GB2175078A

GB2175078A - Heat exchanger with antivibration structure

Info

Publication number: GB2175078A
Application number: GB08512578A
Authority: GB
Inventors: David John Shepherd
Original assignee: National Nuclear Corp Ltd
Current assignee: National Nuclear Corp Ltd
Priority date: 1985-05-17
Filing date: 1985-05-17
Publication date: 1986-11-19
Also published as: IT1189668B; GB2175078B; IT8653424V0; IT8667409A0; FR2582093A1; GB8512578D0; FR2582093B1

Abstract

Flow induced vibration of heat exchanger U-tubes (10) is minimised by the use of generally V-shaped antivibration bars (16-26) inserted into the tube bundle at the U-shaped sections thereof, the bars inserted into alternate gaps between adjacent layers of tubes being staggered with respect to those inserted into the adjacent gaps. All of the antivibration bars (16-26) are interference fits between the tube layers so as to elastically deflect the tubes (10) thereby ensuring positive tube support at each intersection between the tubes (10) and bars (16-26). <IMAGE>

Description

SPECIFICATION Heat exchanger with antivibration structure This invention relates to a heat exchanger of the kind comprising a bundle of U-shaped heat exchange tubes arranged in layers with antivibration elements located between adjacent layers in the region of the U-shaped sections of the tubes so as to support these sections against flow induced vibrations which may otherwise lead to tube failure as a result fretting or fatigue. Such a heat exchanger is herein referred to as a heat exchanger of the kind specified.

Such heat exchangers are well known in the art. One form of antivibration structure is disclosed in, for example, US Patent No 3007679 and comprises a series of V-shaped spacer members disposed between layers of heat exchange tubes and arranged with their apical portions disposed adjacent the innermost of the U-shaped heat exchange tubes, all of the spacer members being aligned with one another as viewed along an axis passing through their apices. Other possibilities are discussed in an article "The Effect of Flat Bar Supports on the Crossflow Induced Response of Heat Exchanger U-Tubes" by Weaver et al, Journal of Engineering for Power, October 1983, Vol. 105, pp. 775-781.Fig. 1(e) and the related description in the latter reference are concerned with the use of flat antivibration bars and the possibility is mentioned of using the flat bars in a staggered relation. Such bars are stated to give the best experimental results with small but non-zero clearance.

The object of the present invention is to provide an improved heat exchanger construction incorporating antivibration means.

According to the present invention there is provided a heat exchanger of the kind specified in which antivibration elements are inserted between adjacent layers such that the elements in alternate gaps between the layers are staggered with respect to those in the intervening gaps between layers and in which said elements are inserted as interference fits whereby, by virtue of the staggered relation, the U-shaped sections of the tubes are subjected to bending within the elastic limit.

Thus, whilst it has already been proposed to employ staggered antivibration bars with non-zero clearance, the present invention employs a staggered relation in conjunction with interference fitting of the antivibration elements. In this way, the U-shaped tube sections are caused to bend elastically thereby ensuring that active support is provided at the intersections between the tubes and the antivibration elements.

To promote further understanding of the invention, an embodiment will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a fragmentary view showing part only of one layer of heat exchange tubes, only some of the tubes being shown for the sake of clarity; Figure 2 is a schematic developed view of the U-shaped sections of the tubes lying in a series of planes; and Figure 3 is a sectional view taken in the direction A-A in Fig. 1, again only some of the tubes being illustrated for the sake of clarity.

The overall construction of the heat exchanger is not illustrated but may be generally as shown in US Patent No. 3007679 particularly with respect to the arrangement of the U-shaped tubes in layers with more tubes in the central layers and decreasing numbers in the layers above and below the central layers and with tubes having concentrically related Ushaped sections of differing radii of curvature whereby the outermost U-shaped sections collectively define a generally (but stepped) hemispherical structure.

Fig. 1 illustrates part only of some of the tubes 10 lying in one layer of the tube bundle.

The line 12 indicates the position of the partition member closest to the U-shaped sections of the tubes, there being a series of partition members spaced lengthwise of the heat exchanger and through which the straight legs of the tubes pass.

In the alternate gaps 1 (see Fig. 3) between adjacent tube layers are disposed three sets of antivibration bars 16, 18, 20 and in the intervening gaps 22 (see Fig. 3) are disposed two sets of antivibration bars 24, 26. The antivibration bars in each set 16, 18, 20, 24 or 26 are all substantially coplanar with each other and are of generally V-shaped configuration with the apices disposed as shown in Fig.

1. The bars 24, 26 are staggered with respect to the bars 16, 18, 20 so that each half of the U-shaped tube section is supported at three positions on one side and two staggered positions on the other side.

Although the bars are shown as being of round section they may be of other section, eg. square or rectangular. Whatever section is employed, it is important that the dimensions are such that an interference fit between the tubes in adjacent layers is obtained so that the staggered contact positions result in a slight amount of bending, within the elastic limit, of the tubes in these regions. In this way, positive support is provided at the tube/bar intersections and, in addition, the staggered arrangement means that the tubes are supported at an increased number of positions. Although, as shown, three and two sets of alternate antivibration bars are employed, the number of sets may differ from those il lustrated, eg. there may be one and two sets instead of three and two.

Fig. 3 illustrated how each set of bars is located and retained within the tube bundle.

The bars of each set all project beyond the tube bundle and the projecting ends are secured together by a retaining ring 30 which is itself retained in position by retaining bars 32 fastened to the ring at 34 and trapped by an outermost layer of tubes.

Claims

1. A heat exchanger of the kind specified characterised in that antivibration elements are inserted between adjacent layers such that the elements in alternate gaps between the layers are staggered with respect to those in the intervening gaps between layers and in which said elements are inserted as interference fits whereby, by virtue of the staggered relation, the U-shaped sections of the tubes are subjected to bending within the elastic limit.

2. A heat exchanger as claimed in Claim 1 characterised in that the antivibration elements are V-shaped and are inserted between the layers of tubes with their apices leading and their ends trailing.

3. A heat exchanger as claimed in claim 1 or 2 characterised in that the antivibration elements are V-shaped and have differing angles at their apices.

4. A heat exchanger as claimed in Claim 1, 2 or 3 in which said antivibration elements are of round section.

5. A heat exchanger as claimed in Claim 1, 2 or 3 in which said antivibration elements are of square or rectangular section.

6. A heat exchanger substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.