Airwel Enterprises specializes in providing reconditioning of all types of chiller compressor

A chiller typically uses one of four types of compressor:

➤ Reciprocating compressor
➤ Scroll compressor
➤ Screw compressor
➤ Centrifugal compressor

Reciprocating compressors:

These type are becoming less common because newer, more efficient, technology has been replacing it so these are slowly being phased out in commercial refrigeration at least. It’s still quite popular in industrial refrigeration. These are very strong and reliable compressors which seem to just work forever with the right maintenance. There are a lot of moving parts though so they can be expensive to operate.

In reciprocating types the refrigerant will often pass over the electrical motor to proving cooling to the electrical coils and then head into the compression chamber. The compression chamber is simply a number of piston and chambers which the refrigerant will flow into. The piston is on a crank which moves it up and down. As it moves it will compress the refrigerant into the chamber and at a timed interval the refrigerant will exit at a high pressure.

Scroll compressor:

The scroll compressor is used mostly on air cooled chillers but you can also find them on water cooled. Usually one compressor isn’t enough to meet the cooling load so several will be joined together in a bank. In the example above the blue cylinders under the chiller are the compressors which are joined to form a bank.

With these type of compressors, the refrigerant usually enters via the bottom and is fed into the compressor discs. One disc will be stationary whilst the other is rotated to compress the refrigerant into a tighter space. The refrigerant is forced around the spiral as the disc moves which causes it to compress, it will then leave via the top and head to the expansion valve.

Screw compressors:

Screw compressors are used for both water cooled and air cooled chillers. With water cooled type the compressor is on top of the chiller and with air cooled type the compressors is under the chiller. Indoor water cooled chillers will often be insulated whereas air cooled may not be. This type takes the refrigerant off of the evaporator and passes through into the compressor. Inside the compressor are two interconnecting screws.

The refrigerant will enter into a void between the two screws, but as the screws rotates they push the socket of refrigerant further into the compressor and squeeze it into a small space. The refrigerant will exit at high pressure high temperature and flows to the expansion valve.

Centrifugal compressor:

The centrifugal type compressor looks a lot like this and is quite easy to spot as the compressor is above the chiller with a large volute shaped pipe curling around into the condenser.

The refrigerant flows in through the suction line, hits into the the centre of the impeller where it will be directed by the blades. The blades rotate and that imparts an angular velocity onto the particles of the refrigerant. This angular velocity makes the refrigerant particles fly out at high velocity, in all directions, and collects in the volute (the outer curl) where it increases in pressure from the kinetic energy, it then passes down into the condenser. This type of compressor/chiller is a very common set up for a central plant in large buildings.