Heat transfer characteristics of buried pipes under groundwater seepage in Karst regions

Abstract

Utilising geothermal energy through ground-source heat pump (GSHP) systems is a viable option. Karst regions, renowned for their abundant geothermal resources and complex geological structures, present a unique challenge owing to the presence and fluctuations of groundwater, which significantly alter the operational environment of GSHPs. Therefore, it is crucial to explore the mechanisms and performance of GSHPs in such areas. Based on actual Karst geological structures and using similarity theory, a multi-layer experimental model of a ground heat exchanger (GHE) was established in a laboratory. To enhance the GSHP performance, a forced seepage plan for shallow soil layers was proposed. Then, a controlled variable method was employed to investigate the impact of aquifer-related groundwater seepage factors on the heat transfer performance of buried pipes. Thresholds for groundwater velocity and temperature that enhanced thermal performance were identified. Groundwater seepage shortens the recovery time of the temperature field in geotechnical materials and influences the heat exchange intensity based on the flow temperature. This study focuses on a layered heat transfer model and proposes a relationship between aquifer thickness and geotechnical heat transfer, providing theoretical support for the application and optimisation of GSHP systems in Karst regions.