Water heater

Abstract

To improve thermal efficiency of a secondary heat exchanger of a water heater.SOLUTION: A water heater 1 includes: a primary heat exchanger 10; a secondary heat exchanger 20 disposed on an upper side of the primary heat exchanger 10; and a passage member 50 connecting the primary heat exchanger 10 and the secondary heat exchanger 20 and introducing a combustion exhaust gas discharged from the primary heat exchanger 10 into the secondary heat exchanger 20. In the water heater 1, the secondary heat exchanger 20 includes: a plurality of heat transfer pipes 21; and a casing 22 in which the plurality of heat transfer pipes 21 is disposed. A gas inlet 28 is formed on a rear wall part 23C of the casing 22, and the passage member 50 is mounted to a peripheral edge part of the gas inlet 28. The casing 22 includes a drifting member 32 for inhibiting the combustion exhaust gas introduced from the gas inlet 28 into the casing 22 from flowing upward.SELECTED DRAWING: Figure 16

Description

Technical Field

[0001] The present disclosure relates to a water heater.

Background Art

[0002] Conventionally, a latent heat recovery type water heater including a primary heat exchanger for sensible heat recovery, a secondary heat exchanger for latent heat recovery, and a path member connecting these heat exchangers has been known. For example, the secondary heat exchanger described in Japanese Patent Application Laid-Open No. 2020-165638 (Patent Document 1 below) includes a box body and a plurality of heat transfer tubes disposed in the box body through which hot water flows. An inlet portion through which combustion exhaust gas flows is provided in the rear wall portion of the box body, and an outlet portion through which combustion exhaust gas is discharged is provided in the front wall portion of the box body. The heat transfer tubes include six linear tube portions extending in the left-right direction and five bent portions connecting the ends of adjacent linear tube portions. The plurality of heat transfer tubes are stacked in the vertical direction in the housing, and the linear tube portions are arranged in a large number at intervals in the vertical and front-rear directions. The path member has its lower end fixed to the upper end of the primary heat exchanger and its upper end fixed to the peripheral edge of the inlet portion of the secondary heat exchanger. According to such a water heater, the combustion exhaust gas from which sensible heat has been recovered by the primary heat exchanger rises in the path member and is introduced into the secondary heat exchanger from the rear of the secondary heat exchanger. Then, when the combustion exhaust gas introduced into the secondary heat exchanger passes near the linear tube portion, it transfers heat to the water flowing through the linear tube portion and heats the water.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above configuration, the combustion exhaust gas flows upward within the path member and is introduced into the secondary heat exchanger, so it tends to flow upward as it is. Furthermore, the combustion exhaust gas is at a high temperature of about 200°C. Therefore, when the combustion exhaust gas is introduced into the secondary heat exchanger, it tends to flow toward the upper side of the casing. For this reason, in the vicinity of the inlet portion where the diffusion of the combustion exhaust gas is small, there is a problem that the combustion exhaust gas flows concentratedly near the linear pipe portion disposed on the upper side and cannot effectively transfer heat to the linear pipe portion on the lower side.

[0005] The present disclosure has been completed based on the above circumstances, and an object thereof is to improve the thermal efficiency of the secondary heat exchanger of the water heater.

Means for Solving the Problems

[0006] The water heater of the present disclosure includes a primary heat exchanger, a secondary heat exchanger disposed above the primary heat exchanger, and a path member that connects the primary heat exchanger and the secondary heat exchanger and introduces the combustion exhaust gas discharged from the primary heat exchanger into the secondary heat exchanger. The secondary heat exchanger includes a plurality of heat transfer pipes and a casing in which the plurality of heat transfer pipes are disposed. A gas inlet is formed in the rear wall portion of the casing, the path member is attached to the peripheral edge of the gas inlet, and the casing is provided with a flow deviation member that suppresses the upward flow of the combustion exhaust gas introduced into the casing from the gas inlet.

Effects of the Invention

[0007] According to the present disclosure, the thermal efficiency of the secondary heat exchanger of the water heater can be improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be listed and exemplified. (1) The water heater of the present disclosure includes a primary heat exchanger, a secondary heat exchanger disposed above the primary heat exchanger, and a path member that connects the primary heat exchanger and the secondary heat exchanger and introduces the combustion exhaust gas discharged from the primary heat exchanger into the interior of the secondary heat exchanger. The secondary heat exchanger includes a plurality of heat transfer tubes and a housing in which the plurality of heat transfer tubes are disposed. A gas inlet is formed in the rear wall portion of the housing, and the path member is attached to the peripheral edge of the gas inlet. The housing is provided with a flow deviation member that suppresses the upward flow of the combustion exhaust gas introduced into the interior of the housing from the gas inlet.

[0010] According to such a configuration, the combustion exhaust gas introduced into the interior of the housing of the secondary heat exchanger through the gas inlet is suppressed from flowing upward by the flow deviation member, and then flows forward while diffusing vertically. Therefore, at a position close to the gas inlet, the combustion exhaust gas can also flow near the heat transfer tubes provided at the lower part of the housing. Thus, the heat quantity of the combustion exhaust gas can be efficiently transferred to the water flowing in the heat transfer tubes, and the thermal efficiency can be improved.

[0011] (2) Preferably, the flow deviation member is a guide plate provided integrally with the housing at the upper edge of the gas inlet and inclined downward toward the interior of the housing.

[0012] According to such a configuration, by providing the guide plate integrally with the housing, the thermal efficiency can be improved without increasing the number of parts.

[0013] (3) The plurality of heat transfer tubes include a plurality of straight tube portions that extend in the left-right direction and are spaced apart in the vertical and front-rear directions in a state where the plurality of heat transfer tubes are disposed inside the housing. Preferably, the virtual plane including the guide plate intersects the straight tube portion that is arranged in the last row and below the central position in the vertical direction among the plurality of straight tube portions.

