US 3595309 A
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United States Patent Inventor Ronald J. Hawkins Morden, Surrey. England App]. No. 846,095 Filed July 30, 1969 Patented July 27, 1971 Ass ignce Babcack 8: Wilcox, Limited London, England Priority July 31, 1968 Great Britain 36565/68 HEAT EXCHANGER WITH HELICALLY COILED TUBES 7 Claims, 5 Drawing Figs.
US. Cl 165/162,
Int. Cl F28d 7/02, F28f 9/00 Field oISearch 165/172,
 References Cited UNITED STATES PATENTS 1,852,363 4/1932 Parent 165/162 2,980,404 4/1961 Andersen ct a1... 165/162 X 3,286,767 11/1966 Evans 165/163 X Primary Examiner-Albert W. Davis, Jr. Attarney.l. Maguire SHEET 2 OF 3 PATENTEU JUL27 l97| HJHTJ R N MD I HIM/(1N5 In van (or A llom sy HEAT EXCHANGER WITH HELICALLY COILED TUBES BACKGROUND AND SUMMARY OF THE INVENTION This invention relates to heat exchangers and is particularly concerned with heat exchangers containing a bank of tubes in the form ofa plurality of concentric helices.
It is common practice tov maintain the desired spacing between the tubes by use of spacer bars. Several, say four, spacer bars are distributed around each helix and serve to establish the desired spacing between the convolutions of the helix with which they are associated. The spacer bars of each helix are aligned with the spacer bars of the next to form rows extending radially of the helices and, to maintain thedesired spacing between the helices, the aligned spacer bars touch each other continuously along their lengths.
Now when the heat exchanger is in operation, the spacer bars expand thermally so that their radial extent will increase. The differential expansion between the rows of spacer bars and the tubes will be such as to deform the tubes; in an arrangement in which the spacer bars form four radial rows each perpendicular to the next and extending outwardly from a central support the tubes will tendto become deformed from their original circular plan towards a square plan with the rows of spacer bars lying along the diagonals.
An object of the invention is to minimize the tendency for deformation of the tubes to result from differential expansion of the tubes relatively to the spacer bars. I
According to the present invention, there is provided a heat exchanger having a bank of tubes in the form of a plurality of concentric helices provided with spacer means, wherein the spacer means includes, for each helix, a plurality of spacer bars distributed around the helix and each aligned with a spacer bar of the next adjacent helix so that rows of spacer bars extend radially of the concentric helices, each spacer bar in each row is separated from the next spacer bar in the row, the separation between each two spacer bars that are adjacent each other in a row is maintained by a set of distance pieces acting between the adjacent spacer bars and separated from each other lengthwise of the spacer bars, and, for any spacer bar lying between two other spacer bars, the distance pieces of the set that act between that spacer bar and one of the other two spacer bars are staggered relatively to the distance pieces of the set acting between that spacer bar and the other of the other two spacer bars.
The invention can therefore be readily summarized as the combination, in a heatexchanger, of a plurality of helically coiled heat exchanger tubes arranged in concentric relation to one another, plural interconvolution spacer means connectively associated with each tube coil to establish the spacing between adjacent convolutions thereof, and radially projecting spacer means connectively associated with each interconvolution spacer means and disposed for engagement with at least one element of the combination consisting of an adjacent tube coil and an interconvolution spacer means associated with such adjacent tube coil, to establish the radial spacing between each pair of adjacent tube coils.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawing and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.
BRIEF DESCRIPTION OF THE DRAWING In the drawing:
FIG. I is a schematic axial section view of a pressure vessel and a heat exchanger therein constructed in accordance with a preferred embodiment of the invention and having helically coiled heat exchanger tubes that are suspended from a central column or spine element.
FIG. 2 is a cross-sectional plan view of the heat exchanger shown in FIG. 1 as taken along line 11-" therein.
FIG. 3 is an elevation view, partly in section, of a typical portion of the heat exchanger shown in FIG. 2 as taken along line III-Ill therein.
FIG. 4 is an elevation view similar to that of FIG. 3, but showing a modification of the tube coil spacing arrangement therein according to another embodiment of the invention.
FIG. 5 is a plan view of the detailed structure shown in FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION In FIG. I helically coiled tubes 1 of the heat exchanger are mounted in space, or pod, formed by the concrete pressure vessel 2. The tubes of the heat exchanger form concentric helices suspended from a support3 which is carried by a tubular column or spine 6 which extends through the center of the helices. High pressure gas from a reactor core (not shown) en ters the vessel at opening 4 and the cooled gas returns to the core through opening 5.
As shown in FIGS. 2 and 3 the interconvolution separation in the tube helices 7a, 7b, and 7c is maintained by spacer bars I3, l4, l5 and sets 9a, 9b, 9c of distance pieces. There are four spacer bars connected to each helix and distributed equiangu- Iarly around it. Each spacer bar is of spectacle plate" formation, consisting of two strips 13a and 13b, 14a and 14b, 15a and 15b clamped edge-to-edge. The strips have similar cooperating recesses 16 lying in pairs forming aperturesv through which the convolutions of the tube helix pass. The spacer bars are connected at their upper ends to the support 3 that is carried by the column or spine 6 as shown in FIG. I.
