Support for heat exchange tubes

Abstract

Rows of heat exchange tubes are supported by transversely disposed support strips having a plurality of V-shaped members interconnected end to end in a manner so that said strips act as a structural member supporting the weight of the tubes and additional support elements from all rows above a given row. Each leg of each V-shaped member has a generally triangular tab bendable out of the plane of its associated leg.

Description

BACKGROUND

In a conventional heat exchanger such as a condenser, horizontal rows of tubes are supported at spaced points along the length of the tubes by support plates. A typical support plate is 3/4 inch thick. The support plates must be drilled to provide the holes through which the tubes will extend. Each tube must be guided through its hole in the support plate. Hence, the support plate envelops a band 3/4 inch long around the entire periphery of each tube in a manner whereby such band is unavailable for acting as a condensing or heat exchange surface. Each condenser or heat exchanger has a substantial number of such support plates at spaced points along the length of the tubes.

Because of the cost and time consuming effort involved in the use of a conventional support plate as the primary structural member, the present invention is directed to elimination of the conventional support plate.

SUMMARY OF THE INVENTION

One aspect of the present invention is an article of manufacture in the form of a tube support strip of sheet metal having a plurality of V-shaped members interconnected end to end. Each leg of each V-shaped member has a generally triangular tab bendable out of the plane of its associated leg.

Another aspect of the present invention is a tube bundle wherein a first row of tubes is supported by a first tube support strip as set forth above and a second row of tubes is supported by a second tube support strip as set forth above. The first support strip supports the second support strip so as to define a structural member supporting the weight of the tubes and wherein each support strip has line contact with each tube at two locations.

In addition to the advantages resulting from the elimination of conventional support plates in accordance with the present invention, a plurality of other advantages and unexpected results have been attained. Thus, the present invention significantly reduces welding operations, facilitates practical application of automated method of assembling rows of tubes, eliminates tube handling damage, reduces field assembly time, increases tube surface area available for heat transfer, increases the area available for tubing, provides a control for the flow of shell side effluent along the length of the tubes, etc.

It is an object of the present invention to provide a heat exchanger such as a condenser wherein conventional support plates are eliminated while at the same time providing a structural support for the weight of the tubes so that the tubes in a bottom row do not support the weight of the tubes in the rows thereabove.

Other objects will appear hereinafter.

For the purpose of illustrating the invention, there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIG. 1 is a perspective view of a portion of a pair of mating support strips in accordance with the present invention.

FIG. 2 is a partial exploded view of a shell half, two support strips and two rows of tubes.

FIG. 3 is a partial perspective view of a heat exchanger such as a condenser constructed in accordance with the present invention.

FIG. 4 is a partial side elevation view of a tube bundle showing the relative length of the tube support strips with respect to the diameter of the tubes.

FIG. 5 is a sectional view taken along the line 5--5 in FIG. 4.

FIG. 6 is a partial plan view of a heater constructed in accordance with the present invention.

FIG. 7 is a sectional view taken along the line 7--7 in FIG. 6.

FIG. 8 is a partial perspective view of support strips in accordance with the present invention showing the inner lock of the ends with a support frame when constructing a rectangular heat exchanger.

FIG. 9 is a sectional view of a heat exchanger in accordance with FIG. 8.

FIG. 10 is a diagrammatic longitudinal sectional view of a condenser constructed in accordance with the present invention.

Referring to the drawings in detail, wherein like numerals indicate like elements, there is shown a pair of mating tube support strips in accordance with the present invention each designated generally as 10. The support strips 10 are identical except for length. The support strips 10 are adapted to support rows of tubes 12 disposed within a shell 14. See FIG. 3.

Referring to FIG. 1, the tube support strips 10 are a strip of sheet metal such as stainless steel having a plurality of V-shaped members interconnected end to end. Each leg of each V-shaped member has a first hole 16 extending therethrough and a second hole 18 extending therethrough. The holes 16 are closer to the lower apex and the holes 18 are closer to the upper apex. There is provided a tab 20 associated with each of the holes 18. Each tab 20 is generally triangular shaped with its base being integral in one piece with its associated leg. Each tab 20 is adapted to be bent out of the plane of its associated leg.

