JP7660895B2 - Heat exchangers and water heaters - Google Patents

Description

The present invention relates to a heat exchanger and a water heater.

Conventionally, a primary heat exchanger described in JP 2020-169744 A (Patent Document 1 below) is known as a heat exchanger used in a water heater. This primary heat exchanger is made of stainless steel and includes a rectangular cylindrical inner casing through which the combustion exhaust gas from the burner passes, and multiple heat transfer tubes that penetrate the right and left sides of the inner casing. A right header and a left header that connect the ends of the multiple heat transfer tubes are attached to the right and left sides of the inner casing. In other words, the heated water flowing in from the multiple heat transfer tubes is merged in the right header and the left header.

In the above primary heat exchanger, the right and left headers are formed with holes that penetrate in the left-right direction and are oval-shaped extending in the front-rear direction. Heated water does not flow into the holes, and the flow path of the heated water is separated into two, upper and lower, by the holes. By forming the holes, the area (area when viewed from the side) in the right and left headers where the water pressure of the heated water is applied is reduced, and damage to the right and left headers due to the impact of the water hammer can be suppressed.

JP 2020-169744 A

In the above configuration, the side surface of the middle casing disposed inside the hole is not in contact with the right header and the left header, and is a non-contact portion exposed to the outside. When this non-contact portion is heated by the combustion exhaust gas passing through the middle casing, the heat of the non-contact portion is transferred to a certain extent parallel to the side surface. However, since the primary heat exchanger uses stainless steel, which has poorer thermal conductivity than copper, etc., as its material, the non-contact portion may have areas where heat transfer is insufficient. In this case, the non-contact portion may have areas with low and high temperatures in a mottled pattern, and cracks may occur in the non-contact portion due to the difference in thermal contraction between these areas.
In addition, since the hole is long from front to rear and has straight edges, water pressure may concentrate on these straight edges, causing damage to the right and left headers.

This disclosure was completed based on the above circumstances, and aims to provide a heat exchanger that is less likely to break, and a water heater equipped with the same.

The heat exchanger of the present disclosure is a heat exchanger comprising: a square cylindrical housing including a first wall portion and a second wall portion opposed to each other; a third wall portion and a fourth wall portion joined to one end portion and the other end portion of the first wall portion and the second wall portion, respectively; a plurality of water pipes provided at different heights in each of the third wall portion and the fourth wall portion and extending in an opposing direction in which the first wall portion and the second wall portion oppose each other; a first header fixed to the outer wall surface of the first wall portion and having a space for receiving heated water introduced from the plurality of water pipes of the fourth wall portion; and a second header fixed to the outer wall surface of the second wall portion and having a space for receiving heated water introduced from the plurality of water pipes of the third wall portion, and the second header is formed with a plurality of holes having a circular shape when viewed from the opposing direction, the hole edge of the hole of the first header is fixed to the outer wall surface of the first wall portion, the hole edge of the hole of the second header is fixed to the outer wall surface of the second wall portion, the first wall portion has a first contact portion that contacts the first header and a first non-contact portion that is arranged in the hole of the first header and is not in contact with the first header, the second wall portion has a second contact portion that contacts the second header and a second non-contact portion that is arranged in the hole of the second header and is not in contact with the second header, and the first non-contact portion and the second non-contact portion are each formed in a plurality of circles when viewed from the opposing direction.

This disclosure makes it possible to provide a heat exchanger that is less susceptible to damage, and a water heater equipped with the same.

FIG. 1 is a front view of a water heater according to an embodiment, with a front cover omitted. FIG. 2 is a front view of the water heater with the resin sheet, the controller, and the display/operation panel omitted. FIG. 3 is a perspective view of the primary heat exchanger. FIG. 4 is a right side view of the primary heat exchanger. FIG. 5 is a cross-sectional view taken along line AA of FIG. FIG. 6 is a right side view of the primary heat exchanger with the header covers of the headers removed. FIG. 7 is an explanatory diagram illustrating the configuration of the first wall portion and each header. FIG. 8 is a left side view of the primary heat exchanger. FIG. 9 is a cross-sectional view taken along line BB of FIG. FIG. 10 is a left side view of the primary heat exchanger with the header covers removed. FIG. 11 is a left side view of a primary heat exchanger according to another embodiment.

