1993 Volume 19 Issue 6 Pages 1023-1030
The proposed ice storage system uses several kinds of hydrogel as heat supports. The vaporization heat of water from highly water-containing gel is stored as the heat of freezing of the remaining water. The first key to the realization of this system is development of a vacuum compressor with large evacuation rate for water vapor at low pressure and with high efficiency. It is also important to evaporate water at high temperature, as near the freezing point as possible, to produce ice with high efficiency.
A 1-liter cylindrical Dewar vessel made of stainless steel was used as a heat container and diaphragm pumps were used for evacuation. Four types of polymer gel materials and two kinds of ice nucleation active substances (INS), AgI and ice nucleation active protein (INAP) produced by an ice nucleation active bacterium (INB : Xantmonas campestris), were used in the experiments.
For practical use, the evaporation rate of water is described as proportional to the vapor pressure of water at the temperature of the gel.
Both kinds of INS were effettive in raising the break-point of supercooling from -58°C (without INS) to -1-3°C (with INS). INAP is recommended for use in this system as a harmless, reproducible organic INS.
