The January 2013 Physics Challenge for Teachers and Students1 has some features that are surprising and worth a closer look. The problem concerns a Carnot-cycle refrigeration unit operating inside a tent. It achieves dynamic equilibrium with a freezer (“cold”) compartment temperature of TC=13°C⁠, tent temperature of TH=1°C (the “hot” waste side of the freezer), and temperature “outside” the tent of TO=0°C⁠. The problem is to find the equilibrium temperature inside the tent if an identical freezer is brought in and run simultaneously. As explained here, what constitutes an identical freezer is open to interpretation.

Topics
Electrical energy, Energy conservation, Energy use and applications, Thermal conductivity, Reversible process, Thermal instruments, Thermodynamic states and processes, Refrigerators, Educational assessment, Teaching
1.
Boris
 
Korsunsky
,
“When It's 2 Cool, It Gets Hot!”
 
Phys. Teach.
 
51
,
56
(
Jan. 2013
).
Google Scholar
 
© 2014 American Association of Physics Teachers.
2014
American Association of Physics Teachers
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