Each of the support strips 10 is of the same length when used to support tubes of a heat exchanger such as a condenser which is rectangular. If the condenser is circular in cross-section, each strip 10 has a length which is slightly different from the length of the next adjacent strip. Each strip has a width which is between 1 and 2 times the diameter of the tubes 12 to be supported thereby. Stated differently, each of the strips has a width which is about 1 to 5 times its height. The height of the strips is designated by the arrow H in FIG. 5. The gauge of the material of strip 10 will vary with the size of the heat exchanger and will be of greater gauge as the size of the heat exchanger increases with the controlling factor being that the support strips cooperate with one another to serve as a structural support member for supporting the weight of the tubes thereabove. Since the lower tubes will not be supporting the weight of the tubes thereabove, removal and/or replacement of a lower tube is easily facilitated.

At spaced points along the length of the tubes, the support strips will be superimposed over one another with a row of tubes between each support strip. The linear distance between the locations where the tubes are supported by the support strips is preferably calculated in a manner well known to those skilled in the art so as to minimize vibrations in the tubes.

The support strips are preferably interlocated with the next adjacent support strip so as to preclude sidewise shifting of one support strip with respect to another. Such interlock is preferably attained at the location wherein one support strip contacts the next adjacent support strip, namely at the apexes. Thus, each upper apex is provided with a protrusion 22 and each lower apex is provided with a mating recess designated 24. See FIG. 1.

Referring to FIG. 2, there is shown the lower shell half 26 of a cylindrical condenser. At spaced points along the length of the shell half 26, there are provided lower support frames 28. An upper support frame 29 will be provided for each of the frames 28 as shown more clearly in FIG. 3. The support frames 28 are identical. Hence, only one such support frame 20 will be described in detail.

The support frame 28 is generally semi-circular with a plurality of steps on its uppermost surface. The largest step is designated 30 and is in the middle of the frame 28 so as to be directly below the longitudinal axis of the shell half 26. The remaining steps designated 32 are shorter in length than the length of step 30. A first support strip 10a is provided having a length corresponding to the length of step 30. With a support strip 10a on each of the steps 30, a first row 34 of tubes 12 are placed over the support strips 10a. It will be noted that the number of tubes in row 34 corresponds to the number of V-shaped recesses on the upper surface of strip 10a.

Thereafter, a support strip 10" is placed over the row 34 at each of the locations of step 32 on the frames 28. The protrusions 22 on the strip 10a interlock with the recesses 24 on the strip 10b. The number of V-shaped recesses on the upper surface of strips 10b corresponds to the number of tubes 12 in row 36. The sequence is then repeated using correspondingly increased lengths of strips 10 and a larger number of tubes 12 in the various rows.

Each of the strips engage the tubes juxtaposed thereto with line contact at two locations on the tubes 12. As will be apparent from FIG. 5, the height H of the V-shaped support strips is slightly greater than one half the diameter of the tubes 12 so that the respective support strips cooperate with one another to provide a structural support for the weight of the tubes thereabove. As shown in FIG. 4, the width of the strips 10 is between 1 and 2 times the diameter of the tubes 12.

In FIG. 6, there is illustrated a heater 38 having a cylindrical shell with a plurality of tubes 44 supported by strips 10, 10a, 10b, as described above. The direction of flow within the shell and exteriorly of the tubes 44 is designated by the curved arrows in FIG. 6 and attained by staggered barriers 40, 42, etc. The barriers 40 and 42 are attained by bending the tabs 20 upwardly on one side of the shell and permitting the tabs 20 on the other side of the shell to remain in the plane of their respective legs. See FIGS. 5 and 7 wherein some of the tabs 20 are bent upwardly while others remain in the plane of their leg. Thus, the present invention provides an unexpected benefit in being able to control longitudinal flow on the shell side in connection with cascading-flow heat exchangers such as a feed water heater.

Referring to FIGS. 8 and 9, the present invention is adaptable for use with heat exchangers that are rectangular in cross-section. In a rectangular shell 50, there will be provided vertically disposed frame members 46 at spaced points therealong in the same manner that frames 28 were provided as described above. All, or substantially all, of the support strips 10 will be of the same length and will have notches 48 at their ends for receiving the frame members 46. Notch 48 is attached by cutting across a hole 16. The cooperation between frame 26 and notches 48 automatically prealigns the support strips 10 so that each protrusion 22 will be juxtaposed to a recess 24 on the next adjacent support strip. As shown in FIG. 9, the vertical height between the support strips corresponds to the diameter of the tubes 12 so that each tube has line contact with a support strip at four different locations.

