Monthly Archives: January 2011

Thermally Enhanced Grout for Geothermal Drilling

Boreholes in areas that permit the use of natural materials for backfill must be sealed at the surface in accordance with governing codes. If holes are to be grouted from bottom to top, high solid bentonites should not be used. The commonly used “high solids” bentonite grouts have around 20% solids- and a thermal conductivity value of approximately .40. This is a very poor heat transfer capability and impedes heat exchanger to ground heat transfer. This is not a problem when the bentonite is used as the sealing material in the top 10-20 fee or so of the borehole. However, if it used to grout the entire borehole, it has a very negative impact on the U-bend’s heat exchange capacity.
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