22.09.2015 12:04

Refrigeration Compressors decoded

A refrigerator is by far one of the most remarkable inventions in the history of humanity. The process of refrigeration has not just improved the longevity of our food items, but has facilitated storage, preservation and availability of food throughout the year. It has made sure no fruit or vegetable really goes out of season, and can be accessed as and when the need arises. Given that refrigeration lowers the reproduction rate of bacteria, the rate of spoilage drops down drastically.

Working Process of a refrigeration compressor

Having started out as an ice-making machine in the late 1800s, the mechanics of refrigeration has grown by leaps and bounds over the years. One of the most important principles of refrigeration is that of vapour-compression. It involves absorbing heat from one space, removing it and subsequently cooling that space, eventually rejecting the heat elsewhere. Refrigeration compressor thrives on four components: a compressor, a condenser, a thermal expansion valve and an evaporator.

The refrigerant enters the compressor, is compressed to a higher pressure, which raises its temperature. This hot, compressed vapour reaches a temperature and pressure at which it can be condensed with either cooling water or air. The hot vapour is then made to pass through a condenser, where it is cooled and condensed into a liquid after putting it through a coil or tubes, with cool water/air flowing across. This is where system heat is rejected by the circulating refrigerant, which is lugged away either by water or air.

Different Types of Refrigeration Compressors

There are many types of compressors used for refrigeration. They are divided in either the positive displacement or non-positive displacement category. Positive displacement compressors house chambers that reduce in volume when compressed; the non-positive compressors, on the other hand, have fixed-volume chambers.

The five main compressor types are piston, screw, rotary, centrifugal and scroll.

Piston: It uses a piston and cylinder arrangement to provide compressive force. The reciprocating motion of the piston due to external power compresses the refrigerant inside the cylinder.

Screw: This uses a helical screw or rotor pair, which mesh together to compress the refrigerant between them. It produces high pressure for a small quantity of gas and consumes less power.

Rotary: It has two rotating elements, like gears, between which the refrigerant is compressed. Rotary compressors are considered to be the most efficient.

Centrifugal: This uses the rotating action of an impeller wheel to exert centrifugal force on refrigerants inside a round chamber.

Scroll: It is a quiet, smooth-operating unit with few moving parts and the highest efficiency ratio of all compressor types. It is also more flexible for handling refrigerants in the liquid.

Further information at www.secop.com