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Calculating R value

  1. Mar 28, 2016 #1
    1. The problem statement, all variables and given/known data
    Determine the R value of the unknown specimen using a conventional hot box.

    Surface area of the specimen is 0.009 m2.
    Initial Hot Room Temperature = T Hot Initial = 30 ° C = 303.15 K
    Initial Cold Room Temperature = T Cold Initial = 20 °C = 293.15 K

    Time for both rooms reach to equilibrium = 2 hours = 7200 seconds
    Temperature after 2 hours in hot room = T Hot final = 22 °C = 295.15 K
    Temperature after 2 hours in cold room = T Cold Final = 22 °C = 295.15 K
    The gas in Hot room is Specific heat capacities = 1 J/(kg K) and masses = 1 kg
    The gas in Cold room is Specific heat capacity = 1 J/(kg K) and masses = 1 kg


    2. Relevant equations

    R Value = dT x A / Q
    Q = m x c dt / time

    3. The attempt at a solution


    Determine rate of heat flow.

    Q = m x c x (T Cold Final - T Cold Initial ) / Time difference

    = 1 kg x 1 J/(kg K) x (295.15 K – 293.15 K) / 7200 sec

    = 2.78e-4 J per Sec


    Determine R value

    R Value = dT x A / Q

    = ((T Hot Initial - T Cold Final) x A) / Q

    = ((303.15 K – 293.15 K) x 0.009 m2 ) / 2.78e-4 J per Sec

    = 324
     
  2. jcsd
  3. Apr 2, 2016 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
     
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