An optimal pressure calibration method for a heat pump system

Abstract

This invention discloses a method for optimal pressure calibration of a heat pump system, comprising a preliminary statistical method and a subsequent usage method. The preliminary statistical method includes: Step 1, setting operating boundary conditions; Step 2, setting compressor operating parameters; Step 3, obtaining compressor output parameter information; Step 4, repeating steps 1-3 to obtain an output matrix table under different operating boundary conditions and compressor operating parameters; Step 5, obtaining a MAP table of the optimal pressure of the CO2 heat pump system based on the obtained output matrix table. The subsequent usage method involves obtaining the calibrated CO2 heat pump system pressure of a vehicle by consulting the MAP table of the optimal pressure of the CO2 heat pump system based on the vehicle's current parameters when calibrating the CO2 heat pump system pressure. This invention can find the optimal pressure target from the perspective of CO2 heat pump system operation, and combine the target with the actual operating state to maximize the optimal characteristics of the CO2 system.

Description

Technical Field

[0001] This invention relates to the field of automotive thermal management, and in particular to an optimal pressure calibration method and system for a CO2 heat pump system in a new technology project. Background Technology

[0002] Due to relevant regulations and domestic carbon emission requirements, as well as its excellent performance at low temperatures, CO2 refrigerant has a strong market demand as an environmentally friendly refrigerant. CO2 refrigerant is a low-temperature refrigerant, and its physical properties determine that its operating cycle is a supercritical cycle. Temperature and pressure are separated in high-temperature and high-pressure conditions, and the control strategy for actual system operation needs to be different from that for medium-temperature refrigerants. There is an optimal operating pressure for CO2 systems in actual operation. To ensure that the optimal characteristics of CO2 systems are fully utilized, finding the optimal pressure target value under various operating conditions is the key to control.

[0003] The physical properties of CO2 refrigerant determine that its operating state is supercritical, which distinguishes it from traditional refrigerant systems in terms of system operation and control. However, current thermal management system calibration methods are not applicable to heat pump systems using CO2 refrigerant. For example, the patent publication CN115222097A, published on October 21, 2022, entitled "Calibration Method and Calibration Device for Thermal Management System of Electric Vehicle," discloses a calibration method that includes: integrating CAN basic data into an integrated thermal management system; the integrated thermal management system monitors global variables of vehicle status information in real time; the thermal management device performs thermal management on the functional unit to be calibrated according to a preset program to ensure that the functional unit to be calibrated reaches the target temperature; planning driving routes according to different seasons and operating conditions; executing the planned driving routes; and calibrating the parameter values ​​of the current thermal management device when the heat generated by the thermal management device is equivalent to the actual heat generated, after the functional unit to be calibrated reaches the target temperature.

[0004] Heat pump systems using CO2 refrigerant have an optimal operating pressure point under supercritical conditions. Currently, there is a lack of methods to find the optimal pressure or optimal operating point to ensure the operation of CO2 systems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to realize a method for calibrating a CO2 heat pump system so that the system can operate at the optimal working pressure curve in the supercritical state, ensuring its optimal performance and energy efficiency under various operating conditions, and improving the comfort, economy and reliability of the entire thermal management system.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: an optimal pressure calibration method for a heat pump system.

[0007] This includes the preliminary statistical methods and the subsequent usage methods:

[0008] The preliminary statistical methods include:

[0009] Step 1: Set the working condition boundary conditions;

[0010] Step 2: Set the compressor operating parameters;

[0011] Step 3: Obtain compressor output parameter information;

[0012] Step 4: Repeat steps 1-3 to obtain the output matrix table under different operating boundary conditions and compressor operating parameters;

[0013] Step 5: Obtain the MAP table of the optimal pressure of the CO2 heat pump system based on the obtained output matrix table;

[0014] The method for later use is to obtain the calibrated pressure of the CO2 heat pump system of the vehicle by looking up the MAP table of the optimal pressure of the CO2 heat pump system based on the current parameters of the vehicle when the CO2 heat pump system pressure is calibrated.

[0015] The boundary condition setting dimensions in step 1 include HVAC air volume, HVAC inlet air temperature, ambient temperature, and Cond inlet air velocity.

