The state of the art

The heat exchanger body according to the invention is an improvement of the heat exchanger body described in WO2013 / 142924 (corresponding to US2015 / 0090431) or an improvement of the heat exchanger described in US6263961 and US6289978. The contents of these documents are incorporated in the present description by reference.

The heat exchanger body according to this document WO2013 / 142924 is a heat exchanger body between a first fluid (FB) and a second fluid (FA), said body being adapted to be placed in a conduit or duct or a chamber (2) for guiding the flow of the first fluid (FB) into or towards the exchanger body (1), this exchanger body (1) comprising: an element (3) adapted to be located at least partially in said duct or chamber (2), said element (3) consisting of two sheets (30, 31) made of heat-conducting material, said sheets being connected to one another at least in the vicinity of their longitudinal edges (30 A, 30B, 31 A, 3 IB) to define between them one or more inner channels (32) for said second fluid (FA), said element (3) being wound to form a substantially spiral structure (3) extending into said duct or conduit or chamber (2) so as to define in the duct or conduit or chamber (2) between the adjacent spiral faces of the element (3) one or more channels (36) for the first fluid (FB), at least two substantially radial distributors (4) for bringing said second fluid (FA) into the element (3) in the vicinity of a first longitudinal edge (30A, 31 A) at different turns of the substantially spiral structure (3), and at least two

substantially radial collectors (5) for collecting said second fluid (FA) after passing through said element (3), said collectors (5) being adapted to collect said second fluid (FA) in the vicinity of the second longitudinal edge (30B, 3 IB) at different turns of the substantially spiral structure (3), in which the first sheet (30) and the second sheet (31) forming the element (3) have in a central zone deformations respectively forming a first series of channels (33) and a second series of channels (34), the edge (33A) of the channels (33) of the first series of the first sheet (30) facing the second sheet (31) contacting the edge (34A) of the channels (34) of the second series of the second sheet (31) forcing said second fluid (FA) to flow following a path between at least one of the distributors (4) and at least one of the collectors (5), said path being formed by channels (33) of the first series and channels (34) of the second series, wherein the substantially spiral structure (3) has a central axis (AC), and wherein in each radial plane (PR) passing through said central axis (AC), the channels (33) of the first series of a turn of the substantially spiral structure form sections of passage extending between a first radial distance (Rl) from the central axis (AC) and a second radial distance (R2) from the central axis (AC) which is greater than the first radial distance (Rl), while the channels (34) of the second series of the turn in consideration form sections of passage extending between a third radial distance (R3) from the central axis (AC) and a fourth radial distance (R4) equal to or smaller than said first radial distance (Rl) from the central axis (AC), but which is greater than the third radial distance (R3).

Although this heat exchanger body has many advantages as regards the recovery of energy contained in the flue gases, the practice or usage has shown that such heat exchanger bodies have one or more of the following potential problems:

• The build-up of large pressure losses for the fluid FA flowing in the space defined between the sheets forming the spiral element. These pressure drops do not make it possible to ensure a completely homogeneous flow of the second fluid FA in the spiral element 3. The fluid FA enters the element 3 via a distributor having slots into which are introduced longitudinal end open portions of the spiral element. The collector is associated to the spiral element in the same way as for the distributor. These large pressure drops force to create a sufficient overpressure at the distributor side, which requires the use of robust distributors.

• The longitudinal ends of the sheets are welded to each other after flattening, further reducing the passage section of the second fluid (FA) in the interior space of the spiral element. In addition, such flattenings create zones of tension or zones favoring the deposition of limestone, etc.

• The winding of the spiral sheets creates tension especially along the longitudinal edges, leading to a reduction of the fatigue resistance.

• Problem related to mechanical stresses generated during the appearance of hot spots, which is particularly the case during a fouling in the interior volume of the element 3.

• Sealing problem at the longitudinal ends.

• Problem at the passages allowing the passage of the hot gas in the free space out of the element (3) in spiral.

• Difficulties in positioning and mounting the collector elements or liquid distributors on a spiral exchange body.

• Difficult construction to ensure a good tightness.

