Scroll Compressors in Air Conditioning Systems

Scroll compressors are the black box you see in your air conditioning unit. This is not a technical term for them, but the casing for them is in fact a black box. They are the machine that compresses refrigerant (R-22 or R-410-a) in an air conditioner. Scroll compressors are the replacement of piston compressors. Scroll compressors give the mandatory cooling in an air conditioner and at a smaller size than its predecessor.

The use of these compressors will see two spirals; one stationary and the other mating spiral or scroll that circle around the stationary scroll that traps and displaces refrigerant gas from suction to discharge. The compression may happen because of quick reduction in volume that positively sweeps refrigerant from the inlet to outlet port. This in turn changes kinetic energy into potential energy.

Air conditioner compressors are categorized by either a seal type or an operation type.  The seal type is completely sealed, semi-sealed, and open type compressors. An operation type compressor is piston, scroll, rotary, or centrifugal. The performance of these compressors will be tested to acquire results of pressure ratio, efficiency, mass flow rate, maximum pressure ratio compared to the compressors' rotational speed.

A scroll compressor was invented in the early 20th century and was not upgraded to the current style we see today until the late 1960s. Scroll compressors are able to acquire a flow rate and outlet pressure at a smaller size and more efficiency than piston or reciprocating compressors. Although they are similar, cooling for scroll compressors are complicated compared to that of piston A/C units because the scroll's performance drop compared to the piston type at much higher ratios. However, most A/C units mandate the use of scroll compressors due to advantages over the piston type.

While the use of scroll compressors do open a wide array of advantages there are also some downfalls that come along with the use of them. They are more susceptible to debris because they do not have suction valves. Debris or any foreign objects open up the door for an issue due to the scrolls not operating with radial or axial compliance.