ALICE TRD AND TPC THERMAL SCREEN COOLING SYSTEMmarin/prr_trd/...Cooling is provided to each...

ORGANISATION EUROPEENNE POUR LA RECHERCHE NUCLEAIRE EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH

CERN-ST/CV-2003-??? ?? February 2003

ALICE TRD AND TPC THERMAL SCREEN COOLING SYSTEM

M. Pimenta dos Santos

Abstract

This document outlines a design proposal for the external cooling system of the Transition Radiation Detector and the TPC thermal screen. For p-p collisions the total power dissipated by the TRD is approximately 55kW. A residual percentage of this heat needs to be removed by a thermal screen in order to ensure an uniform temperature map on the TPC side. The overall design of the cooling system, including piping to and from the detector, plant operation, controls and leak detection are examined. A complete list of components, costs and required manpower is also presented.

Miguel A. P. dos Santos 21/09/2003

Index 1.Introduction 3 2.Cooling Circuits Design 3

3.Cooling Plant Design 3.1 Plant description 4 3.2 The leakless or sub-atmospheric mode 6 3.3 Temperature regulation 7 3.4 Cooling System Operation and communication with ECR and TCR 7 3.5 Cooling plant layout drawings 10 4.Responsibilities and resources 4.1 Responsibilities 11 4.2 Cost estimation 11 Appendix I: Estimation of pressure drop along one MCM cooling circuit 13

TPC Cooling System of 13


1. Introduction

The ALICE Transition Radiation Detector (TRD) aims at providing electron identification at momenta above 1 GeV/c. The segmentation of the TRD follows that of other ALICE detectors, leading to 18 super-modules, each covering 20 degrees in azimuth and aligned along the z direction. Within each super-module, heat is dissipated by a variety of components, the main heat source being the multi-chip modules (MCM). An estimated 55 kW is dissipated for the whole TRD when running with p-p collisions.

The interface with the TPC is of particular interest as the temperature map there must be kept as uniform as possible around 20ºC. An actively cooled thermal screen is introduced between the two detectors aiming at removing any residual heat not taken away by the TRD cooling and smoothing out temperature differences at the TPC boundary.

The cooling system described herein comprises a water cooling and de-ionization plant, its controls and all the piping to the detector.

Figure 1 – Cross section of TRD detector within the ALICE space frame

2. Cooling Circuits Design

Cooling is provided to each individual super-module as shown in Fig.2 with inlets on RB26 side and outlets on the opposite side. The thermal screen follows the same segmentation as the TRD, i.e. one screen per super-module. Each screen is made of 5 panels cooled in parallel, as shown in Fig.3.

The nominal flow rate is 1.5m3/h per super-module and 300L/h per thermal screen. This value was calculated in order to limit the pressure drop within a super-module and enable the so called leakless operation mode (further details in Appendix I). Water temperature at the super-module inlet can be adjusted to any value between 16ºC and 18ºC. The expected water temperature rise (assuming ~3kW heat dissipation per super-module cooled with full efficiency) is less than 2ºC.

The thermal screens are meant to remove just the residual heat from the super-modules and smooth out the temperature map on the TPC side. Consequently, the water temperature at the screen inlet should be just under 20ºC, i.e. the temperature aimed for the TPC volume. Assuming a residual heat of 10% from the super-modules, the power to be removed by one screen is approximately 300W. This would lead to a water temperature increase of 0.8ºC.



Figure 2 – TRD super-modules cooling circuits. Left: Supply pipes layout around the TRD right: Cooling of one TRD super-module.

Figure 3 – Thermal screen cooling circuits. Left: Supply pipes layout around the TPC end-cap right: Cooling of one screen

3. Cooling Plant Design

3.1. Plant description A diagram representing the cooling plant as well as some of the piping to the detector is shown in

Figure 4 and some components are identified in table 1. The plant consists of a reservoir large enough to contain all the water in the installation (27), a pump (9), one supply manifold for the thermal screen, one supply manifold for the TRD and one common return manifold for both. Given the difference in water temperature required for the super-modules (~16ºC) and the thermal screen (~20ºC), each supply manifold will have its own heat exchanger connected to the ST/CV mixed water network (12 and 13). All 36 circuits can be temperature and flow adjusted. Temperature regulation is done via individual heaters (17 and 18) on the supply manifolds. These heaters are PID controlled using a temperature sensor (14f) immediately downstream as a feedback signal (see section 3.3 for details). Flow adjustment is done manually on balancing valves (21 and 22) during the commissioning of the system, in order to ensure that all circuits get the right flow despite of varying pipe length between the plant and the super-modules or screens. A PID controller adjusts the pump speed via a frequency inverter in order to keep a constant pressure in the supply manifold despite of the number of circuits in service at any given moment. Another PID controller adjusts the flow of mixed water via the 3-way valves (15 and 16) in order to maintain a constant temperature (14d and 14e) at the heat exchangers outlets. All regulation loops and the plant control is done by a Programmable Logical Controller (PLC). A fraction of the total flow (~5%) is by-passed through a mixed bed de-ionizer (11) and its conductivity measured (35).



