C. P. KITTREDGE
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 cap-
ital letters V and W is employed in Section 2.1.
Units The units used in this subsection are as defined in the nomenclature unless specif-
ically 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 s. 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 capac-
ity" 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
used. (1 US gallon 231 in3.) For very large pumps, the units ft3/sec are used. The con-