I have a residential fridge now but in my previous camper, I mounted one of these on the lower of the two vents by the fridge with a simple inline switch. 200mm Fans are used often in the top of computer cases for high powered gaming computers for a couple reasons. One, they move significant amounts of air at a lower, quieter RPM. Because of being oversized from the 120mm fans most computers have and being on top, they act much like the attic fan referenced earlier and do so nearly silently.
I only turned it on when it was 85+ but it made all the difference in the world of the fridge struggling to stay in an acceptable range or it doing a great job on the dog days of summer.
NOCTUA 200mm FanThis is a top quality computer fan brand.