FR2814538A1 - Heat exchanger for gas fired water heating system, has multi-layer pipes arranged in stages with heat conducting fins and condensate guides between them - Google Patents

Abstract

The heat exchanger has interconnected finned (3) pipes (2) through which the fluid flows. The pipes have multi-layer arrangement in several stages, with fins maintained between them. Adjacent pipes amongst the assembly are assembled by brazing connection for thermal exchange between the fluid flowing in the pipes and the combustible gas flowing along the pipes exterior. The fins towards the brazed part (4b) of the pipe to the combustible gas output level. Heat exchanger containing a number of fluid flow pipes (2) having peripheral parts connected by brazing (copper or nickel group material). A number of fins (3) are in contact with the external surface of the pipes so as to increase surface thermal conduction. The pipes are assembled in a multi-layer arrangement of several layers with the fins maintained between them . Adjacent pipes are connected by brazing. The fins have guide parts (9) for discharge of condensed water formed by the thermal exchange between the fluid and combustible gas. The condensed water is discharged through different guide parts from the pipes brazing at the level of the combustible gas output. The guides (9) are arranged on two lateral sides of the space having fins between adjacent pipes. The combustible gas passes through this space with both left and right sides defined by the guides.

Description

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La présente invention se rapporte à un échangeur ther- mique pour échanger la chaleur entre un fluide et un gaz de combustion ou, en particulier, à un échangeur thermique utilisé de manière appropriée avec un dispositif de chauffage d'eau. HEAT EXCHANGER

The present invention relates to a heat exchanger for exchanging heat between a fluid and a combustion gas or, in particular, to a heat exchanger suitably used with a water heating device.

 A conventional heat exchanger is described in, for example, Japanese Unexamined Patent Publication NO 9-126554. This heat exchanger comprises a primary heat exchanger for heating the water by recovering the sensible heat from the combustion gases and a secondary heat exchanger disposed downstream of the primary heat exchanger along the direction of flow of the combustion gas, wherein the latent heat of condensation of the combustion gases is also recovered by the secondary heat exchanger to heat, therefore, the hot water before it is heated in the primary heat exchanger.

 In the secondary heat exchanger described above, however, the temperature of the combustion gases drops to a dew point (50 to 60 C) to generate condensed water containing nitrogen oxide (NOx) or l oxide

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 sulfur (SOx) dissolved in this. In the case where a cup-type heat exchanger can be attached to a large heat conduction surface, is used, therefore, there arises the problem of corrosion of the connecting part of the pipe when the hot water is flows. Specifically, the pipe used for the cup type heat exchanger is normally formed by combining two heat conduction plates along its thickness and by brazing its peripheral edges. In the case where a brazing material from a group Cu is used, the brazing material is corroded by condensed water and a sufficient connection resistance (endurance) cannot be ensured.

 As is well known, this problem can be solved by using an Ni group brazing material as the brazing material as described in Japanese Unexamined Patent Publication NO 9-285888. The water quality guidelines for drinking water, specified by WHO (World Health Organization), however, is that the Ni content should be less than 0.02 mg / 1 when compared to the Cu content less than 0 , 5 mg / 1. It is therefore not desirable to use a brazing material of group Ni for the connection part of the pipe which is liable to be exposed directly to hot water.

 On the other hand, the heat exchange performance of the secondary heat exchanger can be improved by any of the two methods described below.

 (1) Increase the thermal conduction area of the fins.

 (2) Improve the thermal conductivity by suppressing the development of a temperature boundary layer on the surface of the fins.

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 The secondary heat exchanger described above, however, in which the temperature of the combustion gases drops to the dew point by heat exchange with hot water, produces condensed water and poses the following problem.

 For the reason described in (1) above, in the case where a cup-type heat exchanger? is used, which can provide a large heat conduction surface of the fins, a reduced fin pitch or a reduced fin height to reduce the size of the heat exchanger is likely to cause an accumulation of condensed water held between adjacent pipes with the fin between them for increased air flow resistance.

 For the reason described in (2), on the other hand, it is common practice to provide ribs for the fins. Providing the ribs after reducing the pitch of the fins or the height of the fins, however, adversely affects the discharge of the condensed water to reduce performance.

la publication de brevet japonais non examiné NO 2000- 146305, d'autre part, l'échange thermique entre l'eau chaude et les gaz de combustion est encouragé en prévoyant des ailettes constituées de plaques minces sur la surface externe des tuyaux dans lesquels l'eau chaude s'écoule. With the heat exchanger for a water heating device in accordance with the invention described in

Japanese Unexamined Patent Publication NO 2000-146305, on the other hand, heat exchange between hot water and combustion gases is encouraged by providing fins made up of thin plates on the outer surface of the pipes in which the hot water flows out.

 The combustion gas has its temperature reduced by heat exchange with hot water. When the temperature of the flue gas drops below 200 C, for example, condensed water (sulfuric acid and nitric acid) containing a sulfur compound and a nitrogen compound existing in the flue gases may corrosive.

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der les tuyaux et les ailettes constituant l'échangeur thermique.

der the pipes and the fins constituting the heat exchanger.

 In the case where the fins are arranged to extend in a direction parallel to the flow of the combustion gases, the condensed water of the combustion gases generated on the surface of the fins remains fixed and extends over the entire surface of the fins. As a result, the fins are susceptible to rapid corrosion.

 Likewise, the water condensed on the fins constitutes a resistance to heat to block the thermal conduction coming from the combustion gases towards the fins. Thus, the heat resistance increases more at the level of the lower parts of the fins on which the condensed water has a greater thickness, influencing, therefore, unfavorably, the heat exchange efficiency.

 The present invention has been made in view of this situation and one of its aims is to provide a heat exchanger whose operating life can be improved.

 Another object of the invention is to provide a heat exchanger which can obtain improved radiation performance without causing an accumulation of condensed water.

 Yet another object of the invention is to provide a heat exchanger which prevents the water condensed on fins of the fin type from becoming thick and therefore prevents the efficiency of the heat exchange from being deteriorated.

 In accordance with a first aspect of the invention, there is provided a heat exchanger comprising a plurality of fins and a plurality of stages of formed pipes.

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 in a multilayer arrangement holding the fins therebetween, in which the connecting portion of the adjacent pipes is brazed for heat exchange, therefore, between the fluid flowing through the fluid path in the pipes and the combustion gas s flowing down the outside of the pipes. The fins of the heat exchanger extend downwards beyond the brazed part of the pipes at the level of the combustion gas outlet.

 The condensed water generated by the condensation of the combustion gases on the surface of the fins flows down along the surface of the fins and descends from the lower end of each fin. In view of the fact that the lower end of the fin is arranged to be lower from the brazed part of the pipes at the level of the combustion gas outlet, the condensed water flowing down along of the surface of the fins is substantially out of contact with the brazed portion of the pipes. As a result, the brazing material used for the brazed part of the pipes is prevented from being corroded by contact with condensed water and, as a result, the strength (corrosion resistance) of the brazed part can be ensured. for an improved operating life of the heat exchanger.

 In accordance with a second aspect of the invention, there is provided a heat exchanger in which a high temperature gas containing water vapor flows down over the outside of the pipes and a fluid of a temperature lower than the high temperature gas flows in the fluid path in the pipes to heat, therefore, the low temperature fluid by recovering the latent heat of condensation as well as the sensible heat from the high temperature gases, in which fins have a plurality of parts

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 cut and raised portions protruding from its surface in the flow of gas at high temperature, the cut and raised parts being formed only on the upper part of the fins.

 In this configuration, the cut and raised portions of the fins act to guide the high temperature gas to the surface of the fins and, therefore, the development of the temperature boundary layer on the surface of the fins is suppressed for improved thermal conductivity.

 Likewise, in view of the fact that the cut and raised parts are formed only on the upper part of the fins, the condensed water produced by the condensation of the gas at high temperature is not prevented from being discharged by the cut parts and raised and, as a result, the radiation performance is not deteriorated by the accumulation of condensed water.

 In accordance with a third aspect of the invention, there is provided a heat exchanger in which a guide is arranged on each of the left and right sides of the space having disposed therein a fin between each pair of adjacent pipes in a multilayer arrangement, so that the combustion gas passes through the space defined by the guides on the left and right sides, and in which the guides are arranged inside the brazed part of the pipes arranged on the left side and straight along the direction of the flue gas flow and the brazed parts between the pipes.

 In this configuration, the combustion gas passes through the space defined on the left and right sides by the two guides and, consequently, the condensed water, even if it is produced by the condensation of the combustion gas.

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 tion, can be prevented from flowing out of the guides. It follows that the condensed water is kept out of contact with the brazed part of the pipes and the brazed part between the pipes arranged outside the guides, making it therefore possible to ensure the corrosion resistance of the connected parts.

 In accordance with a fourth aspect of the invention, there is provided a heat exchanger, in which a plate is arranged on each side of the brazed part of the pipes arranged at the level of the combustion gas outlet orifice so that the condensed water from the combustion gases descends along the surface of the plates.

 In this configuration, the condensed water, even if produced by the condensation of the combustion gas, descends in the form of droplets along the surface of the plates and, consequently, the condensed water is kept out of contact with the brazed part of the pipes at the combustion gas outlet.

 In accordance with a fifth aspect of the invention, there is provided a heat exchanger, in which pipes have a connection part with a first plate element (first heat conduction plate) and a second plate element (second plate heat conduction) brazed to each other to hermetically define a space between the internal side formed with a fluid path and the external side comprising a path of an external fluid, in which a connection part is formed by winding (seam ) of the first plate member around the second plate member from one surface to the other of the last and holding an end portion of the second plate member tightly from its two sides, and in which both surfaces of the second plate element thus held tightly are connected to the first plate element by

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 the use of different soldering materials, respectively.

