What you have is a cross circuited, corrosion proof, DX coil. A direct expansion coil. It's too bad it isn't a dual circuit. It has several times the heat rejection capacity than a non finned coil. As long as it was never hooked up to a condensing unit, you can circ wort through the inside. As long as it doesn't plug up with hop goop. The coil has low pressure drop which will slow down the flow a little. That's a good thing. The coils are brazed with 45% silver and nitrogen purged. They leave the factory nitrigen filled, the coils aren't coated on the inside. The idea you have with the PC fans is kinda how a closed circuit water tower works. The only difference is, the water tower sprays water across the coil, using the lowered wet bulb temp to help cool the fluid by water evaporation. What you're doing is nothing new. There are water towers designed to cool wort to a reasonable temp, before pumping it to the refrigerated chiller or jacketed fermentor. Yours is just in the mini scale range. It certainly, will work. If you want to get more Rube Goldberg-ian. Make a spray header out of pvc with a bunch of holes drilled through it and spray the ice water throught the fins.