JP2002098493A - Heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat exchanger, which is superior in anti-corrosive property and manufactured by connecting metallic members through brazing. SOLUTION: Projected parts 136, forming protecting walls for preventing the direct collision of combustion gas against brazed connecting parts 134 are provided on the upstream side of the brazed connecting parts 134 in the stream of combustion gas. According to this method, the adhesion of condensed water, which causes the corrosion of the brazed connecting parts 134, can be prevented whereby the brazed connecting parts 134 can be connected through brazing employing a copper base brazing material or the like, which is more desirable for drinking water. Accordingly, the secondary heat exchanger 130, which is superior in anti-corrosive property and made of a metallic member through brazing connection can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger, and is effective when applied to a heat exchanger for a water heater for exchanging heat between combustion gas and hot water.

[0002]

2. Description of the Related Art As a heat exchanger for a water heater, for example, in the invention described in Japanese Patent Application Laid-Open No. 2000-130855, a pipe through which hot water flows is meandered to thereby provide a heat transfer area between the hot water and the combustion gas. Exchange area).

[0003]

However, the means for increasing the heat transfer area (heat exchange area) between the hot water and the combustion gas by meandering the pipes without increasing the size of the heat exchanger.
It is more difficult to increase the heat transfer area than the current situation.

[0004] Therefore, the inventors of the present invention have joined a metal member to a pipe (tube) through which hot water flows.
A prototype heat exchanger was developed to increase the heat transfer area without increasing the size of the heat exchanger, but the following new problems occurred.

That is, in the prototype, a plurality of stainless steel heat transfer plates press-formed into a predetermined shape are laminated in the thickness direction, and these heat transfer plates are brazed with a copper brazing material. Although they are brazed together,
In the part of the heat exchanger that recovers latent heat by being exposed to low-temperature combustion gas, nitrogen oxides (NOx) in the combustion gas
And condensed water in which sulfide oxide (SOx) is dissolved, the copper-based brazing material is corroded, and sufficient bonding strength (durability) cannot be secured.

To solve this problem, for example, Japanese Patent Application Laid-Open No. 9-2
It is known that brazing may be performed with a nickel-based brazing material as described in Japanese Patent No. 85888. However, according to the guidelines for water quality of drinking water set by the World Health Organization (WHO), copper is 0.5 mg / L,
Since nickel is as severe as 0.02 mg / L, it is not desirable to use a nickel-based brazing material for a joint that may be directly exposed to hot water.

[0007] In view of the above, an object of the present invention is to provide a heat exchanger which has excellent corrosion resistance and is formed by brazing and joining metal members.

[0008]

According to the present invention, in order to achieve the above object, according to the first aspect of the present invention, there is provided a brazing joint (13) obtained by brazing a metallic member (133).
Tube (131) through which the first fluid flows, having 4)
A heat exchanger for exchanging heat between the first fluid and the second fluid by flowing the second fluid around the tube (131), wherein the second fluid flows upstream from the brazing joint (134). A protective wall (136) for preventing the second fluid from colliding with the brazing joint (134) is provided on the side.

Accordingly, it is possible to prevent the condensed water which induces corrosion from adhering to the brazing joint (134), so that the brazing joint (134) is made of a brazing material more desirable for drinking water. Can be brazed.
Therefore, it is possible to obtain a heat exchanger excellent in corrosion resistance and brazed to a metal member.

[0010] According to the second aspect of the present invention, the metal plate member (133) is bent and the brazed joint (134) is brazed to the opposite side of the bent portion (133a). A tube (131) through which the fluid flows,
A heat exchanger for exchanging heat between a first fluid and a second fluid by flowing a second fluid around a tube (131), wherein a bent portion (133a) is brazed at a second fluid flow. (134) located further downstream than
On the upstream side of the second fluid flow from the brazing joint (134),
A protection wall (136) for preventing the second fluid from colliding with the brazing joint (134) is provided.

As a result, it is possible to prevent the condensed water that induces corrosion from adhering to the brazing joint (134), as in the first aspect of the present invention. It is possible to braze with a more desirable brazing material for drinking water.

