Chiller Piston Compressor


This is a 3D model of a Chiller Piston Compressor.

3D Model Annotations

Chiller Compressor

Chiller compressors are used to compress refrigerant gas. The compressed gas is taken from the chiller evaporator, compressed, then discharged to the condenser. This 3D model shows a reciprocating piston compressor; compressors of the screw, scroll, and centrifugal design, are also quite common.


Refrigeration gas is drawn into the chiller compressor through the suction port.


Compressed refrigeration gas is discharged at a higher pressure through the discharge port.


The reciprocating piston compressor is one of the most common chiller compressor designs used today. A chiller compressor will usually have between one to three pistons, with each being installed within a cylinder liner. A piston consists of a cylinder-shaped body, with piston rings installed around the main body (the piston rings are used for sealing the space between the piston and cylinder liner). Pistons move linearly within their cylinders, drawing refrigerant gas into, or discharging refrigerant gas out of, the cylinder.

Suction Valves

As the piston moves away from the suction and discharge valves, it draws refrigerant gas into the cylinder; this is referred to as the ‘suction stroke’. When the cylinder volume is occupied completely by refrigerant gas, the cylinder is said to be ‘charged’.

Discharge Valves

Once the cylinder is fully charged, the piston begins moving towards the suction and discharge valves. As the piston moves, it compresses the gas. At a designated pressure, the discharge valves open and the compressed gas is discharged from the cylinder. Compared to the suction pressure, the discharge pressure is higher.

Sight Glass

Reciprocating machines (linear and rotary) almost always require some form of lubrication to reduce and remove the heat generated between the machinery parts. Chiller compressors are usually lubricated using some form of synthetic or mineral oil, but bio-degradable oils can also be used. A sight glass allows personnel to visually check that the oil level is sufficient for adequate lubrication to occur. Smaller compressors are splash lubricated, whilst larger compressors require dedicated lubrication systems. For special applications, compressors may require no oil for lubrication (‘oil free’ compressors).


The casing houses the eccentric shaft (similar to an engine crankshaft), piston(s) and bearings.


A 3-phase alternating current (AC) induction motor is used to rotate the chiller compressor eccentric shaft. The motor may be a direct on/off motor or controlled by a variable frequency drive (VFD).

Encyclopedia - saVRee