cooling for BGV modules trying to collect information toward a specification document Mostly of the cooling system, i.e. chiller+transfer line with given loads (not specifying the module cooling interface, which is considered fixed, designed by EPFL) thanks to Petr Gorbounov see also his contribution in https://indico.cern.ch/conferenceDisplay.py?confId=283751

Help from EN-CV ? Talked to Michele Battistin (18 dec 2013) They have no resources for integration/installation on short notice But they can help for dimensioning and technical contact with companies They need some specs: cooling strategy, a sketch, acceptable T over modules, operating temperature at detector, acceptable temperature gradient over transfer line, pressure drop at detector (pipe diameter, series or parallel ?) Integration: I. Muttoni Note: Julabo chiller is good, must however ask perhaps for special pump (depending on required flow)

BGV module dry air in/out fiber mats electronics/flex ~26cm cooling fluid in/out thermal-insulating box (contains SiPM detectors that need to be kept cold)

BGV system composed of 8 modules, arranged in 2 stations (distance between stations is about 1m)

transfer line

Side view inter-tunnel connecting hole

transfer line request to be measured in lab as soon as possible General: Single phase liquid cooling Type of fluid: 3M NOVEC 649 or similar (radiation! ~ < 100 Gy/year) not creepy, oily, ... Keep SiPM and electronics clean in case of fluid leaks!! SiPM cooling pipe (2 per module): in/out diameter = 3/4 mm, 378 mm long, copper 16 pipes in total, connected in series or parallel ... expect suggestion from TS-CV Operating temperature (at detector): settable between 20 and -40 C Module inside (SiPM and pipe) is flushed with dry air Stability +/- 1K , gradient < 1K over one SiPM (thus 8K over one SiPM row ?) Assume 20 W heat load per module ? (conservative) dominated by heat leaks (insulation) Transfer line: Transfer line must be fixed in place, before closure of machine (2014) Goes from near detector to just outside the connecting hole Total length (3D path) is about 20m (minimum) Temperature drop over transfer line < 10 K (to avoid to low chiller temperature) Insulated, no frost Acceptable pressure drop over transfer line: don't care ? Must be dimensioned such as to allow flux of up to 20 l/min to be measured in lab as soon as possible turbulent flow: >0.5 l/min per SiPM pipe

transfer line: some pictures machine tunnel side (RA43) service tunnel side (UA43) the wall hole

sketch of BGV cooling Thermal insulation up to module! tunnel wall dark box dry air station 1 station 2 module module service tunnel transfer line chiller tunnel wall Thermal insulation up to module!

backup / notes

BGV cooling specs SiPM pipe: innner d = 3mm outer D = 4mm length L = 377.5 mm Assume operating temperature: settable between 20 and -40 C at detector Stability +/- 1K Assume 20 W heat dissipation per SiPM module ? (conservative) to be confirmed by measurement! Max temperature gradient over 1 SiPM: 0.5 K Max temperature gradient over 1 branch: 5K Minimum flow F needed per branch to get turbulent flow: Take NOVEC:  = 1766 g/dm3 at -40C C = 1.1 J g-1 K-1, k = 0.059 W m-1 K-1  = 0.64 cP kin. viscosity = 0.4 cSt http://www.pressure-drop.com/Online-Calculator/ Re = d  v /  = 4  F / (  d ) F = flow = v  (d/2)2 heat transfer coeff: h = ~ 0.023 Re0.8 (k/d) Pr0.33 = ~0.32 W cm-2 K-1 Pr = C ∙  / k = ~120 q = h ∙ A ∙ (Twall - Tfluid ) A =  d L = 36 cm2 Acceptable pressure drop over transfer line: don't care ? d velocity >10000 is turbulent take Re = 8842

LHCb chiller in point 8 (Petr Gorbounov) example called Julabo: do not guarantee it works in radiation (10-100Gy/yr)

chiller, more power example called Julabo: do not guarantee it works in radiation (10-100Gy/yr) get picture at POINT8, what model ?

Coolant C6F14 or NOVEC 649 ? Try NOVEC 649 and get experience!