Brief description of the invention

The subject of the invention is an exchange body which makes it possible to at least partially solve one or more of the potential problems listed above.

The exchange body according to the invention is an exchange body of the type described above, which furthermore has the following characteristics:

• the first sheet (30) and the second sheet (31) each have along each of their longitudinal edges (30A, 31A, 30B, 31B) a smooth zone (Zl, Z2, Z3, Z4) with no deformations forming channels extending or lengthening each one or more channels (33,34) of the first or second series respectively of the first sheet and the second sheet, * each of the smooth zones (Zl, Z2, Z3, Z4) of the first or second sheet (30, 31) defines in a radial plane (PR) for a given turn of the substantially spiral structure (3) a line (Dl, D2, D3, D4) parallel to the central axis (AC) extending respectively between the first radial distance (Rl) and the second radial distance (R2) for the channel sections (33) of the first sheet (30) in said considered radial plane (PR) , and between the third radial distance (R3) and the fourth radial distance (R4) for the sections of the channels (34) of the second sheet (31) in said radial plane in consideration,

* in the vicinity of a first longitudinal edge (30 A) of the first sheet (30) of the substantially spiral structure (3) and a first longitudinal edge (31 A) of the second sheet (31) of the substantially spiral structure ( 3) , at the level of a turn and in a radial plane (PR) in consideration, the smooth zone (Zl, Z3) of the first sheet (30) is located opposite a smooth zone (Z2, Z4) of the second sheet (31) while being spaced therefrom by a first radial spacing distance (ER1) corresponding to at least 50% (in particular from 50 to 90%, preferably from 60 to 85%) of the maximum spacing between the second radial distance (R2) and the third radial distance ( R3) of the sections of the channels (33,34) of the turn in consideration and in the radial plane (PR) in consideration, a first spacer element (El) extending between at least portions of said smooth zones (Zl, Z2) in the vicinity said first longitudinal edges (30A, 31 A) of said first and second sheets (30,31),

* in the vicinity of the second longitudinal edge (30B) of the first sheet (30) of the substantially spiral structure (3) and the second longitudinal edge (3 IB) of the second sheet (31) of the substantially spiral structure (3) opposite respectively to said first longitudinal edge (30 A) of the first sheet (30) of the substantially spiral structure (3) and to said first longitudinal edge (31 A) of the second sheet (31) of the substantially spiral structure (3), at the level of a turn and in a radial plane (PR) in consideration, the smooth zone (Z3) of the first sheet (30) is located opposite a smooth zone (Z4) of the second sheet (31), while being separated or spaced therefrom by a second radial spacing distance (ER2) corresponding to at least 50% (in particular from 50 to 90%, preferably from 60 to 85%) of the maximum spacing distance between the second radial distance (R2 ) and the third radial distance (R3) of the sections of the channels of the turn in consideration and in the radial plane (PR) in consideration, a second spacer element (E2) extending between at least portions of said smooth zones (Z3, Z4) in the vicinity of said second longitudinal edges (30B, 3 IB) of said first and second sheets (30,31),

* third spacers (E3) extend between portions of adjacent turns of the substantially spiral structure (3), and

* said first, second and third spacers (El, E2, E3) define zones of passage (ZP) for the flow of the second fluid (FA) into or out of channels of the first and second sheets (30, 31) from a distributor (4) or to a collector (5) and closed zones (ZO) opposing or preventing the flow of the first fluid (FB) and the second fluid (FA) into channels of the first and second sheets (30,31 ). The flat zones (Zl, Z3 and/or Z3, Z4) can be realized by not corrugating said longitudinal edge parts of the sheets (30,31), but also either by flattening portions of corrugations of a fully corrugated single sheet (figure 21, 22, 23), or by welding a flat sheet or band adjacent to the corrugated sheet (figure 3 and 4).

