In the conduction equation Q = (kAT)t/L, the combination of factors kA/L is call
ID: 1446865 • Letter: I
Question
In the conduction equation Q = (kAT)t/L, the combination of factors kA/L is called the conductance. The human body has the ability to vary the conductance of the tissue beneath the skin by means of vasoconstriction and vasodilation, in which the flow of blood to the veins and capillaries underlying the skin is decreased and increased, respectively. The conductance can be adjusted over a range such that the tissue beneath the skin is equivalent to a thickness of 0.092 mm of Styrofoam or 2.3 mm of air. By what factor can the body adjust the conductance?
Explanation / Answer
Factor = Maximum / Minimum
Let's just assume that the styrofoam is the maximum and see how that works (the factor should be greater than one if we are right).
Factor = (K-styro * A /T-styro) / (K-air * A / T-air)
Factor = (K-styro / T-styro) / (K-air / T-air)
Factor = (K-styro * T-air) / (T-styro* K-air)
K - air = 0.025 W/(m·K)
Thermal resistivityof stryrofoam is usually about 35 m·Kelvin/W
K-styro = 1/ R-styro = 1/(35 m·Kelvin/W)
K-styro = 0.029 W/m-K
T-styro = 0.000092 m
T-air = .0023 m
Factor = (K-styro * T-air) / (T-styro* K-air)
Factor = (0.029 W/m-K * 0.0023 m) / (0.000092 m * 0.025 W/(m·K))
Factor = ?