Primary heat exchanger and water heater

Abstract

To prevent a guide member from falling during a brazing process.SOLUTION: A primary heat exchanger 5 includes an inner casing 20, a plurality of heat transfer fins 21, a plurality of heat transfer pipes 22, and a guide member 70. In the primary heat exchanger 5, the guide member 70 includes: a plate portion 71 disposed along an inner face of the inner casing 20 and extending in a second direction; an extension portion 73 extending from an upstream-side end portion of the plate portion 71 toward an inner side of the inner casing 20 in a combustion exhaust flowing direction; and an inclined plate portion 72 inclined toward the inner side of the inner casing 20 from a downstream-side end portion of the plate portion 71 as approaching a downstream side. As the extension portion 73 is held between an inner face of the inner casing 20 and the heat transfer fin 21 closest to the inner face, the plate portion 71 is held in a state of being kept into close contact with the inner face of the inner casing 20.SELECTED DRAWING: Figure 14

Description

Technical Field

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

Background Art

[0002] Conventionally, as a heat exchanger used in a water heater, a primary heat exchanger and a secondary heat exchanger described in Japanese Patent Application Laid-Open No. 2020-169758 (hereinafter referred to as Patent Document 1) are known. This primary heat exchanger includes a rectangular cylindrical middle casing to which a burner is attached, a plurality of fins arranged side by side in the left-right direction inside the middle casing, and a plurality of heat transfer tubes penetrating each fin in the left-right direction. The middle casing has a first wall portion and a second wall portion facing the first wall portion in the left-right direction. A plurality of through holes for passing each heat transfer tube are provided in the first wall portion and the second wall portion, respectively. The plurality of fins each have a through hole for passing the heat transfer tube. Each heat transfer tube is fixed to the middle casing in a posture where both ends thereof slightly protrude outside the first wall portion and the second wall portion.

[0003] On the other hand, the secondary heat exchanger includes a rectangular cylindrical lower casing communicating with the middle casing, and a plurality of pair plates arranged side by side at a predetermined interval in the thickness direction inside the lower casing. The pair plate is formed by joining a pair of heat transfer plates facing each other. In the central portion of each heat transfer plate, a plurality of inclined ridges protrude in parallel. An internal flow path that zigzags through the ridges is formed in each pair plate. Further, an exhaust passage through which combustion exhaust flows is formed between adjacent pairs of ridges between adjacent pairs of pair plates.

[0004] The combustion exhaust from the burner passes between the fins in the middle casing of the primary heat exchanger, exchanging heat with the hot water flowing through the heat transfer tubes and recovering sensible heat. After passing between the fins, the combustion exhaust enters the lower casing of the secondary heat exchanger. At this time, guide members on both the left and right sides of the middle casing guide the exhaust towards the area where the internal flow path is formed in the lower casing (exhaust passage side). Therefore, most of the combustion exhaust passes through the exhaust passage, where it exchanges heat with the water flowing through the internal flow path and recovers latent heat.

[0005] The guide members described above are provided in pairs on both the left and right sides of the inner casing, below the fins and heat transfer tubes. Each guide member comprises an upper plate portion extending upward and an inclined plate portion extending laterally downward from the lower end of the upper plate portion. The combustion exhaust is guided towards the exhaust passage by the inclined plate portion. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-169758 [Overview of the project] [Problems that the invention aims to solve]

[0007] Incidentally, in the primary heat exchanger described above, mounting pieces are formed upward at both the front and rear ends of the inclined plate section for fixing to the front and rear inner surfaces of the inner casing. Since the mounting pieces need to be fixed to the front and rear inner surfaces of the inner casing with screws or rivets, the workability is poor. Therefore, in order to improve workability, it is desirable to fix them simultaneously with other parts, for example by furnace brazing, instead of fixing them with screws or rivets.

[0008] However, the guide member has an inclined plate section that slopes inward, causing the center of gravity to be shifted inward. Furthermore, since the brazing process is performed in an inverted configuration compared to the normal arrangement, the guide member is temporarily fixed with the upper plate section positioned above the heat transfer tube, and the inclined plate section extending laterally from the upper end of the upper plate section upwards. Therefore, there is a concern that the guide member may tip inward during the brazing process.

