EP0867680A1 - Space saving heat exchanger - Google Patents

Abstract

The heat exchanger consists of first and second tube panels (3A, 3B) suspended inside a housing, set opposite one another in a vertical plane and connected to external inlet manifolds (4A, 4B) and a common internal outlet manifold (5). Each of the panels has a first series of tubes (31) which extend horizontally in the lower part of the housing from the inlet manifolds, and a second series (32) extending vertically upwards from the first, and a third series (34) of angled tubes which are connected to the second and extend upwards from the middle of the housing to the top, where the outlet manifold (5) is located.

Description

The invention relates to a heat exchanger intended in particular to be installed in a dense external fluidized bed equipping a circulating fluidized bed hearth.

Such a heat exchanger conventionally comprises a collector of a fluid inlet and a fluid outlet manifold connected together by at minus a group of tubes extending in a zigzag in a vertical plane between the inlet manifold and outlet manifold. Zigzags define pins with hair having adjacent branches which are inclined to one another the other (of the order of 8 to 15 °), leaving a certain free space between them. This tilt is necessary to obtain a natural circulation of the bubbles of fluid vapor in the tubes.

Large power installations require surfaces relatively large heat exchange. This leads to multiply the heat exchangers or to provide a large heat exchanger dimensions whose design is governed by the transverse flow of solid.

The object of the invention is to provide a heat exchanger with reduced space requirement, i.e. a heat exchanger of dimensions similar to exchangers of the zigzag tube type but having a larger heat exchange area.

To this end, the invention relates to a heat exchanger, characterized in that it comprises at least a first group of tubes extending in a vertical plane and forming a first panel of tubes for connecting a first fluid inlet manifold arranged in the lower lateral part of a single-chamber outlet manifold arranged in the upper central part of a box, at least one second group of tubes extending in said vertical plane and forming a second panel of tubes for connecting a second inlet manifold for the disposed fluid in the lower lateral part of the box at the outlet manifold, in that the first tube panel and the second tube panel each have first tubes which extend substantially horizontally and parallel the to each other in the lower part of the box, second tubes which are connected by multiple bifurcations to the first tubes and which extend substantially vertically and parallel to each other between the part bottom of the box and the middle part of the box, and of the third tubes bends which are connected by multiple bifurcations to the second tubes and which extend parallel to each other between the middle part of the box and the upper part of the box where they are connected to the outlet manifold, the third tubes of the first tube panel and the third tubes of the second panel of tubes being arranged so as to form a channel flow of solids having an O-shaped cross section, and in this that said first and second tube panels are stiffened in their part low by continuous fins arranged between the adjacent tubes.

According to a particular embodiment of the invention, the first and the second tube panel have a different number of tubes so that these two panels are juxtaposed in said vertical plane along a line vertical offset from a vertical center of the box.

According to yet another particular embodiment of the invention, the exchanger comprises a first set of first and second tube panels arranged alternately in parallel vertical planes and connecting the first inlet manifold to the outlet manifold and a second set of first and second panels of tubes arranged alternately in parallel vertical planes and connecting the second inlet manifold at the outlet manifold, the tube panels of the first set of tube panels being further staggered with the panels tubes from the second set of tube panels so that a panel of tubes from the first set of tube panels having a small number of tube is juxtaposed to a panel of tubes of the second set of panels of tubes having a greater number of tubes, and there is further provided a system of attachment to secure in their lower part the tube panels of the two sets of tube panels having a greater number of tubes.

An exemplary embodiment of the invention is described below in more detail. in relation to the drawings.

Figure 1 shows schematically the exchanger according to the invention mounted in a fluidized bed.

Figure 2 is a very schematic sectional view along ll-ll of the exchanger of Figure 1 equipped with several tube panels.

Figure 1, there is shown very schematically in cross section, part of a dense fluidized bed and more precisely a box 1 consisting of a metal sheet reinforced with stiffeners and an internal concrete layer, this box defining a chamber 2 into which the solids after passing over a low wall downstream of a reception of these solids.

Bedroom 2 is normally fitted with a lower box fluidizing air supply (not shown), air injection nozzles fluidization (not shown) which are arranged in the bottom wall 2A of chamber 2. A heat exchanger 3 according to the invention is shown installed inside room 2.

The heat exchanger 3 comprises a set of tubes intended for convey a heat transfer fluid, for example steam, between two collectors fluid inlet 4A, 4B arranged in the lower lateral part of the box and a outlet manifold 5 of the heated fluid disposed in the central upper part of the box. It is in chamber 2 that the dense fluidization of solids takes place allowing the heating of the fluid in the tubes of the heat exchanger.

