EP0051036A1 - Surface heat exchanger for the recuperation of heat - Google Patents

Abstract

1. Surface heat exchanger for the recuperation, by a circulating fluid, the waste heat contained in heat-carrying effluents, more particularly combustion fumes, and comprising two concentric tubes, an inner tube (2) defining a central passage (4) for the effluents to be cooled and an outer tube (3) surrounding the inner tube at a distance so as to define therebetween a peripheral annular space (5) forming a "water jacket" in which the fluid to be heated flows, and which communicates with the outside through two pipes (8, 9) provided on the outer tube (3) respectively for the intet of the fluid to be heated into the annular space (5) and its outlet, which exchanger is characterized in that it comprises one duct (10) passing longitudinally through the central region of the inner tube (2) and mounted with the water jacket (2, 3) so that the fluid to be heated passes through the exchanger while being divided therein into two parallel circuits.

Description

The present invention relates to surface heat exchangers intended to recover, by a circulating fluid, the waste heat contained in the heat transfer effluents. The invention applies in particular to heat transfer effluents which can easily be channeled in a discharge pipe, such as the combustion fumes produced, for example, in industrial ovens or boilers of heating installations.

Exchangers of this type, usually called "heat recuperators" aim in particular to better use of fuels and are therefore part of the set of measures which contribute to providing an answer to the ever more pressing energy saving requirements.

As an indication, the combustion fumes at the outlet of the usual heating boilers often reach temperatures of 250 ° C and more. The thermal losses thus caused account for almost 20% if not more in the thermal balance and penalize the performance of the installation all the more. In fact, this latter value must be clearly corrected upwards, if one takes into account the enthalpy of phase change of the water vapor contained in the fumes.

Thanks to heat recuperators, this lost smoke can be a free source of energy, for example for the production of domestic hot water, or for heating the water returning to the boiler in central heating installations. .

However, an optimal design of these devices must necessarily satisfy a compromise between contradictory requirements to which the currently known recuperators do not seem to satisfactorily cool the combustion fumes as much as possible, disturbing their flow to the chimney as little as possible. 'evacuation.

• - Les dispositifs dits "à paroi d'eau", constitués essentiellement de deux conduits concentriques, à distance l'un de l'autre. Ces conduits définissent entre-eux un espace annulaire dans lequel un fluide à chauffer, en général de l'eau, circule à co-, ou à contre-courant des fumées à refroidir s'écoulant dans un conduit intérieur, l'échange se faisant au travers de la surface de ce dernier (brevets français n° 2 257 875 et n° 2 445 935).
• - Les dispositifs dits "à écran d'eau" dans lesquels un conduit de fumées est traversé transversalement soit par un réseau de tubes à eau agencés en faisceau multitubulaire ou en serpentin (brevet français n° 2 293 674) soit par une ou plusieurs plaques creuses ajourées à circulation d'eau interne (brevet français n° 2 287 663).

Indeed, current recuperators can be classified schematically into two families:

• - The so-called "water wall" devices, essentially consisting of two concentric conduits, spaced from each other. These conduits define between them an annular space in which a fluid to be heated, generally water, circulates in co-or against the current of the fumes to be cooled flowing in an interior conduit, the exchange being made at across the surface of the latter (French patents No. 2,257,875 and No. 2,445,935).
• - The so-called "water screen" devices in which a flue is crossed transversely either by a network of water tubes arranged in multitubular bundle or in serpentine (French patent n ° 2 293 674) or by one or more plates perforated hollow with internal water circulation (French patent n ° 2 287 663).

The performance of recuperators of the first family is penalized by an exchange surface which is necessarily limited not only in size, but also by its location at the periphery of the hot gas stream.

Those of the second family are in principle more thermally efficient. However, the back pressure generated in the gas stream by the pressure losses and the occasional reduction in the cross-sectional area by the presence of the water screen requires an adaptation of the heat generator which, too, has its limits and its disadvantages. Furthermore, these devices are generally noisy. In addition, if the gases to be cooled are combustion fumes, the solid unburnt particles which they transport settle and accumulate in the dead volumes inevitably created in the gas flow.

