Self-Study Programme 208 Air Conditioner in the Motor ... - Volkspage

[Temperature controlAir recirculation modeWhat do we mean by air recirculation mode?The air conditioner processes two types of air,namely ambient air and cabin air (airrecirculation).In air recirculation mode, the air used for coolingthe passenger compartment is not extracted fromthe outer atmosphere, rather from the vehicleinterior.Therefore, the system only recirculates andcontrols the temperature of the air which isavailable inside the vehicle.Why air recirculation mode?T C[3020100-100Air recirculation modeFresh air mode2 4 6 8 10 12 14 16t [ min ]208_089Air recirculation mode is the quickest way to cooldown the vehicle interior. This is done byrecycling the cabin air, which is always cooler.When heating the vehicle interior, the converseeffect occurs, i.e. the air is heated more rapidly.An advantage of air recirculation is that theevaporator output or compressor drive outputrequired is more than halved in air recirculationmode.In addition to rapid cooling/heating, airrecirculation mode can be used to avoidbreathing in polluted ambient air (unpleasantodours, pollen).Average values for vehicle temperature reduction/increase in the air recirculation and fresh air modesFresh air flapVacuum boxDoes air recirculation mode have any drawbacks?In air recirculation mode, there is no airexchange. The air will be “used up“.Therefore, air recirculation mode should not beused any longer than is necessary, and for nomore than 15 minutes.In air recirculation mode, the atmospherichumidity in the passenger cabin rises due tomoisture released with the air respired by theoccupants. When the dew point of the interior airexceeds the temperature of the windows, thewindows will inevitably mist up.Cabin airAir recirculation flap208_117In the Defrost setting, therefore, airrecirculation mode is automaticallydisabled.Vehicle air conditioningin air recirculation mode – pneumatically operated60