Ecofriendly fluid sends chills through France
French scientists have come up with the perfect formula for an ecofriendly ice fluid to replace environmentally damaging refrigerants like chlorofluorocarbons.
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°: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.