Post on 06-Apr-2018
IP TRONIKEICHSTÄTT GMBH
Project Scope:
“Simulation of car refrigerant circuit with the software GT–SUITEand its comparison with real test bench measurements“
Christian Schwegler 17. October 2016
Slide 2 October 2016 © IPETRONIK Eichstätt GmbH
Table of Contents
1. Project Description
2. Life Cycle Climate Performance-Evaluation
‣ Presentation of assessment criteria
‣ Test Matrix - Society of Automotive Engineers
3. Structure of the Simulation Model
‣ Compressor
‣ Condenser
‣ Heat Exchanger
‣ Thermostatic Expansion Valve
‣ Evaporator
‣ Final Model
4. Performance of Simulation
‣ Overall Result LCCP-Evaluation
‣ Deviation from Reality
5. Conclusion
Slide 3 October 2016 © IPETRONIK Eichstätt GmbH
Project Description
The basic idea:
• Bench tests and vehicle tests are very time-consuming and costly.
• Through the use of simulation software, results can be forecasted anddevelopment time can be reduced.
• The basic approach of the simulation is performed using aLCCP(Life Cycle Climate Performance)-Evaluation.
• The simulation of a refrigerant circuit has several steps.
• Using GT-SUITE v7.5, the individual components of the refrigerant circuit are first modeled and then the entire model is simulated.
• Finally, the results are compared with the real measurement data.
• Evaluation parameter is the COP (Coefficient of Performance).
Slide 4 October 2016 © IPETRONIK Eichstätt GmbH
• Simulation of the refrigerant circuit of the Audi A4, the current fifth generation
• Modeling of all components:Compressor, Condenser, Heat Exchanger, Thermostatic Expansion Valve, Evaporator
• Assembly of the complete model
• Comparison with real test bench measurements using a LCCP-Evaluation
Project Description
Slide 5 October 2016 © IPETRONIK Eichstätt GmbH
Life Cycle Climate Performance-Evaluation
LCCP
DirectEmissions
RefrigerantLeakage
AtmosphericDegredation by
Refrigerants
IndirectEmissions
EnergyConsumption
Material Manufacturing
RefrigerantManufacturing
Material andRefrigerantRecycling
• LCCP stands for Life Cycle Climate Performance.
• The fundamental target is to evaluate a refrigeration system’s equivalent mass of carbon dioxide released into the atmosphere from its manufacturing over its operation until its recycling.
• Thereby, indirect und direct emissions are classified.
Slide 6 October 2016 © IPETRONIK Eichstätt GmbH
Life Cycle Climate Performance-Evaluation
Test matrix with 45 different measuring points
• Introduced by the Society of Automotive Engineers
• Representation of the range of operating conditions of an AC-system
• Each measuring point is defined by
- Compressor speed
- Air temperature at inlet (condenser and evaporator)
- Humidity at inlet (condenser and evaporator)
- Cooling capacity
Measuring point Condenser [Temp. / Humidity] Evaporator [Temp. / Humidity]
1 bis 5 45°C / 25% r.F. 45°C / 25% r.F.
6 bis 10 45°C / 25% r.F. 35°C / 25% r.F.
11 bis 15 35°C / 40% r.F. 35°C / 40% r.F.
16 bis 25 25°C / 80% r.F. 25°C / 80% r.F.
26 bis 35 25°C / 50% r.F. 25°C / 50% r.F.
36 bis 45 15°C / 80% r.F. 15°C / 80% r.F.
Slide 7 October 2016 © IPETRONIK Eichstätt GmbH
Structure of the Simulation Model
Compressor Model
• Externally regulated compressor from Denso
• Stroke control is based on mass flow
• The pipe´s current mass flow is sent to the controller of the compressor via Wi-Fi.
• The system is controlled by a PID controller.
• To operate a speed setting is necessary.
Slide 8 October 2016 © IPETRONIK Eichstätt GmbH
Structure of the Simulation Model
Compressor Model Parameterization
Data for diferent displacement setpoints (10%-100%) can be entered in each Rack Position
Slide 9 October 2016 © IPETRONIK Eichstätt GmbH
Structure of the Simulation Model
Condenser Model
• Condenser from Denso
• Flow Splits to create volumes which connect pipes with condenser
• Calibration of the pressure drop in the condenser with the help of a discharge coefficient
Slide 10 October 2016 © IPETRONIK Eichstätt GmbH
Structure of the Simulation Model
Condenser Geometry
Global Data
• Height
• Width
• Depth
• Tubes
• Passes
• Weight
Tube data
Slide 11 October 2016 © IPETRONIK Eichstätt GmbH
Structure of the Simulation Model
Condenser Parameterization
• Parameterization data should map the widest possible operating range of the condenser, from two-phase currently only be realized with power ,until subcooled outlet states.
0.5
1
1.5
2
2.5
0 50 100 150 200
Pre
ssure
Dro
p [b
ar]
Mass Flow Rate [kg/s]
Peer Pressure loss for different mass flow• An evaluation criterion is the refrigerant´s
pressure drop.