Hereinafter, embodiments of the present disclosure will be listed and illustrated.
(1) A heat exchanger according to the present disclosure is a heat exchanger comprising: a rectangular cylindrical housing including a first wall portion and a second wall portion opposed to each other; a third wall portion and a fourth wall portion joined to one end portion and the other end portion of the first wall portion and the second wall portion, respectively, through which combustion exhaust gas passes; a plurality of water pipes provided at different heights in each of the third wall portion and the fourth wall portion and extending in an opposing direction in which the first wall portion and the second wall portion oppose each other; a first header fixed to an outer wall surface of the first wall portion and having a space for receiving heated water introduced from the plurality of water pipes of the fourth wall portion; and a second header fixed to an outer wall surface of the second wall portion and having a space for receiving heated water introduced from the plurality of water pipes of the third wall portion, the first wall portion has a first contact portion in contact with the first header and a first non-contact portion arranged in the hole of the first header and not in contact with the first header, the second wall portion has a second contact portion in contact with the second header and a second non-contact portion arranged in the hole of the second header and not in contact with the second header, and the first non-contact portion and the second non-contact portion are each formed in a plurality of circles when viewed from the opposing direction.
The above-mentioned "circular shape" includes not only a perfect circle shape but also a shape that can be recognized as a substantially perfect circle shape. For example, the above-mentioned "circular shape" includes an ellipse shape whose minimum diameter is 95% of its maximum diameter.

The first and second non-contact portions formed on the first and second wall portions are circular when viewed from the opposing direction, so the linear distance from any point on the first and second non-contact portions to the first and second contact portions can be made smaller than the maximum hole diameter of the hole. This allows the heat of the first and second non-contact portions to be efficiently transferred to the first and second contact portions, respectively. This prevents heat from accumulating in the first and second non-contact portions, and prevents cracks from occurring in the first and second non-contact portions.

Furthermore, by providing a plurality of holes in each of the first and second headers, it is possible to prevent the regions in the first and second headers to which water pressure is applied (the areas when viewed from the opposing direction) from becoming excessively large, and therefore it is possible to maintain the impact resistance of the first and second headers against water hammer at the same level as in the conventional case.
Furthermore, since the holes in the first and second headers are circular and do not have straight edges, damage to the first and second headers due to water pressure concentrating on parts of the first and second headers when water passes through them can be prevented.

(2) It is preferable that the hole diameter of the hole portion is one-third or less of the height dimension of the first header and the second header.

With this configuration, the heat from the first non-contact portion and the second non-contact portion can be transferred more efficiently to the first contact portion and the second contact portion, respectively.

(3) The water heater disclosed herein is a water heater that includes a burner and the above-mentioned heat exchanger through which the combustion exhaust gas from the burner passes.

This configuration makes it possible to provide a water heater whose heat exchanger is less likely to be damaged.

<Embodiment>
Hereinafter, an embodiment will be described with reference to the drawings. In addition, in cases where a plurality of identical members are included, only some of the members may be designated by reference numerals, and the reference numerals of the other members may be omitted.

[Overall structure of the water heater]
Fig. 1 is a front view of the water heater 1 with the front cover removed. Fig. 2 shows the water heater 1 of Fig. 1 with the resin sheet 26, the controller 12, and the display operation panel 13 removed.
The water heater 1 comprises a square box-shaped outer casing 2 with an open front, and an inner body 3 housed within the outer casing 2. The inner body 3 is provided with, in order from the top, a burner 4, a primary heat exchanger 5 (an example of a heat exchanger), and a secondary heat exchanger 6, and the water heater 1 is of a downward combustion type in which the combustion exhaust gas from the burner 4 flows from above to below.

In addition, an exhaust section 7, a fan unit 8, and a gas supply unit 10 are provided inside the outer casing 2. The exhaust section 7 is provided facing upward, wrapping around from the lower part of the inner body 3 to the rear. The fan unit 8 is connected to the burner 4 on the right side of the inner body 3. The gas supply unit 10 is connected to the fan unit 8 on its lower side. The gas supply unit 10 supplies fuel gas from a gas inlet pipe 11 to the fan unit 8 via a gas governor 9. A controller 12 containing an electrical board is provided on the lower right side of the inner body 3. A display and operation panel 13 exposed from the front cover is provided in the center of the lower part of the inner body 3.

