US20070169924A1

US20070169924A1 - Heat exchanger installation

Info

Publication number: US20070169924A1
Application number: US11/623,878
Authority: US
Inventors: Pierre-Xavier Bussonnet
Original assignee: Alfa Laval Packinox SAS
Current assignee: Alfa Laval Packinox SAS
Priority date: 2006-01-20
Filing date: 2007-01-17
Publication date: 2007-07-26
Also published as: EP1811256A1; CN100504274C; CN101004328A; JP2007192535A; EP1811256B1; FR2896576A1; DE602006001840D1; FR2896576B1

Abstract

The invention relates to an installation for exchanging heat between fluids, the installation being of the type comprising a leaktight enclosure, means for exchanging heat between the fluids, and fluid admission and discharge means. The heat exchanger means comprise bundles of plates formed by stacks of horizontal plates and distributed in a star configuration around a tubular central collector concentric with the enclosure. Each bundle of plates has a front vertical wall secured to the collector and a rear vertical wall that is free, and each is slidably supported on a support member secured to the enclosure.

Description

The present invention relates to an installation for exchanging heat between fluids for cooling a first fluid by exchanging heat with a second fluid.

BACKGROUND OF THE INVENTION

Heat exchanger installations are known that comprise a leaktight enclosure having placed therein a bundle of plates that are disposed parallel to one another.
The plates, which are constituted by fine sheet metal, usually stainless steel, have edges with smooth surfaces, and central portions with corrugations, whereby they come into contact with one another and define channels that form independent fluid flow circuits.
That type of heat exchanger having bundles of plates operates with a variety of fluids, such as, for example, liquids or gases or two-phase mixtures.
With a plate heat exchanger of that type in which the two fluids flow in respective circuits, heat is exchanged between the two fluids, thereby enabling one of the fluids to be heated and the other fluid to be cooled, or vice versa.
In certain industrial applications, it is necessary to obtain a considerable temperature difference for the fluid to be cooled between its admission to and its discharge from the plate heat exchanger.
That is why, under such circumstances, a plurality of plate heat exchangers are placed one after another and each plate heat exchanger is constituted by a leaktight enclosure in which a bundle of plates is disposed defining two independent circuits. The circuits of the various bundles of plates are connected to one another by connection pipes passing through each of the enclosures in leaktight manner so as to provide continuous flow for the main fluid through the various bundles of plates.
As a result, the ground area occupied by that kind of installation is large, and the cost of fabrication and maintenance is likewise large.
In addition, the connection pipes between the various heat exchangers for transferring fluids between the heat exchangers constitute zones of wasted head losses, and zones of heat loss, thus reducing the efficiency of the heat exchanger installation.
To remedy those drawbacks, heat exchanger installations are known that comprise a leaktight enclosure having placed therein a plurality of bundles of plates, each connected to fluid admission and discharge means.
In general, the bundles of plates are connected rigidly to the leaktight enclosure, which raises problems when the temperature difference between the two fluids is large, for example of the order of several hundreds of degrees.
This temperature difference leads to large thermal stresses in the bundles of plates, which can give rise to deformation in the plates of the bundles of plates and to broken wells, thereby reducing the efficiency of the installation.

OBJECTS AND SUMMARY OF THE INVENTION

An object of the invention is to avoid those drawbacks by proposing a compact heat exchanger installation that enables heat to be exchanged between fluids presenting a large temperature difference.
The invention thus provides an installation for exchanging heat between fluids, the installation being of the type comprising a vertical leaktight enclosure of elongate shape, heat exchanger means between the fluids, and admission means and discharge means for a first fluid and for a second fluid, wherein the heat exchanger means comprise bundles of plates formed by stacks of horizontal plates defining between them two flow circuits for countercurrent flow of the two fluids and distributed in a star configuration around a tubular central collector concentric with the enclosure, and wherein each bundle of plates has a front vertical wall secured to the central collector and provided with inlets and outlets for each of the fluids, and a rear vertical wall that is free and provided with inlets and outlets for each of the fluids, each bundle of plates being slidably supported on a support member secured to the leaktight enclosure.
According to other characteristics of the invention:

