A 2.2-mm·diameter and 14-m·long electric wire is tightly wrapped with a 1-mm-thick plastic...

A 2.2-mm·diameter and 14-m·long electric wire is tightly wrapped with a 1-mm-thick plastic cover whose thermal conductivity is k = 0.15 W/m·K. Electrical measurements indicate that a current of 13 A passes through the wire and there is a voltase drop of 8 V along the wire. If the insulated wire is exposed to a medium at Tx = 30°C with a heat transfer coefficient of h = 24 W/m2·K, determine the temperature at the interface of the wire and the plastic cover in steady operation. Also determine if doubling the thickness of the plastic cover will in- crease or decrease this interface temperature.

FIGURE P3-88