Referring to FIG. 10, there is diagrammatically illustrated a typical surface condenser 49. The condenser 49 includes a shell 52 having a vapor inlet 54 and a condensate outlet 56. A coolant inlet 58 is connected to a tube sheet at one end of the shell 52. A coolant outlet 62 is connected to a tube sheet 64 at the other end of the shell 52. The tubes 12 are supported at their ends and are sealed to the tube sheets 60, 64.

As shown in FIG. 10, the tube bundle defined by the tubes 12 and their frames 28, 29 is constructed as set forth above with support strips between the various rows of tubes. The frames 28, 29 retain the tube bundle in an assembled relationship prior to securing the ends of the tubes 12 to the tube sheets 60, 64.

A unique feature of the present invention lies in the ability to control the flow of the shell side effluent along the lengths of the tubes. Such flow is in a direction reverse to the direction of flow through the tubes 12. As illustrated in FIG. 10, the proper orientation of a surface condenser requires that the major outermost portion of the bundle is constructed such that longitudinal flow is retarded thereby forcing the shell side effluent (typically steam) to penetrate into the center of the bundle toward the cooler zone designated 66 in each section of the bundle between the frames 28, 29. This penetration assures optimum effectiveness of the total surface area of the tubes and tends to form a collection area for the non-condensable vapors. In the cooler zone 66, longitudinal flow of vapors is promoted by permitting the tabs 20 to remain in the plane of the leg of their V-shaped member while bending the tabs 20 to a position perpendicular to their associated leg in the outer peripheral portions of the tube bundle.

As shown in FIG. 10 and described above, longitudinal flow is promoted such that non-condensable vapors (such as air) is directed toward a terminal collection point adjacent tube sheet 60. A terminal collection point is sometimes called a terminal cooler. Since the retardation and promotion of longitudinal flow is controlled by the simple manipulation of the position of the tabs 20, significant advantages are realized. For example, the more conventional cooler required that a certain region not contain or be devoid of tubes. This region required openings in the conventional support plate for the required longitudinal flow of non-condensable vapors. Some structural hardware was required to act as baffles and force the non-condensable vapors to contact tubes in its path to the terminal cooler so that any entrained condensable vapor that remained may be condensed. Such longitudinal flow is now easily promoted using the present invention whereby the previously untubed region can now be fully tubed allowing for a more efficient design.

The present invention whether in the form of a tube support structure, a tube bundle incorporating such support strips, or in a heat exchanger such as a condenser incorporating such tube bundle, provides for a multiplicity of advantages and unexpected results. As used herein, the word "fluid" is used on a broad sense so as to cover liquids and gases. The tube support strips while maintaining the spacing between tubes of the same row and tubes of adjacent rows provides for maximum heat exchanger efficiency since a larger surface of the tubes is exposed to the shell side effluent. In addition, the tube support strips serve as a structural member supporting the weight of the tubes and the support elements from all rows above a given row. There is a tendency for the tube support strip to act as a fin for promoting conductive heat transfer between the tube and the tube support element and convective heat transfer to the shell side effluent.

The conventional method of drilling holes in support plates and inserting tubes through such holes is difficult, time consuming, and expensive. The present invention eliminates the use of drilled tube support plates. As a result thereof, it is now practical to automate the dispensing of tubes and the assembly of a heat exchanger such as a condenser. Tube support strips are placed in a shell, and then a row of tubes is dropped onto the tube support strips. The process is repeated thereby substantially increasing production capability and reducing manufacturing costs. The present invention has advantages in reducing field assembly time which is of particular importance on large surface condensers which typically serves steam turbines of a nuclear fuel power plant or the like. Thus, the present invention lends itself to assembling the condensor at the job site as well as permitting preassembly of the tube bundle in the factory for shipment to the job site.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

Claims

1. Apparatus for providing heat exchange between the first and second fluids comprising a shell supporting a tube bundle having a plurality of rows of parallel tubes in said shell, means defining a fluid inlet for one end of said tubes and for defining a fluid outlet for the other end of said tubes so that said first fluid may flow through said tubes, said shell having an inlet and an outlet for a second fluid to be in surface contact with the outer periphery of said tubes, at spaced points along the lengths of said tubes the tubes being supported by discrete tube support strips disposed between rows of the tubes, each support strip having a plurality of V-shaped members interconnected end to end with each leg of each V-shaped member having a generally triangular tab bendable out of the plane of its associated leg for selective control of flow of said second fluid in a direction longitudinal of said tubes.

