Heat exchangers and water heaters

Abstract

To provide as heat exchanger capable of suppressing damage of heat transfer pipes, and a water heater including the same.SOLUTION: A primary heat exchanger 5 includes: an inner casing 20 which includes a first wall portion and a second wall portion, and a third wall portion 33 and a fourth wall portion 34 connected to the first wall portion and the second wall portion, and in which combustion exhaust passes; a plurality of fins 21 arranged juxtaposed in a first direction where the first wall portion and the second wall portion are opposed to each other, at a lower portion inside of the inner casing and formed with a plurality of through holes 50 penetrating respectively through the fins in the first direction; and heat transfer pipes 22 inserted in the through holes 50. Each fin 21 has: a flange-shaped heat receiving portion 52 projecting toward a radial outer side of each through hole 50; a connecting portion 53 for connecting lower parts of the heat receiving portions 52 adjacent to each other in a second direction where the third wall portion 33 and the fourth wall portion 34 are opposed to each other; end edge portions 54 fixed to the third wall portion 33 and the fourth wall portion 34 at both ends in the second direction of each fin 21; and a temperature difference suppression portion 56 for reducing a temperature difference between an upper part and a lower part of the heat transfer pipes 22 disposed at both end portions in the second direction.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a heat exchanger and a water heater. [Background technology]

[0002] A known heat exchanger for use in a water heater 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 arranged inside the inner casing, 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 fins have edge portions fixed to the inner wall surface of the inner casing at both the front and rear ends. The multiple heat transfer tubes penetrate each fin inside the inner casing in the left-right direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-143841 Summary of the Invention [Problem to be solved by the invention]

[0004] In the primary heat exchanger, the combustion exhaust gas from the burner flows downstream due to the pressure of the fan and passes between the fins. During this process, the heat of the combustion exhaust gas is transferred to the heat transfer tube via the fins and recovered by the water flowing through the heat transfer tube. Because high-temperature combustion exhaust gas flows upstream between the fins and relatively low-temperature combustion exhaust gas, where heat recovery has progressed, flows downstream between the fins, the upstream side (upper side) of the fins becomes hotter and the downstream side (lower side) of the fins becomes relatively cooler. As a result, the upper part of the heat transfer tube that passes through the fins thermally expands more than the lower part, causing the heat transfer tube to deform upward.

[0005] Among the multiple heat transfer tubes, those located near the center of the inner casing are farther from the edges of the fins fixed to the inner wall of the inner casing, allowing for a relatively high degree of freedom of deformation. Therefore, the heat transfer tubes near the center of the inner casing are more likely to be allowed to deform upward as described above. However, the heat transfer tubes located at the front and rear ends of the inner casing are closer to the edges of the fins fixed to the inner wall of the inner casing, limiting their deformation. Therefore, the heat transfer tubes at the front and rear ends of the inner casing are less likely to be allowed to deform upward. As a result, thermal expansion can cause stress to concentrate on parts of the heat transfer tubes at the front and rear ends of the inner casing, potentially damaging the heat transfer tubes. This problem is particularly pronounced in heat exchangers made of stainless steel, which has lower thermal conductivity and toughness than copper and other materials.

[0006] The present disclosure was completed based on the above circumstances, and aims to provide a heat exchanger in which damage to heat transfer tubes is suppressed, and a water heater including the same. [Means for solving the problem]

