JP7729599B2 - Heat exchangers and water heaters - Google Patents

Description

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

A known heat exchanger for use in water heaters is the primary heat exchanger described in Japanese Patent Laid-Open Publication No. 2020-143841 (Patent Document 1 below). This primary heat exchanger is made of stainless steel and includes a rectangular cylindrical inner casing through which combustion exhaust from a burner passes downward, multiple fins, and multiple heat transfer tubes. The multiple fins are arranged at intervals in the left-right direction, which is the thickness direction, at the bottom of the inner casing. The multiple heat transfer tubes include multiple large-diameter tubes that penetrate each fin in the inner casing in the left-right direction, and multiple small-diameter tubes that are arranged above the large-diameter tubes and attached to the outer surfaces of the front and rear walls of the inner casing. The multiple small-diameter tubes are fixed at intervals in the up-down direction in recessed grooves that are recessed from the outer surfaces of the front and rear walls of the inner casing into the inner casing.

In the primary heat exchanger, the fins have protruding portions at the outer edges at both front and rear ends that extend toward the front and rear walls of the intermediate casing. The protruding portions abut against the front and rear walls directly below the lowest small-diameter pipe. This allows heat from the front and rear walls directly below the lowest small-diameter pipe to be transferred to the fins, providing some cooling.
A protrusion is formed at the upper end of the overhanging part, folded back to the left. The protrusion forms an inclined surface that is positioned inside the inner casing as it extends downward. The protrusion can guide the combustion exhaust gas that flows downward along the inner surfaces of the front and rear walls of the inner casing into the inner casing.

Japanese Patent Application Laid-Open No. 2020-143841

However, since stainless steel has poorer heat conductivity than copper and the like, in order to transfer the heat received by the fins to the heat transfer tubes, it is necessary to shorten the distance between the outer edge of the fins and the outer surface of the heat transfer tubes. Therefore, extending the outer edges of the front and rear ends of the fins toward the front and rear walls of the inner casing to provide overhangs and protrusions, as described above, is not preferable from the standpoint of heat transfer efficiency.
On the other hand, if the protruding portion is not provided in the above configuration, heat from the front and rear walls directly below the lowest small-diameter pipe cannot be transferred to the fins. Furthermore, if the protruding portion is not provided in the above configuration, the combustion exhaust gas flowing downward along the inner surfaces of the front and rear walls of the intermediate casing is not guided into the intermediate casing and remains in the space between the front and rear walls below the lowest recessed groove and the ends of the fins. This makes it more likely that heat spots will occur on the front and rear walls below the lowest recessed groove. Meanwhile, the front and rear walls above the portion where the combustion exhaust gas remains and close to the small-diameter pipes are cooled by the water flowing through the small-diameter pipes. Therefore, a large temperature difference occurs between the front and rear walls below the lowest small-diameter pipe, making it more likely that cracks will occur in the lower parts of the front and rear walls of the intermediate casing.

This disclosure was completed based on the above circumstances, and aims to provide a heat exchanger that has good heat transfer efficiency and is resistant to damage, as well as a water heater equipped with the same.

The heat exchanger disclosed herein comprises a rectangular cylindrical housing including a first wall portion and a second wall portion that face each other, and a third wall portion and a fourth wall portion that are joined to one end and the other end of the first wall portion and the second wall portion, respectively, through which combustion exhaust gas passes; a plurality of fins arranged in the opposing direction inside and at the bottom of the housing, with the opposing direction between the first wall portion and the second wall portion being the thickness direction; a plurality of heat transfer tubes that penetrate the plurality of fins in the housing in the opposing direction; and a plurality of water pipes connected to the plurality of heat transfer tubes, and further comprising a guide member fixed to the third wall portion and the fourth wall portion, and a guide member that guides the third wall portion and the The fourth wall portion has a plurality of recessed grooves recessed from the outer wall surfaces of the third wall portion and the fourth wall portion toward the inside of the housing and extending in the opposing direction, and a plurality of protrusions protruding from the inner wall surfaces of the third wall portion and the fourth wall portion toward the inside of the housing and extending in the opposing direction at positions corresponding to the recessed grooves. The plurality of water pipes are arranged above the plurality of heat transfer pipes and attached within the plurality of recessed grooves of the housing. The guide member is fixed to at least the lowest-positioned protrusion of the plurality of protrusions, and this heat exchanger guides combustion exhaust gas flowing downward along the inner wall surfaces of the third wall portion and the fourth wall portion toward the inside of the housing.

