Progress on calculations for pressure relief device sizing

Progress on calculations for pressure relief device sizing Vacuum break of DSHx / DSHm WP 6 a safety meeting : 8 December 2020 Y. Leclercq, V. Gahier

Calculation note § Present assumptions and calculations for each scenario listed in EDMS 2303664 HL-LHC Cold powering failure modes working group (meeting #14) 2

Table 2 : summary § List various scenarios § Define associated protecting relief device § List key values (dissipated power, mass flow, relief device sizing) HL-LHC Cold powering failure modes working group (meeting #14) 3

Reminder heat transfer mechanism in case of Loss of Insulation Vacuum (LIV) Main mechanism For Full LIV, norm suggests to use 6 k. W/m 2 HL-LHC Cold powering failure modes working group (meeting #14) 4

Source for insulation vacuum loss § Rupture of an air connection (e. g. Instrumentation) § § On DF side On DFH side § Perforation of the SC Link thin external envelope § Collapse under high radial load (transport vehicule roll over, fall of heavy item during transport along) most of the service gallery is not accessible : cage to be added to avoid this case. § Mitigation measures are in place to avoid large insulation vacuum loss. HL-LHC Cold powering failure modes working group (meeting #14) 5

Pressure drop calculation in corrugated pipe • In laminar regime : the flow behaviour is very close to a smooth pipe • In turbulent regime, some vortex are formed in the corrugations, however there is a minimum impact on the main flow • In very turbulent regime, vortex in the corrugations impact the main flow as well. Demo 2 test zone From Witzenmann databook : correlation derived from Daniels and Cleveland • • Height and pitch of the corrugation have an impact on the friction factor. The highest the corrugations compared to the diameter, the highest the friction factor The highest the spacing of corrugations, the lowest the friction factor Good accordance with litterature has been found in the transition and turbulence zone : friction factor taken at 0. 13 for LIV due to higher Reynolds (10 e 5) expected during this event. HL-LHC Cold powering failure modes working group (meeting #14) 6

4. 3. 1 Vacuum break in DSHx § § § Basis of design: Assuming a cable diameter of 90 mm, an ID 100 and the convolutions details, the gas volume (neglecting the gas between the cables) is about 3. 21 litres/m. For a 80 m SC Link, the total amount is 257 litres. ~55 m 2 of total surface § Assumptions : § § § No mass transfer to the DFx or DFHx All energy deposited instantaneously in the SC link gas Limited Heat in leak : 18 k. W corresponding to a air ingress from a 15 mm orifice which is the most likely air ingress orifice Cable and SC link metal mass neglected for the calculation Friction factor on the SC link : 0. 13 based on feedback experience of Demo 2 HL-LHC Cold powering failure modes working group (meeting #14) 7

Results for DSHx Steady increase of pressure (closed volume considered) until BD Set pressure is reached in DFX. Peak pressure will depend mainly upon : Friction factor in the SC link cryostat SC link cross section Air ingress quantity To be noted : BD area has little influence once the minimum area is reached Max pressure reached is lower than 3. 5 bara in SC link, DFX and DFHX considering a BD orifice of 50 mm. HL-LHC Cold powering failure modes working group (meeting #14) 8

Vacuum break in DSHm § § Basis of design: Assuming a cable diameter of 70 mm, an ID 80 and the convolutions details, the gas volume (neglecting the gas between the cables) is about 2. 58 litres/m. For a 120 m SC Link, the total amount is 310 litres. § Assumptions : § § § No mass transfer to the DFx or DFHx All energy deposited instantaneously in the SC link gas Limited Heat in leak : 18 k. W corresponding to a air ingress from a 15 mm orifice which is the air ingress orifice the most likely Cable and SC link metal mass neglected for the calculation Friction factor on the SC link : 0. 13 based on feedback experience of Demo 2 HL-LHC Cold powering failure modes working group (meeting #14) 9

Results for DSHm Same calculation methodology as for the IT Cold powering system used. BD orifice considered at 30 mm. Max pressure reached is lower than 3. 5 bara in SC link, DFm and DFHm HL-LHC Cold powering failure modes working group (meeting #14) 10

Conclusions § Considering the most likely air ingress orifice in the SC link, the installed safety elements are adequately sized to avoid any overpressure in the cold powering system. § The above conclusion is valid for DSHx and DSHm. HL-LHC Cold powering failure modes working group (meeting #14) 11

Appendix 12

Pressure drop measurement § Friction factor has been evaluated with raw data at 0. 09 which is in good accordance with litterature for turbulent flow HL-LHC Cold powering failure modes working group (meeting #14) 13