The object of the present invention is to succeed in extracting the maximum number of calories from the combustion fumes and, more generally from any heat-carrying effluent, while disturbing their flow as little as possible.

To this end, the subject of the invention is a surface heat exchanger for the recovery, by a circulating fluid, such as water, of the waste heat contained in the heat transfer effluents, in particular in the combustion fumes, and comprising two concentric ducts: an inner duct through which the heat-transfer effluents to be cooled pass and an outer duct surrounding the inner duct at a distance so as to define between them an annular space forming a wall of water in which the fluid to be heated circulates, exchanger characterized in that the water wall is with multiple passages, and in that it comprises at least one water tube traversing longitudina The central region of the interior duct and mounted in parallel with the water wall.

By "multiple passage water wall" is meant a compartmentalisation of the annular space allowing the fluid to be heated to circulate in a longitudinal serpentine path, by means of rectilinear fins arranged in parallel and in staggered rows according to the generatrices of the inner duct, or along a helical path, for example, by means of a spiral fin surrounding the inner duct.

To fix the ideas, it will be assumed subsequently that the effluents to be cooled and the fluid to be heated are combustion fumes and water respectively, without it being possible to limit the nature of the fluids participating in these examples to these examples. heat exchange.

• D'un cδté, la paroi d'eau à passages multiples augmente le temps de séjour de l'eau en circulation contre le surface du tube intérieur, ce qui entraine une augmentation corrélative de la quantité de chaleur cédée à l'eau par les fumées, et plus précisément par la région périphérique de la veine de fumées en écoulement qui se trouve ainsi très efficacement refroidie.

As can be understood, the invention therefore achieves the combination within a single device, of already known technical solutions, but separately and by adapting them so as to combine their respective advantages without having to bear the disadvantages:

• On the one hand, the multi-pass water wall increases the residence time of the circulating water against the surface of the inner tube, which results in a correlative increase in the amount of heat transferred to the water by the fumes. , and more precisely by the peripheral region of the flue gas stream which is thus very effectively cooled.

On the other side, the, or more generally, the water tubes placed longitudinally in the central part of the inner duct will seek the remaining calories where they are, that is to say at the very heart of the vein. smoke, thus combining their action with that of the water wall to extract the maximum amount of smoke from the smoke in favor of the water to be heated. This is achieved without significantly disturbing the flow of smoke, since the tubes are arranged longitudinally.

The efficiency of the exchange also causes significant condensation of the water vapor contained in the fumes. This elimination of the vapor in liquid form within the exchanger is favorable from all points of view.

Thermally, it allows the latent heat of condensation of water to be recovered. Then aerodynamically, the decrease the resulting smoke flow compensates for the reduction, albeit minimal, of the passage section due to the presence of the central tubes.

Furthermore, the latter, being mounted in parallel with the water wall, have, as we will see in more detail below, bent ends which, far from representing an obstacle to the flow of smoke, on the contrary constitute cold spots favoring the condensation of steam.

On the other hand, the water wall with multiple passages cause particularly advantageous side effects.

Indeed, the partitioning fins being advantageously made of a material which is a good conductor of heat - generally metal - the exchange surface at this level is therefore increased and with it, the overall heat flux.

In addition, any possibility of water stagnation in the space between the two pipes is avoided, which in addition promotes good circulation of the water in the central tubes since these are mounted in bypass on the wall d 'water.

According to another variant, one end of the flue pipe -corresponding to the entry of the flue gases into the exchanger- comprises means for giving the peripheral part of the gas flow a gyratory movement which further improves the transfer of calories by increasing the duration of the exchange with the water wall.

According to a preferred embodiment, these means consist of fins fixed on edge against the inner surface of the flue pipe and angularly offset in the same direction relative to the longitudinal axis of the pipe so as to be outside any passing plane by this axis.

It should also be emphasized that the device is technologically simple, robust and reliable. Its construction poses no particular difficulty since all of its constituent elements can be found easily in commerce and at low cost.

Its maintenance is very convenient. It is limited to the periodic cleaning of any deposits on the exchange surface, namely the external surface of the central water tubes and the internal surface of the flue pipe.

This cleaning takes place very easily from one end of this conduit, after having freed access to it.

