Heat exchanger and water heater

Abstract

To improve thermal efficiency even if the number of stages of a heat transfer pipe is small.SOLUTION: A water heating side primary heat exchanger 25 includes a plurality of fins 27 arranged at a predetermined interval in a thick direction, and a plurality of heat transfer pipes 28 that penetrate each fin 27, are arranged in a row at a predetermined interval in a horizontal direction, and can perform heat exchange between combustion exhaust passing in each fin 27 upward from below and hot water passing through each heat transfer pipe 28. A cut-out portion 40 positioned between the heat transfer pipes 28 in a plane view, whose width becomes narrower toward upward is formed at the lower end of each fin 27 while a protrusion 45 positioned between the heat transfer pipes 28 in a plane view, which protrudes upward is formed at the upper end of each fin 27.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present disclosure relates to a heat exchanger used in a water heater and a water heater using the heat exchanger. [Background technology]

[0002] A known heat exchanger for a water heater is the fin-tube type, in which multiple fins are arranged side by side at a predetermined interval in the thickness direction inside a casing that forms a combustion chamber, and multiple heat transfer tubes that penetrate each fin at a right angle are alternately connected at both ends to form a single serpentine shape, and a high-temperature fluid such as burner combustion exhaust is passed between the fins, allowing heat exchange between the fluid and the fluid flowing inside the heat transfer tube. In particular, water heaters in which the inside of the casing is divided into two combustion chambers by a partition plate, and fins and heat transfer tubes are provided separately in each combustion chamber to house two heat exchangers, with the first heat exchanger being used for hot water supply and the second heat exchanger being used for heating or bathing. In this case, the first heat exchanger, which is usually required to ensure hot water heating capacity, is formed larger than the second heat exchanger. In particular, in Patent Document 1, in order to increase the hot water heating capacity of the narrow second heat exchanger, the heat transfer tubes of the second heat exchanger are arranged in multiple stages vertically to have more stages than the first heat exchanger, while the fins of the first heat exchanger are made smaller in vertical height than the fins of the second heat exchanger to reduce costs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6256801 Summary of the Invention [Problem to be solved by the invention]

[0004] However, because the combustion chamber itself is formed to accommodate the second heat exchanger, which has a larger number of stages, wasted space is generated above the fins of the first heat exchanger inside the casing, making it difficult to improve thermal efficiency.

[0005] Therefore, an object of the present disclosure is to provide a heat exchanger and a water heater that can improve thermal efficiency even when the number of stages of heat transfer tubes is small. [Means for solving the problem]

[0006] In order to achieve the above object, a first configuration of the present disclosure is a heat exchanger including a plurality of fins arranged at predetermined intervals in a thickness direction, and a plurality of heat transfer tubes penetrating each of the fins and arranged in a row at predetermined intervals in a horizontal direction, capable of exchanging heat between a fluid passing between each of the fins in a vertical direction and a fluid passing through each of the heat transfer tubes, At the lower end or upper end of each fin, a cutout portion is formed between the heat transfer tubes in a plan view, and the width of the cutout portion narrows toward the top or bottom. The fins are characterized in that a protrusion that protrudes upward or downward is formed on the upper or lower end of each fin and is located between the heat transfer tubes in a plan view. Another aspect of the first configuration is the above configuration, wherein each protrusion is located directly above or below a respective cutout portion and is shaped to match the cutout portion. Another aspect of the first configuration is that, in the above configuration, a plurality of offset fins protruding in the thickness direction of the fin are cut out and formed at predetermined intervals in the vertical direction on the upper or lower side of each fin and the lower or upper side of each protrusion, and each offset fin has a horizontal width that increases from the cutout side toward the protrusion side, and the horizontal width of each offset fin closest to the protrusion is formed to be the same as or smaller than the maximum horizontal width of each protrusion. Another aspect of the first configuration is that, in the above configuration, each heat transfer tube is connected in a serpentine shape in which adjacent ends in the horizontal direction are alternately connected, and the heat transfer tube located at one end in the horizontal direction serves as an inlet side for the fluid, The cutout portion located on the lower or upper side of the inlet heat transfer tube and the protrusion located directly above or directly below it are characterized in that they have larger areas than the other cutout portions and other protrusions, respectively. In order to achieve the above object, a second configuration of the present disclosure is a water heater, The device is characterized by comprising a burner and a heat exchanger of a first configuration, and enabling heat exchange between the burner's combustion exhaust passing between each fin and hot and cold water passing through each heat transfer tube. Effect of the Invention

[0007] According to the present disclosure, the surface area of ​​the fins can be increased by the protrusions. Therefore, even if the number of stages of the heat transfer tubes is small, the thermal efficiency can be improved. In particular, since each protrusion is located between each heat transfer tube in a plan view, heat can be efficiently recovered even from a high-temperature fluid with a high flow rate. According to another aspect of the present disclosure, in addition to the above effects, each protrusion is located directly above or below each cutout and has a shape that matches the cutout, so that the cutout that would normally be treated as waste material during press forming can be used as a protrusion. Therefore, even if the protrusions are provided, the amount of sheet metal used does not increase, and costs can be suppressed. According to another aspect of the present disclosure, in addition to the above effects, a plurality of offset fins are formed on the upper or lower part of each fin, below or above each protrusion, protruding in the thickness direction of the fin, with the horizontal width increasing from the cutout side to the protrusion side, and the horizontal width of each offset fin closest to the protrusion is formed to be equal to or smaller than the maximum horizontal width of each protrusion, thereby increasing the heat that can be collected from the fluid by the offset fins and improving thermal efficiency. Also, even if an offset fin with the maximum left-right width is provided, its strength can be maintained by providing it below or above the protrusion. According to another aspect of the present disclosure, in addition to the above effects, the cutouts located on the upper or lower side of the heat transfer tube on the fluid inlet side and the protrusions located directly above or below them have larger areas than the other cutouts and other protrusions, respectively, so that the low-temperature area around the heat transfer tube on the inlet side can be reduced and the temperature of the protrusions can be increased, thereby preventing the generation of drainage. [Brief description of the drawings]