[0014] With such a configuration, the combustion exhaust gas introduced into the secondary heat exchanger is guided downward by the guide plate and flows forward while slightly changing its direction upward due to the upward tendency of the combustion exhaust gas itself, passing near the last row of straight pipe portions in the vicinity of the vertical center of the housing. Thereafter, the combustion exhaust gas flows forward while diffusing vertically and transfers heat to the straight pipe portions. Therefore, by bringing the combustion exhaust gas into contact with more heat transfer tubes, efficient heat recovery can be achieved and the thermal efficiency can be improved.

[0015] (4) The path member is provided with an internal space through which the combustion exhaust gas flows and an opening that is the terminal end of the internal space and opens forward. The internal space widens upward as it approaches the opening. The opening communicates with the gas inlet, and it is preferable that the upper end of the opening and the upper end of the gas inlet are at the same height.

[0016] With such a configuration, it is possible to suppress the formation of a pool of combustion exhaust gas in the path member and suppress an increase in exhaust resistance.

[0017] <Embodiment 1> Hereinafter, Embodiment 1 will be described with reference to FIGS. 1 to 17. Note that for a plurality of identical members, only some members may be labeled with reference numerals, and the reference numerals of other members may be omitted.

[0018] [Overall Structure of the Water Heater] FIG. 1 is a front view of the water heater 1 as seen from the front, showing the state with the front cover removed. FIGS. 2 and 3 are views showing the inner cylinder 3 which is a main component arranged inside the outer casing 2 of the water heater 1. As shown in FIGS. 1 to 3, the water heater 1 includes a burner device 4, a primary heat exchanger 10, a secondary heat exchanger 20, a path member 50, a water inlet pipe 13, a hot water outlet pipe 14, a relay pipe 15, etc., and has a function of heating the tap water supplied from the outside and discharging hot water. The burner device 4 burns combustion gas to generate combustion exhaust gas. The combustion exhaust gas generated by the burner device 4 passes through the primary heat exchanger 10, then through the path member 50, and is sent into the secondary heat exchanger 20 and discharged to the outside of the water heater 1. In the primary heat exchanger 10, the sensible heat of the combustion exhaust gas is recovered, and in the secondary heat exchanger 20, the latent heat of the combustion exhaust gas is recovered.

[0019] The water inlet pipe 13 is configured as a path through which water is supplied, and as shown in FIG. 3, it is connected to the first header 37 of the secondary heat exchanger 20. As shown in FIGS. 8 and 9, the first header 37 is connected to a plurality of heat transfer pipes 21 housed in the housing 22. The end portions of the plurality of heat transfer pipes 21 on the side opposite to the first header 37 are connected to the second header 38. As shown in FIG. 3, the second header 38 is connected to the primary heat transfer pipe 12 arranged inside the primary heat exchanger 10 via the relay pipe 15. As shown in FIGS. 1 and 2, the end portion of the primary heat transfer pipe 12 of the primary heat exchanger 10 on the side opposite to the relay pipe 15 is connected to the hot water outlet pipe 14. The hot water outlet pipe 14 is configured as a path for sending out hot water. That is, in the water heater 1, the water flowing in from the water inlet pipe 13 flows in the order of the plurality of heat transfer pipes 21 of the secondary heat exchanger 20, the relay pipe 15, and the primary heat transfer pipe 12 of the primary heat exchanger 10. Then, the water flowing through the inside of the plurality of heat transfer pipes 21 of the secondary heat exchanger 20 and the primary heat transfer pipe 12 of the primary heat exchanger 10 receives the heat quantity of the combustion exhaust gas and is heated, and flows out as hot water from the hot water outlet pipe 14.

[0020] As shown in Fig. 1, the water heater 1 is provided with a drain hose 5. The upstream side of the drain hose 5 is connected to a drain outlet 26 (see Fig. 2) of the secondary heat exchanger 20 described later, and the downstream side is connected to a neutralizer. The drain generated by recovering the latent heat of the combustion exhaust gas in the secondary heat exchanger 20 is discharged to the outside of the secondary heat exchanger 20 through the drain outlet 26 and sent to the neutralizer through the drain hose 5.

[0021] As shown in Fig. 1, the water heater 1 is provided with a controller 6 as a control device. The controller 6 is configured as, for example, a known microcomputer or the like, and is configured to be able to acquire signals from various sensors provided in the water heater 1, and to be able to control various actuators provided in the water heater 1. For example, when the water heater 1 detects the flow of water in the water inlet pipe 13 by a water flow sensor (not shown), it operates the burner device 4 to generate hot water.

[0022] [Primary heat exchanger] As shown in Figs. 2 and 3, the primary heat exchanger 10 includes a can body 11 and primary heat transfer pipes 12. The can body 11 has a substantially rectangular shape in plan view that is long in the left-right direction and is formed in a cylindrical shape that penetrates vertically. The primary heat transfer pipes 12 of the primary heat exchanger 10 are arranged inside the can body 11 and include a plurality of straight pipes extending in the front-rear direction and connection pipes that connect the front ends or the rear ends of two straight pipes adjacent to each other in the left-right direction outside the can body 11. The plurality of straight pipes are connected in series via the connection pipes. That is, the primary heat transfer pipes 12 of the primary heat exchanger 10 are formed in a meandering shape as a whole. The can body 11 and the primary heat transfer pipes 12 can be made of copper with excellent thermal conductivity.

[0023] The primary heat exchanger 10 is fixed to the upper end of the burner device 4 and is arranged such that the combustion exhaust gas generated by the burner device 4 passes through the inside of the can body 11 of the primary heat exchanger 10 from bottom to top. Further, a path member 50, which will be described later, is fixed to the upper end of the primary heat exchanger 10, and the combustion exhaust gas from which sensible heat has been recovered by the primary heat exchanger 10 is sent to the path member 50.

