Heat exchangers and water heaters

Abstract

To prevent a brazing material from falling at the time of brazing.SOLUTION: A primary heat exchanger 5 includes an intermediate casing 20, a plurality of heat transfer pipes 22, and a plurality of lower side water collection parts 25. In the primary heat exchanger 5, each of the plurality of lower side water collection parts 25 is disposed at a left side wall part 31 and a right side wall part 32. The lower side water collection part 25 includes: a fixing part 40 including a bottom wall part 41 fixed to an outer surface of the intermediate casing 20, and a peripheral wall part 42 rising from the bottom wall part 41 and opening to the opposite side from the intermediate casing 20; and a lid part 43 for closing the opening of the peripheral wall part 42 by being fitted in the peripheral wall part 42 of the fixing part 40. At an end part on the bottom wall part side 41 in the peripheral wall part 42, a recessed part 44 is formed recessed toward the inside of the lower side water collection part 25, and the recessed part 44 has a placement surface 45 continued to an interface between the outer surface of the intermediate casing 20 and the bottom wall part 41.SELECTED DRAWING: Figure 12

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 includes a rectangular cylindrical inner casing to which a burner is attached, a plurality of fins arranged side by side in the left-right direction inside the inner casing, and a plurality of heat transfer tubes passing through each of the fins in the left-right direction. The inner casing has a first wall portion and a second wall portion facing the first wall portion in the left-right direction. The first wall portion and the second wall portion each have a plurality of through holes through which each of the heat transfer tubes passes. The plurality of fins each have a through hole through which the heat transfer tubes pass. Each of the heat transfer tubes is fixed to the inner casing with both ends slightly protruding outside the first wall portion and the second wall portion.

[0003] The outer surfaces of the first wall and the second wall are provided with a plurality of lower headers that connect the ends of adjacent pairs of heat transfer tubes so that water can flow between them. The lower headers include a base part with a bottom fixed to the outer surfaces of the first wall and the second wall, and a peripheral wall rising from the bottom, and a lid that is fitted into the base part. The lower headers function to direct hot and cold water introduced from one heat transfer tube to the other heat transfer tube. As a result, the heat transfer tubes are connected in a serpentine pattern via the lower headers, and the multiple heat transfer tubes are configured to function as a continuous series of heat collection tubes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-143841 Summary of the Invention [Problem to be solved by the invention]

[0005] The opposing surfaces of the base part and the first wall part, and the opposing surfaces of the base part and the second wall part, are fixed together by brazing. Brazing is performed by placing a brazing material on the top surface of the base part and melting the brazing material, for example, by furnace brazing. However, it is difficult to place the brazing material on the top surface of the base part in a stable position, and the brazing material may fall off during brazing. Furthermore, the lid part may be inserted into the base part at an angle relative to the correct mounting position or may be inserted insufficiently, which may result in insufficient watertightness between the lid part and the base part.

[0006] The present invention was developed in light of the above circumstances, and its object is to provide a heat exchanger and a water heater that can prevent the brazing material from falling off during brazing. [Means for solving the problem]

[0007] The heat exchanger of the present disclosure is a heat exchanger including: a rectangular cylindrical housing having a first wall portion and a second wall portion opposed to each other, the housing having a plurality of holes formed in the first wall portion and the second wall portion, the housing having a through hole in the first wall portion and the second wall portion, the plurality of heat transfer tubes being fixed to the housing with their ends passing through the plurality of holes; and a plurality of water-passing components that connect ends of a pair of adjacent heat transfer tubes among the plurality of heat transfer tubes so as to be able to pass water therethrough, thereby connecting the plurality of heat transfer tubes into one. The water-passing parts are arranged on the second wall portions, and each of the water-passing parts comprises a fixed portion having a bottom wall portion fixed to the outer surface of the housing, and a peripheral wall portion that rises from the bottom wall portion and opens on the side opposite the housing, and a lid portion that is fitted into the peripheral wall portion of the fixed portion to close the opening of the peripheral wall portion, and a recess portion that is recessed toward the inside of the water-passing part is formed at the end of the peripheral wall portion on the bottom wall portion side, and the recess portion has a mounting surface that is continuous with the interface between the outer surface of the housing and the bottom wall portion, making it a heat exchanger. [Effects of the Invention]

