IP TRONIK EICHSTÄTT GMBH Project Scope: Simulation of car refrigerant circuit with the software GT SUITE and its comparison with real test bench measurements Christian Schwegler 17. October 2016
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 2 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 and development time can be reduced. The basic approach of the simulation is performed using a LCCP(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 3 October 2016 IPETRONIK Eichstätt GmbH
Project Description 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 Slide 4 October 2016 IPETRONIK Eichstätt GmbH
Life Cycle Climate Performance-Evaluation 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. Direct Emissions Refrigerant Leakage Atmospheric Degredation by Refrigerants LCCP Energy Consumption Indirect Emissions Material Manufacturing Refrigerant Manufacturing Material and Refrigerant Recycling Slide 5 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 6 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 7 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 8 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 9 October 2016 IPETRONIK Eichstätt GmbH
Structure of the Simulation Model Condenser Geometry Global Data Height Width Depth Tubes Passes Weight Tube data Slide 10 October 2016 IPETRONIK Eichstätt GmbH
Pressure Drop [bar] 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. An evaluation criterion is the refrigerant s 2.5 pressure drop. - The pressure drop is not constant, but depending on the mass flow. - Automatic calibration of the pressure drop caused significant deviations. 2 1.5 1 Peer Pressure loss for different mass flow - A manual calibration with a multiplier was necessary. 0.5 0 50 100 150 200 Mass Flow Rate [kg/s] Slide 11 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 exchanger predictive correlations were used for calibration. Slide 12 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 and and a 1.05 slope. TXV Parameterization The pressure and temperature at the evaporator outlet is required. The TXV s specific 4-quadrantdiagram is also required. It describes the correlations of pressure, temperature, stroke and mass flow. Slide 13 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 14 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 15 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 16 October 2016 IPETRONIK Eichstätt GmbH
Structure of the Simulation Model Slide 17 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 18 October 2016 IPETRONIK Eichstätt GmbH
Performance of Simulation Deviation from Reality Slide 19 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 20 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 Simulation 40bar 30bar Position of the condenser outlet unknown (only Temperature measured)? 20bar 10bar 1bar Slide 21 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 Simulation 40bar 30bar 20bar 10bar 1bar Slide 22 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 and refrigerant pipes In the simulation the condenser outlet state is always subcooled. In the simulation the evaporator outlet state is always superheated. Note also the refrigerant charge of the system 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. Slide 23 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 Slide 24 October 2016 IPETRONIK Eichstätt GmbH
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