[0024] As shown in FIG. 3, a relay pipe 15 is connected to the opening at the rear and right end of the primary heat transfer pipe 12, and water from the secondary heat exchanger 20 flows in. As shown in FIG. 2, a hot water outlet pipe 14 is connected to the opening at the front and left side of the primary heat transfer pipe 12, and the heated water flows out. That is, in the primary heat exchanger 10, the water that has flowed into the right rear surface side of the can body 11 through the relay pipe 15 exchanges heat with the combustion exhaust gas passing through the inside of the can body 11 while meandering inside the primary heat transfer pipe 12 and is heated. Then, the heated hot water flows into the hot water outlet pipe 14 from the front left surface side of the can body 11.

[0025] [Secondary heat exchanger] Next, the configuration of the secondary heat exchanger 20 will be described in detail. As shown in FIGS. 1 to 3, the secondary heat exchanger 20 is arranged above the primary heat exchanger 10. The secondary heat exchanger 20 and the primary heat exchanger 10 are connected by a path member 50 for introducing the combustion exhaust gas that has passed through the primary heat exchanger 10 into the secondary heat exchanger 20.

[0026] As shown in FIG. 5, the secondary heat exchanger 20 includes a plurality (seven in this embodiment) of heat transfer pipes 21 and a housing 22 in which the plurality of heat transfer pipes 21 are arranged inside. The plurality of heat transfer pipes 21 and the housing 22 can be made of stainless steel with excellent corrosion resistance.

[0027] [Housing, housing main body portion] As shown in FIG. 11, the housing 22 includes a housing main body portion 23 having a bottomed box shape with an open top, a lid body 24 that closes the housing main body portion 23 from above, and a partition portion 25 arranged inside the housing 22. As shown in FIG. 14, the housing main body 23 includes a bottom wall portion 23A, a front wall portion 23B rising from the front edge of the bottom wall portion 23A, a rear wall portion 23C rising from the rear edge of the bottom wall portion 23A, a right wall portion 23D rising from the right edge of the bottom wall portion 23A, and a left wall portion 23E rising from the left edge of the bottom wall portion 23A. The front wall portion 23B, the right wall portion 23D, the rear wall portion 23C, and the left wall portion 23E constitute the peripheral wall portion of the housing main body 23. A drain outlet 26 penetrating the bottom wall portion 23A in the vertical direction is provided in the front side portion of the bottom wall portion 23A. As shown in FIG. 5, in the water heater 1, the bottom wall portion 23A is arranged to incline downward as it goes forward, facilitating the discharge of the drain generated along with the latent heat recovery in the secondary heat exchanger 20 to the drain outlet 26.

[0028] As shown in FIG. 11, a fixing portion 27 for clamping and fixing the lid body 24 to the housing main body 23 is provided at the upper end portion of the peripheral wall portion of the housing main body 23. As shown in FIG. 14, the fixing portion 27 has a flange portion 27A that extends outward in a flange shape from the upper end peripheral edge portion of the peripheral wall portion, and a clamping portion 27B that extends upward from the outer edge portion of the flange portion 27A. As shown in FIG. 6, the clamping portion 27B is a portion that deforms when the lid body 24 is clamped to the housing main body 23. In a state where the lid body 24 is clamped to the housing main body 23, the clamping portion 27B deforms so as to sandwich the fixed portion 24A provided at the outer peripheral edge portion of the lid body 24 together with the flange portion 27A in the vertical direction. Further, an annular packing 27C is interposed between the fixed portion 24A and the clamping portion 27B, preventing the passage of gas between the lid body 24 and the housing main body 23.

[0029] [Gas inlet] As shown in FIG. 14, a gas inlet 28 penetrating in the front-rear direction is formed in the rear wall portion 23C of the housing main body portion 23. The gas inlet 28 is an opening for introducing combustion exhaust gas into the interior of the housing 22. A plurality of connected portions 29 are formed at the peripheral edge of the gas inlet 28 in the rear wall portion 23C. The connected portions 29 have a female screw shape and are configured to attach the path member 50 as shown in FIGS. 6 and 7. That is, combustion exhaust gas is introduced into the interior of the housing 22 from the path member 50 through the gas inlet 28.

[0030] [Guide plate, flow deflection member] As shown in FIG. 14, a burring portion 30 extending inward of the housing 22 is provided at the opening edge of the gas inlet 28. A guide plate 31 is integrally formed with the housing main body portion 23 so as to be continuous with the burring portion 30 at the upper edge portion of the opening edge of the gas inlet 28. The guide plate 31 is inclined downward as it extends toward the interior of the housing 22. The guide plate 31 serves as a flow deflection member 32 that suppresses the upward flow of the combustion exhaust gas introduced from the gas inlet 28 into the interior of the housing 22 (details will be described later).

[0031] As shown in FIG. 8, a right-side opening 33 penetrating in the left-right direction is formed in the right wall portion 23D of the housing main body portion 23. The right-side opening 33 is an opening for accommodating a plurality of heat transfer tubes 21 assembled to an assembly 35 described later. A plurality of connected portions 34 are formed around the right-side opening 33 in the right wall portion 23D. The connected portions 34 have a female screw shape and are used for attaching the assembly 35.

[0032] [Plurality of heat transfer tubes] As shown in FIG. 8, the assembly 35 includes a plurality of heat transfer tubes 21, a plate-shaped closing member 36, a first header 37, and a second header 38. As shown in FIG. 10, the heat transfer tubes 21 extend in a meandering manner along a predetermined planar direction. Each of the heat transfer tubes 21 has a common shape. The heat transfer tube 21 has a plurality (six in this embodiment) of straight tube portions 21A, at least one (five in this embodiment) of U-shaped tube portions 21B, a first connection portion 21C, and a second connection portion 21D.

