High performance use of ground source heat using underground water flow

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K12273
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 64050:Sound material-cycle social systems-related
• Research Institution: Saga University
• Principal Investigator: Tsubaki Koutaro 佐賀大学, 理工学部, 助教 (70432961)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 地中熱利用 / 地下水流動

Outline of Final Research Achievements

Experiments revealed that horizontally installed ground heat exchangers cause groundwater flow near the surface layer during rainfall, which affects the amount of heat exchange. In numerical simulations, OpenFOAM was used to create models corresponding to groundwater heat exchangers in the soil at different angles in addition to a model with the groundwater flow perpendicular and parallel to the groundwater flow, and calculations were performed under different heating conditions and other conditions. The calculation of the porous media was performed using the Darcy law in the equation of motion to calculate the details of the change in heat transfer when the direction of the groundwater heat exchanger is changed. The calculation results show that the heat transfer rate changes significantly when the flow is perpendicular to the groundwater flow, but the effect is very small when the flow is parallel to the groundwater flow by about 10°.

Free Research Field

循環型社会システム関連

Academic Significance and Societal Importance of the Research Achievements

局所的な地下水流動が地中熱利用に与える影響についての研究や調査例は殆どない。地下水流動についての主な国内の研究は、建築・土木分野における広域での地下水の履歴などを対象とした数km規模であり、地中熱交換器の性能に影響を与える伝熱学の視点からの数m規模の例は少ない。本研究で実験的に浅部での雨と地下水の影響を、数値シミュレーションでは水平設置の角度の影響を明らかにしたことにより、地下水流動の影響を考慮した長期的な地中熱交換器の性能変化および周囲の土壌温度に与える影響の予測へとつながる。今後地中熱利用の普及が期待される東南アジアは日本と同じく地下水が流れやすい地層であるため、将来的に展開が期待される。