[0009] The present invention was completed based on the circumstances described above, and aims to provide a primary heat exchanger and a water heater that can prevent the guide member from tipping over during the brazing process. [Means for solving the problem]

[0010] The primary heat exchanger of this disclosure is provided with a burner on the upstream side and a secondary heat exchanger on the downstream side, and is capable of recovering the sensible heat of combustion exhaust gas from the burner by passing through the burner, and comprises a rectangular cylindrical housing having a first wall portion and a second wall portion facing each other, and a third wall portion and a fourth wall portion fixed between the first wall portion and the second wall portion, and a plurality of heat transfer fins having through holes penetrating in the thickness direction, the thickness direction facing a first direction connecting the first wall portion and the second wall portion, and the longitudinal direction facing a second direction connecting the third wall portion and the fourth wall portion, arranged in the first direction, and the plurality of heat transfer fins penetrating the through holes in the first direction, with both ends in the first direction being the first The primary heat exchanger comprises a plurality of heat transfer tubes fixed to a wall and a second wall, respectively, and a guide member attached to the inner surface of the housing for guiding the combustion exhaust that has passed through the heat transfer fins toward the secondary heat exchanger, wherein the guide member comprises a plate portion arranged along the inner surface of the housing and extending in the second direction, an extension portion extending from the upstream end of the plate portion toward the inside of the housing in the direction of passage of the combustion exhaust, and an inclined plate portion provided at an angle from the downstream end of the plate portion toward the inside of the housing as it moves downstream, wherein the extension portion is sandwiched between the inner surface of the housing and the heat transfer fin closest to that inner surface, thereby holding the plate portion in close contact with the inner surface of the housing. [Effects of the Invention]

[0011] According to the present invention, it is possible to prevent the guide member from tipping over during the brazing process. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a front view of the water heater with the front cover removed. [Figure 2] Figure 2 is a front view of a water heater with the resin sheet, controller, and display / operation panel omitted. [Figure 3] Figure 3 is a front view of the inner casing shown in Figure 2. [Figure 4] Figure 4 is a left side view of the inner casing shown in Figure 2. [Figure 5] Figure 5 is a left side view of the inner cylinder with the lid omitted from the left water collecting part and the lower water collecting part of Figure 4. [Figure 6] Figure 6 is a perspective view of the inner cylinder of Figure 2 seen from the front left obliquely. [Figure 7] Figure 7 is a perspective view of the inner cylinder of Figure 2 seen from the rear right obliquely. [Figure 8] Figure 8 is a plan view of the inner cylinder of Figure 2. [Figure 9] Figure 9 is a perspective view of the primary heat exchanger seen from the lower right obliquely. [Figure 10] Figure 10 is a sectional view taken along the line A-A of Figure 8. [Figure 11] Figure 11 is a sectional view taken along the line C-C of Figure 8, and is an enlarged sectional view showing the primary heat exchanger enlarged. [Figure 12] Figure 12 is a sectional view taken along the line B-B of Figure 8, and is an enlarged sectional view showing the guide member enlarged. [Figure 13] Figure 13 is a perspective view showing the state of brazing the guide member to the middle casing. [Figure 14] Figure 14 is an enlarged sectional view showing the state of brazing the guide member to the middle casing enlarged. [Figure 15] Figure 15 is a perspective view of the guide member.

Embodiments for Carrying out the Invention

[0013] Hereinafter, embodiments of the present disclosure will be listed and exemplified. (1) The primary heat exchanger of the present disclosure is a primary heat exchanger in which a burner is provided in series on the upstream side and a secondary heat exchanger is provided in series on the downstream side, and the sensible heat of the combustion exhaust gas can be recovered by passing the combustion exhaust gas from the burner. It has a rectangular tube-shaped housing having a first wall portion and a second wall portion facing each other, and a third wall portion and a fourth wall portion fixed between the first wall portion and the second wall portion. It has through holes penetrating in the thickness direction, the thickness direction faces the first direction connecting the first wall portion and the second wall portion, and the longitudinal direction faces the second direction connecting the third wall portion and the fourth wall portion. A plurality of heat transfer fins arranged side by side in the first direction, a plurality of heat transfer tubes penetrating the through holes of the plurality of heat transfer fins in the first direction, and both ends in the first direction being fixed to the first wall portion and the second wall portion respectively, and a guide member attached to the inner surface of the housing for guiding the combustion exhaust gas that has passed through the heat transfer fins toward the secondary heat exchanger. The guide member includes a plate portion arranged along the inner surface of the housing and extending in the second direction, an extension portion extending from the upstream end portion of the plate portion toward the inside of the housing in the passing direction of the combustion exhaust gas, and an inclined plate portion provided to incline toward the inside of the housing as it goes downstream from the downstream end portion of the plate portion. The primary heat exchanger is such that the plate portion is held in close contact with the inner surface of the housing by the extension portion being sandwiched between the inner surface of the housing and the heat transfer fin closest to the inner surface.

