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End users must specify certain performance requirements when requesting a quote for a new centrifugal compressor. Understand your process, as well as the advantages and disadvantages of each centrifugal compressor configuration, in order to choose the optimal centrifugal compressor for your application.
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Centrifugal compressors, also called radial compressors, are critical equipment in a wide variety of applications in the chemical process industries (CPI). As their name suggests, their primary purpose is to compress a fluid (a gas or gas/liquid mixture) into a smaller volume while simultaneously increasing the pressure and temperature of the fluid. In other words, compressors accept a mass of gas at some initial pressure and temperature and raise that gas to a higher pressure and temperature (Figure 1 ). At the higher discharge pressure and temperature, the gas density is also higher, so the mass of gas occupies a smaller volume - i.e., the gas is compressed.
Of the numerous technologies that can achieve compression, this article focuses on centrifugal compressors. It explores the various types of centrifugal compressors, provides valuable information on impellers, and explains basic centrifugal compressor sizing. (Reference 1 provides information on other types of compressors, such as positivedisplacement, axial, and others.)
Turbocompressors
Centrifugal compressors are members of a class of technologies called dynamic compressors, or turbocompressore. Axial compressors are also part of this class of turbomachines. Axial and centrifugal compressors draw their names from the primary direction in which the flow moves within the compressor. Axial compressors (Figure 2) handle much higher flowrates than centrifugal compressors, but generate lower pressure ratios. Modem centrifugal compressors accommodate lower flowrates than axial compressors but are capable of generating much higher pressure ratios. In turbocompressore, the increase in pressure and reduction in volume is accomplished by adding kinetic energy to the fluid stream (i.e., adding velocity pressure) and then converting that kinetic energy into potential energy in the form of static pressure. In centrifugal compressors, kinetic energy is added by impellers. The number of impellers in a compressor depends on how large a compression or pressure increase is needed for the process. As a result, compressors can have one or as many as 1 0 (or more) impellers.
The conversion of the velocity pressure to static...