Note: Descriptions are shown in the official language in which they were submitted.
3~i
I~ 6141 TITLE
Apparatus with Expandable Tube Bundle
DESCRIPTION
Tech~ical Field
This invention relates to a flexible tube
and shell apparatus. More specifically, this inven-
tion relates to an apparatus having hollow, flexible
tubular units for fluids ko pass through and a hous-
ing or shell surrounding the tubular units so that
one fluid can be passed thxough the apparatus between
the shell and the tubular units and another fluid can
be ~assed through the tubular units with the flexible
tubes in a twist configuxation with respect to the
individual tubes from one end to the other end.
Background Art
Heat exchanger apparatuses with flexible
tubes are described in the prior art, e.g., U.S.
Patent Nos. 3,277,959; 3,391,041; 3,391,042; 3,380,513;
3,848,660; 3,526,275; 3,662,817 and 3,315,740. Heat
exchangers described in the aforesaid patents possess
tapes and screen baffles to keep the flexible tubes
from rubbing against the housing around said tubes
and to effect a suitable heat transfer rate. At high
fluid flows the tubes tear free of said tapes thereby
in some cases requiring thicker tube walls because
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of the tube welds. The thicker walls reduce heat
transfer rate. Said tapes and baffle also tend to
filter out dirt in sedimentary deposits that is very
difficult and in some cases impossible to remove.
Prior art flexible tube heat exchangers do
not attain maximum heat transfer due to the tendency
of the flexible tubes to remain parallel to each
other thereby permitting the tubes to occupy less than
all of the available volume within the housing of said
heat exchanger. This provides a bypass route for the
fluid passing through the shell side of the exchanger.
In the operation of conventional heat ex-
changers equipped with either rigid tubular elements
or flexible tubular elements, the shell side o the
tubular elements tend to build up or cake with solid
material from the fluid, e.g., river water, used as
the heat exchange medium, thereby decreasing the
heat exchange efficiency and interfering with the
flow patterns in the exchanger. Most exchangers
therefore have to be shutdown frequently to remove
the solid material before the efficiency of the heat
exchanger falls below some desired minimum. The same
buildup can occur when the shell side of the tubular
elements contains a fluid containing material which
can be separated out as a solid during its presence
in the heat exchanger.
Disclosure of Invention
. _
Now it has been found th~t when conventional
flexible tube heat exchangers are provided with tubu-
lar elements set in a twist configuration in a hous-
ing such that the twist amounts to 1~25 per foot of
tubular bundle length and when circular spacers
arranged from 6-30 inches apart are provided for said
tubular elements, the tubular elements are capable of
flexing and moving and cannot lay parallel to one
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another, ~hereby reducing buildup of solid paxticles
thereon. Thus brackish water may be used as a heat
transfer medium without problems in buildup of sedi-
ment between the tubes. The spacers are used to
effect more efficient flow patterns than when the
tubes are held by old conventional spacers and tapes.
The absence of tape welds makes it possible to use
thin walled tubes to attain maximum heat transfer
rates in heat exchangers and more efficient ion trans-
fer in ion exchangers. The use of spacers instead oftapes also causes a flow pattern of the fluid such
that sediment deposits from the fluid tend to be
washed through the exchanger.
Accordingly, in an apparatus comprising in
combination an elongated bundle of flexible, rela-
tively small diameter, thin walled, hollow, polymeric,
tubular elements and a housing means therefor ex-
tending the length of said bundle, said bundle com-
prising a plurality of said tubular elements with
open terminal portions and a lateral dimension secur-
ing means for the plurality of said tubular elements
cooperating with the terminal portions of said tubu-
lar elements, said housing means entirely surrounding
said elongated bundle and defining a zone for fluid
passage around said bundle, said housing having inlet
and outlet means and having means for securing itself
to said lateral dimension securing means in a fluid
tight arrangement, the length of said housing is
selected and determined by the length of the elongated
bundle, the improvement wherein the tubular elements
in each bundle vary in length from 0.1-1.0 inch per
foot of bundle length, preferably 0.2-0.6 inch per
foot of bundle length, said tubular elements forming
a bundle set in a twisted configuration, said twist --
amounting to from 1-25 per foot of bundle length,
.
