1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Thermal conductivity

  1. Sep 27, 2014 #1
    • Warning! All queries in the Homework section must use the Posting Template provided when a new thread is started.
    The information I am given is : a door has two steel layers both are .47 mm thick, the door itself is 725 mm by 1800mm. The question asks, how thick of a layer of wood (oak) would have to be put in the door to limit the heat loss to 740kJ per hour? Temp inside is 18C and outside is -20C

    All work is done with only three significant digits.

    I have been working with the equation ;
    Where; k is the thermal conductivity of the material
    X is the unknown

    I have run threw the equation several times but every time I either can't isolate the variable or end up with a wrong answer.

    0.205kJ/sec= ((1.30m^2)(38C))/((9.40*10^-5m/43W/mC)+(Xm/0.17W/mC))

    Is this the right equation and/or have I made a simple error with conversions ?

    Please don't post full answer I want to find it but tips or suggestions would be awesome !!!
  2. jcsd
  3. Sep 27, 2014 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

  4. Sep 29, 2014 #3
    thanks but it is still escaping me i feel like i am just one step away from getting it.... very frustrating but it i will prevail !! :P
  5. Sep 29, 2014 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    Did you try simply solving for X in your equation? (Note that it is usually easier not to make mistakes if you solve the algebraic expression first and insert numbers when this is done)
  6. Sep 29, 2014 #5
    whats the next step? and what is the equation you started with was it H= -kA (dt/dx)
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted

Similar Discussions: Thermal conductivity
  1. Thermal conduction (Replies: 0)

  2. Thermal Conductivity (Replies: 3)

  3. Thermal conductivity (Replies: 6)

  4. Thermal Conduction (Replies: 7)

  5. Thermal conductivity (Replies: 8)