[0007] The heat exchanger of the present disclosure includes a stainless steel 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 of the first wall portion and the second wall portion and joined to the other end of the first wall portion and the second wall portion, respectively, and through which combustion exhaust gas passes downward; a plurality of stainless steel fins arranged inside and at a lower part of the housing, the fins being aligned in a first direction in which the first wall portion and the second wall portion oppose each other, and each having a plurality of through holes formed therein and penetrating in the first direction; and a plurality of stainless steel heat transfer tubes being inserted into each of the through holes. each of the fins has a flange-shaped heat receiving portion that protrudes radially outward from the hole edge of each of the through holes; a connecting portion that connects lower portions of the heat receiving portions that are adjacent in the second direction in which the third wall portion and the fourth wall portion face each other; edge portions that are fixed to the third wall portion and the fourth wall portion at both ends of each of the fins in the second direction, respectively; and a temperature difference suppressing portion that reduces the temperature difference between upper and lower portions of the heat transfer tubes that are arranged at both ends in the second direction among the plurality of heat transfer tubes. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a heat exchanger in which damage to heat transfer tubes is suppressed, and a water heater including the same. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a front view of a water heater according to an embodiment, with a front cover omitted. [Figure 2] FIG. 2 is a front view of the water heater with the resin sheet, controller, and display / operation panel omitted. [Figure 3] FIG. 3 is a perspective view of the primary heat exchanger. [Figure 4] FIG. 4 is a right side view of the primary heat exchanger with the lids of the headers removed. [Figure 5] FIG. 5 is a left side view of the primary heat exchanger with the lids of the headers removed. [Figure 6] FIG. 6 is a cross-sectional view taken along line AA in FIG. [Figure 7] FIG. 7 is an enlarged view of the periphery of the through-hole at the front end of the fin in FIG. [Figure 8] FIG. 8 is a perspective view of the fin with some of the repeating structures omitted. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be listed and exemplified. (1) The heat exchanger of the present disclosure includes a stainless steel rectangular cylindrical housing having 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 of the first wall portion and the second wall portion and joined to the other end of the first wall portion and the second wall portion, respectively, through which combustion exhaust passes downward; a plurality of stainless steel fins arranged inside and at the bottom of the housing in a first direction in which the first wall portion and the second wall portion face each other, and each having a plurality of through holes formed therein and penetrating in the first direction; and a plurality of stainless steel heat transfer tubes inserted into each of the through holes. wherein each of the fins has a flange-shaped heat receiving portion that protrudes radially outward from the hole edge of each of the through holes, a connecting portion that connects lower portions of the heat receiving portions that are adjacent in the second direction in which the third wall portion and the fourth wall portion face each other, edge portions that are fixed to the third wall portion and the fourth wall portion at both ends of each of the fins in the second direction, respectively, and a temperature difference suppressing portion that reduces the temperature difference between upper and lower portions of the heat transfer tubes that are arranged at both ends in the second direction among the plurality of heat transfer tubes.

[0011] With this configuration, the temperature difference suppression section can reduce the temperature difference between the upper and lower portions of the heat transfer tubes arranged at both ends in the second direction, thereby suppressing damage to the heat transfer tubes arranged at both ends in the second direction due to thermal expansion.

[0012] (2) It is preferable that a cavity portion recessed radially inward is provided in the upper part of the heat receiving portion of the hole edge portion of the through hole arranged at both ends of each fin in the second direction, and that the cavity portion is used as the temperature difference suppression portion.

[0013] With this configuration, the cavity, which has a simple structure, can be used as the temperature difference suppression unit. That is, by providing the cavity, the amount of heat that the upper portion of the heat receiving unit receives from the combustion exhaust gas can be reduced, thereby reducing the temperature difference between the upper and lower portions of the heat transfer tubes arranged at both ends in the second direction.

[0014] (3) It is preferable that the cavity portion is provided in an upper portion of the heat receiving portion at a position spaced apart from the adjacent edge portion in the second direction.

[0015] With this configuration, the amount of heat received from the combustion exhaust gas can be made uniform between the heat receiving portion on the edge side, where the combustion exhaust gas has difficulty passing through, and the heat receiving portion on the side away from the edge side in the second direction, thereby further suppressing damage to the heat transfer tube due to thermal expansion.

[0016] (4) It is preferable that a plurality of the cavities are provided adjacent to each other in the heat receiving portion, and that a protrusion protruding radially outward from the hole edge of the through hole is provided between adjacent cavities.