The second fluid exchanges heat with the first fluid flowing through the tube (131) and flows downstream while lowering the temperature. Therefore, the second fluid is temporarily used as the combustion gas. Sometimes, there is a high possibility that condensed water that induces corrosion is accumulated on the downstream side of the second fluid flow. Therefore, as in the present invention, the downstream side of the second fluid flow is the bent portion 133a, and the opposite side (upstream side) of the brazed joint (134).
Is provided, there is no problem in corrosion resistance because the brazed joint (134) is not exposed to condensed water.

Therefore, according to the present invention, it is possible to obtain a heat exchanger excellent in corrosion resistance and brazed to a metal member.

According to the third aspect of the present invention, a part of the tube (131) is plastically deformed.
The protective wall (136) may be integrally formed with the tube (131).

According to the fourth aspect of the present invention, the first plate member is formed by bending a metal plate member and having a brazed joint portion on the opposite side to the bent portion. A heat exchanger having a tube (131) through which a fluid flows, and exchanging heat between the first fluid and the second fluid by flowing a second fluid around the tube (131). The bent portion (133a) is located downstream of the brazing joint (134).

As described above, the second fluid is a tube (1).
31) Since the heat is exchanged with the first fluid flowing in the inside to lower the temperature and flow to the downstream side, it is highly likely that the more condensed water that induces corrosion is accumulated on the downstream side.

For this reason, according to the present invention, as in the present invention, the bent portion 133a may be provided on the downstream side of the second fluid flow, and the brazing joint (134) may be provided on the opposite side (upstream side). As in the present invention, there is no problem in corrosion resistance. Therefore, according to the present invention, it is possible to obtain a heat exchanger excellent in corrosion resistance and brazed to a metal member.

In the heat exchanger for a water heater, the heat exchanger (130) according to any one of the first to fourth aspects may be a tube (13).
1) is made of metal, the drinking water flows through the tube (131), the combustion gas flows around the tube (131), and the combustion gas side of the brazing joint (134) is made of nickel. It is desirable to join with a brazing material and to join the drinking water side with a copper-based brazing material.

Incidentally, the reference numerals in parentheses of the above means are examples showing the correspondence with specific means described in the embodiments described later.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment)
FIG. 1 is a schematic diagram of a gas water heater 100 according to the present embodiment, in which a heat exchanger according to the present invention is applied to a gas water heater.

In FIG. 1, reference numeral 110 denotes a gas burner for burning gas (fuel). Reference numeral 120 denotes a primary heat exchanger for exchanging heat between high-temperature (about 800 ° C.) combustion gas generated by the gas burner 110 and hot water. .

Reference numeral 130 denotes a secondary heat exchanger according to the present embodiment for performing heat exchange between the combustion gas whose temperature has been reduced (to about 200 ° C.) and hot water after completing the heat exchange in the primary heat exchanger 110; The hot water is heated in the secondary heat exchanger 130 and then reheated in the primary heat exchanger 120.

Reference numeral 111 denotes a blower for blowing combustion air to the gas burner 110, reference numeral 112 denotes a drain pipe for draining condensed water generated from the combustion gas, and reference numeral 113 denotes a combustion gas after heat exchange. It is an exhaust pipe.

Next, the structure of the secondary heat exchanger 130 will be described.

FIG. 2 (a) is a front view of the secondary heat exchanger 130, FIG. 2 (b) is a bottom view of FIG. 2 (a), and combustion gas flows in a direction perpendicular to the plane of FIG. 2 (a). Next, it flows around the heat exchanger 130.

Reference numeral 131 designates a gas passage portion (second passage portion) through which the combustion gas (second fluid) flows and a hot water supply passage (first passage portion) through which hot water (first fluid) flows. It is a tube (partition member) that constitutes a water passage.

In the present embodiment, since the combustion gas flows around the secondary heat exchanger 130, the gas passage is formed as shown in FIG.
As shown in FIG. 5, the casing 101 houses the secondary heat exchanger 130.

Outer fins 132 are provided between the tubes 131 to increase the heat transfer area with the combustion gas to promote heat exchange between the combustion gas and the hot water. In this embodiment, the outer fins are offset type. Fins (multi-entry fins) are employed.