[0014] To fix the guide member to the inner surface of the housing, instead of fixing it with screws or rivets, for example, it is desirable from the viewpoint of workability to fix it simultaneously by furnace brazing together with other parts. To perform brazing, with the housing in a posture where the downstream side faces upward, a brazing material is placed near the boundary between the inclined plate portion and the inner surface of the housing. Therefore, the guide member needs to hold the plate portion in close contact with the inner surface of the housing in a posture where the extension portion is arranged on the lower side, the inclined plate portion is arranged on the upper side, and the extension portion and the inclined plate portion face the inside of the housing (that is, an upside-down posture).

[0015] Therefore, with the above-described primary heat exchanger, by inserting the extended portion between the inner surface of the housing and the heat transfer fin closest to that inner surface, the extended portion is sandwiched between the inner surface of the housing and the heat transfer fin closest to that inner surface, and the plate portion is held in an upright position so as to be in close contact with the inner surface of the housing. Thus, it is possible to prevent the guide member from tipping over into the inside of the housing if it is inverted during the brazing process.

[0016] (2) The extended portion has a plurality of positioning portions that extend in a curved shape along the outer surface of the heat transfer tube, and it is preferable that the central portion of the positioning portion in the second direction is recessed toward the inclined plate portion. When assembling the guide member to the heat transfer tube from above, the extended portion fits into the outer surface of the heat transfer tube, making it easier to position the guide member in the second direction. Furthermore, it is possible to reliably prevent the guide member from tipping over into the inside of the housing after it has been assembled to the heat transfer tube.

[0017] (3) The guide member further comprises a pair of support pieces provided at both ends of the plate portion or the inclined plate portion, wherein a part of the pair of support pieces is in contact with the heat transfer fin when the extended portion is sandwiched between the inner surface of the housing and the heat transfer fin closest to the inner surface, and the plate portion is held in close contact with the inner surface of the housing. If the guide member is inverted during the brazing process, a portion of the pair of support pieces will contact the heat transfer fins from above, thus more reliably preventing the guide member from tipping over into the housing.

[0018] (4) The water heater of the present disclosure includes a burner, a primary heat exchanger connected to the burner and capable of recovering the sensible heat of the combustion exhaust from the burner by passing the exhaust through it, and a secondary heat exchanger connected to the primary heat exchanger and capable of recovering the latent heat of the combustion exhaust from the primary heat exchanger by passing the exhaust through it. With this type of water heater, it is possible to prevent the guide member from tipping over into the inside of the housing if it is inverted during the brazing process.

[0019] <Embodiment> Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a front view of the water heater 1, with the front cover removed. Figure 2 shows the water heater 1 from Figure 1, but with the resin sheet 16, controller 12, and display / operation panel 13 removed.

[0020] [Overall structure of a water heater] This water heater 1 is a downward combustion type, with a burner 4, a primary heat exchanger 5, and a secondary heat exchanger 6 arranged in order from top to bottom within a rectangular box-shaped housing 2 with an open front. The burner 4 generates a downward combustion flame. The housing 2 also contains an exhaust section 7 that wraps around from the bottom of the inner body 3 towards 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 connected to the fan unit 8 below the fan unit 8, to which fuel gas is supplied from a gas inlet pipe 11 via a gas governor 9. A controller 12 containing an electrical circuit board is mounted horizontally on the lower right side of the inner body 3, and a display and operation panel 13 exposed from the front cover is located in the lower center of the controller 12.

[0021] [Burner] The burner 4 is a fully primary air type in which a mixture of fuel gas and all the combustion air necessary for combustion is burned. It has an upper casing 14 that is horizontally elongated in plan view, with openings on the top and bottom surfaces and 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 a fan unit 8 is connected.