According to advantageous embodiments, the heat exchange body according to the invention has one or more of the following features, in particular a combination thereof:

- the first spacer element (El) is at least partially compressible and is at least not attached or fixed to at least one of the first and second sheets (30, 31), and/or the second spacer element (E2) is at least partially compressible and is at least not attached or fixed to at least one of the first and second sheets (30,31). Preferably, the first spacer element (El) is at least partially compressible and is at least not attached or fixed to at least one of the first and second sheets (30, 31), while the second spacer element (E2) is at least partially compressible and is at least not attached or fixed to at least one of the first and second sheets (30,31). And/or

- for the first sheet (30) or the second sheet (31) has in the vicinity of its first longitudinal edge (30 A, 31 A) a first smooth zone (Z1,Z2) and in the vicinity of its second longitudinal edge (30B,31B) a second smooth zone (Z3,Z4), in which in a given radial plane (PR), the first smooth zone (Z1,Z2) and the second smooth zone (Z3,Z4) of a sheet (30,31) at the level of a turn of the substantially spiral structure (3) define in each radial plane (PR) two coaxial lines (D1,D3 or D2,D4) parallel to the central axis (AC). And/or

- the first spacer element (El) and/or the second spacer element (E2) or parts thereof is/are integral to the first and/or second sheet(s). For example, a spacer element or portion thereof is integral to the first sheet (30), while the other spacer element or portion thereof is integral to the second sheet (31). The first spacer element and/or the second spacer element can further comprise a portion amovible with respect to the first and the second sheets (30,31). And/or

- in the vicinity of its first longitudinal edge (30B,3 IB) and/or its second longitudinal edge (30A,31A), the first sheet (30) and/or the second sheet (31) are folded or embossed for making one or more protruding parts, said one or more protruding parts forming at least portions of the first and/or second spacer element (E1,E2). And/or

- the first sheet (30) and/or the second sheet (31) is/are made at least partly of at least of two different metallic layers. The sheets can thus be for example bi metallic or bi metallic layered (consisting of two metallic layers covering each other). The sheets can also have the form of a thin metallic core sheet (with a thickness of for example 1 OOmhi upto 3mm) provided on each of its opposite faces with a thin metallic covering layer (with a thickness of for example 20iun up to lmm), the covering layers having the same or different metallic compositions and/or having the same or different thickness. For example, if the temperature on the hot side of the heat exchanger is high (typically above 600°C: like 650°C,

750, °C up to 950°C...) and the temperature on the cold side is low (typically below 300°C: like 150°C.. 250°C...), or if corrosion may arise on one side of the heat exchanger (for instance on the cold side where corrosive condensate may appear), the sheet 30 and 31 can be provided with an anti-corrosion layer or the sheet can be made of two or more than two layers or films attached the one to the other, for example by welding to sheets of different material together (like a stainless steel sheet and an nickel alloy sheet), before the realization of the corrugation pattern, and possible welding of non corrugted edge portions or bands. This reduces the material cost in view of the expensive of sheets made of temperature resistant and/or corrosion resistant alloys. And/or

- third spacers (E3) are located between adjacent turns of the substantially spiral structure (3) so as to define non-passage zones (ZNP) of non passage for the first fluid (FB) from the chamber or conduit or duct (2) towards the volume defined between the turns of the substantially spiral structure (3) and non passage of the first fluid (FB) of the volume defined between the turns of the substantially spiral structure 3 towards the duct or conduit or chamber (2).

Advantageously, the passage zones (ZP) defined by the first and second spacers are located between two third spacers.

Preferably, third spacers (E3) are arranged between the turns of the substantially spiral structure (3) to define radial sectors each associated with a distributor or a collector of the second fluid (FA). And/or

- The first spacer and / or the second spacer are removably mounted between the sheets (30,31) of the substantially spiral structure (3). This allows easy

replacement and easy access to the inside of the exchange body. And/or

- the first smooth zone (Z1,Z3) and / or the second smooth zone (Z2,Z4) of a sheet or sheets have protuberances or stops to ensure correct positioning of the first spacer(s) (El) and / or the second spacer(s) (E2), and / or the third spacer(s) (E3). And/or

- the first spacer (El) and / or the second spacer (E2) is (are) in the form of a series of distinct sections and / or in the form of a continuous band or strip (53) having openings (51) for defining the passage zones (ZP) towards the inner volume of the substantially spiral structure (3) defined between the sheets or zones capable of being deformed (in particular perforated or pierced) to define zones of passage towards the interior or inner volume of the substantially spiral structure (3).

