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8.1 The role of air conditioning
We have all felt the discomfort of being too hot in a
car, even in temperate climates.
The only solution until relatively recently consisted in
turning up the ventilation in order to speed up the
circulation of air inside the cabin.
Surveys have shown that, from the physiological
perspective, increasing the ventilation can, to a cer-
tain extent, compensate for a rise in temperature.
For example, a temperature of 24°C in still air is
equivalent to a temperature of 30°C in air that is
moving at 1.5 m/s, with a relative humidity of 50%
in both cases. But this remedy is no more than an
interim measure that quickly becomes insufficient,
as soon as certain temperature and humidity limits
are exceeded.
In reality, even the very best ventilation systems
make no difference above 30°C and 70% relative
humidity. And the higher speed of the air flow often
results in intolerable sensations on long journeys. The
required level of comfort under any climatic condi-
tions can only be achieved with an air cooling system.
The main role of air conditioning can be defined as
follows:
«To guarantee the climatic comfort of the occupants
by treating the air and providing controls that are
easy to use.»
Climate control also fulfills another function: «To
make sure that the visibility through the cabin’s
windows is quite clear.»
8.2 Overview of the air
conditioning system
Vehicles are fitted with air conditioning systems for
purposes of thermal comfort and safety.
The basic principle consists of circulating a flow of
thermally treated air inside the cabin.
The air conditioning system fulfills the following
functions:
g
Treatment and distribution of air: the air circuit
and the air conditioning
g
Production of cold: the air conditioning or A/C
loop
g
Control of the system : the control panel and the
air conditioning Electronic Control Unit (ECU)
Introduction to
air conditioning
systems
8
16
Cold production system :
The air conditioning or A/C loop