[0008] According to the present invention, it is possible to prevent the brazing material from dropping during brazing. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a front view of the water heater with the front cover removed. [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 front view of the inner barrel of FIG. [Figure 4] 4 is a left side view of the inner barrel of FIG. 2. FIG. [Figure 5] FIG. 5 is a left side view of the inner body in which the lids are omitted from the left and lower water collecting sections of FIG. [Figure 6] 6 is a perspective view of the inner body of FIG. 2 as seen obliquely from the front left. [Figure 7] 7 is a perspective view of the inner body of FIG. 2 as seen from the right rear. [Figure 8] FIG. 8 is a plan view of the inner barrel of FIG. [Figure 9] FIG. 9 is an enlarged perspective view showing the lower water collecting portion with the left water collecting portion of FIG. 6 omitted. [Figure 10] FIG. 10 is a cross-sectional view taken along line AA in FIG. [Figure 11] FIG. 11 is an enlarged cross-sectional view showing the primary heat exchanger of FIG. [Figure 12] FIG. 12 is a cross-sectional view taken along the line BB in FIG. 8, showing an enlarged cross-sectional view of the lower water collecting portion. [Figure 13] FIG. 13 is an enlarged cross-sectional view showing the cover portion of FIG. 12 separated from the fixing portion. [Figure 14] FIG. 14 is a perspective view of the lid. [Figure 15] FIG. 15 is a perspective view of the fixing portion. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be listed and exemplified. (1) A heat exchanger disclosed herein includes a rectangular tubular housing having a first wall portion and a second wall portion opposed to each other, the first wall portion and the second wall portion each having a plurality of holes formed therein, the rectangular tubular housing penetrating in the vertical direction, a plurality of heat transfer tubes fixed to the housing with their ends passing through the plurality of holes, and a plurality of water-conducting members that connect ends of a pair of adjacent heat transfer tubes among the plurality of heat transfer tubes to each other so as to allow water to pass through, thereby connecting the plurality of heat transfer tubes into one. The plurality of water-conducting members are configured to connect the ends of the first wall portion and the second wall portion together. and the second wall portion, respectively, and the water-passing part comprises a fixed part having a bottom wall portion fixed to the outer surface of the housing, and a peripheral wall portion rising from the bottom wall portion and opening on the side opposite the housing, and a lid portion that is fitted into the peripheral wall portion of the fixed part to close the opening of the peripheral wall portion, and a recess portion that is recessed toward the inside of the water-passing part is formed at the end of the peripheral wall portion on the bottom wall portion side, and the recess portion has a mounting surface that is continuous with the interface between the outer surface of the housing and the bottom wall portion, making it a heat exchanger.

[0011] A recess is provided in the peripheral wall of the fixing portion of the water-passing component, and this recess has a mounting surface, so that the brazing material can be stably placed on this mounting surface. The mounting surface is provided so as to be continuous with the interface between the outer surface of the housing and the bottom wall. Therefore, for example, by melting the brazing material by furnace brazing, the brazing material spreads over the interface between the outer surface of the housing and the bottom wall, and the bottom wall can be fixed to the outer surface of the housing by brazing. The recess is shaped to be recessed toward the inside of the water-passing component, so that the brazing material can be prevented from falling off during brazing, resulting in insufficient brazing.

[0012] (2) It is preferable that the recessed portion has a stepped surface that is continuous with the interface between the outer peripheral surface of the lid portion and the inner peripheral surface of the peripheral wall portion, and that the opening end of the lid portion on the housing side is capable of abutting against the stepped surface when the lid portion is fitted into the peripheral wall portion of the fixing portion. When the lid is fitted into the peripheral wall of the fixed part, the opening edge of the lid facing the housing abuts against the stepped surface of the recess, restricting the fitting of the lid. This allows the recess to function as a positioning part for temporarily fixing the lid in a predetermined position. This allows the lid to be temporarily fixed in the fixed part in a fixed position. As a result, the lid and fixed part can be stably fixed by brazing, maintaining the designed waterproofing performance.

[0013] (3) It is preferable that the fixing portion is formed in a shape that is symmetrical in the vertical direction, and that the fixing portion has a plurality of the recesses provided at positions that are symmetrical in the vertical direction. When temporarily fastening the fixing part to the outer surface of the housing, there is no need to pay attention to the up and down direction, improving work efficiency. Also, when temporarily fastening the lid part into the fixing part, the fitting operation of the lid part is restricted to a position that is symmetrical up and down, so it is possible to prevent the lid part from being temporarily fastened into the fixing part in an unbalanced state.