[0017] With this configuration, the protrusion can recover the heat of the combustion exhaust, thereby preventing a significant decrease in heat transfer efficiency that would otherwise be caused by the formation of the temperature difference suppression section. Furthermore, when forming a burring section on the edge of the through hole, the protrusion can provide a portion for pressing the fin.

[0018] (5) The water heater of the present disclosure is a water heater including a burner and the above-described heat exchanger.

[0019] With this configuration, it is possible to provide a water heater equipped with a heat exchanger in which damage to the heat transfer tubes is suppressed.

[0020] <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.

[0021] [Overall structure of the water heater] Fig. 1 is a front view of water heater 1 with the front cover removed. Fig. 2 shows water heater 1 of Fig. 1 with resin sheet 26, controller 12, and display / operation panel 13 removed. Water heater 1 comprises a square box-shaped outer casing 2 with an open front, and an inner body 3 housed within outer casing 2. 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 water heater 1 is of a downward combustion type in which the combustion exhaust gas from burner 4 flows from top to bottom.

[0022] 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 is installed in the lower center of the inner body 3, and is exposed from the front cover.

[0023] [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 on 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.

[0024] [Primary heat exchanger] 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 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. The rectangular cylindrical inner casing 20, the plurality of fins 21, the plurality of heat transfer pipes 22, and the plurality of water pipes 23 are made of stainless steel.

[0025] As shown in FIG. 1, a strip-shaped resin sheet 26 having a serpentine 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.

[0026] 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 first direction), and a third wall portion 33 and a fourth wall portion 34 that are joined at one end (front end) of the first wall portion 31 and at the other end (rear end) of the second wall portion 32, respectively. The third wall portion 33 and the fourth wall portion 34 face each other in the front-rear direction (an example of a second direction). In this embodiment, the first wall portion 31 is a right wall portion of the inner casing 20, and the second wall portion 32 is a left wall portion of the inner casing 20. The third wall portion 33 is a front wall portion of the inner casing 20, and the fourth wall portion 34 is a rear wall portion of the inner casing 20.

[0027] As shown in Figures 3 and 6, multiple fins 21 (only some of which are shown) are arranged side by side at predetermined intervals in the left-right direction in the lower part of the inner casing 20. Multiple heat transfer tubes 22 are linear and extend left and right, and are arranged side by side in the front-rear direction in the lower part of the inner casing 20. Multiple heat transfer tubes 22 penetrate each fin 21 in the left-right direction. As shown in Figures 4 to 6, the cross-sectional shape of the heat transfer tube 22 is an ellipse with the major axis direction being 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.

[0028] 3 and 6, the water pipes 23 are located above the heat transfer pipes 22, and are arranged in groups of three at predetermined intervals in the up-down direction on the outer wall surfaces of the third wall portion 33 and the fourth wall portion 34 of the inner casing 20. The water pipes 23 are linear and extend in the left-right direction. The cross section of the water pipes 23 is circular.

[0029] 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 FIGS. 4 and 5, the lid portions of the headers 40, 42, 43, and 45 are omitted so that the connections between the heat transfer pipe 22 and the water pipe 23 and the headers 40, 42, 43, and 45 can be easily seen.

[0030] 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-rear direction. As a result, the multiple heat transfer tubes 22 are connected together in a serpentine shape. However, the lower header 40 at the rearmost part 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 lower header 40 at the rearmost part of the first wall portion 31 is connected to a joint tube 41. As shown in Figure 1, the joint tube 41 is connected to the secondary heat exchanger 6 via a connecting tube 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.

[0031] 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.

[0032] Therefore, the hot and cold water circulation path 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.

[0033] [Multiple fins, through holes] The configuration of the fins 21 will be described below with reference to FIGS. 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 in the fins 21 so as to penetrate in the left-right direction and are spaced apart in the front-rear direction. The heat transfer tubes 22 are adapted to be inserted through the through-holes 50 of the fins 21.

