Tube Sheet Assembly for a Heat Exchanger

Abstract

A tube sheet assembly for a heat exchanger is disclosed. The tube sheet assembly includes a plastic sheet having multiple tube-retention holes defined therein and a metal plate having multiple holes defined therein, each hole being substantially coaxial with a corresponding tube-retention hole of the plastic sheet. The metal plate is connected to the plastic sheet. The metal plate can be fabricated of, for example, steel or other metals. The plastic sheet can be fabricated of, for example, nylon, ultra-high-molecular-weight polyethylene, or polytetrafluoroethylene. Tubes can be disposed in the tube-retention holes of the plastic sheet and the holes of the metal plate. In an example, the tube-retention holes of the plastic sheet have a smaller diameter than the holes of the metal plate and the tubes contact the plastic sheet without contacting the metal plate.

Description

FIELD OF THE DISCLOSURE

The disclosure relates to heat exchangers.

BACKGROUND OF THE DISCLOSURE

A heat exchanger is designed to transfer heat from one medium to another. Heat exchangers generally have several tubes to carry one of these media, and the design often includes where the tubes pass through headers or other plates. These headers or other plates can be used to, for example, separate or position the tubes within the heat exchanger.

Headers and plates that position the tubes are usually fabricated of metal. This presents multiple problems. First, the header or plate may have a different coefficient of thermal expansion than the tubes, which can lead to stress or damage on the components due to expansion or contraction. Second, the header or plate can cause abrasion to the tubes during installation as the tubes are moved into position through the plate or header. Third, the header or plate can be expensive depending on its thickness or dimensions.

A common technique for mitigating the above problems is through the use of a ferrule around each tube and at each tube-to-header interface. In this way, the ferrule can prevent damage to the tube due to expansion, contract, abrasion, etc. However, the use of ferrules can significantly increase the cost of the resulting heat exchanger in both materials and labor in assembly.

BRIEF SUMMARY OF THE DISCLOSURE

A tube sheet assembly for a heat exchanger is disclosed. The tube sheet assembly includes a plastic sheet having multiple tube-retention holes defined therein and a metal plate having multiple holes defined therein, each hole being substantially coaxial with a corresponding tube-retention hole of the plastic sheet. The metal plate is connected to the plastic sheet. The metal plate can be fabricated of, for example, steel or other metals. The plastic sheet can be fabricated of, for example, nylon, ultra-high-molecular-weight polyethylene, or polytetrafluoroethylene. Tubes can be disposed in the tube-retention holes of the plastic sheet and the holes of the metal plate. In an example, the tube-retention holes of the plastic sheet have a smaller diameter than the holes of the metal plate and the tubes contact the plastic sheet without contacting the metal plate.

DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the disclosure, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1A is a side elevation view showing an example of a header plate and tubes according to an embodiment of the present disclosure;

FIG. 1B is a detail view of a portion of the header plate and tubes of FIG. 1A;

FIG. 2 is a perspective view of tube sheet assembly in accordance with another embodiment of this disclosure;

FIG. 3A is an exploded perspective view of the tube sheet assembly of FIG. 2;

FIG. 3B is a detail view of a portion of the tube sheet assembly of FIG. 3A; and

FIGS. 4A and 4B shows an embodiment of this disclosure in which tubes are inserted through the tube sheet assembly.

DETAILED DESCRIPTION OF THE DISCLOSURE

Although claimed subject matter will be described in terms of certain embodiments, other embodiments, including embodiments that do not provide all of the benefits and features set forth herein, are also within the scope of this disclosure. Various structural, logical, process step, and electronic changes may be made without departing from the scope of the disclosure.

The presently-disclosed tube sheet assembly is used in a heat exchanger to position or separate tubes that carry a heat transfer medium. The tube sheet assembly may be used as a header plate, such as that illustrated in FIG. 1, or other plates that position tubes in the heat exchanger. Multiple tube sheet assemblies can be used in a single heat exchanger.

As seen in FIGS. 2, 3A, and 3B, an embodiment of the presently-disclosed tube sheet assembly 10 includes a plastic sheet 12 having a plurality of tube-retention holes 20 defined therein. Each tube-retention hole 20 has a diameter which is substantially the same as an outside diameter of a heat-exchanger tube 13. In some embodiments, substantially similar diameters provides that the tube may be inserted through each tube-retention hole 20, while still being held stationary in a transverse direction within the hole 20.

