I was just reading up on a technique called "whirlpool chilling" and I'm intrigued. It claims to get temps down in less than five minutes. A whirlpool chiller is just an immersion chiller with some sort of whirlpool device to mix the wort up constantly. It would seem to be an easy addition to add a mix/stir attachment to a drill to get a whirlpool going during the chill. Do any of you use a whirlpool chilling system?