# Transfer of heat question

1. Apr 20, 2010

### Andrews989

1. The problem statement, all variables and given/known data

The amount of heat per second conducted from the blood capillaries beneath the skin to the
surface is 240 J. The energy is transferred a distance of 2.0×10−3mthrough a body whose surface area is 1.6 m2. Assuming that the thermal conductivity is that of body fat 0.2 J /(s ⋅m⋅o C) , determine the temperature difference between the capillaries and the surface of the skin.

So k = .2
A = 1.6 m^2
L = 2.0 x 10^-3m

I'm not sure what the 240 J goes as? Is that Q?

2. Relevant equations

This is basically where I'm stuck... I'm not sure what equation to use.

I was thinking possibly Q = k * A * change in T * time all divided by L .... but there's no mention of time?

3. The attempt at a solution

2. Apr 21, 2010

### AtticusFinch

You wrote down the right equation. Notice that give you a rate of heat transfer so you can divide time over to the left side of the equation.

Then it's just a substitution of information problem.

3. Apr 21, 2010

### Andrews989

So...

Q/t = k * A * change in T / L

240 = .2 * 1.6 * change in T / 2 X 10^-3

So the answer would be 1.5 degrees?

I think that's right... thanks