This disclosure makes it possible to provide a heat exchanger that has good heat transfer efficiency and is resistant to damage, as well as a water heater equipped with the same.

FIG. 1 is a front view of a water heater according to an embodiment, in which a front cover is omitted. FIG. 2 is a front view of the water heater with the resin sheet, controller, and 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 with the lids of the headers removed. FIG. 5 is a left side view of the primary heat exchanger with the lids of the headers removed. FIG. 6 is a cross-sectional view taken along line AA in FIG. FIG. 7 is an enlarged view of the periphery of the guide member in FIG. FIG. 8 is a perspective view of the fin with some of the repeating structures omitted. FIG. 9 is a perspective view of a plurality of fins arranged side by side in the left-right direction, with the repeated structure of the fins partially omitted. FIG. 10 is a plan view of a plurality of fins arranged side by side in the left-right direction, with the repeated structure of the fins partially omitted. FIG. 11 is a perspective view of the guide member. FIG. 12 is a view of the guide member as seen from the long side direction.

Hereinafter, embodiments of the present disclosure will be listed and exemplified.
(1) A heat exchanger of 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 and the other end of the first wall portion and the second wall portion, respectively, through which combustion exhaust passes; a plurality of fins arranged side by side in the opposing direction inside and at a lower part of the housing, with the opposing direction in which the first wall portion and the second wall portion oppose each other as a thickness direction; a plurality of heat transfer tubes penetrating the plurality of fins in the housing in the opposing direction; and a plurality of water pipes connected to the plurality of heat transfer tubes, and further comprising a guide member fixed to the third wall portion and the fourth wall portion, and a guide member fixed to the third wall portion and the front The fourth wall portion has a plurality of recessed grooves recessed from the outer wall surfaces of the third wall portion and the fourth wall portion toward the inside of the housing and extending in the opposing direction, and a plurality of protrusions protruding from the inner wall surfaces of the third wall portion and the fourth wall portion toward the inside of the housing and extending in the opposing direction at positions corresponding to the plurality of recessed grooves, the plurality of water pipes are arranged above the plurality of heat transfer pipes and are attached within the plurality of recessed grooves of the housing, and the guide member is fixed to at least the lowest-positioned protrusion of the plurality of protrusions, thereby forming a heat exchanger that guides combustion exhaust gas flowing downward along the inner wall surfaces of the third wall portion and the fourth wall portion toward the inside of the housing.

With this configuration, a guide member is fixed to the lowest-positioned convex portion, so the combustion exhaust gas flowing downward along the inner wall surfaces of the third and fourth wall portions can be guided toward the inside of the housing. This prevents the combustion exhaust gas from flowing into the space between the third and fourth wall portions below the convex portion and the ends of the multiple fins, and prevents heat spots from occurring in the third and fourth wall portions below the convex portion. This prevents cracks from occurring in the lower parts of the third and fourth wall portions.

(2) It is preferable that the guide member includes an arc portion fixed to cover the convex portion from the upper end to the lower end, and a first flat plate portion extending from the lower end of the arc portion and inclining inwardly toward the housing as it extends downward.

With this configuration, the first flat plate portion can guide the combustion exhaust gas flowing downward along the inner wall surfaces of the third wall portion and the fourth wall portion toward the inside of the housing.
In addition, the arc portion is fixed to the convex portion so as to cover the convex portion from the upper end to the lower end, and the convex portion is located in a position corresponding to the recessed groove in which the water pipe is attached, so that the heat of the combustion exhaust can be efficiently transferred to the water pipe.

(3) It is preferable that the guide member further includes a second flat plate portion extending upward from the upper end of the arc portion and fixed so as to overlap the inner wall surfaces of the third wall portion and the fourth wall portion, the first flat plate portion and the second flat plate portion having the same shape and size, and the guide member being formed symmetrically with respect to an imaginary line passing through a position midway between the first flat plate portion and the second flat plate portion and the circumferential center of the arc portion.

With this configuration, the guide member can be stably fixed to the third wall portion and the fourth wall portion by the second flat plate portion.
Furthermore, because the guide member is formed symmetrically with respect to an imaginary line passing through the midpoint between the first and second flat plate portions, even if the first and second flat plate portions are interchanged, it is possible to fix the guide member to the third and fourth wall portions and guide the combustion exhaust gas into the housing in the same way as when the first and second flat plate portions are not interchanged. Therefore, when fixing the guide member to the third and fourth wall portions, it is not necessary to pay attention to the orientation of the guide member, which improves assembly efficiency.