[0033] [Plurality of straight tube portions] Each of the plurality of straight tube portions 21A is arranged in parallel in a direction (front-rear direction) orthogonal to the direction (left-right direction) in which the plurality of straight tube portions 21A extend. The front and rear ends of two adjacent straight tube portions 21A in the front-rear direction are connected by a U-shaped tube portion 21B that bends in a U shape. However, the right ends of the straight tube portion 21A arranged in the frontmost row and the straight tube portion 21A arranged in the rearmost row are not connected to the U-shaped tube portion 21B and are open to the right. The right end of the straight tube portion 21A in the frontmost row is the first connection portion 21C, and the right end of the straight tube portion 21A in the rearmost row is the second connection portion 21D. By alternately connecting the plurality of straight tube portions 21A and the U-shaped tube portions 21B from the first connection portion 21C to the second connection portion 21D, the heat transfer tubes 21 are connected in series.

[0034] As shown in FIG. 8, the plurality of heat transfer tubes 21 are fixed to the closing member 36 in a state of being stacked in the vertical direction and housed in the housing 22. As shown in FIG. 5, in a state where the plurality of heat transfer tubes 21 are disposed inside the housing 22, the plurality of straight tube portions 21A extend in the left-right direction and are arranged spaced apart in the vertical and front-rear directions. More specifically, two adjacent heat transfer tubes 21 in the vertical direction are arranged offset from each other in the front-rear direction, and the plurality of straight tube portions 21A are arranged in a staggered pattern as a whole in a side sectional view. Among the plurality of heat transfer tubes 21, since the straight tube portions 21A are arranged orthogonal to the flow direction of the combustion exhaust gas (mainly in the front-rear and vertical directions), the heat exchange between the water flow and the combustion exhaust gas in the plurality of heat transfer tubes 21 mainly occurs in the straight tube portions 21A.

[0035] As shown in Fig. 8, the closing member 36 is a plate-like member for closing the right opening 33 from the right in a state where a plurality of heat transfer tubes 21 are housed in the housing 22. As shown in Fig. 9, the closing member 36 has a first through hole through which the first connection portions 21C of the plurality of heat transfer tubes 21 are inserted, a second through hole through which the second connection portions 21D of the plurality of heat transfer tubes 21 are inserted, and an insertion hole through which the connecting member 36A is inserted, which are formed to penetrate in the left-right direction. A burring portion is provided in the first through hole, and the first connection portion 21C is fixed to the closing member 36 by brazing or the like in a state of being inserted into the first through hole. Similarly, the second connection portion 21D is also fixed to the closing member 36 by brazing or the like in a state of being inserted into the second through hole. As shown in Fig. 8, the insertion hole is provided at a position corresponding to the connected portion 34, and the closing member 36 is fixed to the right wall portion 23D by connecting the connecting member 36A inserted into the insertion hole to the connected portion 34. An annular packing 36B is provided between the right wall portion 23D and the closing member 36. Thereby, the passage of gas between the right wall portion 23D and the closing member 36 is prevented.

[0036] As shown in Fig. 3, the first header 37 is a portion connecting the inlet of the secondary heat exchanger 20 (specifically, the openings of the first connection portions 21C of the plurality of heat transfer tubes 21) and the downstream side of the water inlet pipe 13. As shown in Fig. 9, the first header 37 includes a first header body 37A fixed to the closing member 36, a first header lid 37B covering the opening of the first header body 37A, and a joint cylinder 37C. The first header body 37A has a first bottom hole 37D through which the first connection portion 21C inserted into the closing member 36 is inserted. The first header lid 37B has a first lid hole 37E to which the joint cylinder 37C is attached. The joint cylinder 37C is a portion connected to the downstream side of the water inlet pipe 13.

[0037] As shown in FIG. 3, the second header 38 is a portion that connects the outlet of the secondary heat exchanger 20 (specifically, the opening of the second connection portion 21D of the plurality of heat transfer tubes 21) and the pipe on the inlet side of the primary heat exchanger 10 (specifically, the upstream end of the relay pipe 15). As shown in FIG. 9, the second header 38 includes a second header body 38A fixed to the closing member 36, a second header lid 38B that covers the opening of the second header body 38A, and a joint cylinder 38C. The second header body 38A has a second bottom hole 38D through which the second connection portion 21D inserted through the closing member 36 is inserted. The second header lid 38B has a second lid hole 38E to which the joint cylinder 38C is attached. The joint cylinder 38C is a portion connected to the upstream side of the relay pipe 15. As a method for assembling each of the headers 37 and 38 and fixing each of the headers 37 and 38 to the closing member 36 and the like, brazing, welding, or the like can be used.

[0038] In the secondary heat exchanger 20, the water supplied from the water inlet pipe 13 passes through the first connection portions 21C of the respective heat transfer tubes 21 in parallel via the first header 37. The water flow exchanges heat with the combustion exhaust gas flowing in the housing 22 while flowing in a meandering shape through each of the heat transfer tubes 21. The water flow heated by the heat exchange flows from the second connection portion 21D into the relay pipe 15 via the second header 38.

[0039] [Cover] As shown in FIG. 11, the lid 24 is a plate-like member and includes a bulging portion 39 that bulges upward at the central portion and a fixed portion 24A disposed at the outer edge of the bulging portion 39. A gas outlet 41 penetrating in the vertical direction is formed on the top surface of the bulging portion 39. As shown in FIG. 4, the gas outlet 41 is located at the central position in the left-right direction and closer to the front in the housing 22. As shown in FIG. 5, a cylindrical exhaust pipe 42 protruding upward is provided at the peripheral edge of the gas outlet 41. The combustion exhaust gas from which latent heat has been recovered in the secondary heat exchanger 20 is discharged to the outside through the gas outlet 41. Specifically, the combustion exhaust gas is discharged to the outside through an exhaust pipe portion (not shown) connected to the exhaust pipe 42.

