Fig. 12From: Impact of operational temperature changes and freeze–thaw cycles on the hydraulic conductivity of borehole heat exchangersPlain view in the dismantled and washed BHE body of PE-HD pipes (A) and grout (B) under day light (1) and black light (2). Circumferential flow paths (C) at the PE-HD pipes and cracks (D) between return (E) and inlet flow (F) are clearly visibleBack to article page