Page 177 - Chemical process engineering design and economics

Process Heat Transfer 159

leaks could occur at the tube sheets, either the shell or tube-side fluid will collect
in the space between both tube sheets. It is unlikely that both tube sheets will leak
simultaneously.
In Table 4.2, the shell-and-tube heat exchangers just discussed are com-
pared. Table 4.2 illustrates a general approach for evaluating and selecting equip-
ment. To compare various designs, first, list the important design features of heat
exchangers in the left column. Then, list the available heat exchanger designs in
the column headings.

Table 4.2 Comparison of Shell-and-Tube, Heat-Exchanger Designs
(Source Ref. 16 with permission..)

Design Features Filed Return Bead Outside-Pocked Outside-Packed Pull-Thivugh Inside Split
Tubesheel (U-Tube) Stuffing Box Lantern Ring Bundle Backing Ring
Is tube bundle No Yes Yes Yes Yes Yes
removal*?
Can spue No Yes Yes Yes Yes Yes
bundles be
used?
H<WB Expansion Individual tubes Floating bead Floating bead Floating head Heating head
differentia] joint in shell five to expand
thermal
expanjioa
relieved?
Can individual Yes Only those in Yes Yes Yes Yes
tubes be outside rows
replaced? without special
desiens
Can tubes be Yes Yes Yes Yes Yes Yes
chemicall,
deaned,both
inside and
outside?
Can tabes be Yes With special Yes Yes Yes Yes
physkany tools
cleaned on
Inside?
Can tabes be No With square or With square or With square or With square or With square or
physically wide triangular wide triangular wide triangular wide triangular wide triangular
cleaned on pitch pitch pitch pitch pitch
outside?
Are internal No No No No Yes Yes
gaskets and
bolting
required?
Are double Yes Yes Yes No No No
tubesheeU
practical?
What number Number Number limited Number limited One or two Number Number
oftubedde limited by by number of by number of limited by limited by
puncture number of U- tubes tubes number of
available? tubes tubes. Odd tubes. Odd
number of number of
passes requires passes requires
packed joint or packed joint or
expansion joint expansion
joint
Relative cost in 2 1 4 3 5 6
ascending
order, least
expensive = 1
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