Dry Ice
From TPU Reference
Also: Dice
Dry Ice is CO2 (Carbon Dioxide) in its frozen state. Carbon Dioxide forms the bubbles in your soda water or carbonated soft drinks.
Under normal pressure, Carbon Dioxide sublimates (goes straight from gas to frozen state) at -78.5°C or -109.3°F.
Dry Ice is used by many extreme overclockers in the world as a coolant. You build a container (usually from Copper because of heat conductivity) into which you put smashed pieces of Dry Ice. Please be careful when handling dry ice with bare hands, it can leave nasty skin burns from the cold.
Since the Dry Ice forms small crystals it does not make optimum contact with the sides of your container. Typically a thermal interface material that has a low freezing point is added. Good TIMs are: Highly pure alcohol (95%+) or Acetone. Water can not be used because it freezes too quickly, at 0°C. The Dry Ice in your container will slowly evaporate because it turns into a gas from the heat, it leaves no residue. This means that from time to time you have to add more Dry Ice to your container.
Because your hardware parts will be cooled below average temperature, condensation will start forming on them from the surrounding air. A common way to counter this is by insulating all the cold parts.
