Ecofriendly fluid sends chills through France

Researchers at the French Institute for Agriculture and the Environment, Cemagref, developed an ice ‘coulis’ made of water with a splash of ice and a soupçon of alcohol, salt or ammonia to keep the mixture fluid. The team spent years perfecting the mixture to suit industry’s needs. The resulting coulis carries a maximum of 30% of its water as ice crystals, whose optimum size is smaller than a millimetre to maximise the coulis’ fluidity and prevent it from freezing within pipes.

Although the fluid’s major drawback is an increase in viscosity with a lowering of its temperature, meaning circulation slows as the cooling potential increases, the ice coulis offers a major advantage over other refrigerants. Conventional fridges are typically unable to maintain a constant temperature, and can fluctuate over a 6°C range, resulting in a build up of unwanted ice which needs to be defrosted at regular intervals. The coulis refrigerates to within a 2&deg:C variation.

A handful of French shops are already using the mixture, which can be modified to suit different needs, using glycol, ethanol or other antifreeze substances. For temperatures below –20°C ammonia rather than salt should be used. The team is also perfecting the production process to enable the coulis to be manufactured on site.