Advantageously, the first and second spacers (El, E2) are in the form of a bead or continuous strip capable of being pierced. This bead or strip is preferably made of closed-cell foam, elastically compressible. And/or

- the distributor (4) and / or the collector (5) is / are a removable part mounted on the substantially spiral structure (3), said part having a face intended to be turned towards the element (3), said face carrying a series of hollow fingers adapted to to be inserted in open areas or openings, or into the piercable portion (53 A) of the coil or continuous band (53) for piercing it . And/or

- the first smooth zone and / or the second smooth zone of one or more sheets is / are extended by one or more folded portions of the first or second sheet (30, 31). The folded portions advantageously have slots extending from the free edge to the fold line, this to facilitate the bending of the smooth zone or zones. And/or

- the first spacer (El) and / or the second spacer (E2) comprise one or more means for guiding the second fluid coming from/flowing through an opening of the spacer in consideration towards a series of channels or one or more means for collecting the second fluid from a series of channels towards an opening of the spacer in consideration. These guiding means are for example constituted by a channel or channels extending in a considered spacer (El, E2) and having a series of openings or passages directed to the channels defined between the two sheets 30,31. And/or

- The first and second sheets (30,31) are attached to each other at least in their central zones having deformations defining channels 33,34. For example, the sheets are connected to each other by soldering points. The welding points are advantageously made during the winding of the sheets 30, 31. And/or

- a combination of two or more of these characteristics.

The invention also relates to a heat exchanger comprising at least one chamber or duct (2) in which is housed at least one exchange body according to the invention, as described above. The exchanger further comprises at least one distributor or a chamber for distributing the first fluid between the turns of the exchange body and / or a collector or chamber for collecting the first fluid (FB) coming out of/flowing from the volume formed between the turns of the body exchange.

The invention further relates to a heat exchanger whose exchange body is removably mounted relative to the chamber or conduit or duct.

In particular, the first and second spacers (El, E2) are mounted at least partially removably with respect to the substantially spiral structure (3).

The subject of the invention is also the use of a heat exchanger according to the invention for ensuring a heat exchange between a first fluid (FB) gaseous flowing through the spaces defined between the turns of the substantially spiral structure 3, and a second liquid fluid FA flowing in the element 3 spirally wound.

In the context of this use, another object of the invention for ensuring an improved maintenance of the heat exchanger is a method of cleaning or maintenance of a heat exchanger according to the preceding claim, said method comprising at least the following steps :

the exchange body is separated from the chamber or duct;

the distributors and the collectors of the exchange body are removed; the spacers (El, E2) of the element (3) are removed at least partially so as to have easy access to the space between the sheets forming the turns of the element (3);

at least one cleaning fluid is passed between the sheets;

at least one gaseous fluid is passed through to remove deposits and the remaining cleaning fluid;

At least partially reinstalls or spacers on the element (3);

- the distributors and collectors are cleaned if necessary;

- the duct or chamber is cleaned if necessary;

- the distributors and collectors are replaced on the element (3), and

the exchange body is replaced in the chamber or conduit or duct.

Features and details of the invention will become apparent from the following detailed description in which reference is made to the accompanying drawings showing embodiments of the invention or parts thereof.

Brief description of the drawings

In these drawings,

- Figure 1 is a plan view of a first sheet (30);

- Figure 2 is a plan view of a second sheet (31);

- Figures 3 and 4 are sectional views along the lines III-III and IV-IV of said first and second sheets (30,31);

- Figure 5 is a sectional view of two sheets (30,31) associated with each other, before winding;

- Figure 6 is a sectional view (in a radial plane) of a series of adjacent turns obtained by winding the sheets (30, 31) of figure 5;

- Figure 7 is a partial front view of the series of adjacent turns of figure 5;