[0008] [Figure 1]FIG. 2 is a front view of the water heater with the front cover removed. [Diagram 2] FIG. [Diagram 3] FIG. 4 is a perspective view of the fins of the hot water side primary heat exchanger. [Figure 4] FIG. 4 is a front view of the fins of the hot water side primary heat exchanger. [Diagram 5] FIG. 4 is an explanatory diagram of press forming of fins of the hot-water-supply-side primary heat exchanger. [Figure 6] FIG. 4 is a perspective view of the fins of the heating side primary heat exchanger. [Figure 7] FIG. 4 is a front view of the fins of the heating side primary heat exchanger. [Figure 8] FIG. 4 is an explanatory diagram of press forming of the fins of the heating-side primary heat exchanger. [Figure 9] FIG. 4 is an explanatory diagram showing the flow of combustion exhaust gas in the hot water supply side primary heat exchanger. [Figure 10] FIG. 4 is an explanatory diagram showing the flow of combustion exhaust gas in the heating-side primary heat exchanger. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a front view of the water heater with the front cover removed. The housing of the water heater 1 comprises a vertically long box-shaped main body 2 that is open at the front, and a front cover (not shown) that is attached to the front of the main body 2. The bottom of the main body 2 is provided with a water inlet 3, a gas inlet 4, a hot water outlet 5, a heating supply outlet 6, a heating return outlet 7, a bath supply outlet 8, and a bath return outlet 9. A combustion chamber 10 is provided at the rear side within the box body 2. The combustion chamber 10 includes a lower casing 11, a middle casing 12, and an upper casing 13, which are connected in the vertical direction. An exhaust section 14 having an exhaust pipe 15 protruding forward is provided on the front surface of the upper casing 13. As shown in Fig. 2, the inside of the combustion chamber 10 is divided into a first combustion chamber 17 on the right side and a second combustion chamber 18 on the left side by a partition member 16 provided in each casing. The first combustion chamber 17 is for hot water supply, and the second combustion chamber 18 is for heating. The first combustion chamber 17 is wider in left-right direction than the second combustion chamber 18.

[0010] The lower casing 11 accommodates a plurality of burners 20. The burners 20 have a flat shape extending in the front-rear direction, and are accommodated side by side in the left-right direction. The first combustion chamber 17 accommodates a greater number of burners 20 than the second combustion chamber 18, and the burners 20 are switched and used as a plurality of burner units with different numbers of burners 20. In the second combustion chamber 18, all the burners 20 form a single burner unit. A combustion fan 21 is connected to the lower surface of the lower casing 11. The combustion fan 21 supplies combustion air to the burners 20 of the first and second combustion chambers 17, 18, respectively. A gas distribution unit 22 is provided on the front side of the lower casing 11. The gas distribution unit 22 is provided with a plurality of solenoid valves, and the burner unit to be burned can be switched by opening and closing each solenoid valve. A gas pipe 23 equipped with a main valve and a proportional valve (not shown) is connected to the upstream end of the gas distribution unit 22. The gas pipe 23 is connected to the gas inlet 4.

[0011] A hot water supply side primary heat exchanger 25 and a heating side primary heat exchanger 26 are housed in the intermediate casing 12. The hot water supply side primary heat exchanger 25 is provided in the first combustion chamber 17, and the heating side primary heat exchanger 26 is provided in the second combustion chamber 18. The hot-water-supply-side primary heat exchanger 25 has a number of fins 27, 27·· arranged at a predetermined interval in the front-rear direction, and seven heat transfer tubes 28, 28·· that penetrate each fin 27 in the front-rear direction and are arranged at equal intervals in the left-right direction. Each heat transfer tube 28 has adjacent left and right ends connected alternately front to back by U-shaped tubes 29 to form a single serpentine hot-water-supply-side heat transfer tube 30. The right-most heat transfer tube 28 is the upstream end, and the left-most heat transfer tube 28 is the downstream end. The heating-side primary heat exchanger 26 has a plurality of fins 31, 31·· arranged at predetermined intervals in the front-rear direction, and five heat transfer tubes 32, 32·· (two in an upper row and three in a lower row) that penetrate each fin 31 in the front-rear direction and are arranged at equal intervals in the left-right direction. Adjacent ends of each heat transfer tube 32 on the left and right are connected alternately front to back by U-shaped tubes 33, and ends of vertically adjacent right-most heat transfer tubes 32, 32 are also connected by U-shaped tubes 33 to form a single serpentine heating-side heat transfer tube 34 that connects from the lower row to the upper row.

[0012] Fig. 3 is a perspective view of fin 27 of hot-water-supply-side primary heat exchanger 25, and Fig. 4 is a front view of fin 27. Seven through holes 35, 35..., through which each heat transfer tube 28 passes, are arranged side by side in the left-right direction in the lower part of this fin 27. Burring portions 36 rising toward the front are formed on the inner edge of each through hole 35. Three offset fins 37a to 37c are formed in the up-down direction between the through holes 35, 35 adjacent to each other on the left and right at the top of the fin 27. The offset fins 37a to 37c are formed in a band shape that is cut and raised toward the front side and extends in the left-right direction. Here, the lowest offset fin 37c is formed with the smallest left-right width, and the left-right width increases toward the top. The lowest offset fin 37c overlaps with the top of the through hole 35 in the left-right direction. Both left and right ends of the fin 27 are bent portions 38, 38 that are folded back toward the front side. The left bent portion 38 is abutted against the partition member 16 and fixed, and the right bent portion 38 is abutted against the inner surface of the intermediate casing 12 and fixed.

