GB2062208A - Plate heat exchanger - Google Patents

Abstract

In a heat exchanger in which uprights 4a are formed at the corners of a plate stack by corner portions of the plates 1 alternating with block- shaped ends 5 of spacer bars 4 between the plates, the surface of said uprights so formed, is machined (e.g. to render it flat) and processed (e.g. drilled and tapped at 12, 13) to receive fixing members (e.g. screws) for the positioning and securing to the heat exchanger of associated members 14 (such as header boxes) against the uprights. <IMAGE>

Description

SPECIFICATION Heat exchanger with plates and small bars The present invention relates to a novel heat exchanger made of plates and small bars, viz a heat exchanger in which the plates are placed in parallel together and kept in spaced relationship by sets of small bars alternatively placed at 900 for delimiting successive channels crossing each other.

The construction of heat exchanger cores with plates and small bars of the type just mentioned is well known in the art. The cores of this type cannot be used bare and must comprise connection means for connecting them to the fluid circuits, for example header boxes, when the fluid is liquid, or connection flanges enabling fixation to pipes or similar when the fluid is a gas.

It is usual in the art to weld the header boxes and the flanges on the core by arc-welding techniques. However, it has been found that such arc-welding could cause damage to the brazing seams of the core.

Applicant in French Patent Application 79,00436 has proposed to braze uprights at the four angles of the core and to connect thereafter cross-pieces at the ends of the brazed uprights in order to form a connection flange. In this case in fact, the cross-pieces may be arc-welded in positions which are remote from the brazing seams, so that the latter are not damaged.

However, such an arrangement still presents some disadvantages. It has actually been found that brazing of the uprights is difficult to carry out in a perfect manner since the brazing alloy flows downwardly along the uprights, and it is frequent also that porosities exist in some brazing seams between the plates and the small bars. Such porosities cannot be clogged when they are under the uprights since they are then out of access.

Applicant knows various publications concerning the same object in the prior art. In this respect: US patent 3,247,899 discloses a heat exchanger with plates and small bars wherein the plates are interposed between studs affixed to the ends of the small bars.

British patent 838,466 dsicloses small bars the ends of which make an angle with their logitudinal direction, thereby defining studs in which is formed a vertical slot. The plates have the same configuration, enabling thereby to stack the plates with studs protruding relative to the longitudinal edge of the small bars and plates. It is possible, in this embodiment, to engage a thin upright inside the vertical slot delimited by the stacking of plates and small bars, and this upright may be connected to support parts for distribution boxes.

German patent 1,075,135 discloses a similar embodiment wherein the end of the small bars is formed with a slanting portion delimiting a stud, and the plates inserted between the bars form a corresponding protrusion.

Uprights are thus delimited at the four angles of the heat exchanger core, and the two protruding angles of the uprights enable a fixation by welding of the distribution boxes.

US patent 2,961,222 discloses an arrangement in which notches are provided in protruding portions formed by the plates and small bars, these notches being adapted for positioning added uprights on which it is then possible to weld various parts and particularly distribution boxes.

US patent 2,368,814 also discloses a stacked arrangement in which the plates and small bars of the heat exchanger core delimit protruding uprights at the ends of which is fixed a crossshaped jacket in which is inserted the core.

In the known arrangements, welding steps have always to be carried out and it is difficult, and even impossible, to use a same core with distribution boxes of different shapes and sizes.

It is an object of the invention to provide a simple way for forming standard cores which can be used in various applications and on which it is possible to affix accessories, particularly distribution boxes of most different shapes and dispositions.

According to the invention, the heat exchanger with plates and small bars having connection flanges with distribution boxes formed by four uprights and cross-pieces connecting said uprights together and the uprights being formed by an alternate stacking of small bars with corners of the plates being inserted between said small bars, said small bars having ends with studs which are connected by a thinned blade-shaped portion, the- plates fixed to the small bars being formed with notches extending in the side thereof up to vicinity of the uprights, is characterized in that the stacking formed by the ends of the small bars and the portions of the plates inserted between the small bars is machined so as to form bearing surfaces in which are carried out machining operations, particularly tappings, for positioning fixation members applied against the uprights.

Various other features of the invention will become more apparent from the following detailed description.

Embodiments of the invention are shown, by way of non limitative examples, in the accompanying drawings wherein: Fig. 1 is a diagrammatic perspective view, partly cut away, of a heat exchanger core made of plates and constructed according to a first embodiment of the invention; Figs. 2-4 are perspective views of various embodiments of the small bars used in the heat exchanger core of Fig. 1; Fig. 5 is an exploded perspective view showing particular features of the invention; Fig. 6 is a cross-sectional view of the heat exchanger of the invention made with a looped circuit; Fig. 7 shows another embodiment; Fig. 8 is a plan view illustrating a particular feature of the invention.

The heat exchanger core shown in Fig. 1 is made in a known manner by a stacking of plates and small bars. In the embodiment shown in Fig.

1, the plates 1, it... are shaped as rectangles, the sides of which are formed with notches, such as shown at 2, in order to define at the four angles of the rectangle protruding portions 3 forming rectangular shaped corners. In practice, the plates 1, 1 a . . . are easily made by cutting out the notches 2 in the side edges of a rectangular plate, thereby necessarily defining the protruding portions 3.

The small bars 4 which laterally delimit the channels are provided for forming the uprights 4a of the heat exchanger. The small bars may be made in various ways.