• - la figure 1 est une vue en perspective, partiellement arrachée, d'un récupérateur selon l'invention,
• - la figure 2 est une vue en coupe diamétrale selon le plan AA de la figure 1,
• - la figura 3 est un schéma d'ensemble montrant l'implantation du récupérateur sur une installation de chauffage central,
• - la figure 4 est une vue partielle montrant l'entrée du conduit de fumées équipée d'ailettes déflectrices pour la mise en rotation des fumées.

The invention will be clearly understood and other aspects and advantages will emerge more clearly in the light of the description which follows, given by way of nonlimiting example and with reference to the plates of attached drawings, on which

• FIG. 1 is a partially cut away perspective view of a recuperator according to the invention,
• FIG. 2 is a view in diametral section along the plane AA of FIG. 1,
• - Figure 3 is an overall diagram showing the location of the recuperator on a central heating installation,
• - Figure 4 is a partial view showing the inlet of the flue pipe fitted with deflecting fins for rotating the flue gases.

In the figures, the same elements are designated by identical references.

The recuperator 1, shown in FIGS. 1 and 2, is mainly formed by two concentric remote conduits, respectively interior 2 and exterior 3, defining a central passage 4, for the combustion fumes to be cooled, and a peripheral annular space 5 for a circulation of water to be heated.

As can be seen, the space 5 is closed at its ends by means of flanges 6 and 7. It communicates with the external medium by pipes 8 and 9 provided on the external tube 3 in the vicinity of the flanges 6 and 7 respectively, in diametrically opposite angular positions and serving respectively for the introduction and the exit of the water to be heated, as indicated by the direction of the arrows in the figures.

Of course, the respective roles of these pipes are reversible, the circulation of water being able to operate in one direction or the other. It will however be seen that, in an advantageous variant of the invention, it is preferable to respect the direction of circulation indicated here.

Moreover it is seen that the passage 4 is traversed longitudinally by tubes ₁ 0 (here three in number) located in the central portion of the passage adjacent the longitudinal axis of the symbolized exchanger 11. The tubes 10 are mounted in diversion on the annular space 5 and for this purpose have curved ends at right angles opening into this space by means of openings 12 and 13 formed in the wall of the interior conduit 2, in the vicinity of the pipes 8 and 9 respectively.

According to a preferred embodiment, the annular space 5 is compartmentalized so as to constitute a wall of water with multiple passages.

In the example considered, the compartmentalization is carried out by means of fins 14, arranged in parallel along the generatrices of the inner conduit 2 and spaced from one another so as to define between them longitudinal water chambers. The fins 14 are advantageously constituted by simple steel plates of very elongated rectangular shape and having a slightly shorter length (10 cm for example) than the distance separating the two closing flanges 6 and 7. They are offset longitudinally l '' in relation to the following in a staggered arrangement so as to come into abutment by one end alternately against one and then the other flange, the other end then being free to provide between it and the neighboring flange a passage of communication between two adjacent water rooms.

In the example considered, the number of fins has been limited to four, so that the compartmentalisation has a structure in three superposed stages: an upper inlet stage 15A provided with the inlet pipe 8, an outlet stage lower 15 _C comprising the starting pipe 9 and an intermediate stage composed of the two compartments 15'g and 15 " _B symmetrical on either side of the plane passing through the pipes 8 and 9.

It is clear however that the staggered offset does not apply with respect to the fins delimiting between them the input stage 15A and the output stage 15 _e .

• - Une partie de l'eau passe par l'espace annulaire 5 (ou paroi d'eau) selon un circuit en serpentin à trois passages longitudinaux en se répartissant équitablement entre les deux chambres 15'₈ et 15"_B de l'étage intermédiaire. Au cours de ce parcours, l'eau s'échauffe en prenant les calories contenues dans la région périphérique de la veine gazeuse è refroidir,
• - L'autre partie de l'eau emprunte les tubes centraux 10, pour atteindre directement l'extrémité de sortie de l'étage inférieur 15_C après avoir traversé longitudinalement le coeur de la veine gazeuse et avoir capté les calories restantes localisées dans cette région.