[0014] (4) The water heater of the present disclosure is a water heater including a burner, a primary heat exchanger connected to the burner and through which combustion exhaust from the burner passes, and a secondary heat exchanger connected to the primary heat exchanger and through which combustion exhaust from the primary heat exchanger passes. Such a water heater can prevent the brazing material from falling off during brazing.

[0015] <Embodiment> Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 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 16, controller 12, and display / operation panel 13 removed.

[0016] [Overall structure of the water heater] This water heater 1 is a reverse combustion type that houses an inner body 3 on which, from top to bottom, a burner 4, a primary heat exchanger 5, and a secondary heat exchanger 6 are arranged in order inside a square box-shaped housing 2 that is open at the front. Also provided inside the housing 2 are an exhaust section 7 that wraps around from the bottom of the inner body 3 to the rear and faces upward, a fan unit 8 connected to the burner 4 on the right side of the inner body 3, and a gas supply unit 10 that is connected to the fan unit 8 below the fan unit 8 and receives fuel gas from a gas inlet pipe 11 via a gas governor 9. A controller 12 that houses an electrical circuit board is installed on the lower right side of the inner body 3, and a display and operation panel 13 that is exposed from the front cover is installed in the center below the controller 7.

[0017] [Burner] Burner 4 is an all-primary air type that burns a mixture of fuel gas and all the combustion air required for combustion, and 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, and the top of upper casing 14 is closed by a chamber 15 that protrudes upward and to which fan unit 8 is connected.

[0018] [Primary heat exchanger] As shown in Figures 6 to 8, the primary heat exchanger 5 includes a rectangular cylindrical inner casing 20 to which the burner 4 is attached, a plurality of heat transfer fins 21, 21... (only some of which are shown in each figure) arranged in the lower part of the inner casing 20 and juxtaposed at predetermined intervals in the left-right direction, which is the thickness direction, and heat transfer tubes 22 passing through each heat transfer fin 21 in the left-right direction. The primary heat exchanger 5 is made of stainless steel. The inner casing 20 has a rectangular cylindrical shape that passes through in the vertical direction. The inner casing 20 is an example of a housing.

[0019] The intermediate casing 20 has a left side wall 31 and a right side wall 32 that face each other in the left-right direction. As shown in Fig. 5, a plurality of holes 33 are formed in each of the left side wall 31 and the right side wall 32. Ends of a plurality of heat transfer tubes 22 are disposed so as to pass through each hole 33. The ends of each heat transfer tube 22 are fixed to the inner surface of the corresponding hole 33.

[0020] As shown in FIG. 6 , the heat transfer tubes 22 include eight straight large-diameter tubes 23, 23 ··, each having an elliptical cross section and with its major diameter extending in the up-down direction, which are arranged at a predetermined interval in the front-to-rear direction at the lowest level, and straight small-diameter tubes 24, 24 ··, each having a circular cross section, which are arranged three by three on each side at a predetermined interval in the up-down direction on the front and rear outer surfaces of the upper wall portion 20 b of the intermediate casing 20 above the eight straight large-diameter tubes 23, 23 ··.

[0021] 8, the large diameter pipe 23 has a serpentine shape in which two adjacent ends in the front and rear are connected alternately on the left and right by the lower water collecting portions 25 provided on both wall portions 31, 32 of the inner casing 20, forming a single continuous pipe. A pair of guide members 34, 34 that guide the combustion exhaust gas toward the center of the secondary heat exchanger 6 is provided below the heat transfer fins 21 on both wall portions 31, 32 of the inner casing 20.

[0022] A left-side water collecting section 28 is provided on the left side wall 31 of the intermediate casing 20, connecting the left ends of the three front and rear small diameter pipes 24. As shown in Fig. 7, a connecting pipe 26 to the secondary heat exchanger 6 is connected to the right end of the rearmost large diameter pipe 23, and the right end of the frontmost large diameter pipe 23 is connected to the right ends of the front three small diameter pipes 24 by a front water collecting section 27 that extends vertically. A right-side water collecting section 29 is provided on the right side wall 32 of the intermediate casing 20, connecting the right ends of the rear three small diameter pipes 24, and a hot water outlet pipe 30 is connected to the right-side water collecting section 29.

