Answer :

Solution :

Given, Cp = 400 J/kgK, ρ = 8500 kg/m³, t = 4.35 sec, r = 0.5 mm

Ti = 100°C, T∞ = 20°C, T = 28°C

Using equation (1) and putting the given values :

$\ln \left(\frac{100-20}{28-20}\right)=\left(\frac{h\times 3\times 1000}{0.5\times 8500\times 400}\right)\times 4.35$

$\Rightarrow h=\frac{2.302\times 0.5\times 8500\times 400}{3000\times 4.35}=299.87W/m^{2}K$

∴ Heat transfer coefficient = 299.8 W/m²K