US3419069A - Heat transfer apparatus having flexible plastic tubular elements arranged in a braided configuration - Google Patents

Description

3,419,069 TUBULAR Dec. 31, 1968 1:3, BAKER ET AL HEAT TRANSFER APPARATUS HAVING FLEXIBLE PLASTIC ELEMENTS ARRANGED IN A BRAIDED CONFIGURATION Filed April 28. 1967 Sheet INVENTORS THOMAS BERNARD BAKER STANLEY BURTON LEVY ROLAND FREDERICK OTTOLINI ATTORNEY Dec. 31, 1968 115, B K ET AL HEAT TRANSFER APPARATUS HAVING FLEXIBLE PLASTIC TUBULAR ELEMENTS ARRANGED IN A BRAIDED CONFIGURATION Filed April 28, 1967 Sheet FIG.

INVENTORS THOMAS BERNARD BAKER STANLEY BURTON LEVY ROLAND FREDERICK OTTOLINI ATTORNEY United States Patent 3,419,069 HEAT TRANSFER APPARATUS HAVING FLEXIBLE PLASTIC TUBULAR ELE- MENTS ARRANGED IN A BRAIDED CONFIGURATION Thomas Bernard Baker and Stanley Burton Levy, Wilmington, and Roland Frederick Ottolini, Newark, Del., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Apr. 28, 1967, Ser. No. 634,631 Claims. (Cl. 165--158) ABSTRACT OF THE DISCLOSURE A heat transfer apparatus having a casing member surrounding at least one bundle of flexible plastic tubular elements, a substantial portion of each bundle comprising a first group of tubular elements arranged in a given pattern and interlaced in a substantially uniform manner with a second group of tubular elements arranged in symmetrically opposed pattern to provide a coherent flexible bundle, stable in size, and having a predetermined degree of packing and predetermined resistance to fluid flow through said bundle exteriorly of said elements which predetermined characteristics cooperate to provide a good heat transfer characteristics for the apparatus.

Introduction This invention relates generally to improved heat exchange, or heat transfer, apparatus; and more specifically to heat exchange apparatus having flexible plastic tubular elements in a particularly advantageous bundle arrangement.

It is an object of the invention to provide novel and improved heat exchange apparatus combinations or arrangements having plastic components, especially flexible tubular elements, and components made of materials such as metals which arrangements perform effectively, reliably, and in addition, not only accommodate but utilize advantageously during their operation, the different properties of the plastic components under the desired operating conditions.

It is a further object to provide such novel and improved apparatus combinations which will overcome the problems, disadvantages, and deficiencies of early prior art flexible plastic tube heat exchange apparatus combinations as will be discussed hereinafter.

Other objects and advantages will be apparent from a consideration of the following specification, claims and accompanying drawings.

Background of the invention As indicated generally in US. Patent No. 3,228,456, heat exchange arrangements utilizing plastic tubular elements are known and have been found to be advantageous in many applications. Because of the use of small flexible plastic tubular elements, a number of special problems have been encountered, not only in designing and producing such arrangements, but also in their operation. Some of these problems involve the relatively low heat transfer coeflicients and the relatively high coeflicients of thermal expansion possessed by most plastic materials as compared with parts made of more conventional ma- 3,419,069 Patented Dec. 31, 1968 terials such as metals. Other problems relate to the different properties such as compressive strength, tensile strength, flexibility, and melting points of these plastic materials relative to the other materials used. Production and operating techniques as well as apparatus designs must be established such that the more conventional parts such as those still for-med of the usual metallic compositions can be shaped, formed, heated, and used While in cooperative association with the plastic parts to produce and operate economical, reliable, and effective heat exchange arrangements Wit-hout destroying or damaging the associated plastic parts by application of excessive forces, impacts, temperatures, or other conditions.