[0022] [Primary heat exchanger] As shown in Figures 6 to 8, the primary heat exchanger 5 comprises a rectangular cylindrical inner casing 20 to which the burner 4 is attached, a plurality of heat transfer fins 21, 21... (only a portion is shown in each figure) arranged at predetermined intervals in the left-right direction, which is the thickness direction, and a heat transfer tube 22 that penetrates each heat transfer fin 21 in the left-right direction. The heat transfer fins 21 have through holes 35 that penetrate in the thickness direction, and a plurality of them are arranged in the left-right direction with the thickness direction facing left-right and the longitudinal direction facing front-back. The primary heat exchanger 5 is made of stainless steel. The inner casing 20 is a rectangular cylindrical shape that penetrates in the vertical direction. The inner casing 20 is an example of a housing.

[0023] The central casing 20 has a left side wall portion 31 and a right side wall portion 32 that face each other in the left-right direction, and a front side wall portion 41 and a rear side wall portion 42 that face each other in the front-rear direction. As shown in Figure 5, the left side wall portion 31 and the right side wall portion 32 are each provided with a plurality of holes 33. The ends of a plurality of heat transfer tubes 22 are arranged to pass through each hole 33. The ends of each heat transfer tube 22 are fixed to the inner surface of each hole 33. The left-right direction is an example of a first direction, and the front-rear direction is an example of a second direction. Furthermore, the left side wall portion 31 is an example of a first wall portion, the right side wall portion 32 is an example of a second wall portion, the front side wall portion 41 is an example of a third wall portion, and the rear side wall portion 42 is an example of a fourth wall portion.

[0024] As shown in Figure 6, the heat transfer tubes 22 include eight straight, large-diameter tubes 23, 23... with an elliptical cross-section and a major axis in the vertical direction, arranged at predetermined intervals in the front-rear direction at the lowest stage, and three straight, small-diameter tubes 24, 24... with a circular cross-section, arranged at predetermined intervals in the vertical direction on the front and rear outer surfaces of the upper wall portion 20b of the middle casing 20, respectively. The large-diameter tubes 23 pass through the through holes 35 of the multiple heat transfer fins 21 in the left-right direction, and both ends in the left-right direction are fixed to the left wall portion 31 and the right wall portion 32, respectively.

[0025] As shown in Figure 8, the large-diameter pipe 23 is connected to two adjacent ends alternately on the left and right by lower water collection sections 25 provided on both walls 31 and 32 of the central casing 20, forming a meandering shape that connects the entire pipe into one. Below the heat transfer fins 21 on both walls 31 and 32 of the central casing 20, a pair of guide members 70, 70 are provided to guide the combustion exhaust toward the center of the secondary heat exchanger 6.

[0026] The left side wall 31 of the middle casing 20 is provided with a left-side water collection section 28 that connects the left ends of the three front and rear small-diameter pipes 24. As shown in Figure 7, the right end of the rearmost large-diameter pipe 23 is connected to a connecting pipe 26 to the secondary heat exchanger 6, and the right end of the foremost large-diameter pipe 23 is connected to the right ends of the three front small-diameter pipes 24 by a front water collection section 27 that extends vertically. The right side wall 32 of the middle casing 20 is provided with a right-side water collection section 29 that connects the right ends of the three rear small-diameter pipes 24, and the hot water outlet pipe 30 is connected to the right-side water collection section 29.

[0027] Therefore, in the heat transfer tubes 22 of the primary heat exchanger 5, the hot water that flows from the connecting tube 26 to the last large-diameter tube 23 flows forward in a meandering manner, passing alternately through the lowest large-diameter tubes 23, 23..., and then flows from the frontmost large-diameter tube 23 through the three small-diameter tubes 24 on the front side and the three small-diameter tubes 24 on the rear side in order to the hot water outlet tube 30.

[0028] As shown in Figure 1, a strip-shaped resin sheet 16, with a conductive pattern that serpentinely covers almost the entire upper outer circumference of the inner casing 20, is wound around it, making it possible to detect leakage of combustion exhaust from the inner casing 20. As shown in Figure 5, a turbulence plate 23a is inserted into each large-diameter pipe 23 to agitate the hot water passing through it.

[0029] As shown in Figures 11 and 12, the heat transfer fin 21 has a body that is a horizontally elongated plate shape extending in the front-to-back direction. Eight elliptical through holes 35, 35·· are formed in the body of the heat transfer fin 21. Each through hole 35 is arranged in a row in the front-to-back direction at equal intervals. A burring portion 36 that protrudes to the left is formed on the inner edge of each through hole 35 by burring processing.

