Composite

Fourier’s Law, Composite Solid Cylinder?

October 31st, 2009 | by admin |

I have this experiment which I don’t understand at all. I hope some kind soul can help.

I have a solid cylinder, comprising 3 sections. Section 1 is connected to the heat source and is manufactured from brass (k = 121 W/mK). 3 temperature sensors, T1, T2, T3 are installed at 15mm intervals along the working section which has a diameter of 25mm. The heat source is assumed to be 5mm from the first sensor T1.

Section 2 is made up of stainless steel (k= 25 W/mk) and has a length of 30mm and diameter 25mm.

Section 3 is also made up of brass and is cooled with running water at the end. 3 temperature sensors, T6, T7, T8 are also fitted in it at 15mm intervals. The running water is assumed to be 5mm from T8. Spacing between T3 and T6 is 45mm.

The heat flows from the top to the bottom of the cylinder in one dimension. Now I have to use these equations to calculate the experimental overall heat transfer coefficient, Uexperimental.

Uexperimental = Q/[A*(Th -Tc)]

Th =66.9
Tc = 25.7

q" = -k (dT/dx)

Q = Aq" = (k/L) * A * (TL-TR)

I don’t understand what is "k" and how to get it!!!!

I’m also supposed to use 1/Utheory = L/K = L1/k1 + L2/k2 + L3/k3 to find the theoretical value of the overall heat transfer coefficient U.

k is the thermal conductivity

Beyond this, your problem is a difficult one for this forum. You probably have sufficient material at hand to understand how to solve it, if you study the materials and try. Once you do this, if you are having trouble, I suggest you show your work to the point where you need help, including your references. Then, we may be encouraged to spend the necessary time to be of some use.

.