[0013] At the lower end of the fin 27, between the adjacent through holes 35, 35 on the left and right, cutouts 40, 40... are formed with their lower ends open. Each cutout 40 is tapered such that its width narrows linearly from the lower end upward. At the upper end of the cutout 40, a semicircular bulge 41 is formed that bulges upward. The bulge 41A of the right-end cutout 40A (hereinafter, when the right-end component of the fin 27 is described to be distinguished from the others, "A" is added.) extends upward more than the other bulges 41, and its upper end is located above the bulge 41. Therefore, the cutout 40A has a larger area than the other cutouts 40. At the left and right lower ends of each cutout 40, lower semicircular portions 42, 42 with a diameter smaller than that of the bulge 41 are cut out and formed, respectively. The right side of the lower end of cutout portion 40A is not a semicircle but an inverted L-shaped lower notch 43. Between cutout portions 40, 40, the lower side of each through hole 35 is a lower straight portion 44 extending in the left-right direction.

[0014] A plurality of protrusions 45, 45... are formed on the upper part of the fin 27 and on the upper side of the offset fin 37a, protruding upward. Each protrusion 45, like the cutout portion 40, is tapered such that the width of the left and right protrusions 45 narrows linearly from the lower end to the upper side, and is located between the heat transfer tubes 28, 28 adjacent to the left and right in a plan view. A flat portion 46 extending in the left and right direction is formed at the upper end of the protrusion 45. Upper semicircular portions 47, 47 having the same diameter as the lower semicircular portion 42 of the cutout portion 40 are cut out at the left and right lower ends of each protrusion 45. The flat portion 46A of the protrusion 45A at the right end is longer in the left and right directions than the other flat portions 46. A protrusion 48 protruding in a trapezoidal shape is formed at the right part of the protrusion 45A, and has a larger area than the other protrusions 45. The right side of the lower end of the protrusion 45A is an upper cutout portion 49 that is not semicircular but L-shaped. Above the through hole 35 between the protrusions 45, 45 is an upper straight portion 50 extending in the left-right direction. The maximum width including the upper semicircular portions 47, 47 at the base of each protrusion 45 is equal to the left-right width of the uppermost offset fin 37a. By positioning the protrusions 45 above the offset fin 37a in this way, the strength of the portion where the offset fin 37a is formed can also be ensured.

[0015] The fin 27 is obtained by press-molding a single sheet metal, but here, as shown in Fig. 5, the lower straight portion 44, the upper straight portion 50, the cutout portion 40, and the protrusion 45 are obtained by cutting the space between the upper and lower fins 27, 27 along the cut-off line 51. At this time, before cutting, semicircular hole processing P1, P1... is performed at the positions that are the apexes of the cutout portion 40 and the protrusion 45, circular hole processing P2, P2 is performed at the positions that are the left and right ends of the cutout portion 40 and the protrusion 45, and rectangular hole processing P3 extending vertically is performed at the right end of the cutout portion 40A and the protrusion 45A. Therefore, when cutting along the cut-off line 51, the bulge portion 41, the lower semicircular portion 42, the lower cutout portion 43, the flat portion 46, the upper semicircular portion 47, and the upper cutout portion 49 are also simultaneously formed. Although only two fins 27, 27 at the top and bottom are shown in FIG. 5, in reality, three or more fins 27 are press-formed from one metal plate in which three or more fins 27 are connected together. In this way, since the cutout portion 40 and the protrusion 45 have the same shape, the fin 27 can be press-formed without generating scraps in the metal sheet. In particular, by performing the holes P1 to P3 in advance before cutting along the cut-off line 51, even if the cut-off position is shifted when cutting, the hole position can be tolerated and the cutting can be performed reliably.

[0016] Fig. 6 is a perspective view of the fin 31 of the heating-side primary heat exchanger, and Fig. 7 is a front view of the fin 31. In the lower part of this fin 31, three through holes 55, through which each heat transfer tube 32 passes, are formed on the left and right in the lower row, and two on the left and right in the upper row. The through holes 55 in the upper row are positioned between the through holes 55 in the lower row in the vertical direction. Burring portions 56 rising toward the front are formed on the inner edge of each through hole 55. The left and right ends of the fin 31 are bent portions 57, 57 that are folded back toward the front side. The left bent portion 57 is fixed by abutting against the inner surface of the middle casing 12, and the right bent portion 57 is fixed by abutting against the partition member 16. The upper portion of the fin 31 is formed with a band-shaped protruding portion 58 that protrudes upward from the bent portion 57 with a left-right width smaller than the left-right width of the bent portion 57. The upper end of the protruding portion 58 is an upper straight portion 59 that extends in the left-right direction. The left-right width W1 of the upper straight portion 59 is set to be larger than the left-right width W2 of the arrangement area of ​​the three through holes 55, 55·· in the lower row. Therefore, the upper straight portion 59 overlaps in the vertical direction with the three through holes 55, 55··, i.e., the arrangement area of ​​the three heat transfer tubes 32, 32··. In the upper linear portion 59, upper semicircular portions 60, 60... are formed on the left and right ends and above the two through holes 55, 55 in the upper row.

[0017] Four offset fins 61a to 61d are formed in the vertical direction on the left and right outer sides of the two upper through holes 55, 55 of the fin 31. Three offset fins 61a to 61c are also formed in the vertical direction between the two upper through holes 55, 55. The offset fins 61a to 61d are strip-shaped and cut out toward the front and extend in the horizontal direction. The offset fins 61a to 61d overlap the lower through hole 55 in the vertical direction, respectively. At the bottom of the fin 31, between the adjacent through holes 55, 55, . . . in the lower row, notches 62, 62 are formed by cutting upward. The notches 62 have an upper end 63, an intermediate portion 64, and a lower end 65. The upper end 63 is circular and located above the left and right through holes 55, 55, and has a smaller diameter than the through hole 55. The upper end 63 is formed with a burring portion 66 that protrudes forward. The burring portion 66 abuts against the adjacent fin 31 at the front. The intermediate portion 64 is connected to the lower end of the upper end 63, and is a narrow slit that extends downward between the left and right through holes 55, 55. The lower end 65 is connected to the lower end of the intermediate portion 64, and is tapered such that the left and right width increases as it goes downward and the lower end opens. The left and right sides of the lower end 65 are curved along the shape of the through hole 55. Three lower straight portions 67, 67... extending in the left-right direction are formed at the lower end of the fin 31 divided by the notches 62. Each lower straight portion 67 is located directly below one of the three through holes 55 in the lower row. Lower semicircular portions 68, 68 are formed on both the left and right sides below each through hole 55. The left-right width W3 of each lower straight portion 67 including the lower semicircular portion 68 is formed to be larger than the diameter of the through hole 55, i.e., the diameter W4 of the heat transfer tube 32, and overlap in the up-down direction. A vertical height H1 of the fin 27 including the projection 45 shown in FIG. 4 is equal to a vertical height H2 of the fin 31 shown in FIG.