- the fluid inlets and outlets provided in the front walls are formed, for each circuit, by an alternating superposition of open or closed ends, the open ends of the circuit inlets for the first fluid being situated in the middles of the front walls, and the open ends of the circuit outlets for the second fluid being situated in the side margins of the front walls;
- the open ends of the inlets for the first fluid open out into the central collector connected to the admission means for said first fluid;
- the open ends of the outlets for the second fluid in the side margins of the front walls of two adjacent bundles of plates are interconnected by an annular collector concentric about said central collector and including, in its bottom heat exchanger, a hemispherical cap connected to the means for discharging said second fluid;
- the inlets and outlets for the fluids provided in the rear walls are formed, for each circuit, by an alternating superposition of open or closed ends, the open ends of the circuit inlets for the second fluid being situated in the middles of the rear walls, and the open ends of the outlets for the second fluid being situated in the side margins of the rear walls;
- the fluid inlets and outlets formed in the rear walls are formed, for each circuit, by an alternating superposition of open or closed ends, the open ends of the circuit inlets for the second fluid being situated in the side margins of the rear walls, and the open ends of the outlets for the first fluid being situated in the middles of said walls;
- the open ends of the inlets for the second fluid open out into the annular space between the central collector and the enclosure, said annular space being connected to the admission means for said second fluid;
- the open ends of the outlets for the first fluid are covered by a collector connected by at least one pipe provided with at least one expansion compensator to a collector ring connected to the means for discharging the first fluid; and
- each bundle of plates on each of its side walls has a respective vertical deflector extending towards the adjacent bundle of plates, the free ends of two contiguous deflectors overlapping.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics and advantages of the invention appear from the following description given by way of example and made with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic longitudinal section view of a heat exchanger installation in accordance with the invention;

FIG. 2 is a diagrammatic cross-section view on line 2-2 of FIG. 1;

FIG. 3 is a diagrammatic longitudinal section view on line 3-3 of FIG. 2, showing fluid flow in the installation in accordance with the invention;

FIG. 4 is a diagrammatic perspective view showing the distribution of bundles of plates in the heat exchanger installation in accordance with the invention; and

FIGS. 5A and 5B are views of the walls, respectively in front of and behind a bundle of plates.