- Figures 8A and 8B / C / D are a sectional view (in a radial plane) of another series of adjacent turns obtained by winding the sheets (30, 31) and views on a larger scale of parts (end parts and central portion) of adjacent turns of figure 8 A;

- Figure 9 is a schematic perspective view of a body including a series of adjacent turns of figure 8A;

- Figures 10, 11 and 12 are views on a larger scale of a longitudinal edge of two turns of figure 9 (lines X-X, XI-XI and XII-XII);

- Figure 13 is a schematic view of a sheet showing the path followed by the second fluid FA between a distributor and collectors, the sheet being shown after flattening;

- Figure 14 is a schematic perspective view of an exchange body, with distributors and collectors;

- Figure 15 is a schematic perspective view of an exchange body according to WO2013 / 142924, while Figure 16 is a view of an exchanger provided with an exchange body according to WO2013 / 142924,

- Figure 17 is a view of the sheets forming the exchange body before winding them;

- Figure 18 is a partial view of a strip or band (53) adapted to form a spacer (El, E2); - Figure 19 is a perspective view of a distributor or collector for an exchange body, and

- Figure 20 is a detail view of a portion of an embodiment of a strip or band (53).

- Figure 21 shows a stack of sheets 30 and 31 alternatively, in which the spacer E2 is replaced by protrusion (embossments) realized in the longitudinal edge portions of the sheet 31, the embossments being in contact with the sheet 30 directly or with possible interposition of a removable spacer portion,

- Figure 22 shows a perspective view of the stack with embossment in the sheet 31 , and

- Figure 23 is a cross section (S-S) in the middle of the embossment showing the contacting surfaces between sheets 31 and 30.

Description of the invention

The invention is an improvement of the exchange body according to WO

2013/142924, or according to US6263961 and US6289978. As an example of an exchange body that can be improved, reference is made to the heat exchange body shown in Figures 15 to 17 of the present document, which correspond to the heat exchange body represented respectively in Figures 1, 21 and 22A of WO

2013/142924.

The heat exchange body according to the invention is a heat exchange body between a first fluid (FB) and a second fluid (FA), said body being adapted to be placed in a conduit, duct or a chamber (2) to guide the flow of the first fluid (FB) into or towards the heat exchange body (1).

The fluids FA and FB can flow in the same general direction (co -current) or in opposite general directions (countercurrent). The fluids FA and FB may be gaseous or liquid and may possibly undergo a phase change (partial or total) in the heat exchanger. For example, a fluid may condense at least partially on the walls of the spiral heat exchanger or evaporate at least partially along the walls of the spiral heat exchanger.

The exchange body (1) comprises:

- an element (3) adapted to be located at least partially in said duct or chamber (2), said element (3) consisting of two sheets (30, 31) made of a heat-conducting material (for example made of steel or aluminium; the sheets having for example, a thickness of less than 2mm, such as from 0.1mm to 1.5mm, like 0.2mm, 0.5mm, 0.8mm, etc.), said sheets being connected to each other at least in the vicinity of their longitudinal edges (30 A, 30B, 31 A, 3 IB) to define between them one or more internal channels (32) for said second fluid ( FA), said element (3) being wound to form a substantially spiral structure extending into said duct or chamber (2) so as to define in the duct (2) between the adjacent spiral faces one or more external channels ( 36) for the first fluid (FB), - at least two substantially radial distributors (4) for bringing/supp lying said second fluid (FA) into the element (3) in the vicinity of a first longitudinal edge (30A, 31 A) at the level of one or more turns, and at least two substantially radial collectors (5) for collecting said second fluid (FA) after passing through said element (3), said collectors (5) being adapted to collect said second fluid (FA) near the second longitudinal edge (30B, 3 IB) at one or more turns, wherein the first sheet (30) and the second sheet (31) forming the element (3) have in a central zone deformations forming respectively a first series of channels (33) and a second series of channels (34), the edge (33A) of the channels (33) of the first series of the first sheet (30) facing the second sheet (31) contacting the edge (34A) of one or more channels (34) of the second series of the second sheet (31) obliges/forces said second fluid (FA) to travel according a path between at least one of the distributors (4) and at least one of the collectors (5), said flow path being formed by both channels (33) of the first series and channels (34) of the second series, wherein the substantially spiral structure has a central axis (AC, axis of the winding), and wherein in each radial plane (PR) passing through said central axis (AC), the channels of the first series (33) of a turn form passage sections extending between a first radial distance (Rl) from the central axis (AC) and a second radial distance (R2) from the central axis (AC) which is greater than the first radial distance (Rl), while the channels of the second series (34) of the turn considered form passage sections extending between a third radial distance (R3) from the central axis (AC) ) and a fourth radial distance (R4) equal to or smaller than said first radial distance (Rl) from the central axis (AC), but which is greater than the third radial distance (R3).

