Page 444 - Handbook of Energy Engineering Calculations

substituting for h the appropriate correlation for the coefficient; for k, the
value obtained from the Weber equation; for A, the equivalent of the surface
area in terms of the number of tubes, outside diameter and length, according
to the relation A = π n(d /12) L; for mass velocity on the tubeside,
o
; and for mass velocity on the shellside, G = 411.4 W /
o
o
.
The resulting equation is rearranged to separate the physical-property,
work, and mechanical-design parameters into groups. To obtain consistent
units, the numerical factor in the equation combines the constants and
coefficients. The form of the equations shown in Table 6 as Eqs. (1), (11),

(18), and (19) omits dimensionless groups such as Reynolds or Prandtl
numbers, but includes single functions of the common design parameters
such as number of tubes, tube diameter, tube length, baffle pitch, etc.

The individual products calculated from the four equations are added to
give the sum of the products (SOP). A valid design for heat transfer should
give SOP = 1. If SOP comes out to be less or more than one, the products for
each resistance are adjusted by the appropriate exponential function of the
ratio of the new design parameter to that used previously.

More sophisticated rating methods are available that make use of complex
computer programs; the described method is intended only as a general,
shortcut approach to shell-and-tube heat-exchanger selection. Accuracy of the

technique is limited by the accuracy with which fouling factors, fluid
properties, and fabrication tolerances can be predicted. Nevertheless, test data
obtained on hundreds of heat exchangers attest to the method’s applicability.
This procedure is the work of Robert C. Lord, Project Engineer, Paul E.
Minton, Project Engineer, and Robert P. Slusser, Project Engineer,

Engineering Department, Union Carbide Corporation, as reported in
Chemical Engineering magazine. SI values were added by the handbook
editor.

Nomenclature