Development of New Method for Measuring of Ice Packing Factor in Ice Storage Tank by Sensing of Electric-Conductivity of Aqueous Solution--Application to Ice-on-Coil Type Ice Storage Tank--

Kazuo AIZAWA*,†,††,†††, Hidemasa OGOSHI, Kanetoshi HAYASHI, Katsuya MAEYAMA††† and Noriyuki YONEZAWA†††

† Engineering Research Center, NKK Corporation; 1-1 Minami-Watarida-cho, Kawasaki-ku, Kawasaki-shi 210-0855 Japan
†† Present address: Environment Plant Design Division, NKK Design and Engineering Corporation; 3 Benten-cho, Tsurumi-ku, Yokohama-shi 230-0044 Japan
††† Department of Organic and Polymer Materials Chemistry, Tokyo University of Agriculture and Technology; 2-24-16 Naka-machi, Koganei-shi 184-8588 Japan

As a new method to measure ice packing factor (IPF) in ice-on-coil type statical ice storage tank, electric-conductivity sensing of aqueous solution coexisting with ice was investigated in view point of application to district cooling and heating systems. Ice forming and melting process was monitored by measurements of total volume and electric-conductivity of the aqueous solution-ice mixture inside the test apparatus.
The correlations between two IPF values determined by changes in volume and the electric-conductivity were obtained by changing kind of electrolyte, initial concentration of electrolyte in the solution, and ice formation rate. When a low ice formation rate corresponding to the operation condition for actual ice storage tank systems was chosen, it was found that the electrolyte in the solution was concentrated almost ideally with growth of ice. The specific electric-conductivity and concentration ratio have a linear correlation. Good linear correlation of two determination methods for IPF demonstrates that this new determination method based on electric-conductivity has sufficient accuracy and utility on the condition that good mixing is performed and concentration of electrolyte is equal or higher than that in tap water.

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