In this figure 15, reference (L) denotes the width of the exchange body, while reference (36) denotes the free space between turns of the element (3) defining the volume (volume outside the element 3) of passage for the first fluid FB. Reference (Z) denotes the direction of the winding axis which is also the central axis AC.

Reference (35) denotes a supply of the second fluid FA intended to bring/feed the fluid FA (for example water) to the radial distributors (4).

In Figures 16 and 17, references (40) and (50) denote external rings for supplying distributors 4 and for collecting fluid from collectors (5), whereas references (100) and (101) denote respectively the supply duct for supplying the first fluid FB and the outlet pipe of the first fluid FB flowing out of the chamber 2.

In figure 17, the reference 102 designates welding points of the sheets 30, 31 between them, advantageously said welding points being made before and / or after and / or during the winding.

In the exchange body according to the invention, the first sheet (30) and the second sheet (31) each have along each of their longitudinal edges (30A, 31 A, 30B, 3 IB) a smooth zone (Zl, Z2, Z3, Z4) having no deformations forming channels each extending one or more channels (33,34) of the first or second series respectively of the first sheet and the second sheet (see Figures 1, 2, 3 and 4 ). Before winding, the smooth zones located on either side of a central zone with deformation to define channels 33, 34 are flat areas without deformation. Once rolled up, the smooth areas form a spiral structure.

Each of the smooth zones (Zl, Z2, Z3, Z4) of the first or second sheet (30, 31) defines in a radial plane (PR) for a given turn a straight line (Dl, D2, D3, D4) parallel to the central axis (AC) extending respectively between the first radial distance (Rl) and the second radial distance (R2) for the sections of the channels (33) of the first sheet (30) in said considered radial plane (PR), and between the third radial distance (R3) and the fourth radial distance (R4) for the channel sections (34) of the second sheet (31) in said radial plane considered (see figures 6 and 7) During the winding, the smooth zones of the sheets thus define a channel with a large radial width with respect to the average radial width of the channels defined between the sheets 30, 31.

In the neighborough of a first longitudinal edge (30 A) of the first sheet (30) of the spiral member structure (3) and a first longitudinal edge (31 A) of the second sheet (31) of the spiral member structure (3), at the level of a turn and for a considered radial plane (PR), the smooth zone (Zl, Z3) of the first sheet (30) is located opposite a smooth zone (Z2, Z4) of the second sheet (31), while being separated therefrom by a first radial spacing or distance (ER1) corresponding to at least 50% (for example from 50 to 90%) of the maximum spacing between the second radial distance ( R2) and the third radial distance (R3) of the sections of the channels (33,34) of the turn considered and in the radial plane considered (PR), a first spacer element (El) extending between at least parts of said zones smooth (Zl,

Z2) in the neighborough of said first longitudinal edges (30 A, 31 A) of said first and second sheets (30,31).

In the neighborough of the second longitudinal edge (30B) of the first sheet (30) of the spiral member (3) and the second longitudinal edge (3 IB) of the second sheet (31) of the opposed spiral member (3) respectively to said first longitudinal edge (30A) of the first sheet (30) of the spiral member (3) and said first longitudinal edge (31 A) of the second sheet (31) of the spiral member (3), at the level of a turn and for a considered radial plane (PR), the smooth zone (Z3) of the first sheet (30) is located opposite a smooth zone (Z4) of the second sheet (31), while being spaced therefrom by a second radial spacing (ER2) corresponding to at least 50% (eg 50% to 90%) of the maximum spacing between the second radial distance (R2) and the third radial distance (R3) of the sections of the channels of the turn considered and for the radial plane considered (PR), a second spacer element (E2) extending between at least portions of said smooth areas (Z3, Z4) in the neighborough of said second longitudinal edges (30B, 3 IB) of said first and second sheets (30,31).

