period one
Compressor Types
notes
gradually shrinking the volume of the refrigerant. Thus, they are called
In contrast, centrifugal compressors use the principle of dynamic compression, which involves converting energy from one form to another in order to increase the pressure and temperature of the refrigerant. The centrifugal compressor uses centrifugal force, generated by a rotating impeller, to compress the refrigerant vapor.
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Figure 6
Reciprocating Compressor
The first type of compressor to be discussed is the reciprocating compressor. The principles of operation for all reciprocating compressors are fundamentally the same. The refrigerant vapor is compressed by a piston that is located inside a cylinder, similar to the engine in an automobile. A fine layer of oil prevents the refrigerant vapor from escaping through the mating surfaces. The piston is connected to the crankshaft by a rod. As the crankshaft rotates, it causes the piston to travel back and forth inside the cylinder. This motion is used to draw refrigerant vapor into the cylinder, compress it, and discharge it from the cylinder. A pair of valves, the suction valve and the discharge valve, are used to trap the refrigerant vapor within the cylinder during this process. In the example reciprocating compressor shown, the
During the intake stroke of the compressor, the piston travels away from the discharge valve and creates a vacuum effect, reducing the pressure within the cylinder to below suction pressure. Since the pressure within the cylinder is less than the pressure of the refrigerant at the suction side of the compressor, the suction valve is forced open and the refrigerant vapor is drawn into the cylinder.
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