preferably 6-15 per foot of bundle length as measured
by ~he angle of turn that the tubes in one terminal
portion of the bundle are to the tubes in the other
terminal portion, the -~uhe bunale havin~ a length
0.5-5% greater than the housing length for said tubes,
preferably 1.0-3%, said tubular elements passing
through circular spacers having an area of up to 80%
of the inside cross-sectional area of the housing
means made up of 1-600 holes through which said
tubular elements pass and an area of 20% or more of
the cross-sectional area made up of one opening
through which said tubular elements pass, said spacers
located at intervals of from 6-30 inches apart, preferably
18-24 inches and rotated with respect to the openin~
having an area of 20% or more of the area of the
spacer relative to the adjacent spacers, said rotation
ranging from 45-315, the number of tubes passing
through each hole ranging from 1-100.
The preparation of conventional flexible
tube apparatus for use as heat exchangers is known in
the art, e.g., U. S. Patent Nos. 3,277,959; 3,391,041,
3,391,042 and 3,315,740.
The tubular elements are generally formed
of a suitable thermoplastic polymer. The tubular
elements are preferably formed of a suitable poly-
flurinated plastic material and in sizes as disclosedin U. S. Patent 3,228,456. Particularly adaptable are
polymers and copolymers of tetrafluoroethylene sold
under the trade mark Teflon~ by E. I. du Pont de Nemours
and Company and polypropylene. Representative
examples of such polyfluorinated thermoplastic
polymers include polytetrafluoroethylene modified
with polyhexafluoropropylene, copolymers of tetra-
fluoroethylene and perf]uoropropylvinyl ether,
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tetrafluoroethylene, ethylene and hexafluoroacetone
(Tefzel~ manufactured by E. I. du Pont de Nemours and
Company) and fluorinated ion exchange pol~mers. How-
ever, other polymers may be used without departing
from the spirlt of the invention. Any organic poly-
meric compositions that are thermoplastic, possess
suitable compatability with the fluids handled,
possess adequate properties such as strength at the
desired operating conditions and further possess
adequate thermal conductivity for the desired use
may also be used. Representative organic polymeric
compositions also include polymers of aliphatic
olefins, e.g., homopolymers and copolymers of
ethylene, propylene, butene-l, pentene-l, hexene-l,
octene-l, decene-l, butadiene, styrene; polymers of
vinyl halides, e.g., vinyl chloride, vinyl fluoride,
vinylidene fluoride; polymers of amides, e.g., hexa-
methylene adipamide, hexamethylene, sebacamide,
caprolactam, etc.; polyacetals, e.g., polyoxymethy-
lene, formaldehyde copolymers; polyaromatic ethers,e.g., polyphenylene oxide; polyurethanes; polyesters,
e.g., polycarbonates, polyacrylates, polyalkylene
dicarboxylates; chlorinated polyethers, etc.
The fluorinated ion exchange polymers
possess pendant side chains containing sulfonyl groups
attached to carbon atoms having at least one fluorine
atom connected thereto and are disclosed in U.S.
Patent Nos. 3,282,875; 3,041,317; 3,718,627 and
3,560,569.
The fluorinated ion exchange polymers are
prepared from monomers which are fluorinated or
fluorine substituted vinyl compounds. The polymers
are made from at least two monomers with at least
one of the monomers coming from each of the two groups
described below. The first group is fluorinated vinyl
`:
compounds such as vinyl fluoride, hexafluoropropylene,
vinylidene fluoride, trifluoroethylene, chlorotri-
fluoroethylene, perfluoro(alkyl vinyl ether), tetra-
fluoroethylene and mixtures thereof.
The second group is the sulfonyl-containing
monomers containing the precursor -SO2F or -SO2Cl.
One exa~ple of such a comonomer is CF2-CFS02F. Addi-
tional examples can be represented by the general
formula CF2=CFRfSO2F wherein Rf is a bifunctional
perfluorinated radical comprising 2-8 carbon atoms.
