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# Compressor

Last updated: July 19, 2024

## What Does Compressor Mean?

A compressor is a device that increases the pressure of a substance (usually a gas) by reducing the volume of the substance.

Compressors are used in many applications, most of which involve increasing the pressure inside a gas storage container, such as:

• Compression of gases in petroleum refineries and chemical plants
• Storage of gas in high pressure cylinders
• Cabin pressurization in airplanes
• Air storage for underwater activities
• Filling tires

Other applications include, but are not limited to:

• Refrigeration and air conditioners
• Rail vehicle operation
• Gas turbines
• Powering pneumatic tools
• Pipeline transport of natural gas

## Corrosionpedia Explains Compressor

The laws of thermodynamics dictate how compressors are able to compress gases. The properties of gases more or less follow the ideal gas law, which relates pressure (P), volume (V), the amount of gas in moles (N) and temperature (T) with a factor R called the universal gas constant. Allowing for deviations in gas behavior, the compressibility factor z is added to the equation to obtain:

PV = zNRT

Simply put, as the volume of a gas decreases, the pressure increases proportionally in order to keep the ideal gas law equation equated.

Ideal compression occurs under isentropic conditions, which means the process is both reversible and adiabatic. The idealized efficiency of a process can be assumed to be isentropic, which allows the efficiency of a compressor to be evaluated. The isentropic efficiency of a particular compressor is the ratio of the work done by an isentropic compressor to that of the actual compressor.

There are many types of compressors. Positive displacement compressors, which use physical force to displace gas into smaller volumes include:

• Diaphragm compressors
• Ionic liquid piston compressors
• Reciprocating compressors
• Rolling piston compressors
• Rotary screw compressors
• Rotary vane compressors
• Scroll compressors

Dynamic compressors, on the other hand, use a continuous flow to pass gas through an element to generate a higher pressure, and include:

• Air bubble compressors
• Axial-flow compressors
• Centrifugal compressors
• Diagonal/mixed-flow compressors

Compressors in refrigerators are further classified as being either hermetic, open or semi-hermetic, depending on the relationship of the location of the compressor and the compressed vapor.

The oil and gas industry also use compressors and have their own set of specific compressor types:

• Booster compressors
• Flash gas compressors
• Gas lift compressors
• Reinjection compressors
• Vapor-recovery compressors