Under these conditions, the water which enters through the inlet pipe 8 joins the outlet pipe 9 after having passed through the recuperator, having shared there in two circuits in parallel, so as to ensure an extraction of the calories contained in all the volume of the smoke stream to be cooled:

• - Part of the water passes through the annular space 5 (or water wall) according to a serpentine circuit with three longitudinal passages, being distributed evenly between the two chambers 15 ' ₈ and 15 " _B of the middle floor. During this course, the water heats up taking the calories contained in the peripheral region of the gas stream to cool,
• - The other part of the water borrows the central tubes 10, to directly reach the outlet end of the lower stage 15 _C after having passed longitudinally through the heart of the gas stream and having captured the remaining calories located in this region .

According to a preferred embodiment of the invention, clearly visible in Figure 2, the partition fins 14 are distributed around the inner tube 2 with variable spacings so that the passage section of the water chambers is not equal in the stages, but gradually decreases from the input stage 15A to the output stage 15 _C. This particular arrangement has the advantage of providing the water in the space 5 with an exchange surface which is all the greater the lower its temperature. In addition, the water is speeded up as it warms up, which is also favorable from a thermal point of view, for example with regard to the risks of calefaction. We find here, the explanation of the remark made previously concerning the reversibility of the roles of the pipes 8 and 9.

In accordance with an advantageous ease of use of the recuperator, and in application of rules well known in thermal, a circulation of the type against the current of water is favored with respect to the flow of fumes. This condition is always satisfied when, as shown in FIG. 1, the inlet pipe 8 is placed at the downstream end of the recuperator with respect to the direction of flow of the fumes (indicated by the arrow on the axis 11). It can be seen in FIG. 2 in particular, that in this case, the water wall 5 comprises two counter-current passages (stage 15A and 15 _C ) for a co-current passage (stage 15 _B ). In this figure, the direction of circulation of the water and the fumes has been indicated by the conventional symbols. Of course, when the number of stages is of even order, the passages in co- and counter-current of the water wall 5 are in equal number, independently of the choice of the inlet pipe.

We will now briefly describe a method of manufacturing the recuperator according to the invention.

We start by welding the closing flanges 6 and 7 on the periphery of the inner conduit 2 and preferably about ₁ 5 or 20 cm from these ends so as to provide free end portions which will allow easy mounting of the device on the installation for which it is intended. These flanges are of slightly different sizes: one of them, for example the flange 6, has a diameter equal to the outside diameter of the duct 3, while the flange 7 has a diameter equal to the inside diameter of the duct 3 and determines so the thickness of space 5.

Then the openings 10 and ₁₁ are drilled and the central tubes 10 are fixed by sealed welding to the edge of the orifices made from the outside of the duct 2. Previously, the tubes 10 were shaped as "S" by bending the ends in opposite directions, from sections of drawn steel tube that are readily available commercially. The fins 14 are then placed on edge on the inner duct 2, taking care to press one of their ends against one of the closing flanges, so as to make a staggered arrangement, as explained above. The fins, which have a height equal to that of the small flange 7, are then fixed permanently by welding.

Furthermore, the two openings intended to receive the pipes 8 and 9 for the inlet and outlet of the water are drilled on the outer conduit 3.

Then, place the inner conduit 2 vertically, the largest flange (flange 6) being in the low position, and then install the outer conduit 3 by sliding it from top to bottom on the inner conduit 2 until that it comes into abutment on the flange 6. This operation is facilitated by the fins which serve as guiding and centering members. The outer conduit 3 has been previously dimensioned so that, once in place, its upper end comes in the plane of the outer surface of the flange 7. The assembly of the two conduits 2 and 3 is then carried out at the level of the two flanges by the sealed weld beads 16 and 17 visible in FIG. 1.

It should be emphasized that the correct angular positioning of the external duct is simplified by virtue of the various orifices previously formed on the two ducts 2 and 3 and which serve as visual cues.

Once the assembly has been carried out, the pipes 8 and 9 are attached by welding to the external pipe 3. It is advantageous to complete the construction by insulating the recuperator by means of a thermal insulation envelope placed around the external pipe 3. This envelope has not been shown so as not to overload the figures unnecessarily.