[0018] Seven embosses 70A, 70B, 70C are formed between the through holes 55, 55 in the upper and lower stages and protrude forward. Each of the embosses 70A to 70C is circular in front view, and the peripheral surface is tapered so that the diameter becomes smaller toward the front. The protruding end is a flat circle. The four central embosses 70A, 70A... are arranged in pairs on the left and right sides of the upper end 63 of the cutout portion 62, and are located slightly above the gap between the burring portion 56 of the through hole 55 in the lower stage and the burring portion 66 of the upper end 63 of the cutout portion 62. The two embossments 70B, 70B are arranged at a predetermined interval above and below at the left end of the fin 31. The embossment 70B vertically overlaps with the through-hole 55 at the left end of the lower row and the offset fin 61c in the third row from the top. One emboss 70C is disposed at the right end of the fin 31, and vertically overlaps with the through-hole 55 at the right end of the lower row and the offset fin 61c in the third row from the top. Each of the embossments 70A, 70B, 70C is formed at a height approximately half the distance between the adjacent fins 31, 31 in the front and rear, and is not in contact with the adjacent fin 31 in front.

[0019] This fin 31 is also obtained by press-molding a single sheet metal, but here, as shown in Fig. 8, an upper straight portion 59 and a lower straight portion 67 are obtained by cutting between the upper and lower fins 31, 31 along a cut-off line 71. In this case, as with the fin 27, circular holes P2, P2... are formed at both the left and right ends and at both sides of the lower end of the notch 62 before cutting. Therefore, when cutting along the cut-off line 71, an upper semicircular portion 60 and a lower semicircular portion 68 are simultaneously formed. Note that, although only two fins 31, 31, an upper one and an lower one, are shown in Fig. 8, in reality, three or more fins 31 are press-molded from a single sheet metal having three or more fins 31 connected together. Even if a lower straight portion 67 is provided at the lower end of the fin 31, the protruding portion 58 on which the upper straight portion 59 is formed is formed, so that the height cut by the lower straight portion 67 can be covered by the protruding portion 58, and there is no need to shorten the vertical dimension of the fin 31.

[0020] As shown in FIG. 2, the upper casing 13 houses a hot water supply side secondary heat exchanger 75 and a heating side secondary heat exchanger 76. Each of the heat exchangers 75, 76 has a plurality of heat absorption pipes 77, 77·· formed in a serpentine shape. Both ends of each heat absorption pipe 77 of the hot water supply side secondary heat exchanger 75 are connected to hot water supply side headers 78, 78 provided at the front and rear of the right side surface of the upper casing 13, respectively, so that one end and the other end are in communication with each other. Both ends of each heat absorption pipe 77 of the heating side secondary heat exchanger are connected to heating side headers 79, 79 provided at the front and rear of the left side surface of the upper casing 13, respectively, so that one end and the other end are in communication with each other. The upper casing 13 and the middle casing 12 are connected at their rear ends. The upper casing 13 is supported in a position inclined downwards toward the front. A drain receiver (not shown) is provided in the exhaust section 14 connected to the front side of the upper casing 13. As shown in FIG. 1, a neutralizer 80 is installed on the right side of the combustion chamber 10. The drain receiver is connected to the neutralizer 80 via a drain discharge pipe 81. The drain neutralized in the neutralizer 80 is discharged to the outside via a drain pipe 82.

[0021] A water supply pipe 85 is connected to the water inlet 3. The water supply pipe 85 is routed upward on the right side of the combustion chamber 10 and connected to the hot water supply header 78 on the front side of the upper casing 13. A hot water supply side relay pipe 86 is connected to the hot water supply side header 78 on the rear side of the upper casing 13. The hot water supply side relay pipe 86 is routed to the rear of the combustion chamber 10 and connected to the upstream end of the right end of the hot water supply side heat transfer pipe 30 of the hot water supply side primary heat exchanger 25. A hot water outlet pipe 87 is connected to the downstream end of the left end of the hot water supply side heat transfer pipe 30. The hot water outlet pipe 87 is routed from the front of the combustion chamber 10 to the right side and descends, and is connected to the hot water outlet 5. A bypass pipe 88 (FIG. 2) provided with a distribution valve (not shown) is connected between the water supply pipe 85 and the hot water supply side relay pipe 86.

[0022] A heating return pipe 89 is connected to the heating return port 7. The heating return pipe 89 is routed upward on the left side of the combustion chamber 10 via a pump 90, and is connected to the heating side header 79 on the front side of the upper casing 13. A heating side relay pipe 91 is connected to the heating side header 79 on the rear side of the upper casing 13. The heating side relay pipe 91 is routed to the rear of the middle casing 12 and connected to the upstream end of the heating side heat transfer pipe 34 (the heat transfer pipe 32 at the left end of the lower stage). A heating outgoing pipe 92 is connected to the downstream end of the heating side heat transfer pipe 34 (the upper left heat transfer pipe 32). The heating outgoing pipe 92 is routed downward from the front of the inner casing 12, and is connected to the heating outgoing port 6. The heating return port 7 and the heating supply port 6 are connected to a high-temperature radiator (e.g. a heating blower) outside the appliance via external piping, forming a circulation path in which hot water circulates between the heating side primary and secondary heat exchangers 26, 76 and the high-temperature radiator.

