A/C Refrigerant System Operation
REFRIGERATION CYCLEWhen the magnetic clutch (which drives the compressor) is disengaged, the refrigerant in the system normalizes into a vaporized state. Upon clutch engagement, the vapor is compressed and elevated in temperature as it proceeds to the condenser.
The high-pressure vapor enters the condenser where air passing over the cooling fins dispels heat from the refrigerant. With this loss of heat, the vapor liquifies and leaves the condenser as a hot liquid. The pressure between the inlet and outlet lines is approximately constant because of the restriction in the line (fixed orifice tube) between the condenser and evaporator. Any pressure drop across the inlet and outlet is due to circulation in the condenser.
Follow the high-pressure side of the circuit from the compressor to the fixed orifice tube line. The pressure and temperature are shown as 1207 kPa (175 psi) and 55°C (130°F), respectively, for both the vapor into and liquid out of condenser.
The fixed orifice tube separates the high and low-pressure segments of the refrigerant circuit as shown in symbol form.
The vapor then courses through the inlet or suction line to the compressor.
The suction accumulator/drier (illustration) is located between the evaporator and compressor. It allows the liquid leaving the evaporator to vaporize before reaching the compressor, thus preventing excessive liquid refrigerant from reaching the compressor.
Oil-laden refrigerant from the evaporator enters the accumulator through the inlet at the top. Refrigerant vapor rises and enters the vapor return tube, then flows down the tube and to the compressor suction line. The heavier liquid refrigerant tends to flow toward the bottom of the suction accumulator/drier where it has a second opportunity to vaporize before reaching the compressor.
An oil bleed hole near the bottom of the housing allows compressor oil and some liquid refrigerant to flow to the compressor at a controlled rate. A fine mesh filter screen surrounds the bottom of the tube to prevent contamination from plugging the bleed hole.
A desiccant bag is mounted inside the suction accumulator/drier to absorb any moisture that may be in the system.
GENERAL INFORMATION
The A/C refrigerant system is a fixed orifice tube-cycling clutch type. The major components are:
1. Compressor
2. Magnetic clutch
3. Condenser
4. Evaporator
5. Suction accumulator/drier
6. Connecting refrigerant lines
System operation is controlled by the fixed orifice tube and the clutch cycling pressure switch.