Heat Storage/Heat Release of Phase-Change Filling Body with Casing Heat Exchanger for Extracting Geothermal Energy

초록

Arranging heat exchanger in filling body to extract geothermal energy is an effective way to alleviate the problems of high ground pressure and high ground temperature in deep resource exploitation. Filling body with casing heat exchanger was acted as research object, encapsulating phase change materials (PCMs) in annular space. During heat storage and heat release process, the effects of different PCMs on temperature distribution, phase-change process and heat transfer performance were studied. The result indicates: During heat storage process, the temperature increases rapidly and the melting process is accelerated for the position closer surrounding rock. CaCl2 center dot 6H(2)O/EG can make filling body complete heat storage process in the shortest time because of its good thermal diffusivity. The heat storage capacity of PCMs backfill is significantly higher than that of ordinary backfill; it increases by 36.6%-67.3% at heat storage of 10 h. During heat release process, the closer to the heat exchange tube, the greater the temperature drop in filling body. The maximum value of heat release rate and heat release capacity is in CaCl2 center dot 6H(2)O/EG backfill, it can release 116.4% more heat than RT35 backfill after heat release of 12 h, the maximum value of effectiveness and its heat transfer rate also is in CaCl2 center dot 6H(2)O/EG backfill. This paper provides the basic data for the selection of PCMs in phase-change thermal storage filling body.

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