Question:-
A flat plate has thickness 5 cm, thermal conductivity 1 W/(mK) convective heat transfer coefficients on its two flat faces of 10 W/(m2K) and 20 W/(m2K). The overall heat transfer coefficient for such a flat plate is
Option (A)
5 W/(m2K)
Option (B)
6.33 W/(m2K)
Option(C)
20 W/(m2K)
Option(D)
30 W/(m2K)
Correct Option:
(A)
Question Solution:

UA = (1 / åR) = [1/{(1/h)+(b/k)+(1/h)}]
UA = [1 / {(1/10)+(1/20)+((5 x 10-2)/1)}]
1/UA = (1/10) + (1/20) + (1/50) = ((10+15+2)/100) = 17/100
UA = 100 / 17 = 5.88
question-answer-faq-6097