petra janickova
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Petra Janickova 21. February 2011
Investigation on Pressure Drop Phenomena of CO2 in Two Phase Flow
for Detector Cooling
1. Advantages of CO2 2. The test facilities3. Pressure drop measurements4. Comparison to the model 5. Conclusion
Petra Janickova 21. February 2011
• higher latent heat, 2 times more
then C6F14
• higher operation pressure then
C3F8 (at -20˚C it has 2 bar)
smaller gas bubbles in two phase
flow
lower probability of
plugging in mini channels
• lower Global Warming Potential
CO2 = 1 ; C6F14 = 7400
• resistant to radiation
• high heat transfer coefficient
especially in two phase flow
1. Advantages of CO2
Petra Janickova 21. February 2011
2. The different supply systemsSMALL SCALE SYSTEM: Compressing Condensing LARGE SCALE SYSTEM: Liquefying Pumping
Petra Janickova 21. February 2011
The portable test section
Expansion Heating Measurement Heating
wall temperature
fluid temperature
Petra Janickova 21. February 2011
3. Experimental results
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
50
100
150
200
250Large scale system Small scale system
Vapor quality
Pres
sure
dro
p [m
bar]
Petra Janickova 21. February 2011
3. Experimental results
400 500 600 700 800 900 10000
10
20
30
40
50
60
70
Mass flux [kg/m2s]
Offs
et ∆
p(∆p
) [m
bar]
Petra Janickova 21. February 2011
3. Possible reasons for the deviation
1. blocked capillaries
2. wrong measurement of the
mass flow
3. different kind of pump
1. Measurement of the pressure drop by
means of the temperature sensors
2. Calibration of the mass flow meter in
single phase
3. Measurement of eventual pressure
oscillations in the system
Petra Janickova 21. February 2011
3. Reasons for the deviation1. Measurement of the pressure drop by means of the temperature sensors
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
10000
20000
30000
40000
50000
60000
70000
80000
Δp_measured Δp_calculated
Vapour quality x
Pres
sure
dro
p Δp
in
[Pa/
m]
Large scale
Small scale
The deviation of calculated and measured mass flow is identical at both systems
Petra Janickova 21. February 2011
3. Reasons for the deviation2. Calibration of the mass flow meter in single phase
The coriolis mass flow meter is measuring by means of the coriolis effect Thus able to measure in liquid and gas phase
• A lower accuracy of the mass flux meter at low mass flux < 500 kg/m2s• Additional vibrations in the system can effect the measurement
0 200 400 600 800 1000 1200 14000
20
40
60
80
100
120
140
160
LIQUID GAS Prediction
Mass flux measured with the mass flow meter in cryolab G [kg/m2s]
Erro
r [%
]
Petra Janickova 21. February 2011
3. Reasons for the deviation2. Calibration of the mass flow meter in single phase
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
50
100
150
200
250
300
350
Small scale Large scale calibrated
Vapor quality x
Pres
sure
dro
p ∆p
[mba
r]
→ The deviation in mass flow is not effecting the pressure drop significantly
2 4 6 8 10 12 14 16 18 20 2225
30
35
40
45
50
55
Time [min]
Pres
sure
p [b
ar]
A = 1 bar
Petra Janickova 21. February 2011
3. Measurement of eventual pressure oscillations in the system
According to the datasheet: f = 2.33 Hz
3. Reasons for the deviation
Petra Janickova 21. February 2011
3. Measurement of eventual pressure oscillations in the system
Measurement in the test sectionA = 25 mbar
3. Reasons for the deviation
More measurements has to be done to prove the influence of the oscillations
Petra Janickova 21. February 2011
4. Proof of the model
0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800 0.900 1.0000
100
200
300
400
500
600
700
800
900
MODEL 300 kg/m^2*s 400 kg/m^2*s 500 kg/m^2*s 800 kg/m^2*s941 kg/m^2*s
Vapor quality x
Pres
sure
dro
p ∆p
[mba
r]
Petra Janickova 21. February 2011
4. Proof of the model
The deviation is growing bigger with higher mass flux and is negative at low mass flux
200 300 400 500 600 700 800 900 1000-20
0
20
40
60
80
100
120
140
160
180
200
220
240
Mass flux G [kg/m2s]
Offs
et ∆
(∆p)
[mba
r]
Petra Janickova 21. February 2011
4. Proof of the model
The friction factor is more depending on the mass flux: Introduction of a new friction factor with a mass flux ratio
0 10000 20000 30000 40000 50000 600000
0.0050.01
0.0150.02
0.0250.03
0.0350.04
0.045
Reynolds number ReV
Fricti
on fa
ctor
0 0.02 0.04 0.06 0.08 0.1 0.120
0.005
0.01
0.015
0.02
0.025
270 260 460460 f_calculated
Weber number WeL
Fricti
on fa
ctor
0 10000 20000 30000 40000 50000 600000
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
f_measured f_calculated f_new
Reynolds number
Fricti
on fa
ctor
Petra Janickova 21. February 2011
4. Proof of the model The model is not including the roughness Introduction of an additional part concerning the roughness
0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800 0.900 1.0000
100
200
300
400
500
600
700
800
900
1000
MODEL 300 kg/m^2*s 400 kg/m^2*s 500 kg/m^2*s800 kg/m^2*s 941 kg/m^2*s old f_M
Vapor quality x
Pres
sure
dro
p ∆p
[mba
r]
Petra Janickova 21. February 2011
5. Conclusion
• The pressure oscillations caused by a pump can cause a problem during the operation of the cooling plant for CMS. A solution could be:• A good damping system• A not fluctuating pump (gear pump)
• The coriolis mass flow meter should be calibrated before use• The latest released model has to be improved and therefore more measurements has to be done• at high mass flow• the dryout inception• the pressure drop
• Never trust the pressure restriction of the valves while doing a pressure test!
Petra Janickova 17. February 2011
Thank you for your attention!
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