 In this configuration, the two surfaces of the second plate member are both coupled to the first plate member. Therefore, a solder material securely exposed to the internal fluid can be used for the internal connection part formed with an internal fluid path and a solder material resistant to corrosion of an external fluid can be used for the part external connection where an external fluid flows.

 In accordance with a sixth aspect of the invention, there is provided a heat exchanger, in which defining elements (pipes) (131) for defining a first path, in which a first fluid flows and a second path, in which a second fluid flows, are configured by brazing metallic elements (133,140), in which the connection parts (133a, 140a) of the definition elements (131) have a double connection structure including first connection surfaces ( 133c, 140d) coupled by a first brazing material and second connecting surfaces (113b, 140d) coupled by a second brazing material different from the first brazing material, and in which recesses (133d, 140b) are formed between the first connecting surfaces (133c, 149d) and the second connecting surfaces (133b, 140e), respectively.

 As a result, the first brazing material suitable for the first fluid and the second brazing material suitable for the second fluid can be selected. In the case where the first fluid is a combustion gas, for example, nickel or the like can be used as the first brazing material, and in the case where the second fluid is hot water,

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 copper or the like can be used as the second brazing material.

 In the case where the heat exchanger, in accordance with the invention, is used for a water heating device, for example, a high corrosion resistance can be ensured while at the same time preventing nickel or the like metal , not suitable for drinking water, to be exposed directly to hot water.

 Although the double connection structure is used, the first brazing material (nickel or similar material in the example described above) melted during brazing can flow to the second connection surfaces (133b, 140e) by a capillary phenomenon with the result that the first brazing material and the second brazing material (copper or similar material in the example described above) are mutually mixed, often often exposing the first brazing material directly to the second fluid (hot water in the example described above).

raccordement (133c, 140d) et les secondes surfaces de raccordement (133b, 140e), respectivement et, en conséquence, l'écoulement du premier matériau de brasage par le phénomène de capillarité est bloqué par les évidements (133d, 140b). In the present invention, in contrast, the recesses (133b, 140b) are formed between the first surfaces of

connection (133c, 140d) and the second connection surfaces (133b, 140e), respectively and, consequently, the flow of the first brazing material by the phenomenon of capillarity is blocked by the recesses (133d, 140b).

 It follows that the first brazing material cannot reach the second connection surfaces (133b, 140e) thanks to the recesses (133d, 140b) and, consequently, the first brazing material can be positively prevented from being directly exposed to the second fluid.

 In accordance with a seventh aspect of the invention, a heat exchanger is proposed in which elements

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mière surface de raccordement (133c) et la seconde surface de raccordement (133b). defining elements (pipes) (131) for defining a first path in which a first fluid flows and a second path in which a second fluid flows are formed by metallic brazing elements (133,140), in which the parts connection elements (133a, 140c) defining elements (131) have a double connection structure including first connection surfaces (133c, 140d) coupled by a first brazing material and the second connection surfaces (133b, 140e) coupled by a second brazing material different from the first brazing material, and in which a surface (133f) inclined at an angle relative to at least one of the first connection surfaces (133c) and of the second connection surfaces (133b) is formed between the first

first connection surface (133c) and the second connection surface (133b).

surface d'inter-raccordement L) peut être accrue lorsque comparée au cas dans lequel une surface dépourvue d'irrégularité est formée entre la première surface de raccordement (133c) et la seconde surface de raccordement (133b), sans augmenter la dimension de l'échangeur thermique. As a result, the length L between the first connection surface (133c) and the second connection surface (133b) (which will hereinafter be called length of

interconnection surface L) can be increased when compared to the case in which an uneven surface is formed between the first connection surface (133c) and the second connection surface (133b), without increasing the dimension of the 'heat exchanger.

 If the first fluid is flue gas, the second fluid is hot water, the first brazing material is nickel or the like and the second brazing material is copper or the like, for example, the first molten brazing material at the time of brazing is prevented from reaching the second connection surface (133b) and, consequently, the first brazing material (nickel or similar material in this example) is prevented from being di-

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 directly exposed to the second fluid (hot water in this example).

 In accordance with an eighth aspect of the invention, there is provided a heat exchanger comprising pipes (131) each having a connection part (141) brazed with a metal element (thermal conduction plate) (133) and each allowing the first fluid to flow therein, wherein the second fluid is allowed to flow around the pipes (131) thereby exchanging heat between the first fluid and the second fluid, the heat exchanger further comprising , a barrier wall (143) formed upstream of the brazed connection portion (141) in the flow of the second fluid to prevent the second fluid from contacting the brazed connection portion (141).

 As a result, the condensed water which causes corrosion is kept out of contact with the brazed connection part (141) and, therefore, the connection part (141) can be brazed with a more suitable brazing material for drinking water. In this way, a heat exchanger is proposed which has a high corrosion resistance but with metallic elements connected by brazing.

 In accordance with a ninth aspect of the invention, a heat exchanger is proposed, comprising pipes (131) each consisting of a metal plate element (thermal conduction plate) (133) having a curved part (144) and a connection part (141) brazed on the side opposite to the curved part (144), in which the pipe (131) allows a first fluid to flow therein and a second fluid to flow around the pipe (131) to exchange, consequently, the heat between the first fluid and the second fluid and in which the curved part (144) is placed downstream of the part of

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 brazed connection (141) in the flow of the second fluid.

 The second fluid flows downstream while having its temperature reduced by the heat exchange with the first fluid flowing in the pipe (131). In the case where the second fluid is the combustion gas, consequently, the condensed water causing corrosion is likely to remain downstream in the flow of the second fluid. To prevent such a situation, in accordance with this aspect of the invention, the curved part (144) is formed downstream in the flow of the second fluid and the brazed connection part (141) is formed on the other side ( upstream side), without posing any corrosion problem because the brazed connection part (141) is not exposed to condensed water.

 In this aspect of the invention, therefore, there is provided a heat exchanger which has a high corrosion resistance with metallic elements connected by brazing.

 In accordance with a tenth aspect of the invention, there is provided a heat exchanger of a water heating device for the heat exchange between hot water and the combustion gas, comprising pipes (131) for allowing hot water to flow therein and a plurality of protrusions (132a) from the outer surface of the pipes (131) to encourage heat exchange between the hot water and the flue gas, wherein the plurality protrusions (132a) are discreetly arranged with a predetermined space (8) along the direction in which the combustion gas flows.

 It follows that the film of condensed water can be finely segmented by the interval 8 and, consequently, the water

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 condensate attached to the protrusions (132a) is separated from them in the segmented parts (intervals 8).

 Thus, the thickness of the film of condensed water attached to the protrusions (132a) is not increased and, as a result, an increase in the thermal resistance which otherwise would be caused by the condensed water is suppressed, thereby preventing that the efficiency of the heat exchange is reduced.

 Also, in view of the fact that the condensed water attached to the protrusions (132a) is separated at the segmented portions (intervals 5), the amount of condensed water attached to the protrusions (132a) can be reduced. In this way, the protrusions (132a), etc. can be prevented from being quickly corroded.

 In accordance with a llth aspect of the present invention, there is provided a heat exchanger of a water heating device for heat exchange between hot water and the combustion gas, comprising pipes (131) to allow hot water to flow therein and a plurality of rectangular corrugated fins projecting from the outer surface of the pipes (131) to encourage heat exchange between the hot water and the combustion gas, and in which the ribs of the fins (132) are substantially parallel to the direction of flow of the combustion gas, and in which each of the fins (132) has a plurality of slots cut out and discreetly arranged.

 The slots correspond to the intervals and the parts between the adjacent slots of the fins (132) correspond to the protrusions (132a). As in the previous aspect of the invention described above, therefore, the film thickness of the condensed water attached to the fins (132) can be more positively prevented from increasing any

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 by reducing at the same time the amount of condensed water attached to the fins (132).

 The present invention will now be more fully understood with reference to the accompanying drawings and to the preferred embodiments of the invention.

 Figure 1 includes (a) a sectional view of a heat exchanger along a line A-A in Figure 2, and (b) an enlarged sectional view of the coiled portion in Figure 2.

 Figure 2 is a front view of the heat exchanger in accordance with a first embodiment of the invention.

 Figure 3 is a side view of a heat exchanger in accordance with the first embodiment of the invention.

 Figure 4 is a top plan view of a heat exchanger in accordance with the first embodiment of the invention.

 Figure 5 is a drawing of three views of the first thermal conduction plate.

 Figure 6 is a drawing consisting of three views of the other heat conduction plate.

 FIG. 7 is a sectional view along line B-B of the thermal conduction plate shown in FIG. 5.

 FIG. 8 is a sectional view along line E-E of the thermal conduction plate shown in FIG. 5.

 Figure 9 includes (a) a sectional view along line C-C and (b) a sectional view along line D-D

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 of the thermal conduction plate shown in Figure 5.

 Figure 10 includes (a) a sectional view and (b) a front view of the fins.

 Figure 11 is a three-view drawing of a guide.

 Figure 12 includes (a) a sectional view corresponding to Figure 1 (a) and (b) an enlarged sectional view of the coiled portion of a heat exchanger in accordance with a second embodiment of the invention.

 Figure 13 includes (a) a perspective view of an external fin and (b) a front view of the brazed surface showing the shape of the fins of a heat exchanger in accordance with the second embodiment of the invention.

 Figure 14 is a perspective view of an external fin having ventilation channels of another shape.

 Figure 15 is a front view of a heat exchanger in accordance with a third embodiment of the invention.