The spacer bars of all the helices are aligned to form four radial rows A, B, C, and D, (FIG. 2). The distances pieces of set 912, FIG. 3, are welded at equal intervals along spacer bar 13 and extend across the gap between bars 13 and 14 to abut the latter.
The distance pieces of set are welded at equal intervals along spacer bar 14 and extend across the gap between bars 14 and I5 to abut the latter. The distance pieces of set 9a are welded to the tubular column or spine 6 and extend across the gap between the spine and the bar 13 to abut the latter. Each distance piece of set 9c lies midway between two adjacent distanced pieces of set 9b and each distance piece of set 9b lies midway between two adjacent distance pieces of set 9a.
If there were no distance pieces and the spacer bars abutted, continuously along their lengths against each other and the central column or spine then, when heated, the spacer bars would be subjected to stresses such that the cross section of the tube coils would tend to become rectangular rather than circular. The staggering of the distance pieces permits the spacer bars, when heated, to deform somewhat and bow between the distance pieces so that the stresses on the coils are less than those that would occur if the spacer bars abutted each other and the central column or spine continuously.
In the modification shown in FIGS. 4 and 5, each distance piece is formed by two plates Ila and llb. The end 12a of each plate is welded to a spacer bar and the end 12b abuts a tube passing through the next adjacent spacer bar which lies between the ends 12b. Thus, the spacer means is formed partly of a material at the gas temperature and partly by the tubes which are continually cooled. An advantage of this arrangement is that the total radial expansion of the spacer means is less than that of the spacer means shown in FIG. 3.
From the'foregoing it can thus be appreciated by the artisan that the inventioncan be considered as the combination, in a heat exchanger, of a plurality of helically coiled heat exchanger tubes 1 arranged in concentric relation to one another, as along helices 7a, 7b, 7c; plural interconvolution spacer means, i.e. bars l3, 14, I5, connectively associated with each tube coil 7a, 7b, 70 respectively to establish the spacing between adjacent convolutions thereof; and radial spacer means 9b, 9c, or alternatively 11. In one example given, the radial spacer means. the distance pieces 9b, 9c, are connected to interconvolution spacer bars 13 and 14 respectively and are disposed for abutting engagement with the interconvolution spacer bar l4, 15 associated with an adjacent tube coil 7b, 70, with the radial spacing between support column or spine 6 and tube coil 7a being established by radially projecting distance pieces 911 connected to spine 6 itself. ln the other example, represented by FIGS. 4 and 5, the radial spacer means are in the form of radially projecting pairs of plates 11a, llb which are connected to the interconvolution spacer bars 14 and 15, and engage the tube coils 7b, 7a (not shown). The common feature between these different embodiments thus lies in the fact that for each pair of adjacent tubes coils selectable out of the combination of tube coils 7a, 7b, 7c, the radial spacing therebetween is established by radially projecting spacers connected to intcrconvolution spacers associated with one tube coil of the pair, and disposed for abutting engagement with interconvolution spacers associated with the other tube coil of the pair and/or such other tube coil itself.
While in accordance with the provisions of the statutes there is illustrated and described herein a specific embodiment of the invention, those skilled in the art will understand that changes may be made in the form of the invention covered by the claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features.
What I claim is:
1. In a heat exchanger, the combination comprising an upright cylindrical pressure vessel, a bank of tubes in the form of a plurality of concentric helices provided with spacer means, a tubular column extending through the center of the helices, support members connected to and extending radially of said tubular column, said spacer means including, for each helix, a plurality of spacer bars equiangularly distributed around the helix and each aligned with a spacer bar ofthe next adjacent helix so that rows of spacer bars extend radially of the concentric helices, each spacer bar being formed of two sections which are fitted on either side ofa vertical row of the helical tubes and joined to form a spacer bar and tube assembly means for connecting the spacer bars at their upper ends to a corresponding one of said support members, each spacer bar in each row is separated from the next spacer bar in the row, the separation between each two spacer bars that are adjacent each other in a row is maintained by a set ofdistance pieces connected to one spacer bar and abutting a portion of the adjacent spacer bar and tube assembly and equidistantly separated from each other lengthwise of the spacer bars, and, for any spacer bar lying between two other spacer bars, the distance pieces of the set which is associated with that spacer bar and one of the other two spacer bars are staggered rclatively to the distance pieces of the set associated with that spacer bar and the other of the other two spacer bars.
2. A heat exchanger according to claim 1, in which two sets of distance pieces that are staggered relatively to each other are so disposed that distance pieces of one set lic midway between adjacent distance pieces of the other set.
3. A heat exchanger according to claim 1, in which each distance piece is fixed to one of the two spacer bars with which it is associated and abuts the other.
4. A heat exchanger according to claim 1, in which each distance piece is fixed to one of the two spacer bars with which it is associated and abuts a tube helix with which the other spacer bar is associated.
S. A heat exchanger according to claim 3 in which the fixing of each distance piece to the spacer bar to which it is fixed is effected by welding.
6. A heat exchanger according to claim 4 wherein each distance piece comprises a pair of rectangularly shaped plates and the spacer bars associated with the distance piece are interposcd between said pair of plates.
7. A heat exchanger according to claim 1 wherein each of the spacer bars comprises two stri s clamped ed e-to-edge, said strips having their abutting e ges formed wit h substantially cquiarcuate cooperating recesses lying in pairs and forming apertures for the passage of the tube helix therethrough.