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What is the heat flow through the ceiling into the attic in 4.5h?

  1. Dec 3, 2009 #1
    1. The problem statement, all variables and given/known data
    The ceiling of a room has an area of 135ft^2. The ceiling is insulated to an R value of 30 (in units of ft^2*deg. F*h/Btu). The surface in the room is maintained at 63 deg. F, and the surface in the attic has a temperature of 38 deg. F. What is the heat flow through the ceiling into the attic in 4.5 h?
    Express your answer in (a) BTU and (b) joules.


    2. Relevant equations
    The equation I used was the heat current equation with thermal resistance.
    H = [A(Th-Tc)] / R


    3. The attempt at a solution
    The equation I used was the heat current equation with thermal resistance.
    H = [A(Th-Tc)] / R
    = [(135ft^2)(63 deg. F - 38 deg. F)] / [30 ft^2*deg. F*h/BTU]
    = [(135)(25)] / [30]
    = 3.8 BTH / h

    I've already made an attempt to this problems and my results don't seem to not be right. Can someone please help me?
     
  2. jcsd
  3. Dec 3, 2009 #2

    kuruman

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    Science Advisor
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    Gold Member

    135*25/30 is not 3.8.
     
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