Michael Kauffeld

Investigation of Ice Crystal Growth and Geometrical Characteristics in Ice Slurry (RP-1166)

The physical properties and practical application of solid-liquid suspensions are influenced by, among other factors, the size and shape of the solid particles. In the case of ice slurry, this influence is especially visible with respect to fluid dynamic and heat transfer (melting) characteristics. This paper presents results from an investigation of the influence of different parameters on the time-dependent crystal growth rate in ice slurry. The parameters included in the study were (by weight) 10% ethanol and 15% propylene glycol as freeze-depressing agents in both homogeneously mixed storage (10 and 30% ice) and heterogeneous storage (30 and 46% ice). In addition, the effect of one crystal growth inhibitor (Tween® 85) and the influence of air exposure to the storage surface were investigated. All parameters were examined in combination and the growth rate was observed for 96 h. It was found that the geometrical shape of ice crystals in ice slurry is not significantly influenced by either time or any of the studied parameters.

Novel biomimetically based ice-nucleating coatings

Abstract Ice nucleation and ice repellence are properties which appear to be contradictory. Both are of great importance: The former for ice generation in the food and cooling industry and the latter for avoiding the adhesion of ice to structures. By mimicking a peculiar survival mechanism of some cold-adapted organisms a new type of coating system, able to both nucleate and repel the ice was developed. A heterogeneous surface containing locally isolated nucleation points in a low surface energy matrix were synthesised by a sol-gel process. The ice nucleating and ice releasing performance of the new ice nucleating coatings (INC) has been tested in a specially designed crystallisation chamber in comparison to commercial low surface energy coating systems. A mixture of demineralised water and a water freezing point depressant was used in the experiments. Compared to the commercial coatings, the INC surfaces showed a much higher ice nucleation rate but also a distinctly better ice releasing ability. Obviously the novel concept of local embedded nucleation points improves the ice repellent properties of surfaces.