19

14f

21

1a

TRDSupply manifold

18 outlets

Thermal screenSupply manifold

18 outlets

25a

Compressedair

23a

29b30

28

1500L/h @ 16~20oC TRD supermodule

RB26 side RB24 side

300L/h @ 18~20oC

Thermal screen

17

20

22

18

6

5

4

3a

2a

24

27

26

23b

14e

Return manifold36 inlets

Flow rate: • TRD: 18× 1.5m3/h • Thermal Screen: 18×0.3 m3/h

Total flow: 32.4 m3/h +5% by-passed demin. Unit. ≈34m3/h

Total heat to be removed: ~ 55 kW Total Volume of water in the installation: ~2000L Installed Electrical Power: • Pump: 11kVA • Heaters TRD: 18 x 700VA • Heaters Screen: 18 x 3.5kVA

Total Power: 76kVA

Range of available water temperature at the Heaters outlet:

• Super-modules: 16~18ºC • Screen: 18~20ºC

Mixed Water Consumption: TRD Heat exchanger : ~32..5m3/h Screen Heat exchanger: ~4.5m3/h

Total consumption: 37m3/h

14d

13

15

Mixed water

14b

12

16

14c

93b

10

8

2b

C

1b

35

29a

25b 11

3132 33

34

Figure 4 – TRD and Thermal Screen Cooling System

Table 1 – Identification of some components in Figure 4

item Description item Description 1a, 1b Pressure relief valve 14a,b,c,d,e,f Temperature Sensors 2a, 2b Manometer 15, 16 Mixed water Regulation Valve 3a, 3b Pressure transmitters 17, 18 Heaters 4 Ultra sound Level transmitter 19,20,24, 25a,b Pneumatic shut off valves 5 Vacuum pump 21, 22, 31 Balancing Valves 6 3-way Electro-valve 23 a,b Schrader valves 7 Drain valve 26 Visual Level 8 Butterfly Valve 27 Reservoir 9 Circulator Pump 28 Pneumatic distribution array 10 Strainer 29a,b Pressure switch 11 Mixed bed de-ionizer 32,33,34 Flowmeters 12, 13 Heat Exchangers

35 Conductivity transmitter

14a7



3.2. The Leakless Operation Mode1

Consequences of a leak occurring inside the detector are obviously adverse. The risk of such an event can be eliminated if the hydraulics of the system is such that water pressure within the detector is below atmospheric, i.e.PDETECTOR-INLET ≤ PATMOSPHERIC. This is done by keeping the reservoir (22) below atmospheric pressure by means of a vacuum pump (5), but still at a pressure high enough to avoid cavitation in the pump (9). Pressure drops inside the detector and in the return lines are carefully minimized to obey the following condition:

ghUPPPP RESERVOIRCATMOSPHERILINERETURNDETECTOR ρρ ++−≤∆+∆ 2_ 2

1 (a)

Where 2

21 Uρ (U, flow speed; ρ density) is the dynamic pressure at the detector inlet

And ρgh (h, difference in height; g gravitational acceleration) is the hydrostatic pressure difference between the reservoir free surface and the detector inlet. • Leak Detection Should a leak occur inside the detector or anywhere downstream to the cooling plant, no water will be spilled out. Instead, air will infiltrate into the system and be flushed down the return line, accumulating inside the reservoir. The pressure sensor in the reservoir (3a) will detect the consequent pressure build up and as soon as a pre-established threshold P1 is exceeded, the PLC will immediately switch on the vacuum pump (5) and produce a WARNING message. The vacuum pump will run for a maximum period of 10 minutes.

If the vacuum pump is able to restore the pressure back to the normal operation pressure PN in less than 10 minutes, it will stop pumping, yet the WARNING message will persist, informing the operator that a “small air infiltration ” has been detected. As long as the air infiltration remains small, the pump is always able to restore the normal operation pressure in less than 10 minutes and the system can run ad infinitum with the pressure in the reservoir swinging between PN and P1. In these circumstances the user may decide to engage the leak identification procedure to identify the exact leaky circuit, even though this procedure implies stopping the cooling for a while.

