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  1. #1
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    Red face Temperature Gained?



    OK guys (gals?),

    Please feel free to laugh at me for this one, it is late, my brain is mush and I can't find my trusted rule of thumb book...


    What will the temperature rise be in 1m2 of air if 1 watt of heat is added to it for 1 hour?
    (Assuming no losses or other heat transfers occur and that we start with dry air at 20ºC)


    I will now go and collect my free bus pass, get my slippers on and complain about the youth of today.



  2. #2
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    Re: Temperature Gained?

    Assuming you mean 1m3

    Straight forward Viking..

    1 Watt = 1j/s
    1 hour = 3600 secs
    so 1 Watt for 1 hour = 3600joules or 3.6kj

    The mass of dry air at 20c is 1.205kg

    Specific heat of air is 1.22kj/kg, so

    Using the heat transfer formula Q = mass x c x (t1-t2) we can transpose to find the dt

    3.6/(1x1.205)/1.22 = dt

    dt = 2.4488K

    Temperature rise = 2.45 degrees C
    Last edited by frank; 01-11-2014 at 07:53 AM.

  3. #3
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    Re: Temperature Gained?

    Typo I think frank!
    3600joules = 3.6 Kj (not kw)

  4. #4
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    Re: Temperature Gained?

    Thanks Frank,
    You are of course right m3 it is.

    And thank you for the formula.


  5. #5
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    Re: Temperature Gained?

    Quote Originally Posted by mad fridgie View Post
    Typo I think frank!
    3600joules = 3.6 Kj (not kw)
    Spot on MF...wine kicked in lol
    I'll have to recalculate tomorrow... Beds calling☺

  6. #6
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    Re: Temperature Gained?

    Correction made ☺

  7. #7
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    Re: Temperature Gained?

    Cheers Frank,

    You are a true gentleman.


  8. #8
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    Re: Temperature Gained?

    Quote Originally Posted by frank View Post
    Spot on MF...wine kicked in lol
    You need to retune to vine from beer!

    I telling this from personal expirience!

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