In Fig. 2, the small bars comprise two metallic studs 5, of rectangular cross-section, in which are provided slots 6 adapted for introduction of the ends of a blade 7 which is fixed to the studs by brazing, the operations being carried out at the same time as the small bars are brazed to the plates 1, 1a....

In Fig. 3 the studs 5 are connected by a blade 7a which is welded as shown at 8.

Finally, in Fig. 4, the studs 5 and blade 7b are integral, the bar assembly being for example manufactured by forging or cutting.

As is clearly apparent, the height of the blade 7, 7a or 7b is the same as that of the studs 5.

For forming a heat exchanger core, there are stacked in succession two longitudinal small bars, a first plate, two transverse small bars, a second plate, two longitudinal small bars, a third plate, and so forth. If required, it is also possible to place secondary heat exchange member 9 and 10, respectively, in one and the other of the two sets of channels formed by the plates.

The protruding portions 3 of the plates 1, 1 a . . .

are thus sandwiched between the studs 5 of the small bars, the blades 7 of which are slightly set back relative to the edge 1, of the plates in the area of the notches 2 (Fig. 6). On the contrary, it is advantageous that the outer edge of the protruding portions 3 of the plates is in alignment, in the most efficient way, with the outer edge of the studs 5.

The core assembly made by stacking is subjected to a brazing operation, the operative sequence of which depends on the nature of the metals or alloys used for forming the core.

As shown in Fig. 5, for completing the core, solid longitudinal bars 41 are placed on each of the two sides of the core and transverse solid small bars 42 on each of the two other sides of the core so that these solid small bars, i.e. having the shape of rectangular parallelepipeds, form with the uprights 4a a peripheral flange.

It is next necessary to machine the faces formed by the uprights and the small bars 4, and 42- In the present enbodiment, this may be carried out by grinding, since the inlet and outlet faces of the core are set back relative to the planes to be machined which form thereafter the connection flange of the heat exchanger with the fluid circuits.

Fig. 7 shows a second embodiment of the invention wherein the plates 1 ..... . . . are of rectangular shape, and the portions of the plates which have to be integrated to the uprights are simply separated from the rest by small notches 2a. Thus, the almost totality of the volume formed by the uprights can be occupied by the core of a more compact apparatus. It remains possible to machine the end small bars and uprights with a view to provide a good flatness of the connection flanges by milling them without forming burrs by virture of the notches 2a which separate the inlet or outlet faces of the core from the uprights.

Fig. 8 is a partial view of a small bar, the blade 7a of which is conformed so as to extend up to the edge of the plates 1 ',1 'a ....

A subsequent step consists in drilling in the uprights holes 12, 1 3 possibly tapped, or to carry out other machining operations for the fixation of accessories, for example collecting boxes shown diagrammatically at 14, 1 5 (Fig. 5) in the shape of connection flanges of the heat exchanger to the circulation pipes of a gas. The holes 12, 13 may be drilled without drawback at the same time into the mass of the studs 5 and into the plates which are sandwiched between the studs to which they are brazed.

The connection flanges 14, 15 or boxes and other accessories which have to be fixed to the uprights and to the solid small bars 41 and 42 may be assembled by means of screws.

The sandwich arrangement of the plates and small bracing cross-bars is such that the brazing step is always carried out between stacked elements so that there is no risk of the brazing alloy having a tendency to flow down the core at the moment of the melting. On the other hand, this sandwich arrangement makes possible to bring the brazing alloy in the shape of a preliminary plating of some of the parts, and particularly of the plates, and this whatever the metals or alloys chosen.

Fig. 6 shows that the embodiment described makes possible the manufacturing of heat exchangers where the circulation is looped in at least one of the two circuits that they have.

Intermediate studs 5a can actually be provided, these intermediate studs 5a being connected by a blade 7d dividing each channel into two portions.

In this case, one of the boxes 141 is made such as to comprise inlet and outlet ducts 1 6, 17, whereas the other box 142 forms only a cover.

The heat exchanger can easily be repaired or modified.

A sealing agent may be placed inside the tapped holes drilled in the uprights, if the brazing seams prove to be porous.

But the most important is that it is possible to have an access to any point at the periphery of the brazings, thereby making possible the repair of eventual leaks by soldering or brazing.

The invention is not restricted to the embodiments shown and described from its scope as shown in the appended claims.

Claims (6)

1. A heat exchanger with plates and small bars having connection flanges with distribution boxes are formed by four uprights and cross-pieces connecting said uprights together and the uprights being formed by an alternate stacking of small bars with corners of the plates being inserted between said small bars, said small bars having ends with studs which are connected by a thinned blade-shaped portion, the plates fixed to the small bars being formed with notches extending in the side thereof up to vicinity of the uprights, the improvement wherein the stacking formed by the end of the small bars and the portions of the plates inserted between the small bars is machined so as to form bearing surfaces in which are carried out machining operations, particularly tappings, for positioning fixation members applied against the uprights.

2. A heat exchanger according to claim 1, wherein the upper portions of the uprights are connected by cross-pieces in the shape of small bars with no thinned out portion.

3. A heat exchanger according to claim 1, wherein the small bars comprise, on one side of the heat exchanger, intermediate studs for forming a looped circulation core.

4. A heat exchanger according to claim 1, wherein the core has inlet and outlet faces which are substantially in planes formed by outer faces of the uprights.

5. A heat exchanger according to claim 1, wherein the plates are rectangular in shape and the uprights are delimited by notches.

6. A heat exchanger, substantially as hereinbefore described, with reference to any one of the embodiments shown in the accompanying drawings.