One problem involves maintaining uniform packing and resistance to fluid flow for the tube bundle in plastic tube heat exchange apparatus. This, in turn, has been related to the flexible nature of the small plastic tubes used in this type heat exchanger apparatus. The problem is aggravated at elevated operating temperatures at which considerable thermal expansion takes place and the tubes become even more flexible and limp. A number of special structural features have been needed and used in the past to try to solve these problems. One of such features as disclosed in prior US. Patent No. 3,228,456 involves the use of transverse rigid baflle members through which the plastic tubular elements extend for lateral support. The baflle members also are needed to provide the desired fluid flow conditions exteriorly of the tubular elements. A second of such features as disclosed in prior US. Patent No. 3,277,959 involves the use of interleaved tape elements spaced along a bundle of plastic tubular elements and bonded thereto. The tape elements position the tubular elements, maintain them in a fairly compact bundle, and control, to some extent, fluid flow conditions exteriorly of the tubular elements in the bundle. A third feature of this type as disclosed in prior copending application Ser. No. 598,070, filed Nov. 30, 1966 in the name of Robert Dilman Smith involves placing a bundle of plastic tubular elements in a foraminous casing member or sleeve to maintain a compact bundle configuration and desired fluid flow conditions in the bundle exteriorly of said elements.

However there are serious problems and disadvantages associated with each of the above prior art features. For example, threading the great multiplicity of small tubular elements through perforated transverse baffies as mentioned in the feature first mentioned is a prohibitive operation as to cost and time, and in addition does not prevent the squeezing together and spreading apart of the flexible tubular elements between the spaced transverse baflle members, which has an adverse effect on fluid flow conditions and on the tubular elements.

As to the second feature mentioned above, the spaced tape elements bonded to the tubular elements, prevent bending of the bundles during production, and use and will break loose or damage the tubular elements if excessive bending forces are encountered. In addition, the tapes do not prevent the squeezing together and spreading apart of the flexible tubular elements between the spaced tape elements which has an adverse effect on fluid flow conditions and on the tubular elements. The

bonding of spaced tape elements to the tubular elements tubular elements, does reduce the spreading apart of the tubular elements but still requires spacing means such as the tape elements to maintain the desired spacing between the tubular elements. Squeezing together of the tubular elements between the tape element positions still occurs and this feature represents a costly, and not entirely successful, way to provide a compact bundle with uniform spacing and resistance to fluid flow through the bundle.

In applicants improved arrangement embodying the present invention, the flexibility of the plastic tubular elements is used to provide a bundle of uniformly interlaced tubular elements which, without any additional structure or means, results in a coherent compact bundle in which uniform packing, resistance to flow, and spacing of the tubular elements are maintained uniformly along the bundle. In addition, the bundle is flexible and rugged as required in assembly and operation of the heat exchange apparatus, and also accommodate thermal expansion of the elements in a more uniform and controlled manner. Where the bundles are provided in the preferred form of sleeve-like configurations it is possible without difficulty to assemble a number of sleeve-like bundles one inside the other and, if desired, to provide additional support and/or fluid flow for the bundle by positioning a substantially rigid support or a sparger member within the bundle as will be described in detail hereinafter.

In the drawings:

FIGURE 1 is a partial isometric view of a preferred heat transfer arrangement embodying features of the invention with certain parts broken away to show the relationship of the component parts and features.

FIGURE 2 is a side elevational view, with certain parts broken away for a clearer showing, of a somewhat different heat transfer arrangement embodying features of the invention.

FIGURE 3 is an enlarged end view of the sparger and support member of the arrangement of FIGURE 2.

FIGURE 4 is a partial side elevational view of a bundle of tubular elements with the cooperating tube sheet member and a rigid support and sparger member associated therewith. The interlaced arrangement of the flexible tubular elements embodying the present inven tion is also shown in this figure.

FIGURE 5 is a partial enlarged detailed view of the preferred interlaced flexible tubular element arrangement of the invention, showing how the important angle of tubular element cross over or intersection is measured.