[Burner]
The burner 4 is of a full primary air type, in which a mixture of fuel gas and all the combustion air required for combustion is burned. The burner 4 has an upper casing 14 that is open at the top and bottom and has a horizontally elongated rectangular shape in a plan view with a predetermined depth in the vertical direction. The top surface of the upper casing 14 is closed by a chamber 15 that protrudes upward and to which the fan unit 8 is connected. A flame hole plate (not shown) having a plurality of flame holes formed therein is provided at the bottom surface of the upper casing 14, and the mixture can be burned on the surface (bottom surface) of the flame hole plate.
The fan unit 8 includes a fan (not shown) in a fan case 16 that is circular in a plan view. A fan motor 17 that drives and rotates the fan is provided in the upper center of the fan case 16.

[Primary heat exchanger]
The primary heat exchanger 5 is made of stainless steel. As shown in Fig. 3, the primary heat exchanger 5 includes a rectangular cylindrical inner casing 20 (one example of a housing), a plurality of fins 21, a plurality of (eight in this embodiment) heat transfer tubes 22, and a plurality of (six in this embodiment) water pipes 23. The inner casing 20 is attached to the burner 4, and the combustion exhaust gas generated by the burner 4 passes through the inner casing 20 from above to below (see Fig. 2). The heat of the combustion exhaust gas is transferred to the hot water flowing through the plurality of heat transfer tubes 22.

As shown in FIG. 1, a band-shaped resin sheet 26 with a meandering conductive pattern covering almost the entire surface is wound around the upper outer periphery of the inner casing 20, making it possible to detect leakage of combustion exhaust gas from the inner casing 20.

As shown in FIG. 3, the middle casing 20 includes a first wall portion 31 and a second wall portion 32 that face each other in the left-right direction (one example of a facing direction), and a third wall portion 33 and a fourth wall portion 34 that are joined to one end (front end) of the first wall portion 31 and the second wall portion 32 and to the other end (rear end) of the first wall portion 31 and the second wall portion 32, respectively. In this embodiment, the first wall portion 31 is the right wall portion of the middle casing 20, and the second wall portion 32 is the left wall portion of the middle casing 20. The third wall portion 33 is the front wall portion of the middle casing 20, and the fourth wall portion 34 is the rear wall portion of the middle casing 20.

6 and 7, eight lower through holes 35 are formed in a row in the front-rear direction on the lower side of the first wall portion 31. Each lower through hole 35 has an elliptical shape with its major axis extending in the up-down direction in side view. Three front through holes 36 and three rear through holes 37 are formed in a row in the up-down direction on the front and rear sides of the first wall portion 31. Each front through hole 36 and each rear through hole 37 has a circular shape in side view.
As shown in FIG. 10 , the second wall portion 32 is also provided with a lower through-hole 35 , a front through-hole 36 , and a rear through-hole 37 , similar to the first wall portion 31 .

As shown in Figs. 3, 5, and 9, the fins 21 (only some of which are shown) are arranged in parallel at a predetermined interval in the left-right direction at the lower part of the middle casing 20. The heat transfer tubes 22 are linear and extend in the left-right direction, and are arranged in a row in the front-rear direction at the lower part of the middle casing 20. The heat transfer tubes 22 penetrate each fin 21 in the left-right direction. As shown in Figs. 6 and 10, the cross-sectional shape of the heat transfer tube 22 is an ellipse with the vertical direction as the major axis direction. Inside the heat transfer tube 22, a flow rate adjustment member 22A is arranged to adjust the flow rate of hot water and to stir the hot water. As shown in Fig. 5, the right ends of the heat transfer tubes 22 are inserted into the lower through-holes 35 of the first wall portion 31. As shown in Fig. 9, the left ends of the heat transfer tubes 22 are inserted into the lower through-holes 35 of the second wall portion 32.

3, 6, and 10, the water pipes 23 are located above the heat transfer pipes 22, and are arranged in groups of three at a predetermined interval in the vertical direction on the outside of the third wall portion 33 and the fourth wall portion 34 of the middle casing 20. The cross-sectional shape of the water pipes 23 is circular. The water pipes 23 are linear and extend in the left-right direction. As shown in FIG. 6, the right ends of the water pipes 23 are inserted into the front through-hole 36 and the rear through-hole 37 of the first wall portion 31. As shown in FIG. 10, the left ends of the water pipes 23 are inserted into the front through-hole 36 and the rear through-hole 37 of the second wall portion 32.