2. Apparatus in accordance with claim 1 wherein some of said tabs are bent so as to be perpendicular to their associated leg and others of said tabs remain in the plane of their associated leg.

3. Apparatus in accordance with claim 2 wherein the tabs that are bent so as to be perpendicular to their associated leg are adjacent the outer peripheral portions of said tube bundle with the tabs remaining in the plane of their associated leg being adjacent the central portion of the tube bundle.

4. An article of manufacture comprising at lease two (a) tube support strips of corrosion resistant material each having a plurality of V-shaped members interconnected end to end, releasable interlock means on a plurality of the apexes of said members to facilitate interlocking said strips with another in a manner so that a plurality of diamond-shaped openings are provided therebetween for accommodating horizontally disposed heat exchange tubes, said means including an integral projection on each of a plurality of apexes and a mating hole in adjacent apexes, each projection being integral in one piece with its associated apex in a manner so as to enable juxtaposed apexes to be in line contact.

5. An article in accordance with claim 4 wherein each leg of each V-shaped member has a generally triangular tab between adjacent apexes, each tab being bendable out of the plane of its associated leg along an edge of the tab which is generally parallel to the longitudinal side edge of its associated member.

6. An article in accordance with claim 4 wherein said strip has a width at least as large as its height.

7. A tube bundle comprising a first tube support strip horizontally disposed and having a plurality of V-shaped members interconnected end to end, a first row of horizontally disposed tubes supported by said strip with each tube being in line contact at two spaced locations with each leg of the V-shaped member therebelow, a second tube support strip overlying said first row of tubes and aligned with said first mentioned strip, said strip having a plurality of V-shaped members interconnected end to end, means including a lower apex on said second strip removably interlocked with an upper apex of said first strip so that only said strips cooperate to structurally support the load of tubes thereabove and with line contact between the juxtaposed apexes whereby tubes of said first row may be removed longitudinally without disturbing tubes of said second row, and the V-shaped members on said first mentioned strip cooperating with the V-shaped members on said second strip to define diamond-shaped openings through which said tubes extend.

8. A tube bundle in accordance with claim 7 wherein each V-shaped member has a bendable tab, each tab being bendable to a position wherein it occupies substantially all of the space between a tube and adjacent mating apexes within one of said diamond-shaped openings.

9. A tube bundle in accordance with claim 7 wherein the number of tubes in alternate rows is the same, and parallel structural members associated with the ends of the strips for retaining the strips in superimposed relation.

10. In heat exchange apparatus comprising a shell containing parallel rows of heat exchange tubes, support structure within said shell for maintaining correct lateral spacing of the tubes and serving as a structural member for supporting the weight of the tubes thereabove, said support structure being defined by a plurality of superimposed, horizontally disposed strips of sheet metal, each strip having a plurality of V-shaped members interconnected end to end, the V-shaped members on one strip cooperating with the V-shaped members on the next adjacent strip to define generally diamond-shaped openings, mating structure on juxtaposed apexes of said strips for removably interlocking adjacent strips with the juxtaposed apexes having line contact, said mating structure on juxtaposed apexes including a protrusion on and integral in one piece with one apex and a mating recess on the adjacent apex, each diamond-shaped opening accomodating one of the tubes, the outer peripheral surface of each tube having line contact with each leg of the V-shaped member therebelow.

11. Apparatus in accordance with claim 10 including a support frame within said shell, said support frame having steps on its inner peripheral surface, each support strip having its ends supported by a pair of said steps.

12. Apparatus in accordance with claim 10 including a tab integral at one end with each leg of said V-shaped members, each tab being bendable out of the plane of its associated leg so that it may occupy a portion of one of said diamond-shaped openings adjacent thereto.

13. Apparatus in accordance with claim 10 including means in said shell cooperating with mating structure on the ends of said strips for aligning said strips.

14. A tube bundle in accordance with claim 7 wherein said strips have a width which is between 1 and 2 times the diameter of said tubes.