[0023] Meanwhile, a heating low-temperature forward pipe (not shown) is branched off and connected to the heating return pipe 89 downstream of the pump 90. The heating low-temperature forward pipe is connected to a low-temperature radiator (e.g., a floor heating) outside the appliance via an external piping. This external piping is connected to an external piping that is connected to the heating return port 7, thereby forming a low-temperature circulation path in which hot and cold water circulates between the heating return pipe 89, the heating low-temperature forward pipe, and the low-temperature radiator. The heating return pipe 89 and the heating supply pipe 92 are each branched and connected to the internal pipe of a bath heat exchanger (not shown). A bath supply pipe (not shown) equipped with a pump, which is connected to the bath heat exchanger, is connected to the bath supply port 8, and a bath return pipe (not shown) is connected to the bath return port 9. The bath supply port 8 and the bath return port 9 are each connected to an external bathtub via external piping, forming a bath circulation path in which hot and cold water circulates between the bath heat exchanger and the bathtub. A controller 95 is provided in the lower part of the box body 2 in front of the combustion chamber 10. The controller 95 has an electrical circuit board, and is connected to an external hot water / bath remote control and a heating remote control (not shown).

[0024] In the water heater 1, normal hot water supply is performed as follows. When the hot water tap of the external piping connected to the hot water outlet 5 is opened to allow water to flow into the appliance and this water flow is detected by a hot water supply amount sensor (not shown) installed in the water supply pipe 85, the controller 95 rotates the combustion fan 21 for a predetermined time to discharge the combustion exhaust gas accumulated in the combustion chamber 10 (pre-purge). After that, the controller 95 opens the main valve of the gas piping 23 and the solenoid valve of the gas distribution unit 22, opens the proportional valve to a predetermined opening degree, supplies fuel gas to each burner 20 in the first combustion chamber 17, and operates the igniter to ignite each burner 20. As a result, the water supplied from the water supply pipe 85 exchanges heat with the exhaust gas from the burner 20 as it flows through the heat absorption pipe 77 of the hot water supply side secondary heat exchanger 75, recovering latent heat. The drainage generated at this time is recovered in the neutralizer 80 via the drain discharge pipe 81, neutralized with a neutralizing agent, and then discharged from the drain pipe 82 to the outside of the appliance. The hot water that has passed through the hot water-supply side secondary heat exchanger 75 flows through the hot water-supply side relay pipe 86 to the hot water-supply side primary heat exchanger 25, and while flowing through the hot water-supply side heat transfer pipe 30, exchanges heat with the combustion exhaust gas from the burner 20 to recover sensible heat. The hot water thus heated passes through the hot water outlet pipe 87 and external piping and is discharged from the hot water tap.

[0025] 9, in the first combustion chamber 17, the combustion exhaust gas rises between the fins 27, 27..., passing between the heat transfer tubes 28, between the left-most heat transfer tube 28 and the bent portion 38, and between the right-most heat transfer tube 28A and the bent portion 38. Moreover, as shown by dotted arrow b, the combustion exhaust gas flows around to the left or right along the underside of each heat transfer tube 28, and then joins the flow indicated by dotted arrow a and rises. As the combustion exhaust gas rises in this manner, it exchanges heat by coming into contact with each of the fins 27 and each of the heat transfer tubes 28. Even if the flow speed of the combustion exhaust gas passing between the heat transfer tubes 28, 28 is high, the combustion exhaust gas comes into contact with the offset fins 37a-37c and then with the protrusions 45, so that the contact time (contact distance) between the combustion exhaust gas and the fins 27 can be increased. Therefore, heat can be efficiently collected from the combustion exhaust gas. Furthermore, in each fin 27, the temperature around the heat transfer tube 28A at the right end, which is the water inlet side, is lower than the temperature around the other heat transfer tubes 28. In this case, there is a risk of condensation forming on the upper part of the fin 27. However, here, the cutout 40A at the right end is made larger than the other cutouts 40, reducing the area around the heat transfer tube 28A, which will be at a lower temperature, so that the temperature of the upper part of the fin 27, including the projection 45A, can be increased, and the generation of drainage can be suppressed.

[0026] The controller 95 monitors the outlet temperature, which is the temperature of the hot water discharged immediately after the hot water supply side primary heat exchanger 25, using an outlet temperature thermistor installed in the hot water outlet pipe 87, and drives a distribution valve installed in the bypass pipe 88 to control the flow rate (bypass rate) to the bypass pipe 88 so that the outlet temperature is maintained within a temperature range that can prevent the generation of drainage or overheating in the hot water supply side primary heat exchanger 25. In addition, the controller 95 monitors the outlet hot water temperature using an outlet hot water temperature thermistor installed in the outlet hot water pipe 87, and controls the opening and closing of each solenoid valve in the gas distribution unit 22 and adjusts the opening of the proportional valve so that the outlet hot water temperature becomes the set temperature specified by the hot water / bath remote control, and also continuously changes the amount of air by controlling the rotation speed of the combustion fan 21. When the hot water tap is closed, the controller 95 confirms that the signal from the hot water volume sensor has stopped, closes the main valve and the solenoid valve of the gas distribution unit 22 to extinguish the burner 20, and rotates the combustion fan 21 for a predetermined period of time (post-purge).

[0027] On the other hand, when the operation switch of the heating remote control is pressed, the controller 95 operates the pump 90 to circulate hot and cold water between the heating-side primary heat exchanger 26, the heating-side secondary heat exchanger 76, and the high-temperature radiator, and opens the solenoid valve corresponding to the burner 20 in the second combustion chamber 18 in the gas distribution unit 22 to ignite the burner 20, and supplies combustion air by the combustion fan 21. Therefore, the hot and cold water flowing through the heating return pipe 89 exchanges heat with the combustion exhaust gas of the burner 20 as it flows from the heating-side header 79 to the heat absorption pipe 77 of the heating-side secondary heat exchanger 76, thereby recovering latent heat. The drainage generated at this time is also recovered in the neutralizer 80 via the drainage discharge pipe 81, neutralized, and then discharged to the outside of the appliance. The hot water that has passed through the heating-side secondary heat exchanger 76 then flows through the heating-side relay pipe 91 to the heating-side primary heat exchanger 26, and exchanges heat with the combustion exhaust gas from the burner 20 as it flows through the heating-side heat transfer pipe 34, recovering sensible heat. The hot water heated in this way is supplied to the high-temperature radiator through the heating supply pipe 92 and external piping. When the circulating hot water reaches the set temperature, the controller 95 stops the combustion of the burner 20 in the second combustion chamber 18, and stops the pump 90.