As shown in Figs. 4 and 8, the lower header 40 is attached to the lower part of the first wall part 31 and the second wall part 32. As shown in Figs. 5, 7, and 9, the lower header 40 includes a lower header body 41 attached to the outer wall surface of the first wall part 31 or the second wall part 32, and a lower header cover body 42 that closes the opening of the lower header body 41. As shown in Figs. 5 and 7, the lower header body 41 is provided with a burring part provided on the inner edge of the lower through hole 35, and an insertion hole 43 through which the end of the heat transfer tube 22 inserted in the burring part is inserted. As shown in Figs. 6 and 10, the lower header 40 connects the left and right ends of two heat transfer tubes 22 adjacent in the front-rear direction, except for the one connected to the right end of the rearmost heat transfer tube 22. As a result, the multiple heat transfer tubes 22 are connected into one serpentine shape.

As shown in FIG. 4, the lower header 40 connected to the right end of the rearmost heat transfer tube 22 is equipped with a joint tube 45. As shown in FIG. 7, the joint tube 45 is attached to an inlet opening 44 provided in the lower header cover body 42. As shown in FIG. 1, the joint tube 45 is connected to the secondary heat exchanger 6 via the connection tube 24.

As shown in FIG. 6, the right end of the front heat transfer tube 22 is connected to the right ends of the three front water pipes 23 via the front header 50 extending vertically. As shown in FIG. 7, the front header 50 includes a front header body 51 attached to the outer wall surface of the first wall portion 31 and a front header cover 52 that closes the opening of the front header body 51. The front header body 51 includes a burring portion provided on the inner edge of the front lower through hole 35 and an insertion hole 53 through which the right end of the front heat transfer tube 22 inserted into the burring portion is inserted, and a burring portion provided on the inner edge of the front through hole 36 and an insertion hole 54 through which the right end of the water pipe 23 inserted into the burring portion is inserted.

[First Header]
As shown in FIG. 4, the first header 60 is attached to the upper part of the first wall part 31. As shown in FIG. 5 and FIG. 7, the first header 60 includes a first header body 61 attached to the outer wall surface of the first wall part 31, and a first header cover body 62 that closes the opening of the first header body 61. As shown in FIG. 6 and FIG. 7, the first header body 61 is provided with a burring part provided on the inner edge of the rear through hole 37, and an insertion hole 63 through which the right end part of the rear water pipe 23 inserted in the burring part is inserted. As shown in FIG. 4, a joint cylinder 65 is provided in the upper right part of the first header 60. As shown in FIG. 7, the joint cylinder 65 is attached to the outlet opening 64 provided in the first header cover body 62. As shown in FIG. 2, the joint cylinder 65 is connected to the hot water pipe 25.

[Second Header]
As shown in Fig. 8, a second header 70 is attached to the upper part of the second wall part 32. As shown in Fig. 9, the second header 70 includes a second header body 71 attached to the outer wall surface of the second wall part 32, and a second header cover body 72 that closes the opening of the second header body 71. As shown in Fig. 10, the second header body 71 is provided with a burring part provided on the inner edge of the front through hole 36, an insertion hole 73 through which the left end of the front water pipe 23 fitted in the burring part is inserted, a burring part provided on the inner edge of the rear through hole 37, and an insertion hole 74 through which the left end of the rear water pipe 23 fitted in the burring part is inserted. The second header 70 connects the left ends of the front and rear three water pipes 23 to each other.

Therefore, the circulation path of hot and cold water in the primary heat exchanger 5 is as follows.
First, the hot water that flows into the rearmost heat transfer tube 22 from the connecting tube 24 moves forward in a serpentine manner, passing alternately through the multiple heat transfer tubes 22 via the lower header 40. Then, the hot water that flows out of the frontmost heat transfer tube 22 flows into the front three water pipes 23 via the front header 50, moves to the left, and then flows into the rear three water pipes 23 via the second header 70 and moves to the right. The hot water that flows out of the rear three water pipes 23 flows out of the hot water outlet pipe 25 via the first header 60.

