The tip of a soldering iron consists of a 0.6-cm diameter copper rod, 7.6 cm long. If the tip must be 204°C, what are the required minimum temperature of the base and the heat flow, in watts, into the base? Assume that h= 22.7 W/(m2 K) and Tair = 21°C.
GIVEN
FIND
(a) Minimum temperature of the base (Ts)
(b) Heat flow into the base (q) in W
ASSUMPTIONS
The tip is in steady state
The thermal conductivity of copper is uniform and constant, i.e., not a function of temperature
The copper tip can be treated as a fin
SKETCH
(a) the temperature distribution for a fin with a uniform cross section and convection from the
tip is
Evaluating the temperature at x = L
Solving for the base temperature
(b) To maintain steady state conditions, the rate of heat transfer into the base must be equal to the rate of heat loss from the rod. From Table 2.1, the rate of heat loss is
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