Temporal monitoring of thermal disturbances induced by shallow heat exchangers : petrophysics modeling and geo-electrical imaging
Basket geothermal heat exchanger buried at shallow depth and connected to heat pumps can be used to heat and/or cool buildings. Heat transfers and performance related to geothermal basket are complex due to heterogeneous petrophysical properties of the soil, freezing of ground and surface environmen...
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| Other Authors: | , , , , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | French |
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HAL CCSD
2021
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| Subjects: | |
| Online Access: | https://tel.archives-ouvertes.fr/tel-03256522 https://tel.archives-ouvertes.fr/tel-03256522/document https://tel.archives-ouvertes.fr/tel-03256522/file/COPEREY_2021_archivage.pdf |
| Summary: | Basket geothermal heat exchanger buried at shallow depth and connected to heat pumps can be used to heat and/or cool buildings. Heat transfers and performance related to geothermal basket are complex due to heterogeneous petrophysical properties of the soil, freezing of ground and surface environmental conditions e.g. air temperature variations. To study heat transfers, a geophysical monitoring of electrical conductivity and induced polarization has been developed using three experiments at different scales. First, a petrophysical model was designed from laboratory measurements. This model describes at the pore scale, the variation of electrical conductivity and chargeability according to the soil temperature and frost. This model was applied to an in-situ experiment to monitor the growth of an ice-core. We have also designed an analogic experiment at small scale and under controlled conditions in order to study the heat transfers and the effect of the soil freezing according to different environmental conditions. This study shows the importance of lateral flow and the influence of freezing during system operation. The petrophysical model was tested and validated with several datasets and geophysical monitoring was able to detect the formation and melting of the ice core. Les corbeilles géothermiques sont des échangeurs thermiques hélicoïdaux implantés dans le proche sous-sol qui couplés à une pompe à chaleur, permettent de chauffer et/ou de rafraichir les bâtiments. Comprendre les transferts thermiques liés à ces systèmes et étudier leurs performances requiert de prendre en compte les propriétés pétrophysiques hétérogènes du sol, les phénomènes de changement de phase et les conditions environnementales, dont les variations de température de l’air et la pluviométrie. Dans ce but un monitoring géophysique en conductivité électrique et en polarisation provoquée a été développé à l’aide de trois expériences à différentes échelles. Tout d’abord, un modèle pétrophysique a été élaboré à partir d’une série ... |
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