C2
Air
Conditioning
System
Manua
I
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----
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Ro/ls-Royce
&
Bentley
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The temperature difference created by these two
media causes a heat transfer from the warm air to
the cold refrigerant liquid. As the liquid refrigerant
absorbs the heat from the air, the refrigerant vaporises
(or
boils) due
to
the low temperature in the evaporator
coil.
The cold, de-humidified air
is
then discharged
through two outlet ducts situated m the rear parcel
shelf
of
the car interior.
Condensation
of
the air moisture simultaneously
occurs with the reduction
of
the air temperature.
This condensation is drained as water
out
of
the
evaporator a,-sembly
by
two drain pipes.
An expansion valve capillary tube strapped to the
evaporator coil outlet
is
sensit[ve to the temperature
of
the circulating refrigerant vapour. The pressure
corresponding to this temperature
is
relayed to a
diaphragm in the valve which opposes a balancing
spring tension. The action
of
these two opposing
forces closes
or
opens the valve port in relation to
the increase or reduction
of
heat absorbed by the
refrigerant vapour beyond the quantity necessary
to complete the vaporisation process.
In this manner, the valve automatically meters the
correct amount
of
liquid refrigerant into the eva-
porator
coil depending upon the degree
of
superheat
exrstmg at the evaporator outlet.
It should
be
clearly pointed
out
that
no attempt to alter the
factory setting
of
the expansion valve should
be
made
unless thorough experience with such adjustment has
been gained.
The refrigerant vapour from the evaporator coil
(bearing the heat from the car interior)
is
then pulled
into the suction side
of
the compressor, compressed
and begins
another
cycle.
Prevention
of
the evaporator coil from icing and
control
of
the
car
interior temperature
is
obtained by
the action
of
a thermostat in the evaporator assembly
which controls a solenoid by-pass valve. The ther-
mostat
is
located on the left-hand side
of
the evaporator
casing and has a manual setting with seven positions.
Normal thermostat setting
is
position
6.
For
in-
sufficient cool air flow across the condenser
or
with
the air delivery volume set
at
a minimum, reduce the
manual setting accordingly. In adverse conditions
as
stated
or
in the cooler, more humid climates it may be
necessary to set the control
at
'O'. A capillary tube
(bulb) from the thermostat
is
inserted adjacent to the
evaporator coil and
is
sensitive to the coil temperature.
As
the thermostat points are 'normally open', reduc-
tion
of
the coil temperature below the predetermined
thermostat setting will cause the points to close.
Fig. 3 Evaporator Unit Installed in Boot
Section
CJ
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