 FIG. 16 is a side view of the heat exchanger shown in FIG. 15.

 FIG. 17 is a three-view drawing of a guide of a heat exchanger in accordance with the third embodiment of the invention.

 Figure 18 includes (a) a plan view and (b) a side view of the plate of a heat exchanger in accordance with the third embodiment of the invention.

 Figure 19 is a diagram showing the manner in which the plate is mounted.

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 Figure 20 is a perspective view of an integrated fin with a guide in accordance with a modification of the third embodiment of the invention.

 Figure 21 is a perspective view of a fin integrated with a guide in accordance with a modification of the third embodiment of the invention.

 FIG. 22 is an enlarged view showing the connection part of the two thermal conduction plates of a heat exchanger in accordance with a fourth embodiment of the invention.

 FIG. 23 is an enlarged view showing the connection part of two heat conduction plates of a heat exchanger in accordance with a first modification of the fourth embodiment of the invention.

 FIG. 24 is a side view showing a part of the coiled part of the second thermal conduction plate in accordance with the fourth embodiment of the invention.

 Figure 25 is a simplified diagram of a water heating device in accordance with a fifth embodiment of the invention.

 Figure 26 is a front view of a secondary heat exchanger in accordance with the fifth embodiment of the invention.

 Figure 27 is a partially enlarged sectional view of a secondary heat exchanger in accordance with the fifth embodiment of the invention.

 Figure 28 includes (a) a front view of a plate, (b) a side view of a plate shown in (a) and (c) an enlarged view of part A of the plate of an exchanger

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 secondary thermal in accordance with the fifth embodiment of the invention.

 Figure 29 includes (a) a front view of a plate, (b) a side view of a plate shown in (a) and (c) an enlarged view of part A of the plate of a heat exchanger secondary in accordance with the fifth embodiment of the invention.

 Figure 30 is a front view of a first spacer in accordance with the fifth embodiment of the invention.

 Figure 31 includes (a) a front view of a second spacer and (b) a side view of the second spacer shown in (b) in accordance with the fifth embodiment of the invention.

 Figure 32 is a partially enlarged sectional view of a secondary heat exchanger in accordance with the fifth embodiment of the invention.

 Figure 33 is a partially enlarged sectional view of a secondary heat exchanger in accordance with a first modification of the fifth embodiment of the invention.

 Figure 34 is a partially enlarged sectional view of a secondary heat exchanger in accordance with a second modification of the fifth embodiment of the invention.

 Figure 35 is a partially enlarged sectional view of a secondary heat exchanger in accordance with a third modification of the fifth embodiment of the invention.

 Figure 36 is a partially enlarged sectional view of a secondary heat exchanger in accordance with

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 a third modification of the fifth embodiment of the invention.

 Figure 37 is a partially enlarged sectional view of a secondary heat exchanger in accordance with a fourth modification of the fifth embodiment of the invention.

 Figure 38 is a partially enlarged sectional view of a secondary heat exchanger in accordance with a fifth modification of the fifth embodiment of the invention.

 Figure 39 is a partially enlarged sectional view of a secondary heat exchanger in accordance with a fifth modification of the fifth embodiment of the invention.

 Figure 40 is a partially enlarged sectional view of a secondary heat exchanger in accordance with a sixth modification of the fifth embodiment of the invention.

 Figure 41 includes (a) a front view and (b) a bottom view of a secondary heat exchanger in accordance with a sixth embodiment of the invention.

 Figure 42 is a partially enlarged sectional view of a secondary heat exchanger in accordance with the sixth embodiment of the invention.

 Figure 43 is a partially enlarged sectional view of a secondary heat exchanger in accordance with a modification of the sixth embodiment of the invention.

 Figure 44 includes (a) a plan view from above and (b) a front view, respectively, of an external fin

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 a heat exchanger in accordance with a seventh embodiment of the invention.

 Figure 45 is a sectional view along line B-B of Figure 41 (b).

 Figure 46 is a perspective view of an external fin in accordance with the seventh embodiment of the invention.

 Figure 47 is a perspective view of an external fin in accordance with a first modification of the seventh embodiment of the invention.

 Figure 48 is a top plan view of an external fin in accordance with a second modification of the seventh embodiment of the invention.

 Figure 49 is a front view of an external fin in accordance with a third modification of the seventh embodiment of the invention.

 Figure 50 is a top plan view of an external fin in accordance with a third modification of the seventh embodiment of the invention.

 The embodiments of the present invention will now be explained with reference to the drawings.

[First embodiment]
FIG. 2 is a front view of a heat exchanger 1, FIG. 3 is a side view of the heat exchanger 1 and FIG. 4 is a plan view from above of the heat exchanger 1.

 The heat exchanger 1 in accordance with this embodiment is used with a water heating device for heat exchange between hot water and the gas

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 combustion. As shown in Figure 3, the heat exchanger 1 is of the cup type and consists of a multilayer arrangement of a plurality of pipes 2 and fins 3 and after all the parts are assembled, it is made by soldering them together.

 The pipes 2 are each formed by combining two heat conduction plates 4 (4A, 4B) shown in FIGS. 5 and 6 and each of these includes a portion of flat pipe 2A having an internal U-shaped water path and a set of tank parts 2B communicating with the ends of the water path. The tank parts 2B have openings 2b for communication purposes (Figure 5).

 The two thermal conduction plates 4 have substantially the same shape except that a welded part 4a is arranged on the peripheral edge of the first thermal conduction plate 4A (FIG. 5). These two heat conduction plates 4, as shown in FIG. 1 (b), are assembled in such a way that the welded part 4a of the first heat conduction plate 4A is folded from the inner surface side to the side. outer surface of the second heat conduction plate 4B and the ends of the second heat conduction plate 4B are held tightly by being wound from both sides. The contact surfaces 4b of the two plates are connected by the use of a brazing material consisting of Cu or the like. The brazed (contact) parts 4b of the two thermal conduction plates 4, as shown in FIG. 1, are arranged in a different plane from the surface of the plate connected to the fins 3 at substantially the central part between the two plates.

 The tank parts in 2B have a greater thickness than the flat pipe part 2A. Flat parts

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 annulars 2c (FIGS. 7 and 9) constituting the soldering surfaces are arranged around the communication openings 2b, respectively, on the external surface of the heat conduction plates 4 forming the tank parts 2B. The sectional views (along lines BB, CC, and DD) of the thermal conduction plates 4 forming the tank parts 2B and the sectional view (along the line EE) of the thermal conduction plates 4 forming the flat pipe unit 2A are shown in Figures 7 to 9.

 A plurality of pipes 2, as shown in Figures 3 and 4, have the tank parts 2B incorporated in layers on top of each other with the flat parts 2c arranged around the communication ports 2b and coupled to each other other. It follows that the water paths of the pipes 2 communicate with each other through the communication openings 2b open to the tank parts 2B, respectively. An internal fin 5 can be inserted into each pipe 2, as shown in FIG. 1 (a), in order to increase the surface of thermal conduction.

 The pipe 2 at one end of the multilayer arrangement, as shown in FIG. 4, has a hot water inlet 6 and a hot water outlet 7 coupled to the tank parts 2B. Likewise, a reinforcing plate 8 is coupled to each of the two lateral ends of the multilayer arrangement.

 A flat space having a substantially uniform width is formed between each pair of adjacent flat pipe parts 2A each having a thickness smaller than the tank parts 2B and an external fin 3 and guides 9 (Figure 3) are arranged in each of spaces.

 The outer fin 3 is formed by bending a thin metallic material having a high thermal conductivity

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 (such as aluminum) in an irregular shape so that the combustion gas flows downward from the upper part of the heat exchanger 1 through the irregular space. The external fin 3 is connected, by the use of a brazing material, to a group Ni on the surface of the heat conduction plate 4 forming the flat pipe part 2A.

 This external fin 3 can be an ordinary corrugated fin with its irregular space formed uniformly along the direction of the flue gas flow. Alternatively, however, an offset fin can be used in which the complete fin is segmented into a plurality of unit fins 3a having a small vertical width, as shown in Figure 10 (b) and vertically adjacent fins among the unitary fins 3a are arranged in a stepped manner transversely to the flow of the combustion gas, as shown in FIG. 10 (a). Each external fin 3 in accordance with this embodiment, however, as shown in Figure 1 (a), extends further down from the portion of the lower end (the brazed portion 4b) of the corresponding pipe 2 at the combustion gas outlet orifice.

 The guides 9 are arranged on each side of the external fin 3 in the space where the external fin 3 is arranged, shown in FIG. 3 and extends from about the upper end to the lower end of the heat exchanger 1 along the direction of flow of the combustion gases in a position such as to close the left and right sides of the space having the outer fin 3 therein.

 The guides 9 are formed from a metal plate (such as an aluminum plate) having a conductivity

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 superior thermal. More precisely, as shown in FIG. 11, the guide 9 includes a U-shaped curved separation part 9A and rectangular protection parts 9B on the side at each longitudinal end. A separation part 9A is inserted between adjacent pipe parts 2A (Figure 3). The protective parts 9B are arranged at the inlet side and at the outlet side, respectively of the combustion gases (FIG. 2).

 The ends of the U-shaped curving part 9A are folded over, as shown in Figure 11 (c) to form connecting margins 9a. The connection margins 9a and the U-shaped upper parts are connected, respectively, by a brazing material of group Ni on the surface of the heat conduction plate 4 formed with the part of the flat pipe 2A of each pipe 2.

 Each protective part 9B, as shown in FIG. 4, has its flat surface arranged along the direction in which the multilayers of the pipes 2 are formed. By continuously arranging the protective parts 9B in the direction of the arrangement of the multilayers without any gap between them, the combustion gas is prevented from flowing out of the protective parts 9B.

