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AIR CONDITIONING
26
11.9 MAIN PARTS OF A.C. SYSTEM
1. COMPRESSOR
: It is the heart of A.C. system
where, low temperature, low pressure vapour
refrigerant is compressed and converted to
high temperature high pressure gas.
2. CONDENSER:
It is the place where heat
dissipation takes place. Hot compressed gas
enters the condenser and is cooled off and
converted into high pressure liquid at the
condenser outlet.
3. RECEIVER DRIER INTEGRATED WITH
CONDENSER
: It serves as a reservoir for
excess refrigerant where it removes any
traces of moisture and filters out dirt in the
system.
4. LINEAR PRESSURE SWITCH:
It is used to
limit pressure conditions in a closed
refrigerant cycle for series / parallel logic.
High Low Pressure Settings: If the system
Pressure reaches impermissible levels i. e. if
the pressure is less than 2 ± 0.2 kg/cm2 or if
the pressure is higher than 32 ± 2 kg/cm2
then the compressor is switched off. This
avoids its consequential damage.
Medium Pressure Settings: Due to these
pressure settings, both the condenser fan and
radiator fan start immediately after the A. C. is
switched ON. Both the fans run at slow speed
until the system pressure exceeds 20.5 kg /
cm2 Above this pressure, both the fans run at
full speed. When the system pressure drops
below 15.5 kg / cm2, both the fans will run at
slow speed.
5. EXPANSION VALVE:
It senses the pressure
of the refrigerant coming into the evaporator
as well as the temperature of the refrigerant
into the evaporator. By sensing the
temperature and the pressure of the gas
leaving the evaporator, the expansion valve
prevents the evaporator from being flooded,
and thereby returning liquid refrigerant to the
compressor.
6. EVAPORATOR:
It serves as a heat
absorption unit. Here it removes heat from
inside the vehicle and dehumidifies it. The
refrigerant enters the bottom of evaporator as
a low pressure liquid. The warm air passing
through evaporator fins causes the refrigerant
to boil; it can absorb large amounts of heat.
The heat is then carried off with the refrigerant
to the outside of vehicle.
7. ANTI FREEZE SWITCH:
It is a temperature
sensing device, which protects the A.C.
systems from damage. It switches off the
compressor when condensed water tends to
form ice on the fins of evaporator. Thus it
maintains the evaporator temperature within a
specified range.
8.
MAGNETIC CLUTCH
:
A magnetic clutch is used to connect and
disconnect the compressor from the engine. Main
components are stator, rotor, and pressure plate.
PRINCIPLE:
When the current is fed to the coil (as shown fig. B
on the right), magnetic force is generated in iron II
which attracts iron I.