A small distiller evaporates 1 L of water per half hour. Copper tubing exposed to the air serves as a condenser to recover the steam. The outside surface of the tubing is at 99.9°C. The ambient temperature is 20°C. The inside diameter of the tube is 0.75 cm, and the outside diameter is 1.2 cm. The thermal conductivity of copper is 388 W/m K. he for saturated steam at 100°C is 2257 kJ /kg.

How long must the tube be to condense all of the steam?

a) 0.3 nm
b) .2 m
c) 2.4 m
d) 8.3 mm
e) 10.8 m