In a simple thermal conductivity measuring device, the center rod is a metal wit
ID: 1850263 • Letter: I
Question
In a simple thermal conductivity measuring device, the center rod is a metal with unknown thermal conductivity k which is to be found. The upper surface of the rod is maintained at 85 degree C with an electrical heater, while the lower surface is held at 23 degree C with a cooling water flow through a plate-type heat exchanger. Determine the value of k if the electric power input is 18.75 W and the specimen length and diameter are 0.1 m and 0.03 m, respectively. Is there a metal approximately having this value of k? Clearly state the assumption(s) you made and comment.Explanation / Answer
Q = kA(T1 -T2)/L
18.75 = k*(/4*0.03^2)*(85 - 23)/0.1
k = 42.8 W/m-K
This is closer to steel.