(4) It is preferable that the multiple fins have folded portions arranged at the upper portions of the end portions on the third wall portion side and the fourth wall portion side and folded back toward the first wall portion side or the second wall portion side, the folded portions inclining inwardly of the housing as they extend upward, and the lower end of the first flat plate portion being arranged near the upper end of the folded portions.

With this configuration, the provision of a folded portion allows the combustion exhaust gas guided into the housing by the guide member to be guided into the space between the heat transfer tube and the end of the fin on the third wall side and the end on the fourth wall side, a space through which combustion exhaust gas would normally have difficulty passing. This improves the efficiency of heat transfer to the heat transfer tube.

(5) The water heater of the present disclosure is a water heater equipped with a burner and the above-described heat exchanger.

This configuration makes it possible to provide a water heater equipped with a heat exchanger that has good heat transfer efficiency and is less likely to break.

<Embodiment>
Hereinafter, embodiments will be described with reference to the drawings. Note that, in some cases, when a plurality of identical components are used, only some of the components will be designated by reference numerals, and the reference numerals of the other components will 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 rectangular 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, from top to bottom, 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 top to bottom.

Also provided within the outer casing 2 are an exhaust section 7, a fan unit 8, and a gas supply unit 10. The exhaust section 7 is installed facing upward, wrapping around from the bottom 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 underside. 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 circuit board is installed on the lower right side of the inner body 3. A display and operation panel 13 exposed from the front cover is installed in the lower center of the inner body 3.

[Burner]
The burner 4 is an all-primary air type that burns a mixture of fuel gas and all the combustion air required for combustion. 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) with multiple flame holes formed therein is provided on the bottom surface of the upper casing 14, allowing the mixture to combust 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 plan view. A fan motor 17 that drives and rotates the fan is provided in the center of the upper side 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 (an 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 interior of the inner casing 20 from top to bottom (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 Figure 1, a strip-shaped resin sheet 26 with a serpentine conductive pattern covering almost the entire upper outer periphery of the inner casing 20 is wrapped around the upper outer periphery, making it possible to detect leakage of combustion exhaust gas from the inner casing 20.

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

As shown in Figures 3 and 6, multiple fins 21 (only some are shown) are arranged side by side at a predetermined interval in the left-right direction in the lower part of the inner casing 20. Multiple heat transfer tubes 22 are linear and extend left-right, and are arranged side by side in the front-to-back direction in the lower part of the inner casing 20. The multiple heat transfer tubes 22 penetrate each fin 21 in the left-to-right direction. As shown in Figures 4 to 6, the cross-sectional shape of the heat transfer tube 22 is elliptical with the major axis extending in the up-down direction. A flow rate adjusting member 22A is arranged inside the heat transfer tube 22 to adjust the flow rate of hot water and to agitate the hot water.

As shown in Figures 3 and 6, the multiple water pipes 23 are located above the multiple heat transfer pipes 22, and are arranged in groups of three at a predetermined interval in the vertical direction on the outer wall surfaces of the third wall portion 33 and the fourth wall portion 34 of the intermediate casing 20. The water pipes 23 are linear and extend in the horizontal direction. The cross-sectional shape of the water pipes 23 is circular.

As shown in Figures 6 and 7, the water pipes 23 are mounted in multiple recessed grooves 35 provided in the third wall portion 33 and the fourth wall portion 34. Three recessed grooves 35 are provided in each of the third wall portion 33 and the fourth wall portion 34. The recessed grooves 35 are spaced apart in the vertical direction and extend in the horizontal direction. The recessed grooves 35 in the third wall portion 33 are recessed rearward from the outer wall surface of the third wall portion 33, and the recessed grooves 35 in the fourth wall portion 34 are recessed forward from the outer wall surface of the fourth wall portion 34. In other words, the recessed grooves 35 are recessed inward of the intermediate casing 20. In the cross-sectional views of the third wall portion 33 and the fourth wall portion 34, the recessed grooves 35 correspond to the arc-shaped portions on the outer wall surfaces.