The particular chemical content or structure of the
radical linking the sulfonyl group to the copolymer
chain is not critical but such must have a fluorine
atom attached to the carbon atoms to which is attached
the sulfonyl group. If the sulfonyl group is attached
directly to the chain, the carbon in the chain to
which it is attached must have a fluorine atom
attached to it. Other atoms connected to this car-
bon can include fluorine, chlorine or hydrogen. The
Rf radical of the formula above can be either branched
or unbranched, i.e., straight-chained and can have
one or more ether linkages. I~ is preferred that the
vinyl radical in this group of sulfonyl fluoride con-
taining comonomers be joined to the Rf group through
an ether linkage, i.e., that the comonomer be of the
formula CF2=CFORfSO2F. Illustrative of such sulfonyl
fluoride containing comonomers are
CF2=CFOCF2CF2S02F,
CF2-CFOCF2CFOCF2CF2S02F,
CF3
CF2=CFOCF2CFOCF2CFOCF2CF2S02F,
CF3 CF3
CF2=cFcF2cF2so2Fr and
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CF2=CFOCF2CFOCF2CF2So2F.
CF2
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CF3
The most preferred sulfonyl fluoride con-
taining comonomer is perfluoro(3,6-dioxa-4-methyl-7-
octenesulfonyl fluoride),
CF2=CFOCF2CFOCF2CF2So2F.
CF3
The preparation of tetrafluoroethylene
polymers and copolymers thereof with other fluoro-
carbons or hydrocarbons are well known in the art as
are the other polymeric compositions.
The tube bundles of the apparatus of this
invention are prepared from tubes whose variation
in length range from 0.1-l.0 inch per foot of tube
length. These tube bundles can conveniently be pre-
pared by the use of a trough having a bend that is
generally at least 5, preferably 10-15, of any
desired length, into which tubular elements are laid.
Due to this bend in the trough, the tubes laid therein
will vary in length from the adjacent tubes. The
tubes are then cut to conform to the desired length
of the bundles by a vertical cutting of both ends
of the tubesO The tube ends are then sealed together
with heat by the methods descrihed in U.S. Patent ;
3,315,740 after the desired number and type of
spacers have been placed in the trough so that the
tubular elements pass through the holes in the spacer
as desired.
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Spacers are ~Ised to help keep the tubular
elements from nesting by more evenly distributing
the tubular elements within the housing walls.
The spacers are placed 0~5-2.5 feet apart.
This depends on the particular system being used.
Th~ design of the spacer so that up to 80% of the
area is made up of holes for the tubular elements to
pass through is unique and causes the flow of fluid
to avoid parallel flow by arranging the opening that
amounts to 20% of the area of the spacer to be turned
at least 45 from the adjacent spacer. There can be
from 1-600 holes in the area amounting to up to 80%
of the total spacer area. Each hole is capable of
having 1-100 tubular elements pass through. The re--
maining area of 20% or more of the spacer is oneopening through which from 1-100 tubular elements
can pass. The passage of some fluid through the
spacer holes between the circumference of the holes
and the outer surface of the tubular elements permits
minimal parallel flow of the fluid, but results in a
reduction in the wear of the tubular elements. The
turning of the spacers with respect to the adjacent
spacer can be from 45-315, however, they are prefer-
ably turned from 90-270,and most preferably 180
from the adjacent spacer to prevent parallel flow of
the fluid on the shell side of the exchanger. This
arrangement of the spacers directs the majority flow
of fluid on the shell side of the tubular elements
through the open sections thereby creating a cross
flow that impro~es the heat transfer rate across the
tubes. Some fluid passes around the tubes between-
the tubes and the hole through which they pass
but the majority passes through the open sections
that are at least 45 turned from the previous spacer
thereby preventing channeling. The majority flow is
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a cross flow with some parallel flow occurring around
the tubes in the holes.
The spacers of this invention are yenerally
circular in shape and sized to fit tightly against
the inside circumference of the housing in such a
manner that the fluid in the shell side of the ex-
changer will only minimally flow around the spacers.
The tubes are pulled from creel, skraight-
ened and threaded through the spacers. One end of
the tubes is fused together and to a connector ring
that surrounds the fused tubes. The tubes are then
bowed by laying them in a trough with a bend (angle
of bend disclosed herein) with the spacers in place
and the second end of the tubes is fused together and
to a connector ring that surxounds the fused tubes.
The fusing of the tubular elements at the ends can be
performed one one end before subjecting them to the
desired bend followed by twistlng and fusing the other
end or both ends may be fusedafter they have been sub-
jected to the desired bend and twist. Both ends maybe fused before any twist. In this case, the tube
bundle is twisted when the ends are anchored to the ;
housing means.