[0023] Therefore, in the heat transfer pipes 22 of the primary heat exchanger 5, hot water that flows from the connecting pipe 26 into the rear large diameter pipe 23 flows forward in a serpentine manner, passing alternately through the bottom-most large diameter pipes 23, 23, etc., and then flows from the front-most large diameter pipe 23 through the front three small diameter pipes 24 and the rear three small diameter pipes 24 in order to the hot water outlet pipe 30.

[0024] As shown in Fig. 1, a strip-shaped resin sheet 16 having 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. 5, a turbulence plate 23a is inserted into each large diameter pipe 23 to agitate the hot and cold water passing through.

[0025] As shown in Figures 11 and 12, the heat transfer fin 21 has a horizontally elongated plate shape extending in the front-to-rear direction. Eight elliptical through holes 35, 35... are formed in the heat transfer fin 21. The through holes 35 are aligned in the front-to-rear direction at equal intervals. Burring portions 36 that protrude to the left are formed on the inner edge of each through hole 35 by burring processing.

[0026] Upper notches 37 are formed between the through holes 35 on the upper side of the heat transfer fin 21. The upper notches 37 have curved inner edges that conform to the outer peripheral shapes of the front and rear through holes 35, 35. The inner edges of the upper notches 37 are V-shaped, with the spacing between the front and rear becoming smaller as they extend downward. The lower ends of the upper notches 37 are located slightly below the centers of the long axes of the through holes 35.

[0027] Edge portions 39, 39 that abut against the inner surface of the lower wall portion 20a of the intermediate casing 20 are formed on both front and rear ends of the heat transfer fin 21. Each edge portion 39 extends in the vertical direction and is folded back to the left.

[0028] [Detailed structure of the lower catchment section] As shown in Fig. 12, the lower water collecting section 25 includes a fixing section 40 and a lid section 43. As shown in Fig. 15, the fixing section 40 has a pair of through holes 46, and includes a horizontally elongated rectangular bottom wall section 41 and a peripheral wall section 42 rising from the peripheral edge of the bottom wall section 41. The through holes 46 are formed to correspond to the outer peripheral shape of the large diameter tube 23 of the heat transfer tube 22. The lower water collecting section 25 is an example of a water-passing part.

[0029] The lower water collection section 25 is provided on both the left side wall 31 and the right side wall 32 of the middle casing 20, but since the configuration of the lower water collection section 25 is exactly the same, the lower water collection section 25 provided on the left side wall 31 will be described below as a representative, and the description of the lower water collection section 25 provided on the right side wall 32 will be omitted.

[0030] 12, the bottom wall 41 is fixed to the left side wall 31 of the inner casing 20, and the peripheral wall 42 has an opening that opens on the side opposite to the inner casing 20. As shown in FIGS. 13 and 14, the cover 43 is cylindrical with a bottom and has a horizontally elongated rectangular opening that opens on the inner casing 20 side.

[0031] When the lid portion 43 is fitted into the peripheral wall portion 42 of the fixing portion 40, the opening of the peripheral wall portion 42 is closed, and a water passage space 47 is formed inside the lower water collection portion 25. The water passage space 47 is an enclosed space that is watertight from the outside. As shown in Figure 12, the end portion 23b of the large diameter pipe 23 is disposed inside the water passage space 47. Therefore, hot and cold water introduced into the water passage space 47 from the large diameter pipe 23 connected to one of the through holes 46 is discharged to the large diameter pipe 23 connected to the other through hole 46.

[0032] A recess 44 is formed at the end of the peripheral wall 42 on the bottom wall 41 side, recessing toward the inside of the lower water collection section 25. As shown in Fig. 13, the recess 44 has a mounting surface 45 that continues to the interface between the outer surface of the left wall 31 of the inner casing 20 and the bottom wall 41. The recess 44 has a stepped surface 48 that continues to the interface between the outer peripheral surface of the lid 43 and the inner peripheral surface of the peripheral wall 42. The open end of the lid 43 on the inner casing 20 side can abut against the stepped surface 48 when the lid 43 is fitted into the peripheral wall 42 of the fixing part 40, as shown in Fig. 12.

