Stratification modelling of lake water used by Lindt & Sprüngli AG

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 https://pubdb.bfe.admin.ch/de/publication/download/8797).

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.