[0034] [Heat receiving part, connection part] As shown in Figure 8, the inner edge of the through hole 50 of the fin 21 is provided with a burring portion 51 that protrudes to the left. The fin 21 is provided with a flange-shaped heat receiving portion 52 that protrudes radially outward from the hole edge of the through hole 50. The heat receiving portion 52 receives heat from the combustion exhaust gas flowing from above to below inside the inner casing 20, and transfers the heat to the heat transfer tube 22 inserted into the through hole 50, thereby heating the hot water inside the heat transfer tube 22. Two heat receiving portions 52 adjacent in the front-to-rear direction are connected at their lower portions by a connecting portion 53.

[0035] [Edge] The fin 21 has edge portions 54 at both ends in the front-rear direction. As shown in Fig. 6, the front edge portion 54 is disposed so as to abut against and be fixed to the inner wall surface of the lower part of the third wall portion 33. The rear edge portion 54 is disposed so as to abut against and be fixed to the inner wall surface of the lower part of the fourth wall portion 34.

[0036] [Cavity part] As shown in FIG. 8 , a cavity 55 is provided in a heat receiving portion 52E provided at the edge of the through-hole 50 disposed at both the front and rear ends of the fin 21. The cavity 55 is formed in an upper portion of the heat receiving portion 52E and recessed radially inward of the through-hole 50. Providing the cavity 55 reduces the volume of the upper portion of the heat receiving portion 52E, thereby reducing the amount of heat received by the upper portion of the heat receiving portion 52E from the exhaust combustion gas passing through the inner casing 20 (see FIGS. 6 and 7 ). Therefore, the amount of heat received by the upper portion of the heat transfer tube 22 from the upper portion of the heat receiving portion 52E also decreases. Furthermore, the heat of the exhaust combustion gas that is not collected by the upper portion of the heat receiving portion 52E is collected by the lower portion of the heat receiving portion 52E, and the collected heat is transferred to the lower portion of the heat transfer tube 22. Therefore, providing the cavity 55 in the upper portion of the heat receiving portion 52E increases the amount of heat received by the lower portion of the heat transfer tube 22.

[0037] [Temperature difference suppression section] In a configuration in which the combustion exhaust gas passes from top to bottom within the middle casing 20, the upper portion of the heat transfer tube 22 becomes hotter than the lower portion, and the heat transfer tube 22 tends to deform upward. However, in this embodiment, as described above, the cavity portion 55 functions as a temperature difference suppression portion 56 that reduces the temperature difference between the upper and lower portions of the heat transfer tube 22, and therefore deformation of the heat transfer tubes 22 arranged at both the front and rear ends of the fin 21 can be suppressed. Because the heat transfer tubes 22 at both front and rear ends are close to the edge portions 54 to which the fins 21 and the inner casing 20 are fixed, deformation of the heat transfer tubes 22 at both front and rear ends due to thermal expansion is likely to be restricted by the fixing structure between the edge portions 54 and the inner casing 20. However, by providing the cavity portions 55, upward warping deformation of the heat transfer tubes 22 at both front and rear ends is suppressed, so that the heat transfer tubes 22 at both front and rear ends are less likely to be damaged by thermal expansion.

[0038] The cavity portion 55 is not provided on the heat receiving portions 52 other than the heat receiving portions 52E at both the front and rear ends of the fin 21, i.e., the heat receiving portions 52 arranged inside the inner casing 20 (see FIG. 6). The heat receiving portions 52 arranged inside the inner casing 20 do not have anything around them to restrict deformation, so deformation of the heat transfer tubes 22 arranged inside the inner casing 20 is permitted, and the heat transfer tubes 22 are less likely to be damaged. In this way, by not providing a cavity portion 55 in the heat receiving portion 52 arranged inside the middle casing 20, the amount of heat received by the fins 21 from the combustion exhaust gas is not reduced as much as possible, and the decrease in thermal efficiency in the primary heat exchanger 5 can be kept to a necessary minimum.

