Estimation of groundwater flow from temperature monitoring in a borehole heat exchanger during a thermal response test

Yoshioka, Mayumi; Takakura, Shinichi; Uchida, Youhei

Estimation of groundwater flow from temperature monitoring in a borehole heat exchanger during a thermal response test | Estimation des écoulements d’eau souterraine par un suivi de température dans une sonde géothermique verticale, pendant un test de réponse thermique Estimación del flujo de agua subterránea a partir del monitoreo de temperatura en un intercambiador de calor en un pozo durante un ensayos de respuesta térmica 热响应试验期间根据钻孔热量交换器的温度监测估算地下水流 Estimativa do fluxo de águas subterrâneas a partir do monitoramento de temperatura em tubos permutadores de calor durante um teste de resposta térmica

2018

Yoshioka, Mayumi | Takakura, Shinichi | Uchida, Youhei

To estimate the groundwater flow around a borehole heat exchanger (BHE), thermal properties of geological core samples were measured and a thermal response test (TRT) was performed in the Tsukuba upland, Japan. The thermal properties were measured at 57 points along a 50-m-long geological core, consisting predominantly of sand, silt, and clay, drilled near the BHE. In this TRT, the vertical temperature in the BHE was also monitored during and after the test. Results for the thermal properties of the core samples and from the monitoring indicated that groundwater flow enhanced thermal transfers, especially at shallow depths. The groundwater velocities around the BHE were estimated using a two-dimensional numerical model with monitoring data on temperature changes. According to the results, the estimated groundwater velocity was generally consistent with hydrogeological data from previous studies, except for the data collected at shallow depths consisting of a clay layer. The reasons for this discrepancy at shallow depths were predicted to be preferential flow and the occurrence of vertical flow through the BHE grout, induced by the hydrogeological conditions.

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