FIGURE 6 is a partial transverse cross sectional view of the arrangement of FIGURE 4 taken at line 66.

FIGURE 7 is a partial longitudinal cross sectional view of the sparger and support member of FIGURE 3.

FIGURE 8 is an enlarged partial side elevational view Of a heat exchange arrangement embodying features of the invention and similar to that of FIGURE 4, showing a modified arrangement in the tubular elements are interlaced With each other in groups of four.

One preferred heat exchange arrangement or combina: tion embodying principles of this invention is shown in FIGURES l, 4, 5 and 6. The apparatus shown in these figures comprises a casing member 10 formed by wall elements 11 of suitable material which define a chamber for a fluid the upper surface of which is indicated at 14. The casing member is provided with fluid inlet means 12 and fluid outlet means 13. An elongated compact bundle of a relatively large number of small thin-walled flexible plastic tubular elements T is positioned as shown to extend through at least a portion of a fluid in the chamber defined by wall elements 11. Each end of the bundle 20 is provided with a header unit 21 which maintains free communication between the interiors of the tubular elements T and fluid supply conduit elements 23, 24, 25. Suitable header unit arrangements are shown for example in U.S. Patents 3,228,456 and 3,277,959 mentioned above. The tubular elements T of which there may be from about 500 to about 10,000 or more, may be formed of a composition, and in sizes, disclosed in the abovemen-tioned U.S. Patent No. 3,228,456. The composition preferred is a polyfluorinated plastic such as a copolymer of tetrafluoroethylene and hexafluoropropylene with a thermal conductivity of about 0.1 B.t.u./hr./ft./F. The tubular elements in the bundle are preferably in a size range between about 5 and 275 mils outside diameter with a wall thickness between about 0.5 and about 30.0 mils on centerlines spaced in an average of about 1.01- 2.00 diameters.

As best shown in FIGURES 4, 5 and 6, the position of the tubular elements relative to each other, the packing of the tubular elements, and their resistance to fluid flow are controlled solely by the interengagement and interlacing of the flexible tubular elements with each other. A braided arrangement, as shown in FIGURES 4, 5 and 6 is preferred in which a plurality of braided sleeves are assembled one inside the other to form the bundle. Generally speaking, each sleeve comprises a first plurality of tubular elements positioned in a first helical pattern and an interengaged interlaced second plurality of tubular elements positioned in a second opposing helical pattern. In the preferred interlaced pattern shown in the drawings a tubular element of one plurality proceeds in an over two and under two pattern of interweaving relative to the tubular elements of the second opposing plurality, with the interwoven position of any element being offset by one element with respect to its adjacent tubular elements of the same plurality. Another variation of an interlaced bundle is shown in FIGURE 8 in which the tubular elements are interlaced in the same general manner except that they are handled in groups of four elements. If the tubular elements are interwoven or braided together too tightly, a closed pattern with prohibitive resistance to fluid flow, unacceptable susceptability to plugging, and undesirable kinking of individual tubular elements is formed. On the other hand, if the tubular elements are interwoven or braided together too loosely, the bundle loses its desired coherence and compactness; also, the position of the elements relative to each other to maintain a desired uniform packing packing and resistance to fluid flow through the bundle cannot be established or maintained. It has been determined that a controlling factor is the .angle of intersection formed where tubular elements of one plurality cross over the elements of the other plurality. For tubular elements in the size ranges discussed above, and particularly for tubular elements of about mils outside diameter, this angle is preferably maintained between about 10 and about 60. The measurement of this angle is shown in FIGURE 5 at angle ABC or 0.