[0040] As shown in FIG. 11, when the lid body 24 is clamped and fixed to the housing main body 23, the portion to be fixed 24A is arranged above the flange portion 27A of the housing main body 23 and is clamped by the clamping portion 27B. As shown in FIG. 6, the portion to be fixed 24A is configured to be clamped in the vertical direction by the flange portion 27A and the clamping portion 27B. By clamping and fixing the lid body 24 to the housing main body 23, the housing main body 23 is closed.

[0041] [Partition portion] As shown in FIG. 5, the partition portion 25 is a plate-like member fixed to the lower surface of the lid body 24, and vertically partitions the internal space S1 of the housing formed by the housing main body 23 and the lid body 24. Specifically, the partition portion 25 partitions the internal space S1 of the housing into a layout region S2 in which a plurality of heat transfer tubes 21 are arranged, and an upper region S3 arranged on the lid body 24 side (upper side) than the layout region S2. The upper region S3 communicates with the gas outlet 41 upward. The layout region S2 and the upper region S3 communicate with each other through an opening 46 and a plurality of through holes 43A described later.

[0042] As shown in FIG. 13, the partition portion 25 includes a bottom plate 43, extending portions 44 extending upward from the left and right edge portions and the rear edge portion of the bottom plate 43, and a fixing piece 45 extending upward from the front edge portion of the bottom plate 43. The bottom plate 43 has a rectangular plate shape. A plurality (22 in this embodiment) of through holes 43A penetrating in the vertical direction are formed in the bottom plate 43. The plurality of through holes 43A are arranged in two rows in the front-rear direction in a substantially one-third region on the front side of the bottom plate 43 and are arranged closer to the center in the left-right direction. As shown in FIG. 4, in the housing 22, a part of the plurality of through holes 43A is arranged directly below the gas outlet 41. As shown in FIG. 5, the plurality of through holes 43A communicate the layout region S2 and the upper region S3. The bottom plate 43 is arranged at a distance below the lid body 24.

[0043] As shown in FIG. 13, the extended portion 44 includes a laterally extended portion 44A extending from both left and right end portions of the bottom plate 43, and a rearward extended portion 44B extending from the rear edge portion of the bottom plate 43. The laterally extended portion 44A rises substantially vertically upward from the bottom plate 43. The rearward extended portion 44B includes a portion rising substantially vertically upward from the bottom plate 43, and a first fixing portion 44C further extending rearward from the upper end portion of the rising portion.

[0044] In the present embodiment, the fixing piece 45 includes a second fixing portion 45A having a long shape in the left - right direction, and three extending portions 45B extending obliquely downward rearward from the second fixing portion 45A and connected to the bottom plate 43. The extending portions 45B are arranged at the left - right center position, the left - end side, and the right - end side of the second fixing portion 45A. Note that, different from the present embodiment, a plurality of fixing pieces may be provided at intervals in the left - right direction at the front edge portion of the bottom plate, and each fixing piece may have a configuration including one second fixing portion and one extending portion.

[0045] As shown in FIG. 5, the partition portion 25 is fixed by welding the first fixing portion 44C of the extended portion 44 and the second fixing portion 45A of the fixing piece 45 to the lower surface of the lid body 24. In a state where the partition portion 25 is fixed to the lid body 24, as shown in FIG. 12, the front edge portions of the lid body 24 and the partition portion 25 constitute an opening 46 that is open in the front - rear direction. The space (upper region S3) between the lid body 24 and the partition portion 25 opens forward through the opening 46. As shown in FIG. 5, the opening 46 connects the upper region S3 and the arrangement region S2. Also, the upper region S3 is blocked by the rearward extended portion 44B at the rear. As shown in FIG. 12, the upper region S3 is defined by the laterally extended portions 44A on both sides. Therefore, as shown in FIG. 5, the arrangement region S2 and the upper region S3 are connected through a plurality of through - holes 43A and the opening 46.

[0046] As shown in Fig. 5, the opening 46 is arranged in front of the plurality of heat transfer tubes 21 within the housing 22. Therefore, the opening 46 allows the combustion exhaust gas that has reached the vicinity of the frontmost straight tube portion 21A among the plurality of heat transfer tubes 21 to pass from the arrangement region S2 to the upper region S3 (see Fig. 16). For this reason, heat recovery can also be achieved at the frontmost straight tube portion 21A, and the efficiency of heat transfer from the combustion exhaust gas to the water flowing through the plurality of heat transfer tubes 21 can be improved.

[0047] On the other hand, as shown in Fig. 5, the plurality of through holes 43A of the partition portion 25 are arranged behind the opening 46 within the housing 22 and above the front portion of the plurality of heat transfer tubes 21. For this reason, a part of the combustion exhaust gas that has reached the front side of the arrangement region S2 from the gas inlet 28 flows from the arrangement region S2 to the upper region S3 through the plurality of through holes 43A behind the frontmost straight tube portion 21A (see Fig. 16). That is, the exhaust path that flows from the arrangement region S2 to the upper region S3 through the plurality of through holes 43A is shorter in distance than the exhaust path that flows from the arrangement region S2 to the upper region S3 through the opening 46 provided on the front side within the housing 22, and it is a so-called shortcut exhaust path. As a result, although the heat efficiency of the secondary heat exchanger 20 is reduced, an increase in the exhaust resistance of the combustion exhaust gas can be suppressed, and the combustion performance of the water heater 1 can be ensured.

[0048] [Path member] As shown in Fig. 5, the path member 50 is arranged between the primary heat exchanger 10 and the secondary heat exchanger 20. The path member 50 communicates the upper end opening of the can body 11 of the primary heat exchanger 10 and the gas inlet 28 of the rear wall portion 23C of the housing 22 of the secondary heat exchanger 20, and constitutes an internal space S4 through which the combustion exhaust gas flows.

