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16-8
GROUP 16- VENTILATING AND HEATING
(b) SYSTEM CAPACITY
Design of the components of the
system is such as to provide a capacity
potential comparable to any unit pre-
sently
marketed.
Rated capacity of
the compressor is 3! tons at 4,000
R.P.M.
Note that one ton of refrigeration is
equivalent to the cooling effect of
melting 2,000 lbs of ice in 24
hours.
(a)
EVAPORATORASSEMBLY
For the "front end" unit, the evap-
orator assembly contains the evapora-
ting or cooling
coil, blower, motor,
and controls. This assembly is located be-
low the instrument panel in the front
compartment.
Cooled air is discharged into
the cabin through adjustable
louvres.
The evaporator coil is of fin and
tube construction and is made com-
plete with inlet and outlet mani-
folding.
Male fitting
s
(expansion valve inlet and
evaporator outlet) extend through the
dash panel for connection to the expansion
valve in the engine compartment.
Refrigerant is sprayed into the
evaporator coil from the expansion
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FIG. 2- Installation.
valve.
As a suction is created in the
evaporator coil by the action of the
compressor, it allows the refrigerant
entering the coils from the expansion
valve to expand and boil. This causes
an evaporative effect lowering the
temperature in the evaporator coil.
As the warm air is blown across the
coils, it is cooled to a comfortable
level.
(b) EXPANSION VALVE
The expansion valve is a pressure
reducing control which regulates re-
frigerant flow to the
evaporator.
High
pressure freon enters the valve in
the liquid state and leaves as a low
pressure
spray,
being approximately
75% liquid by weight but 25% liquid
by
volume.
Its action is analogous
to the cor:1mon garden hose nozzles
where the hose line is "solid" with
water, but a fine spray is emitted from
the
nozzle.
The expansion valve also senses suction
temperature, thereby actuating the valve.
With rise in suction line temperature
the charge in the bulb expands exert-
ing pressure on the valve, forcing it
to open and allow more refrigerant
to
flow.
With reduced temperature
the charge contracts, relieving
pres-
sure to the valve diaphragm subseq·
uently causing
orifice
ir. valve to
close.
(c)
COMPRESSOR
Fig.
24
The compressor is a -reciprocating
twin-cylinder type driven through a
magnetic clutch, which is belt driven
by a special pulley on the engine
crankshaft. Belt tension is obtained
by positioning of an adjustable idler
pulley. The fuction of the compressor
is to raise the low temperature. low
pressure gas entering from the
eva·
porator (suction side) to a high tem-
perature high pressure gas which is
pumped to the condensor (discharge
side). In this compression process,
temperature of the discharge gas is
raised above that of the condensor air
supply (atmospheric temperature)
,
thereby dissipating heat removed
from the car interior.
The compressor is equipped with
two service
valves.
One is defined as
"discharge" and the other
"suction".
Both are of the "back seat" type used
for service checks. With valve stem
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