ok... here's the idea...
take an old window AC and carefully take it apart. you'll find the 3 main components inside...
2. condenser (hot side)
3. evaporator (cold side)
you can use the AC's original evaporator but depending on what you are doing it may be better to build your own(like in the pic below)
basically, you submurse the evaporator in a bucket, cooler, whatever you have, full of the coolant for the water loop. the evaporator supercools the water.