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T--311
1--6
1.5 COOLING CYCLE
The unit operates as a vapor compression system using
R-134a as the refrigerant (See Figure 1-10). The
compressor raises the pressure and the temperature of
the refrigerant and forces it thru the discharge lines into
the condenser tubes. The condenser fan circulates
surrounding air (which is at a temperature lower than the
refrigerant) over the outside of the condenser tubes.
Heat transfer is established from the refrigerant (inside
the tubes) to the condenser air (flowing over the tubes).
The condenser tubes have fins designed to improve the
transfer of heat from the refrigerant gas to the air; this
removal of heat causes the refrigerant to liquify. Liquid
refrigerant leaves the condenser and flows to the filter/
drier (receiver/drier). The filter/drier (receiver/drier)
contains a medium (absorbent) that keeps the
refrigerant clean and dry.
From the filter-drier (receiver/drier), the liquid refrigerant
then flows to the block type expansion valve. The
expansion valve reduces pressure and temperature of
the liquid and meters the flow of liquid refrigerant to the
evaporator to obtain maximum use of the evaporator
heat transfer surface.
The low pressure, low temperature liquid that flows into
the evaporator tubes is colder than the air that is
circulated over the evaporator tubes by the evaporator
fans. Heat transfer is established from the evaporator
air (flowing over the tubes) to the refrigerant (flowing
inside the tubes). The evaporator tubes have fins to
increase heat transfer from the air to the refrigerant;
therefore the cooler air is circulated to the interior of the
vehicle.
The transfer of heat from the air to the low temperature
liquid refrigerant in the evaporator causes the liquid to
vaporize. This low temperature, low pressure vapor
refrigerant then continues through the suction line and
returns to the compressor where the cycle repeats.
1
2
3
4
5
6
7
8
9
10
Ambient Air In
Air In
Cool Air Out
NOTE:
Receiver--Drier will have HPS
installed with Micro--Channel Condensers
1. Compressor
2. Electro-Magnetic Clutch
3. Discharge Line
4. Condenser
5. Filter/Dryer or Receiver/Drier
6. Liquid Line
7. Evaporator
8. Block Valve
9. Thermostat-(Freeze-Up)
10. Suction Line
Figure 1-10 Refrigerant Flow Diagram