An immersion heater is a device that can be submerged in a liquid to heat it. Th e heater is plugged into an electrical socket and in eff ect transforms electrical energy to thermal energy. One such...

An immersion heater is a device that can be submerged in a liquid to heat it. Th e heater is plugged into an electrical socket and in eff ect transforms electrical energy to thermal energy. One such heater is made of a 1/2 in. metal rod 5 in. long that draws 5 W. When the heater is submerged in 50°F oil, the heat-transfer coeffi cient between the rod and oil is 1.0 BTU/(hr · ft2 · °R). Determine the maximum temperature within the rod and the exterior surface temperature. Take the thermal conductivity of the metal to be 7.0 BTU/(hr · ft · °R).