WO1989001599A1

WO1989001599A1 - Jet impact heat exchanger

Info

Publication number: WO1989001599A1
Application number: PCT/FR1988/000408
Authority: WO
Inventors: Serge Galant; Michel Cellier; Christian Morillon; Jean-Charles Mulet; Louis Minjolle; Gines Martinez
Original assignee: Bertin & Cie
Priority date: 1987-08-07
Filing date: 1988-08-05
Publication date: 1989-02-23
Also published as: FR2619205B1; FR2619205A1

Abstract

Jet impact gas-gas heat exchanger, comprising alternating circulating layers of a hot gas and a cold gas, composed of parallel separation plates (14) between which rows of unitary blocks (16) are placed freely side by side serving to direct the gas flows and generate the jets which impinge on the walls of the separation plates (14).

Description

i

JET IMPACT HEAT EXCHANGER

The invention relates to a jet impact heat exchanger, comprising parallel alternating layers of circulation of a stream of hot gas and a stream of cold gas, respectively. •

There are already exchangers of this type, whose components are made of ceramic to withstand temperatures of the order of 1400 - 5- 1500 ° C, but which, due to the very use of ceramics, are of structural and relatively complex assembly. In particular, it is known from French patent No. 2,526,930 of the applicant, a ceramic gas-gas exchanger, with jet impact, in which the layers or circulation passages of hot gas and cold gas are delimited by series of

T0 parallel plates placed obliquely and mounted by interlocking their edges in grooves of two lateral ceramic flanges. The relatively large number of these plates complicates the assembly of the exchanger. In addition, the arrangement does not allow an exchanger comprising easily a number of alternating layers of gas circulation

15 hot and cold gas circulation, respectively, which is greater than two.

The object of the invention is in particular to overcome the drawbacks of this prior art and to propose a gas-gas heat exchanger of the jet impact type, which is extremely simple to assemble and whose 0 ceramic components can be standardized and mass produced.

The invention provides for this purpose a jet impact heat exchanger, comprising parallel alternating layers for the circulation of a stream of hot gas and a stream of cold gas, which are delimited by walls 5 -. separation parallels forming an exchange surface and one side of which is in contact with the hot gas and the other side in contact with the cold gas, and elements mounted in each sheet to divert the current of gas which circulates therein and form gas jets striking a partition wall, characterized in that these elements are freely 0 unit blocks juxtaposed in each sheet between two partition walls, each of these blocks comprising support and positioning means cooperating with the partition walls and to capture the gas flow coming from a previous block, means for forming two series of gas jets oriented in opposite directions and striking the partition walls, and means ensuring the continuity of the flow of gas to the next block as well as positioning by report to this block.

Thus, according to the invention, the exchanger can be formed very simply by free juxtaposition of unit blocks between parallel walls of separa¬ tion which delimit the layers of hot gas circulation and the layers of cold gas circulation. These unit blocks are all identical to each other, and their manufacture can be standardized.

The juxtaposition of these blocks in two perpendicular directions, one of which is parallel to the general direction of the flow of gas in the sheet considered, allows at will to increase the size of the exchanger.

According to one embodiment of the invention, each unit block has substantially the shape of a rectilinear trough with U-shaped section, the side walls of which are substantially parallel to the partition walls, the open face of which faces the preceding block by compared to the gas flow, and whose closed face or transverse wall is oriented towards the next block with respect to the gas flow.

The side walls of this block include slots or orifices for the passage of gas, which form the above-mentioned jets striking the partition walls.

The side walls of the block are advantageously bordered, on the side of the open and closed faces of the block, by external flanges forming the aforementioned support and positioning means.

To ensure the continuity of the gas flow to the next block, the flanges located on the side of the closed face of the block are perforated or cut.

The blocks are advantageously sections of profile made of thermally refractory material, in particular ceramic. They can be formed by extrusion or by raw molding, then by baking and machining.

These manufacturing methods are particularly well suited to mass production.

