Natural convection in groundwater-filled boreholes used as ground heat exchangers
In most of the world, borehole heat exchangers used with closed-loop ground source heat pump systems are backfilled with a low permeability grout to prevent water contamination. However, in Scandinavian countries, a different approach is taken – the borehole is sealed at the top and cased down to solid bedrock. The borehole then naturally fills with groundwater in the annular space between the U-t