We will now briefly describe, with reference to FIG. 3, a central heating installation equipped with an exchanger-recuperator according to the invention. In this figure, there is shown very schematically at 18 a boiler supplying hot water, by a conventional system of closed loop pipes comprising a four-way valve 19 and an accelerator 20, a set of radiators 21 for heating living quarters. The combustion fumes exit at the rear of the boiler to reach the exhaust vent chimney, shown at 22.

As can be seen, the heat exchanger-recuperator 1 is installed between the boiler and the chimney 22, replacing the usual boiler outlet pipe. The installation is carried out without particular difficulty thanks to the free end portions of the internal conduit which protrude on either side of the apparatus and which allow by simple fitting to be connected to two bent elements 23 and 24 which have been provided to ensure vertical orientation of the recuperator.

It should be emphasized that the presence of these bent elements is by no means imperative, the recuperator can be placed in any position. It nevertheless remains desirable to keep a slight inclination on the horizontal, positive in the direction of the flow of the fumes, in order to favor by an orifice such as 25, provided between the recuperator and the boiler (or on the free end part of inner duct), the evacuation of condensates, in particular the water formed in the inner duct by condensation of the water vapor contained in the flue gases.

As can be seen, the recuperator 1 is used as a heater: the heating water, which leaves cooled from the radiators 21, returns to the boiler 18 by first passing through the recuperator 1, which in this case constitutes an accessory of the heating system which improves the redement and therefore allows an eco nomie of fuel.

For purely indicative purposes, tests carried out on a liquid fuel boiler (domestic fuel oil) have shown that it is possible, thanks to the device according to the invention, to lower the temperature of the fumes by a value of more than 250 ° C. at outlet from the boiler up to a residual value of approximately 80 ° C at the outlet of the recuperator. From this data, an approximate 15% improvement in the thermal efficiency of the installation is calculated, without taking into account the recovery of the latent heat of condensation of part of the steam. the water leaving the heater shows a temperature rise of 8 ° C. approximately below the usual flow rate, imposed by the heating installation in normal operation (more than 2 m ³ / h).

Other tests carried out with a solid fuel boiler (wood), made it possible to drop the temperature of the fumes by almost 400 ° C, from where a reduction (in percentage) of the losses by the fumes of a similar coefficient of six. Correspondingly, the temperature of the return water rose by 15 ° C.

Furthermore, a circulator, not shown in FIG. 3, may advantageously be provided on the outlet pipe 9 of the heater. In this case, the overall thermal efficiency is further significantly improved thanks to a homogenization of the water temperature within the boiler, due to a permanent stirring effect.

It goes without saying that the invention cannot be limited to the examples described, but extends to multiple variants or equivalents insofar as the characteristics set out in the appended claims are respected.

In particular, numerous variants can be envisaged both with regard to the water wall with multiple passages, as well as the central water tubes or as the relative arrangement of the water wall with these tubes.

With regard to the first point, it has already been said that compartmentalization can be achieved, not only by means of the longitudinal reactive fins 14, but also using for example a single helical fin wound on edge around the inner duct 2.

Likewise, we can opt for multiple agent variants cement rectilinear fins 14, all allowing a circulation of water along a serpentine path with several "back and forth" in the longitudinal direction. In particular, it will be possible to choose between the variants which allow any volume of elementary water entering the annular space 5, or, as in the case of the example described, to travel only one or the other half of the surface of the inner duct 2, that is to cover the whole of this surface, therefore to pass successively through all the water chambers. In this case, the staggered arrangement applies to all of the fins, with the exception of only one, which connects the two flanges 6 and 7 and thus separates the two adjacent chambers in a sealed manner, intended to receive respectively the inlet pipe 8 and the outlet pipe 9.