If the vacuum pump is not able to restore the pressure in less than 10 min or if the pressure in the reservoir rises above a second threshold P2, then the air infiltration rate into the system is considered to be important. In this case, not a warning but an ALARM message will be generated by the PLC and the cooling will stop. The PLC will also stop the circulator pump (9) and open the by-pass valves (25a and 25b) in order to start recovering all the water back into the reservoir both through supply and return lines. During this whole process, the vacuum pump stays on. Once most of the water has been recovered back into the reservoir, the user may also decide to engage the leak identification procedure.

A significant part of the installation, from the pump outlet up to the immediate upstream vicinity of the detector inlet, will be above atmospheric pressure. Water spill out will occur if a leak develops anywhere between these two points. In this case, the ultra-sound level transmitter (4) will detect the loss of water in the reservoir and the PLC will produce an ALARM message and switch off the circulator pump, i.e., the cooling will stop. With the circulator pump switched off, the pressure throughout the installation falls to sub-atmospheric and the water spillage will stop. The by-pass valve (25a and 25b) opens and water recovery can then precede both through supply and return sides. The vacuum pump stays on during the process. Once most of the water has been recovered back into the reservoir, the user may decide to engage the leak identification procedure. • Leak identification procedure

This is an automatic procedure to identify and isolate the leaky circuit with the intent to restart the installation without intervention. With all supply and return valves closed and the reservoir at sub-atmospheric pressure, the leaky circuit is identified by successively opening one circuit at a time and monitoring the pressure in the reservoir. Once the leaky circuit has been identified the installation may

1 “Leakless” systems were developed by Michel Bosteels , CERN ST/CV



resume the cooling for all remaining circuits. The whole procedure is triggered by the Experiment Control Room (ECR).

3.3. Temperature Regulation The heat dissipated inside a super-module may vary with time, thus some sort of adjustment needs to

be undertaken on the cooling if the temperature field at the TPC boundaries is to be preserved. The adjustment suggested here is to modify the temperature of the water at the inlet of the super-modules in order to cope with different heat dissipations.

Prior to any physics data taking, the thermal behaviour of a super-module needs to be established experimentally in the form of an empirical relationship between heat dissipation and required water temperature so that in normal running conditions, the ECR will know what water temperature to request from the cooling plant for each individual super-module. The request is communicated from the ECR to the cooling plant PLC where all the PID controllers are implemented. The PID uses as feedback signal the temperature sensor located at the heater outlet and acts on a Solid State Relay which in turns adjusts the heating power. There is of course a long pipe length between the heater outlet and the Super-modules inlet so these pipes are insulated in order to eliminate any thermal disturbance from the surroundings.

Heaters are protected with a thermal switch, to prevent damage caused by accidentally overheating when there is little or no flow.

The outgoing water temperature acquisition is made using a CERN developed card, the ELMB- Embedded local monitor Board – connected to the PLC via CAN fieldbus. Figure 5 depicts the control loop in block diagram language.

Water temperaturerequested by ECR PID

controller Triac heaterWater temperature at

the heater outlet

Pt100

Twater atSupermodule

inletTraveltime alongsupply line

Water temperature atthe heater inlet

EMLBCanbusPLC

Figure 5 – Control loop for water temperature regulation

3.4. Cooling System Operation and communication with ECR and TCR

3.4.1. Plant Status

The cooling plant can exist in 4 different statuses: stop, test, stand-by and run. In order to transit from one status to another, an input is required and/or certain conditions must be verified. Stop status: All power is off. Maintenance or repair operations can be carried out Test status: Testing the plant’s performance and readiness. Filling, emptying and leak testing operations can be carried out.

• Mixed water may or may not be flowing • The plant may or may not contain water • The pressure in the reservoir may or may not be sub-atmospheric



• Pressure and liquid level readings are available • Pneumatic pressure is available so that individual circuits can be shut off for

eventual leak testing. Stand-by status: The plant is water filled and waiting for a RUN order from the ECR

• Return and supply valves are all open (except any previously identified leaky circuit that may remain not repaired).

