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

Lase

r

Plexi glas

12.5 m

1.3 m

7.5 m 50 mm

Application of the potential

Water flowWater flow

Water flowWater flow

Water flowWater flow

Measured velocity profile with and without DC-potential

0

0,2

0,4

0,6

0,8

1

1,2

0 5 10 15 20 25 30 35 40

Relative units

Position inward from the pipe wall

Vmean= 1.0 m/s, Re = 50000

0

0,2

0,4

0,6

0,8

1

1,2

0 5 10 15 20 25 30 35 40

Position inward from the pipe wall

Relative units

Vmean= 0.5 m/s, Re = 25000

Vmean= 2.0 m/s, Re = 100000

Addisional observation

Water flow

Pumping water

DC-potential

Lase

r

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

Uring(R)

U

U UPipe(R)

12.5 m

Results – Potential distributionUpipe(R)

-1000

-800

-600

-400

-200

0

200

400

600

1 3 5 7 9

11

13

15

17

19

21

23

25

OCP [mV]: Upipe(R) URing(R)

V/ 0.8 V [mV]: Upipe(R) URing(R)

Results

URing(R)0

50

100

150

200

250

300

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

1.1 V

0.8 V

0.5 V

U = Upipe(R) - Upipe, ocp(R)

Potential changes [mV] vmean = 1.0 m/s Potential changes [mV] vmean = 2.0 m/s

0

50

100

150

200

250

300

1 3 5 7 9 11 13 15 17 19 21 23 25

U = Upipe(R) - Upipe, ocp(R)

1.1 V

0.8 V

0.5 V

0

2

4

6

8

10

12

14

16

18

0 0,2 0,4 0,6 0,8 1 1,2

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

P1

P2

Active effect

Reactive effect

Results – Head loss(Q2)

0

5

10

15

20

25

30

35

40

45

0 2 4 6 8 10 12 14 16 18 20 22 24

Hea

dlos

s [m

]

Q2 [m6/s2]Q2 [m6/s2]

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 measurementsTheoretical studies involving electrochemistry andfluid 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.