• - sur le plan hydraulique, les pertes de charges, à débit d'eau égal, sont plus faibles car l'espace annulaire 5 se compose de deux circuits en parallèle recouvrant chacun une moitié de la surface du tube intérieur;
• - sur le plan thermique, le partage de l'espace 5 en deux circuits parallèles équivalents entraine une symétrie de la carte des températures dans toute section droite du récupérateur. Cette symétrie, absente dans la seconde variante'semble globalement favorable à une meilleure transmission du flux thermique; \
• - sur le plan physico-chimique, les tubulures d'entrée 8 et de sortie 9 étant angulairement diamétralement opposées, les tubes à eau centraux 10 traversent la veine de fumées de part en part (tubes 10 conformés en "S"). Il en résulte, non seulement un refroidissement plus complet et plus homogène du coeur de la veine de fumées, mais également une condensation plus importante de la vapeur d'eau, ce qui est un avantage à tout point de vue. Dans la seconde variante, les tubulures d'entrée et de sortie étant angulairement très voisines l'une de l'autre, les tubes centraux présentent une conformation en "U" aplati, de sorte que leur effet d'extrémité reste limité à une partie seulement de l'épaisseur de la veine gazeuse.

It should however be specified that these two variants are not entirely equivalent, but that the first, namely the staged circulation variant, has certain particular advantages over the second:

• - hydraulically, the pressure drops, at equal water flow rate, are lower because the annular space 5 consists of two parallel circuits each covering one half of the surface of the inner tube;
• - thermally, the sharing of space 5 in two equivalent parallel circuits leads to a symmetry of the temperature map in any cross section of the recuperator. This symmetry, absent in the second variant, seems generally favorable for better transmission of the heat flux; \
• - On the physico-chemical level, the inlet 8 and outlet 9 pipes being angularly diametrically opposite, the central water tubes 10 pass through the smoke stream from side to side (tubes 10 shaped as "S"). The result is not only a more complete and more homogeneous cooling of the core of the smoke stream, but also a greater condensation of the water vapor, which is an advantage from all points of view. In the second variant, the inlet and outlet pipes being angularly very close to each other, the central tubes have a flattened "U" shape, so that their end effect remains limited to a part only the thickness of the gas stream.

As far as the second point is concerned, it should be understood that the number of central tubes cannot be fixed a priori for all cases. It essentially depends on the local conditions of use of the recuperator and must be determined in each case in relation to the diameter of the tubes chosen so as not to create in the flow a backpressure which is difficult to accept for the heating installation. As an indication, the smoke outlet pipes of the usual heating systems are generally oversized for safety reasons, so that a reduction in the cross-sectional area in a proportion which can range up to approximately 20% remains entirely - made acceptable. Thus, in the case of a boiler whose smoke evacuation pipe has a diameter of about 180 mm (central heating boiler of an average dwelling house), the replacement of this pipe by a recuperator whose inner tube has an inside diameter of the same dimension and has three central water tubes of 21mm outside diameter, does not cause modifications either to the boiler or to the normal operation of the installation.

Finally, with regard to the third point, concerning the relative arrangement of the central tubes and of the water wall with multiple passages, it should be emphasized that, in accordance with the invention, the water tubes 10 can be mounted as a bypass. total or only partial on the water wall 5. The example described with reference to Figures 1 and 2 corresponds to a total bypass since the openings 12 and 13 on the inner tube 2 were formed in the immediate vicinity of the inlet pipes 8 and outlet 9. Dais it is possible to provide these openings at other places on the inner tube 2 so as to achieve a partial diversion of the tubes 10 on the water wall 5. Such an arrangement is necessary moreover of itself in the case of a water wall with parallel circuits and with an even number of stages, as this is easily understood.

In addition, total diversion can take place not only through the openings 12 and 13 on the inner tube 2, but by any other appropriate means, for example by direct connection of the central tubes 10 to the pipes 8 and 9. .

According to another alternative embodiment, provision is made to equip the space 5 with an air purge.

Similarly, it may be useful to provide a temporary assembly of the external conduit (fixing by bolted flange, for example, instead of welding) so that it can be removed at will for possible cleaning of the annular space. 5 and from the inside of the central water tubes by access to the openings 12 and 13. Of course, this feature is of particular interest if the recuperator is placed in a water circuit of the "open" type, for example in the case of use for direct production of domestic hot water,

Likewise also, in another variant embodiment of the invention, the internal duct 2 is provided, at its end through which the smoke enters, with means for imparting a gyratory movement to the peripheral part of the flowing gas stream. In this way, the duration of passage of the fumes against the wall of the interior duct 2 is increased and the heat transfer is further improved.