 We will now describe the operation and the effects of this embodiment.

 Hot water flows from the hot water inlet 6 of the heat exchanger 1 to the tank parts 2B on one side of the pipes 2, from which it flows into the tank parts 2B on the on the other side via the water path formed in the flat pipe part 2A and then flows outside from

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 the hot water outlet orifice 7 coming from the other tank parts 2B.

 On the other hand, the combustion gas, as shown in FIG. 2, flows downward from the upper part of the heat exchanger 1 and, while passing through the heat exchanger 1, exchanges the heat with hot water and heat the water. In this process, the combustion gas is condensed by decreasing in temperature to at least a temperature below the dew point (say from 30 to SO'C) at the outlet of the heat exchanger. In other words, the heat exchanger 1 absorbs not only the sensible heat but also the latent heat discharged at the time of the condensation of the combustion gas to heat the hot water.

 The heat exchanger 1 in accordance with this embodiment is structured in such a way that the combustion gas passes through the space with the left and right sides thereof separated by two guides 9 and at the side outlet port of the heat exchanger (the combustion gas outlet side), the fins extend, further down, beyond the lower end portions (brazed portions 4b) of the pipes 2. With this configuration, most of the condensed water produced by condensation on the surface of the fins 3 flows down directly along the surface of the fins 3 and can descend drop by drop from the lower ends of the fins 3.

 As shown in Figure l (a), the lower end of each fin is placed below the brazed parts 4b of the pipes 2 arranged at the flue gas outlet side and each brazed part 4b and arranged in a plane different from the surface of the corresponding heat conducting plate 4. As a result, the condensed water flowing down along

<Desc / Clms Page number 25>

 from the surface of the fins 3 flows towards the brazed part 4b of the pipe 2 at the level of the combustion gas outlet orifice in a smaller quantity and drops drop by drop directly out of the heat exchanger 1 from the lower end of the fins 3. It follows that the brazing material consisting of Cu used for the brazed part 4b of the pipe 2 is prevented from being corroded by contact with condensed water, so that the corrosion resistance of the brazed part 4b can be ensured for an improved operating life of the heat exchanger 1.

 Likewise, each pipe 2 in accordance with this embodiment employs a structure wound with two heat conduction plates 4. Thus, the connection part (brazed part) of the first heat conduction plate 4A can be formed on each of the two surfaces of the second heat conduction plate 4B, and therefore a sufficient connection force can be ensured.

[Second embodiment]
In accordance with a second embodiment of the invention, each external fin 3, as shown in FIG. 13 (a) is formed by bending, in alternately opposite directions, a thin plate element of a metal ( such as stainless steel or aluminum) with high thermal conduction. The space formed by such a curvature is arranged in such a way that the combustion gas flows downwards and the external fin 3 is brazed on the surface of the heat conduction plate 4 forming the part of flat hose 2A.

 A plurality of cut and raised parts (which will be called wings 3a below) are formed, as

<Desc / Clms Page number 26>

 this is shown in Figures 12 (a) and 13 (a), only on the part of the external fin 3 closest to the combustion gas inlet (the surface where the sensible heat is mainly recovered from combustion gas). In the external fin 3 shown in FIG. 13 (a), the wings 3a are formed on the surface 3A brazed to the heat conduction plate 4. As a variant, however, the wings 3a can be formed on the lateral surfaces 3B of the external fin 3.

 The wings 3a are in the form of a cut and raised triangular part, except for one of its sides, from the surface of the fin at an angle towards the direction in which the combustion gas flows. Each pair of adjacent wings 3a formed vertically from the fin 3, as shown in Figure 13 (b), are cut and raised at different angles in the direction in which the combustion gas flows. More specifically, the upper wing (first part cut and raised) 3a shown in FIG. 13 (b) and cut and raised from the surface of the fin except for the right side of the triangle, while the lower wing 3a ( second part cut and raised) is cut and raised from the surface of the fin except for the left side of the triangle.

 We will now explain the operation and the effects of this second embodiment.

 The hot water which flows from the hot water inlet orifice 6 of the heat exchanger 1 into the tank parts 2B on one side of the pipes 2, flows through a water path formed in the flat pipe part 2A in the tank parts 2B on the other side of the pipes 2 and flowing out using the hot water outlet 7.

<Desc / Clms Page number 27>

On the other hand, the combustion gas, as shown in Figure 2, flows down from the upper part of the heat exchanger 1 and while passing through the heat exchanger 1, exchange heat with hot water and heat hot water. In the process, the combustion gas is condensed by lowering its temperature to a temperature below the dew point (say 30 to 500 C) at the outlet of the heat exchanger. In other words, the heat exchanger 1 can heat the hot water by absorbing not only the sensible heat of the combustion gas but also the latent heat discharged at the time of the condensation of the combustion gas.

 With the heat exchanger 1 in accordance with this embodiment, the wings 3a formed on the external fins 3 act to conduct the combustion gas towards the surface of the fin. Furthermore, since the wings 3a are formed at a certain angle in the direction in which the combustion gas flows, a turbulent flow of the combustion gas can be produced. More precisely, each pair of the two vertically adjacent wings 3a of the external fin 3 are cut at different angles in the direction in which the combustion gas flows and, consequently, turbulent flows in alternate and often different directions can be produced. It follows that the development of a temperature boundary layer which would otherwise have to be produced on the surface of the external fins 3 can be suppressed. Thus, the thermal conductivity is improved for improved radiation performance.

 Similarly, in view of the fact that the wings 3a are formed only on the upper part of each external fin 3 (the surface where the sensible heat is recovered from the combustion gas), the discharge of the water conden-

<Desc / Clms Page number 28>

 The salt produced by condensation of the combustion gas is not blocked by the wings 3a and the deterioration of the radiation performance which otherwise would be caused by an accumulation of the condensed water can be prevented.

 In contrast to this embodiment in which triangular wings 3 are cut and raised from the external fins 3, rectangular ventilation channels 3b can be formed alternately, as shown in FIG. 14.

[Third embodiment]
The heat exchanger 1 in accordance with a third embodiment of the invention includes guides 9 and plates 10, as described below, so that the condensed water generated by the condensation of the combustion gas cannot come into contact with the connection part of the pipe 2 and the connection part between the pipes 2 (the brazed part connected by a brazing material made of Cu).

 The guides 9, as shown in Figure 16, are arranged on the left and right sides (upper and lower sides in Figure 16) of the space where the fins 3 are arranged between the adjacent pipes 2 in the multilayer arrangement , along the direction in which the combustion gas flows (to the right of the heat exchanger 1 shown in Figure 15). The guides 9 are designed to allow the combustion gas to pass through the space with the left and right sides defined by the guides 9.

<Desc / Clms Page number 29>

 The guides 9, as shown in FIG. 17, each include a separation part 9A curved in a U shape and a protection part 9B disposed at the level of the combustion gas inlet side (left side at the 15) of each adjacent pair of flat pipe parts 2A between which the separation part 9A is inserted. This guide 9, in the same way as the fin 3, is formed of a metal plate (such as an aluminum plate or a stainless steel plate) having a high thermal conductivity and has the function of increasing the thermal conduction surface with the fins 3.

 The separation part 9A, as shown in FIG. 17 (c), is curved in the shape of a U and has connection margins 9a formed by folding the ends. The connection margins 9a and the upper part of the U-shaped part are connected, using a brazing material consisting of Ni, to the surface of the heat conduction plate 4 formed with the flat pipe part 2A of the pipe 2 .

 Each pair of the protective parts 9B has a respective flat surface arranged very precisely along the direction of the multilayer arrangement, consequently preventing the combustion gas from flowing out of the protective parts 9B.

 The plates 10 are rectangular thin plate elements (Figure 18) and, as shown in Figure 19, are arranged on each side of the connection part (brazed part) in a position such as to sandwich the part of connection where two heat conduction plates 4 forming the pipe 2 are mutually connected, the plate 10 extending further than the connection part in the direction of the flue gas flow. Each plate 10 is

<Desc / Clms Page number 30>

 disposed with its upper end contacting the lower end surface of the guide 9 without any gap between the two guides 9 and connected by the use of a brazing material consisting of Ni on the surface of the heat conduction plate 4 forming the flat pipe part 2A of pipe 2.

 We will now describe the operation and the effects of this third embodiment.

 Hot water flows into the tank parts 2B on one side of the pipes 2 from the inlet port 5 of the heat exchanger 1 and flows into the tank parts 2B on the other side of the pipes 2 through the water path formed in the flat pipe part 2A, then flows out via the outlet orifice 7 from the tank parts 2B on the other side.

 On the other hand, the combustion gas flows downward from the upper part of the heat exchanger 1 (from the left to the right in FIG. 15) and while passing through the heat exchanger 1, exchange heat with hot water and heat hot water. In the process, the combustion gas is condensed by reducing its temperature to another temperature at least below the dew point (say 30 to 50 C) at the outlet of the heat exchanger 1. In in other words, the heat exchanger 1 absorbs not only the sensible heat of the combustion gas but also the latent heat discharged at the time of the condensation of the combustion gas to heat the hot water.

 The heat exchanger 1 in accordance with this embodiment is configured so that the combustion gas passes through each space separated on its left and right sides by two guides 9 and the connection part (brazed part) of each pipe 2 arranged at

<Desc / Clms Page number 31>

 the outlet of the heat exchanger 1 and sandwiched from both sides by the plates 10. As a result, the condensed water produced by the condensation of the combustion gas is prevented from flowing over the part of pipe connection 2 where the connection part (brazed part connected using the brazing material consisting of Cu) between the pipe 2. More specifically, the condensed water, condensed on the surface of each fin 3 where each pipe 2, as shown in FIG. 19, drops drop by drop by its own weight along the surface of the plate 10. Thus, the condensed water is kept out of contact with the connection part (brazed part) of the pipe 2 .

