ChBE421
Test #1
Fall 2009
1. (25 pts)
Answer
briefly
(5 pts) Consider a ball (dimension ‘L’) thrown at a defined velocity (‘U’). If the density
of the liquid through which the ball is thrown is doubled while the viscosity is reduced by
1/3, does the flow become more laminar or turbulent? By what factor does the Reynolds
number increase or decrease?
(3 pts) What are the three conditions required to be met for simplification of the integral
mass, energy and momentum balances to their respective special cases?
(4 pts) Please write out the complete integral energy balance equation (Accum = Input –
Output) and define the physical meaning of each term.
(5 pts) What assumption must be made to simplify the Mechanical Energy Balance into
Bernoulli’s Equation?
(8pts) When considering pump efficiency (
η
p
): 1) how is
η
p
determined (this is an
equation), 2) what are the limits the size of
η
p
, 3) write the component of the mechanical
energy balance equation where
η
p
is applied, and 4) is the
lw
term in the mechanical
energy balance equation now negligible, or if not, what is it’s physical meaning?
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 Spring '10
 1`
 Fluid Dynamics, Force, Kinetic Energy, Mass, pts, energy balance equation

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