A number of protrusions 36 extend in the left-right direction on the inner wall surfaces of the third wall portion 33 and the fourth wall portion 34, which are arranged at positions corresponding to the plurality of recessed grooves 35. The protrusions 36 of the third wall portion 33 protrude rearward from the inner wall surface of the third wall portion 33, and the protrusions 36 of the fourth wall portion 34 protrude forward from the inner wall surface of the fourth wall portion 34. In other words, the protrusions 36 protrude toward the inside of the intermediate casing 20. In a cross-sectional view of the third wall portion 33 and the fourth wall portion 34, the protrusions 36 correspond to the arc-shaped portions on the inner wall surfaces.

The third wall portion 33 and the fourth wall portion 34 below the lowest protrusion 36 among the plurality of protrusions 36 are each designated as a lower wall portion 37, and the third wall portion 33 and the fourth wall portion 34 above the lowest protrusion 36 among the plurality of protrusions 36 are each designated as an upper wall portion 38. The lower wall portion 37 is positioned more inwardly of the intermediate casing 20 than the upper wall portion 38, and the spacing between the lower wall portions 37 in the front-to-rear direction is smaller than the spacing between the upper wall portions 38 in the front-to-rear direction.

As shown in Figures 3 to 5, a lower header 40 is attached to the lower part of the first wall portion 31 and the second wall portion 32. Note that in Figures 4 and 5, the lid portions of each header 40, 42, 43, and 45 are omitted to make it easier to see the connections between the heat transfer pipes 22 and water pipes 23 and each header 40, 42, 43, and 45.

As shown in Figures 4 and 5, the lower header 40 connects the left and right ends of two heat transfer tubes 22 adjacent in the front-to-rear direction. As a result, the plurality of heat transfer tubes 22 are connected into a single serpentine tube. However, the rearmost lower header 40 of the first wall portion 31 is connected only to the right end of the rearmost heat transfer tube 22. As shown in Figure 3, the rearmost lower header 40 of the first wall portion 31 is connected to a joint cylinder 41. As shown in Figure 1, the joint cylinder 41 is connected to the secondary heat exchanger 6 via the connecting pipe 24.
As shown in FIG. 4, the right end of the foremost heat transfer tube 22 is connected to the right ends of the three front water pipes 23 via a front header 42 that extends vertically.

As shown in Figures 3 and 4, a first header 43 is attached to the top of the first wall portion 31. The first header 43 is connected to the right end of the rear water pipe 23. As shown in Figure 3, a joint cylinder 44 is provided in the upper right portion of the first header 43. As shown in Figure 2, the hot water outlet pipe 25 is connected to the joint cylinder 44.
5, a second header 45 is attached to the upper part of the second wall portion 32. The second header 45 is connected to the left end of the front water pipe 23 and the left end of the rear water pipe 23. In other words, the second header 45 connects the left ends of the three front and rear water pipes 23 together.

Therefore, the flow path of hot water in the primary heat exchanger 5 is as follows.
First, 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, hot water that flows out of the frontmost heat transfer tube 22 flows into the front three water pipes 23 via the front header 42, moves to the left, and then flows into the rear three water pipes 23 via the second header 45, and moves to the right. 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 43.

[Multiple Fins]
The fins 21 are horizontally elongated plate-like members extending in the front-rear direction. As shown in FIG. 6 , eight elliptical through-holes 50 are formed penetrating the fins 21 in the left-right direction and are spaced apart in the front-rear direction. Heat transfer tubes 22 are inserted through the through-holes 50 of the fins 21. As shown in FIG. 8 , burring portions 51 protruding to the left are formed on the inner edges of the through-holes 50 of the fins 21. The fins 21 include flange-shaped heat receiving portions 52 that protrude radially outward from the edge of the through-holes 50. The heat receiving portions 52 receive heat from the combustion exhaust gas flowing from above to below within the inner casing 20 and transfer the heat to the heat transfer tubes 22 inserted through the through-holes 50, thereby heating the hot water in the heat transfer tubes 22. Two heat receiving portions 52 adjacent in the front-rear direction are connected at their lower portions by a connecting portion 53.
The fin 21 has edge portions 54 at its front end (on the third wall portion 33 side) and its rear end (on the fourth wall portion 34 side). As shown in Fig. 6, the front edge portion 54 is disposed and fixed so as to abut against the inner wall surface of the lower wall portion 37 of the third wall portion 33. The rear edge portion 54 is disposed and fixed so as to abut against the inner wall surface of the lower wall portion 37 of the fourth wall portion 34.