 It follows that corrosion of the brazed part which otherwise would be caused by contact with condensed water can be prevented, thereby increasing the operating life of the heat exchanger 1.

 Likewise, the guides 9 if provided can be used as a part of the fin 3 and, therefore, can correspondingly increase the heat conduction area for improved performance.

 As a variant, a single plate 10 may be provided integrally with the fin 3 in the lowest floor, as shown in FIG. 10 (b) in which case, the plate 10 is not necessary for each of the plurality of pipes 2 constituting a multiplicity of stages and can only be disposed at the level of the combustion gas outlet orifice, making it therefore possible to prevent the number of stages of assembly to increase. In other words, since the plate 10 is not necessary at the level of the combustion gas inlet orifice, the weight is not necessarily increased by the supply of the plate 10.

<Desc / Clms Page number 32>

Although the heat exchanger 1 in accordance with this embodiment exchanges the heat between the hot water and the combustion gas, means other than hot water can be used with an equal effect.

(Modification of the third embodiment)
This modification represents an example of each guide 9 integrated into a corresponding fin 3.

 The guide 9 and the fin 3, which are arranged as separate elements in the first embodiment, can be arranged alternately in an integrated manner since the two are arranged between adjacent pipes of the multilayer arrangement. In this case, the guide 9 described in the previous embodiment (FIG. 17) can be integrated directly into the corresponding fin 3.

However, as shown in FIG. 20, for example, the lateral surfaces 3a on the two external transverse sides of the fin 3 can be used as a guide 9.

 As described above, the complete supply of the guide 9 and the fin 3 can reduce the number of parts required and facilitate the assembly work, making it therefore possible to reduce the cost of a smaller number of assembly steps.

 As shown in FIG. 21, in order to obtain turbulence by causing the combustion gas to flow in a zigzag path, each fin 3 can be formed with cut and raised parts 3b-. The lateral surfaces of the fin 3a constituting the guide 9 are not naturally provided with the cut and raised parts 3b.

<Desc / Clms Page number 33>

[Fourth embodiment] The fourth embodiment of the invention has a new functionality in the connection part (brazed part) of the pipes 2 of the heat exchanger 1.

 The two heat conduction plates 4 constituting the pipe 2, as described above, are assembled in such a way that the rolled-up part 4a of the first heat conduction plate 4A is folded on the external surface side from the internal surface side of the second heat conduction plate 4B and rolled up to hold the ends of the second heat conduction plate 4B from both sides. During the assembly of the first thermal conduction plate 4A by tuning it substantially in the shape of a U on the second thermal conduction plate 4B, a space 11 is formed between the interior surface of the curved part of the first conduction plate thermal 4A and the end surface of the second thermal conduction plate 4B (Figure 22).

 The two thermal conduction plates 4 thus assembled are connected to one another by means of two surfaces of the second thermal conduction plate 4B and of the interior surface of the first thermal conduction plate 4A. In the process, the first connection part 12 towards the inside and the second connection part 13 towards the outside of the curved part of the first heat conduction plate 4A are connected with different brazing materials. In accordance with this embodiment, the first connection part 12 is connected using a brazing material made of Cu, while the second connection part 13 is connected using a brazing material made of Ni.

<Desc / Clms Page number 34>

The operation and the effects of the fourth embodiment will now be explained.

 The hot water flows into the tank parts 2B on one side of each pipe from the inlet 6 of the heat exchanger 1 and, passing through the water path formed in the flat pipe part 2A from the particular tank parts 2B, flows into the tank parts 2B on the other side, from which it flows out through the outlet 7.

 The combustion gas, on the other hand, as shown in Figure 2, heats hot water by exchanging heat with it while flowing down through the heat exchanger 1. At the same instant, the combustion gas is condensed by lowering its temperature to a temperature below at least the dew point (say 30 to 50 C) at the level of the outlet side of the heat exchanger 1. In other words, the heat exchanger 1 can heat the hot water by absorbing not only the sensible heat of the combustion gas but also the latent heat released when the combustion gas is condensed.

 In the heat exchanger 1 in accordance with this embodiment, the first heat conduction plate 4A is wound (sewn) on the second heat conduction plate 4B and the two surfaces of the second heat conduction plate 4B thus wound (sewn) ) are coupled to the first thermal conduction plate 4A with different soldering materials, respectively. A brazing material made of Cu poses no problem, if exposed to hot water, is used for the first connection part 12 inside the curved part of the first heat conduction plate 4A, while brazing material made of Ni resistant to combustion gas corrosion can be used to

<Desc / Clms Page number 35>

 the second connection part 13 towards the outside of the same curved part. With this configuration, the brazing material made of Cu used for the first connection part 12 is not exposed to the combustion gas and, consequently, even in the case where the condensed water is produced by condensation of the combustion gas , the brazing material made of Cu is not corroded. It follows that a sufficient connection force can be maintained and that the operating time of the heat exchanger 1 can be increased.

 Likewise, since a space 11 (FIG. 22) is formed between the first connection part 12 and the second connection part 13, the brazing material consisting of Cu used for the first connection part 12 is not mixed with the brazing material consisting of Ni used for the second connection part 13. It follows that the brazing material consisting of Ni is prevented from entering the first connection part 12 and from being exposed to water hot. In this way, a highly safe heat exchanger 1 is proposed.

 In addition, in view of the fact that a sewn structure of the two heat conduction plates 4 is used, the connection part of the first heat conduction plate 4A can be formed on each of the two surfaces of the second heat conduction plate 4B . When compared to the case in which the second connection part 13 is arranged on the extension of the first connection part 12, consequently, the unused space in the heat exchanger 1 can be reduced. Thus, a heat exchanger 1 can be proposed which is not bulky and has superior anticorrosive properties.

<Desc / Clms Page number 36>

[First modification of the fourth embodiment]
Figure 23 is an enlarged view showing the connecting parts for the two heat conduction plates.

A first modification of the fourth embodiment is an example of the frame in which an inclined surface 4C is formed at the end portion of the second heat conduction plate 4B. More specifically, the end portion of the second heat conduction plate 4B is formed with the inclined surface 4C in such a way as to form a wedge-shaped space with the connecting surface of the first heat conduction plate 4A. In this case, the wedge-shaped space provides a barrier of brazing material and, therefore, different types of brazing material used on both sides of the second heat conduction plate 4B can be positively prevented from mixing the with each other. Although the inclined surface 4C is formed on the second connection part 13 in FIG. 23, it can be formed either on the first connection part 12 or on both the first and second connection part 12,13. second modification of the fourth embodiment]
A second modification of the fourth embodiment of the invention, as shown in FIG. 24, represents an example in which a hole 14 is made in the wound part 4a of the first thermal conduction plate 4A. This hole 14, as shown in FIG. 23, is formed to communicate with the space 11

<Desc / Clms Page number 37>

 formed inside the curved part of the first thermal conduction plate 4A.

 With this configuration, the air can be released from the hole 14 during the brazing of the assembled heat exchanger 1 under vacuum and, consequently, a case of connection failure is prevented in which the air is mixed in the first part connection 12 and in the second connection part 13 to cause insufficient connection force.

 Likewise, the state of brazing of the connection parts 12, 13 can be checked through the hole 14. In the case where a hermetic capacity is maintained after a vacuum is applied to the hole 14, for example, the The connection status is determined to be satisfactory.

[Fifth embodiment]
This embodiment is an application of a heat exchanger in accordance with the invention for a gas water heating device. FIG. 25 is a simplified diagram of a device for heating water with a gas 100 in accordance with this embodiment.

 In FIG. 25, a reference numeral 110 denotes a gas burner for burning the gas (fuel) and a reference numeral 120 denotes a primary heat exchanger for exchanging the heat between the hot water and the combustion gas at high temperature ( about 800 C) produced by the gas burner 110.

 A reference numeral 130 designates a secondary heat exchanger in accordance with this embodiment for exchanging heat between hot water and the reduced combustion gas from a temperature reduced to approximately 2000 C after heat exchange in the primary heat exchanger.

<Desc / Clms Page number 38>

 mayor 110. The hot water, after having been heated by the secondary heat exchanger 130, is heated by the primary heat exchanger 120.

 A reference numeral 111 designates a fan for blowing combustion air to the gas burner 110, a reference numeral 112 represents a used water pipe for discharging the condensed water generated from the combustion gas and a reference numeral 113 is an exhaust pipe to release the combustion gases after heat exchange.

 The structure of the secondary heat exchanger 130 will now be explained.

 Figure 26 is a front view of the secondary heat exchanger 130, in which the combustion gas is shown flows around the secondary heat exchanger 130 in directions perpendicular to the page in Figure 26. A reference numeral 131 designates a pipe (defining element) constituting a hot water path while simultaneously defining both a gas path (first path), in which the combustion gas (first fluid) flows and a path d hot water (second path), in which the hot water (second fluid) flows.

 In accordance with this embodiment, the combustion gas flows around the secondary heat exchanger 130 and, consequently, the gas path, as shown in FIG. 25, consists of a housing 101 for receive the secondary heat exchanger 130.

 A reference numeral 132 designates the external fins arranged between the pipes 131 to encourage the heat exchange between the combustion gas and the hot water by increasing the thermal combustion surface with the combustion gas. This embodiment employs offset fins (multi-inlet fins).

<Desc / Clms Page number 39>

 The offset fins consist of tabular segments arranged in a stepped manner.

