jbotelho@cern.ch - FSTS weekly meeting 1

FSTS “water hammer” Running mode

• Pressure profile of the “water hammer” pulse – Joukowsky Equation

• FSTS Running worst case scenario:

– instant closing of a valve: dt = 0.

– C3F8 liquid: Temperature = - 60 °C; Pressure = 16 bar.– ΔP = 3.13 bar

tva

tP

..

vaP ..

15/11/2011

jbotelho@cern.ch - FSTS weekly meeting 2

FSTS “water hammer” worst case scenario • Pressure increase on vertical liquid pipe line as function of mass flow or liquid velocity:

• Calibrated orifice to reduce the maximum fluid velocity (or mass flow)?

• Even with 43mbar of dP for nominal flow, the orifice would not restrict the flow!• In any case, there is a risk of liquid fall after the restrictor and we can not put an orifice each “x”

meters.

15/11/2011

0

1

2

3

4

5

6

7

8

9

0 0.5 1 1.5 2 2.5 3 3.5

dP [b

ar]

Mass flow [kg/s]

0

1

2

3

4

5

6

7

8

9

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

dP [b

ar]

Liquid velocity [m/s]

4

1

2

2

1....2

1DD

ACmPcsd

0.0

0.1

0.1

0.2

0.2

0.3

0.3

0.4

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

dP [b

ar]

mass flow [kg/s]

Orifice diameter = 25mm

jbotelho@cern.ch - FSTS weekly meeting 3

Conclusion• Does the risk of high pressure or shock wave formation exists in

case of vertical liquid drop?

• How to reduce the pressure increase due to vertical liquid fall if it can happen?– Should we insert siphons on the vertical line?

• If yes, what is the maximum distance between them?

• One possible solution is to regulate the liquid flow after the condenser in case the dP between the tank and the bottom of the plant does not correspond to the hydrostatic pressure difference.

15/11/2011