Definitions

Nomenclature Many of the quantities involved in this subsection are also dealt with in Section 2.1. Therefore, a single nomenclature that applies to both sections appears at the beginning of Section 2.1. Differences in notation exist for some of these quantities as a result of the coexistence of different traditions and pump cultures, so the nomenclature shows the equivalence in each case. An example is the use in this subsection of "c" and "w" to denote absolute and relative velocity respectively, whereas the NASA system of capital letters V and W is employed in Section 2.1.

Units The units used in this subsection are as defined in the nomenclature unless specifically noted in the text. In particular, the primary units for this subsection are those of the U.S. Customary System (USCS). A distinction in USCS usage in this subsection is that the pound force (lbf) is represented simply as "lb". In keeping with the commentary on SI units in the front matter of this handbook, conversions to SI units are given throughout this subsection, or the actual equivalent SI values are given in parentheses.

However, the number appearing in parentheses after the USGS value of specific speed ns is the equivalent value of the universal specific speed Hs. Note that the value of specific speed corresponding to the best efficiency point (BEP) operating conditions of the pump is the value of interest and is often used to identify the impeller geometry involved.

Volume Flow Rate Abbreviated to "flow rate" and known traditionally as "pump capacity" Q, this is the volume of liquid per unit time delivered by the pump. In USCS units, Q is expressed in U.S. gallons per minute or USgpm, for which the abbreviation "gpm" is

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