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  1. Contents • Progress at the large scale CO2 system, • Results of the small scale CO2 system in the cryolab.

  2. CO2 - Large scale system Joao Noite, Lukasz Zwalinski, Torsten Koettig

  3. CO2 - Large scale system

  4. CO2 - Large scale system

  5. CO2 - Large scale system • Location in 158: • - Commissioning of the system at 25°C, • Possible mass flow rate 1...15 g/s, • Run only at ambient temperature • at the moment, • Next step => accumulator to vary Tsat. Joao Noite, Lukasz Zwalinski, Torsten Koettig

  6. CO2 – Small scale system Small scale system in the cryolab CERN: Test section length: 300 mm, heated part: 150 mm • Measurement of the heat transfer coefficient and pressure drop under variation of the following dependencies: • Vapor quality x • Heat flux q • Mass flux G • Saturation temperature Tsat Jihao Wu, Daniel Helmer

  7. CO2 - Small scale system Heat transfer coefficient in the flow map (Tsat=263 K, G=300 kg/m2s, q=15kW/m2)

  8. CO2 - Scanning the two-phase region Pressure drop in the flow map (Tsat=263 K, G=300 kg/m2s, q=15kW/m2) Pressure drop [mbar] Mass flux [kg/m2s] Vapor quality x

  9. CO2 - Scanning the two-phase region • Measurement of the heat transfer coefficient and pressure drop under variation of the following dependencies: • Vapor quality x • Heat flux q • Mass flux G • Saturation temperature Tsat

  10. CO2 - Scanning the two-phase region Heat flux dependency of the heat coefficient (T=263 K, G=400 kg/m2s)

  11. CO2 - Scanning the two-phase region Heat flux dependency of the pressure drop(T=263 K, G=400 kg/m2s)

  12. CO2 - Scanning the two-phase region • Measurement of the heat transfer coefficient and pressure drop under variation of the following dependencies: • Vapor quality x • Heat flux q • Mass flux G • Saturation temperature Tsat

  13. CO2 - Scanning the two-phase region Mass flux dependency of the heat coefficient (T=263 K, q=7.5 kW/m2)

  14. CO2 - Scanning the two-phase region Mass flux dependency of the pressure drop (T=263 K, q=7.5 kW/m2)

  15. CO2 - Scanning the two-phase region • Measurement of the heat transfer coefficient and pressure drop under variation of the following dependencies: • Vapor quality x • Heat flux q • Mass flux G • Saturation temperature Tsat

  16. CO2 - Scanning the two-phase region Temperature dependency of the heat coefficient (q=15 kW/m2, G=300 kg/m2s)

  17. CO2 - Scanning the two-phase region Temperature dependency of pressure drop (q=15 kW/m2, G=300 kg/m2s)

  18. Resume • Reliable test setup to determine heat transfer and pressure drop, • Measurements in the whole two phase region are done, • Influences of mass flux, heat flux and saturation temperature. Paper will be submitted to Int. Journal of Heat and Mass Transfer

  19. CO2 - Small scale system Instabilities Observed instabilities: J-T expansion into subcooled liquid or x<3% oscillations occur Oscillations are amplified reaching the dryout at around 75 % vapor quality Temperatures below -34 °C