[0033] The fixing portion 40 is formed to have a shape that is symmetrical vertically. A pair of upper and lower recesses 44, 44 are provided at positions that are symmetrical vertically in the fixing portion 40. As shown in Fig. 15, the recess 44 is located between a pair of through holes 46, 46, at the connection portion between the bottom wall portion 41 and the peripheral wall portion 42.

[0034] The primary heat exchanger 5 is manufactured by inserting the ends 23b of the large-diameter pipes 23 into the through-holes 46 of the fixing part 40 and brazing the outer surface of the left side wall 31 of the inner casing 20 to the bottom wall 41. As shown in FIG. 9 , this brazing is performed by placing a rod-shaped brazing material P in the recess 44 and heating it in a furnace. The brazing material P melts in the recess 44 and flows along the placement surface 45, and by capillary action, spreads to the interface between the outer surface of the left side wall 31 and the bottom wall 41. Once the brazing material P solidifies, the left side wall 31 of the inner casing 20 and the bottom wall 41 of the fixing part 40 can be evenly fixed together.

[0035] By providing the recessed portion 44 in the fixing portion 40 in this manner, the brazing material P can be stably placed on the placement surface 45 of the recessed portion 44. This prevents the brazing material P from falling during furnace brazing, resulting in insufficient brazing. In addition, the recessed portion 44 also functions as a restriction portion for restricting the insertion amount of the lid portion 43, allowing the lid portion 43 to be fitted into the peripheral wall portion 42 of the fixing portion 40 in a fixed position. As a result, the fixing portion 40 and the lid portion 43 can be stably brazed and fixed, making it possible to maintain the designed watertightness.

[0036] The fixing part 40 is formed in a vertically symmetrical shape when the burner 4 and the secondary heat exchanger 6 are arranged one above the other, and this fixing part 40 has a plurality of recesses 44 provided at vertically symmetrical positions, so that when temporarily fastening the fixing part 40 to the left wall part 31 of the intermediate casing 20, it is not necessary to pay attention to the vertical orientation, improving assembly efficiency. Furthermore, because the insertion of the lid part 43 is restricted to vertically symmetrical positions, it is possible to prevent the lid part 43 from being fitted into the peripheral wall part 42 of the fixing part 40 in an offset state.

[0037] [Secondary heat exchanger] The secondary heat exchanger 6 is provided in series with the primary heat exchanger 5, and as shown in FIG. 10, includes a rectangular cylindrical lower casing 55 that communicates with the intermediate casing 20, and a plurality of heat transfer plates 56, 56... arranged side by side within the lower casing 55. The heat transfer plates 56 have inclined projections and depressions. The heat transfer plates 56 are arranged alternately in the front-to-rear direction at predetermined intervals. An internal flow path 57 is formed within the lower casing 55, connecting the left and right ends of the heat transfer plates 56.

[0038] 3, an inlet 58 connected to the internal flow path 57 is provided at the lower front side of the lower casing 55, and a water supply pipe 60 is connected to this inlet 58. An outlet 59 connected to the internal flow path 57 is provided at the upper front side of the lower casing 55, and a connecting pipe 26 is connected to this outlet 59.

[0039] The exhaust section 7 includes a drain receiver 61 attached to the lower surface of the lower casing 55 of the secondary heat exchanger 6, and an exhaust duct 62 erected at the rear of the drain receiver 61. The bottom of the drain receiver 61 is connected to a neutralizer 64 via a drain discharge pipe 63. The exhaust duct 62 is a horizontally elongated rectangular tube made of synthetic resin, and an upper cover 65 having a cylindrical exhaust tube portion 66 protruding from the upper surface of the housing 2 is joined to the opening at the upper end of the exhaust duct 62.

[0040] [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 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 installed 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 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 the ignition electrode to combust.

[0041] The combustion exhaust gas from the burner 4 passes between the heat transfer fins 21, 21 in the inner casing 20 of the primary heat exchanger 5, exchanging heat with the hot water flowing in the heat transfer tubes 22 and recovering sensible heat. Within each of the large diameter tubes 23 of the heat transfer tubes 22, the hot water is agitated by the turbulence plates 23a, making it less likely that stagnation or temperature unevenness will occur.