[0030] An upper notch 37 is formed between each through-hole 35 on the upper side of the heat transfer fin 21 body. The upper notch 37 has a curved inner edge that follows the outer surface shape of the front and rear through-holes 35, 35. The inner edge of the upper notch 37 is V-shaped, with the distance between the front and rear decreasing as it goes downwards. The lower end of the upper notch 37 is located slightly below the center in the major axis direction of the through-hole 35.

[0031] The front and rear ends of the main body of the heat transfer fin 21 are formed with edge portions 39, 39 that abut against the inner surface of the lower wall portion 20a of the middle casing 20. Each edge portion 39 extends in the vertical direction and is folded back to the left.

[0032] [Detailed structure of the guide member] As shown in Figure 8, a pair of guide members 70 are provided, attached to the right wall 32 and the left wall 31 of the primary heat exchanger 5. The pair of guide members 70 are identical in shape and arranged symmetrically. In Figure 15, the guide member 70 attached to the right wall 32 is described as representative, and the guide member 70 attached to the left wall 31 is not described.

[0033] The guide member 70 has a shape that extends in the front-to-back direction as a whole and is made of a metal plate. The guide member 70 comprises a plate portion 71 that extends upward, an inclined plate portion 72 that extends to the left as it goes downward from the lower end of the plate portion 71, a pair of mounting pieces 75, 75 that extend upward from both the front and rear ends of the inclined plate portion 72, and an extended portion 73 that extends to the left from the upper end of the plate portion 71. The mounting pieces 75, 75 are formed by bending both the left and right ends of the inclined plate portion 72 upward.

[0034] As shown in Figure 12, the plate portion 71 is positioned along the inner surface 20c of the middle casing 20. The upper end of the plate portion 71 is located at the upstream end in the direction of combustion exhaust passage. The extension portion 73 is positioned perpendicular to the inner surface 20c of the middle casing 20 and is provided extending from the upstream end of the plate portion 71 toward the inside of the middle casing 20. The inclined plate portion 72 is inclined toward the inside of the middle casing 20 as it moves downstream from the downstream end of the plate portion 71.

[0035] As shown in Figure 10, the guide member 70 is mounted with its plate portions 71, 71 facing each other, with its extension portion 73 positioned further outward from the heat transfer fins 21 located at both the left and right ends, and the upper surface of the extension portion 73 in contact with each of the large-diameter pipes 23, 23. The extension portion 73 is inserted and clamped between the inner surface 20c of the middle casing 20 and the heat transfer fin 21 closest to the inner surface 20c (hereinafter sometimes referred to as the "insertion portion 38"). More specifically, as shown in Figure 10, the left guide member 70 is clamped between the inner surface 20c of the left wall portion 31 and the end face of the burring portion 36 of the heat transfer fin 21, while the right guide member 70 is clamped between the inner surface 20c of the right wall portion 32 and the right side of the main body of the heat transfer fin 21 (the side on which the burring portion 36 is not formed). As a result, the plate portions 71, 71 are held in a state where they rest on the upper surface of the heat transfer fins 21 and are in close contact with the inner surfaces 20c, 20c of the inner casing 20. The "upper surface" of the heat transfer fins 21 referred to here is the upper surface when the inner casing 20 is positioned upside down during the brazing process in the manufacturing of the water heater 1 (see Figures 13, 14), and is the lower surface in the finished product state (the normal operating state where the inner casing 20 is not inverted; for example, see Figures 1-7, 12). In this state, the molten brazing material P flows between the plate portions 71, 71 and the inner surfaces 20c, 20c of the inner casing 20, and the plate portions 71, 71 are joined to the inner surfaces 20c, 20c of the inner casing 20 by brazing. At the same time, the front and rear mounting pieces 75, 75 are also joined to the inner surfaces 20c, 20c of the inner casing 20 by brazing.

[0036] Each inclined plate portion 72 of the left and right guide members 70 extends downward as it moves towards the center in the left-right direction below the heat transfer fins 21, and extends in the front-rear direction at both ends of the left and right heat transfer plates 56 of the secondary heat exchanger 6, positioned above the inlet 58 and outlet 59, respectively. Therefore, the combustion exhaust flowing downward along the left and right inner surfaces 20c, 20c of the middle casing 20 passes the lower end of the heat transfer fins 21, and is then guided towards the center from the inside of the plate portions 71, 71 along the inclined plate portions 72, 72 toward the secondary heat exchanger 6, and flows into the exhaust passage 57a. As shown in Figures 11 and 12, the portion of the inclined plate portion 72 corresponding to the secondary heat exchanger 6 has a folded portion 76 formed by folding back the tip.

