Homework SourseA down jacket has a surface area of 088 m2 and is filled wit
A down jacket has a surface area of 0.88 m2 and is filled with a 3.9 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 -19° C. At what rate is heat conducted through the coat?
The ANSWER for THIS SAMPLE PROBLEM is 22.4 kcal/h ... HOW DO I GET THIS EXACT ANSWER
The ANSWER for THIS SAMPLE PROBLEM is 22.4 kcal/h ... HOW DO I GET THIS EXACT ANSWER
Solution
the rate of heat transfer is given as
Q / t = kA(t2 -t1) / L
Q/ t = (6.0x10^-6 kcal / m.s C) (0.88m^2)[ 27 - (-19) ] / (0.039m)
= (6.0x10^-6 kcal / m.s C) (0.88m^2)[ 46 ] / (0.039m)
= 0.0062277 kcal /s
converting this into kcal / hr
= (0.0062276 kcal / s)(3600s /hr)
= 22.42 kcal /hr
