Synthetic Study on the Techniques for Storage/Conveyance/Utilization of Cold Energy using Phase-Change Phenomena

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It is known that the thermal storage system utilizing the phase-change phenomena is quite effective, but that the efficiency is reduced by the supercooling phenomenon occurring in the Phase-Change Materials (PCMs). At the same time, in order to supply the cold energy stored in PCMs, conveying technique should be settled since the cold is stored in frozen, i.e.solid, PCMs, which can not be easily moved. This study therefore dealt with the storage/conveyance techniques of cold as well as the phase-change phenomenon itself. At the same time, new applications of cold energy with phase-change phenomena, i.e., cooling of electronic devices and freezing preservation of organisms, were also examined. The results can be summarized as follows :(1) Liquid-to-solid Phase-change phenomenon including the supercooling was numerically examined by using molecular dynamics simulation method. From the simulation, thermal properties of supercooled water and the effect of electric field on the freezing pro … More bability of supercooled water were discussed.(2) Pneumatic conveying characteristics of the cold using bare-ice cubes were experimentally examined so as to compare the results with the ones of the system using ice enclosed in spherical capsules. The results showed that the cold loss during conveyance with bare-ices is larger than that in encapsuled case, but that the pumping power is little affected.(3) melting heat transfer of a brine-ice mixture flowing inside a horizontal tube was experimentally examined. From the results, it was obtained that the heat transfer coefficient in the downstream region increases with increase in flow velocity of the brine-ice mixture, and that the local heat transfer decreases with increasing the concentration of brine.(4) Heat transfer characteristics of the liquid-solid two-phase flow within micro-channels were examined so as to apply the heat transfer to the cooling of electronic devices. Heat transfer and pressure drop within a channel of 0.5-3mm height were measured, and the results were discussed from the viewpoint of heat transfer enhancement.(5) Freezing characteristics and osmotic pressure of a protoplast of wheat were experimentally examined, and the effects of ice-crystal generation within a cell on the damage to the cell were discussed from the microscale view point. Using the results, relation between the cooling rate and biological condition of the organic cells was obtained. Less