[0042] Next, the combustion exhaust from the primary heat exchanger 5 passes between the heat transfer plates 56, 56 within the lower casing 55 of the secondary heat exchanger 6, exchanging heat with the water flowing through the internal flow path 57, and the latent heat is recovered. The combustion exhaust gas that has passed through the lower casing 55 enters the drain receiver 61 of the exhaust section 7, moves to the rear of the drain receiver 61, rises inside the exhaust duct 62, and is discharged to the outside from the exhaust pipe section 66. The drain generated in the secondary heat exchanger 6 falls into the drain receiver 61 and is discharged to the outside of the appliance via the drain discharge pipe 63 and neutralizer 64.

[0043] [Effects of the embodiment] A recess 44 is provided in the peripheral wall 42 of the fixing portion 40 of the lower water collecting portion 25. This recess 44 has a mounting surface 45, allowing the brazing material P to be stably placed on this mounting surface 45. The mounting surface 45 is provided so as to be continuous with the interface between the outer surface of the left side wall 31 of the inner casing 20 and the bottom wall 41. Therefore, by melting the brazing material P, for example, by furnace brazing, the brazing material P wets and spreads over the interface between the outer surface of the left side wall 31 of the inner casing 20 and the bottom wall 41, thereby fixing the bottom wall 41 to the outer surface of the left side wall 31 of the inner casing 20 by brazing. The recess 44 is recessed toward the inside of the lower water collecting portion 25, preventing the brazing material P from falling during brazing and resulting in insufficient brazing. The water heater 1 prevents the brazing material P from falling during brazing.

[0044] When the lid portion 43 is fitted into the peripheral wall portion 42 of the fixing portion 40, the opening end of the lid portion 43 on the left side wall portion 31 side of the intermediate casing 20 abuts against the stepped surface 48 of the recessed portion 44, thereby restricting the fitting movement of the lid portion 43, and the recessed portion 44 can function as a positioning portion for temporarily fixing the lid portion 43 in a predetermined position. Therefore, the lid portion 43 can be temporarily fixed in the fixing portion 40 in a fixed posture. As a result, the lid portion 43 and the fixing portion 40 can be stably fixed by brazing, and the designed watertight performance can be maintained.

[0045] When temporarily fastening the fixing part 40 to the outer surface of the left wall part 31 of the intermediate casing 20, there is no need to pay attention to the up and down orientation, improving work efficiency. Furthermore, when temporarily fastening the lid part 43 into the fixing part 40, the fitting operation of the lid part 43 is restricted to positions that are symmetrical up and down, so it is possible to prevent the lid part 43 from being temporarily fastened into the fixing part 40 in an unbalanced state.

[0046] [Other embodiments] In the above embodiment, the water-passing component is applied to the lower water-passing section 25, but it may also be applied to the front water collecting section 27, the left water collecting section 28, or the right water collecting section 29. In addition, in the above embodiment, the water-passing component is applied to the primary heat exchanger 5, but it may also be applied to the secondary heat exchanger 6.

[0047] In the above embodiment, the fixing portion 40 has a pair of recessed portions 44, but the number of recessed portions 44 may be one, or may be three or more. Furthermore, the fitting operation of the lid portion 43 is restricted by the stepped surface 48 of the recessed portion 44, but a stepped surface may be provided separately from the recessed portion 44. In this case, the position of the stepped surface is not limited to a position that is symmetrical in the vertical direction, and may be a position that is symmetrical in the horizontal direction.

[0048] In the above embodiment, the lower water collection section 25, which connects the ends of a pair of adjacent heat transfer tubes 22 among the multiple heat transfer tubes 22 so that water can flow between them, was described as a representative water-passing part. However, any part that allows water to pass through so that the multiple heat transfer tubes 22 are connected into one may be used, and the lower water collection section 25 provided at the right end of the rearmost large diameter tube 23 is also a water-passing part.

[0049] In addition, as is common to all inventions, the configuration of the burner, primary heat exchanger, and secondary heat exchanger, the arrangement of the fan unit, the arrangement of the controller, etc. can be changed as appropriate. The secondary heat exchanger does not have to be provided, and the system does not have to be a reverse combustion system.

