Question

A down jacket has a surface area of 0.78 m2 and is filled with a 4.2 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 29° C. The outer surface of the coat is at -19° C. At what rate is heat conducted through the coat?

Answer 1

Rate of heat conduction = kA(delta T) / L
k is thermal conductivity of material
A is area through which heta condcuts
delta T is tempreature difference across end
L id distance between ends
rate of heta conduction = 6x10-6 kcal/s.m.oC * 0.78m2*(29oC - (-19oC) ) / 0.042 m
                                     = 5.3x10-3 kcal/sec