 The pipes 131, as shown in Figure 27, each include a set of two heat conduction plates (plate elements) 133 made of stainless steel formed into a predetermined shape in a press. The particular heat conduction plates (which will be called plates hereinafter) 133 are stacked in the direction of their thickness and connected by brazing. The intermediate part of the brazed connection part 133a of the plate 133 is formed with integral arc-shaped recesses 133d on the connection surfaces 133b and 133c in opposite relation to each other at the time of formation ( press forming).

 On the other hand, an offset internal fin 134 is arranged in each pipe 131 to encourage the heat exchange between the combustion gas and the hot water by increasing the thermal combustion surface compared to the hot water.

 At each longitudinal end portion of the pipe 131, a reservoir portion 135 is formed to establish communication between a plurality of pipes 131. The reservoir portion 135 on the left side of the page in Figure 26 is intended to deliver way distributed hot water to the pipe 131 and the tank part 135 on the right side of the page in Figure 26 is intended to collect and recover the hot water after heat exchange.

 Thus, the hot water flows through the pipe 131 through the tank part 135 from the inlet port 136 placed at the upper left part of the page in FIG. 26 and leaves the heat exchanger secondary 130 from the outlet orifice 137 placed at the level of the upper right part of the page in FIG. 26.

<Desc / Clms Page number 40>

The inlet 136 and the outlet 137 are formed with a female thread for connection to a pipe.

 Figures 28 and 29 show the plate 131. A reference numeral 138 in Figure 28 designates holes for passing hot water. The plate 133 shown in FIG. 29 which is not formed with the holes 138 is used for the other end part of the secondary heat exchanger 130 which is not provided with the inlet port 136 and the port 137.

 In FIG. 27, a reference numeral 139 designates a first spacer made of stainless steel disposed at a part of the gap between the plates 133 corresponding to the interior of the pipe 131 (hot water path) and brazed to plate 133 to ensure space in the tube in the pipe 131 (hot water path). The first spacer 139, as shown in Figure 30, is of a substantially semi-circular shape.

 A reference numeral 140 designates a second spacer disposed between the adjacent pipes 131 in the gap between the plates 133 and brazed to the plate 133 and made of stainless steel to provide a predetermined space to allow the combustion gas to flow between the pipes 131 (plate 133). As shown in Figure 31 (a), the second spacer 140 is annular in shape.

 A part of each axial end surface 140a of the second spacer 140 in contact with the plate 133 is formed with an annular groove (recess) 140b.

 The brazing of the secondary heat exchanger 130 will now be explained.

 FIG. 32 is an enlarged view showing the brazed connection parts 133a and the brazed connection parts 140c between the second spacer 140 and the plates

<Desc / Clms Page number 41>

 133. Among the brazed connection part 133a, the connection surface 133c placed on the gas path side is brazed with a brazing material consisting of a nickel group, while the connection surface 133b placed inside the pipe 131 (hot water path) is brazed with a copper group brazing material.

 Similarly, in the brazed connection part 140, the connection surface 140d placed on the side of the gas path is brazed with a brazing material of the nickel group, while the connection surface 140e placed inside the pipe 131 (hot water path) is brazed with a copper group brazing material.

 In the process, the brazing material made of copper (the brazing material for the connection surfaces 133b, 140e) is designed to hold a brazing plate of copper or the like in the form of a thin film, while the material brazing of the nickel group (the brazing material for the connection surfaces 133c, 140d) is supplied by coating.

 The brazing material for brazing the internal fin 134 and the plates 133 is disposed while maintaining a brazing plate of copper or the like metal while the brazing material for brazing the external fin 132 and the pipes 131 (plates 133) is designed by coating the brazing material with a nickel group.

 In accordance with this embodiment, the melting points of the two brazing materials are fixed at substantially the same temperature (1,083 C in this embodiment) by adjusting the additive applied to the brazing material.

<Desc / Clms Page number 42>

We will now explain the operation and the effects of this embodiment.

 In accordance with this embodiment, the brazed connection parts 133a, 140c comprise a double connection structure in which the connection surfaces 133c, 140d exposed directly to the combustion gas are brazed by a brazing material of a nickel group having high corrosion resistance to sulfuric acid and nitric acid, while the connection surfaces 133b, 140e exposed directly to hot water are brazed with a brazing material of a copper group more suitable for drinking water. As a result, while providing high corrosion resistance, nickel or the like metal is not suitable for drinking water is prevented from being exposed directly to hot water.

 Despite the double connection structure being used, the brazing material consisting of molten nickel at the time of brazing is liable to flow towards the connection surfaces 133b, 140e by capillary action and mixing with the brazing material consisting of copper, can be exposed directly to hot water.

 In accordance with this embodiment, in contrast, as shown in FIG. 32, the recesses 133d, 140b are formed between the connection surfaces 133c, 140d and the connection surfaces 133b, 140e. Consequently, the brazing material made of nickel and the brazing material made of copper which can flow outside by a capillary phenomenon are blocked by the recesses 133d, 140b, respectively.

 It follows that the brazing material is prevented from reaching the connection surfaces 133b, 140e on the recesses 133d, 140b. In this way, the brazing made of nickel is positively prevented from being directly

<Desc / Clms Page number 43>

 exposed to hot water and the brazing material made of copper is positively prevented from being directly exposed to the combustion gas.

 In view of the fact that the mixed nickel and copper brazing materials remain in the recess 133d and in the groove 140b, the recess 133d and the groove 140b can be filled with brazing material in the case where the quantity of material brazing held in the recess 133d and the groove 140b is excessively large.

 The recess 133d and the groove 140b, therefore, are desirably of a size such that the solder materials collected at the time of soldering are prevented from overflowing from the recess 133d and the groove 140b and from flowing to the connection surfaces 133b, 140d.

 In accordance with this embodiment, the flow of the brazing material of the molten nickel group at the time of brazing is blocked by the recess 133d and the groove 140b. By conducting the brazing operation with the secondary heat exchanger 130 placed in an oven with the recess 133d and the groove 140b hollowed out below the connection surfaces 133b, 140d, consequently, the brazing material of nickel melted at the time brazing can be collected in the recess 133d and the groove 140b and, consequently, the brazing material made of nickel can be even more positively blocked by the recess 133d and the groove 140b.

<Desc / Clms Page number 44>

 (First modification of the fifth embodiment).

l'espaceur 140 qui est placé en aval peut être disposée par elle-même de manière telle à être évidée en dessous de la surface de raccordement 140b. In accordance with the previously mentioned embodiment, the molten brazing material is collected in the groove part 140b formed in the second spacer 140. However, the groove 140b is made in the second

the spacer 140 which is placed downstream can be arranged by itself so as to be hollowed out below the connection surface 140b.

 In view of this, in accordance with this modification, as shown in Figure 33, a recess 140g is formed in the plate 133 to positively stop the brazing material of a molten nickel group at the time of brazing.

(Second modification of the fifth embodiment)
In accordance with this modification, as shown in FIG. 34, the first and second spacers 139, 140 are not used and, at the same instant the flow of the brazing material of molten nickel at the time of brazing is obviously stopped. 133d formed in the connection phase (fixing surface) of the plate 133.

(Third modification of the fifth embodiment)
In the embodiments described above, nickel or the like metal is prevented from being directly exposed to hot water by blocking, at the level of the recess 133d, flow of the brazing material of molten nickel at the time of brazing. In accordance with this modification, and place it as shown in Figures 35, 36, obviously 133d is not used and a surface 133f

<Desc / Clms Page number 45>

 inclined with respect to at least one surface of the connection surface 133c and the connection surface 133b is formed.

 By doing this, a longer length (which will hereinafter be called the length of the interconnecting surface L) between the connecting surface 133c and the connecting surface 133b along the plate 133 can be ensured than in the case where a flat surface without irregularity is formed between the connection surface 133c and the connection surface 133b, without increasing the size of the body of the secondary heat exchanger 13 (plate 133).

 During the process, the longer the length of the interconnection surface L, the more difficult it will be for the brazing material made of molten nickel at the time of brazing to reach the connection surface (133b) (inside of the pipe 131) (hot water path).

 In accordance with this modification, therefore, nickel or the like metal is prevented from being directly exposed to hot water without increasing the size of the secondary heat exchanger 130 (plate 133).

 Likewise in the case where the connection surface 133c, the connection surface 133b and the inclined surface 133f are corrugated as shown in FIG. 36, nickel or the like metal is prevented from being directly exposed to water hot while at the same time increasing the rigidity of the plate 133 (pipe 131) without increasing the size of the secondary heat exchanger 130 (plate 133).

 (fourth modification of the fifth embodiment)

<Desc / Clms Page number 46>

This embodiment is a combination of the fifth embodiment (Figure 27) and the third modification (Figure 35). More precisely as shown in FIG. 37, the inclined surface 133F is formed with the obvious 133d.

partie de raccordement brasée 140c. En conformité avec cette modification, à l'opposé, comme cela est représenté aux figures 38 et 39, une pluralité d'évidemment 133d et rainures 140b sont formés sur chaque partie des parties de raccordement brasées 133 et de la partie de raccordement brasée 140c. It follows that nickel or the like metal is positively prevented from being directly exposed to hot water. 3 (fifth modification of the fifth embodiment)
In the embodiments described above, the recess 133d and the groove 140b are formed, one of each in the brazed connection part 133a and in the

brazed connection part 140c. In accordance with this modification, in contrast, as shown in Figures 38 and 39, a plurality of obviously 133d and grooves 140b are formed on each part of the brazed connection parts 133 and of the brazed connection part 140c.

