PMT Array Cooling

PMT Array Cooling

Tim

PMT Array Cooling 2

Overview• Cooling System Parameters– Estimate Power Loads• Active components• Extraneous heat sources

– Develop methodology for exploring cooling system parameter space• Flow rate• Pressure drop• Pipe bores

• Control and Monitoring– Strategies– Implementation

15/03/2011

PMT Array Cooling 3

Cooling System Parameters• Working document - “Specifications for the

Cooling System for the NA62 CEDAR Kaon Tagger”

• Considers 2 sides as being separate sub-systems– Chiller/Heater– Interconnect pipe-work– Internal pipe-work, etc..

• System specification driven from a desired inlet-to-outlet bulk temperature rise

15/03/2011

PMT Array Cooling 4

Considerations• Desired temperature rise

and total power defines the mass-flow;– 1g/s cools 4.2W for 1C

• Mass flow, density and tube bore defines volume flow and velocity.

• Velocity defines Reynolds Number.

• Reynolds Number defines pressure drop and HTC

• HTC defines tube wall temperature

15/03/2011

PMT Array Cooling 5

Power Estimate• FE

– 32 PMTs per array– 4 arrays per cooling circuit connected in series– 0.5W per PMT– 16W per PMT array, 64W for four arrays on one side

• Environment– Box dimensions 1.2(h) x 0.6(w) x 0.3(d).

• Area of 5 sides = 2.16sq.m

– Box insulation k=0.05 W.m-1.K-1

– Wall thickness 50mm– Assume external wall is at 40C and internal wall is at 20C– Power = 0.05 x 2.16 x 20 / 0.05 = 47W

• Total Power– 64 (FE) + 47(env) = 107W15/03/2011

PMT Array Cooling 6

Pipe-work Geometry• External Interconnect– Flow and return lines 7m long with a bore of

12mm

• Internal– Heat exchanger: heated length 0.5m per array– Interconnect: 4m in total– Bore: 4, 6, 8mm

15/03/2011

PMT Array Cooling 7

System Properties• Volume Flow– Inversely proportional to desired temperature rise– Independent of tube bore– Flow = 1.54/T lpm

0 0.5 1 1.5 2 2.5 30.1

1.0

10.0

100.0

Inlet-to-outlet Temperature Rise (deg C)

Volu

me

Flow

Rat

e (lp

m)

15/03/2011

PMT Array Cooling 8

System Properties• Pressure Drop– Depends on fluid velocity (strong dependence on

tube bore)

0 0.5 1 1.5 2 2.5 30.00

0.01

0.10

1.00

10.00

4mm6mm8mm

Inlet-to-outlet Temperature Rise (deg C)

Tota

l Pre

ssur

e D

rop

(bar

)

15/03/2011

PMT Array Cooling 9

Draft Chiller Requirements

T rise 0.5deg C 0.25deg C 0.10 deg C

Bore 4mm 6mm 8mm 4mm 6mm 8mm 4mm 6mm 8mm

Flow 3.09 3.09 3.09 6.17 6.17 6.17 15.43 15.43 15.43

Pressure 3.52 0.55 0.17 11.8 1.83 0.57 58.8 9.13 2.83

• Tabulate Flow and pressure for different bores of the internal pipe work and desired temperature rise

• Chiller Specifications (preliminary web-trawl)

Model Power Flow (lpm @ 0 bar) Pressure (bar)Fryka DLK 402 380W @ 30C 4 0.15Grant RC350G 350W @ 20C 15 1.60 (@1 lpm)Neslab Thermoflex 900/P2 900W @ 40C 12.5 (@4.1 bar) 7 barJubalo FC600S 600W @ 20C 15 1.2Cole-parmer WU-13042-07 250W @ 20C 21 0.8Lauda WK 502 600W @ 20C 10 (@1.5bar) 2.2

15/03/2011

PMT Array Cooling 10

Chiller Parameters• Cooling Specification– Cooling Power (W)– Flow Rate (lpm)– Maximum Pressure (bar)

• Control– Set-point stability– Heater Power (W)– PID / remote control– Control Temperature (internal / external)

• Alarm signal (low flow, low level, ….)15/03/2011


Monitoring• DCS Monitoring

– ELMB (ATLAS) – quote from ELMB128 User Guide• “It should be usable in USA15 outside of the calorimeter in the area of

the MDTs and further out. This implies tolerance (with safety factors) to radiation up to about 5 Gy and 3·1010 neutrons/cm2 for a period of 10 years and to a magnetic field up to 1.5 T.”

• Automated reading, archival & presentation in central DCS

– Inputs• 128 floating input (2 wire) channels• Can be configured for DCV, Ohms…• Can be used in pairs for 4-wire RTD (PT100)

• DSS– Detector Safety System

• High level alarms relating to safety ONLY• Independent of DCS15/03/2011


Control• Issues

– Maintain the PMT arrays at a given temperature– Control the heat transfer between the box and the CEDAR

• Options1. Control the PMT array temperatures such that the global temperature of the

box is close to the CEDAR. Provide sufficient thermal insulation to minimise coupling between box and CEDAR.

2. Monitor the CEDAR temperature and control the temperature of the PMT arrays such that the temperature difference between the box and the CEDAR is minimised.

3. Control the PMT array temperatures such that the global temperature of the box is just below the CEDAR. Provide an ACTIVE thermal enclosure between the box and the CEDAR and control the temperature on the CEDAR side to minimise heat flow.

• Need more engineering input to define interfaces between CEDAR and box15/03/2011


Thermal Interfaces• For Option 1 and Option 3 - need to consider

Thermal Interfaces– Option 1: Passive thermal interfaces between PMT

array box and CEDAR• Control of thermal exchange between box and CEDAR

would have to be through adjusting the set-point on the chiller PID

– Option 3: ACTIVE Thermal Interfaces between PMT array box and CEDAR• Control of thermal exchange between box and CEDAR

would be through regulation of the power to the heaters o the active thermal enclosure.

15/03/2011


Thermal Interfaces

• Heat Paths– Box/beam pipe/CEDAR– Box/Support Tube/CEDAR (is steel the right material?)

• NB– Option 3 heat generated on CEDAR side of thermal enclosures will need to be

absorbed by the cooling system15/03/2011


Option 1

15/03/2011


Option 2

15/03/2011


Option 3

15/03/2011


Comments• Option 1:

– Likely to need greatest number of interventions to adjust chiller PID controller

– Needs chiller with in-built heater– Needs high precision chiller set-point & stability

• Option 2:– Highest cooling power requirement– Need to develop fault tolerant PLC /heater sub-system

• Option 3:– Chiller may not need in-built heater– May allow low precision chiller set-point & stability– Complete segmentation of control sub-systems– Needs detailed engineering analysis / design & manufacture of active

thermal enclosure15/03/2011

PMT Array Cooling

Documents

Transcript of PMT Array Cooling