[Butcher]

Yes I read what you said, pity you didn;t extend me the same courtesy.
If you check I didn't say fridges couldn't cool hot things, I said they can't cool all the time.
If you put food in the fridge it cools to the fridge temperature and therefore isn't an active load on the fridge. Dumping radiator exhaust in the fridge is a constant 50W+ load in there, hence the compressor has to run all the time to cope with the continual heat dump.
Fridges aren't designed for this, you'd be much better off getting a compressor setup designed for 100% duty cycle and setting that up, not only would you get lower temps but you would also be a lot less likely to nuke your compressor.