Fig. 8From: Impact of operational temperature changes and freeze–thaw cycles on the hydraulic conductivity of borehole heat exchangersMean values of hydraulic conductivity measurements of KBHE at varying temperature steps with initial state (A), cooling process (black) to 3 °C (B), heating process (red) to 12 °C (C), heating process after FTC6 (green, D) and comparison values of a parallel experiment according to VDI 4640-2 (2019) with the same grout–pipe material combination at 20 °C, mean values of 3 specimen 600 readings each (E)Back to article page