Formation of the interwoven bundles or sleeves is suitably accomplished on conventional well-known brading machinery with a few minor modifications obviously necessary to adapt them from small solid wires or yarns to the small hollow tubular elements utilized in the apparatus of this invention. One example of a satisfactory arrangement generally suitable for forming the interlaced bundles of this invention is disclosed in Catalog 56 (ELF-20004-1M-l164) on Braiders of the New England Butt Co., 304 Pearl Street, Providence, R.I. Preferably, braided or interlaced bundles are formed with end portions in which the tubular elements are substantially parallel (not interlaced) to facilitate construction of the tube sheet TS (FIGURE 4) or end construction suitable for forming the necessary header arrangement of a heat exchange apparatus (such as disclosed in abovementioned U.S. Patents 3,228,456 and 3,277,959). This is accomplished by periodically ceasing the braiding or interlacing action as a long length of bundles of tubular elements is being produced.

As shown in FIGURES 1, 4 and 6, the configuration and/ or position of the bundle of tubular elements as a Whole can be controlled or maintained by the use of a rigid unit inserted within the bundle. This unit may, if desired, be hollow and provided with suitable orifices 33 so fluid can be circulated through the unit into the bundle to improve fluid circulation and distribution within the bundle. Specifically, in FIGURE 1 the unit 32 in a U-shaped configuration within the bundle maintains the bundle configuration and position. Unit 32 is connected to conduit elbow elements 31 and to other conduits elements 30 and 33 through which fluid is supplied into the bundle interior as shown. As further illustrated in FIGURE 1, the tube bundle 20 and rigid supporting unit 32 are held in position relative to each other and relative to the wall elements 1 1 of the housing by means of a bracket assembly comprising elements 40, 42, and 43, all held in place by bolts 44 and 41. In FIGURE 4 the rigid unit controlling the position of the bundle and improving fluid circulation comprises a hollow radial portion 310 and a hollow axial portion 312 having perforations or orifices 313.

In operation of the apparatus of FIGURE 1, a fluid at one temperature is passed through the housing by means of inlet 12 and outlet 13, while a suitable fluid at a significantly different temperature is passed through the tubular elements T of bundle by means of conduit elements 23, 24, and header units 21 to cause transfer of heat between the two fluids. In order to improve the fluid flow through the bundle 20 exteriorly of the tubular elements, a portion of the fluid at said one temperature may be circulated through the hollow rigid unit 32 and out of orifices 33 by means of supply conduit elements 33 and 30.

A modified version of heat transfer apparatus embodying principles of the invention is shown in FIGURE 2. This version corresponds to a tube-in-shell heat exchanger arrangement similar to that shown in the above mentioned US. Patent No. 3,228,456. In this version, braided or interlaced bundle of tubular elements similar to that shown in FIGURE 4 has been positioned in a shell or casing member 101 which is provided with inlet 105, outlet 106, and suitable header units 102 at each end thereof to permit circulation of fluid fro-m inlet 103 through the interiors of the tubular elements to the outlet 104. Suitable header constructions are disclosed in the above-mentioned US. Patents 3,228,456 and 3,277,- 959. If desired, a rigid unit 401 can be mounted in cooperation with shell inlet 105 as shown in FIGURE 2 and in engagement with the bundle of tubular elements to help maintain the position of the bundle and improve the handling of fluid supplied into the bundle as shown, by means of openings 403 and 404- in hollow unit 401. The enlarged showings of FIGURES 3 and 7 make the structure and function of this unit clear. Unit 401 functions as shown in the preferred version of FIGURE 2 to receive a portion of the inlet stream to the shell in its hollow portion, and conduct this portion of the inlet stream directly into the central portion of the tube bundle where it is distributed through openings 403. The other portion of the shell inlet stream passes through openings 404 directly into the shell outside of the hollow portion of unit 401. The direction of shell inlet flow is generally indicated by the arrows in FIGURE 7. The op eration of the FIGURE 2 version of the apparatus of the invention is believed to be apparent from the drawing; one fluid at a given temperature being passed within the casing member or shell 101 exteriorly of the tubular elements from inlet 105 to outlet 106 while a fluid at a different temperature is passed from header inlet 103 through the interiors of the tubular elements T to header outlet 104.

It is believed that the preceding description indicates that a novel improved heat exchanger apparatus has been provided in accordance with the objects of the invention.

