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Refrigerant Circuit With Expansion Valve

WARNING: This page is about a different car, the 2024 Audi SQ7, 2024 Audi Q7, 2023 Audi SQ7, and 2023 Audi Q7. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:

Applies to vehicles with an Electrical A/C Compressor -V470- only with restrictions.

HP- High pressure side of refrigerant circuit.

LP- Low pressure side of refrigerant circuit.

Component Aggregate state of refrigerant Pressure (bar pressure) Temperature in Celsius
-1- Evaporator, from input to output Vapor approximately 1.2 bar (17.4 psi) (1)1 approximately -7 °C (2)2
-2- Expansion valve Fluid, released as vapor approximately 14 bar (203.05 psi) approximately + 55 °C (high pressure side), reduces to -7 °C (19.4 °F) (low pressure side)
-3- High pressure switch / high pressure sensor Fluid approximately 14 bar (203.05 psi) approximately +55 °C
-4- HP-side service connection and -5- receiver/dryer Fluid approximately 14 bar (203.05 psi) approximately +55 °C
-6- Condenser From gas (at input) through vapor to fluid (at output) approximately 14 bar (203.05 psi) From approximately +65 °C (at input) to approximately + 55 °C (at output)
-7- pressure relief valve and -8- A/C compressor, HP-side Gas approximately 14 bar (203.05 psi) approximately +65 °C
-9- A/C compressor, low pressure side Gas approximately 1.2 bar (17.4 psi) (1)1 approximately -1 °C (30.2 °F) (2)2
-10- Pre-volume (not present in all vehicles) and -11- LP-side service connection Gas approximately 1.2 bar (17.4 psi) (1)1 approximately -1 °C (30.2 °F) (2)2
(1) 1- Pressure in refrigerant circuits is maintained at approximately 2 bar (29.01 psi) absolute pressure (corresponds to approximately 1 bar (14.5 psi) positive pressure) by a regulating A/C compressor, despite changing heat transfer and varying engine speeds. However, this applies only within the performance range of the A/C compressor; if the performance limits of the A/C compressor are exceeded, the pressure increases. Refer to PRESSURES, CHECKING .
(2) 2 - Temperature in refrigerant circuits is maintained within the A/C compressor control range by a regulating A/C compressor, despite changing heat transfer and varying engine speeds. However, this applies only within the performance range of the A/C compressor; if the performance limits of the A/C compressor are exceeded, the temperature increases. Refer to PRESSURES, CHECKING .
NOTE:

A/C compressors that do not regulate their output are switched off by the respective control module via the A/C Compressor Regulator Valve -N280- at an evaporator temperature below 0 °C (32 °F).

For vehicles with a A/C Compressor Regulator Valve -N280-, the pressure on the low pressure side is changed by the valve activation.

Temperature and pressure in the refrigerant circuit in vehicles with two evaporators and two expansion valves correspond to those in vehicles with only one evaporator and one expansion valve (parallel switching).

Depending on the version of the refrigerant circuit, a component with an inner heat exchanger may be installed (for example, on the Audi A4 from MY 2008 and on the Audi A5 Coupe from MY 2008, a refrigerant line with an inner heat exchanger). In the inner heat exchanger, the warm liquid refrigerant flowing on the high pressure side releases energy into the gaseous or vaporous cold refrigerant flowing on the low pressure side. This increases the efficiency of the A/C system. Refer to REFRIGERANT LINE WITH INNER HEAT EXCHANGER .

Arrows point in direction of refrigerant flow.

HP- High pressure side of refrigerant circuit.

LP- Low pressure side of refrigerant circuit.

Fig 1: Identifying Refrigerant Circuit With Expansion Valve Overview
GWWA87-10139Courtesy of AUDI
  1. Evaporator
  2. Expansion Valve
  3. High Pressure Switch / High Pressure Sensor
    • There are different versions depending on the vehicle
  4. High Pressure Side Service Connection
  5. Receiver/Dryer
    • There are different versions depending on the vehicle
  6. Condenser
  7. Pressure Relief Valve
  8. A/C Compressor, High Pressure Side
  9. A/C Compressor, Low Pressure Side
  10. Damping Chamber
    • Not present on all vehicles
  11. Low Pressure Side Service Connection
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