[Folded part]
As shown in Figure 8, two folded portions 55 are provided at the top of both front and rear ends of the fin 21, folded back toward the left (toward the second wall portion 32). The front folded portion 55 is inclined rearward as it extends upward. The rear folded portion 55 is inclined forward as it extends upward. In other words, the two folded portions 55 are provided so as to be inclined inward toward the inner casing 20 as they extend upward (see Figure 6).

When multiple fins 21 are aligned in the left-right direction inside the middle casing 20 and the heat transfer tubes 22 are inserted, the folded portions 55 of the multiple fins 21 are arranged so that they overlap each other, as shown in Figures 9 and 10. In particular, as shown in Figure 10, when fin 21A is adjacent to the right (above in the figure) of fin 21B, the tip end (lower part in the figure) of the folded portion 55 provided on fin 21A overlaps the base end (upper part in the figure) of the folded portion 55 provided on fin 21B.

[Guide member]
As shown in FIG. 6 , the primary heat exchanger 5 includes a guide member 60 inside the inner casing 20. In this embodiment, the guide member 60 is fixed to the lowest convex portion 36 among the plurality of convex portions 36. FIG. 7 is a partially enlarged view of FIG. 6 showing the periphery of the guide member 60 fixed to the third wall portion 33. As shown in FIG. 7 , the guide member 60 guides the combustion exhaust gas flowing downward along the inner wall surface of the third wall portion 33 rearward, as indicated by the dashed arrow A1. Similarly, the guide member 60 fixed to the fourth wall portion 34 guides the combustion exhaust gas forward. That is, the guide member 60 guides the combustion exhaust gas flowing downward along the inner wall surfaces of the third wall portion 33 and the fourth wall portion 34 toward the inside of the inner casing 20.

[Arc portion, first flat plate portion]
As shown in FIG. 7 , the guide member 60 includes an arc portion 61 fixed to the protrusion 36, a first flat plate portion 62 extending from the lower end of the arc portion 61, and a second flat plate portion 63 extending from the upper end of the arc portion. The arc portion 61 is disposed so as to cover the protrusion 36 from its upper end to its lower end. A recessed groove 35 is disposed in a position corresponding to the protrusion 36, and the water pipe 23 is disposed in the recessed groove 35, thereby facilitating heat transfer from the combustion exhaust gas to the hot water in the water pipe 23. The first flat plate portion 62 is inclined downward toward the interior of the inner casing 20 (rearward in FIG. 7 ). Therefore, the first flat plate portion 62 guides the combustion exhaust gas flowing downward along the inner wall surfaces of the third wall portion 33 and the fourth wall portion 34 toward the interior of the inner casing 20 (dashed arrow A1).

Unlike the present embodiment, when the guide member 60 is not provided, the combustion exhaust gas flows into and stagnates in a space S1 (see FIG. 7 ) between the lower wall portion 37 of the third wall portion 33 and the fourth wall portion 34 and the front-rear ends of the fins 21. Because the primary heat exchanger 5 is made of stainless steel, which has relatively poor thermal conductivity, the heat of the combustion exhaust gas stagnates in the space S1 is not easily transferred to the hot water in the heat transfer tubes 22 through the fins 21 and the lower wall portion 37, and heat spots are likely to occur in the lower wall portion 37. Furthermore, the side of the lower wall portion 37 closest to the lowest water pipe 23 is cooled by the water flowing through the water pipe 23, but the side of the lower wall portion 37 away from the water pipe 23 is heated by the combustion exhaust gas flowing in the space S1, resulting in a large temperature difference in the lower wall portion 37. Since the primary heat exchanger 5 is made of stainless steel, which has poor thermal conductivity, the temperature difference in the lower wall portion 37 cannot be eliminated, and cracks may occur in the lower wall portion 37 .
7 , the provision of guide member 60 makes it difficult for the combustion exhaust gas to flow into space S1, and instead the combustion exhaust gas is guided toward the inside of inner casing 20 (dashed arrow A1). This prevents the lower wall portion 37 from being heated, and prevents a large temperature difference from occurring in the lower wall portion 37. Therefore, even if the distance between the outer edges of the front and rear ends of fins 21 and heat transfer tubes 22 is reduced and gaps are formed between the fins 21 and lower wall portion 37, the generation of heat spots and cracks in the lower wall portion 37 can be suppressed.
Furthermore, since the flow of combustion exhaust gas into the space S1 is suppressed, the heat transfer efficiency can be improved accordingly.