• Pressure and liquid level in the reservoir is correct. • Circulator Pump is OFF. • Temperature Regulation is OFF. • Liquid level and Pressure monitoring is ON. • Mixed water is flowing at the right temperature and rate. • Compressed air is available and at the right pressure • Emergency by-pass valve is closed

Run status - Cooling is ON

• Supply and return valves are all open • Emergency by-pass valve is closed • Pump is running and outlet pressure regulation loop is ON • Leak surveillance (reservoir pressure and liquid level monitoring) and is ON • Temperature regulation is ON • The detector is being cooled. The experiment may switch the detector on.

3.4.2. Transition between status

Test →Stand-by: only the local ST/CV SCADA supervisor can order this transition Stand-by→Test: only the local ST/CV SCADA supervisor can order this transition. Stand-by →Run: only ECR (experiment control room) can order this transition. However, if the stand-by status was the result of an alarm driven transition from run status, the alarms need to be acknowledged and reset first by the ST/CV supervisory SCADA. Upon ordering this transition, the ECR will have the possibility to set the following parameters:

1. Open/Close the water flow for a particular circuit (as long as the circuit hasn’t been declared out of order).

2. Temperature set-point for each and every circuit Run →Stand-by: this transition can take place as a result of the ECR deciding to stop the cooling to all circuits. The transition may also originate from the PLC as the result of an ALARM and in this case the ECR will promptly receive an alarm message informing of the imminent stopping of the cooling.

3.4.3. Warnings and Alarms

Warnings and Alarms are issued by the cooling plant PLC and transmitted to the Experiment Control Room (ECR) and to the Technical Control Room (TCR).

A warning is issued when a parameter is outside its normal range, but the deviation is not significant enough to stop the cooling. If the deviation becomes significant then an alarm is produced and the cooling plant or part of the cooling plant stops. A warning does not necessarily give rise to an alarm. An alarm always implies ceasing of cooling.



List of Warnings: W1) The pressure in the reservoir is above threshold P1. W2) PID deviation error greater than 0.1°C (set point − outlet temperature>0.1°C) for circuit #N W3) PID deviation error greater than 0.5°C (set point − outlet temperature>0.5°C) at heat exchanger W4) PID deviation error greater than 100mbar (set point − outlet pressure) at pump outlet W5) Circulator pump motor temperature above limit TPM1 W6) Mixed water temperature is above limit TMW1 List of Alarms: A1) Pressure in the reservoir is above threshold P2 or vacuum pump has been running for more that 10 min. A2) Temperature switch has cut off power to heater #N A3) Compressed air failure (pressure insufficient) A4) Liquid pump failure (pressure insufficient at outlet). A5) Circulator pump motor temperature above limit TPM2> TPM1 A6) Mixed water failure (temperature either too high or insufficient flow). A7) Drop of water level in the reservoir.

3.4.4. Communication with ECR and TCR

The role of the TCR, regarding this cooling system is assumed to be to receive alarms and to call the appropriate intervention piquet when required. The piquet is the only entitled entity to reset alarms and allow the system to transit back to run status, upon request from the ECR. This is done through the local ST/CV SCADA supervisor.

The commands to switch on/off the cooling circuits as well as to modify set points go directly from the ECR supervisory SCADA (PVSS) to the cooling plant PLC (see Figure6). The ECR does not have access to low level commands to act on individual pieces of equipment in the cooling system (valves, pumps, etc.).

Cooling plant Status (Stop, Test, Stand-by, Run)

Circuits status (Open, Closed)

Warnings, Alarms

Temperature at the heater outlets

Transition orders Stand-by <=> Run Status

Temperature set point for every circuit

Open/Close circuits

Local ST/CV ScadaSupervisor(Wizcon)

PLC

ECRTCR

Cooling plant Status (Stop, Test, Stand-by, Run)

Circuits status (Open, Closed)

Warnings, Alarms

Cooling plantData Storage

Transition orders Stand-by <=> TestStatus

Alarms ResetDefinition of Set Points for mixed water and

pump outlet pressure PID regulationDefinition of warning and alarm thresholds

Figure 6-Communication with ECR and TCR



3.5 Cooling plant layout drawings Figure 7 represents a preliminary sketch of the cooling plant physical layout. For transportation purposes, the plant is divided in 6 main volumes: TCR supply manifold, thermal screen supply manifold, return manifold, reservoir, rack containing pump + heat exchanger + filter and finally a rack with control (PLC), electrical equipment (triacs, circuit-brakers, frequency inverters etc…) and pneumatic equipment (electro-valves, etc..). Figure 8 shows a more detailed drawing of one temperature regulated outlet.