Note that offset fins are described in the heat exchanger design handbook (published by Kogyo Tosho Co., Ltd.) and in the 19th edition.
As described in the Japanese Heat Transfer Symposium Lecture Papers, etc., plate-shaped segments are offset in a zigzag pattern.

As shown in FIG. 3, the tube 131 is made up of a pair of stainless steel heat transfer plates (plate-like members) 133 which are press-formed into a predetermined shape. (Hereinafter abbreviated as plate 133) in the thickness direction (in FIG. 3, in the horizontal direction of the paper), and then brazed and welded.

More specifically, a portion 134 of the plate 133 that communicates with the adjacent tubes 131 (hereinafter, this portion is referred to as a brazing joint 134) is formed of the plate 133 (the secondary heat exchanger 130). Since it is extremely difficult to perform the welding work located on the inner side, it is brazed with a copper-based brazing material while the plate 133 (tube 13
The outer peripheral portion 135 of 1) is joined by welding.

Then, on the upstream side of the combustion gas flow from the brazing joint 134, as shown in FIG.
Projection 1 plastically deformed by press working so that part of (tube 131) projects outside tube 131
The tip side of the adjacent protrusion 136 is joined with a brazing material having excellent corrosion resistance (in this embodiment, a nickel-based brazing material).

At this time, as shown in FIG. 2 (b), the projection 136 forms the annular brazing joint 1 so as to prevent the combustion gas from directly colliding with the brazing joint 134.
34 is formed in an arc shape so as to form a protection wall on the upstream side of the combustion gas flow.

As shown in FIG. 2A, a plurality of tubes 13 are provided at both ends in the longitudinal direction of the tube 131.
1 is formed. The tank 137 on the left side of the drawing is for distributing and supplying hot water to each tube 131, and the tank 137 on the right side of the drawing collects hot water after heat exchange. It is to be collected.

For this reason, hot water flows into the tube 131 from the inflow port 136 located on the upper left side of the paper via the tank section 137, and flows out of the outlet 13 located on the upper right side of the paper.
7 flows out of the secondary heat exchanger 130.

Also, as shown in FIG.
Inside, an offset-type inner fin 138 that increases a heat transfer area with hot water and promotes heat exchange between combustion gas and hot water is provided.

The outer fin 132, the inner fin 138, and the plate 133 are provided with a brazing material by sandwiching a brazing plate of a thin copper-based metal between them, and the tip of the projection 136 is made of nickel. The brazing material is disposed by application of the brazing material and brazed.

In this embodiment, the melting point of the copper-based brazing material and the melting point of the nickel-based brazing material are substantially equal to each other by adjusting the additive to be added to the brazing material (in this embodiment, 1083 ° C.). ), Brazing is performed in a single brazing process.

Next, the features of this embodiment will be described.

According to this embodiment, the brazing joint 13
4 is provided on the upstream side of the combustion gas flow with a projection 136 serving as a protective wall for preventing the combustion gas from directly colliding with the brazing joint 134.
4 can be prevented from adhering condensed water that induces corrosion.

Therefore, the brazing joint 134 can be brazed to drinking water with a more desirable copper-based brazing material or the like, so that the metal member is excellent in corrosion resistance and brazed. The joined secondary heat exchanger 130 can be obtained.

In this embodiment, the tip end of the projection 136 is brazed and joined with a nickel-based brazing material.
Since it is disposed outside of the base, the nickel-based brazing material and hot water do not come into direct contact with each other.

In this embodiment, the adjacent projections 1
Although the distal ends of the protrusions 136 are joined by brazing, when the distal ends of the adjacent protrusions 136 are sufficiently adhered to each other due to a mechanical structure or the like, the brazing at the protrusions 136 may be omitted. .

(Second Embodiment) In the above-described embodiment, 2
Although one tube 13 is formed by joining the plates 133, in the present embodiment, as shown in FIG. 4, one plate 133 is bent and the bent portion 13 is formed.
3a is joined by brazing, and the bent portion 133a is joined to the brazed joint 13 in the combustion gas flow.
4, 133b.

