Tutorial
Modeling of Cryogenic
Systems in EcosimPro
Benjamin BRADU
CERN, EN-ICE
10 &11 March 2011
Contents

Introduction

Presentation of the Cryogenic Library
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Practical hands-on
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Warm Compression Station
Cold-Box @ 4.5 K
Dewar with Cold-Compressor
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Tutorial objectives

Simulation of a warm compression station (WCS)

Get familiar with the cryogenic library
 Understand how to build a “good” model
 Realize the entire modeling using the cryogenic library
 Perform different simulations
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Simulation of a refrigerator
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Connect compression station to an existing cold-box model
Simulate a complete cool-down
Simulate a pulsed load and a turbine stop
Connection with a Dewar and a cold-compressor
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Modeling cryogenic systems : Why ?

Optimization
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Control optimization
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In term of stability, reliability, robustness
 In term of cost
Process Optimization
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Virtual commissioning
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Test control systems off-line in advance
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Check PLC Programs, starting/ending sequences
Check Supervision systems
Real-Time simulator for operator training
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THE CERN
CRYOGENIC LIBRARY
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Cryogenic Library for EcosimPro
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Library “CRYO_CERN”
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Made for CERN cryogenic systems
Use only Helium as cryogen (for the moment)
Made for large-scale systems
Made to simulate process behaviors
Ready to be linked with CERN control systems
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CRYO_CERN components
Helium port
P, h, m
Helium
Thermodynamic
properties
(HEPAK tables)
EcosimPro
Library
CRYO_CERN
Material
Properties
Stainless steel 304L
Aluminum 6061 T6
Copper
Hydraulic components
Storage components
- pipes
- Phase separators
Thermal components
- Valves
- Turbines
-Screw compressors
-Hydrodynamic compressors
Calcul : P, hout
-Thermal loads
-Heat Exchangers
Calcul : hout, Pout, min
Calcul : m, hout
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Interconnections between components
Rule 1
Hydraulic component
Between 2 storage components
Rule 2
Thermal component in series or
between a storage component and an
hydraulic component
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Storage components
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Flow components
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Thermal components
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Sources, Sinks and Sensors
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Example in EcosimPro
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TUTORIAL :
WARM COMPRESSION
STATION
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Process description

Warm compression station
 Compress warm helium from 1 bar to 13 bar (300 K)
 High Pressure (HP) must remain stable around 13 bar
 Low Pressure (LP) must remain stable around 1.05 bar
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What we model
 Helium
 1 Compressor
 3 Gas Volumes (HP, LP, Buffer)
 3 Controlled gas valves
 1 Gas Mixer
 3 PI controllers
PT199
ORS
PT
HP
CV180
CV100
B
C1
CV189
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What we neglect
 Oil Removal System
LP
PT
PT100
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New project and library in EcosimPro
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Open EcosimPro V4.8
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Create a New Workspace
 File New Workspace
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Open libraries “MATH”, “PORT_LIBS”, “CRYO_CERN” and “PLC”
 File  Open  Library  choose .elb file
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Create a new library “CRYO_TUTORIAL”
 File  New  Library
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Create a new schematic “CS” in your library (Compression Station)
 In Schematic View: File  New Schematic
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Schematic building
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To build a complete model before simulation:
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1- Build process itself with sensors but without control. Add also
Source/Sink or Inlet/Outlet ports if necessary
2- Add control components inside the model
For each component:
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Drag and Drop component to your schematic
Double click on your component and:
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Give a name
Fill-in parameters according to the excel specification for the model
Connect it to other components if necessary
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Compression station in Schematic View
1- Process with sensors
Ideal Compressor
Sensors
Discharge/Charge valves
(link to buffer)
Bypass valve
Pipes
Boundary
conditions
Initialization of the model : 3 bar and 300 K
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Control Components
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Add special components from the library “PLC” to manage
the control of the model
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Add components “analog” to drive analog actuators
Add components “PIDFF” for PID control loops
Add AI/DI/AO/DO if you need exchange signals with an eventual
future external control systems
Add/create any other blocks to perform control tasks
3 Compression Station control loops (PID)
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LP controlled by valve CV139
HP controlled by valves CV180 (discharge) and CV189 (charge)
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Compression station in Schematic View
2- Process with control components (Lib PLC)
HP Control
+/- 0.15 bar
- Analog actuators (ANALOG)
-PID controllers (PIDFF)
-Extra control blocks (HP Set-points calculation)
LP control
Slide Valve
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Partition Creation

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Compile the schematic and check that there is no error
Create a partition from the schematic
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In Code View, select the tab “Partitions” and Righ click on the
schematic ‘CS’  New partition
Select default boundaries

