US2505695A

US2505695A - Tube nest for heat exchangers

Info

Publication number: US2505695A
Application number: US690572A
Authority: US
Inventors: Villiger Eugen; Peter Rudolf
Original assignee: Aktiengesellschaft fuer Technische Studien
Current assignee: Aktiengesellschaft fuer Technische Studien
Priority date: 1945-09-22
Filing date: 1946-08-14
Publication date: 1950-04-25
Anticipated expiration: 1967-04-25

Description

April 25, 1950- E. VILLIGER ETAL TUBE NEST FOR HEAT EXCHANGERS 2 Sheets-Sheet 1 Filed Aug. 14, 1946 wua am? I f n 1 Q n m b c Aiiorn cgs April 259 19 50 E. VILLIGER ETAL 2,505,695

TUBE NEST FOR HEAT EXCHANGERS Filed Aug. 14, 1946 2 Sheets-Sheet 2 Invenkors 'fiugznvilliger and Rudolf Pdzr Fig.5 1 V 5 B9 QdfiQ/DZ? Adornegs Patented Apr. 25, i950 TUBE NEST ron nan ExcnANGnns Eugen Villiger and Rudolf Peter, Zurich, Switzerland,

'assignors to Aktiengesellschaft Fuer Teelmische Studicn, Zurich, Switzerland, a corporation of Switzerland Application August 14, 1946, Serial No. 690,572 In Switzerland September 22, 1945 1 This invention relates to a tube nest for heat exchangers such for example as evaporators,

steam generators, preheaters, regenerators, gas' heaters and the like with tubes which are long in proportion to their diameter. Tube nests of this kind are used in heat exchangers for heating or cooling liquid and gaseous media.

In Order to obtain the exchange of heat aimed at in heat exchangers with long, thin tubes, it is necessary that the distances between the tubes should be maintained under all working conditions, and that any tendency of the tubes to swing or whip should be prevented. On the other hand damaged tubes must be capable of being removed singly and replaced by new ones.

In order to satisfy these various requirements, the relative positions of the tubes to each other is ensured in a tube nest according to the present invention by spacer members, preferably of ring shape, which are connected to form at least one latticework and by which the tubes are held movably and in a manner which will enable single tubes of the nest to be exchanged. The latticework can in its turn be rigidly connected to the inside of the shell of the heat exchanger. In a tube nest of this kind therefore the spacer members are not rigidly connected to the tubes, so

7 Claims. (Cl. 257-224) 2 11-11 of Fig. 1 through a changer.

Fig. 3 is a longitudinal section on the line III-III of Fig. 4 through a part of a contraflow heat exchanger, in which spacer rings of one group of a latticework are slit and pushed on to unslit spacer rings of a second group of this latticework. The tubes are not shown in section for the sake of clearness.

Fig. 4 is a partial section to a larger scale on portion of the heat exthe line IV--IV of Fig. 3.

that welded and other connections between these parts are not necessary. Consequently, in connection with the securing of the tubes of the nest in their relative positions to each other, injury to the thin tubes by burning out, damage and the like can be prevented. Since all rigid connection between the tubes and the spacer members is avoided, each single tube of the nest can be also removed and replaced by a new one. As a latticework built up of a number of spacer rings has no radial struts, the resistance to the flow of the medium offered by a latticework of this kind is comparatively small, and at the same time the risk of small pieces of metal being broken off and carried along by one of the heat exchanging media is obviated to a very great extent. As no tightly adhering holders have to be pushed along over the long tubes and no delicate welding operations have to be carried out, tube nests according to the present invention are also cheap to manufacture.

constructional forms of the subject matter of the invention are illustrated by way of example in the accompanying drawing in which:

Fig. l is a longitudinal section on the line 1-1 of Fig. 2 through a contrailow heat exchanger, and i Fig. 2 is a section on a larger scale on the line Fi 5 is a longitudinal section onthe line V---V oi 1kg. 6 through a portion of a heat exchanger, in which the spacer rings which serve to' maintain the relative positions of adjacent tubes are staggered relatively to each other longitudinaly of the tubes, which latter are not shown in section for the sake of clearness.

Fig. 6 is a partial section to a larger scale on the line VI-VI of Fig. 5.

Fig. 7 shows a modification of details.

Fig. 8 shows the cross-section of a differently 1shaped spacer member and of tubes spaced by hem.

Before proceeding with a detailed description of embodiments of the invention, certain geomet rical considerations should be made clear.

