Put the warm beer in a cooler, ice on top, then pour salt on the ice...beer cools down quick.
For maximum effectiveness, you must twists the beers constantly to cool the beer evenly. In about 2-3 min you will have near frosty beer! College did pay off!
A beer can’s heat transfer to its’ surroundings can be maximized by increasing the amount of surface area that is exposed to the differential temperature of the beer can to its’ surroundings. Thus, immersing a beer can in cold water provides this maximization in that it also lowers the resistance to heat flow caused by the thin film coefficient at the water/ beer can interface.
Techniques such as putting the beer can in the freezer do not work as well since, although you have an increase in differential temperature, the air to can thin film resistance coefficient is extremely large when compared to that of the water to can thin film coefficient.
Putting salt on ice takes advantage of the colligitive property of decreasing the freezing point of water (increasing the differential temperature) however, it is the reduction of the thin film coefficient effected by the contact of liquid water with increased can surface area that explains the phenomena you report.