Petra Janickova

1. Investigation on Pressure Drop Phenomena of CO2 in Two Phase Flow for Detector Cooling Advantages of CO2 The test facilities Pressure drop measurements Comparison to the model Conclusion Petra Janickova 21. February 2011

2. 1. Advantages of CO2 • 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 Petra Janickova 21. February 2011

3. 2. The different supply systems SMALL SCALE SYSTEM: Compressing Condensing LARGE SCALE SYSTEM: Liquefying Pumping Petra Janickova 21. February 2011

4. The portable test section Expansion Heating  Measurement  Heating wall temperature fluid temperature Petra Janickova 21. February 2011

5. 3. Experimental results Petra Janickova 21. February 2011

6. 3. Experimental results Petra Janickova 21. February 2011

7. 3. Possible reasons for the deviation blocked capillaries wrong measurement of the mass flow different kind of pump Measurement of the pressure drop by means of the temperature sensors Calibration of the mass flow meter in single phase Measurement of eventual pressure oscillations in the system Petra Janickova 21. February 2011

8. 3. Reasons for the deviation Measurement of the pressure drop by means of the temperature sensors  The deviation of calculated and measured mass flow is identical at both systems Petra Janickova 21. February 2011

9. 3. Reasons for the deviation 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 Petra Janickova 21. February 2011

10. 3. Reasons for the deviation Calibration of the mass flow meter in single phase → The deviation in mass flow is not effecting the pressure drop significantly Petra Janickova 21. February 2011

11. 3. Reasons for the deviation Measurement of eventual pressure oscillations in the system According to the datasheet: f = 2.33 Hz Petra Janickova 21. February 2011

12. 3. Reasons for the deviation Measurement of eventual pressure oscillations in the system Measurement in the test section A = 25 mbar  More measurements has to be done to prove the influence of the oscillations Petra Janickova 21. February 2011

13. 4. Proof of the model Petra Janickova 21. February 2011

14. 4. Proof of the model The deviation is growing bigger with higher mass flux and is negative at low mass flux Petra Janickova 21. February 2011

15. 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 Petra Janickova 21. February 2011

16. 4. Proof of the model • The model is not including the roughness • Introduction of an additional part concerning the roughness Petra Janickova 21. February 2011

17. 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 21. February 2011

18. Thank you for your attention! Petra Janickova 17. February 2011