In this embodiment, the lower end 62A of the first flat plate portion 62 is located near the upper end 55A of the folded-back portion 55. As a result, as indicated by the dashed arrow A2, the combustion exhaust gas guided into the inner side of the intermediate casing 20 by the first flat plate portion 62 can be guided into the space S2 between the edge portion 54 of the fin 21 and the heat transfer tube 22. The combustion exhaust gas does not normally pass through this space S2. This improves the efficiency of heat transfer to the heat transfer tube 22.
Furthermore, the folded portions 55 of adjacent fins 21 in the left-right direction are overlapped with each other (FIG. 10), which prevents the combustion exhaust gas guided to the space S2 from flowing between the adjacent fins 21 into the space S1.

[Second flat plate part]
The second flat plate portion 63 is fixed so as to overlap with the inner wall surfaces of the upper wall portions 38 of the third wall portion 33 and the fourth wall portion 34. The second flat plate portion 63 allows the guide member 60 to be attached to the inner casing 20 more stably.

As shown in FIG. 11 , the guide member 60 is elongated in the long-side direction D1 and divided into approximately three parts in the short-side direction D2. The central part in the short-side direction D2 is an arc-shaped part 61. A first flat plate part 62 is provided at one end of the arc-shaped part 61 in the short-side direction D2, and a second flat plate part 63 is provided at the other end of the arc-shaped part 61 in the short-side direction D2. The first flat plate part 62 and the second flat plate part 63 are flat plates of the same shape and size. The guide member 60 is formed with a plurality of slits 64 penetrating the arc-shaped part 61. The plurality of slits 64 are arranged at intervals in the long-side direction D1 of the guide member 60.
The guide member 60 is disposed so that the long side direction D1 coincides with the left-right direction, and is fixed to the inner casing 20 so that the arc portion 61 covers the protrusion 36 .

As shown in FIG. 12 , the guide member 60 is formed symmetrically with respect to an imaginary line VL that passes through the midpoint between the first flat plate portion 62 and the second flat plate portion 63 and the circumferential center of the arc portion 61. That is, the first flat plate portion 62 and the second flat plate portion 63 in the guide member 60 are structurally equivalent. As a result, when fixing the guide member 60 to the third wall portion 33 and the fourth wall portion 34, it is not necessary to distinguish between the first flat plate portion 62, which guides the combustion exhaust gas into the inner side of the inner casing 20, and the second flat plate portion 63, which is fixed to the third wall portion 33 and the fourth wall portion 34. This improves the efficiency of assembling the guide member 60 to the inner casing 20.

[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 a continuous internal flow path is formed between the heat transfer plates. The internal flow path has an inlet to which a water supply pipe 81 is connected and an outlet to which a connecting pipe 24 is connected.

The exhaust section 7 includes a drain receiver 82 attached to the underside of the 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 tubular 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 described above, when water is passed through the appliance, the controller 12 drives the fan motor 17 at a rotation speed corresponding to the combustion amount requested via a remote control or the like, causing the fan to rotate. The fan unit 8 then draws in air proportional to the fan rotation speed. At the same time, fuel gas is supplied from the gas inlet pipe 11, its pressure adjusted by the gas governor 9, and then mixed with air in the gas supply unit 10 via a venturi provided on the suction side of the fan unit 8 to generate an air-fuel mixture. The generated air-fuel mixture is discharged from the outlet of the fan case 16 into the chamber 15 of the burner 4, supplied into the upper casing 14, ejected from each flame hole in the flame hole plate, and ignited by an ignition electrode (not shown) to combust.

The combustion exhaust 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 tubes 22 and recovering sensible heat.

At this time, the guide member 60 guides the combustion exhaust gas flowing downward along the inner wall surfaces of the third wall portion 33 and the fourth wall portion 34 toward the inside of the intermediate casing 20, making it difficult for the combustion exhaust gas to flow into the space S1 between the lower wall portion 37 and the front and rear ends of the fins 21. This makes it possible to prevent cracks from occurring due to heat spots being formed in the lower wall portion 37.
In addition, heat from the combustion exhaust gas that flows into space S1 is difficult to transfer to the hot water in the heat transfer tube 22, but in this embodiment, the flow of the combustion exhaust gas into space S1 is suppressed, thereby improving the heat transfer efficiency accordingly.