[0016] Step 1 obtains a working condition combination table with ambient temperature and Cond inlet air velocity as the horizontal axis and HVAC air volume and HVAC inlet air temperature as the vertical axis. Each ambient temperature corresponds to several Cond inlet air velocities, and each HVAC inlet air temperature corresponds to several HVAC air volumes.

[0017] Step 2 involves setting different operating conditions for the compressor under different boundary conditions in step 1, including changing the compressor speed and changing the compressor's EXV opening.

[0018] The compressor output parameters obtained in step 3 are compressor parameter information based on each determined setpoint condition in steps 1 and 2, including compressor discharge pressure and discharge temperature signals, compressor suction pressure and temperature signals, EVA outlet air temperature signal, EVA capacity, and compressor power consumption.

[0019] The output matrix table in step 4 uses the compressor speed and the EXV opening of the compressor as the horizontal axis and the compressor output parameter information as the vertical axis to obtain different compressor output parameter information under different compressor speeds and different compressor EXV openings.

[0020] In step 5, each cell in the operating condition combination table serves as an environmental baseline. Each environmental baseline yields multiple output matrix tables. These output matrix tables are evaluated to obtain the optimal table for that environmental baseline, which serves as the MAP table for the optimal pressure of the CO2 heat pump system for that environmental baseline.

[0021] The subsequent usage method obtains the environmental baseline by matching the ambient temperature and the current airflow velocity of the external air exchanger to the ambient temperature and Cond intake airflow velocity in the operating condition combination table, and matching the current HVAC intake airflow and cabin return air temperature of the vehicle to the HVAC airflow and HVAC intake airflow temperature in the operating condition combination table.

[0022] Based on the optimal pressure MAP table of the CO2 heat pump system under the current environmental conditions, select the most ideal compressor speed and EXV2 control combination, obtain the corresponding optimal calibration pressure of the heat pump system, and execute it.

[0023] This invention can find the optimal pressure target from the perspective of CO2 heat pump system operation, and combine the target to control the actual operating state, thereby realizing the optimal characteristics of the CO2 system. Attached Figure Description

[0024] The following is a brief explanation of the content represented by each figure in this specification:

[0025] Figure 1 To test and simulate boundary relationship diagrams;

[0026] Figure 2 For testing and simulation calculation of operating condition combination tables;

[0027] Figure 3 Output matrix tables for testing and simulation calculations;

[0028] Figure 4 This is the optimal pressure MAP table output from the simulation calculation under example condition 2; Detailed Implementation

[0029] The following description, with reference to the accompanying drawings, details the specific implementation of the present invention, including the shape and structure of each component, the relative positions and connections between the parts, the function and working principle of each part, the manufacturing process, and the operation and use methods, to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention.

[0030] like Figure 1 As shown, under actual operating conditions of the CO2 system, during cooling, high-temperature and high-pressure gas is discharged through the compressor, SOV2 is opened, and the gas enters the external air cooler. Then, it flows into the evaporator through the expansion valve EXV1 to absorb heat through evaporation. After passing through SOV3 and AD, it returns to the compressor. During heating, after the high-temperature and high-pressure gas exits the compressor, SOV1 is opened, and the gas enters the internal cooling system. It passes through EXV3 and the evaporator, is throttled by EXV1, flows through I HX to the external air cooler to absorb heat, and then returns to the compressor through SOV4 and AD.

[0031] This invention relates to an optimal pressure calibration method for CO2 heat pump systems. At the factory, vehicle calibration settings (statistics) are required to obtain corresponding tables. During the initial statistical analysis...

