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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017
♦ The hot refrigerant flows with its heat content to the condenser.
Here, the refrigerant dissipates its heat to the surrounding air
via the condenser due to the temperature gradient between
the refrigerant and the surrounding air.
♦ The refrigerant thus acts as a heat transfer medium. As it is to
be re-used, the refrigerant is returned to the evaporator.
♦ For this reason all air conditioning systems are based on the
refrigerant circulation principle. There are however differences
in the composition of the units
⇒ “1.1 System overview - refrigerant circuit”, page 30 .
6.4.2
Comfort
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♦ A basic requirement for concentration and safe driving is a
feeling of comfort in the passenger compartment. This comfort
is only reached by using an air conditioning system, particu‐
larly when it is hot and humid. Of course, open windows, an
open sunroof or increased air ventilation can contribute to
comfort, but they all have certain disadvantages within the ve‐
hicle interior, such as additional noise, draughts, exhaust
gases, unhindered entry of pollen (unpleasant for allergy suf‐
ferers).
♦ A well regulated air conditioning system in conjunction with a
well thought-out heating and ventilation system can create a
feeling of well-being and comfort by regulating the interior
temperature, humidity and rate of air change, regardless of the
external conditions. This must be available whether the vehi‐
cle is moving or not.
Other important advantages of air conditioning are:
♦ Drying of the air in the passenger compartment (humidity in
the air condenses on the cold evaporator and is drained away
as condensate, the air is heated up again on the heat ex‐
changer for heater to a preset temperature, which reduces the
water content in the air and the absolute and relative humidity
is reduced).
♦ Additional cleansing of the air directed into the passenger
compartment (dust and pollen that have made their way
passed the dust and pollen filter, for example, are washed out
by the moist fins of the evaporator and carried off with the
condensation water.)
♦ Temperatures in a mid-range car (for example, after a short
period of driving, ambient temperature 30°C in the shade and
the vehicle in direct sunlight).
With air conditioning Without air condi‐
tioning
Head height
Chest
Footwell
23 °C
24 °C
30 °C
42 °C
40 °C
35 °C
6.4.3
Environmental aspects
♦ Until about 1992, air conditioning systems were equipped with
refrigerant R12. Due to its chlorine atoms, this CFC had a high
potential for destroying ozone and, in addition, a very high po‐
tential for increasing the greenhouse effect.
♦ From 1992, the air conditioning systems of newly manufac‐
tured cars have been successively changed from R12 refrig‐
erant to R134a refrigerant. This refrigerant contains no
chlorine and therefore does no damage to the ozone layer.
Due to the high global warming potential of approx. 1400
(GWP), it may no longer be used in vehicles that are newly
type approved from 2011. The cut-off date for bringing vehi‐
6. Basic technical and physical properties
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