Question

A down jacket has a surface area of 0.82 m2 and is filled with a 3.8 cm thick layer of down, which has a thermal conductivity of 6.0 10-6 kcal/(s · m · C°). The coat is worn by a person whose skin temperature is maintained at 27° C. The outer surface of the coat is at -23° C. At what rate is heat conducted through the coat?

Answer 1

6• 10^-6 kcal/(s • m • C°) =0.025 J/(s • m • C°)
Fourier's Law of Conduction
ΔQ/ Δt = λ•A•( ΔT/ Δx) =0.025• 0.82•(50/0.038) =0.27 J/s