[Hole]
As shown in Figs. 4, 5, and 7, the first header 60 has a plurality of holes 66 (four in this embodiment) penetrating the first header 60 in the left-right direction. As shown in Figs. 5 and 7, the holes 66 are provided by connecting a main body side hole 66A provided in the first header main body 61 and a lid body side hole 66B provided in the first header lid body 62. As shown in Fig. 4, the holes 66 are circular in side view (viewed from the left-right direction). In the present disclosure, a circular shape does not have to be a perfect circle shape, and includes shapes that can be recognized as substantially a perfect circle shape. For example, an elliptical shape in which the minimum diameter is 95% of the maximum diameter is also included. The hole diameter of the holes 66 is one-third or less of the height dimension of the first header 60.

Providing a plurality of holes 66 in the first header 60 makes it possible to reduce the area (area when viewed from the left and right) of the first header 60 to which water pressure is applied, thereby making it possible to suppress damage to the first header 60 due to the impact of the water hammer.
Furthermore, the holes 66 of the first header 60 are isotropic circular. Therefore, compared to the case where the holes are provided in the form of elongated holes including linear edges (the configuration of Patent Document 1 described above), in this embodiment, water pressure is less likely to concentrate on a portion of the holes 66 of the first header 60 when water passes through them. Therefore, damage to the first header 60 due to changes in water pressure can be suppressed.

The holes 66 are also arranged in a row in the front-to-rear direction at the vertical center of the first header 60. This makes it difficult for the flow of hot and cold water within the first header 60 to be impeded.

As shown in FIG. 8, the second header 70 is also provided with four holes 76 that are circular in side view, similar to the first header 60. As shown in FIG. 9, the holes 76 are provided in communication with the body side holes 76A provided in the second header body 71 and the lid side holes 76B provided in the second header lid 72.

[First non-contact portion, first contact portion]
As shown in Fig. 5, the hole edge of the hole 66 of the first header 60 is fixed to the outer wall surface of the first wall 31 on the first header body 61 side. The hole 66 exposes a part of the outer wall surface of the first wall 31 to the right. That is, the first wall 31 has a first non-contact portion 67 that is disposed in the hole 66 of the first header 60 and is not in contact with the first header 60, and a first contact portion 68 that is in contact with the first header 60. As shown in Fig. 4, the first non-contact portion 67 has a circular shape in a side view (when viewed from the left-right direction), and a plurality of the first non-contact portions 67 (four in this embodiment) are formed.

In the first wall portion 31, which directly receives the heat of the combustion exhaust gas, the heat of the first contact portion 68 is transferred to the hot water in the first header 60 via the first header 60. On the other hand, the first non-contact portion 67 is separated from the hot water, unlike the first contact portion 68. Therefore, the heat of the first non-contact portion 67 is transferred to the first contact portion 68 approximately parallel to the wall surface of the first wall portion 31. In this embodiment, since the first non-contact portion 67 has a circular shape in a side view, the straight-line distance from any point of the first non-contact portion 67 to the first contact portion 68 can be made smaller than the maximum hole diameter of the hole portion 66. Therefore, by appropriately setting the hole diameter of the hole portion 66, the heat of the first non-contact portion 67 can be efficiently transferred to the first contact portion 68. Therefore, even if the material of the primary heat exchanger 5 is stainless steel, which has poorer thermal conductivity than copper and other materials, it is possible to prevent heat accumulation in the first non-contact portion 67 and prevent cracks from occurring in the first non-contact portion 67.

[Second non-contact portion, second contact portion]
As shown in Fig. 9, similar to the first header 60, the hole edge of the hole 76 of the second header 70 is fixed to the outer wall surface of the second wall portion 32. As with the first wall portion 31, the second wall portion 32 has a second non-contact portion 77 that is disposed in the hole 76 of the second header 70 and is not in contact with the second header 70, and a second contact portion 78 that is in contact with the second header 70. As shown in Fig. 8, the second wall portion 32 has four second non-contact portions 77. The second non-contact portions 77 are circular in side view.

[Secondary heat exchanger]
2, the secondary heat exchanger 6 includes a rectangular cylindrical lower casing 80 that communicates with the intermediate casing 20. Although not shown, a plurality of heat transfer plates having an uneven structure are stacked at predetermined intervals inside the lower casing 80, and an internal flow path is formed between the heat transfer plates. The internal flow path has an inlet to which the water supply pipe 81 is connected and an outlet to which the connection pipe 24 is connected.