[0032] First, set the boundary conditions for different operating conditions of the external air cooler and the HVAC assembly. The boundary condition setting dimensions include HVAC airflow, HVAC inlet air temperature, ambient temperature, and Cond inlet air velocity. The operating condition combination table uses ambient temperature and Cond inlet air velocity as the horizontal axis and HVAC airflow and HVAC inlet air temperature as the vertical axis. Each ambient temperature corresponds to a certain number of Cond inlet air velocities, and each HVAC inlet air temperature corresponds to a certain number of HVAC airflows. Here, the ambient temperature is set with equally spaced point values, for example, a set of data is obtained every 5 degrees Celsius. When looking up the table, the closest parameter is used. If the current temperature is between two temperatures, the set operation can be followed. For example, if the temperature is 37.5 degrees, it is exactly between 40 degrees and 35 degrees. In this case, the data for 35 degrees will be retrieved by default. Each ambient temperature corresponds to a different Cond inlet air velocity, which is also set at intervals. For example, if the Cond inlet air velocity data is set to 1.8km / h, 2.5km / h, 3.0km / h, and 3.5km / h, then if 4 sets of ambient temperatures are set, there will be 16 columns of data. Similarly, the HVAC inlet air temperature is also set with equally spaced point values. Each HVAC inlet air temperature corresponds to a set of HVAC airflow, thus obtaining a working condition combination table. Each cell of the working condition combination table serves as the environmental baseline.

[0033] Secondly, based on different compressor speeds, the opening degree of different EXVs is scanned. Under different boundary conditions in step 1, different operating conditions of the compressor are set, including varying the compressor speed and varying the compressor EXV opening degree. Then, the compressor discharge pressure and discharge temperature signals, compressor suction pressure and temperature signals, compressor voltage and current signals, and EVA outlet air temperature signals are collected to calculate the EVA capacity and the corresponding system COP value. Combined with varying compressor speed and varying compressor EXV opening degree, an output matrix table is formed under different conditions. Here, it is necessary to determine the compressor parameter information under each environmental baseline, including the compressor discharge pressure and discharge temperature signals, compressor suction pressure and temperature signals, EVA outlet air temperature signal, EVA capacity, and compressor power consumption.

[0034] The output matrix table uses the compressor speed and varying compressor EXV opening as the horizontal axis and the compressor output parameter information as the vertical axis to obtain different compressor output parameter information under different compressor speeds and varying compressor EXV openings. Therefore, there are as many output matrix tables as there are environmental references. Multiple output matrix tables are obtained for each environmental reference. Evaluating these output matrix tables yields the optimal table for that environmental reference, which serves as the MAP table for the optimal pressure of the CO2 heat pump system for that environmental reference.

[0035] Finally, during use, these tables are stored in the vehicle's CO2 heat pump system. During vehicle calibration, when the CO2 heat pump system pressure is being calibrated, the corresponding environmental baseline is obtained based on the vehicle's current parameters. This includes the ambient temperature and current external air exchanger fan speed corresponding to the ambient temperature and Cond intake fan speed in the operating condition combination table, and the current HVAC intake airflow and cabin return air temperature corresponding to the HVAC airflow and HVAC intake air temperature in the operating condition combination table. The calibrated pressure of the vehicle's CO2 heat pump system is then obtained by consulting the MAP table for optimal CO2 heat pump system pressure.

[0036] During refrigerant cooling, the refrigerant operates in a supercritical state within the external air cooler, and during heating, it operates within the internal air cooler. The high-pressure state is typically around 110 Bar, and the temperature is generally between 110 and 150°C. To fully utilize the advantages of CO2 in its supercritical state and to ensure that compressor components can withstand long-term operating pressures and temperatures, the following compressor limits are proposed for cooling and heating conditions: discharge pressure < 120 bar, discharge temperature < 150°C; suction pressure > 10 bar. Based on different operating environments or system operating boundaries, and the required parameter performance values ​​obtained after operation, appropriate operating control parameters, corresponding parameter boundaries, and control and output objects are selected.

[0037] During actual vehicle operation, ambient temperature, vehicle speed, and fan operation constitute the heat exchange environment of the external air cooler. Therefore, ambient temperature and the current air velocity of the external air cooler are used as the working boundary for the outdoor air side. The boundary conditions for the in-vehicle heat exchanger are determined by the HVAC intake airflow and the cabin return air temperature; therefore, these two parameters are used as the working boundary. The operating conditions for testing or simulation calculations are shown in the appendix. Figure 2 .

