PRE-RELEASE
Air conditioning
| Air conditioning |
The function of the air conditioning is to lower the cabin temperature to a comfortable level during high outside temperatures. The unit can also keep the windows free of mist during damp weather with the fan at low speed.
The A/C unit does not produce cold, it leads heat away from the cabin. In order to do this, a refrigerant or medium with a lower temperature than the air is used since heat always moves from a warmer object to a colder object.
The refrigerant used is a liquid, R134a, that boils and evaporates at low temperature. The refrigerant has a constant relationship between pressure and temperature which means that if the pressure changes, then the temperature changes and vice versa. A condition for this is that the volume is constant.
By letting the refrigerant circulate in a closed system and change its pressure, a temperature change can also be achieved. If the pressure changes sufficiently, and subsequently also the temperature, the refrigerant will evaporate (boil). At the pressure existing in the low-pressure side in the system, the refrigerant is evaporated at approximately 0 - +4°C. The process occurs in the A/C system evaporator.
A condition for the evaporation of the refrigerant is that there is sufficient heat available. The heat is withdrawn from the air around the evaporator. When that heat is absorbed by the refrigerant in the evaporator, the ambient air cools down. In turn, this cold air is directed into the cabin.
The heat absorbed in the evaporator is transported by a compressor to the engine compartment where it is released into the open air via an air-cooled condenser.
| Refrigerant |
A liquid designated R134a is used as refrigerant. R134a boils and evaporates at a temperature of approximately -30°C at normal air pressure. When the refrigerant is evaporated on the evaporator, it absorbs heat from the surrounding air. The cooled air is then directed into the cabin.
R134a is a chlorine-free refrigerant. It does not contribute to the depletion of the atmospheric ozone layer.