The exhaust section 7 includes a drain receiver 82 attached to the lower surface of a lower casing 80 of the secondary heat exchanger 6, and an exhaust duct 83 erected at the rear of the drain receiver 82. The bottom of the drain receiver 82 is connected to a neutralizer 85 via a drain discharge pipe 84.
The exhaust duct 83 is made of synthetic resin and has a horizontally elongated rectangular tube shape. An upper cover 86 having a cylindrical exhaust tube portion 87 protruding from the upper surface of the outer casing 2 is joined to the opening at the upper end of the exhaust duct 83.

[Explanation of water heater operation]
In the water heater 1 configured as above, when water is passed through the appliance, the controller 12 drives the fan motor 17 at a rotation speed corresponding to the amount of combustion requested by a remote control or the like to rotate the fan. Then, the fan unit 8 draws in air in proportion to the rotation speed of the fan. At the same time, fuel gas is supplied from the gas inlet pipe 11, and after the pressure is adjusted by the gas governor 9, the gas supply unit 10 mixes the fuel gas with air through a venturi provided on the intake side of the fan unit 8 to generate an air-fuel mixture. The generated air-fuel mixture is discharged from the discharge port of the fan case 16 into the chamber 15 of the burner 4, supplied into the upper casing 14, ejected from each flame hole of the flame hole plate, and ignited by an ignition electrode (not shown) to burn.

The combustion exhaust gas from the burner 4 passes from top to bottom between the fins 21 in the inner casing 20 of the primary heat exchanger 5, exchanging heat with the hot water flowing inside the heat transfer tube 22, and sensible heat is recovered.

The combustion exhaust from the primary heat exchanger 5 passes between the heat transfer plates in the lower casing 80 of the secondary heat exchanger 6, exchanging heat with the water flowing through the internal flow paths of the heat transfer plates and recovering latent heat.

The combustion exhaust gas that passes through the lower casing 80 enters the drain receiver 82 of the exhaust section 7, moves to the rear of the drain receiver 82, rises inside the exhaust duct 83, and is discharged to the outside from the exhaust tube section 87. The drain generated in the secondary heat exchanger 6 falls into the drain receiver 82 and is discharged to the outside of the appliance via the drain discharge pipe 84 and neutralizer 85.

[Effects of the embodiment]
In this manner, in the present embodiment, the first non-contact portion 67 and the second non-contact portion 77 formed on the first wall portion 31 and the second wall portion 32 are circular in side view, so that the linear distance from any point on the first non-contact portion 67 and the second non-contact portion 77 to the first contact portion 68 and the second contact portion 78 can be made smaller than the maximum hole diameter of the hole portions 66, 76. Therefore, the heat of the first non-contact portion 67 and the second non-contact portion 77 can be efficiently transferred to the first contact portion 68 and the second contact portion 78, respectively. Therefore, accumulation of heat in the first non-contact portion 67 and the second non-contact portion 77 can be suppressed, and the occurrence of cracks in the first non-contact portion 67 and the second non-contact portion 77 can be suppressed.

Furthermore, by providing a plurality of holes 66, 76 in each of the first header 60 and the second header 70, it is possible to prevent the area (area in a side view) to which water pressure is applied in the first header 60 and the second header 70 from becoming excessively large. Therefore, it is possible to maintain the impact resistance of the first header 60 and the second header 70 against water hammer at the same level as that of the conventional header.
Furthermore, since the holes 66, 76 of the first header 60 and the second header 70 are circular and do not have straight edges, damage to the first header 60 and the second header 70 due to the water pressure concentrating on parts of the first header 60 and the second header 70 when water passes through them can be prevented.

In this embodiment, the hole diameter of the holes 66 , 76 is set to be equal to or less than one-third of the height dimension of the first header 60 and the second header 70 .
With this configuration, the heat of the first non-contact portion 67 and the second non-contact portion 77 can be more efficiently transferred to the first contact portion 68 and the second contact portion 78, respectively.

The water heater 1 of this embodiment is equipped with a burner 4 and the above-mentioned primary heat exchanger 5 through which the combustion exhaust gas of the burner 4 passes, so it is possible to provide a water heater 1 in which the primary heat exchanger 5 is less likely to be damaged.

<Other embodiments>
The present disclosure is not limited to the embodiments described above and in the drawings. For example, the features of the above or later described embodiments can be combined in any combination within a range that does not contradict. Furthermore, any feature of the above or later described embodiments can be omitted unless it is clearly stated as essential. Furthermore, the above-mentioned embodiment may be modified as follows.

