Briefs: Ice cubes at over 10°C

Ice slurries are well known for their capacity to transport heat within confined systems. Cemagref is currently working on a new type of two-phase secondary refrigerant: a gas-hydrate slurry which could pave the way for applications in the industry and in air conditioning. In the early 2000s, in the framework of a study on the crystallization of water, researchers at Cemagref in Antony, France, observed the formation of gas-hydrate crystals at positive temperatures, over 10°C, which proves to be very interesting for the air-conditioning sector as it enables domestic cooling without entailing such cold temperatures and uses an environmentally friendly secondary refrigerant. The team that set up an experimental prototype of an ice-slurry making system is led by Laurence Fournaison, who is incidentally the chairperson for the IIR Phase-Change Materials and Slurries for Refrigeration and Air Conditioning Working Party. The aim of the prototype is to characterize the thermal and hydraulic properties of the slurry and model its behaviour. It was thus discovered that hydrate slurry was very efficient, providing 500 kJ of energy on melting, whereas 1 kg of ice crystals provides only 333 kJ.