The invention will be better understood and other characteristics, details and advantages thereof will appear more clearly on reading the description which follows, given by way of example with reference to the appended drawings in which: - Figure 1 is a schematic perspective view of a module of a heat exchanger according to the invention, - Figure 2 is a simplified view of two layers of this module, illustrating the operation of the exchanger;

- Figure 3 is a partial schematic perspective view of an element of the exchanger;

- Figure 4 is a partial perspective view of a section of section intended to form an element of a heat exchanger according to the invention;

- Figure 5 shows the element obtained from this section of profile.

The module of FIG. 1 comprises two plies 10 for the circulation of a hot gas in parallel, and three plies 12 for the circulation of a cold gas, the plies 10 and 12 being parallel and alternating so that each ply

10 for circulation of hot gas is located between two plies 12 for circulation of cold gas.

In the example of Figure 1, the general circulation of hot gas and cold gas are crossed. They could be parallel and oriented in the same direction, or in the opposite direction against the current.

Each sheet 10, 12 is delimited by two parallel flat plates 1, made of ceramic, between which are placed unitary blocks for guiding the gas flow, which are juxtaposed freely in two perpendicular directions, one of which is parallel to the direction general of the gas flow in the sheet considered, as indicated by the arrows in Figure 1, and the other of which is perpendicular to the first in the plane of the sheet.

The heat exchanger also comprises inlet and outlet manifolds for hot gas and cold gas, as well as side plates making it possible to support the plates 14 delimiting the layers. Preferably, the plates 14 are supported by embedding their edges in grooves of the side plates. These may have a cellular structure, which facilitates the embedding of the edges of the plates 14.

The entire heat exchanger is surrounded by thermal insulation elements and contained in a metal structure equipped with means for compensating for differential expansions.

The unitary ceramic blocks which are juxtaposed between the plates 14 have substantially the structure shown schematically in the figures

2 and 3. Each unit block 16 comprises two side walls 18, mutually parallel and connected at one end by a transverse wall 20 to give the block 16 substantially the shape of a trough with cross section in U. Two outwardly oriented flanges 22 are formed on the edges of the plates 18 which are parallel and opposite to the edges connected by the transverse wall 20. The latter comprises, from place to place, tabs 24 ^" oriented towards the Slots 26 or any gas passage openings are formed in the side walls 18.

The unit blocks 16 are juxtaposed in rows and columns between the plates 14, so that the edges 22 of a block 16 are applied on the legs 24 of the previous block, and that the legs 24 of the same block 16 s' apply to the edges 22 of the next block with respect to the general direction of gas flow. The gas which circulates in a sheet 10 or 12 between two plates 14 is guided as follows: when it arrives on a block 16, it is deflected by the flanges 22 between the side walls 18 and leaves the block 16 through the slots or orifices 26 of these side walls, forming gas jets which strike the two partition walls 14. The gas then flows, between each side wall 18 and the corresponding partition wall 14, in the direction of the next block where it is again deflected by the outer edges 22 to come between the side walls 18 of this next block.

A wall 14 between two layers 10 and 12 is therefore regularly struck on one of its faces by jets of hot gas and, on the other of its faces, by jets of cold gas and therefore constitutes a heat exchange surface by convection between hot gas and cold gas, with good efficiency thanks to the impact of the gas jets on the two faces of the wall 14. In addition, the side walls 18 of the blocks 16 form screens making it possible to absorb ber the thermal radiation of the partition walls 14 which are brought to a relatively high temperature. This reduces the heating of the outer walls of the heat exchanger, and therefore the heat losses to the surrounding environment.

The separation plates 14 and the blocks 16 are preferably made of - silicon carbide, but can be made of other ceramic materials, such as silicon nitride and sialon, having a sufficient thermal conductivity (greater than 15 W /°.m).

As can be seen in FIG. 2, the separation plates 14 forming an exchange surface are in fact formed by several plates connected to one another by assembly bars 28 with an I-shaped cross-section allowing both to be juxtaposed edge to edge two 14 consecutive plates.

We will now refer to Figures 4 and 5, which represent schematically a practical embodiment of the unit blocks 16.