The inlet collectors 4A and 4B each consist of a tube extending horizontally along the outer lateral side of the box 1, respectively on the left for the collector 4A and on the right for the collector 4B in figure 1.

The outlet manifold 5 consists of a tube extending horizontally at the upper central part of chamber 2 and more precisely under the upper wall 2B of the chamber 2. This outlet manifold 5 is connected to a tube 6 which passes through the upper wall 2B by a slot 7. The tubing 6 is coated with concrete 8 lining the slot 7 so that the outlet manifold 5 is suspended from the upper wall 2B of chamber 2.

The heat exchanger 3 itself has a first group of tubes extending in a vertical plane and forming a first panel 3A of tubes which connect the first inlet manifold 4A to the outlet manifold 5 and a second group of tubes extending in the same vertical plane and forming a second panel 3B of tubes which connect the second inlet manifold 4B to the outlet manifold 5.

As shown in Figure 1, each panel 3A or 3B of tubes have first tubes such as 31 which extend substantially horizontally and parallel to each other in the lower part of the box. These tubes 31 pass through a side wall of the box through a slot filled with concrete, respectively the left wall in figure 1 for the tubes 31 of panel 3A and the right wall in FIG. 1 for tubes 31 of panel 3B.

Each tube panel 3A, 3B also includes second tubes such as 32 which are connected by multiple bifurcations such as 33 to the first tubes of the panel considered and which extend substantially vertically and parallel to each other between the lower part of the box and the middle part of the box.

Each tube panel 3A, 3B also includes third tubes C-shaped bends such as 34 which are connected by bifurcations multiples such as 35 to the second tubes of the panel considered and which extend parallel to each other between the middle part of the box and the upper part of the box where they are connected to the outlet manifold 5. The bending of the tubes 34 defines the profile of the dense fluidized bed and more particularly the tubes 34 of the first panel 3A and of the second panel 3B form a channel flow of solids whose cross section is O-shaped which facilitates the transit of these solids in transverse flow because they do not encounter almost no obstacles.

We see in Figure 1 that the tubes 31 and 32 are relatively close from each other and form a heat exchange surface at the bottom of the box which is relatively continuous in the vertical plane while allowing a some mobility of solids between adjacent tubes. This provision allows therefore to obtain a fairly large heat exchange surface for a relatively small footprint. Although the exchanger has tubes horizontal like tubes 31, we nevertheless obtain good circulation of heat transfer fluid in the exchanger thanks to the vertical tubes 32 which contribute the proper functioning of the feed in natural circulation.

Each tube panel is stiffened in its lower part at the level tubes 31 and at the bottom of the tubes 32 using continuous fins 36 arranged between adjacent tubes, these fins 36 being represented by hatching in Figure 1.

At the bottom of the exchanger 3, the tubes 31 of the panel 3A are connected to the inlet manifold 4A via a tube 9A in form of collector which extends vertically and the tubes 31 of the panel 3B are connected to the inlet manifold 4B via another pipe 9B in the form of a collector which extends vertically.

Furthermore, at the top of the exchanger 3, the tubes 34 of the panel 3A are connected to the outlet manifold 5 via other tubing 10A in the form of a bottle which extends horizontally and the tubes 34 of the panel 3B are also connected to the outlet manifold 5 via another tube 10B in the form of a bottle which extends horizontally.

The arrangement of the heat exchanger tubes as indicated above allows to design an exchanger configuration with several firsts and second tube panels so as to increase the heat exchange surface without considerably increasing the size of the exchanger.

In Figure 1, there are shown panels 3A and 3B which have a different number of tubes 31 (or 32.34), in the example, 7 tubes 31 for the panel 3A and 5 tubes 31 for panel 3B. Following this realization, the two panels 3A and 3B are juxtaposed in the vertical plane along a line vertical in C offset with respect to a vertical median 11 of the box. A such an arrangement facilitates the mounting of several panels 3A and 3B in the box.

Figure 2 shows very schematically in a section II-II of the box in FIG. 1, a configuration of a heat exchanger according to the invention comprising several panels 3A and 3B. We see that several panels 3A and 3B are interposed in the longitudinal direction of the box.