Said first and second spacers (El, E2) with the third spacers (E3) define passage zones (ZP) for the passage and flow of the second fluid (FA) into or out of channels of the first and second sheets (30, 31) from a distributor (4) or to a collector (5) and closed zones (ZO) opposing the passage/flow of the first fluid (FB) and the second fluid (FA) in channels of the first and second sheets (30, 31). (see figure 19 in which the spirals are shown schematically)

The first spacer element (El) is at least partially compressible and is at least non- fixed with at least one of the first and second sheets (30,31), while the second spacer element (E2) is at least partially compressible and is at least not fixed with at least one of the first and second sheets (30,31).

The spacers E3 form, with parts of spacers El, E2, radial zones of non-passage ZNP of fluid for both the first fluid FB and the second fluid FA. Between two non passage zones ZNP, either spacers El, E2 are arranged to close the passage between two sheets 30, 31 of an element 3, or spacers E3 to close off portions of passage between adjacent turns.

Figure 10 shows in section the heat exchange body along a radial plane intersecting a radial section of the exchange body for which the longitudinal edges 30A, 31A of the spiral element 3 are not closed by a spacer El, while spacers E3 extend between the adjacent turns. In this radial section ZP, the passage/flow of the second fluid FA to the inner channels of the element 3 is possible.

Figure 11 shows in section a radial section for which spacers El and E3 form a no passage zone. In this zone, the spacers El and E3 seal firstly the element 3 along the longitudinal edges (the term "longitudinal edge" is used here to mean the end edge of a sheet which, after winding, forms a spiral) of the element structure 3, and secondly the space between adjacent turns. In this radial section comprising spacers El and E3, it is possible to associate the spacers El, E3 with a strip then covering the free spiral edges of the sheets 30, 31.

Figure 12 shows in section a radial section comprising spacers El so as to allow the passage of gas between the turns of element or spiral structure 3.

Figure 13 shows the path followed by the second fluid FA (in solid lines) along the front face of the sheet shown in developed or plane form and by the first fluid FB (in dashed lines) along the rear face of the sheet 30. The spacers El and E2 are shown along the front face of the sheet. In the central part, the movement of the fluids FA, FB describes zig-zags following the deformations forming the channels 33.

Figure 18 is a schematic view of a spacer El, E2 in the form of a flexible and compressible strip or band 53 having passages for the second fluid FA. The upper face of the strip is provided with a layer or film that can be either withdrawn or pierced to allow passage of the second fluid FA through the band 53.

Figure 19 shows in perspective a distributor or manifold or collector 4,5 with on a flat face 55 hollow fingers 55 A intended to form passages for the second fluid FB. These fingers 55 A then are suitable to possibly pierce the film, strip and / or band, and / or to fit tightly in passages 51 of the band.

Figure 20 shows that the band 53 has an opening 51 associated with a flared part to serve as a means for distributing the second fluid FA to several channels or for collecting the second fluid from several channels 33, 34.

The band 53 advantageously leaves part of the smooth zones facing one another, this part then forming a kind of spiral ring distribution or collection of the second fluid FA.

As it can be seen from the figures, it appears that:

- for the first sheet (30) or the second sheet (31) has in the vicinity of its first longitudinal edge (30 A, 31 A) a first smooth zone (Zl, Z2) and in the vicinity of its second longitudinal edge (30B, 3 IB) a second smooth zone (Z3, Z4), in which in a determined radial plane (PR), the first smooth zone (Zl, Z2) and the second smooth zone (Z3, Z4) of a sheet (30, 31) define at the level of a turn in each radial plane (PR), two coaxial lines (Dl, D3 or D2, D4) parallel to the central axis (AC).