[0039] 6 and 8, the cavity 55 provided in the front heat receiving portion 52E is disposed on the rear side of the upper portion of the heat receiving portion 52E. The cavity 55 provided in the rear heat receiving portion 52E is disposed on the front side of the upper portion of the heat receiving portion 52E. In other words, the cavity 55 is provided in a position in the heat receiving portion 52E that is spaced apart from the adjacent edge portion 54 in the front-to-rear direction.

[0040] 7, combustion exhaust gas does not easily pass through the space SP between the edge portion 54 and the heat transfer tube 22. Therefore, an upper portion of the heat receiving portion 52E on the edge portion 54 side (front side in FIG. 7) receives a smaller amount of heat from the combustion exhaust gas than an upper portion of the heat receiving portion 52E on the opposite side of the edge portion 54 in the front-to-rear direction (rear side in FIG. 7). Therefore, by providing the cavity portion 55 at a position away from the edge portion 54 in the front-to-rear direction rather than on the edge portion 54 side of the heat receiving portion 52E, it is possible to balance the amount of heat received from the combustion exhaust gas between the front and upper portion of the heat receiving portion 52E and the rear and upper portion of the heat receiving portion 52E, and it is possible to further suppress damage to the heat transfer tube 22 due to thermal expansion.

[0041] [Protrusion] A plurality of cavities 55 are provided adjacent to the heat receiving portion 52E. As shown in Fig. 7, in this embodiment, two cavities 55 are provided in the front heat receiving portion 52E. A protrusion 57 is formed between the two cavities 55, protruding radially outward from the edge of the through hole 50. Similarly, two cavities 55 and a protrusion 57 are provided in the rear heat receiving portion 52E (see Fig. 6). The protrusions 57 prevent the amount of heat received by the heat receiving portions 52E from excessively decreasing due to the formation of the cavity portions 55. Furthermore, in the process of manufacturing the fins 21 by processing the metal plate material, the protrusions 57 can be used as portions for holding the fins 21 when the through holes 50 and the burring portions 51 are formed.

[0042] [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 with 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.

[0043] 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.

[0044] [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 intake 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, then 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.

[0045] 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 tubes 22 and recovering sensible heat. At this time, by providing the cavity portion 55 (temperature difference suppression portion 56), the temperature difference between the upper and lower portions of the heat transfer tubes 22 at both front and rear ends can be reduced, making the heat transfer tubes 22 at both front and rear ends less susceptible to damage due to thermal expansion.

[0046] The combustion exhaust gas 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.

[0047] The combustion exhaust gas that has passed 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 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.

[0048] [Effects of the embodiment] As described above, in the primary heat exchanger 5 of this embodiment, each fin 21 has a flange-shaped heat receiving portion 52 that extends radially outward from the hole edge of each through hole 50, edge portions 54 that are fixed to the third wall portion 33 and the fourth wall portion 34 at both front and rear ends of each fin 21, and a temperature difference suppression portion 56 that reduces the temperature difference between the upper and lower portions of the heat transfer tubes 22 arranged at both front and rear ends of the plurality of heat transfer tubes 22.

[0049] With this configuration, the temperature difference suppression section 56 can reduce the temperature difference between the upper and lower portions of the heat transfer tubes 22 arranged at both front and rear ends, thereby suppressing damage to the heat transfer tubes 22 arranged at both front and rear ends due to thermal expansion.

[0050] Furthermore, in this embodiment, as an example of a temperature difference suppression section 56, a cavity section 55 that is recessed radially inward of the through hole 50 is provided in the upper part of the heat receiving section 52E at the hole edge of the through hole 50 arranged at both the front and rear ends of each fin 21. Therefore, the simple structure of the cavity section 55 reduces the amount of heat that the upper part of the heat receiving section 52E receives from the combustion exhaust gas, thereby reducing the temperature difference between the upper and lower parts of the heat transfer tubes 22 arranged at both the front and rear ends.