[0028] In the second combustion chamber 18, the combustion exhaust gas first rises between the fins 31, 31, passing between the three lower heat transfer tubes 32, 32, between the left-most heat transfer tube 32 in the lower row and the bent portion 57, and between the right-most heat transfer tube 32 in the lower row and the bent portion 57, as shown by the dotted arrow c in Fig. 10. The combustion exhaust gas also flows around to the left or right along the underside of each heat transfer tube 32, as shown by the dotted arrow d, and then merges with the combustion exhaust gas of the dotted arrow c and rises. Thus, the combustion exhaust gas comes into contact with the lower portion of each fin 31 and each lower-row heat transfer tube 32 to exchange heat. In this case, the lower ends of the fins 31 between each heat transfer tube 32 in the lower row are curved by the lower end portions 65 of the notches 62, so that the amount of heat absorption is ensured while also ensuring strength and reducing the risk of cracks, etc.

[0029] The exhaust gas flowing up between the heat transfer tubes 32, 32 comes into contact with the left and right embosses 70A, 70A, and branches to the lower heat transfer tube 32 side and the upper heat transfer tube 32 side as shown by dotted arrows e, e. Therefore, the exhaust gas is dispersed to the upper part of the lower heat transfer tube 32, where heat is not easily transferred, and the side part of the upper heat transfer tube 32, promoting heat absorption. Since the emboss 70A does not come into contact with the fin 31 adjacent to the front, a decrease in the flow speed of the exhaust gas can be suppressed. In particular, since the burring portion 66 of the upper end portion 63 of the cut portion 62 is located between the embossments 70A, 70A, the combustion exhaust gas passes through the flow path formed between the left and right heat transfer tubes 32, 32 and the burring portion 66, and is rectified to flow toward the embossment 70A side. Therefore, the embossment 70A is more effective in dispersing the combustion exhaust gas and promoting heat absorption. The branched combustion exhaust gas flows upward while coming into contact with the offset fins 61a to 61d as indicated by the dotted arrow f. On the other hand, the exhaust gas from the combustion passage between the left-most heat transfer tube 32 and the bent portion 57 comes into contact with the embossments 70B, 70B arranged vertically, and thus branches to the left and right as indicated by dotted arrows g, g, one of which rises along the left-side bent portion 57, and the other of which flows around to the upper side of the left-most heat transfer tube 32, before joining the flow indicated by dotted arrow f and rising. Therefore, even in a narrow space, the exhaust gas from the combustion passage can be guided to the left-most heat transfer tube 32 and the offset fins 61a-61d, and the thermal efficiency is also improved here. The exhaust gas from the combustion passage between the right-end heat transfer tube 32 and the bent portion 57 also comes into contact with the embossment 70C and branches to the left and right as indicated by dotted arrows g, g, one of which rises along the right-side bent portion 57, while the other is guided toward the offset fins 61a-61d and joins the flow of dotted arrow f and rises. Therefore, an improvement in thermal efficiency can be expected even at the right portion of the fin 31.

[0030] The heat exchanger and water heater according to the present disclosure, in which the fins are provided with cutouts and protrusions, have the following advantages. The hot water side primary heat exchanger 25 (an example of a heat exchanger) includes a plurality of fins 27 arranged at a predetermined interval in the thickness direction, and a plurality of heat transfer tubes 28 that penetrate each fin 27 and are arranged in a row at a predetermined interval in the horizontal direction, and is capable of exchanging heat between the combustion exhaust gas (an example of a fluid) passing between each fin 27 from bottom to top (an example of the up-down direction) and hot water (an example of a fluid) passing through each heat transfer tube 28. The water heater 1 is equipped with a burner 20 and a hot water side primary heat exchanger 25, and enables heat exchange between the combustion exhaust of the burner 20 passing between each fin 27 and hot water passing through each heat transfer tube 28. The lower end of each fin 27 is formed with a cutout 40 that is located between the heat transfer tubes 28, 28 in a planar view and that narrows in width as it extends upward, while the upper end of each fin 27 is formed with a protrusion 45 that is located between the heat transfer tubes 28, 28 in a planar view and protrudes upward. According to this configuration, the surface area of ​​the fins 27 can be increased by the projections 45. Therefore, even if the number of stages of the heat transfer tubes 28 is small, the thermal efficiency can be improved. In particular, the projections 45 are located between the heat transfer tubes 28, 28 in a plan view. The combustion exhaust gas flowing between the heat transfer tubes 28, 28 has a high flow rate and is difficult to exchange heat with, and passes between the fins 27 while remaining at a relatively high temperature. However, here, the projections 45 provided between the heat transfer tubes 28, 28 can efficiently recover heat even from the high-temperature combustion exhaust gas with a high flow rate.

[0031] Since each protrusion 45 is located directly above each cutout portion 40 and has a shape that matches the cutout portion 40, the cutout portion 40 that would normally be treated as waste material during press forming can be used as the protrusion 45. Therefore, even if the protrusions 45 are provided, the amount of sheet metal used does not increase, and an increase in costs can be suppressed. At the top of each fin 27 and below each protrusion 45, a number of offset fins 37a to 37c protruding in the thickness direction of the fin 27 are cut out and formed at a predetermined interval in the vertical direction, and each offset fin 37a to 37c has a horizontal width which increases from the cutout portion 40 side toward the protrusion 45 side, and the horizontal width of each offset fin 37a closest to the protrusion 45 matches the maximum horizontal width of each protrusion 45. Therefore, it is possible to improve thermal efficiency by increasing the amount of heat that can be collected by the offset fins 37a to 37c from the combustion exhaust gas that is difficult to collect heat from as it passes between the heat transfer tubes 28, 28. Furthermore, even if the offset fin 37a having the maximum width is provided, its strength can be maintained by providing it below the protrusion 45.