More particularly, this configuration comprises a first set of tube panels 3A and 3B arranged, on the left in FIG. 2, in alternation (i.e. alternately a 3A panel and a 3B panel) in parallel vertical planes. This first set of tube panels 3A, 3B connects the inlet manifold 4A to the outlet manifold 5. The configuration includes a second set of 3A and 3B tube panels arranged, on the right in FIG. 2, alternately in vertical planes parallel. This second set of tube panels 3A, 3B connects the second inlet manifold 4B to outlet manifold 5.

As shown in Figure 2, the panels 3A, 3B of the first set panels are staggered with panels 3A, 3B of the second set of panels so that a tube panel from the first assembly having a small number of tubes, i.e. a 3B panel, is juxtaposed in the same vertical plane to a panel of tubes of the second assembly having a greater number of tubes, that is to say a panel 3A. The panels 3A and 3B of the two sets of tube panels are as well nested within each other.

This staggered arrangement of panels 3A and 3B facilitates their mounting in the box. In addition, a hanging system is provided for secure in their lower part the tube panels of the two sets of tube panels with a greater number of tubes, i.e. panels 3A, so as to obtain a rigidity of the structure of the exchanger thermal in the vertical direction while leaving the possibility of displacement panels between them in the horizontal direction. This attachment system is shown as an example in Figure 2 by two rods 12 which pass through fins 36 arranged in the lower part of these panels. These two rods 12 are also shown in Figure 1.

In Figure 2, there is shown by way of non-limiting example a heat exchanger structure according to the invention in which 3 panels 3A or 3B of a set of panels as defined above are connected to a tubing 9 welded to an inlet manifold, respectively 4A or 4B, this tubing 9 making these panels 3A or 3B integral in their lower part.

Figure 2 also shows a heat exchanger configuration according to the invention comprising several pipes such as 9 and therefore several triplets of panels 3A or 3B of a set arranged in vertical planes adjacent. In this way, we understand that it is easy to increase the surface heat exchange by multiplying the number of pipes 9 and therefore tube panels.

To stiffen the panels connected to the same tubing such as 9 in their upper part, an additional flange is provided such as 13 (shown in FIG. 1) at the level of the tubes 34.

Tubing such as 10A and 10B also being welded to the manifold outlet 5, the exchanger according to the invention is self-supporting.

Claims (3)

Heat exchanger for dense fluidized bed, characterized in that it comprises at least a first group of tubes extending in a vertical plane and forming a first panel of tubes (3A) for connecting a first inlet manifold (4A) of a fluid arranged in the lower lateral part of a box (1) to an outlet manifold (5) arranged in the upper central part of the box, at least a second group of tubes extending in said vertical plane and forming a second tube panel (3B) for connecting a second inlet manifold (4B) of the fluid disposed in the lower lateral part of the box to the outlet manifold (5), in that the first tube panel (3A) and the second panel tubes (3B) each comprise first tubes (31) which extend substantially horizontally and parallel to each other in the lower part of the box, second tubes (32) which are connected by multiple bifurcations (33) to the first tubes (31) and which extend sen vertically and parallel to each other between the lower part of the box and the middle part of the box, and third bent tubes (34) which are connected by multiple bifurcations (35) to the second tubes (32) and which extend parallel to each other between the middle part of the box and the top part of the box where they are connected to the outlet manifold (5), the third tubes (34) of the first panel of tubes (3A) and the third tubes of the second panel of tubes (3B) being arranged to form a solids flow channel having an O-shaped cross section, and in that said first and second tube panels (3A, 3B) are stiffened in their lower part by continuous fins (36) disposed between the adjacent tubes. Exchanger according to claim 1, in which the first and the second tube panel (3A, 3B) have a different number of tubes (31,32,34) so that these two tube panels are juxtaposed in said plane vertical along a vertical line offset from a vertical median (11) of the box. Exchanger according to claim 2, comprising a first set of first and second tube panels (3A, 3B) arranged alternately in parallel vertical planes and connecting the first inlet manifold (4A) to the parallel vertical planes and connecting the first inlet manifold (4A) to the outlet manifold (5) and a second set of first and second tube panels (3A, 3B) arranged alternately in vertical planes parallel and connecting the second inlet manifold (4B) to the outlet manifold (5), the tube panels of the first set of tube panels being in in addition staggered with the tube panels of the second set of tube panels so that a tube panel of the first set of tube panels having a small number of tubes is juxtaposed in the same vertical plane to a panel of tubes of the second set of tube panels having a greater number of tubes, and in which it is provided with a fastening system (12) for securing in their lower part the tube panels of the two sets of tube panels having a plus large number of tubes.

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