Page 30 - Separation process principles 2

xxxiv Dimensions and Units

CONVERSION FACTORS
Physical constants may'be found on the inside front cover of this book. Conversion factors
are given on the inside back cover. These factors permit direct conversion of AE and CGS
values to SI values. The following is an example of such a conversion together with the
reverse conversion.

Example
Convert 50 psia (lbf/in2 absolute) to kPa:
The conversion factor for lb$in2 to Pa is 6895, which results in
50(6895) = 345000 Pa or 345 kPa
Convert 250 kPa to atm:
250 kPa = 250000 Pa. The conversion factor for atm to Pa is
. Therefore, dividing by the conversion factor,
atm
Three of the units [gallons (gal), calories (cal), and British thermal unit (Btu)] in the
list of conversion factors have two or more definitions. The gallons unit cited here is
the U.S. gallon, which is 83.3% of the Imperial gallon. The cal and Btu units used here are
international (IT). Also in common use are the thermochernical cal and Btu, which are
99.964% of the international cal and Btu.

FORMAT FOR EXERCISES IN THIS BOOK
In numerical exercises throughout this book, the system of units to be used to solve the
problem is stated. Then when given values are substituted into equations, units are not ap-
pended to the values. Instead, the conversion of a given value to units in the above tables
of base and derived units is done prior to sirbstitution in the equation or carried out directly
in the equation as in the following example.

Example

Using conversion factors on the inside back cover of this book, calculate a Reynolds
number, , given D = 4.0 ft, .5 ftls, lbm/ft3, and p = 2.0 CP (i.e., centipoise).
Using the SI System (kg-m-s),

Using the CGS System (g-cm-s),

Using the AE System (Ib,-ft-h)
Convert the viscosity of 0.02 glcm s to Ib,/ft h: