15.4 Steam at 100°C is injected into 1.8 kg of water at 22°C in a well-insulated container, where it condenses and mixes with the
existing water, reaching thermal equilibrium. If the final temperature of the well-mixed water is 25°C, what is the mass of the
injected steam?
kgSection 18 - Thermal conduction quantified
18.1 A window opening is 1.1 m by 1.3 m, and the wall thickness is 0.12 m. The temperature difference between the inside and
outside is 28°C. What is the rate of heat transfer through the opening if it is filled with (a) concrete, or (b) wood (fir)?
(a) W
(b) W18.2 A material has thermal conductivity of 0.380 W/m·K. What is its thermal resistance for a one-inch thick layer, in SI units of
m^2 ·K/W?
m^2 ·K/W
18.3 You want to add insulation under the roof of your house with a thermal resistance of 31.0 ft^2 ·F°⋅h/Btu. (a) What thickness of
fiberglass should you add, in inches? (b) What thickness of plywood would do the job?
(a) in
(b) in
18.4 A circular pond of radius 12 m has a layer of ice 0.25 m thick. On a spring day, the temperature of the water below the ice is
4.0°C and the temperature of the air above is 11°C. What is the rate of heat transfer through the ice, in kW?
kW18.5 A cube of wood and a cube of concrete, each
0.17 m on a side, are placed side by side. One
of the long faces of the rectangular prism
formed by the two cubes is held at 17°C, and
the opposite long face is held at 32°C. What is
the total rate of heat transfer through the
cubes?
W18.6 A copper rod and an aluminum rod with identical cross-sections are joined end to end. The free end of the copper rod is held
at a constant temperature of 94°C, and the free end of the aluminum rod is held constantly at 13°C. Where the rods meet, the
temperature is 45°C. If the copper rod is 2.4 m long, how long is the aluminum rod? (For the temperatures in the range
discussed here, the thermal conductivity of copper is 401 W/m·K and the thermal conductivity of aluminum is 237 W/m·K.
Ignore the heat loss through the sides of the rods.)
m
Section 21 - Interactive summary problem: pop the cork
21.1 Use the information given in the interactive problem in this section to calculate the heat flow required to pop the cork. Test
your answer using the simulation.
J