[0038] According to the operating limit requirements and Figure 1 The required parameters are presented in combination with Figure 2 The operating condition boundary is determined by testing or simulation to calculate the output at different compressor speeds and various opening degrees of EXV. See [link / reference]. Figure 3 ,in Figure 4 The table presents a set of output examples, which are actually output matrix tables; (Organization) Figure 3 The output matrix table selects the air-side heat exchange capacity, outlet air temperature, compressor power consumption, and COP under various environmental conditions. Combined with the actual needs under various environmental conditions (including the needs of the cabin personnel and the battery needs, or both), the most ideal compressor speed and EXV2 control combination under various environmental conditions are selected to form an overall control MAP to support actual calibration requirements and achieve control requirements.

[0039] This invention seeks the optimal pressure target from the perspective of CO2 heat pump system operation, combines the target with the actual operating state to give full play to the optimal characteristics of the CO2 system, and ensures its optimal performance and energy efficiency under various operating conditions by quickly finding the optimal working pressure curve of the CO2 heat pump system in the supercritical state, thereby improving the comfort, economy and reliability of the entire thermal management system.

[0040] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A method for optimal pressure calibration of a heat pump system, characterized in that: This includes the preliminary statistical methods and the subsequent usage methods: The preliminary statistical methods include: Step 1: Set the working condition boundary conditions; Step 2: Set the compressor operating parameters; Step 3: Obtain compressor output parameter information; Step 4: Repeat steps 1-3 to obtain the output matrix table under different operating boundary conditions and compressor operating parameters; Step 5: Obtain the MAP table of the optimal pressure of the CO2 heat pump system based on the obtained output matrix table; The method for later use is to obtain the calibrated pressure of the CO2 heat pump system of the vehicle by looking up the MAP table of the optimal pressure of the CO2 heat pump system based on the current parameters of the vehicle when the CO2 heat pump system pressure is calibrated. In step 5, each cell in the operating condition combination table serves as an environmental baseline. Each environmental baseline yields multiple output matrix tables. These output matrix tables are evaluated to obtain the optimal table for that environmental baseline, which serves as the MAP table for the optimal pressure of the CO2 heat pump system for that environmental baseline. The subsequent usage method obtains the environmental baseline by matching the ambient temperature and the current airflow velocity of the external air exchanger to the ambient temperature and Cond intake airflow velocity in the operating condition combination table, and matching the current HVAC intake airflow and cabin return air temperature of the vehicle to the HVAC airflow and HVAC intake airflow temperature in the operating condition combination table.

2. The optimal pressure calibration method for a heat pump system according to claim 1, characterized in that: The boundary condition setting dimensions in step 1 include HVAC air volume, HVAC inlet air temperature, ambient temperature, and Cond inlet air velocity.

3. The optimal pressure calibration method for a heat pump system according to claim 2, characterized in that: Step 1 obtains a working condition combination table with ambient temperature and Cond inlet air velocity as the horizontal axis and HVAC air volume and HVAC inlet air temperature as the vertical axis. Each ambient temperature corresponds to several Cond inlet air velocities, and each HVAC inlet air temperature corresponds to several HVAC air volumes.

4. The optimal pressure calibration method for a heat pump system according to claim 3, characterized in that: Step 2 involves setting different operating conditions for the compressor under different boundary conditions in step 1, including changing the compressor speed and changing the compressor's EXV opening.

5. The optimal pressure calibration method for a heat pump system according to claim 4, characterized in that: The compressor output parameters obtained in step 3 are compressor parameter information based on each determined setpoint condition in steps 1 and 2, including compressor discharge pressure and discharge temperature signals, compressor suction pressure and temperature signals, EVA outlet air temperature signal, EVA capacity, and compressor power consumption.

6. The optimal pressure calibration method for a heat pump system according to claim 5, characterized in that: The output matrix table in step 4 uses the compressor speed and the EXV opening of the compressor as the horizontal axis and the compressor output parameter information as the vertical axis to obtain different compressor output parameter information under different compressor speeds and different compressor EXV openings.

7. The optimal pressure calibration method for a heat pump system according to claim 6, characterized in that: Based on the optimal pressure MAP table of the CO2 heat pump system under the current environmental conditions, select the most ideal compressor speed and EXV2 control combination, obtain the corresponding optimal calibration pressure of the heat pump system, and execute it.

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