[0032] Each heat transfer tube 28 is connected in a serpentine manner with horizontally adjacent ends joined alternately, and heat transfer tube 28A located at one horizontal end is the inlet for hot and cold water, and cutout 40A located below heat transfer tube 28A serving as the inlet, and protrusion 45A located directly above it, have a larger area than the other cutouts 40 and other protrusions 45, respectively. Therefore, by increasing the area of ​​cutout 40A on the water inlet side, where the temperature is lowest, the low-temperature area around heat transfer tube 28A can be reduced, and the temperature of protrusion 45A can be increased. This makes it possible to prevent drainage from occurring.

[0033] The following modifications are possible with respect to the present disclosure in which the fin cutouts and protrusions are provided. In the above embodiment, holes are drilled at the apex of the cutout and the protrusion and at both the left and right ends of the cutout and the protrusion, but the shape of the holes can be changed as appropriate. However, holes may be omitted and the shapes of the cutout and the protrusion may be made completely the same. The shapes of the cutout and protrusion are not limited to the above-mentioned shapes, and may be tapered with curved left and right sides, semicircular, triangular, or the like. As long as the protrusion is disposed between the left and right heat transfer tubes, the protrusion does not have to be directly above the cutout, and the shape does not have to match the cutout. The number and size of the offset fins below the protrusion may be varied as appropriate. The width of the offset fin closest to the protrusion may be less than the maximum width of the protrusion. The offset fin may be omitted. If the water inlet side is the leftmost heat transfer tube instead of the rightmost one, the cutout on the lower side of the leftmost heat transfer tube can be made larger than the other cutouts. The same applies to the protrusions. However, all cutouts and protrusions can be made the same shape regardless of the water inlet side. The present disclosure can also be applied to a water heater that does not include a secondary heat exchanger. The present disclosure can also be applied to a water heater that is equipped only with a heat exchanger for hot water supply.

[0034] The heat exchanger and water heater according to the present disclosure, in which first and second straight portions are provided at the upper and lower ends of the fins, provide the following advantages. The heating side primary heat exchanger 26 (an example of a heat exchanger) includes multiple fins 31 arranged at a predetermined interval in the thickness direction, and multiple heat transfer tubes 32 arranged in two upper and lower rows at a predetermined interval in the horizontal direction and penetrating each of the fins 31, and is capable of exchanging heat between combustion exhaust gas (an example of a fluid) passing between each of the fins 31 from bottom to top (an example of the up-down direction) and hot water (an example of a fluid) passing through each of the heat transfer tubes 32. The water heater 1 is equipped with a burner 20 and a heating side primary heat exchanger 26, and enables heat exchange between the combustion exhaust of the burner 20 passing between each fin 31 and hot water passing through each heat transfer tube 32. The upper end of each fin 31 is formed with an upper straight portion 59 (an example of a first straight portion) extending horizontally in a range that vertically overlaps with the horizontal arrangement area of ​​all the heat transfer tubes 32, 32... in the lower tier (an example of a tier upstream in the direction of fluid passage), while the lower end of each fin 31 is formed with a lower straight portion 67 (an example of a second straight portion) extending horizontally in a range that vertically overlaps with the diameter (an example of a horizontal area) of each heat transfer tube 32 in the lower tier.

[0035] According to this configuration, the upper and lower straight sections 59, 67 ensure a large surface area for each fin 31, leading to improved thermal efficiency. In addition, the sheet metal yield during press forming is improved, and the amount of material discarded as waste material is reduced, resulting in lower costs. Therefore, even if the heat transfer tubes 32 are arranged in two levels, one above the other, the thermal efficiency can be improved with a simple configuration without hindering compactness. In particular, if the lower ends of the fins are corrugated to follow the shape of the heat transfer tube, as in conventional fins, the lower ends of each fin close to the burner become very hot and may suffer damage such as cracks after long-term use. In addition, the distance from the heat transfer tube is large, so that the contribution to heat exchange is small. However, in the above embodiment, the lower ends of the fins 31 directly below each heat transfer tube 32, which becomes hot, are cut to the lower straight portion 67, thereby improving durability. Also, since the upper straight portion 59 is formed by providing a protrusion 58 at the upper portion corresponding to the cut lower end, it is possible to improve thermal efficiency without changing the vertical height of the fins 31.

[0036] A notch 62 is formed at the lower end of each fin 31, cutting toward the space between the heat transfer tubes 32, 32 in the lower stage of the combustion exhaust, and the lower part of each notch 62 is formed in a curved shape along the outer peripheral surface of the heat transfer tube 32. Therefore, the area cut by the lower straight portion 67 is filled in, increasing the amount of heat absorption by the lower heat transfer tube 32, while reducing the risk of damage such as cracks occurring due to long-term use.

[0037] Regarding the present disclosure in which first and second straight portions are provided at the upper and lower ends of the fin, the following modifications are possible. The lower straight portion of the lower end of the fin is longer than the diameter of the lower heat transfer tube, but may be equal to the diameter. The cut portion may have only a mountain-like or tapered lower end portion without an upper end portion and an intermediate portion, and the inner edge may be curved. However, the cut portion may not be provided. The upper portion of the fin may not be provided with a protruding portion, but may instead have a first straight portion with a smaller vertical height than that of a conventional fin. The number and shape of the offset fins may be varied as appropriate, although offset fins are not required in the present disclosure. The number of heat transfer tubes in each of the upper and lower stages can be changed as appropriate. In the present disclosure, the heat transfer tubes in the upper and lower two stages do not have to be arranged alternately above and below. In the present disclosure, the fins do not need to be provided with embossments.

