A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h1, h2 and h3 respectively. The average heat transfer coefficient for the cube is
A. $${{\text{h}}_1} + {{\text{h}}_2} + {{\text{h}}_3}$$
B. $${\left( {{{\text{h}}_1}{{\text{h}}_2}{{\text{h}}_3}} \right)^{\frac{1}{3}}}$$
C. $$\frac{1}{{{{\text{h}}_1}}} + \frac{1}{{{{\text{h}}_2}}} + \frac{1}{{{{\text{h}}_3}}}$$
D. None of these
Answer: Option C
Solution (By Examveda Team)
A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h1, h2 and h3 respectively. The average heat transfer coefficient for the cube is $$\frac{1}{{{{\text{h}}_1}}} + \frac{1}{{{{\text{h}}_2}}} + \frac{1}{{{{\text{h}}_3}}}.$$This Question Belongs to Mechanical Engineering >> Heat And Mass Transfer
A) all surfaces will be consider as in parallel connection, so thermal resistance is inversely proportional to h.
1/R proportional to h.
(h1+h2+4h3)/6