[0049] As shown in Fig. 15, the path member 50 is configured to have a path member main body 51 and a path member rear portion 52. The path member body 51 is formed in a shape that gradually rises from the front end toward the rear in the front-rear direction and bulges upward. The rear end of the path member body 51 is open to the rear, and a plurality of connected parts are provided at the periphery of this opening. These plurality of connected parts are in the form of female threads and are configured to be connected to the connecting member 52A. The rear part 52 of the path member is formed in a square dish shape that bulges rearward. The rear part 52 of the path member has an insertion hole at a position corresponding to the connected part of the path member body 51, and the connecting member 52A inserted through this insertion hole is configured to be connected to the connected part of the path member body 51. As a result, as shown in FIG. 7, the rear part 52 of the path member is fixed to the path member body 51 so as to close the rear opening of the path member body 51. A packing (not shown) is provided between the path member body 51 and the rear part 52 of the path member to prevent the passage of gas between the path member body 51 and the rear part 52 of the path member.

[0050] As shown in FIG. 7, the rear part 52 of the path member has an insertion hole at a position corresponding to the connected part 29 of the rear wall part 23C. By connecting the connecting member 52B inserted through this insertion hole to the connected part 29, the rear part 52 of the path member is configured to be fixed to the rear wall part 23C. An annular packing 52C is provided between the rear wall part 23C and the rear part 52 of the path member. The packing 52C prevents the leakage of gas between the rear wall part 23C and the rear part 52 of the path member.

[0051] As shown in FIG. 15, an opening 53 that opens forward is provided in the upper part of the rear part 52 of the path member. As shown in FIG. 5, the opening 53 is the terminal end of the internal space S4 of the path member 50, and the internal space S4 extends obliquely upward in front as it approaches the opening 53, that is, as it approaches the terminal end side. In a state where the path member 50 is attached to the housing 22, the opening 53 communicates with the gas inlet 28. The upper end of the opening 53 and the upper end of the gas inlet 28 are set at the same height (see FIG. 6).

[0052] Since the combustion exhaust gas is usually at a higher temperature (about 200°C) than the ambient temperature and shows an upward trend, if there is a space that spreads upward in the exhaust path of the combustion exhaust gas, the combustion exhaust gas may stay in that space and form a pool. However, in this embodiment, as described above, the internal space S4 of the path member 50 widens upward as it approaches the opening 53 that serves as the terminal end, and the upper end of the opening 53 coincides with the upper end of the gas inlet 28. Therefore, when the combustion exhaust gas flows from the path member 50 into the housing 22, a pool of combustion exhaust gas is not formed in the internal space S4 of the path member 50. Accordingly, an increase in the exhaust resistance of the combustion exhaust gas can be suppressed, and the combustion performance of the water heater 1 can be ensured.

[0053] [Flow deviation of combustion exhaust gas by the guide plate] Hereinafter, the flow deviation of the combustion exhaust gas by the guide plate 31 in this embodiment will be described with reference to FIGS. 16 and 17. FIG. 16 is a cross-sectional view of the secondary heat exchanger 20 and the path member 50 reflecting the calculation results of the flow velocity of the combustion exhaust gas, and the arrow indicates the flow direction of the combustion exhaust gas with a high flow velocity. That is, the arrow indicates the portion where a large amount of combustion exhaust gas flows and its flow direction. FIG. 17 is a diagram created in the same manner as FIG. 16, and shows the secondary heat exchanger 120 of the water heater 101 according to a comparative example not included in the scope of the present disclosure.

[0054] In both cases of FIGS. 16 and 17, the combustion exhaust gas introduced from the gas inlet 28 flows while being divided vertically near the plurality of straight pipe portions 21A and flows forward in the arrangement region S2. Then, the combustion exhaust gas flows from the arrangement region S2 to the upper region S3 through the opening 46 or the through hole 43A, and is finally discharged from the gas outlet 41.

[0055] First, for comparison, while different from the present embodiment, the configuration of the water heater 101 including the secondary heat exchanger 120 without a guide plate will be described with reference to FIG. 17. In FIG. 17, the same components as those in Embodiment 1 are denoted by the same reference numerals as in Embodiment 1. When the guide plate is not provided, the combustion exhaust gas introduced from the gas inlet 28 into the housing 22 flows upward and forward due to the upward tendency of the combustion exhaust gas. Then, the combustion exhaust gas mainly flows forward in the vicinity of the straight pipe portion 21A (hereinafter referred to as the last row upper straight pipe portion 21AU) arranged in the last row and the upper side (specifically, the sixth row from the bottom) among the plurality of straight pipe portions 21A, and enters the space between the plurality of heat transfer pipes 21.

[0056] As described above, when the combustion exhaust gas mainly flows forward in the vicinity of the last row upper straight pipe portion 21AU, it becomes difficult for the combustion exhaust gas to flow through the region S5 in the vicinity of the straight pipe portion 21A arranged on the rear row side and the lower row side among the plurality of straight pipe portions 21A. As a result, the heat exchange efficiency between the water flowing through the straight pipe portion 21A arranged on the rear row side and the lower row side and the combustion exhaust gas deteriorates. Therefore, it is difficult to improve the thermal efficiency in the secondary heat exchanger 120.

[0057] On the other hand, in the present embodiment, as shown in FIG. 16, a guide plate 31 that slopes downward toward the inside of the housing 22 is provided at the upper end of the gas inlet 28. Therefore, when the combustion exhaust gas having an upward tendency is introduced from the gas inlet 28 into the housing 22, it is deflected downward by the guide plate 31 while flowing forward. As a result, the combustion exhaust gas mainly flows forward in the vicinity of the straight pipe portion 21A (hereinafter referred to as the last row central straight pipe portion 21AM) arranged in the last row and the central position in the vertical direction (specifically, the fourth row from the bottom), and enters the space between the plurality of heat transfer pipes 21.

