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Cooling with tiny crystals

August 27, 2004

Refrigeration equipment prevents sweaty brows in the summer and also keeps our food fresh for longer periods. With CryoSol®, a new and easily pumpable liquid ice suspension, space requirements for cold storage are much lower than with conventional coolants.

Keeping things cold is not only important in summer. Ice cream and beer is only really enjoyable when it is properly chilled. Milk, fresh from the cow, must immediately be stored in a cool room. Every product requires a special refrigeration technology. The new liquid ice suspension CryoSol® not only provides a way to chill food and keep commercial production plants cool, it can also be used in indoor air-conditioning systems. CryoSol is a versatile, high-performance coolant developed by researchers at the Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT in Oberhausen. The liquid, non-toxic medium provides low-cost, high-capacity cooling while saving space.

"Our ice slurry reminds one of the slush drinks we loved as kids," says Christian Doetsch, head of the energy systems department at UMSICHT. The ice is created in an externally cooled hollow cylinder. A rotating ice scraper abrades the tiny ice crystals that form on the inner walls of the cylinder. The resulting ice crystal suspension is then transfered to a storage container, to be used as needed for cooling and climate control. CryoSol can easily be pumped through conventional refrigeration equipment and pipes. In food manufacturing, chilled water and crushed ice/water mixtures have long been the standard coolants.

At the end of the 19th century, engineer and businessman Carl von Linde revolutionized the market with his compression refrigerator. His invention eventually displaced natural ice, the only cooling alternative up to that time. In Linde's machine, the basic principle was to use a coolant - in this case ammonia - that takes up heat when it vaporizes. When pressurized, the coolant transfers the heat to the surrounding of the machine. When the pressure is reduced, the process starts over again. Most refrigerators in households still operate on this closed cycle principle.

The CryoSol unit is based on the same principle, while additionally taking advantage of the ice's melting energy. "The cooling capacity is significantly higher than standard chilled water technology and consumes much less energy than crushed ice/water mixtures," adds Doetsch. "With an ideal ice content of fourty percent, the CryoSol container can maintain a total cooling capacity equivalent to a chilled water storage unit five times as large." This pays off particularly during peak demand periods. The UMSICHT lab already boasts pleasant year-round temperatures thanks to its own CryoSol unit.

Fraunhofer-Gesellschaft