The combustion exhaust from the primary heat exchanger 5 passes between the heat transfer plates within 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 through the exhaust duct 83, and is discharged to the outside from the exhaust pipe 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]
As described above, in this embodiment, the guide member 60 is fixed to the lowest-positioned convex portion 36, so that the combustion exhaust gas flowing downward along the inner wall surfaces of the third wall portion 33 and the fourth wall portion 34 can be guided toward the inside of the intermediate casing 20. This prevents the combustion exhaust gas from flowing into the space S1 between the third wall portion 33 and the fourth wall portion 34 below the convex portion 36 and the ends of the plurality of fins 21, thereby suppressing the occurrence of heat spots in the third wall portion 33 and the fourth wall portion 34 below the convex portion 36. This prevents a large temperature difference from occurring between a portion of the lower wall portion 37 close to the lowest water pipe 23 and a portion remote from the lowest water pipe 23, thereby suppressing the occurrence of cracks in the lower portions of the third wall portion 33 and the fourth wall portion 34.

In this embodiment, the first flat plate portion 62 of the guide member 60 is inclined inwardly into the middle casing 20 as it extends downward, so that the first flat plate portion 62 can guide the combustion exhaust gas flowing downward along the inner wall surfaces of the third wall portion 33 and the fourth wall portion 34 toward the inside of the middle casing 20.
In addition, the arc portion 61 is fixed to the convex portion 36 so as to cover the convex portion 36 from the upper end to the lower end, and the convex portion 36 is located in a position corresponding to the recessed groove 35 to which the water pipe 23 is attached, so that the heat of the combustion exhaust can be efficiently transferred to the water pipe 23.

In this embodiment, the guide member 60 further includes a second flat plate portion 63 extending upward from the upper end of the arc portion 61, so that the guide member 60 can be stably fixed to the third wall portion 33 and the fourth wall portion 34 by the second flat plate portion 63.
Furthermore, because the guide member 60 is formed symmetrically with respect to the imaginary line VL that passes through the midpoint between the first flat plate portion 62 and the second flat plate portion 63 and the circumferential center of the arc portion 61, even if the first flat plate portion 62 and the second flat plate portion 63 are interchanged, it is possible to fix the guide member 60 to the third wall portion 33 and the fourth wall portion 34 and to guide the combustion exhaust gas into the inner side of the intermediate casing 20 in the same way as when the first flat plate portion 62 and the second flat plate portion 63 are not interchanged. Therefore, when fixing the guide member 60 to the third wall portion 33 and the fourth wall portion 34, it is not necessary to pay attention to the orientation of the guide member 60, which improves assembly efficiency.

In this embodiment, the multiple fins 21 have folded portions 55, so the combustion exhaust gas guided toward the inside of the inner casing 20 by the guide member 60 can be guided to the space S2 between the end of the fin 21 on the third wall portion 33 side and the end on the fourth wall portion 34 side and the heat transfer tube 22, through which the combustion exhaust gas would normally have difficulty passing. This improves the efficiency of heat transfer to the heat transfer tube 22.

The water heater 1 of this embodiment is equipped with a burner 4 and the above-mentioned primary heat exchanger 5, making it possible to provide a water heater 1 equipped with a primary heat exchanger 5 that has good heat transfer efficiency and is resistant to damage.

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

In the embodiment, a configuration including two heat exchangers, a primary heat exchanger 5 and a secondary heat exchanger 6, is illustrated, but the water heater may also be configured to include 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 it may also be a heat exchanger for other purposes, such as circulation for baths or central heating.

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.

1...water heater, 2...outer casing, 3...inner body, 4...burner, 5...primary heat exchanger (heat exchanger), 6...secondary heat exchanger, 7...exhaust section, 8...fan unit, 9...gas governor, 10...gas supply unit, 11...gas inlet pipe, 12...controller, 13...display/operation panel, 14...upper casing, 15...chamber, 16...fan case, 17...fan motor, 20...middle casing (housing), 21, 21A, 21B...fins, 22...heat transfer tube, 22A...flow rate adjusting member, 23...water flow pipe, 24...connecting pipe, 25...outlet pipe, 26...resin sheet, 31...first wall portion, 32...second wall portion, 33...third wall portion, 34...fourth wall portion, 35...recessed groove, 36...convex portion, 37...lower wall portion, 38...upper wall portion, 40...lower header, 41...joint tube, 42... Front header, 43...first header, 44...joint tube, 45...second header, 50...through hole, 51...burring portion, 52...heat receiving portion, 53...connecting portion, 54...edge portion, 55...folded portion, 55A...upper end portion, 60...guide member, 61...arc portion, 62...first flat plate portion, 62A...lower end portion, 63...second flat plate portion, 64...slit 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, A1, A2...dashed arrow, D1...long side direction, D2...short side direction, S1...space between third wall portion and fourth wall portion below the convex portion and ends of multiple fins, S2...space between the end of the fin on the third wall portion side and the end of the fin on the fourth wall portion side and the heat transfer tube, VL...imaginary straight line