FIG. 4 shows a section of ceramic profile 30, which can be produced by extrusion or raw spinning of ceramic, then by firing. The profile 30 of FIG. 4 comprises a rectangular channel 32 associated on its two short sides with two channels 34 of trapezoidal section, the small base of which corresponds to the short side of the rectangular channel 32.

The profile section 30 of Figure 4 is then machined to take the shape shown in Figure 5 and constitute a ^' unit block 16. This machining consists of cutting one of the side channels 34 to keep only legs 36 at regular intervals , while rectangular cutouts 38 and 40 are formed in the large base and the small base of the other lateral channel 34 and open out inside the rectangular channel 32. Finally, parallel slits 42 are formed in the large walls of the rectangular channel 32. A unitary block is thus obtained, the structure of which corresponds to that of block 16 in FIGS. 2 and 3, the openings 38 and 40 forming the gas inlet passages inside the unitary block, the slots 42 corresponding to the slots or passages 26 for exiting the gas jets towards the separation plates 14, the legs 36 corresponding to the legs 24 for support and positioning. The unit blocks could also be produced in another way, for example by raw molding, then cooking and machining and / or assembly. The shapes of these unit blocks could be different from those shown in the figures, provided that they allow the following functions to be fulfilled: - supplying the unit block by the flow of gas leaving the previous unit block,

- ensure the continuity of the flow of gas leaving this block towards the next block,

- Ensure the support and positioning of the unit block between the two walls 14 of separation.

For example, a block could be constituted by a central box associated with two end elements.

A heat exchange module according to the invention such as that shown diagrammatically in FIG. 1, can have a heat recovery capacity of the order of 30 to 60 kW, for the following dimensions:

- height of all the layers 10 and 12: 200 mm,

- dimensions in the plane of a sheet: 660 mm X 220 mm.

Claims

1) Jet impact heat exchanger, comprising parallel alternating layers (10, 12) for the circulation of a stream of hot gas and a stream of cold gas, which are delimited by parallel walls (14) of separation forming an exchange surface, one side of which is in contact with the hot gas and the other side of which is in contact with the cold gas, and elements mounted in each sheet to divert the current of gas which circulates therein and form gas striking a partition wall (14), characterized in that these elements are unit blocks (16) freely juxtaposed in each sheet between two partition walls (14), each of these blocks comprising support means (22) and positioning cooperating with the two partition walls (14) and making it possible to capture the gas current coming from a previous block, means (26) for forming two series of gas jets oriented in opposite directions and striking the walls of parted tion (14) and means ries (24) ensuring the continuity of the flow of gas to the next bioc as well as positioning relative to this block.

2) Exchanger according to claim 1, characterized in that the unit blocks (16) are, in each sheet (10, 12), juxtaposed in two directions, one of which is parallel to the general direction of gas flow in the tablecloth and the other of which is perpendicular to the first in the plane of this tablecloth.

3) Exchanger according to claim i or 2, characterized in that each unit block (16) has substantially the shape of a rectilinear trough with U section, the side walls (18) of which are substantially parallel to the partition walls, of which the open face is turned towards the previous block with respect to the gas flow, and whose closed face or transverse wall (20) is oriented towards the next block with respect to the gas flow.

4) Exchanger according to claim 3, characterized in that the side walls (18) of the block (16) comprise slots or orifices (26) for the passage of gas, forming the aforesaid jets. 5) Exchanger according to claim 3 or 4, characterized in that the side walls (18) of the block are bordered, on the side of the open and closed faces of the bioc, by external flanges (22, 24) forming the aforementioned support means and positioning. 6) Exchanger according to claim 5, characterized in that the flanges (24) located on the side of the closed face (20) are perforated or cut to ensure continuity of the gas flow to the next block.

7) Exchanger according to one of the preceding claims, characterized in that the unit blocks (16) are profile sections (30) of thermally refractory material such as a ceramic.

8) Exchanger according to one of the preceding claims, characterized in that the blocks (16) are formed by extrusion or by raw molding, then by baking and machining. 9) Exchanger according to one of the preceding claims, characterized in that the partition walls (14) are parallel flat plates joined together in the same plane by assembly bars (28), and mounted by embedding their edges in side plates.