Piston compressors

As the piston continues its downward journey, the pressure in the cylinder, in the end fall below the pressure in the suction line. The inlet valve opens, drawing low temperature, low pressure, superheated gas cylinder evaporator. Spring on the intake valve closes the valve when the piston low point of its travel.

The piston moves up, compressing the gas and increasing its pressure and the saturation temperature. Because it takes to compress the gas, overheating gas also increases. Suction valve passing before the pressure in the cylinder, while the exhaust valve passes close at this time the pressure in the discharge line.

As the piston continues its upward journey, the pressure in the cylinder, ultimately, higher than the pressure in the discharge line (hot gas line). The discharge valve opens and the high temperature, high pressure superheated gas comes out of the cylinder in the discharge line on the way to the condenser. In the upper part of his journey piston stop pumping and the discharge valve is closed. Gas volume remains a gap in the cylinder.

Now, let's take a clear look at the compression cycle reciprocating compressors, using a graph of the four steps listed earlier. Each graph shows the pressure in the cylinder compared volume of the cylinder. They will help you understand how the pressure changes as the piston sweeps back and forth inside the cylinder and as valves open and close. This, in turn, help you see how the compressor performance depends on improper maintenance, or other system problems.

Starting once again in the intake stroke, the piston must re-expanding gas in the amount of clearance to the new gas could be used for compression. As the plunger is pulled back, high pressure gas in the amount of clearance undergoes a pressure drop is shown line A-B. You can see on this diagram, that about 20% of a full stroke of the piston rod is currently used, but no new gas entered into a cylinder. It is desirable to keep the skin as possible and as part of the cylinder stroke is used to re-extensions cannot be used to attract new gas. This represents a slight loss in power. If it was possible to build piston compressors with zero gap, will not be re-expansion. Line A-B will fall straight down and 100% of the piston scan would be used for drawing and compress new refrigerant gas. For technical reasons, however, it is impractical to build such a reciprocating compressors. One of the attractive features of " rotary", scroll, screw and centrifugal compressors design lies in the fact that they expel each portion of gas they take, covering new portion of gas at the inlet end instead of re-expanding old gas trapped in the cylinder. This gives them an efficiency advantage over reciprocating compressors.

After the suction inlet valve opens, low-pressure gas enters the cylinder at a fairly constant pressure, as shown on the line B-C.

In this chart, it is assumed that the suction pressure 69.0 pounds per square inch, while the discharge pressure 263.0 pounds per square inch. This is typical for low and high side pressure comfort air conditioning system is removed from R-22. The piston begins its compression stroke on line 100%. The volume of gas, held in the cylinder at the moment is 100% of what it was designed to hold. At this point cylinder pressure equal to the pressure suction, 69.0 pounds per square inch. Curved line C-D shows an increase in pressure as the piston passes through its compression stroke. At point D, the pressure in the cylinder is equal to the discharge pressure, 263.0 pounds per square inch. Volume of the cylinder is reduced to 20%. Up to this point, both valves were closed...