- #1

- 2

- 0

http://i.imgur.com/8ztNq.gif

We have a x=5mm thin aluminium wall used for dividing two air flows. T1=308 K and T2=283 K. Aluminium has a thermal conductivity of k=220 W/m,K. Assuming the wall areas are 1 m

^{2}we can use the equation

1/U=(1/h1)+(x/k)+(1/h2)

to determine the overall heat transfer coefficient U [W/m

^{2}K].

What are some reasonable values for the heat transfer coefficients h

_{1}and h

_{2}? If we have these values we can calculate the heat flow Q [W] through the wall. For instance, using h1=60 W/m

^{2}K and h2=40 W/m

^{2}K, we get Q=U*dT=600 W.

Now say we want to put a thermal barrier coating on the hot side of the wall so that the wall temperature, Tw1, goes up by 10 K. The coating has a very low thermal conductivity of k=0.02 W/m,K. Is there a way to estimate how thick the coating needs to be to achieve this? Is there enough info to solve this, or do we need more numbers?

Does the heat transfer coefficient h

_{1}change when we apply an insulation layer? Any help or tips would be greatly appreciated!