[0037] As shown in Figure 15, the extension 73 has a plurality of positioning sections 74 that are curved downward at equal intervals in the front-rear direction. The central part of each positioning section 74 in the front-rear direction is recessed toward the inclined plate section 72. Each positioning section 74 is provided corresponding to the position of each large-diameter pipe 23. Therefore, when the guide member 70 is attached to the middle casing 20, as shown in Figure 12, the positioning sections 74 are arranged along the outer circumferential surface of the large-diameter pipe 23 and are held in contact with it.

[0038] [Method for attaching guide members] In this primary heat exchanger 5, the plate portion 71 of the guide member 70 is attached to the inner surface 20c of the middle casing 20 by brazing, as described above. In the following description, an example will be given in which one of the pair of left and right guide members 70 is attached to the inner surface 20c of the left wall portion 31 of the middle casing 20, and the other is attached to the inner surface 20c of the right wall portion 32.

[0039] First, to perform brazing, the middle casing 20 is positioned so that the downstream side faces upward, as shown in Figure 13. Next, one guide member 70 is placed on the outer surface of each large-diameter pipe 23 from above in an inverted position. As shown in Figure 14, when the extension portion 73 is inserted into the insertion portion 38, the extension portion 73 is held between the inner surface 20c of the left wall portion 31 and the end face of the burring portion 36 of the heat transfer fin 21. Similarly, the extension portion 73 of the other guide member 70 is held between the inner surface 20c of the right wall portion 32 and the body of the heat transfer fin 21. As a result, the plate portion 71 of each guide member 70 is held in an upright position so as to be in close contact with the inner surface 20c of the left wall portion 31 or the right wall portion 32.

[0040] When assembling the guide member 70 to each large-diameter pipe 23 from above, the positioning portions 74 of the extended portion 73 fit into the outer surface of each large-diameter pipe 23, making it easier to position the guide member 70 in the front-rear direction. Furthermore, since the extended portion 73 is formed to have a predetermined length in the left-right direction, it is possible to prevent the guide member 70 from tipping over into the inner casing 20 after it has been assembled to each large-diameter pipe 23. In addition, since the pair of mounting pieces 75 are in contact with the heat transfer fins 21 from above, this also prevents the guide member 70 from tipping over into the inner casing 20.

[0041] Next, as shown in Figure 14, brazing is performed by placing brazing material P near the boundary between the inclined plate portion 72 and the inner surface 20c of the inner casing 20 and heating it in a furnace. The molten brazing material P then flows along the inclined plate portion 72 and spreads to the interface between the inner surface 20c of the inner casing 20 and the plate portion 71 by capillary action. Once the brazing material P solidifies, the inner surface 20c of the inner casing 20 and the plate portion 71 can be evenly fixed.

[0042] [Secondary heat exchanger] The secondary heat exchanger 6 is installed in conjunction with the primary heat exchanger 5 and, as shown in Figure 10, comprises a rectangular cylindrical lower casing 55 that communicates with the middle casing 20, and a plurality of heat transfer plates 56, 56... arranged side by side within the lower casing 55. Each heat transfer plate 56 has a horizontally elongated rectangular shape when viewed from the front. Multiple inclined protrusions 57 are provided parallel to each other in the central part of each heat transfer plate 56. By joining a pair of heat transfer plates 56 facing each other, an internal flow path is formed in which exhaust gas flows in a zigzag pattern within the opposing pair of protrusions 57, 57, and an exhaust passage 57a is formed between adjacent pairs of protrusions 57, 57 through which combustion exhaust gas flows in an inclined manner.

[0043] As shown in Figure 3, an inlet 58 connected to the internal flow path 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 is provided at the upper front side of the lower casing 55, and a connecting pipe 26 is connected to this outlet 59.

[0044] 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 the neutralizer 64 via a drain discharge pipe 63.

[0045] The exhaust duct 62 is a horizontally elongated rectangular tube made of synthetic resin, and an upper cover 65, which has a cylindrical exhaust pipe section 66 that protrudes from the upper surface of the housing 2, is attached to the opening at the upper end of the exhaust duct 62.

