Question

Q5. a wire 1.5mm in diameter and 150 mm long is submerged in the water. an electric current is passed through the wire which boils the water at 100°c. if the convective heat transfer coefficient is 4500 w/m2°c , find how much electric power must be supplied to the wire to maintain the wire surface at 120 °c .

Answer 1

The surface area of the wire is $A=\pi dL$, where $d=1.5\;mm,L=150\;mm$.

The convective heat transfer coefficient of the wire is 4500 W/m2°c.

When the heat transfer is in equilibrium, electric power must be supplied to the wire to maintain the wire surface at 120 °c is

$P=A(4500)(120-100)\\ P=\pi 1.5*150*10^{-6}(4500)(120-100) \\ P=63.62\;W$