well the point of using things like dry ice is to get sub zero temps
it will also be kinda hard to get the amount of pumping just right plus the ice will float on the water, you can always just through ice cubes in ur res or even put ur rad in ice water for some suicide runs,
but be careful of condensation!
custom pvc res=>DDC3.2w/xspc acrylic top=>DDC 3.2 w/xspc acrylic top=>Black Ice Extreme GTX 360(3xUK 3000's pulling)=>mcr 120=>Apogee GT (bowed)=>res
DDC Ultra w/xspc res-top=>RX360(3x pana Ultras pulling)=>enzotech nb block=>Dtek GFX 2=>res-top