- The pressure drop is not constant, but depending on the mass flow.
- Automatic calibration of the pressuredrop caused significant deviations.
- A manual calibration with a multiplier was necessary.
Slide 12 October 2016 © IPETRONIK Eichstätt GmbH
Structure of the Simulation Model
Internal Heat Exchanger Model
• The heat exchanger´s main task is the heat transfer from the slave to the master side.
• Master = Low pressure side
• Slave = High pressure side
• On the slave side, the refrigerant flows from the condenser into the heat exchanger where it is cooled by the colder incoming flow from the evaporator (Master).
• On the master side, the refrigerant flows from the evaporator to the compressor.
Heat Exchanger Parameterization
Due to two-phase operation points in the heat exchangerpredictive correlations were used for calibration.
Slide 13 October 2016 © IPETRONIK Eichstätt GmbH
Structure of the Simulation Model
TXV Model
In the A4(B9) refrigerant circuit the standard expansion valve has a 1.5ton capacity andand a 1.05 slope.
TXV Parameterization
The pressure and temperature at the evaporator outlet is required.
The TXV´s specific 4-quadrant-
diagram is also required. It describes the correlations of pressure, temperature, stroke and mass flow.
Slide 14 October 2016 © IPETRONIK Eichstätt GmbH
Structure of the Simulation Model
Evaporator Model
• Evaporator from Mahle
• Air is cooled and as the case my be dehumidified while flowing through the evaporator.Condensate is considered in the simulation.
• The two flow splits are used for uniform air distribution up and downstream.
Slide 15 October 2016 © IPETRONIK Eichstätt GmbH
Structure of the Simulation Model
Evaporator Model
• Similarity to the condenser model
• The component is divided in two cores with three areas each (12, 9 and 12 tubes).
• The refrigerant´s flow pattern is of particular importance and must be specified.
Evaporator Parameterization
• Similarity to the condenser model
• Widest possible data range
• Bench data were used
Slide 16 October 2016 © IPETRONIK Eichstätt GmbH
Structure of the Simulation Model
Final Model
• Compressor
• Condenser
• Heat Exchanger
• Thermostatic Expansion Valve
• Evaporator
After completion of modeling and simulation, all system components will be analyzed with GT-POST and the results can be plotted.
Slide 17 October 2016 © IPETRONIK Eichstätt GmbH
Structure of the Simulation Model
Slide 18 October 2016 © IPETRONIK Eichstätt GmbH
Performance of Simulation
Overall result LCCP
• Target is the COP value.
• Its values can be compared with the real measurement values deviations analyzed.
Slide 19 October 2016 © IPETRONIK Eichstätt GmbH
Performance of Simulation
Deviation from Reality
Slide 20 October 2016 © IPETRONIK Eichstätt GmbH
Performance of Simulation
Deviation from Reality
• Sorting of cases by the refrigeration capacity
• With increasing refrigeration capacity at the evaporator,the relative deviation of the simulated COP values decrease exponentially
Slide 21 October 2016 © IPETRONIK Eichstätt GmbH
Performance of Simulation
Analysis of case 45 (relative deviation 45,3%)
• In the real measurement the states at condenser outlet, through the heat exchanger and TXV inlet is two-phase wet steam.
• Different pressure ratio between measurement and simulation.
• Simulated refrigeration capacity is higher than the measurement.
Messung Simulation40bar
20bar
30bar
1bar
10bar
?
Position of thecondenser outletunknown (onlyTemperaturemeasured)
Slide 22 October 2016 © IPETRONIK Eichstätt GmbH
Performance of Simulation
Analysis of case 5 (relative deviation 10,8%)
• Deviating heat transmission resistances of the components may be on reason the system´s COP deviation.
• Better pressure accordance in this case.
Messung Simulation40bar
20bar
30bar
1bar
10bar
Slide 23 October 2016 © IPETRONIK Eichstätt GmbH
Conclusion
General Variance of Deviation
• The relative deviation increases with decreasing refrigeration capacity.
• Different heat transmission resistances of the condenser, evaporator andrefrigerant pipes
• In the simulation the condenser outlet state is always subcooled.
• In the simulation the evaporator outlet state is always superheated.
• Different states at compressor inlet at low load
• Characteristic diagram of the compressor has a single entry state.Its pressure is 3,0bar and its superheat is 10K.
• The simulation quality depends on the input data of the single components.They are essential for a successful simulation and thus the quality of the results.
Note also therefrigerantcharge ofthe system
Slide 24 October 2016 © IPETRONIK Eichstätt GmbH
Conclusion
Own experiences
• Working with GT-SUITE is very easy and comfortable.
• GT-SUITE´s user interface has a clear layout.
• GT-SUITE offers a wide range of options.
• Complex refrigerant circuits can be modeled within short time.
• Difficulty of finding appropriate validation sizes for the individual components
• Dependency of availability of suitable parameterization data
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