I'm certainly no expert on thermodynamics (as my college transcript can attest) but it is my understanding that most spacecraft are cooled by radiation.

I recently saw photos of the ISS showing radiators being installed, and the Shuttle has radiators on the inside of the payload bay doors. Additionally, I seem to recall the Shuttle having "flash evaporators" for cooling when the doors are shut.

As for the A13 situation, most of the heat generating electronics were shut off during the trip home. Without doing any research whatsoever, I'd assume that the CSM radiated heat faster than it was being generated internally by the crew and operational electronics. I don't know if any evaporative cooling was going on, but I'd assume the crew would turn it off if the cabin was getting cold.

With enough work, one could do a thorough analysis of the situation and determine if the temperature in the cabin was consistant with the amount of heat being generated (and absorbed from the sunshine) and radiated away.

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I may have many faults, but being wrong ain't one of them. -- Jimmy Hoffa