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Unformatted text preview: CHE 3013, Fall 2010 1 of 14 Incompressible Fluid Flow Summary of Key Concepts and Skills Required for CHE 3013 Chapters 1, 2, 3, 5, and 8 Munson, Young, and Okiishi Fundamentals of Fluid Mechanics, 5 th Edition John Wiley & Sons, 2006 Chapter 1: Introduction Unit Systems 1. Chemical engineers must be able to work in both FPS (US Customary) and SI systems of units. 2. There is no standardized system of nomenclature. Variables have to be interpreted in the context in which they are used. 3. Find and keep a comprehensive list of unit conversion factors. There are some conversion factors inside the back cover of Incropera, et al., but these are probably not complete for our work. 4. Academia and literature SI 5. U. S. workplace FPS 6. 2 f m s lb ft lb 174 . 32 = c g (adequate precision for most cases, see p. 8) 7. Numbers without units are ambiguous and a major source of errors! Example: ( ) ( ) f lb 0.224809 0.45359237 9.80665 1 N 1 = = This should be written as f m 2 f 2 2 m 2 lb 0.224809 N 1 ft lb 174 . 32 s lb s ft 174 . 32 m 80665 . 9 s kg 0.45359237 lb kg 1 s m kg 1 N 1 = = = CHE 3013, Fall 2010 2 of 14 8. Common workplace units lb m /hr ACFM actual ft 3 /min ACFH actual ft 3 /hr SCFM standard ft 3 /min 60 F, 14.696 psia SCFH standard ft 3 /hr gpm gal/min BPD bbl/day 1 bbl = 42 US gal BPSD bbl/stream day psig lb f /in 2 gage psia lb f /in 2 absolute F degrees Fahrenheit cP centipoise hp horsepower power = rate of work (hphr/hr) kw kilowatt (kwhr/hr) Btu/hr rate of heat transfer ft feet in inch 9. Pressure measurements always include gage or absolute designation, i.e., psia or psig not psi. Differential pressures ( P 1 P 2 ) do not include gage or absolute designation, but the difference can only be calculated when both pressures are on the same basis, i.e. ( ) ( ) psig psig psia psia psi 2 1 2 1 P P P P P = = If the units of a calculation are incorrect, the numerical value is also incorrect due to missing conversion factors. 10. Be very careful to distinguish between dimensionally homogeneous and non homogeneous equations (see Example 1.1, p 5). Vendors literature and other industry publications often use dimensionally non homogeneous equations. For example, ( ) ( ) . . psi 31 . 2 ft g s P Head = CHE 3013, Fall 2010 3 of 14 Dimensional Analysis 1. Dimensional analysis is a powerful concept and has been widely used in developing practical correlations for momentum, mass, and heat transfer. 2. Most dimensionless groups we encounter have physical meaning, i.e. forces viscous forces inertial number Reynolds V D Re = forces nal gravitatio forces inertial number Froude gD V Fr = 3. Proficiency is required for working with dimensionless numbers, rather than developing dimensionless groups or correlations....
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