[0058] As described above, when the combustion exhaust gas mainly passes through the vicinity of the central straight pipe portion 21AM in the last row, the combustion exhaust gas is divided vertically in the vicinity of the central straight pipe portion 21AM in the last row, and also flows into the region S5 in the vicinity of the straight pipe portion 21A arranged on the rear row side and the lower row side among the plurality of straight pipe portions 21A. Therefore, compared with the case where the guide plate 31 is not provided, the efficiency of heat exchange between the water flowing through the straight pipe portion 21A arranged on the rear row side and the lower row side and the combustion exhaust gas is improved, so that the efficiency of heat recovery in the secondary heat exchanger 20 can be improved.

[0059] Also, as shown in FIG. 5, in the present embodiment, the virtual plane VP including the guide plate 31 intersects with the straight pipe portion 21A arranged on the lower side (specifically, the second row from the bottom row) and the last row among the plurality of straight pipe portions 21A (hereinafter referred to as the straight pipe portion 21AL on the lower side of the last row). In particular, when the inclination of the guide plate 31 is adjusted so that the virtual plane VP intersects with the straight pipe portion 21AL on the lower side of the last row in this way, as shown in FIG. 16, it is known that the combustion exhaust gas easily flows into the region S5 in the vicinity of the straight pipe portion 21A arranged on the rear row side and the lower row side.

[0060] [Operation and Effect of Embodiment 1] As described above, the water heater 1 of the present embodiment includes a primary heat exchanger 10, a secondary heat exchanger 20 arranged above the primary heat exchanger 10, and a path member 50 that connects the primary heat exchanger 10 and the secondary heat exchanger 20 and introduces the combustion exhaust gas discharged from the primary heat exchanger 10 into the secondary heat exchanger 20. The secondary heat exchanger 20 includes a plurality of heat transfer pipes 21 and a housing 22 in which the plurality of heat transfer pipes 21 are arranged inside. A gas inlet 28 is formed in the rear wall portion 23C of the housing 22, a path member 50 is attached to the peripheral edge of the gas inlet 28, and a flow deflection member 32 is provided in the housing 22 to suppress the upward flow of the combustion exhaust gas introduced into the housing 22 from the gas inlet 28.

[0061] With such a configuration, the combustion exhaust gas introduced into the housing 22 of the secondary heat exchanger 20 through the gas inlet 28 is suppressed from flowing upward by the flow deflection member 32, and then flows forward while diffusing vertically. Therefore, the combustion exhaust gas can also flow near the heat transfer tubes 21 provided at the lower part of the housing 22 at a position close to the gas inlet 28. Thus, the heat quantity of the combustion exhaust gas can be efficiently transferred to the water flowing in the heat transfer tubes 21, and the thermal efficiency can be improved.

[0062] In the present embodiment, the flow deflection member 32 is provided at the upper edge of the gas inlet 28 integrally with the housing 22 and is a guide plate 31 that inclines downward toward the inside of the housing 22.

[0063] With such a configuration, by providing the guide plate 31 integrally with the housing 22, the thermal efficiency can be improved without increasing the number of parts.

[0064] In the present embodiment, the plurality of heat transfer tubes 21 include a plurality of straight tube portions 21A that extend in the left - right direction and are spaced apart in the vertical and front - rear directions in a state where the plurality of heat transfer tubes 21 are disposed inside the housing 22. The virtual plane VP including the guide plate 31 intersects the straight tube portion 21A that is arranged in the last row and below the central position in the vertical direction among the plurality of straight tube portions 21A.

[0065] With such a configuration, the combustion exhaust gas introduced into the secondary heat exchanger 20 is guided downward by the guide plate 31 and flows forward while slightly changing its direction upward due to the upward tendency of the combustion exhaust gas itself, and passes near the straight tube portion 21A of the last row near the central portion in the vertical direction of the housing 22. Thereafter, the combustion exhaust gas flows forward while diffusing vertically and transfers heat to the straight tube portions 21A. Therefore, by bringing the combustion exhaust gas into contact with more heat transfer tubes 21, efficient heat recovery can be performed and the thermal efficiency can be improved.

[0066] In this embodiment, the path member 50 is provided with an internal space S4 through which the combustion exhaust gas flows, an opening 53 that serves as the terminal end of the internal space S4 and opens forward. The internal space S4 expands upward as it approaches the opening 53. The opening 53 communicates with the gas inlet 28, and the upper end of the opening 53 and the upper end of the gas inlet 28 are at the same height.

[0067] According to such a configuration, it is possible to suppress the formation of a pool of combustion exhaust gas in the path member 50 and suppress an increase in exhaust resistance.

[0068] <Embodiment 2> Hereinafter, Embodiment 2 will be described with reference to FIG. 18. FIG. 18, similar to FIGS. 16 and 17 described above, is a cross-sectional view of the secondary heat exchanger 220 and the path member 50 reflecting the calculation result of the flow velocity of the combustion exhaust gas, and shows the flow direction of the combustion exhaust gas with a high flow velocity by an arrow. That is, the arrow indicates the portion where a large amount of combustion exhaust gas flows and its flow direction. For a plurality of identical members, only some members may be labeled with reference numerals, and the reference numerals of other members may be omitted. In addition, members similar to those in Embodiment 1 may be labeled with the same reference numerals as in Embodiment 1 and the description may be omitted.

[0069] The water heater 201 of Embodiment 2 includes a secondary heat exchanger 220. The secondary heat exchanger 220 includes an extension plate 232A instead of the guide plate 31 of Embodiment 1. The extension plate 232A is provided by extending a part of the upper end of the burring portion 30 provided at the opening edge of the gas inlet 228 straight forward, and has a eaves shape. That is, the extension plate 232A does not incline downward toward the inside of the housing 22. Further, the extension plate 232A extends forward at a position closer to the center in the vertical direction of the opening 53 of the path member 50. Therefore, behind the extension plate 232A, the upper end of the gas inlet 228 is disposed below the upper end of the opening 53.