(sixth modification of the fifth embodiment)
In accordance with this modification, as shown in FIG. 40, obviously 133d is coated with an anti-flow agent (consisting of titanium oxide in this modification) before brazing.

 At the parts coated with the titanium oxide anti-flow agent, the titanium oxide cannot be reduced to a temperature other than more than 1200 ° C. under high vacuum. In the case where the brazing operation is carried out at a temperature of 1083 ° C. for example, the titanium oxide is not reduced and, consequently, the parts coated with the anti-flow agent cannot be wetted, making it possible to prevent more positively than

<Desc / Clms Page number 47>

 the first brazing material and the second brazing material mix with each other.

 We will now explain the operation and the effects of this embodiment.

 Even a slight damage to the plate 133 (especially at the part closest to the water path than obviously 133d) causes a phenomenon of capillarity, with the effect that the brazing material consisting of molten nickel at the time of brazing is likely to be drawn into the waterway.

 In accordance with this modification, on the contrary, an anti-flow agent is placed in the recess 133d and consequently, the wettability of the recess 133d is lower than that of the parts remaining at the time of brazing, consequently preventing the obviously 133d from being wet.

 It follows that even if the plate 133 is damaged, the brazing material consisting of molten nickel at the time of brazing is prevented from being drawn into the water path by the capillary phenomenon caused by the damage.

 In this way, nickel or another metal not suitable for drinking water can be positively preventing it from being exposed directly to hot water at the same time ensuring effective anti-corrosiveness.

 Figure 40 shows an example in which the anti-flow agent is deposited (disposed in the recess 133).

Nevertheless, the anti-flow agent can, of course, be deposited (disposed) also in the groove 140b.

 The anti-flow agent (anti-wetting agent to prevent the obvious 133d from getting wet) is not limited to titanium oxide.

<Desc / Clms Page number 48>

 In the embodiments described above, the secondary heat exchanger 130 is used for the present invention. The invention is not however limited to such a secondary heat exchanger but is also applicable to the primary heat exchanger 120 or to the integrated heat exchanger including the primary heat exchanger 120 and the secondary heat exchanger 130 combined.

(Sixth embodiment)
The pipe 131 of the secondary heat exchanger 130, as shown in FIG. 42, consists of a set of two heat conduction plates (plate element) 133 made of stainless steel formed in a press in a pre-formed form. determined, the thermal conduction plates 133 (which will hereinafter be called plates 133) being arranged in a layer in the direction of their thickness (unilaterally in FIG. 41) then being subsequently connected by soldering and welded.

 More specifically, the part 141 (which will hereinafter be called the brazed connection part 141) for establishing communications between the interior of the adjacent pipes 131 of the plates 133 is placed inside the plate 133 (secondary heat exchanger 130) and is therefore very difficult to weld. Therefore, the brazed connection part 141 is brazed by a brazing material made up of the copper group and the external peripheral part 142 of the plate 133 (pipe 131) is connected by welding.

 On the other hand, protuberances 143 plastically deformed in a press, so as to form part of the plate 133 (pipe 131) protrudes towards the outside of the pipe 131, as shown in FIG. 41, are formed upstream of the brazed connection part 141 in the di-

<Desc / Clms Page number 49>

 rection of the flue gas flow and the front ends of the adjacent protrusions 143 are mutually coupled by a nickel brazing material in this embodiment having corrosion resistance is lifted.

 During the process, the protrusions 43 are formed in an arc shape to form a stop wall upstream of the annular brazed connecting portion 141 in the direction of flow of the combustion gas and consequently prevent the combustion gas to contact the brazed connection part 141 directly as shown in Figure 41 (b).

 As shown in Fig. 41 (a), on the other hand, a part of the tank 135 for establishing communication between a plurality of pipes 131 is formed at the two longitudinal end parts of the pipe 131. The tank part 135 on the left side of the page in Figure 41 (a) is intended to deliver distributed hot water to each pipe 131 and the tank portion 135 for the right side of the page in Figure 41 (a) is intended to collect and recover hot water after heat exchange.

 It follows that the hot water flows in the pipe 131 through the tank part 135 from the inlet port 136 placed at the level of the upper left part of the page in FIG. 41 (a) and leaves of the secondary heat exchanger 130 from the outlet orifice 137 placed at the level of the upper right part of the page in FIG. 41 (a).

 Likewise, as shown in FIG. 42, an external fin 132 of the offset type is arranged on the outside of each pipe 131 to encourage the heat exchange between the conduction gas and the hot water in

<Desc / Clms Page number 50>

 increasing the thermal combustion surface with hot water. The external fin 132 and the plate 133 hold a thin brazing plate made of copper or similar metal between it and a brazing material of the nickel group is deposited on the front ends of the protrusions 143 to connect them.

 With an embodiment, the melting point of the copper brazing material is fixed insensibly at the same temperature (1083 Oc in this embodiment) as the melting point of the nickel brazing material by adjusting the additive applied to the soldering material, so that the soldering operation is completed in one step.

 We will now describe the details of this embodiment.

 In accordance with this embodiment, a protuberance 143 constituting a stop wall to prevent the combustion gases from contacting the brazed connection part 141 is directly formed upstream of the brazed connection part 141 in the gas flow combustion. Consequently, the condensed water which causes corrosion of the brazed connection part 141 is prevented from being fixed to the brazed connection part 141.

 Thus, the brazed connection part 141 can be connected by brazing with a copper group brazing material more suitable for drinking water and, therefore, a secondary heat exchanger 130 connected by brazing to a metal element can be obtained which has a high corrosion resistance.

 In accordance with this embodiment and on the other hand, the front ends of the protrusions 143 will be connected by brazing with a brazing material of the nickel type. However in view of the fact that the brazing material

<Desc / Clms Page number 51>

 is disposed outside the pipe 131 with the plate 133 between them, the brazing material consisting of nickel and hot water are kept out of direct contact with each other.

 Similarly in accordance with this embodiment, the front ends of the adjacent protrusions 143 are connected by brazing. In the case of the front ends of the protrusions 143 are fixed to each other firmly by analogous mechanical means, however, the soldering of the protrusions 143 can be carried out without them.

(Modification of the sixth embodiment)
In the embodiments described above, two plates 133 are connected to each other to constitute a single pipe 131. In accordance with this modification, moreover, as shown in FIG. 43, a single plate 133 is curved and its part opposite to the curved part 144 is brazed. At the same instant the curved part 144 is placed downstream of the brazed connection parts 141, 142 in the flow of the combustion gas.

 The part opposite to the curved part 144 indicates a part upstream of a curved part 144 in the flowing gas flow and, in this modification, "the brazed connection part distant from the curved part 144 "which includes the brazed connection part 141 and the external peripheral part 142 of the plate 133 (pipe 131) constituting the part 142 upstream in the flow of the combustion gas.

 We will now describe the details of this embodiment.

 Condensed water (sulfuric acid or nitric acid which corrodes the copper brazing material as described

<Desc / Clms Page number 52>

 in "description of the related art" is generated by a decrease in the temperature of the combustion gas. At the level of the part of the secondary exchanger 13 very upstream of the flow of the combustion gas, consequently, the condensed water generated in a smaller quantity and more condensed water is likely to appear downstream.

 As in this modification, therefore, the supply of the curved part 144 having no brazed connection part downstream in the flue gas flow and the supply of the brazed connection parts 141,142 on the other side (side upstream) does not pose a corrosion problem. It is thus possible to propose a secondary heat exchanger 130 having a high corrosion resistance and comprising metallic elements connected by brazing.

 In accordance with this modification, as in the embodiments described above, the front ends of the protrusions 143 are brazed with a brazing material of the nickel type. Since less condensed water is generated upstream in the flue gas flow, however, the front ends of the protrusions 143 can be brazed with copper brazing material or the protrusions 143 (barrier wall) can perform without this one.

 The present invention is not limited to these embodiments for which the secondary heat exchanger 130 is used but is applicable with an effect equal to the primary heat exchanger 120 or to a combination of the primary heat exchanger 120 and the secondary heat exchanger 130 integrated with one another.

* (Seventh embodiment)

<Desc / Clms Page number 53>

 The seventh embodiment of the invention relates to fins (an external fin 132 and an internal fin 134) or, in particular, to an external fin 132.

 In accordance with this embodiment, an external fin of the offset type is used as the external fin 132 arranged between the pipes 131 of the secondary heat exchanger 130 to encourage the heat exchange between the combustion gas and the hot water by increasing the thermal combustion surface for the combustion gas.

 The offset fin, as shown in Figure 44, includes tabular segments (protrusions) 132 arranged offset and stepped. It follows that a multiplicity of segments 132a protrude from the external surface of the pipes 131 and are arranged in separate form at a predetermined interval 0 along which the combustion gas flows, as shown in Figure 44 (a).

 Each pipe 131, as shown in Figure 45, includes a set of two heat conduction plates (plate elements) 133 made of stainless steel formed in a press in a predetermined shape, and arranged in layers along their thickness (laterally compared to the figure on page 44) followed, then are connected by welding and soldering thereafter. In accordance with this embodiment, an offset fin (internal fin 134) is also arranged for each pipe 131.

 Hot water, as shown in Figure 25, flows into the secondary heat exchanger 130 from the left side of the page in Figure 25 or after being delivered in a distributed manner to a plurality of pipes 131 exits of the secondary heat exchanger 130

<Desc / Clms Page number 54>

 then is collected and retrieved on the right side of the page in Figure 25.

 We will now describe the details of this embodiment.

 In accordance with this embodiment, a plurality of segments 132a are arranged separately at predetermined intervals Ö in a direction of flow of the combustion gas and, as a result, the film of condensed water can be finely divided by the intervals 8. It follows that the condensed water fixed to the external fin 132 (segment 132a) descends by drop (and is separated) from the external fin 132 at segmented points (intervals) without extending over the entire external fin 132.