[0046] [Water heater operation instructions] In the water heater 1 configured as described above, when water is supplied to the appliance, the controller 12 drives the fan motor to rotate the fan at a rotation speed corresponding to the amount of combustion requested by the remote control, etc. Then, the fan unit 8 draws in air in proportion to the rotation speed of the fan. At the same time, fuel gas is supplied from the gas inlet pipe 11, and after being pressurized by the gas governor 9, it is mixed with air in the gas supply unit 10 via a venturi installed on the intake side of the fan unit 8 to produce a fuel mixture. The produced fuel mixture is discharged from the outlet of the fan case into the chamber 15 of the burner 4, supplied into the upper casing 14, ejected from each flame hole in the flame hole plate, ignited by the ignition electrode, and combusted.

[0047] The combustion exhaust from the burner 4 passes between the heat transfer fins 21, 21 in the central casing 20 of the primary heat exchanger 5, exchanging heat with the hot water flowing through the heat transfer tubes 22, and recovering sensible heat. Within the heat transfer tubes 22, the hot water is agitated by the turbulence plates 32 in each large-diameter tube 23, which reduces stagnation and temperature unevenness.

[0048] Next, the combustion exhaust from the primary heat exchanger 5 passes between the heat transfer plates 56, 56 in the lower casing 55 of the secondary heat exchanger 6, exchanging heat with the water flowing through the internal passages, and latent heat is recovered.

[0049] The combustion exhaust 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 through 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.

[0050] [Effects of the Embodiment] To fix the guide member 70 to the inner surface 20c of the middle casing 20, it is preferable from the viewpoint of workability to fix it simultaneously with other parts, for example, by furnace brazing, rather than fixing it with screws or rivets. To perform brazing, the middle casing 20 is positioned with the downstream side facing upwards, the guide member 70 is inverted and placed on the outer surface of the large-diameter pipe 23, and the brazing material P is placed near the boundary between the inclined plate portion 72 and the inner surface 20c of the middle casing 20. Therefore, the guide member 70 needs to be held in a state where the extended portion 73 is positioned on the lower side, the inclined plate portion 72 is positioned on the upper side, and the extended portion 73 and the inclined plate portion 72 are facing inwards to the middle casing 20 (inverted position), with the plate portion 71 in close contact with the inner surface 20c of the middle casing 20.

[0051] Therefore, with the primary heat exchanger 5 described above, by inserting the extension portion 73 into the insertion portion 38, the extension portion 73 is sandwiched between the inner surface 20c of the middle casing 20 and the heat transfer fin 21 closest to the inner surface 20c, so that the plate portion 71 is held in an upright position so that it is in close contact with the inner surface 20c of the middle casing 20. Thus, it is possible to prevent the guide member 70 from tipping over into the inside of the middle casing 20 if it is inverted during the brazing process.

[0052] When assembling the guide member 70 onto the large-diameter pipe 23 from above, the extended portion 73 fits into the outer surface of the large-diameter pipe 23, making it easier to position the guide member 70 in the front-rear direction. Furthermore, after assembling the guide member 70 onto the large-diameter pipe 23, it is possible to reliably prevent the guide member 70 from tipping over into the inner casing 20.

[0053] If the guide member 70 is inverted during the brazing process, a portion of the pair of mounting pieces 75, 75 will contact the heat transfer fins 21 from above, thus more reliably preventing the guide member 70 from tipping over into the inner casing 20.

[0054] [Other embodiments] In the above embodiment, an example was shown in which the extended portion 73 has a plurality of positioning portions 74 corresponding to each large-diameter pipe 23. However, the extended portion may not have positioning portions and may be formed in a flat plate shape extending in the front-rear direction.

[0055] In the above embodiment, an example was shown in which the extended portion 73 has a positioning portion 74 formed in a curved shape along the outer surface of the large-diameter pipe 23. However, the positioning portion does not have to be in a curved shape along the outer surface of the large-diameter pipe 23, and may be an insertion piece that fits between a pair of adjacent large-diameter pipes 23.

[0056] In the above embodiment, mounting pieces 75, 75 are provided at both the front and rear ends of the inclined plate portion 72, but mounting pieces may also be provided at both the front and rear ends of the plate portion 71.

[0057] In addition, common to all inventions, the configurations of the burner, primary heat exchanger, and secondary heat exchanger, as well as the arrangement of the fan unit and controller, can be modified as appropriate. The secondary heat exchanger is not required, nor is the combustion type downward.