- third spacers (E3) are located between adjacent turns of the element (3) of the element (3) so as to define non-passage zones (ZNP) of the first fluid (FB) of the chamber or conduit (2) to the volume defined between the turns of the element 3, as well as of the first fluid (FB) of the volume defined between the turns of the element (3) to the conduit or chamber (2).

- The passage/flowing zones (ZP) defined by the first and second spacers (El, E2) are located between two third spacers (E3).

- Third spacers (E3) are arranged between the turns of the element (3) to define radial sectors each associated with a distributor (4) or a manifold (5).

- The first spacer (El) and / or the second spacer (E2) are removably mounted between the sheets (30,31) of the element (3). For example, they are inserted between two smooth zones and held in position thanks to the compression of the band between the smooth zones.

- the first smooth zone (Zl, Z3) and /or the second smooth zone (Z2, Z4) of a sheet or sheets have protuberances or stops (50) to ensure correct positioning of the first spacer(s) (El) and / or the second or second spacer(s) (E2), and / or the third spacer(s) (E3).

- the first and / or second spacers (El, E2) are in the form of a series of distinct sections and / or in the form of a continuous strip/band (53) having openings (51) for defining the zones of passage (ZP) to the interior volume of the element (3) defined between the sheets (30,31) or zones capable of being deformed or pierced to define the passage zones towards the interior volume of the element (3) . - The first and second spacers are each in the form of a strand or band or continuous strip with a portion (53 A) capable of being pierced or to be removed (for example in the form of a peelable film).

- the distributor (4) and / or the collector (5) is a removable part mounted on the element (3), said part having a face (55) intended to be turned towards the element (3), said face (55) carrying a series of hollow fingers (56) adapted to be inserted into open areas (51) or to pierce the portion (53A) of the strip or flange (53).

- the first smooth zone (Zl, Z2) and / or the second smooth zone (Z3, Z4) of one or more sheets (30, 31) is / are extended by one or more folded portions (ZR) of the first or second sheet (30,31).

- the first spacer (El) and / or the second spacer (E2) comprise one or more means (57) for guiding or dispensing the second fluid (FA) coming from an opening (51) of the retractor in question towards a series channels or means for collecting the second fluid (FA) from a series of channels to an opening of the spacer.

- The first and second sheets (30,31) are attached to each other, in particular during their winding, at least in their central zones having deformations defining channels (33,34).

Figure 21 shows a stack of sheets 30 and 31 alternatively, in which the spacer E2 is replaced by protrusion (embossments) realized in the longitudinal edge portions of the sheet 31, the embossments being in contact with the sheet 30 directly or with possible interposition of a removable further spacer portion. The flat zones Z1/Z3 of the sheets 30 are spaced from the flat zones Z2/Z4 of the sheets 31 by spacer elements El . The spacers E2 are formed by embossments.

Figure 22 shows a perspective view of the stack with embossment in the sheet 31 of figure 21.

Figure 23 is a cross section in the middle of the embossments of the sheet 31 showing the contacting surfaces between sheets 31 and 30. The sheet 30 has folding zones for forming the contacting zones.

The subject of the invention is also a method for cleaning or maintaining an exchanger according to the invention, said method comprising for example the following steps:

- the exchange body is separated from the chamber or duct, for example by removing the distributor/supply chamber or collector /collecting chamber for the first fluid (FB);

- the distributors and the collectors of the exchange body are removed;

- the spacers (El, E2) of the element (3) are removed at least partially so as to have easy access to the space between the sheets (30,31) forming the turns of the element (3);

- at least one cleaning fluid is passed between the sheets (30,31); - at least one gaseous fluid is passed through the space between the sheets (30,31) in order to evacuate/remove possible deposits and remaining cleaning fluid and / or to dry the exchange body;

- At least partially reinstalls or spacers on the element (3);

- the distributors and collectors are cleaned if necessary;

- the duct or chamber is cleaned if necessary;

- the distributors and collectors are replaced on the element or spiral structure (3), and

- the exchange body is replaced in the chamber or conduit.