Question

A mild steel tank of wall thickness 12 mm contains water at ${95}^{\circ }C.$ The thermal conductivity of mild steel is $50W/m^{\circ }C,$ and the heat transfer coefficients for the inside and outside the tank are 2850 and $10W/m^2{}^{\circ }C$ respectively. If the atmospheric temperature is ${15}^{\circ }C,$ then the overall heat transfer coefficient is

• A. $994W/m^2{}^{\circ }C$
• B. $0.944W/m^2{}^{\circ }C$
• C. $9.94W/m^2{}^{\circ }C$
• D. $99.4W/m^2{}^{\circ }C$

Answer 1

The correct option is C $9.94W/m^2{}^{\circ }C$

$\text{Over all heat transfer coefficient}$
$\frac{1}{U}=\frac{1}{h_1}+\frac{L}{k}+\frac{1}{h_0}\frac{1}{U}=\frac{1}{2850}+\frac{0.012}{50}+\frac{1}{10}\text{Overall heat transfer coefficient (U)}=9.94W/m^2-K$