Figure 7 – Layout of the TRD and thermal screen cooling plant

To detector

From supplymanifold

Heater

Balancingvalve

Temperaturesensor

Ball valve

Figure 8 –Detail of a temperature regulated outlet



4. Responsibilities and resources

4.1. Responsibilities

The cooling plant described in this paper will be assembled, tested and first commissioned by ST/CV at the point 2 surface building by December 2005. Later on, the plant will be installed in the ALICE Experimental Area, connected to the mixed water network and again commissioned by ST/CV. Cables from the rack to neighbouring control equipment (PLC, etc.) are included, cables to other areas should be laid to ST/CV specifications by the experiment. Documentation (schematics, description, user instruction manuals) and the associated controls will be delivered with the cooling system. The PLC hardware is included in the work package. However, the PC's for the PVSS control are to be supplied by the experimental group. ST/CV will assume responsibility for the maintenance of the cooling plant during the LHC lifetime.

A sub-detector expert from the experiment must participate during the commissioning of the cooling system both at the surface building and ALICE cavern.

4.2. Cost Estimation

Table 3 – Components and Materials Cost breakdown Item

(see Fig 4) Description Manufacturer

/model Quantity Unit cost (CHF) Total

(CHF) 1a,b Pressure Relief valves CERN stores 2 75 150

2a,b Manometers CERN stores 2 90 180

3a,b Pressure transmitter Huba Control 2 250 500

4 Ultra sound level transmitter Burkert 1 1608 1608

5 Vacuum Pump KNF 1 680 680

6 3-way electrovalve Parker 1 90 90

7 Drain valve Legris 1 120 120

8 Butterfly valve Zuercher/LUG 1 250 250

9 Circulator Pump Grundfos/CRN 64-3-2 1 6519 6519

10 Filter TECOFI 1 1037 1037

11 Demineralisation Unit 50L Degremont 2 15000 30000

12,13 Nickel brazed Heat Exchanger Swep 2 2460 4920

15,16 Mixed water regulation valve Sauter 2 2110 4220

17 Heater 6000W Dimeca 18 195 3510

18 Heater 1000W Dimeca 18 65 1170

19 Pneumatic Ball valvesDN20 Zuercher/Meca-Inox 18 315 5670


21 Balancing valve DN20 Ribat/TA hydronics 18 48 864

22 Balancing valve DN15 Ribat/TA hydronics 18 44 792

23 Schrader valves M Paulus 72 8 576



26 Visual Level CERN stores 1 120 120

27 Reservoir 2000L Depositos Coballes 1 4000 4000

28 Pneumatic EV array DIMAT 1 2000 2000

29 Pressure switch Huba control 2 95 190



30 Electrovalve Lucifer 1 80 80

31 Balancing Valve Rohr 1 380 380

32 Flowmeter Aquadis Qmax=50m3/h Actaris 1 2000 2000



35 Conductivity Meter Burkert 1 1563 1563

Supply manifold TRD Tecnodelta 1 6000 6000

Supply manifold thermal screen Tecnodelta 1 3000 3000

Return manifold Tecnodelta 1 5700 5700

rack for pump CERN stores 1 800 800

piping, fittings, etc CERN stores 3000

PLC and related add-ons Schneider/TSX 21785 Circuit breakers, cabling etc CERN stores 4000 Frequency inverter Omron 3000

Cabling and accessories CERN stores 4000

Triacs for heaters Radiospares 36 52 1872

Pt100 sensors 42 28 1176

ELMB acquisition cards 1 320

Total cost of material and components: 147’392 CHF

Manpower:

duration (days) cost/hour (CHF) total cost Mechanical Assembly 50 55 22000 Electrical/control design 10 55 4400 Electrical assembly and cabling 20 55 8800 PLC programming 10 55 4400 Preliminary tests at CERN 5 55 2200 Commissioning at surface building point 2 5 55 2200 SCADA Wizcon Programming 5 55 2200 Commissioning in the cavern (including connection to networks, leaktesting, connection to pipes),

10 55 4400

Total cost of manpower: 50 600 CHF




Appendix I

Estimation of pressure drop along one MCM cooling circuit

Pressure drop vs Flow rate

for a 2mm ID pipe

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25

Flow rate (L/h)

Pdro

p (m

bar)

LaminarRe<2000

Transition2000<Re<4000

Length=5.6m

Length=1.0m

TurbulentRe>4000

ALICE TRD AND TPC THERMAL SCREEN COOLING SYSTEMmarin/prr_trd/...Cooling is provided to each...

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