There are two possible uniform spacings of tubes in a tube sheet. In one the tube ends form a square pattern, i. e. the centers of the tubes lie in two sets of uniformly spaced parallel lines at 90 to one another (see Figs. 2, 4, 6 and 8). In the other arrangement the tube endsare inan equilateral triangle pattern, and the centers of the tubes lie on three sets of uniformly spaced parallel lines at to each other (see Figs. 4, 6 and 8). The invention is applicable to either tube arrangement but there are minor differences of detail.

For either tube pattern, the spacing grid structure comprises two sets of short, thin-walled tube sections hereinafter called spacer rings, each of which encircles a tube and at its periphery engages a plurality of tubes adjacent the surrounded tube. The two sets of spacer rings may be connected together, and at least one connected to the shell of the exchanger, or both sets may be connected with the shell. In the latter case the two sets may be interconnected or not as may be preferred.

With the first (square) pattern alternate tubes in a row are surrounded by spacer rings of one set, and the remaining tubes by spacer rings of the other set (see Fig. 2). With the second (equilateral triangle) pattern, the tubes counted in greases any of the three row directions have the following recurrent sequence as to the spacer rings; a tube surrounded by'a ring of the first set, a tube surrounded by a ring of the second set. a-tube not surrounded by any ring (see Fig. 4).

with the square pattern each spacer ring (except those around marginal tubes) engages four tubes at uniform intervals of 90 of are on the ring periphery, whereas with the triangularpattern each spacer ring (except those around marginal tubes) engages six tubes and the are interval is 60.

The spacing action in the same and all tubes are rigidly spaced. Preferably the two sets of spacer rings are oiIset in the direction of tube length, minimizing obstruction to flow outside the tubes in the direction of their length. In any case no part of the spacer structure is welded to the tubes. If the two sets of spacer rings are to be connected to one another, various 'expedients may be adopted, but welding is preferred.

In Figs. 1 and 2 the reference I denotes tubes of a tube nest which are long in proportion to their diameter, that is to say in which the ratio of length to external diameter is greater than 100:1. These tubes I are traversed by a medium which enters the heat exchanger through a connection 2 and leaves it by a connnection 3. A second medium which flows around the tubes I enters the heat exchanger through a connection 4 and leaves it again by a connection 5. In order to ensure the relative positions of the comparatively long tubes I to each other, two latticeworks A and B, which are built up out of spacer rings, are provided. Each of the latticeworks A and B has two groups 6, I of spacer rings, those of group 6 being staggered relatively to those of group I longitudinally of the tubes l in such a way that group 6 is'located above group I of the particular groups A and B respectively. As shown in Fig. 2 each horizontal and vertical row of tubes of the nest contains alternately a spacer ring of group 6 and one of group I concentric with a tube I, a larger free annular space 'being left between the particular spacer ring and the particular tube I of the nest. In this arrangement each tube I passes through an opening bounded by four spacer rings of the adjacent group and ,by doing so is held at four points a, b, c, d by these spacer rings in the required position relatively to the adjacent tubes. In this way the prescribed distance between the different tubes I of a nest can be ensured without its being necessary to connect the spacer rings of the latticeworks A, B to the tubes I rigidly in any way. On the contrary the the two cases is basically latter are held movably by the spacer rings of Y the groups 6 and 1 respectively and in amanner which enables single tubes to be interchanged at any time. The spacer rings of each group 6 and I respectively of the latticeworks A, B are on the other hand rigidly connected to each other, e. g. by welding, and the spacer rings of group I are welded at 6 to a plate 6 which in turn is welded at G to the shell 8 of the heat exchanger. If necessary the spacer rings of the two groups 6, 1 of latticework A and B respectively may be rigidly connected with each other also, asby welding for example. Such weldin points are denoted in Fig. 2 by the reference 1 Theconstructional form shown in Figs. 3 and 4 diflers from that shown in Figs. 1 and 2 in two respects. The tube pattern is triangular, and the spacer rings 9 of the upper group of a latticework C are provided in their lower half with six notches (of which only one can be seen in-l'ig. 9) rimning parallel with the axis of the nest tubes I I, so that they can interengage with spacer rings III of the lower group of this latticework C. In this case therefore the necessary rigid connection between the spacer rings 9, II of the latticework is obtained by pushing the rings of one group on to the rings of the other group. The spacer rings thus need not also be welded to each other. In this type of construction, those tubes which are not encircled by a spacer ring engage the spacer rings 9 of the upper group at three points e. 1, e and the spacer rings III of the lower group of the latticework C at three points h, I, it. Each tube which is encircled by a spacer ring Is engaged by three other spacer rings of one of the two groups, so that in this case also any divergence of any one of the tubes II from its prescribed position is rendered practically impos-. sible. In order to secure the latticework C to the shell I2 of the heat exchanger two annular plates I3, I4 arranged in different planes and welded to the shell I2 are employed; each of them has extensions IE, IS and I6 respectively of different lengths (the shorter extensions of the lower plate I are not shown in Figs. 3 and 4) The shorter extensions of the two plates I3, I4 are welded to the radially outermost spacer rings 9 and III respectively of the nest, whereby a rigid connection of the latticework C to the shell I2 of the heat exchanger is established.