Set-points of controllers
 Analog actuators not controlled
 Source/Sink
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Experiment creation
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Create new experiment in your partition
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Simulation view  right click on the partition  New experiment
Define experiment to start the compression station
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1- Start Compressor at min power (CV120=15%) after 100 s
2- Start LP and HP Regulation after 100 s
3- Start Compressor at full power (CV120=100%) after 500s
4- Apply flows of 50 g/s to the source/sink to disturb the operation after 800s
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Experiment definition
Variable declarations
Slide Valve
Set-Points
Sources/Sinks
Compressor start
PID Controllers
Simulation
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Simulation in Monitor
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Compile your experiment and simulate it in monitor !!
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Configure time dependent plots in Monitor :
 Set-Points & Process Values of PI controllers (.AtSP & .PV.signal)
 Valve positions (.s_stem)
 All other signals you want (mass-flows, temperatures…)
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Save graphical configuration
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Run Simulation
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Simulation results : Regulation
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Simulation Results : Actuators
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Simulation Results : Various
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Parametric studies
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You can change model parameters of your model

Setup of parametric studies in experiements
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Study influence of process parameters (Volume, Cv, etc.)
PID tuning
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TUTORIAL :
COLD-BOX
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Connection with a cold box
Copy the schematic “CB.eds” in the following directory and compile it
c:/EcosimPro_4.8.0/USER_LIBS/CRYO_TUTORIAL/Schematics
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Modifications on compression station
Create Input / Output ports and OnOff
valves to connect compression station
to the cold-box
Add a valve to an infinite
source at 7 bars to fill-in the
buffer
Then, save this new schematic on another name and compile it
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Creation of symbols

Create a symbol for the compression station and for the cold-box
 In schematic view  right click on CS (and CB)  Edit
Symbol
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Draw a graphical symbol representing your compression
station and your cold-box with its different I/O ports
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Refrigerator model
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Create a new schematic “refrigerator” in your library
 In Schematic View: File  New Schematic

Connect your compression station to the cold box with 2 pipes for
the HP and LP
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Set sources/sinks for the load
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Cool-down of the refrigerator
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Compile the model of the refrigerator
Create a partition and an experiment “cooldown”
Follow the following sequence for the cool-down:
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Start compression station at 100s
Connect CS to CB (HP and then LP) at 300s
Start Regulation PC290, TC260 and LC270 just after
Run Compressor at full power at 500s
Start Turbines at 600s
Wait until Lhe in phase separator : around 10h (38 000s)
Fill-in buffer at 45 000s
Save the state of your model in a file when steady state is reached (70 000s)
Simulation should take around 7 min to simulate 20h.
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Cooldown Experiment : Boundaries
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Cooldown Experiment : Body
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Cooldown results : CS
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Cooldown results : CB
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Cooldown results : Turbines
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Cooldown results : Cold-end
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Simulation of a pulsed load
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Create new experiment “pulse”
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Restore the state saved in previous experiment
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Re-init the time at 0
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TIME = 0
Apply a heat load of 100W after 500s
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
RESTORE_STATE("../cooldown/state_70000.rpt")
CB.LOAD.PosR.signal[1] = 100*step(TIME,500)
Simulate 10000s
Launch Monitor to run the simulation
Restore graphical configuration of the “cooldown”
 Save the current graphical configuration
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Simulation result of a pulsed load
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Simulation of a Turbine Stop
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Create a new experiment “T_Stop”
 Restore the state reached at the end of cooldown
 Pass all turbine controllers to tracking modes
 Input valve should go to 0% and brake valve to 100%
 Restart all turbine regulations
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Simulation result of a turbine stop
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TUTORIAL :
COLD-COMPRESSOR
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Load schematic

Create new schematic “Load”
Heater to ensure a
minimum massflow to
stay in operation
ranges
Input valve to control
the dewar level
Control box to
compute minimum
massflow in coldcompressor
Cold-compressor
To control the Dewar
pressure
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Cold-Compressor

Cold-Compressor design point :

N_d = 500 Hz
 Tin_d = 6 K
 Pin_d = 0.4 bar
 m_d = 0.01 kg/s
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Based on CC pressure field : pr = f (mr)
Iso-lines have to cover all operation ranges (from Nr=0 to Nr=1.2)
Cold-Compressor Pressure Field

Need to perform real tests on machines with sensitive sensors to
have a goo pressure field (especially at low speed).
Surge Line
Choked Line
Iso-speed Lines
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Cold-Compressor Control
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Create a file “CC_Control” in your library computing the massflow
in order to to follow a predefined trajectory in the pressure field

Generate symbol for the component
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Simulation of the load alone
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
Create partition
 Select LineA.P, LineA.T and LineB.P as boundaries

Create experiment
 LineA.P = 1.2 bar
 LineA.T = 4.5 K
 LineB.P = 1.2 bar
 Start regulation on LC840 (60%) after 500s
 Start regulation FC840 after 1000s
 Start regulation PC840 1 bar  0.8 bar  0.6 bar  0.4 bar
 Put a load of 50W after 25000s
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Load Alone experiment
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Simulation results with Load alone
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Simulation results with Load alone
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Simulation results with Load alone
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Pressure Field during simulation
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Load with cold-box
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Create new schematic with the load :
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Experiment Cold-box + load
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Simulation results load+CB
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Simulation results load+CB
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Simulation results load+CB
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Simulation results load+CB
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