Departmental Bulletin Paper 浅いため池底層水の夏季における冷熱源としての可能性

佐藤, 恵一  ,  吉越, 恆  ,  長﨑, 裕司

(18)  , pp.65 - 73 , 2018-03-28 , 国立研究開発法人 農業・食品産業技術総合研究機構 , National Agriculture and Food Research Organization (NARO)
農業用ヒートポンプの熱源としての浅いため池の可能性を検討するため,ため池底に熱交換器を設置し,地中浅層埋設の場合と比較しつつ,ため池底に設置することによって性能が向上する理由を明らかにした.水中に設置した場合,熱交換器の周辺水温は,熱交換器から 10cm 程度離れたポイントで 0.2℃ 程度の水温上昇しか認められないのに対して,地中に浅層埋設した熱交換器の上部 10cm~20cm の地層では,約 10℃ の地温上昇が認められ,高温状態が約 10 日間継続した.水中設置の場合,パイプ近傍の排熱滞留を短時間で解消させる対流が働き,熱交換器の性能を優位にしているものと考えられた.To determine if a shallow pond could act as a heat source for a heat exchanger, of an agricultural heat pump, submerged under the pond surface, a heat exchanger was installed in a shallow pond. Tests were carried out to compare this system with an identical system buried in the ground. The reason for the performance improvement in the case with the heat exchanger submerged in the pond was shown. In the case of the submerged system, the ambient water temperature rose by only 0.2°C even at a distance of 10 cm from the heat exchanger, while an approximately 10°C rise in soil temperature was observed in the buried system, which continued over lasting days. The present study suggests that some thermal convection mechanism is formed around the submerged heat exchanger and it contributes to the high heat- exchange performance in the water.

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