The spacers are anchored in the desired
position by the use of a rod running the length of
the tube bundle through each spacer at its outer
edge and fused to the other tubes and to a sheath or
~` header ring as a tubular element is. The rod is
generally of plastic material (e.g., TeflonO). The
polymeric materials described above may also be used
to make said rods. The ends of the rods are sealed
with the honeycomb of tubular elements to anchor the
rods at both ends. There are four rods anchoring the
spacers in each bundle, said rods spaced about 90
apart at the outer circumference of the tubular
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elements. The rod size is generally o~ the sa~e out-
side diameter as the tubes. However, larger outside
diameter rods can also be used.
The apparatus of this invention results
in three improvements over conventional apparatuses.
These are (1) reduced buildup of sediment on the
shell side of the tubes, (2) reduced tube leaks (due
to absence of tapes), (3) increased overall heat
transfer due to lower velocity of fluids on the shell
side without sedimentary deposits and reduced nesting
of the tubes. The three critical requirements in
achieving the a~ove improvements are the variation in
length o~ the tubes, the twist set of the tubes, the
spacers and bowed tubes. The bowed tubes are
attained with the use of an excessive tube bundle
length for the housing so that the tube ends must be
pushed in toward each end of the housing before the
bundles are locked to the housing in fluid tight
arrangement. Thus, when the twisted tube bundle is
inserted into the housing, the tube bundle ends are
pushed into the housing before anchoring the terminal
portions of the tube bundle in fluid tight arrange-
ment with the terminal portion of the housing means
bowing the tubes outwardly toward the housing. This
excess length of the bundle of tubes amounts to
0.5-5% more than the housing length.
The terminal portions of the bundle of
tubular elements are sealed in an arrangement within
an annular member that cooperates with the lateral
dimension securing means. The lateral dimension
securing means and the means for attaching said
securing means to the housing are known in the art.
Any conventional means for accomplishing this may
be used. U.S. Patent 3,277,959 discloses the fluid
tight arrangement between the lateral dimension
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securing means and the hou~ing and details relating
- thereto.
What is meant by a conventional flexible
tube apparatus is an apparatus known in the ar~ as
heat exchanger which has ~lexible, relatively small
diameter, thin walled, hollow, polymeric tubular
elements. The preferred tube sizes of this invention
are from 0.125 inche O.D. to 0.305 inche O.D. Such
exchangers are described,for example, in U.S. Patent
Nos. 3,277,959; 3,391,041; 3,391,042; 3,315,740;
3,61~,022; 3,417,812; 3,363,680 and 3,526,274.
In operation the apparatus of this invention
may be used to exchange heat between two fluids. The
fluids, e.g., may be sulfuric acid of different
strengths and different temperatures. A process
might involve liquids inside the tubes and gas on
the shell side, e.g., sulfur dioxide gas on the
shell side and water in the tubes. The apparatuses ;
Qf this invention are most often utilized to exchange
heat from one ~luid to another fluid where corrosive-
ness of one fluid or both is a factor to be considered.
It is important that the cleaner fluid
being used be the fluid inside the tubes and the one
not as clean be the fluid outside the tubes. The
flow of heat from the shell side of the tubes ir.to
the tubes or from the inside of the tubes toward the
shell side also tends to cause the tubes to bow.
The apparatus of this invention when the
tubular elements are fabricated from fluorinated ion
exchange polymers with sulfonyl groups may be used
to separate metals from plating solutions with re-
duced build up of sediment on the shell side of the
tubular elements from the plating solutions.
The housing means may be fabricated from
steel or other metals and it may be uncoated or
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coated or lined with a polymeric material where
corrosiveness is a factor. The polymer used for
this coating may be selected ~rom the polyraers
described herein but is not intended to be limited
to said polymers. Thus, coating or lining may be
of polymers that are not thermoplastic.
Brief Description of the Drawings
Figure l is an isometric illustration of
a tube bundle with a twist configuration also showing
the rods that anchor the spacers in place.
Figure 2 is a cross section of the tube
bundle o~ Figure 1 at a spacer showing the openings
in the spacer and its position relative to an adja-
cent spacer.
