[oil pan 4]

Since I understand how refrigeration works, no I have not built one.

I don't think it will cool worth a crap.

Like Daox said, I believe in liquid cooled seats. With the ice water cooled seats you are pretty much only trying too cool heat your body puts off.

The ice to air cooler has to cool the air, you and the heat you put off, plus all the heat coming into the car from solar radiation, thermal conduction from the out side environment which includes engine heat coming through the floor and fire wall.

If you want to cool off using ice, buy a 10 pound block and set it in your lap (the primitive version of cooled seats).

Here is why it wont work to cool the interior of your car.
Small to mid size car air conditioners seem to put out some where between 2,000 to 5,000 BTUs per hour when stopped in traffic with a heat soaked condenser with minimal air flow and A/C compressor turning at idle speed.
In large SUVs and luxury cars on the highway cooling capacity could easily exceed 12,000BTUs per hour.

A bucket with 10lb of ice and a fan has a cooling capacity of some where around 1,440BTUs in the amount of time it takes it to melt (I am thinking well over an hour).
That would work great if you were only trying to cool your back and bottom. At rest I believe a person puts off something like 400 BTUs per hour.

If you could melt 10 pounds of ice for air cooling every 20 or 30 minutes, it would work in theory/on paper (which means it rarely ever works out the way you think it will).