Refrigerant Circuit, Function - GF83.40-P-2008KJE
MODEL 453.091/391/491 with CODE I01 (Automatic air conditioning)
Schematic diagram of the refrigerant circuit
Function requirements, general
- Drivetrain operational ("READY" status) or pre-entry climate control active
- Automatic air conditioning switched on
Refrigerant circuit in general
The refrigerant circuit generates the cooling that is required for climate control of the vehicle interior by changing the state of the refrigerant from liquid to gaseous. The coolant temperature of the low-temperature circuit can also be lowered via the high-voltage battery refrigerant circuit (with code V03 (Battery cooling system)), if the coolant temperature of the low-temperature circuit is too high. The refrigerant circuit is regulated by the electric drive control unit (N127). The electrical actuation of the electrical expansion valves takes place via the climate control unit (N22/1). The requests from the vehicle occupants for controlling the climate control of the vehicle interior are read in by the air conditioning operating unit (N20).
Detailed information on the climate control regulation function is available in the function description "Climate control regulation, function". Detailed information about the coolant circuit and the refrigerant circuit of the high-voltage battery cooling can be found in the separate "Thermal management, function" function description.
The refrigerant circuit for climate control of the vehicle interior essentially consists of the following components:
- Electric refrigerant compressor
- Condenser
- Accumulator (drier)
- Electric expansion valve (vehicle interior)
- Evaporator
The individual components of the refrigerant circuit are interconnected through hoses and pipelines and form a closed system.
The refrigerant circuit is made up as follows:
- High-pressure side
- Low-pressure side
High-pressure side
If the air conditioning (refrigeration system) is switched on via the air conditioning operating unit (N20), the electrical refrigerant compressor is switched on and regulated by the electric drive control unit via the electric drive LIN. The air conditioning system can also be switched on via the "Pre-entry climate control" function. The electrical refrigerant compressor draws in the gaseous refrigerant from the evaporator, compresses it, whereby it is heated, and delivers it to the condenser.
The compressed, hot refrigerant is cooled in the condenser by the passing flow of air or the outside air drawn in by the fan motor (M4/7).
On reaching the pressure-specific dew point temperature, the refrigerant condenses and changes in terms of its physical state from gaseous to fluid.
The refrigerant then flows into the accumulator (drier). While it is flowing through the fluid reservoir, moisture is removed from the refrigerant, vapor locks are separated and any mechanical impurities are filtered out in order to protect the downstream components from these. The cleaned refrigerant then flows to the electrical expansion valve (vehicle interior). The electrical expansion valve (vehicle interior) consists of the expansion valve itself and an electric solenoid valve, which is located in the high- pressure line upstream of the expansion valve (vehicle interior) and controls the flow of refrigerant to the expansion valve. The electric solenoid valve is open when de-energized. The liquid refrigerant under high pressure can flow to the expansion valve, which injects it into the evaporator (vehicle interior).
Low-pressure side
The liquid refrigerant decompresses in the evaporator and changes its physical state from liquid to gaseous. The evaporation heat required for the evaporation is removed from the blow-by air at the evaporator fins, cooling it down in the process. The refrigerant, which is now completely gaseous, is drawn in and compressed again by the electric refrigerant compressor.
The cooled air is led to the interior of the vehicle by actuating the blower motor (M2).
To prevent the evaporator from icing up, the power of the electric refrigerant compressor is reduced or it is switched off by the powertrain control unit if the evaporator temperature drops below a certain level. The temperature at the evaporator is recorded by the evaporator temperature sensor. The signals of the evaporator temperature sensor are read in directly by the A/C control unit.
| Overview of system components for climate control | GF83.40-P-9994KJE |