Stratification modelling of lake water used by Lindt & Sprüngli AG

Ramona Nüssli, February 12, 2020

3D-CFD application to validate the temperature stratification of lake water used for industrial purposes

The all-season cold water in the depth of Lake Zurich, represents an ideal source of cooling water for industrial companies like the Lindt & Sprüngli AG in Kilchberg (Switzerland). The reinjection of the water must take place below the thermocline (below 20 m of depth). Large temperature differences caused by returning the heated water into the lake, are only allowed to occur within a range of 20 x 20 m in horizontal and 10 m in vertical direction. Thereby nutrients transport to the vegetation zone at the surface should be prevented (see

TK CONSULT AG was commissioned with the evaluation of the effects of the lake water extraction and re-injection using a 3D-CFD stratification calculation. The simulation results show that no negative effect on the water and temperature balance of the lake was observed for both winter and summer conditions.

Temperature difference (dark blue), domain of 20 x 20 x 10 m (light blue), thermocline (dark green)