How does steady state refrigeration work?

[Bonulo]

When a refrigerator has been turned on for some time, steady state refrigeration occurs. This is the normal refrigerator operative state. But what exactly happens?

These things are really hard to do research on, since Internet searches, regardless of search query detailing, result in a lot of useless sites. Our textbook, University Physics 11th Ed., has nothing on the subject.


Does the compressor

1. lower its amount of work done on the refrigerant so much, that the refrigerator cools as quickly as heat conduction heats the food? (I don't think so)

2. lower its amount of work for some time, when the temperature gets a bit too cool, then increase it, when the temperature gets a bit too hot, and continue this way, steadily lowering and increasing its work? (This has been suggested to us)

3. reverse the process for some time (so that heat is pumped into, instead of out of the refrigerator) and continue steadily reversing the process? (This too has been suggested)

 

[Astronuc]

Under steady-state operation, a refrigerator removes as much heat from the cold region as leaks back in from the environment. The in-leakage of heat depends on the temperature differential, or more commonly, convection of cold atmosphere out which is displaced by warmer air (as when one opens the door). There is a thermocouple control which shuts of the compressor once the desired temperature is achieved, and thereafter, the control will activate the compressor once a warmer temperature is acheived.

Compressor work is usually constant, at least for residential systems. What changes is the efficiency at which heat is transferred.

See if these help -
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heatpump.html

http://www.aie.org.au/melb/material/resource/cop.htm

http://ist-socrates.berkeley.edu/~phy7b/solutions/T5_WkSheet/T5soln.html

http://electron9.phys.utk.edu/phys136d/modules/m3/heatpump.htm