A/C Cycle

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.

Refrigerant is the key element in an air conditioning system. R-1234yf can transfer the undesirable heat and moisture from the passenger compartment to the outside air.

The A/C compressor is belt driven and operates when the magnetic clutch is engaged. The compressor builds pressure on the vapor refrigerant. Compressing the refrigerant also adds heat to the refrigerant. The refrigerant is discharged from the compressor, through the condenser and then through the balance of the A/C system.

The A/C system is mechanically protected with the use of a high pressure relief valve. If the high pressure switch were to fail or if the refrigerant system becomes restricted and refrigerant pressure continued to rise, the high pressure relief will pop open and release refrigerant from the system.

Compressed refrigerant enters the condenser in a high temperature, high pressure vapor state. As the refrigerant flows through the condenser, the heat absorbed by the refrigerant is transferred to the ambient air passing through the condenser. Removing heat from the refrigerant causes the refrigerant to condense and change from a vapor to a liquid.

The condenser is located in front of the radiator for maximum heat transfer. The condenser is made of aluminum, which allows rapid heat transfer for the refrigerant. Cooler liquid refrigerant exits the condenser and flows through the liquid line, to the thermal expansion valve.

The thermal expansion valve is located between the condenser and the evaporator. The thermal expansion valve is the dividing point for the high and the low pressure sides of the A/C system. As the refrigerant passes through the thermal expansion valve, the pressure of the refrigerant and temperature is lowered. The thermal expansion valve also meters the amount of liquid refrigerant that can flow into the evaporator.

Refrigerant exiting the thermal expansion valve flows into the evaporator core in a low pressure, liquid state. Ambient air is drawn through the HVAC module and passes through the evaporator core. Warm and moist air will cause the refrigerant to evaporate inside of the evaporator. The evaporating refrigerant absorbs heat from the ambient air and removes moisture. The refrigerant exits the evaporator back to the compressor, in a vapor state completing the A/C cycle of heat removal. At the compressor, the refrigerant is compressed again and the cycle of heat transfer is repeated.

Vehicles equipped with R-1234yf may utilize an IHX (Internal heat exchanger) in the A/C line set. An IHX transfers heat between liquid line from the condenser and the gas from the evaporator. It uses the cold vapor from the evaporator to cool the warm liquid refrigerant before it enters the expansion device, resulting in increased cooling and higher efficiency.

The conditioned air is distributed through the HVAC module for passenger comfort. The heat and moisture removed from the passenger compartment will also change form, or condense, and is discharged from the HVAC module as water under the vehicle.