I have a tiny 40 MM 6 cfm 0.03a muffin fan on the inside of my 1.8 cubic foot fridge, blowing into the freezer compartment, and it works great at keeping the temps inside even, and cooler at the same setting.
Does not make it use less electricity, just givems me more overhead to crank it up if I want, and cools down items placed withn faster, and keeps all internal box temps within 3 degrees of each other. Without the fan my IR gun shows a spread of nearly 20 degrees from the warmest to the coolest spot.
Computer/ Muffin Fans vary widely in how much air they move for noise made and current consumed.
So not get a sleeve bearing fan for a horizontal mounting location.
Shop around, don't just goto radio shack.
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