In Figs. 5 and 6 the reference I9 denotes the spacer rings of a latticework D, which are superimposed on each other like a flight of stairs without being rigidly connected to each other. In this arrangement the spacer rings are supported on those rings I8 which are situated on the periphery of the tube nest and are connected rigidly by sheet metal strips 29 (see Fig. 5) to the shell I9 of the heat exchanger. A part of thetubes of the nest, that is to say the tubes I! (see Fig. 6) are each arranged co-axially to one of the spacer rings l8, each of these tubes I1 being held in the necessary position by three of the spacer rings I8, at three points I, m, n situated at different heights. The rest of the tubes of the nest, that is to say the tubes II, are held in the prescribed position by the outer walls of the spacer rings I9, which surround them and touch them at six points 0, 9, q, r, s, t situated at different heights.

If, as shown in Fig. '1, longitudinal slots are.

provided in both the lower half of the ring 2| of an upper group and also in the upper half of the rings 22 of a lower group of spacer rings of a latticework, the spacer rings 2I and 22 of the two groups can be pushed into each other in such a way that the upper and lower ends of the spacer rings of the two groups are each caused to lie in a plane, that is to say the height of the latticework thus formed then corresponds to the height of each single spacer ring.

The spacer members need not necessarily be of ring shape as shown; they may also be constructed as bodies of polygonal cross section. Thus, Fig. 8 shows spacer member 24 of hexagonal shape. Obviously, since the circular spacer rings suggested in Figs. 1-7 engage four, three or six tubes, as has already been explained, the

contour of the rings between the points of such engagement is not controlling and can be varied considerably without any change of function. Thus the term "ring" as used in the claims should not be so literally interpreted as to exclude all but circular rings.

What is claimed is:

i. A heat exchanger comprising a shell; a nest of long slender parallel tubes enclosed by said shell, said tubes being uniformly spaced and arranged in a pattern in. which the tube axes lie in intersecting Sets of parallel uniformly spaced planes; and at least one grid assembly serving to sustain the tubes laterally in a zone intermediate their ends, said assembly comprising at least two sets of spacer rings, these sets being offset from one another in the direction of the length of the tubes, each ring freely encircling a tube, and the tube so encircled being spaced from the encircling ring and from other tubes by a plurality of rings offset from said encircling ring and in peripheral contact with said encircled tube and other tubes at a plurality of circumferentially spaced points on the tubes and on the rings.

2. The combination defined in claim 1 in which the rings of the different sets are interconnected.

3. The combination defined in claim 1 in which the rings of the different sets are interconnected and at least one set is connected with said shell.

t. The combination defined in claim 1 in which said sets of parallel uniformly spaced planes are at 90 to each other, there are two sets of rings in the grid assembly, the rings of each set engage peripherally only tubes which are encircled by rings of the other set, and the rings of the two sets are interconnected and connected with said shell.

5. The combination defined in claim 1, in which the tube axes lie at the intersections of three sets of uniformly spaced parallel planes disposed at 60, each to the others, there are two sets of rings in the grid assembly, approximately one third of the tubes are not ring encircled and are distributed in equilateral spacing throughout the nest, and the rings of each set of tube-encircling rings engage tubes encircled by rings of the other set and also un-encircled tubes, whereby all tubes are engaged by rings.

6. The combination defined in claim 1, in which the tube axes lie at the intersections of three sets of uniformly spaced parallel planes disposed at each to the others, there are two sets of rings in the grid assembly, approximately one third of the tubes are not ring encircled and are distributed in equilateral spacing throughout the nest, the rings of each set of tube-encircling rings engage tubes encircled by rings of the other set and also un-encircled tubes, whereby all tubes are engaged by rings, and the rings of the two sets are interconnected and connected with said shell.

7. The combination defined in claim 1 in which the tube nest is approximately circular in transverse section, rings encircling the tubes of the outermost annular series of tubes in the nest are connected with said shell, rings encircling the next inner annular series of tubes are oflset in the direction of tube length and engage the first named rings, and so on in annular stepped arrangement to the center of the nest.

EUGEN VILLIGER. RUDOLF PETER.

REFERENCES EMBED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,967,961 Metten July 24, 1934 2,018,037 Sieder Oct. 22, 1935 FOREIGN PATENTS Number Country Date 480,574 Great Britain Feb. 24, 1938 553,485 Great Britain May 24, 1943