1. Pressure oscillation and the damper function
J WU, T Koettig, P Janickova, L Zwalinski

2. Oscillation of the pump discharge pressure
Time
Pressure [Bar]
At certain low discharge pressure of the pump, there is no oscillation. With increase of the pressure, the oscillation starts. The frequency of the oscillation is about 3 Hz. The amplitude (p2p) is about 1 bar.

3. Effect of the damper Temperature of the damper [˚C]
Damper on (with heating)
Pressure [Bar]
Oscillation is due to not enough heat load
in the dummy load.
JT valve of the chiller is active.
Damper off (without heating)
Damper has no obvious effect on the damping of the oscillation.

4. Test station connected with the large scale system
From the large scale system
To the large scale system

5. Pressure measurement in the test station
Time [s]
In the test station, the pressure P1 before the JT expansion valve still oscillates with the same frequency as the discharge pressure of the pump. Much less amplitude (25mbar)
After JT expansion, the pressure P2 has no oscillation.
It is possibly dampened by the JT expansion valve and the capillary connected with
the pressure sensors P1 and P2.

6. Suction side pressure before the chiller
PT1106
Time [s]
The suction side pressure PT1106 before the chiller of the large scale system has no oscillation too.
It seems the oscillation has no effect on the pressure drop measurement along the test section.

7. PT1105
TT1102
PT1106
PT1102
Run the pump
Disconnect the test section
Close the bypass of the
dummy-load

8. (inlet pressure test section) (temperature in the damper)
Damper Heater
PT1105
(discharge pressure)
PT1102
(inlet pressure test section)
PT1106
(suction pressure)
T1102
(temperature in the damper)
off
P+[bar]
71.3
70.57
64.1
19˚C
Liquid in damper
P-[bar]
70.36
69.70
62.2
∆P[bar]
0.94
0.83
1.9 on
72.2
71.5
64.8
34˚C
Gas in damper
70.8 63
0.9
0.75
1.8
The damper has very small effect on the reduction of the oscillation amplitude
The oscillation amplitude of the suction side is about 2 times bigger than the discharge side of the pump