Automatic air conditioning refrigerant circuit, function - GF83.40-P-2005FLH
MODEL 212.095/098/298
Function requirements, general
- Automatic air conditioning switched on
Automatic air conditioning refrigerant circuit, general
The refrigerant flow is controlled by the automatic air conditioning control and operating unit (N22/7). The air in the vehicle interior is cooled depending on the setting at the control and operating unit or the rear automatic air conditioning control unit (N22/4) (with code (581) Comfort automatic air conditioning).
The high-voltage battery module (A100) can be cooled if required.
The request to switch on the electric refrigerant compressor is transmitted by the control and operating unit via the interior CAN (CAN B) to the front SAM control unit with fuse and relay module (N10/1). The front SAM control unit transmits the request in vehicles (up to 28.2.13) via the chassis CAN (CAN E) to the CDI control unit (N3/9) (with diesel engine) or the ME-SFI [ME] control unit (N3/10) (with gasoline engine). In vehicles (as of 1.3.13) the front SAM control unit transmits the request via the chassis CAN 1 (CAN E1) to the CDI control unit (with diesel engine) or the ME-SFI [ME] control unit (with gasoline engine).
The CDI control unit or the ME-SFI [ME] control unit transmits the request via the hybrid CAN (CAN L) to the electric refrigerant compressor. The high-voltage battery cooling system shutoff valve is actuated directly by the battery management system control unit (N82/2).
Detailed information about the high voltage battery cooling system can be found in the separate high-voltage system cooling function description.
The automatic air conditioning refrigerant circuit mainly consists of the following components:
- Electric refrigerant compressor
- Condenser
- Accumulator (drier)
- Expansion valve
- Evaporator
- High-volt battery cooling system shutoff valve
- Evaporator shutoff valve
The individual components of the refrigerant circuit are interconnected through hoses and pipelines and form a closed system.
The refrigerant circuit is split up as follows:
- High-pressure side
- Low-pressure side
High-pressure side
The electric refrigerant compressor draws in the cold, gaseous refrigerant from the evaporator, compresses it, whereby it heats up, and delivers it to the condenser. The compressed hot refrigerant is cooled in the condenser by the flow of outside air that has been drawn in by the internal combustion engine and air conditioning system fan motor with integrated control (M4/7). On reaching the dew point dependent on the pressure, 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 flows on to the expansion valve and the evaporator shutoff valve. The liquid refrigerant, which is under high pressure, is injected into the evaporator.
Low-pressure side
The liquid refrigerant decompresses in the evaporator and changes again in terms of its physical state from fluid to gaseous. The evaporation heat required for the evaporation is removed from the air flowing past the evaporator fins or the high-voltage battery, cooling it down in the process. The refrigerant, which is completely gaseous again, is drawn in again and compressed by the electric refrigerant compressor. The air cooled on the evaporator is routed to the vehicle interior.
The evaporator is designed as a coaxial heat exchanger. This increases the cooling output.
To prevent the evaporator from icing up, if the temperature drops below a specific value at the evaporator, the electric refrigerant compressor is switched off by the control and operating unit. The evaporator temperature is recorded by the evaporator temperature sensor.
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