Figure 3 is a cross section of the tube
bundle of Figure 1 at the spacer adjacent to the
spacer in Figure 2 showing the openings in the spacer
and its position relative to an adjacent spacer.
Referring now to Figures 2 and 3, spacer 2
is shown with holes through which a plurality of
tubular elements pass making up as much as 80~ of the
area of the spacer. An opening 11 that amounts to
" 20% or more of the surface area of the spacer is pro-
vided for a plura~ity o tubular elements. An iden-
tical spacer 3 is shown rotated 180 with respect to
-` identical spacers 2~
Referring now to Figure 1, rods 7 and 8
are fused into the honeycombed ends 6 of the tubular
elements in the same manner as an individual tubular
element. Rod 7 extends through holes on spacers
_, 3, 4 and 5 and tie into the other terminal portion_
of the tubular elements in the same manner as an
individual tubular element. Rod 8 also extends
through the spacers and is fused to both ends of the
bundle but is located about 90 from rod 7. Two
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other rods spaced 30 apart and 90 from other rods
make up a total of four rods which anchor the spacers.
The spacers are lucated at intervals defined herein
between the terminal portions of the tube bundle
shown and are each rotated 180 with respect to the
adjacent spacer. The tube bundle and rods are
enclosed within a housing means. The tubular ele-
ments of the bundle are in a twist configuration
which, for purposes of illustration, are intended to
amount to 360.
The plurality of tubular elements making up
the bundle 1 are sealed together at both ends so that
the individual tubes are parallel to each other and
packed together with a minimum of space between them
to form a "honeycomb" effect 6. A sheath or header
ring 9 made up of polymer that can be the same as
that of the tubular elements is bonded by fusing the
sheath around the honeycomb of tubes. The finished
bond leaves no passageway between the tube walls and
sheath or between `the tube walls themselves.
Example l
An apparatus with the features of the
present invention was prepared with tubes of l/4 inch
O.D. of a copolymer of tetrafluoroethylene and hexa-
fluoropropylene (Teflon~ FEP 160 made by E. I. du Pontde Nemours and Company) that varied in length from
16 feet to 16 feet 8 inches and arranged in a 10
per foot of bundle length twist and in a housing such
that there will be a 2~ excess in length of the tubes.
The spacers were 18 inches apart with holes large
enough for 80 tubes per each hole. Raw river water
from the James River at Richmond, Virginia was fed
to the shell side of the apparatus and steam was fed
to the inside of the tubes and data taken to calcu-
late the overall heat transfer coefficient Uo. Thefollowing data represent average data from four runs:
13
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Overall
Steam Water Flow Coef~icient
Inlet ~emp F E~it Tem~ F GPM _ Uo
230 220 100 38
5 230 220 150 42
230 220 200 44
230 220 290 44
After six months of operation, there was
essentially no buildup of salt or sediment on the
shell side.
Comparison Example A
The procedure of Example 1 was followed
except that a conventional apparatus with 1/4 inch
O.D. of the same Teflon~ FEP 160 tubes 11 feet in
length with welded tapes constructed as disclosed in
U.S. Patent 3,391,041 and 3,391,042 was used. The
raw river water and steam flows were essentially
parallel and gave the following overall heat transfer
- coefficient in a series of 3 runs:
,~ 20 Overall
r Steam _ Water Flow Coefflcient
Inlet Temp F Exit Temp F GPM Uo*
230 220 100 3~
`: 25 230 220 150 36
~;~. 230 220 200 40
*Uo = BTU/hr/ft area/0 differential temperature
Comparative Example B
. . _ .
~he apparatus of Comparative Example A was
placed in commercial operations with steam and water
at the same commercial facility with the same river
water. After six months of operation, the shell
side was plugged solid with silt.
Comparative Example C
A six foot long apparatus with a shell 8
inches in I.D. and 525 tubes 1/4 inch in O.D, 0.025
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inch wall thickness, of the same Teflon~ ~'EP 160 of
Example 1 making up a bundle of tubes with welded
tapes to hold the tubes as disclosed in U.S. Patent
3,391,042 with the screen baffle of U.S. Patent
3,417,812. The apparatus was connected so that a
slurry of sand in water could be recirculated
through the shell side of said heat exchanger. After
16 hours of recirculating of the sand slurry, the
exchanger had 62 lbs of sand deposited therein.
