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DE-102024210890-A1 - Method for operating a refrigerant circuit and temperature control system

DE102024210890A1DE 102024210890 A1DE102024210890 A1DE 102024210890A1DE-102024210890-A1

Abstract

The invention relates to a method (200) for operating a refrigerant circuit (100) comprising a compressor (130) for compressing a refrigerant, a cooler (150) for at least partially cooling and/or condensing the compressed refrigerant, at least one expansion valve (155) for expanding the at least partially cooled or condensed refrigerant, and an evaporator (112) for at least partially evaporating the expanded refrigerant. The method (200) includes determining the current temperature and pressure of the refrigerant, each directly upstream of the at least one expansion valve (155), and controlling (250) the at least one expansion valve (155) as a function of the current temperature and pressure of the refrigerant. Furthermore, a computing unit, a computer program, and a corresponding temperature control system for carrying out the method (200) are proposed.

Inventors

  • Patrick Grau
  • Matthias Heinkele

Assignees

  • Robert Bosch Gesellschaft mit beschränkter Haftung

Dates

Publication Date
20260513
Application Date
20241113

Claims (13)

  1. Method (200) for operating a refrigerant circuit (100) comprising a compressor (130) for compressing a refrigerant, a cooler (150) for at least partially cooling and/or condensing the compressed refrigerant, at least one expansion valve (155) for expanding the at least partially cooled or condensed refrigerant, and an evaporator (112) for at least partially evaporating the expanded refrigerant, the method (200) comprising: Determining (210) a current temperature and a current pressure of the refrigerant, each directly upstream of the at least one expansion valve (155), Controlling (250) the at least one expansion valve (155) as a function of the current temperature and the current pressure of the refrigerant.
  2. Procedure (200) according to Claim 1 , wherein the actuation (250) of the at least one expansion valve (155) depends on the current temperature and pressure of the refrigerant includes: rules (240, 250) of a controlled variable to a setpoint which depends on the current pressure of the refrigerant.
  3. Procedure (200) according to Claim 2 , wherein the controlled variable comprises a specific enthalpy of the refrigerant and/or an enthalpy difference established across the cooler (150).
  4. Procedure (200) according to Claim 3 , furthermore comprehensive. Determine (220) an actual value and/or the setpoint value of the specific enthalpy of the refrigerant or the enthalpy difference as a function of the current pressure and the current temperature.
  5. Procedure (200) according to one of the Claims 2 until 4 , furthermore comprehensive: Determining (230) the setpoint as a function of a specific enthalpy at which a density of the refrigerant has the highest gradient.
  6. Procedure (200) according to Claim 2 , wherein the controlled variable comprises a temperature of the refrigerant and/or a temperature difference established across the cooler (150).
  7. Procedure (200) according to Claim 6 , furthermore comprehensive. Determining (230) the setpoint of the refrigerant temperature or the temperature difference as a function of the current pressure.
  8. Procedure (200) according to Claim 2 , 6 or 7 , furthermore comprehensive: Determining (230) the setpoint of the refrigerant temperature or temperature difference as a function of a temperature at which a refrigerant density exhibits the highest gradient.
  9. Method (200) according to one of the preceding claims, wherein the refrigerant comprises one or more from the group comprising carbon dioxide, propane, propene, ethane and ethene.
  10. Computing unit (120) which is configured to perform all process steps of a process (200) according to any of the preceding claims.
  11. Computer program that causes a computing unit (120) to execute all procedural steps of a procedure (200) according to one of the Claims 1 until 9 to be performed when it is executed on the computing unit (120).
  12. Machine-readable storage medium containing a computer program stored on it according to Claim 11 .
  13. Temperature control system with at least one refrigerant circuit (100) comprising a compressor (130) for compressing a refrigerant, a cooler (150) for at least partially cooling and/or condensing the compressed refrigerant, at least one expansion valve (155) for expanding the at least partially cooled or condensed refrigerant, and an evaporator (112) for at least partially evaporating the expanded refrigerant, wherein the temperature control system includes a computing unit (120) according to Claim 10 exhibits and/or is equipped to carry out a procedure (200) according to one of the Claims 1 until 9 to carry out.

