Aims The product is an easy to use simscape simulator with simple GUI or HMI allowing to define: - the different configurations of the physical system - the different operating modes: start, stop, load variation - the different defaults or dysfunctions: defaults on sensor, actuator, components - the steady state or dynamic scenario to run in open or closed loop - A quick start with the data of just a nominal point - A possibility to do an automatic scaling of the model R: this Matlab/Simulink/Simscape open model and simulator can be easily modified or customized by the user to define its specific simulator. Operating principles The objective of refrigerant loop is to produce cooling thermal power that is transferred to air or water with a good performance whatever the environmental conditions and to protect the components. A refrigerant loop has 4 main intensive states: the high and low pressure, the condenser sub cooling and the evaporator overheat. The high pressure balance depends on the interaction between the compressor mass flow rate capacity and the capacity of condenser which reduces the volumetric mass flowrate. The low pressure balance depends on the interaction between the evaporator which generates superheated refrigerant mass flow rate and the compressor capacity that removes the mass flowrate. The condenser sub-cooling protects the expansion valve against chocking by expansion of vapor. It depends on the refrigerant mass in the system and mainly in the condenser. This sub-cooling is set up during the loop filling. It varies not too much during the operating point and depends on the condenser energy balance. A bottle allows to maintain the cycle during refrigerant life leakages
The evaporator superheat protects the compressor against liquid bubbles expansion. It depends on the energy balance in the evaporator. It is generally controlled by thermostatic valve or maintained by accumulator. As the COP (coefficient of performance) of the loop is function of the thermodynamic cycle and the intensive variables, it is necessary to control these 4 main intensive states. The dynamic control allows to master the 4 intensive variables (pressure, temperature) and the extensive variables (mass flow rate) which are linked by the component characteristics. Therefore, it is necessary to have 5 main actuators: - the speed of the compressor that acts on the extensive mass flow rate or the compressor capacity if the speed is constrained, - the expansion valve that sets up the evaporator superheat - the refrigerant mass that maintains a sub-cooling at the valve input. - The condenser air mass flow rate that acts upon the high pressure - The evaporator air mass flow rate that acts upon the low pressure. As these actuators act in some limits, it is obviously important to have a consistent component static sizing to obtain the required cooling power in critical conditions. Simulator usages - Parametric study and computation of parametric table for steady state points: definition of mapping of inputs or parameters - Dynamic simulation in nominal/degradation/failures conditions - Easy loop sizing, mainly for condenser and evaporator. - Validation tests: MIL/SIL/HIL - Comparison simulated data with tests data (real tests, reference) - Energy optimization - Pre calibration of controlled laws The simulator functions: - Pre-processor to define the scenario, the parameters and the initial states - Component sizing functionalities - Auto sizing scaling: the intensive variables are unchanged but all the extensive variables are scaled. - Post-processor to visualize the results: on line plot of thermodynamic diagram This model can be integrated in higher level model, for example in Air loop model.
Refrigerant cold loop physical description Elements of the cold loop are: Volumetric compressor fixed capacity: the mass flow rate is function only of the speed of the compressor. variable capacity; in this case the capacity can be internally manipulated (control of low pressure) or externally (control of the outlet evaporator air temperature). The efficiency constitutive laws depend on the compressor capacity. Condenser: -with integrated or separated bottle. -Refrigerant side: 3 zones (overheating, condensation, sub-cooling) -Air side: wet or dry air R: the void rate is not taken into account Evaporator : The functioning of evaporator depends much on the air humidity. Therefore, we consider dry or wet regime to assess the right cooling thermal power. There are several zones: - 2 zones for refrigerant: evaporation and overheating -2 zones air side: wet or dry air. Expansion valve: Several options are existing: Thermostatic valve: the opening area depends of output evaporator temperature and corrections of Text. Controlled valve: the section is controlled to have a defined overheat law at evaporator output to protect the compressor.
Fixed valve: the section is fixed Elements of the air subsystem - Condenser fan - Evaporator fan All these super elements have been developed from the simscape library elements Simulator structure The simulator is composed of modular blocks: 1 Block of protocols or scenarios management 2 Block of defaults 3 Control block of pressure, temperature or power 4 Sensors block: leakages, sensors defaults, actuators blocking, components degradation 5 System synoptic with on line numeric and graphic results 6- Results storage and pre-defined plotting: 7 excel data import/export Cold loop with one Air Evaporator Cold loop with two parallel evaporator ( air or water)
Protocol block Choice of simulation mode: - Sizing: search of functional or dimensional parameters - Steady state computation for one point or for a mapping of N points - Dynamic simulation Choice of open/ closed loop options Choice of environmental conditions Choice of configuration options Following is an example of cockpit:
Default Block This block defines the defaults applied to components, to sensors or actuators: blockage, bias, degradation
Control Block This block implements the control of - Compressor: speed or capacity to realize the low pressure objective Ncp or Vol_Cp as P_LP=set point - Valve section to realize the evaporator superheat Va as OVH_Ev=set point - Condenser fan to control the high pressure max Vfan as P_HP < max Sensor block - Real or virtual sensor. Synoptic Block - Numeric values of all properties in all system plans - On line or off line graphic diagrams and plots
Condenser map : it gives all the parameters and values of components - geometric, functional internal/external fluids parameters, exchanger parameters - air and refrigerant values -Refrigerant Cycle - Air diagram
- Power balance Plots: Protocol: variation of compressor speed and inlet temperature evaporator 1
Control Valve and compressor Points 1 to 8
Similitude : auto scaling of factor 100.
Data Import/Export Parameters import and results export between matlab and excel. All the cases of parametric table are defined in excel sheet and the results are exported in excel file. Refrigerant Package Basic Professional Library Volumetric Compressor, controlled or fixed valve, equivalent condenser evaporator dry and wet air bottle + Compressor (pistons, scroll, palet) + Thermostatic valve + condenser 3 zones + evaporator 2 zones (air or water) + accumulator Model User functional parameter law, basic architecture (one evaporator line) Dry air diagram basic documentation Nominal Theoretical laws for coefficient Two evaporator lines Wet Air diagram Complete documentation + Degradation and defaults
Simulator Limited protocols No identification Energy and mass balance No Excel link Thermodynamic diagram off line Basic synoptic Extended protocol Components identification Advanced Graphic Excel link thermodynamic diagram on line Detailed synoptic Price Prices (Keuros) Basic Professional Library 2 5 Standard Model 3 5 Standard Simulator 6 10 Training / day 1.5 2. Technical Assistance / day 0.8 0.8 Specification of work On demand On demand