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94 CHAPTER 4. EVALUATION OF TRANSFER COEFFICIENTS
Analysis
The Reynolds number as
The we of the correlation proposed by Bedingfield and Drew, Eq. (4.4-10), gives
Sh = 0.281 Re2
= 0.281 (9375)1'2(1.16)0*44 29
=
Therefore, the average mass transfer weflcient is
4.5 FLOW IN CIRCULAR PIPES
The rate of work done, W, to pump a fluid can be determined from the expression
W = m W = m (/ dP) (4.5-1)
where m and 9 are the mass flow rate and the specific volume of the fluid, re
spectively. Note that the term in parenthesis on the right-hand side of Eq. (4.5-1)
is known as the shaft work in thermodynamics3. For an incompressible fluid, i.e.,
? = l/p =constant, Eq. (4.51) simplifies to
I&'= Q lAPl (4.5-2)
where Q is the volumetric flow rate of the fluid. Combination of &. (4.52) with
Eq. (3.1-11) gives
FD (v) = Q JAPI (4.5-3)
or.
(4.5-4)
Expressing the average velocity in terms of the volumetric flow rate
Q
(v) = - (4.5-5)
7rD2/4
3Work done on the system is considered positive.
