Effect of Various Parameters on a Supercooling Phenomenon of Still Bulk Water and Water Solution

Supercooling characteristics on still bulk water and several kinds of water solutions were investigated experimentally. The test fluids, which were sandwiched in between two immiscible liquids in a glass tube, were set in a constant low-temperature room, and its freezing temperature was measured. It was found that the critical degree of supercooling for the water increased with decreasing test fluid volume, V, and was proportional to the logarithm of V. However, the critical degree of supercooling for the water solutions varied with the type of solute, and for each solute, it increased with increasing solute concentration. The critical degree of supercooling for the water solution was larger than that for the water by about 0～4 K. The increment supercooling, which depended on the type of solute, could be explained by the equilibrium freezing point depression, an increase in the viscosity and solute/water interactions. In addition, the present data for the water solutions were correlated with dimensionless parameters which expressed these effects.本研究は、水溶液の過冷却現象を利用したスラリー状氷を生成させる氷蓄熱システムの完成を最終目標とし、まず容器内に充墳した比較的容積の大きな水および各種水溶液の静止状態における過冷却現象の解明を対象として取り上げて、その過冷却現象の基本的特徴を探るものである。第一に氷核生成の要因が不均質核生成に強く依存する系のもとでの水の限界過冷却度を定量的に明らかにした上で、その基礎資料にもとずき水と同一条件下で有機・無機水溶液、溶質の種類および濃度等が、水溶液の過冷却現象に与える影響について実験的に検討するものである。得られた水溶液の過冷却現象に関する情報は、過冷却状態を利用した流動水溶液によるスラリー状氷の連続性氷技術および水溶液媒質の氷結緩和作用による輸送性に富むスラリー状氷の流動特性解明に活用せれ、新しい機能性に富む氷蓄熱・輸送システムの実現、本研究は大いに役立つものと思われる