In the embodiment, a configuration having two heat exchangers, a primary heat exchanger 5 and a secondary heat exchanger 6, is illustrated, but the water heater may be configured to have only a primary heat exchanger.

In the embodiment, a primary heat exchanger 5 used for hot water supply is shown as an example of a heat exchanger, but the heat exchanger may be used for other purposes, such as circulation for baths or central heating.

In the embodiment, four holes 66, 76 arranged in the front-rear direction in each header 60, 70 are illustrated, but the size, arrangement, number, etc. of the holes may be changed as appropriate.
11 , in the primary heat exchanger 105, the second header 170 may be provided with seven holes 176 of the same shape and size as in the embodiment in a staggered pattern, and the second wall portion 32 may have seven second non-contact portions 177 arranged in the holes 176 and not in contact with the second header 170. In the primary heat exchanger 105, the number of holes 176 is increased and the area of the second header 170 in a side view is reduced compared to the configuration of the embodiment, so that impact resistance to water hammer is improved.

The scope of this disclosure is not limited to the above-described embodiments, but is intended to include all modifications within the scope of the claims or within the scope equivalent to the claims.

Reference Signs List 1...water heater, 2...outer casing, 3...inner body, 4...burner, 5, 105...primary heat exchanger (heat exchanger), 6...secondary heat exchanger, 7...exhaust section, 8...fan unit, 9...gas governor, 10...gas supply unit, 11...gas introduction pipe, 12...controller, 13...display/operation panel, 14...upper casing, 15...chamber, 16...fan case, 17...fan motor 20...middle casing Casing (housing), 21...fin, 22...heat transfer tube, 22A...flow rate adjusting member, 23...water passage tube, 24...connecting tube, 25...hot water outlet tube, 26...resin sheet, 31...first wall portion, 32...second wall portion, 33...third wall portion, 34...fourth wall portion, 35...lower through hole, 36...front through hole, 37...rear through hole, 40...lower header, 41...lower header main body, 42...lower header cover, 43...insertion hole, 44... Inlet opening, 45... joint tube 50... front header, 51... front header body, 52... front header cover, 53... insertion hole, 54... insertion hole 60... first header, 61... first header body, 62... first header cover, 63... insertion hole, 64... outlet opening, 65... joint tube, 66... hole, 66A... body side hole, 66B... cover side hole, 67... first non-contact portion, 68... first contact portion 70, 17 Reference Signs List 0...second header, 71...second header body, 72...second header cover, 73...through hole, 74...through hole, 76, 176...hole, 76A...body side hole, 76B...cover side hole, 77, 177...second non-contact portion, 78...second contact portion 80...lower casing, 81...water supply pipe, 82...drain receiver, 83...exhaust duct, 84...drain discharge pipe, 85...neutralizer, 86...upper cover, 87...exhaust tube portion

Claims (3)

a rectangular cylindrical housing including a first wall portion and a second wall portion opposed to each other, and a third wall portion and a fourth wall portion joined to one end portion and the other end portion of the first wall portion and the second wall portion, respectively, through which combustion exhaust gas passes;
A plurality of water pipes are provided at different heights on each of the third wall portion and the fourth wall portion, and extend in a direction in which the first wall portion and the second wall portion face each other;
a first header fixed to an outer wall surface of the first wall portion and having a space for receiving heated water introduced from the plurality of water pipes of the fourth wall portion;
a second header fixed to an outer wall surface of the second wall portion and having a space for receiving heated water introduced from the plurality of water pipes of the third wall portion;
A heat exchanger comprising:
The first header and the second header are formed with a plurality of circular holes when viewed from the opposing direction,
a hole edge portion of the hole of the first header is fixed to an outer wall surface of the first wall portion, and a hole edge portion of the hole of the second header is fixed to an outer wall surface of the second wall portion,
the first wall portion has a first contact portion in contact with the first header and a first non-contact portion disposed in the hole of the first header and not in contact with the first header, the second wall portion has a second contact portion in contact with the second header and a second non-contact portion disposed in the hole of the second header and not in contact with the second header,
The heat exchanger includes a plurality of the first non-contact portions and a plurality of the second non-contact portions each having a circular shape when viewed from the opposing direction. The heat exchanger according to claim 1, wherein the hole diameter is one-third or less of the height dimension of the first header and the second header. A water heater comprising a burner and the heat exchanger according to claim 1 or 2, through which the combustion exhaust gas from the burner passes.

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