An experimental study of Water Flow in Pipelines under Influence of Applied Electrical DC-Potentials M. Waskaas Telemark University College Porsgrunn, Norway

The idea and hypothesis Given a pipeline made of electric conductive material, through which water containing ions, is flowing. An electrical potential between the pipewall and fluid is established. The electric force acts as a friction in addition to the mechanical and hydrodynamical friction for the flow. If the potential is reduced, then this additional friction is also reduced, and the result is an increased flow rate near the pipewall.

Advanced experimental setup - in principle Water flow Pumping water DC-potential Laser Plexi glas 12.5 m 1.3 m 7.5 m  50 mm

Application of the potential Water flow

Measured velocity profile with and without DC-potential V mean = 1.0 m/s, Re = 50000V mean = 0.5 m/s, Re = V mean = 2.0 m/s, Re =

Addisional observation Water flow Pumping water DC-potential Laser Plexi glas Fouling Clean

Experimental setup – potential measurements Reference electrode (R) Ag/AgCl I + Applied potentials: OCP, 0.5, 0.8 and 1.1 V U ring (R) U U U Pipe (R) 12.5 m

Results – Potential distribution U pipe (R) OCP [mV]: U pipe (R)U Ring (R) V / 0.8 V [mV]: U pipe (R)U Ring (R)

Results U Ring (R) 1.1 V 0.8 V 0.5 V  U = U pipe (R) - U pipe, ocp (R) Potential changes [mV] v mean = 1.0 m/sPotential changes [mV] v mean = 2.0 m/s  U = U pipe (R) - U pipe, ocp (R) 1.1 V 0.8 V 0.5 V Current [  A] V / 1m/s Current [  A] V / 2m/s

Full scale field experiment in a powerstation 12.5 MW, 85 GWh Pelton turbine Pipeline: L = 1600 m, D = 1 m Head: 380 m Head loss: 44.1 m

Water Reservoir Turbine inlet Applied DC-potential Applied DC-potential on the pipeline in Vrenga powerstation Pipeline

The electric insulated manlock

Head loss in tunnels and pipelines Turbine Head loss – 44.1 m Flow Q Head – 380 m P1P1 P2P2 Active effect Reactive effect

Results – Head loss(Q 2 ) Q 2 [m 6 /s 2 ] Head loss [m]

Results Head loss is reduced by 13 % Energy production is increased by 1.8 %

Addisional observation The fouling inside appears to be reduced

Summary Increased water flow rate at the pipewall in a pipe when exposed to a particlular electric DC-potential is observed. A gradient in the electrical potential distribution along the pipe has been measured. Maximum potentrial at the inlet. This holds for both exposed and unexposed to electric DC-potentials. In a hydroelectric powerstation: A decrease in the head loss up to 14 % An increase in the power production up to 1.8 % The study is still in progress. Experiments – water flow and potential measurements Theoretical studies involving electrochemistry and fluid mechanics will be initiated

Acknowledgement I thank prof. V. Daujotis, Vilnius University, Lithuania; prof. K.Esbensen Aalborg University, Denmark; assoc. prof. K.E.Wolden, Telemark University College and tehnician Inger H. Matveyev, Telemark University College for assistance with the experiments.