Here, the side opposite to the bent portion 133a means the upstream side of the flow of the combustion gas from the bent portion 133a, and in the present embodiment, the brazed joint portion 134 and the plate 133 (tube 131). A portion 133b on the upstream side of the combustion gas flow in the outer peripheral portion 135 of the above corresponds to a "brazing joint portion on the opposite side to the bent portion 133a".

Next, the features of this embodiment will be described.

Condensed water (sulfuric acid and nitric acid), which causes corrosion of the copper brazing material, is generated due to a decrease in the temperature of the combustion gas as described in the section of “Problems to be Solved by the Invention”.
In the portion of the secondary heat exchanger 130 on the upstream side of the combustion gas flow, the amount of generated condensed water is small, and it is highly likely that more condensed water is accumulated toward the downstream side.

Therefore, as in the present embodiment, the bent portion 1 having no brazing joint on the downstream side of the combustion gas flow.
33a, and the other side (upstream side) of the brazing joint 1
Even if 34 and 133b are provided, there is no problem in corrosion resistance.
The secondary heat exchanger 130 which is excellent in corrosion resistance and in which a metal member is brazed and joined can be obtained.

In this embodiment, as in the first embodiment, the tip end of the projection 136 is brazed with a nickel-based brazing material. Since the amount of condensed water generated is small, the protrusion 1
The tip side of 36 may be brazed with a copper brazing material, or the protrusion 136 (protection wall) may be eliminated.

(Other Embodiments) In the above embodiment, the present invention is applied to the secondary heat exchanger 130, but the present invention is not limited to this, and the primary heat exchanger 120
Also, the present invention can be applied to a heat exchanger or the like in which the primary heat exchanger 120 and the secondary heat exchanger 130 are integrated.

The heat exchanger according to the present invention is not limited to a water heater, but can be applied to other heat exchangers.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a water heater according to a first embodiment of the present invention.

FIG. 2A is a front view of a secondary heat exchanger according to the first embodiment of the present invention, and FIG. 2B is a bottom view of FIG.

FIG. 3 is a partially enlarged sectional view of the secondary heat exchanger according to the first embodiment of the present invention.

FIG. 4 is a partially enlarged sectional view of a secondary heat exchanger according to a second embodiment of the present invention.

[Explanation of symbols]

131: tube, 133: heat transfer plate, 134: brazing joint, 136: protrusion (protection wall).

Claims (5)

[Claims] 1. A tube (131) through which a first fluid flows and having a brazing joint (134) formed by brazing a metal member (133).
1) A heat exchanger for exchanging heat between a first fluid and a second fluid by flowing a second fluid around the heat exchanger, wherein the brazed joint (134) is provided on the upstream side of the second fluid flow. A second fluid is connected to the braze joint (134).
A heat exchanger, comprising a protective wall (136) for preventing collision with the heat exchanger. 2. A metal plate member (133) is bent,
A tube (131) through which a first fluid flows has a brazed joint (134) brazed to the opposite side to the bent portion (133a), and a second fluid is supplied around the tube (131). A heat exchanger for exchanging heat between a first fluid and a second fluid by flowing the fluid, wherein the bent portion (133a) is located downstream of the brazed joint (134) in the second fluid flow. Further, a protection wall (136) for preventing the second fluid from colliding with the brazing joint (134) is provided on the upstream side of the second fluid flow from the brazing joint (134). A heat exchanger. 3. The protective wall according to claim 1, wherein the protective wall is formed integrally with the tube by plastically deforming a part of the tube. Heat exchanger. 4. A metal plate member (133) is bent,
A tube (131) through which a first fluid flows, having a brazed joint (134) brazed to the opposite side of the bent portion (133a);
By flowing the second fluid around the first fluid and the second fluid,
A heat exchanger for exchanging heat with a fluid, wherein the bent portion (133a) is located downstream of the brazing joint (134) in the second fluid flow. vessel. 5. The heat exchanger (130) according to any one of claims 1 to 4, wherein the tube (131) is made of metal, and drinking water flows through the tube (131). Combustion gas is circulated around the tube (131). Further, of the brazing joint (134), the combustion gas side is joined with a nickel-based brazing material, and the drinking water side with a copper-based brazing material. A heat exchanger for a water heater characterized by being joined.