[0058] Furthermore, in the primary heat exchanger, the number of large-diameter tubes can be changed as appropriate, and it is also acceptable to have a configuration without small-diameter tubes as heat transfer tubes. If the cross-sectional shape is elliptical as in the above embodiment, the dimensions in the short axis direction will be compact, but other shapes can also be used. The orientation of the heat transfer fins and heat transfer tubes may also be reversed from that of the above embodiment, and the heat transfer fins and heat transfer tubes may be provided in multiple stages instead of just one.

[0059] Furthermore, although the fan unit is a premixed type that supplies a mixture of fuel gas and combustion air to the chamber, the invention is not limited to this, and each invention 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]

[0060] 1: Water heater 2: Housing 3: Inner casing 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 (casing) 20a: Lower wall 20b: Upper wall 20c: Inner surface 21: Heat transfer fin 22: Heat transfer tube 23: Large diameter tube 23a: Turbulence plate 23b: End 24: Small diameter tube 25: Lower water collection section (water passage parts) 26: Connection pipe 27: Front water collection section 28: Left water collection section 29: Right side water collection section 30: Hot water outlet pipe 31: Left side wall section (first wall section) 32: Right side wall section (second wall section) 33: Hole section 35: Through hole 36: Burring section 37: Upper notch section 38: Insertion section 39: Edge section 41: Front side wall section (third wall section) 42: Back side wall section (fourth wall section) 55: Lower casing 56: Heat transfer plate 57: Protrusion 57a: Exhaust passage 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 section 70: Guide member 71: Plate section 72: Inclined plate section 73: Extension section 74: Positioning section 75: Mounting piece (support piece) 76: Folded section P: wax

Claims

1. a primary heat exchanger having a burner on an upstream side and a secondary heat exchanger on a downstream side, the primary heat exchanger being capable of recovering sensible heat of the combustion exhaust gas by the combustion exhaust gas passing through the primary heat exchanger; a rectangular cylindrical housing having a first wall portion and a second wall portion facing each other, and a third wall portion and a fourth wall portion fixed between the first wall portion and the second wall portion; a plurality of heat transfer fins each having a through hole penetrating in a thickness direction, the thickness direction facing a first direction connecting the first wall portion and the second wall portion, and the longitudinal direction facing a second direction connecting the third wall portion and the fourth wall portion, the heat transfer fins being arranged side by side in the first direction; a plurality of heat transfer tubes that pass through the through holes of the plurality of heat transfer fins in the first direction and have both end portions in the first direction fixed to the first wall portion and the second wall portion, respectively; a guide member attached to an inner surface of the housing and guiding the combustion exhaust gas that has passed through the heat transfer fins toward the secondary heat exchanger, the guide member includes a plate portion disposed along the inner surface of the housing and extending in the second direction, an extension portion extending from an upstream end of the plate portion toward the inside of the housing in the passage direction of the combustion exhaust gas, and an inclined plate portion inclined toward the inside of the housing as it moves downstream from the downstream end of the plate portion, A primary heat exchanger in which the extension portion is sandwiched between the inner surface of the housing and the heat transfer fin closest to the inner surface, thereby maintaining the plate portion in close contact with the inner surface of the housing.

2. 2. The primary heat exchanger according to claim 1, wherein the extension portion has a plurality of positioning portions formed in a curved shape extending along the outer peripheral surface of the heat transfer tube, and the central portion of each positioning portion in the second direction is recessed toward the inclined plate portion.

3. The guide member further includes a pair of support pieces provided at both ends of the plate portion or the inclined plate portion, 3. A primary heat exchanger as described in claim 1, wherein a portion of the pair of support pieces abuts against the heat transfer fin when the extension portion is sandwiched between the inner surface of the housing and the heat transfer fin closest to the inner surface and the plate portion is held in close contact with the inner surface of the housing.

4. Burner and the primary heat exchanger according to any one of claims 1 to 3, which is provided in communication with the burner and is capable of recovering sensible heat from the combustion exhaust gas when the combustion exhaust gas passes through the primary heat exchanger; a secondary heat exchanger that is connected to the primary heat exchanger and that can recover latent heat from the combustion exhaust gas when the combustion exhaust gas from the primary heat exchanger passes through the secondary heat exchanger.

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