What is an AC Compressor?

What is an AC Compressor?

Updated: 4/31/2017

A compressor is a critical and sometimes expensive part of the air conditioner unit.  The compressor has the role of circulating the pressure, specifically from low to high gas pressure.  In laymen’s terms, it moves liquid refrigerant through a pipe to create cold air.  When the low pressure gas is changed to high pressure, the cold air is created.  The compressor specifically squeezes the refrigerant and alters its temperature according to the home’s air.  There are 5 types of compressors that we will discuss.  These compressors include reciprocating, scroll, rotary, screw, and centrifugal.  Each is distinct in how it operates.

According to “Machinery Lubrication,” a reciprocating compressor is “A positive-displacement machine that uses a piston to compress a gas and deliver it at high pressure.  They are often some of the most critical and expensive systems.”  These are some of the most commonly used compressors for AC’s.  The compressor utilizes electricity to compress the refrigerant.  The piston is the actual piece that performs the reciprocating motion.  Without the piston, the refrigerant could not be compressed.  These reciprocating compressors often come in one, two, four, five, seven, or ten pistons.  This leads into the next type we will discuss.

The scroll compressor uses a twisting motion to squeeze the refrigerant.  One scroll remains stationary while another slowly turns within.  The refrigerant is pushed towards the center causing a change of gas pressure.  The main difference between this compressor and the reciprocating is the sound.  The scroll is generally quiet due to its simple mechanisms.  In comparison, reciprocating compressors can be loud. 

Rotary screw air compressors are commonly used by industries.  They are expected to run 24/7.  The compressor works when two screws rotate counter to each other.  A small filter is emplaced to catch any outside particles that may be harmful.  After the air passes through the filter, it moves through the two rotating screws.  The air is then compressed as it moves through a smaller space and the pressure increases.  This is another example of a compressor that runs quiet. 

The rotary compressor contains a complex design that is usually more expensive then piston-type compressors.  The rotors contain a unique shape that turn in opposite directions.  The air gets trapped between these rotors and is pushed to one direction.  The trapped air and the unique shape of the rotors causes an increase in pressure.  There is one single exhaust port where the air is transferred out of to the home or car. The number of blades in the rotor ranges from two through eight. 

  Centrifugal compressors use rotating blades to transfer energy to the gas.  Unlike reciprocating compressors, they require little maintenance.  These compressors are usually used for large installations. This could be a massive storage area for food.  But what is meant by centrifugal?  This is the energy moving in a circular motion.  The velocity allows the cold air to be released efficiently.  Because of this, they operate at an extremely fast speed compared to other compressors.   







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