The tube sheet assembly 10 further includes a metal plate 11 has a plurality of holes 22 defined there, each hole 22 substantially coaxial (as further defined below) with a corresponding tube-retention hole 20 of the plastic sheet 12. Each hole 22 of the metal plate 11 has a diameter which is greater than the diameter of the tube-retention holes 20 of the plastic sheet 12. Tubes 13, which may be copper, aluminum, alloys thereof, or other materials, can be passed through the tube sheet assembly 10. The centers of the holes in the plastic sheet 12 and metal plate 11 may be aligned (i.e., coaxial). In other embodiments, the tube-retention holes 20 of the plastic sheet 12 are not coaxial with the holes 22 of the metal plate 11, although the tube-retention holes 20 may be configured such that a tube 13 disposed through a tube-retention hole 20 of the plastic sheet 12 and a corresponding hole 22 in the metal plate 11 is not in contact with the metal plate 11 (i.e., the holes 20, 22 are considered to be “substantially coaxial”). The tube-retention holes 20 of the plastic sheet 12 and the holes 22 metal plate 11 may be the same diameter or different diameters. In some embodiments, the tube-retention holes 20 in the plastic sheet 12 may have a smaller diameter than the holes in the metal plate 11.

The plastic sheet 12 may be fabricated of nylon, ultra-high-molecular-weight polyethylene, polytetrafluoroethylene, or other materials. The plastic sheet 12 may be softer and/or more flexible than the metal plate 11.

The metal plate 11 may be fabricated of steel or other materials. For example, stainless steel or zinc-plated steel (i.e., galvanized steel) may be used. This metal plate 11 provides support for the plastic sheet 12 and prevents the plastic sheet 12 from drooping, warping, sagging, or otherwise moving out of a desired position.

The plastic sheet 12 and metal plate 11 are connected to one another. For example, the plastic sheet 12 and the metal plate 11 may be connected using fasteners such as pop rivets, bolts, screws 24, or other devices known to those skilled in the art. In other embodiments, the plastic sheet 12 and metal plate 11 may be connected using an adhesive. Other techniques for connecting the components can be used.

In an embodiment, the tubes contact the plastic sheet 12 without contacting the metal plate 11 when assembled. FIGS. 4A-4B illustrate the tube sheet assembly from both the side of the plastic sheet 12 (FIG. 4B) and the metal plate 11 (FIG. 4A). The tube sheet assembly of FIGS. 4A-4B can correspond to the tube sheet assembly 10 in FIGS. 2 and 3. The plastic sheet 12 is illustrated as white in FIGS. 4A-4B. As seen in FIGS. 4A-4B, the tubes contact the plastic sheet 12 and not the metal plate 11. As shown in FIG. 4A, there is a gap between the exterior of the tubes and the circumference of the holes in the metal plate 11. The holes in the metal plate 11 are larger in diameter than the corresponding holes in the plastic sheet 12. The diameter of the holes in the plastic sheet 12 may be approximately the same as the outer diameter of the tubes. In various embodiments, the diameters may differ to provide, for example, ease of installation, proper positioning, friction fit, or a desired amount of expansion or contraction.

The tube sheet assembly 10 enables movement of the tubes 13 through the plastic sheet 12 without damage or wear to the material of the tubes 13 due to the flexible or yielding nature of the plastic in the plastic sheet 12. Furthermore, the plastic sheet 12 allows the tubes 13 to expand during operation without causing damage or wear due to the flexible nature of the plastic. Minimizing or eliminating contact between the tubes and the metal plate 11 reduces or eliminates the possibility that the heat exchanger tubes will be worn through due to vibration. The plastic sheet 12 is less expensive than the metal plate 11, so the combination of the plastic sheet 12 and metal plate 11 lowers the overall material cost of the tube sheet assembly 10 compared to one made of only metal. Ferrules can be avoided through use of the plastic sheet 12. Removing ferrules eliminates rattling where tubes vibrate against the ferrule and tube sheet assembly. Use of the plastic sheet 12 also eliminates known issues related to a bi-metallic interface when two different metals are used for the tubes and for the metal plates in previous designs.

Although the present disclosure has been described with respect to one or more particular embodiments, it will be understood that other embodiments of the present disclosure may be made without departing from the spirit and scope of the present disclosure. Hence, the present disclosure is deemed limited only by the appended claims and the reasonable interpretation thereof.

Claims

1. A tube sheet assembly for a heat exchanger, comprising: a plastic sheet having a plurality of tube-retention holes defined therein, wherein each tube-retention hole has a diameter substantially the same as an outside diameter of a heat-exchanger tube; anda metal plate attached to the plastic sheet, the metal plate having a plurality of holes defined therein, each hole coaxial or substantially coaxial with a corresponding tube-retention hole of the plastic sheet.

2. The tube sheet assembly of claim 1, wherein the metal plate is fabricated of steel.

3. The tube sheet assembly of claim 1, wherein the plastic sheet is fabricated of nylon, ultra-high-molecular-weight polyethylene, or polytetrafluoroethylene.

4. The tube sheet assembly of claim 1, further comprising a plurality of heat-exchanger tubes disposed through the holes of the plastic sheet and the holes of the metal plate.

5. The tube sheet assembly of claim 4, wherein the holes of the plastic sheet have a smaller diameter than the holes of the metal plate.

6. The tube sheet assembly of claim 5, wherein the tubes contact the plastic sheet and do not contact the metal plate.