESP = Elliott Sound Products, not quite what you were thinking WBahn. It certainly coincidental. Still, it's a very good website.
     
  8. Papabravo

    Expert

    Feb 24, 2006
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    You're not suggesting that Rod change his name, due to the unfortunate association??
     
  9. WBahn

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    I know -- I went to the website.

    But, given the mind reading needed to answer the TS's question (not very strong mind reading skills, mind you), it's a particularly appropriate site name.
     
  10. WBahn

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    What could possibly imply that I am suggesting any such thing?
     
  11. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    So, to get started, if you have power (watts), and you need temperature, you must be heating something. Do you know the mass and the material that you are heating? You can then look up the "specific heat" of the material you are heating. The units of Specific Heat is (J/(g*C)). Then you need the time that the heat is applied to the material. This all assumes that 100% of the energy is transferred to the material that is heated.

    Watts / time= Joules

    Joules / ((specific heat) * (mass)) = temp change (C)
     
  12. Papabravo

    Expert

    Feb 24, 2006
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    The desire to exert a slight tug on your leg.
     
  13. WBahn

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    Mar 31, 2012
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    Consider it tugged. (where tugged rhymes with rugged) :D
     
  14. HighVoltage!

    Thread Starter Member

    Apr 28, 2014
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    Im glad I made you guys smile a bit :rolleyes: :). I am heating an aluminum slug via current induction...Therefore, I am trying to generate a formula as to what will be the final "stable" temperature in a "stable" ambient at a set current.
     
  15. DerStrom8

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    Feb 20, 2011
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    Unfortunately there's no straight answer. You really need to provide more information. The temperature is highly dependent on the physical size and shape of the slug, the type of aluminum, distance from the coil, and even is affected by ambient temperature, humidity, and how high above sea level you are. Your best option would be to throw a thermocouple on the slug to actually measure the temperature.
     
  16. HighVoltage!

    Thread Starter Member

    Apr 28, 2014
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    Well at the moment I am using a thermocouple...But I wanted to generate formulas if possible
     
  17. HighVoltage!

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    Apr 28, 2014
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    will resistivity of the metal be suffice?
     
  18. DerStrom8

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    Short answer? No.
     
  19. WBahn

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    What it comes down to is the ability to come up with a heat balance equation.

    As the slug heats, it gives off more heat to its surroundings. It will do this through a number of mechanisms such as radiation and conduction. Which will dominate depends on your setup. Also, which will dominate will change with temperature. But you should be able to measure this by heating the slug up to a high temperature and then removing power from the system and recording it's temperature as a function of time while it cools down. The rate at which it cools at a particular temperature (assuming a constant heat capacity) is proportional to the rate at which heat is dissipated at that temperature.

    Now you have the other side of the equation. You know how much power you are putting in, but the question is what fraction of that is actually getting into the slug and, more importantly, is that efficiency constant or is it a strong function of temperature.

    If you can make the first measurement (the cool down data) then you can start with the assumption that the thermal coupling efficiency of your system is constant and measure the stable temperature at one operating point and compute a coupling efficiency at that point. Then pick another operating point well away from the first and use the data to predict the equilibrium temperature and then measure what it actually is. If the results are close enough for your purposes, then you are done. If not, then take some data points over the operating range and do some curve fitting. You will probably come out with curves that can be pretty reasonably fit using a low-order polynomial.
     
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