Claims (5)

a rectangular cylindrical housing including a first wall portion and a second wall portion facing 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 fins arranged in a thickness direction in a direction in which the first wall portion and the second wall portion face each other, the fins being arranged inside and at a lower part of the housing in the thickness direction;
a plurality of heat transfer tubes that pass through the plurality of fins in the housing in the opposing direction;
a plurality of water pipes connected to the plurality of heat transfer pipes;
A heat exchanger comprising:
further comprising a guide member fixed to the third wall portion and the fourth wall portion,
the third wall portion and the fourth wall portion have a plurality of recessed grooves recessed from outer wall surfaces of the third wall portion and the fourth wall portion inwardly of the housing and extending in the opposing direction, and a plurality of protrusions protruding from inner wall surfaces of the third wall portion and the fourth wall portion inwardly of the housing and extending in the opposing direction at positions corresponding to the plurality of recessed grooves,
the plurality of water pipes are disposed above the plurality of heat transfer pipes and are attached to the plurality of recessed grooves of the housing;
the guide member is fixed to at least the lowest-positioned convex portion among the plurality of convex portions, and guides the combustion exhaust gas flowing downward along the inner wall surfaces of the third wall portion and the fourth wall portion toward the inside of the housing ;
A heat exchanger , wherein a lower end of the guide member is located higher than an upper end of the heat transfer tube . The heat exchanger described in claim 1, wherein the guide member comprises an arc portion fixed to cover the convex portion from its upper end to its lower end, and a first flat plate portion extending from the lower end of the arc portion and inclining inwardly toward the housing as it extends downward. a rectangular cylindrical housing including a first wall portion and a second wall portion facing 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 fins arranged in a thickness direction in a direction in which the first wall portion and the second wall portion face each other, the fins being arranged inside and at a lower part of the housing in the thickness direction;
a plurality of heat transfer tubes that pass through the plurality of fins in the housing in the opposing direction;
a plurality of water pipes connected to the plurality of heat transfer pipes;
A heat exchanger comprising:
further comprising a guide member fixed to the third wall portion and the fourth wall portion,
the third wall portion and the fourth wall portion have a plurality of recessed grooves recessed from outer wall surfaces of the third wall portion and the fourth wall portion inwardly of the housing and extending in the opposing direction, and a plurality of protrusions protruding from inner wall surfaces of the third wall portion and the fourth wall portion inwardly of the housing and extending in the opposing direction at positions corresponding to the plurality of recessed grooves,
the plurality of water pipes are disposed above the plurality of heat transfer pipes and are attached to the plurality of recessed grooves of the housing;
the guide member is fixed to at least the lowest-positioned convex portion among the plurality of convex portions, and guides the combustion exhaust gas flowing downward along the inner wall surfaces of the third wall portion and the fourth wall portion toward the inside of the housing;
the guide member includes an arc portion fixed to the protrusion from an upper end to a lower end thereof so as to cover the protrusion, and a first flat plate portion extending from the lower end of the arc portion and inclining inwardly of the housing as it extends downward;
the guide member further includes a second flat plate portion extending upward from an upper end of the arc portion and fixed to overlap inner wall surfaces of the third wall portion and the fourth wall portion,
The first flat plate portion and the second flat plate portion have the same shape and size,
A heat exchanger, wherein the guide member is formed symmetrically with respect to an imaginary line passing through a midpoint between the first flat plate portion and the second flat plate portion and a circumferential center of the arc portion. the plurality of fins each include a folded portion that is arranged at an upper portion of an end portion on the third wall portion side and an end portion on the fourth wall portion side and is folded back toward the first wall portion side or the second wall portion side,
The folded portion is inclined inwardly of the housing as it extends upward,
4. The heat exchanger according to claim 2, wherein a lower end of the first flat plate portion is disposed near an upper end of the folded portion. A water heater comprising a burner and a heat exchanger according to any one of claims 1 to 4.