MORE DETAILED DESCRIPTION

The figures show an installation for implementing heat exchanger between a first fluid A referred to as a “hot” fluid, which on admission into the installation presents a temperature of about 800° C., and a second fluid B, referred to as a “cold” fluid, which presents on admission into the installation a temperature of about 200° C.
The heat exchanger installation is intended for example to cool the first fluid A by means of the second fluid B.
The heat exchanger installation shown in the figures comprises a leaktight enclosure 1 of elongate shape and of section that is circular, for example. This leaktight enclosure 1 is provided with support members (not shown) for resting on a surface for receiving said leaktight enclosure 1, and it is preferably disposed vertically.
The enclosure 1 has a cylindrical central portion 2 provided with a cover 3 and a bottom 4, e.g. of hemispherical shape.
The installation includes a tubular central collector 10 concentric with the enclosure 1 and cooperating with the enclosure 1 to define an annular space 5. The collector 10 has a central portion 11 of generally cylindrical shape provided with a cover 12 and a bottom 13 each in the form of a spherical cap.
Admission means for a first fluid A open out into the cover 12 of the collector 10, which admission means are constituted by at least one tube 14 passing through the cover 3 of the leaktight enclosure 1 and provided with at least one expansion compensator 15. The annular space 5 defined between the central collector 10 and the leaktight enclosure 1 is connected to admission means for the second B which are formed by at least one tube 16 passing through the cover 3 of said leaktight enclosure 1.
As shown in particular on FIGS. 1, 2, and 4, the installation includes means for exchanging heat between the fluids A and B, which means comprise bundles of plates 20 disposed in the annular space 5 provided between the central collector 10 and the leaktight enclosure 1.
In the enclosure shown in the figures, the bundles of plates 20 are distributed in a star configuration around the central collector 10, and they are eight in number, for example. In conventional manner, each bundle of plates 20 is generally in the form of a rectangular block, and it is formed by a stack of horizontal metal plates 21 of small thickness, and made of stainless steel, for example. These plates 21 are provided with corrugations that are not shown. The plates 21 in each bundle of plates 20 define between one another two circuits for countercurrent flow respectively of the fluids A and B.
As can be seen in particular in FIGS. 2 and 4, each bundle of plates 20 includes a front vertical wall 22 secured on the central portion 11 of the collector 10, a rear vertical wall 23 that is free projecting into the annular space 5, and two side walls 24 extending perpendicularly to said central portion 11 of the collector 10.
As shown in FIG. 4, each bundle of plates 20 has its bottom portion resting on a support member 25 secured to the leaktight enclosure 1. Each support member 25 is formed by a horizontal plate 25 a with the bottom portion of the corresponding bundles of plates 20 bearing slidably thereagainst, and a vertical plate 25 b extending perpendicularly to said horizontal plate 25 a.
As shown in FIG. 5A, the front wall 22 is provided with inlets and outlets for the fluids A and B that are formed, for each circuit, by an alternating superposition of open ends 26 a and 26 b respectively for the first fluid A and for the second fluid B, or closed ends 27 a and 27 b respectively for the first fluid A and for the second fluid B.
The open ends 26 a of the circuit inlets for the first fluid A are situated in the middle of the front wall 22, and the open ends 26 b of the outlets of the circuit for the second fluid B are situated in the side margins of the front wall 22. The open ends 26 a for the first fluid A open out into the central collector 10 and as a result they are connected to the admission tube 14 for the first fluid A.
The open ends 26 b of the outlets for the second fluid B in the side margins of the front wall 22 of two adjacent bundles of plates 20 are interconnected, as shown in FIGS. 3 and 4 by an annular collector 30 concentric about the central collector 10.
In its bottom portion, the annular collector 30 has a hemispherical cap 31 surrounding the bottom 13 of the central collector 10. This hemispherical cap 31 is connected to means for discharging the second fluid B that are constituted by at least one tube 32 passing through the leaktight enclosure 1 in its bottom portion, as shown in FIGS. 1 and 3. This tube 32 is provided with at least one expansion compensator 33.
As shown in FIG. 5B, the rear wall 23 of each bundle of plates 20 has inlets and outlets for each of the fluids that are formed, for each circuit, by an alternating superposition of open ends 28 a and 28 b, respectively for the first fluid A and for the second fluid B, or closed ends 29 a and 29 b respectively for the first fluid A and for the second fluid B.
In the embodiment shown in FIG. 5B, the open ends 28 b of the inlets of the circuit for the second fluid B are situated in the middle of the rear wall 23, and the open ends 28 a of the outlets for the first fluid A are situated in the side margins of said rear wall 23. The open ends 28 b of the inlets for the second fluid B open out into the annular space 5 arranged between the collector 10 and the leaktight enclosure 1, which itself communicates directly with the admission tube 16 for the second fluid B into said annular space 5.
As shown in FIGS. 3 and 4, the open ends 28 a of the outlets for the first fluid A are covered by vertical collectors 35. As a result, each vertical row of open ends 28 a of outlets for the first fluid A is covered by a collector 35, and each collector 35 is extended at its top end by at least one pipe 36 provided with at least one expansion compensator 37. Each pipe 36 is connected to a collector ring 40, itself connected to means for discharging the first fluid A that are formed by at least one tube 41 passing through the cover 3 of the leaktight enclosure 1.
In a variant that is not shown, the open ends 28 b of the inlets for the second fluid B can be situated in the side margins of the rear wall 23 and the open ends of the outlets 28 a for the first fluid A can be situated in the middle of the rear wall 23. In such a configuration, the vertical row of open ends 28 a of outlets for the first fluid A from each bundle of plates 20 is covered by a collector 35 connected by a pipe 36 to the collector ring 40.
As shown in FIG. 2, each bundle of plates 20 includes a vertical deflector on each of its side walls 24, the deflector extending towards the adjacent bundles of plates 20.
The free edges 45 a of two contiguous deflectors overlap so as to allow the second fluid B to pass through and create around the central collector 10 a buffer zone of said second fluid B.
A deflector 46 is placed around the admission tube 14 for the first fluid A, and another deflector 47 is likewise placed beneath the bundles of plates 20 between the hemispherical cap 31 of the central collector 10 and the bottom 4 of the leaktight enclosure 1.
With reference now to FIG. 3, there follows a description of how the fluids A and B flow through the installation.
The hot first fluid A which is at a temperature of about 800° C. penetrates via the admission tube 14 into the central collector 10, and is then directed into the inlets 26 a of each of the bundles of plates 20.
The second fluid B which is at a temperature of about 200° C. penetrates via the admission tube 16 into the annular space 5 formed between the central collector 10 and the leaktight enclosure 1. This second fluid B is directed towards the inlets 28 b in the rear wall 23 of each of the bundles of plates 20. The flow of fluids A and B in the independent circuits of each of the bundles of plates 20 leads to heat being exchanged between these fluids so that the first fluid A is cooled down after passing through each bundle of plates 20 and leaves via the outlet ends 28 a of the bundles of plates 20 so as to be collected by the vertical collectors 35. The cooled first fluid A passes along the pipes 36 and penetrates into the collector ring 40 prior to being discharged from the installation via the tube 41.
Simultaneously with this first fluid A circulating through the installation, the second fluid B penetrates via the admission tube 16 into the leaktight enclosure 1 at a temperature of about 200° C. After filling the annular space 5, this second fluid B penetrates through the open ends 28 b in the rear walls 23 of each of the bundles of plate 20 and passes through each of these bundles of plate 20 as a counterflow to the first fluid A. Heat exchange is thus established in each of the bundles of plates 20 between the fluids A and B, so the second fluid B is thus heated and is discharged from the open ends 26 b of each of the bundles of plates 20 and is then collected by the annular collector 30 prior to being discharged through the space provided between the bottom 13 of the central collector 10 and the hemispherical cap 31, and then via the tube 32.
When the hot fluid A and the cold fluid B pass through the various elements of the installation, and in particular through the bundles of plates 20, the thermal stresses that are generated lead to the plates 21 of the bundles of plates 20 expanding, and given that each of these bundles of plates is supported inside the leaktight enclosure 1 by sliding support organized between these bundles of plates 20 and the support members 25, these bundles of plates can expand freely, thus enabling large thermal stresses to be avoided in each of the bundles of plates 20. The same applies to the admission tube 14 for the hot fluid, to the discharge tube 32 for the cold fluid that has been heated after passing through each of the bundles of plates 20, and also to each of the pipes 36, all of which are fitted with respective expansion compensators 15, 33, and 37.
The heat exchanger installation of the invention presents the advantage of concentrating the inlet of hot fluid in the center of the leaktight enclosure 1 by means of the central collector 10 and of surrounding this hot zone with a peripheral cold buffer zone by using the respective deflectors 45, 46, and 47 around the hot fluid admission tube 14, the central collector 10, and the discharge tube 32 for heated fluid.
These buffer zones as provided in this way around the hot zones make it possible to provide a leaktight enclosure 1 of relatively small thickness compared with the leaktight enclosures in heat exchanger installations that have been in use in the past.
Because of its design, the heat exchanger installation in accordance with the invention presents the advantage of being compact and of presenting a large heat exchange area, while enabling the various elements making it up to expand freely given the large temperature difference between the hot fluid and the cold fluid.