[0051] In this embodiment, the cavity portion 55 is located in the upper part of the heat receiving portion 52E at a position away from the adjacent edge portion 54 in the front-to-rear direction. Therefore, the amount of heat received from the combustion exhaust gas can be made uniform between the heat receiving portion 52E on the edge portion 54 side, through which the combustion exhaust gas has difficulty passing, and the heat receiving portion 52E on the side away from the edge portion 54 in the front-to-rear direction, thereby further suppressing damage to the heat transfer tube 22 due to thermal expansion.

[0052] In this embodiment, a plurality of cavities 55 are provided adjacent to each other in the heat receiving portion 52E, and the protrusions 57 are provided between adjacent cavities 55, so that the heat of the combustion exhaust can be recovered by the protrusions 57 and it is possible to suppress an extreme decrease in heat transfer efficiency that would otherwise occur due to the formation of the temperature difference suppression portion 56. Furthermore, when the burring portion 51 is formed on the edge of the through hole 50, the protrusions 57 can ensure a portion for pressing the fins 21.

[0053] The water heater 1 of this embodiment is equipped with a burner 4 and the above-mentioned primary heat exchanger 5, so it is possible to provide a water heater 1 equipped with a primary heat exchanger 5 in which damage to the heat transfer tube 22 is suppressed.

[0054] <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.

[0055] In the embodiment, a configuration including two heat exchangers, a primary heat exchanger 5 and a secondary heat exchanger 6, has been exemplified, but the water heater may also be configured to include only a primary heat exchanger.

[0056] In the embodiment, the primary heat exchanger 5 used for hot water supply has been exemplified 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.

[0057] The scope of the present disclosure is not limited to the above-described embodiments, but is intended to include all modifications within the scope indicated by the claims or within the scope equivalent to the claims. [Explanation of symbols]

[0058] 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...intermediate casing (housing), 21...fin, 22...heat transfer tube, 22A...flow rate adjusting member, 23...water pipe, 24...connecting pipe, 25...hot water outlet pipe, 26...resin sheet, 31...first wall portion, 32...second wall portion, 33...third wall portion, 34...fourth 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, 52E...heat receiving portion provided on the hole edge portion of the through hole arranged at both front and rear ends of the fin, 53...connecting portion, 54...edge portion, 55...cavity portion, 56...temperature difference suppressing portion, 57...protruding 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 pipe section SP: Space between the edge and the heat transfer tube

Claims

1. a stainless steel 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 of the first wall portion and one end of the second wall portion, respectively, and through which combustion exhaust gas passes downward; a plurality of stainless steel fins arranged in a first direction in which the first wall portion and the second wall portion face each other, the fins being formed with a plurality of through holes penetrating in the first direction, inside and at a lower portion of the housing; a plurality of stainless steel heat transfer tubes inserted into the through holes; A heat exchanger comprising: each fin has a flange-shaped heat receiving portion that protrudes radially outward from a hole edge portion of each of the through holes; a connecting portion that connects lower portions of the heat receiving portions that are adjacent in the second direction in which the third wall portion and the fourth wall portion face each other; edge portions that are fixed to the third wall portion and the fourth wall portion at both ends of each fin in the second direction; a notch formed above each of the through holes in the heat receiving portion; and a cavity portion that is located below the notch in the heat receiving portion and that reduces a temperature difference between upper and lower portions of the heat transfer tubes that are arranged at both ends in the second direction among the plurality of heat transfer tubes, The cavity portion is formed so as to be continuous with the notch, The cavity portion is recessed radially inward and is provided at a hole edge portion of the through hole arranged only at both end portions of each of the fins in the second direction, The cavity portion is provided at a position farther in the second direction from the edge portion closer to the cavity portion than the notch in the heat receiving portion.

2. A heat exchanger as described in Claim 1, wherein the cavity portion is arranged from a position connected to the notch in the heat receiving portion to near the connecting portion.

3. a plurality of the cavities are provided adjacent to each other in the heat receiving portion, 3. The heat exchanger according to claim 1, wherein a protrusion protruding radially outward from a hole edge of the through hole is provided between adjacent cavity portions.

4. A water heater comprising a burner and the heat exchanger according to any one of claims 1 to 3.

Images