A well-insulated 4-m * 4-m * 5-m room initially at 10C is heated by the radiator of a steam-heating system. The radiator has a volume of 15 L and is filled with superheated vapor at 200 kPa and 200C. At this moment both the inlet and the exit valves to the radiator are closed. A 120-W fan is used to distribute the air in the room. The pressure of the steam is observed to drop to 100 kPa after 30 min as a result of heat transfer to the room. Assuming constant specific heats for air at room temperature, determine (a) the average temperature of air in 30 min, (b) the entropy change of the steam, (c) the entropy change of the air in the room, and (d) the entropy generated during this process, in kJ/K. Assume the air pressure in the room remains constant at 100 kPa at all times.
A well-insulated 4-m * 4-m * 5-m room initially at
10C is heated by the radiator of a steam-heating system. The
radiator has a volume of 15 L and is filled with superheated
vapor at 200 kPa and 200C. At this moment both the inlet
and the exit valves to the radiator are closed. A 120-W fan
is used to distribute the air in the room. The pressure of the
steam is observed to drop to 100 kPa after 30 min as a result
of heat transfer to the room. Assuming constant specific heats
for air at room temperature, determine (a) the average temperature
of air in 30 min, (b) the entropy change of the steam,
(c) the entropy change of the air in the room, and (d) the
entropy generated during this process, in kJ/K. Assume the air
pressure in the room remains constant at 100 kPa at all times.
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