Editing Scroll compressor (section)

===Efficiency===
The [[isentropic]] efficiency of scroll compressors is slightly higher than that of a typical reciprocating compressor when the compressor is designed to operate near one selected rating point.<ref>{{cite conference|last1=Elson|first1=John P.|last2=Kaemmer|first2=Norbert|last3=Wang|first3=Simon|last4=Perevozchikov|first4=Michael|title=Scroll Technology: An Overview of Past, Present, and Future Developments|conference=International Compressor Engineering Conference|date=July 14–17, 2008|url=https://docs.lib.purdue.edu/icec/1871|access-date=May 9, 2019|archive-date=May 9, 2019|archive-url=https://web.archive.org/web/20190509180632/https://docs.lib.purdue.edu/icec/1871/|url-status=live}}</ref> The scroll compressors are more efficient in this case because they do not have a dynamic discharge valve that introduces additional throttling losses. However, the efficiency of a scroll compressor that does not have a discharge valve begins to decrease as compared to the reciprocating compressor at higher pressure ratio operation. This is a result of under-compression losses that occur at high pressure ratio operation of the positive displacement compressors that do not have a dynamic discharge valve.

The scroll compression process is nearly 100% [[volumetric]]ally efficient in pumping the trapped fluid. The suction process creates its own volume, separate from the compression and discharge processes further inside. By comparison, reciprocating compressors leave a small amount of compressed gas in the cylinder, because it is not practical for the piston to touch the head or valve plate. That remnant gas from the last cycle then occupies space intended for suction gas. The reduction in capacity (i.e. volumetric efficiency) depends on the suction and discharge pressures with greater reductions occurring at higher ratios of discharge to suction pressures.