[0050] Furthermore, in the primary heat exchanger, the number of large-diameter tubes can be changed as appropriate, and a configuration without small-diameter tubes is also acceptable. The cross-sectional shape can be elliptical as in the above configuration, making the dimensions in the minor axis direction compact, but shapes other than elliptical can also be adopted. The orientation of the heat transfer fins and heat transfer tubes can also be reversed from that in the above embodiment, and the heat transfer fins and heat transfer tubes can be provided in multiple stages rather than in a single stage.

[0051] Furthermore, although the fan unit is a premixing type in which a mixture of fuel gas and combustion air is supplied to the chamber, the inventions are not limited to this type and can also be applied to water heaters in which only combustion air is supplied from the fan and the fuel gas and combustion air are introduced into the chamber downstream of the fan. [Explanation of symbols]

[0052] 1: Water heater 2: Housing 3: Inner body 4: Burner 5: Primary 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 and operation panel 14: Upper casing 15: Chamber 16: Resin sheet 20: Middle casing (housing) 20a: Lower wall portion 20b: Upper wall portion 21: Heat transfer fin 22: Heat transfer pipe 23: Large diameter pipe 23a: Turbulence plate 23b: End portion 24: Small diameter pipe 25: Lower water collection portion (water passage part) 26: Connecting pipe 27: Front water collection portion 28: Left side water collection portion 29: Right side water collection portion 30: Outlet pipe 31: Left side wall portion (first wall portion) 32: Right side wall portion (second wall portion) 33: Hole portion 34: Guide member 35: Through hole 36: Burring portion 37: Upper notch portion 39: Edge portion 40: Fixing portion 41: Bottom wall portion 42: Peripheral wall portion 43: Lid portion 44: Recessed portion 45: Placement surface 46: Through hole 47: Water passage space 48: Step surface 55: Lower casing 56: Heat transfer plate 57: Internal flow path 58: Inlet 59: Outlet 60: Water supply pipe 61: Drain receiver 62: Exhaust duct 63: Drain discharge pipe 64: Neutralizer 65: Upper cover 66: Exhaust pipe P: Brazing material

Claims

1. a rectangular cylindrical housing having a first wall portion and a second wall portion opposed to each other, the housing having a plurality of holes respectively formed in the first wall portion and the second wall portion, the housing being penetrated in the up-down direction; a plurality of heat transfer tubes fixed to the housing with their ends passing through the plurality of holes; a plurality of water-passing components that connect ends of adjacent pairs of the plurality of heat transfer tubes to each other so that the plurality of heat transfer tubes are connected to one another in a water-passable manner, the plurality of water-passing parts are respectively disposed on the first wall portion and the second wall portion, The water-passing component includes a fixing part having a bottom wall portion fixed to the outer surface of the housing and a peripheral wall portion rising from the bottom wall portion and opening on the opposite side of the housing, and a lid portion fitted into the peripheral wall portion of the fixing part to close the opening of the peripheral wall portion, The peripheral wall portion has a horizontal portion disposed in a horizontal direction and a pair of adjacent portions adjacent to both ends of the horizontal portion, a recessed portion is formed at the connecting portion between the bottom wall portion and the peripheral wall portion, the recessed portion being recessed toward the inside of the water-passing component and being surrounded on all sides by the end portion of the horizontal portion on the lid portion side, both end portions of the horizontal portion on the pair of adjacent portion sides, and the outer surface of the housing; The recessed portion has a mounting surface that is continuous with the interface between the outer surface of the housing and the bottom wall portion, and the bottom wall portion is brazed to the outer surface of the housing by placing a brazing material on the mounting surface and heating the brazing material.

2. the recessed portion has a stepped surface that is continuous with the interface between the outer circumferential surface of the lid portion and the inner circumferential surface of the peripheral wall portion, The heat exchanger according to claim 1 , wherein the open end of the lid portion on the housing side is capable of abutting against the stepped surface when the lid portion is fitted into the peripheral wall portion of the fixing portion.

3. The fixing portion is formed in a shape that is symmetrical in the vertical direction, 3. The heat exchanger according to claim 1, wherein the fixing portion has a plurality of recesses formed at positions that are symmetrical in the up-down direction.

4. Burner and a primary heat exchanger, which is the heat exchanger according to any one of claims 1 to 3, provided in communication with the burner and through which combustion exhaust gas from the burner passes; a secondary heat exchanger provided in series with the primary heat exchanger and through which combustion exhaust gas from the primary heat exchanger passes.

Images