Compared with the above-mentioned prior art heat exchanger combinations, this invention provides a simplified arrangement in which the flexible tubular elements themselves act as spacing means to maintain the position of the elements relative to each other along the bundle, and establish a substantially uniform packing and resistance to fluid flow necessary for good heat exchange relation ships. The invention provides a compact bundle which is also flexible and widely manipulatable in assembly, operation, and maintenance while preserving generally the important relationships of the tubular elements relative to each other. The new arrangement of this invention results in a heat exchanger apparatus which is less susceptible to plugging of shellside fluid flow, less susceptible to tubular element kinking or damage, and also inherently possesses better and more uniform heat transfer characteristics.

Although certain preferred embodiments of the invention have been described in detail in accordance with the Patent Law, many variations and modifications within the spirit of the invention will be obvious to those skilled in the art and all such are considered to fall within the scope of the following claims.

What is claimed is:

1. An improved heat exchanger apparatus comprising in combination: a casing member, said casing member provided with structure defining a fluid-containing chamber, said apparatus further comprising a bundle of small diameter, thin-walled, flexible, tubular elements having continuously hollow interiors and formed of an organic polymeric composition, said bundle extending through at least a portion of said chamber to cooperate with a fluid contained in said chamber, said apparatus further comprising supporting means cooperating with said bundle to support said bundle in said chamber, conduit means operatively connected with the interiors of said tubular elements to circulate a fluid therethrough and establish a heat transfer relationship with a fluid in said chamber, said bundle having at least a substantial portion thereof comprising a first plurality of tubular elements arranged in a given pattern, and a second plurality of tubular elements arranged in a similar opposed pattern, said elements of each plurality being interlaced in a substantially uniform manner to provide a coherent flexible bundle substantially stable in size, the extent of interlacing and number of tubular elements being such that a predetermined degree of packing and a predetermined resistance to fluid flow through said bundle exteriorly of said tubular elements, is provided to maintain said heat transfer relationship at effective levels.

2. The improved apparatus of claim 1 in which the tubular elements of one plurality cross over the engaged tubular elements of the other plurality to form included angles of intersection of between about 10 and 60.

3. The improved apparatus of claim 2 in which said first and second pluralities of tubular elements are arranged in symmetrically opposed patterns and are interwoven in a regular pattern to provide a braided bundle.

4. The improved apparatus of claim 3 in which said bundle comprises a number of layers each having interlaced pluralities of tubular elements.

5. The improved apparatus of claim 4 in which said layers are in the form of hollow sleeve arrangements of graduated sizes each positioned within sleeve arrangement of larger size to form a compact stable bundle.

6. The improved apparatus of claim 5 in which said bundle is elongated in form with end portions and the tubular elements at said end portions are substantially parallel and free of interlacing.

7. The improved apparatus of claim 1 in which the said supporting means comprises a substantially rigid reinforcing unit extending through said bundle and interengaged with said tubular elements to maintain the position of said bundle within desired limits in said chamber.

8. The improved apparatus of claim 7 in which said unit comprises a fluid passageway therethrough and orifices connected therewith for handling fluid supplied into said bundle exteriorly of said tubular elements.

9. The improved apparatus of claim 8 in which said unit is engaged and coextensive with a significant portion of the length of said bundle to maintain the desired position of the bundle and improved fluid circulation along said portion of the bundle length.

10. The improved apparatus of claim 5 in which said supporting means comprises an elongated substantially rigid unit projecting into and extending along within the innermost sleeve arrangement for a substantial portion of the length of the bundle in order to positively maintain the position and configuration of the bundle Within desired limits, said unit comprising a fluid passageway therethrough and orifices connected therewith for handling fluid supplied into said bundle exteriorly of said tubular elements.

ROBERT A. OLEARY, Primal Examiner.

10 A. W. DAVIS, JR., Assistant Examiner.

U.S. Cl. X.R.

Images