2021 Fiscal Year Final Research Report
Evaluating acceptable conditions of soils around heat exchanger for geothermal heat pump system
| Project/Area Number |
19K06327
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 41040:Agricultural environmental engineering and agricultural information engineering-related
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| Research Institution | National Agriculture and Food Research Organization |
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Principal Investigator |
Iwata Yukiyoshi 国立研究開発法人農業・食品産業技術総合研究機構, 農村工学研究部門, 上級研究員 (70370591)
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| Co-Investigator(Kenkyū-buntansha) |
山本 芳樹 日本工営株式会社中央研究所, 総合技術開発第2部, 課長 (60463577)
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| Project Period (FY) |
2019-04-01 – 2022-03-31
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| Keywords | 地中熱ヒートポンプ / 不飽和帯 / 水蒸気移動 / 水平型熱交換器 / コンタクト資材 / 熱伝導率 / 数値シミュレーション / 熱移動 |
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| Outline of Final Research Achievements |
To reduce the initial cost, horizontal geothermal heat pump system may be useful because there is a possibility to install heat exchanger cheaper. We conducted field research and 3-D numerical simulation for the horizontal heat pump system. First, we used a model considering heat conduction. We found that calculated temperature of the antifreeze solution at the outlet of the heat exchanger, which determines the efficiency of the heat pump system, were significantly higher than the observed values. This was probably because of the heat transportation of vapor flow, which occurs in unsaturated soil with high soil temperature and large thermal gradient. Thus, we developed a model to obtain apparent thermal conductivity, and found this method was useful for accurate calculation of the horizontal geothermal heat pump system. We also found the possibility that it may be possible not to use contact materials such as sand around the heat exchangers of horizontal heat pump system.
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| Free Research Field |
農業農村工学
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| Academic Significance and Societal Importance of the Research Achievements |
地中熱ヒートポンプの数値シミュレーションの既往の研究では、熱伝導や地下水の流れによる熱輸送の効果は組み込まれていたが、不飽和土壌中の水蒸気移動の効果は検討されてこなかった。本研究により、水平型地中熱ヒートポンプで冷房する際に、地温の上昇と温度勾配により水蒸気移動による熱輸送が無視できないことが初めて指摘された。開発した計算方法は見かけの熱伝導率を地温のパラメータとして計算できるため、計算負荷が非常に小さく、実用上の有用性も高い。また、熱交換器の周囲に充填していた砂を使用しなくても良い可能性を示すなど、熱交換器埋設の低コスト化に関するいくつかの知見が得られた。
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