[0070] As described above, Embodiment 2 differs from Embodiment 1 in that the upper end of the gas inlet 228 is provided below the upper end of the opening 53 in the vicinity of the extension plate 232A, and the extension plate 232A does not slope downward but extends forward. When the combustion exhaust gas is introduced from the path member 50 into the housing 22 through the gas inlet 228, although a slight accumulation of the combustion exhaust gas is formed in the upper part of the terminal end portion of the path member 50, the extension plate 232A somewhat suppresses the upward flow of the combustion exhaust gas introduced into the housing 22 from the gas inlet 228. That is, in Embodiment 2, the extension plate 232A functions as a flow deflection member. Due to the extension plate 232A, the combustion exhaust gas flows forward while slightly rising in the vicinity of the central straight pipe portion 21AM of the last row, and enters the space between the plurality of heat transfer pipes 21. As a result, since the combustion exhaust gas also flows through the region S5 in the vicinity of the straight pipe portion 21A arranged on the rear row side and the lower stage side among the plurality of straight pipe portions 21A, the thermal efficiency of the secondary heat exchanger 220 can be improved as compared with the comparative example.

[0071] The extension plate 232A can be easily formed as compared with the guide plate 31 of Embodiment 1 that requires adjustment of the inclination angle.

[0072] <Other Embodiments> The present disclosure is not limited to the embodiments described by the above description and drawings. For example, the features of the above-described or below-described embodiments can be combined in any combination within a non-contradictory range. Also, any feature of the above-described or below-described embodiments can be omitted if it is not explicitly specified as essential. Further, the above-described embodiments may be modified as follows.

[0073] In the above embodiment, the gas outlet 41 of the secondary heat exchanger 20 is configured to open upward, but the gas outlet of the secondary heat exchanger may be configured to open forward.

[0074] In the above embodiment, the water heaters 1 and 201 having a hot water supply circuit for heating tap water to discharge hot water are exemplified, but water heaters for other uses such as circulation for a bath or central heating may also be used.

[0075] Note that the scope of the present disclosure is not limited to the above-described embodiments, and it is intended that all modifications within the scope shown by the claims or within the scope equivalent to the claims be included.

Explanation of Reference Numerals

[0076] 1,101,201... water heater, 2... outer casing, 3... inner cylinder, 4... burner, 5... drain hose, 6... controller, 10... primary heat exchanger, 11... can body, 12... primary heat transfer pipe, 13... water inlet pipe, 14... hot water outlet pipe, 15... relay pipe 20,120... secondary heat exchanger 21... heat transfer pipe, 21A... straight pipe portion, 21AL... lower straight pipe portion of the last row, 21AM... central straight pipe portion of the last row, 21AU... upper straight pipe portion of the last row, 21B... U-shaped pipe portion, 21C... first connection portion, 21D... second connection portion, 22... housing, 23... housing main body portion, 23A... bottom wall portion, 23B... front wall portion, 23C... rear wall portion, 23D... right wall portion, 23E... left wall portion, 24... lid body, 24A... fixed portion, 25... partition portion, 26... drain outlet, 27... fixing portion, 27A... flange portion, 27B... caulking portion, 27C... packing, 28... gas inlet, 29... connected portion, 30... burring portion, 31... guide plate, 32... flow deflection member, 33... right opening, 34... connected portion, 35... assembled body, 36... closing member, 36A... connecting member, 36B... packing, 37... first header, 37A... first header main body, 37B... first header lid body, 37C... joint cylinder, 37D... first bottom hole, 37E... first lid hole, 38... second header, 38A... second header main body, 38B... second header lid body, 38C... joint cylinder, 38D... second bottom hole, 38E... second lid hole, 39... bulging portion, 41... gas outlet, 42... exhaust cylinder, 43... bottom plate, 43A... through hole, 44... extending portion, 44A... side extending portion, 44B... rear extending portion, 44C... first fixing portion, 45... fixing piece, 45A... second fixing portion, 45B... extending portion, 46... opening, 232A... extension plate, S1... internal space of the housing, S2... arrangement region, S3... upper region, S5... region near the straight pipe portion arranged on the rear row side and the lower stage side, VP... virtual plane 50... path member 51…Path member body, 52…Rear part of path member, 52A…Connecting member, 52B…Connecting member, 52C…Packing, 53…Opening, S4…Internal space 220…Secondary heat exchanger 228…Gas inlet, 232…Flow deviation member, 232A…Extension plate

Claims

1. A water heater comprising a primary heat exchanger, a secondary heat exchanger disposed above the primary heat exchanger, and a path member connecting the primary heat exchanger and the secondary heat exchanger and introducing the combustion exhaust gas discharged from the primary heat exchanger into the interior of the secondary heat exchanger, wherein the secondary heat exchanger includes a plurality of heat transfer tubes and a housing in which the plurality of heat transfer tubes are disposed, a gas inlet is formed in a rear wall portion of the housing, the path member is attached to a peripheral portion of the gas inlet, the housing is provided with a flow deflection member for suppressing upward flow of the combustion exhaust gas introduced into the housing from the gas inlet, the flow deflection member is provided at an upper edge portion of the gas inlet integrally with the housing and is a guide plate inclined downward toward the interior of the housing, the plurality of heat transfer tubes include a plurality of straight tube portions extending in the left-right direction and spaced apart in the vertical and front-rear directions in a state where the plurality of heat transfer tubes are disposed in the housing, a virtual plane including the guide plate intersects with the straight tube portion disposed below the central position in the vertical direction in the last row among the plurality of straight tube portions, the water heater.

2. the path member is provided with an internal space through which the combustion exhaust gas flows and an opening portion that is a terminal end of the internal space and opens forward, the internal space expands upward as it approaches the opening portion, the opening portion communicates with the gas inlet, the upper end of the opening portion and the upper end of the gas inlet are at the same height, the water heater according to claim 1.

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