After six flow interruptions, 28 lbs of that amount
of sand were freed.
Example 2
The procedure of Comparative Example C was
followed except the appaxatus was one constructed
according to the disclosure in the present application
of the same size, number of tubes, diameter and length
as in Comparative Example C. One end of the tube
bundle was honeycombed (tubes fused to each other
and to a collector ring surrounding the honeycomb).
The tubes were slipped through three spacers spaced
approximately 18 inches apart, said spacers contain-
ing six circular holes in an area making up less
than 80% of the cross sectional area of the spacer
and one opening making up at least 20% of the cross
sectional area. The spacers were rotated 180 from
the adjacent spacer. The tube bundle was bent 8~ in
a trough having a 26 inch radius. The other end of
the tubes in the bundle was honeycombed while the
tube bundle was in this configuration. The longest
tube was three inches longer than the shortest tube
and the tube bundle length was three inches longer
than the shell. The tube bundle was pulled through
the shell and compressed and twisted 15 per foot of
tube bundle length to fit the shell and locked into
place. After 16 hours of recirculation of the same
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slurry makeup used in Comparative Example C, 16 lbs
of the sand were deposited in the apparatus. One
interruption of the recircul~tion freed 10 lbs of
sand. After five additional flow interruptions, 4 lbs
S of additional sand were freed.
Tests were conducted with an apparatus of
the present invention and another apparatus of the
same size except that the spacers of the present ln-
vention were not used. The apparatuses were compared
in a vertical position and in a horizontal position.
Example 3
The apparatus of this invention comprised
a shell six inches in diameter and six feet long.
A tube bundle containiny 106 tubes of l/4 inch O.D.
with a wall thickness of 0.025 inch was honeycombed
at one end. The tubes were slipped through three
spacers and the bundle was then laid in a trough with
a bend such that the tube leng~hs varied four inches
from the shortest to the longest. The tube bundle
was twisted 20 per foot of tube bundle length and
the other end was honeycombedO The tube bundle
length was one inch longer than the shell. The
spacers included holes 7/8 inch in diameter in a
triangular arrangement over an area amounting to 80%
of the area of the spacer and over the area covering
20% of the area of the spacer was a single noncircu-
lar opening~ There were 20 tubes passing through
the noncircular opening. Six and seven tubes in
some cases passed through each of the 7/8 inch holes.
The spacers were rotated 180 from the adjacent
spacer. The tube ends were pushed together to fit
the shell. The spacers were 18 inches apart.
Hot water was circulated inside the tubes
and cold water on the shell side and then this arrange-
ment was reversed. An overall heat transfer was
16
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17calculated from data obtained with the apparatus in
a vertical position and a horizontal position. The
data o~tained is summarized below:
Water temp shell side = 180F
Water temp inside tubes (AV) = 108F
Uo (vertical position) = 43
Uo (horizontal position) = 40
, Water ~emp shell side = 108F
i Water temp inside tubes (AV) = 180F
; lO Uo (vertical position) = 44
Uo (horizontal position) = 40
Comparative Example D
The apparatus of Example 3 was made except
that no spacers were used and the apparatus tested as
in Example 3. The following data was obtained:
~ater temp shell side = 180F
water temp inside tubes (AV) = 108F
- Uo (vertical position) = 30
Uo (horizontal position) = 22
Water temp shell side = 108F
Water temp inside tubes (AV) = 180F
Uo (vertical position) = 37
Uo (horizontal position) = 27
Comparative Example E
The apparatus of Example 3 was made except
that the twist was 5 per foot of tube bundle and no
spacers were used and the procedure of Example 3 was
followed. The following data was obtained:
Water temp shell side = 170F
Water temp inside tubes (AV) = 105F
Uo (vertical position) = 28
Uo (horizontal position) = 24
The above data indicates that although the
present invention gives better heat transfer in the
vertical position, either the vertical or horizontal
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position results in better heat transfer than when no
spacers are used.
BEST MODE
Example 1 represents the best mode of
operation.
INDUSTRIAL APPLICABILITY
,
The apparatus of the present invention can
be used where fluid heat exchange is required and
more especially where these fluids are corrosive in
nature. The apparatus of the present invention can
also be used in applications where ion exchange or
removal of ions from streams is required when the
tubular units are fabricated from ion exchange
material.
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