 Thus, the thickness of the film of condensed water attached to the outer fin 132 (segments 132a) is prevented from increasing and, as a result, an increase in the heat resistance due to the condensed water is suppressed making this makes it possible to prevent deterioration of the efficiency of the heat exchange (Figure 46).

 On the other hand, the condensed water attached to the external fin 132 (segments 132a) drops by drop (is separated) from the external fin 132 at the segmented points (intervals) without spreading over the external fin whole 132 and therefore the amount of condensed water attached to the external fin 132 (segments 132a) can be reduced, making it possible to prevent the external fin 132 (segments 132a) from being rapidly corroded .

 (First modification of the seventh embodiment)

<Desc / Clms Page number 55>

 In accordance with the embodiments described above, among the multiplicity of segments 132a, the adjacent segments 132a along the direction of flow of the combustion gas are arranged in parallel with the direction of the combustion gas. In accordance with this opposite modification, as shown in FIG. 47, among the multiplicity of segments 132a, the adjacent segments 132a along the direction of flow of the combustion gas are moved in the directions orthogonal to the direction of flow of the combustion gas.

 As a result, among the adjacent segments in the direction of the flue gas flow, the condensed water descended in (separate) drops from the segments 132a placed upstream in the flue gas flow prevented re-attach to segments 132a located downstream in the flue gas flow (Figure 47).

 Thus, the thickness of the film of condensed water fixed to the external fin 132 (segments 132a) is more positively prevented from being increased while at the same time, the quantity of condensed water is fixed to the fin. external 132 (segments 132a) is reduced. It is therefore possible to prevent the efficiency of the heat exchange from being adversely affected, while at the same time positively preventing early corrosion of the external fin 132 (segments 132a).

(Second modification of the seventh embodiment)
In the embodiments described above, the combustion gas is caused to flow in a direction orthogonal to the length of the pipes 131. The present invention is not, however, limited to such a configuration.

<Desc / Clms Page number 56>

 ration and the combustion gas can be caused to flow in the direction parallel to the length of the pipe 131.

 In this case, the direction of the segments 132a (the direction parallel to the surface of the segments) can be positioned parallel to the direction of the flow of the combustion gas, as shown in FIG. 48.

(Third modification of the seventh embodiment)
In the second modification described above, an external fin 132 of the offset type is used. In place of the offset fin shown in Figure 48, however, the present modification employs a rectangular corrugated fin as the outer fin 132, as shown in Figure 49.

 The direction of the fins is a top line 32b of the rectangular corrugated outer fin 132, as shown in FIG. 50 is positioned substantially parallel to the direction of the flow of combustion gas and a plurality of partially cut slots 132c are arranged. spaced.

 It follows that the slots 132c correspond to the intervals 8 and that the parts of the external fins 132 between the adjacent slots among the slots 132c correspond to the segments 132a (the protuberances described in the seventh previous embodiment). Thus, the thickness of the film of condensed water fixed to an external fin 132 can be positively prevented from increasing while at the same time the amount of condensed water fixed to the external fin 132 is reduced.

 In the embodiments described above, an offset fin is used like an external fin 132.

The present invention, however, is not limited to a

<Desc / Clms Page number 57>

 such a configuration and ventilation channels or the like, for example, can be formed in the corrugated fin or a branch-shaped fin can be arranged as a variant.

 In the hot water supply unit in accordance with the embodiments described above, the heat exchanger for changing the heat between the hot water and the combustion gas can be one of two types, the exchanger primary heat exchanger 120 and secondary heat exchanger 130. The primary heat exchanger 120 heat exchanged with the combustion gas of a higher temperature for the secondary heat exchanger 130 and, therefore, does not produce water condensed.

 Although the embodiments set out above employ the secondary heat exchanger 130, the present invention is not limited to the secondary heat exchanger 130 but is also applicable to the primary heat exchanger 120 with an identical effect. Similarly, the invention is also applicable to a combination of the primary heat exchanger 120 and the secondary heat exchanger integrated with one another.

 In addition, the heat exchanger in accordance with this invention is not limited to a hot water supply unit but is also applicable to other similar equipment.

Claims (15)

1. Heat exchanger characterized in that it comprises a plurality of pipes (2; 131) having their peripheral parts connected by brazing having a path of fluid formed therein; and a plurality of fins (3; 132) in contact with the external surface of said pipes (2; 131) to increase the surface of thermal conduction; wherein said pipes (2; 131) have a multilayer arrangement in a plurality of stages with said fins (3; 132) held therebetween, the adjacent pipes among said pipes are assembled by brazed connection for heat exchange between the fluid flowing through the fluid path in said pipes and the combustion gas flowing downstream along the outside of said pipe; and wherein said fins (3; 132) have guide portions for discharging the condensed water generated by heat exchange between the fluid and the combustion gas through the different guide portions of said brazed portion of said pipes (2; 131 ) arranged at the outlet side of the combustion gas.  2. Heat exchanger characterized in that it comprises a plurality of pipes (2) having their peripheral parts connected by brazing having a fluid path formed therein; and a plurality of fins (3) in contact with the external surface of said pipes to increase the surface of thermal conduction; <Desc / Clms Page number 59>  wherein said pipes (2) have a multilayer arrangement in a plurality of stages with said fins (3) held therebetween, the adjacent pipes among said pipes are assembled by brazed connection for heat exchange between the fluid s' flowing through the fluid path in said pipes and the combustion gas flowing downstream along the outside of said pipe; and wherein said fins (3) extend downward further than said brazed portion (4b) of said pipes (2) disposed at the outlet side of the combustion gas.  3. Heat exchanger according to claim 2, characterized in that guides (9) are arranged on each of the two lateral sides of the space having said fins (3) disposed therein between the adjacent pipes among said pipes (2 ) along said multilayer arrangement, and; wherein the combustion gas passes through a space with its left and right sides defined by said two guides (9).  4. Heat exchanger according to claim 2 or 3, characterized in that said brazed part (4b) of said pipes forming said fluid path is connected by brazing using a brazing material of a group Cu.  5. Heat exchanger according to any one of claims 2 to 4, <Desc / Clms Page number 60>  characterized in that said fins (3) are connected by brazing using a group Ni brazing material.  6. Heat exchanger according to any one of claims 2 to 5, characterized in that said brazed part (4b) of said pipes (2) and said connection part for connecting said fins (3) on the external surface of said pipes (2) are arranged in different planes.  7. Heat exchanger characterized in that it comprises: a plurality of pipes (2) having formed therein a fluid path; and a plurality of fins (3) in contact with the external surface of said pipes (2) to increase the surface of thermal conduction; wherein said pipes (2) will have a multilayer arrangement in a plurality of stages with said fins (3) held therebetween, a high temperature gas containing water vapor flows downward along the side external of said pipes (2), a fluid of a temperature lower than said gas at high temperature is caused to flow through said fluid paths and in said pipes (2) and not only the sensible heat but the latent heat of condensation are recovered from said high temperature gas to superheat said low temperature fluid accordingly; and wherein said fins (3) include a plurality of cut and raised portions (3a) formed from the surface of said fins and protruding into the flow of said high temperature gas, said cut portions above <Desc / Clms Page number 61>  raised being arranged only on the upper side of each of said fins.  8. Heat exchanger according to claim 7, characterized in that said fins (3) are formed with the plurality of cut and raised parts (3a) only in the area from which mainly the sensible heat is recovered from the high temperature gas .  9. Heat exchanger according to claim 7 or 8, characterized in that the cut and raised parts (3a) are of triangular shape and formed at a certain angle relative to the direction of flow of said high temperature gas, and include first cut and raised portions and second cut and raised portions having different tilt directions, said first cut and raised portions and said second cut and raised portions being arranged alternately along the direction of flow of said high temperature gas.  10. Heat exchanger used with a water heating device for exchanging heat between hot water and the combustion gas, characterized in that it comprises: a plurality of pipes (131) allowing the hot water to flow through them; and a plurality of protrusions (132a) formed so as to protrude from the external surface of said pipes (131) to encourage heat exchange between the hot water and the combustion gas; <Desc / Clms Page number 62>  wherein said plurality of protrusions (132a) are disposed separately with an interval 8 in the direction of flow of said combustion gas.  11. Heat exchanger used with a water heating device according to claim 10, characterized in that the protrusions among said plurality of protrusions (132a) which are mutually adjacent in the direction of flow of the combustion gas, are offset one relative to the other in a direction orthogonal to said direction in which said combustion gas flows.  12. Heat exchanger used with a water heating device according to claim 10 or 11, characterized in that said plurality of protrusions includes segments (132a) of offset fins.  13. Heat exchanger used with a water heating device according to any one of claims 10 to 12, characterized in that said pipes (131) each include two plate elements (heat conduction plate) (133) formed in a press in a predetermined shape and arranged one on the other along their thickness direction.  14. Heat exchanger used with a water heating device to exchange heat between hot water and the combustion gas, characterized in that it comprises: a plurality of pipes (131) through which the hot water flows; and <Desc / Clms Page number 63>  a plurality of rectangular fins (132) disposed on said pipes (131) so as to project beyond the outer surface of said pipes (131) to encourage heat exchange between said hot water and said combustion gas; wherein the direction of the ribs being an apex line of said fins (132) is substantially parallel to the direction in which said combustion gas flows; and wherein said fins (132) include a plurality of separate slots formed by partially notching said fins.  15. Heat exchanger used with a water heating device according to any one of claims 10 to 14, structured in such a way that said combustion gas flows downwards.