First Experimental Data of the Cryogenic Safety Test Facility PICARD

Transcription

1 First Experimental Data of the Cryogenic Safety Test Facility PICARD C. Heidt, A. Henriques, M. Stamm and S. Grohmann 26 th International Cryogenic Engineering Conference 2016 in New Delhi, India KIT, INSTITUTE FOR TECHNICAL PHYSICS KIT, INSTITUTE FOR TECHNICAL THERMODYNAMICS AND REFRIGERATION EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN) KIT The Research University in the Helmholtz Association

2 Outline Motivation Helium Safety Design & Construction PICARD First Experimental Results Status & Outlook

3 Motivation Conventional conductors: el. resistance heat large energy losses Superconductors: materials with R = 0 Ω for low J, B, T Application: sc. cables, sc. magnets For J, B T Cooling with LHe, T nb = 4.2 K P.J. Lee, Superconducting Wires and Cables: Materials and Processing, EMSAT (2003) Helium enthalpy of evaporation h V 4.2 K; 1 bar = 2.6 kj l Factor 835 lower than water Factor 62 lower than nitrogen Quench: local loss of sc. heat propagation

4 Motivation

5 Helium Bath Cryostat Rupture disc, vacuum vessel He safety relief devices He filling and return lines He bath Vacuum vessel Power supply Superinsulation Sc. magnet Radiation shield Source: DIN SPEC 4683: Cryostats for liquefied helium Safety devices for protection against excessive pressure

6 Safety Concept Quench of a sc. magnet Worst case Sources: DIN SPEC 4683: : Cryostats for liquefied helium Safety devices for protection against excessive pressure; S. Grohmann, M. Süßer: Conceptual Design of Pressure Relief Systems for Cryogenic Application, AIP Conference Proceedings, 1573,

7 Consequences for Pressure Levels Sources: DIN SPEC 4683: ; S. Grohmann, M. Süßer: Conceptual Design of Pressure Relief Systems for Cryogenic Application, AIP Conference Proceedings, 1573,

8 Quench of Sc. Magnet

9 Venting of Insulating Vacuum

10 Dimensioning of cryogenic safety relief devices Existing models and standards (e.g. DIN EN 13648) do not consider process dynamics q = const. [1] Oversizing of safety valves Implications on spending, space and helium leakage Unstable operation reduced relief flow capacity (pumping, chattering) Dynamic model links all time-dependent sub-processes [2] ODE system based on thermodynamic and fluid mechanic principles Contains some simplifications (desublimation, kinetics) Experiments for validation and extension of model fit parameters [1] Lehmann, W., Zahn, G., Safety aspects for LHe cryostats and LHe transport containers, 1987 Proc. Int. Cryog. Eng. Conf [2] Heidt, C., Grohmann, S., Süßer, M., Modeling the Pressure Increase in Liquid Helium Cryostats after Failure of the Insulating Vacuum, 2014 AIP Conf. Proc

11 Outline Motivation Helium Safety Design & Construction PICARD First Experimental Results Status & Outlook

12 Purpose & Operating Range PICARD: Pressure Increase in Cryostats and Analysis of Relief Devices [3] Broad range of safety experiments in cooperation with CERN [4] Variation of Venting diameter Insulation Liquid level Set relief pressure Cryogenic fluid Mass flow rates Venting fluid Safety relief device Range Up to 40 mm Radiation shield, MLI % up to 100 L LHe Up to 12 bar(g) Helium, nitrogen Up to 4 kg/s Air, nitrogen Safety valve, rupture disc, control valve [3] Heidt, C., Schön, H., Stamm, M., Grohmann, S., Commissioning of the cryogenic safety test facility PICARD, 2015, IOP Conf. Ser.: Mater. Sci. Eng. 101, [4] Collaborative R&D on experimental testing on cryogenic pressure relief between CERN and KIT, KE2974/KT/DGS/222C,12/

13 Safety Test Facility PICARD Quench gas line Safety relief devices Filling line Assembly jig Vacuum pumps Exhaust gas line through water bath Venting orifice Cryostat Dewar

14 P&ID PICARD Venturi tube Rupture discs Vacuum vessel Vacuum pumps Safety valve Control valve Rupture disc Inner vessel Superinsulation Radiation shield Air inlet via orifice

15 Fast Temperature Measurement Measurement of temperature gradients in cryogenic fluid 7 plain TVO sensors

16 Fast Temperature Measurement

17 Level Measurement Capacitive level sensor 1 m Superconducting level sensor

18 Outline Motivation Helium Safety Design & Construction PICARD First Experimental Results Status & Outlook

19 Results of Commissioning Cooldown & filling time: 173 min to filling level of 49 cm = 60 L LHe consumption: 183 L Cooldown rate: 12 K/min

20 Settings of First Venting Experiments Vacuum insulation with radiation shield Venting with atm. air Venting diameter: 12.5 mm Filling level: ~50% Liquid He volume: 59 l Set pressure safety valve: 2 barg

21 Results of First Venting Experiments

22 Results of First Venting Experiments

23 Results of First Venting Experiments Staged protection: if margin between set pressures too small open system air moisture No additional pressure protection: plastic deformation or total mechanical failure Venting with gaseous nitrogen

24 Conclusions Successful commissioning Cooldown, filling and experiment in one day Verification of instrumentation consistence First venting experiments Safety valve DN25 oversized pumping overpressures But: small incidents more likely than maximum incidents Implications: small incidents more problematic than maximum incidents??? Safety valve performance to be further investigated

25 Outlook Planned experiments in course of R&D collaboration with CERN: Larger venting diameters Higher set pressures Larger heat fluxes With MLI Pressure close to critical point Additional quench of sc. magnet Investigation of Two-phase flow Safety valve behavior at cryogenic temperatures

26 Thank you for your attention!