The blood plays an important role in removing heat from the body by bringing thi
ID: 1420862 • Letter: T
Question
The blood plays an important role in removing heat from the body by bringing this heat directly to the surface where it can radiate away. Nevertheless, this heat must still travel through the skin before it can radiate away. We shall assume that the blood is brought to the bottom layer of skin at a temperature of 37.0 C and that the outer surface of the skin is at 30.3 C . Skin varies in thickness from 0.500 mm to a few millimeters on the palms and soles, so we shall assume an average thickness of 0.770 mm . A 165 lb , 6.00 ft person has a surface area of about 2.00 m2 and loses heat at a net rate of 75.0 W while resting.
On the basis of our assumptions, what is the thermal conductivity of this person's skin?
Explanation / Answer
Rate of heat loss = k A deltaT / deltax
A = surface area = 2 m^2
deltax = thickness = 0.770 mm = 0.770 x 10^-3 m
deltaT = 37 - 30.3 = 6.7
75 = k (2) (6.7) / (0.770 x 10^-3)
k = 4.31 x 10^-3 W / m K
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