Claims

1. An installation for exchanging heat between fluids, the installation being of the type comprising a vertical leaktight enclosure of elongate shape, heat exchanger means between the fluids, and admission means and discharge means for a first fluid A and for a second fluid B, wherein the heat exchanger means comprise bundles of plates formed by stacks of horizontal plates defining between them two flow circuits for countercurrent flow of the two fluids A and B distributed in a star configuration around a tubular central collector concentric with the enclosure, and wherein each bundle of plates has a front vertical wall secured to the central collector and provided with inlets and outlets for each of the fluids A and B, and a rear vertical wall that is free and provided with inlets and outlets for each of the fluids A and B, each bundle of plates being slidably supported on a support member secured to the leaktight enclosure.

2. An installation according to claim 1, wherein the fluid inlets and outlets provided in the front walls are formed, for each circuit, by an alternating superposition of open or closed ends, the open ends of the circuit inlets for the first fluid A being situated in the middles of the front walls, and the open ends of the circuit outlets for the second fluid B being situated in the side margins of the front walls.

3. An installation according to claim 2, wherein the open ends of the inlets for the first fluid A open out into the central collector connected to the admission means for said first fluid A.

4. An installation according to claim 3, wherein the admission means for the first fluid A are formed by at least one tube passing through the enclosure and connected to the top portion of the central collector, said tube being provided with at least one expansion compensator.

5. An installation according to claim 2, wherein the open ends of the outlets for the second fluid B in the side margins of the front walls of two adjacent bundles of plates are interconnected by an annular collector concentric about said central collector and including, in its bottom heat exchanger, a hemispherical cap connected to the means for discharging said second fluid B.

6. An installation according to claim 5, wherein the means for discharging the second fluid B are formed by at least one tube passing through the leaktight enclosure in its bottom portion, said tube being provided with at least one expansion compensator.

7. An installation according to claim 1, wherein the inlets and outlets for the fluids A and B provided in the rear walls are formed, for each circuit, by an alternating superposition of open or closed ends, the open ends of the circuit inlets for the second fluid B being situated in the middles of the rear walls, and the open ends of the outlets for the second fluid A being situated in the side margins of the rear walls.

8. An installation according to claim 1, wherein the fluid inlets and outlets formed in the rear walls are formed, for each circuit, by an alternating superposition of open or closed ends, the open ends of the circuit inlets for the second fluid B being situated in the side margins of the rear walls, and the open ends of the outlets for the first fluid A being situated in the middles of said walls.

9. An installation according to claim 7, wherein the open ends of the inlets for the second fluid B open out into the annular space between the central collector and the enclosure, said annular space being connected to the admission means for said second fluid B.

10. An installation according to claim 9, wherein the admission means for the second fluid B are formed by at least one tube passing through the enclosure and opening out to the inside of said enclosure.

11. An installation according to claim 7, wherein the open ends of the outlets for the first fluid A are covered by a collector connected by at least one pipe provided with at least one expansion compensator to a collector ring connected to the means for discharging the first fluid A.

12. An installation according to claim 1, wherein each bundle of plates on each of its side walls has a respective vertical deflector extending towards the adjacent bundle of plates, the free ends of two contiguous deflectors overlapping.

13. An installation according to claim 1, wherein the first fluid A is a hot fluid at about 800° C. on admission into the bundles of plates, and the second fluid B is a cold fluid at a temperature of about 200° C. on admission into said bundles of plates.