As can be seen in FIG. 4, the means used can be deflecting fins 26, constituted by simple metal plates fixed on edge against the inner wall of the duct 2 and angularly offset, for example by 40 °, approximately, all in the same direction with respect to the generatrices of the duct 2 so as to be situated outside any plane passing through the axis of symmetry 11.

The fins 26 are about ten centimeters in length and their height is about a quarter of the diameter of the tube 2 so as to only rotate the peripheral part of the flue gas flow without preferably disturbing the central region where the longitudinal water tubes 10 not shown in this figure.

The recuperator according to the invention can not only be installed between the boiler and the chimney, on existing installations, but also be provided for manufacturing on new boilers.

Finally, the application of the recuperator according to the invention is not limited to the field of central heating for heating the return water from the radiators or for the production of domestic hot water, but extends, as is the case. '' has already said, on recovery, by means of a surface exchanger, of the calories contained in any heat transfer effluent, insofar as the latter is or can be channeled in a discharge pipe,

Claims (11)

1) Surface heat exchanger for the recovery, by a circulating fluid, of the waste heat contained in heat transfer effluents, in particular combustion fumes, and comprising two concentric tubes: an inner duct (2) defining a central passage (4 ) for the effluents to be cooled, and an outer duct (3) surrounding the inner duct at a distance so as to define between them a peripheral annular space (5) forming a "water wall" in which the fluid to be heated circulates and which communicates with the outside by two pipes (8, 9) provided on the outside pipe (3) respectively for the entry of the fluid to be heated in the annular space (5) and for its exit, exchanger characterized in that it comprises at least one tube (10) mounted in parallel with the water wall and passing longitudinally through the central region of the interior duct. 2) Exchanger according to claim 1 characterized in that the water wall with multiple passages is achieved by compartmentalizing the annular space (5) by means of spaced parallel fins (14), staggered according to the generatrices of the inner duct (2) and defining between them longitudinal chambers (15) communicating at one of their ends and traversed by the fluid to be heated. 3) Exchanger according to claims 1 and 2 characterized in that the inlet pipes (8) and outlet (9) of the fluid to be heated provided on the outer conduit (3) are angularly diametrically opposite and in that the compartmentalization of the annular space (5) divides said space into two equivalent parallel circuits each covering one half of the surface of the interior duct (2). 4) Exchanger according to claims 1 and 2 characterized in that the inlet pipes (8) and outlet (Q) of the fluid to be heated provided on the outer conduit (3) have similar angular positions and in that the compartmentalization annular space (5) arranges said space in a circuit covering the entire surface of the inner conduit (2). 5) Exchanger according to claim 1 characterized in that the tube or tubes (10) mounted in parallel with the water wall and passing longitudinally through the central region of the inner conduit (2) open at their respective ends in the annular space ( 5) by openings (12, 13) made on the inner duct (2). 6) Exchanger according to claim 5 characterized in that the openings (12, 13) formed on the inner conduit (2) are arranged in the immediate vicinity of the locations of the pipes (8, 9) provided on the outer conduit (3). 7) Exchanger according to claims 3 and 5 or 6 characterized in that the tube or tubes (10) mounted in parallel with the water wall and passing longitudinally through the central region of the inner conduit (2) have ends bent in directions opposite their conferan- an "S" conformation. 8) Exchanger according to claims 4 and 5 or 6 characterized in that the tube or tubes (10) mounted in parallel with the water wall and passing longitudinally through the central region of the inner conduit (2) have bent ends in the same meaning giving them a "U" shape. 9) Exchanger according to claim 2 characterized in that the fins (14) are distributed around the inner duct (2) with variable spacings so that the passage section of the chambers (15) gradually decreases in the direction of circulation of the fluid to heat. 10) Exchanger according to any one of the preceding claims, characterized in that the internal conduit (2) is provided at one of its ends with means for giving the peripheral part of the flow of the effluents to cool a gyratory movement. 11) Exchanger according to claim 10 characterized in that said means consist of fins (26) fixed on edge against the inner wall of the conduit (2) and angularly offset in the same direction relative to the longitudinal axis (11) so as to be outside any plane passing through said axis.

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