STUDY ON PNEUMATIC CONVEYANCE OF COLD ENERGY USING A PHASE-CHANGE MATERIAL ENCLOSED IN SMALL SPHERICAL CAPSULES

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In this research, a refined cold-energy conveying system which reduces the required pump power was proposed and feasibility of the proposed system was discussed. Generally speaking, the conventional cold-energy conveying system, in which the cold-energy is directly transported by chilled brine, requires large pumping power especially when the amount of transporting cold-energy becomes large. In order to overcome the defect of conventional system, the proposed refined system utilizes the latent heat of a phasechange material (PCM) enclosed in a small capsule and the capsules are conveyed with gas flow.Small scale test loop of the proposed system was constructed to measure the conveying performances and cold-energy conveying performance of the proposed system was compared with the one of conventional system. The results snowed that, under the condition of identical cold-energy conveying rate, the proposed system requires less pumping power than the conventional one especially when the conveying rate of cold-energy becomes large (e.g. > 1 MW). In order to minimize the required pumping power, effects of shapes and sizes of the capsules on the pressure drop were also examined. The results that the pumping power required for vertical transportation of the capsules by using large capsules outer diameter of which is almost similar to the inner diameter of duct, and that spherical capsules require less pump power than cylindrical ones.In addition to these investigation, the investigators proposed a fluidized-bed-type freezer which make the PCM enclosed in a capsule vibrate to enhance freezing of supercooled PCM, and effects of amplitude and frequency of the vibration on freezing was examined. The results showed that the fluidized-bed-type freezer in which the capsules are fluidized with chilled gaseous medium is suitable for reducing supercooling of PCM enclosed in a small capsule.