Description

The present invention relates to a method for operating a refrigerant circuit, a computing unit and a computer program for carrying out the method, and a corresponding temperature control system. Background of the invention In refrigerant circuits, pressure and temperature sensors can typically be used to control and/or monitor the operation of the refrigerant circuit. Typically, at least one pressure sensor can be used in a high-pressure area (downstream of a refrigerant compressor) and in a low-pressure area (upstream of the compressor). Typically, at least one temperature sensor can also be used. Depending on the configuration of the refrigerant circuit, additional pressure and/or temperature sensors can be used. Refrigerant circuits can be used, for example, in vehicles to regulate the temperature of the vehicle cabin and/or other vehicle components (especially in battery-electric vehicles, for example, the traction battery and/or the electric drive motor(s)). It is also possible to use a refrigerant circuit as a heat pump to heat one or more components. Using the previously mentioned battery-electric vehicle as an example, the compressor speed (refrigerant compressor) can be varied to achieve the required temperatures of the battery or of the air in the passenger compartment (vehicle cabin). The required mass flow rate results from the necessary cooling capacity (heat flows) required to reach the target temperatures. Another control element in the refrigerant circuit, the expansion valve, can be used to superheat the gaseous refrigerant before the compressor (superheat) or subcool the liquid refrigerant before the expansion valve (subcooling). This regulates the refrigerant and pressure distribution within the refrigerant circuit. Electrically adjustable valves, for example, can be used for refrigerant expansion. To control a refrigerant circuit based on refrigerant pressures, PL control structures with physically based feedforward controllers can be used, for example. To ensure such control and comply with limitations (e.g., component specifications such as maximum permissible pressure), a large number of pressures within the refrigerant circuit must be known. Typically, all necessary pressure values can be determined using pressure sensors. As the complexity of the refrigerant circuit increases, so does the number of required pressure sensors. Typically, an outlet pressure downstream of the compressor is chosen to be high enough to allow sufficient heat dissipation to the environment. In other words, the compressor is controlled pressure-based, taking ambient conditions into account. The expansion valve can also typically be controlled pressure-based, especially in cases where the refrigerant may be in a supercritical state on the pressure side (e.g., CO₂ ). Disclosure of the invention According to the invention, a method for operating a refrigerant circuit, a computing unit and a computer program for carrying out the method, and a temperature control system with the features of the independent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description. The invention employs a method for controlling an expansion valve in a refrigerant circuit (instead of a conventionally used high-pressure setpoint pressure) that takes into account the current temperature and pressure of the refrigerant directly upstream of the expansion valve. This makes the control of the expansion valve less dependent on the specific properties of the refrigerant used and also reduces mutual interference between the controls of the expansion valve and other components of the refrigerant circuit (in particular the compressor and components requiring temperature control). Overall, the invention thus enables a more robust control of the expansion valve that is less prone to oscillation than conventional methods. In detail, the invention proposes a method for operating a refrigerant circuit, wherein the refrigerant circuit comprises a compressor for compressing a refrigerant, a cooler (also referred to as a gas cooler) for at least partially cooling and/or condensing the compressed refrigerant, at least one expansion valve for expanding the at least partially cooled or condensed refrigerant, and an evaporator for at least partially evaporating the expanded refrigerant. The method includes determining the current temperature and pressure of the refrigerant, each directly upstream of the at least one The invention relates to the control of at least one expansion valve based on the current temperature and pressure of the refrigerant. It is understood that in the case of refrigerants that are essentially permanently kept in a supercritical state (e.g., CO₂ ), condensation of the refrigerant is not possible. The invention can be implemented with refrigerants that are partially or completely in a supercritical state, as well as with those that are partially or completely in a subcriti