[0038] The heat exchanger and water heater according to the present disclosure having embossments on the fins provide the following advantages. The heating side primary heat exchanger 26 (an example of a heat exchanger) includes a plurality of fins 31 arranged at a predetermined interval in the thickness direction, and a plurality of heat transfer tubes 32 arranged in two upper and lower rows at a predetermined interval in the horizontal direction, alternating between the top and bottom, and penetrating each of the fins 31, and heat exchange is possible between the combustion exhaust gas (an example of a fluid) passing between each of the fins 31 from bottom to top (an example of the up-down direction) and hot water (an example of a fluid) passing through each of the heat transfer tubes 32. The water heater 1 is equipped with a burner 20 and a heating side primary heat exchanger 26, and enables heat exchange between the combustion exhaust of the burner 20 passing between each fin 31 and hot water passing through each heat transfer tube 32. Between the upper and lower heat transfer tubes 32, 32 of each fin 31, a plurality of embossments 70A, 70B, 70C, which are circular when viewed from the front and have a smaller diameter from the base to the tip, are formed at a predetermined interval in the horizontal direction, and each embossment 70A is positioned so as to overlap the upper and lower heat transfer tubes 32, 32 in the vertical direction, respectively. According to this configuration, by providing the easily processed embossment 70A, the combustion exhaust gas can be guided to the upper side of the lower heat transfer tube 32 where heat is less likely to be transferred, and the combustion exhaust gas can be dispersed in the left and right directions of the upper heat transfer tube 32. Therefore, even if the heat transfer tubes 32 are arranged in two tiers, one above the other, the thermal efficiency can be improved with a simple configuration without hindering compactness. In addition, the temperature distribution of the fins 31 is made uniform, which leads to the prevention of drainage, and the strength of the fins 31 can be expected to be increased by the embossment 70A.

[0039] Below each heat transfer tube 32 in the upper row (an example of a row downstream in the direction of fluid passage), a burring portion 66 (an example of a straightening portion) is formed which protrudes in the thickness direction and abuts against an adjacent fin 31 to form a flow path for the combustion exhaust between the heat transfer tube 32 in the lower row (an example of a row upstream in the direction of fluid passage), and the embossment 70A is positioned on that flow path. Therefore, the high-temperature exhaust gas that does not exchange heat with the lower heat transfer tube 32 can be dispersed to the left and right and reliably guided to the upper side of the lower heat transfer tube 32. Therefore, the dispersion effect of the exhaust gas by the embossment 70A can be further improved, and the thermal efficiency can be further increased. The embossments 70B, 70C are also disposed between the left and right bent portions 57 (an example of an edge on at least one side in the horizontal direction) of the fin 31 and the lower heat transfer tubes 32 adjacent to the respective bent portions 57. Therefore, the combustion exhaust gas can be guided to the heat transfer tube 32 side even in a narrow space, which contributes to further improvement of thermal efficiency.

[0040] The following modifications are possible for the present disclosure in which fins are provided with embossments. The number of embossments is not limited to the above-mentioned form and can be changed as appropriate. For example, the number of embossments arranged between the upper and lower heat transfer tubes may be increased from the above-mentioned form. The number of embossments between the left and right bent portions and the lower heat transfer tube can also be increased or decreased as appropriate. However, the embossments on the left and right bent portions may not be required. The size of the embossments does not need to be the same for all, and for example, the embossments between the upper and lower heat transfer tubes may be made larger in diameter than the embossments on the left and right. The embossments may be formed at a height such that they abut adjacent fins. The burring portion provided below the upper heat transfer tube is not limited to a circular shape when viewed from the front, and may be, for example, an oval or elliptical shape extending in the left-right direction when viewed from the front. The flow straightening portion is not limited to the burring portion, and may be formed by a cut and raised wall, etc. The flow straightening portion may be omitted. The number of heat transfer tubes in each of the upper and lower stages can be changed as appropriate. The number and shape of the offset fins may be varied as appropriate, although offset fins are not required in the present disclosure. In the present disclosure, the fin does not need to have straight sections at the top and bottom ends.

[0041] In addition, as is common to all disclosures, the number of burners, the shape of the combustion chamber, the arrangement of the neutralizer and controller, etc. can be changed as appropriate. In the above embodiment, the heating primary and secondary heat exchangers are installed in the second combustion chamber, but instead, a bath primary and secondary heat exchanger may be installed. In the above configuration, the exhaust gas flows from bottom to top, but the disclosures can also be applied to a reverse combustion water heater in which the fan unit, burner, primary heat exchanger, and secondary heat exchanger are arranged in order from the top of the combustion chamber, and the exhaust gas flows from top to bottom. In this case, the cutout portion is the upper end of the fin, and the protrusion is the lower end of the fin. The first straight portion is the lower end of the fin, the second straight portion is the upper end of the fin, and the cut portion is formed downward from the upper end of the fin. [Explanation of symbols]

[0042] 1...water heater, 2...box body, 10...combustion chamber, 11...lower casing, 12...middle casing, 13...upper casing, 14...exhaust section, 17...first combustion chamber, 18...second combustion chamber, 20...burner, 21...combustion fan, 22...gas distribution unit, 25...hot water side primary heat exchanger, 26...heating side primary heat exchanger, 27, 31...fins, 28, 32...heat transfer tubes, 30...hot water side transfer Heat tube, 34··Heating side heat transfer tube, 37a~37c··Offset fin, 40··Cutout portion, 45··Protrusion, 51, 71··Cut-off line, 59··Upper straight portion, 62··Notched portion, 66··Burning portion, 67··Lower straight portion, 70A, 70B, 70C··Embossment, 75··Hot water side secondary heat exchanger, 76··Heating side secondary heat exchanger, 85··Water supply pipe, 87··Hot water outlet pipe, 95··Controller.

Claims

1. A heat exchanger including a plurality of fins arranged at predetermined intervals in a thickness direction, and a plurality of heat transfer tubes penetrating each of the fins and arranged in a row at predetermined intervals in a horizontal direction, capable of exchanging heat between a fluid passing between each of the fins in a vertical direction and a fluid passing through each of the heat transfer tubes, At the lower end or upper end of each of the fins, a cutout portion is formed that is located between the heat transfer tubes in a plan view and that narrows in width as it goes upward or downward, A heat exchanger characterized in that a protrusion that protrudes upward or downward is formed on the upper or lower end of each of the fins and is located between the heat transfer tubes in a plan view.

2. 2. The heat exchanger according to claim 1, wherein each of the projections is located directly above or below each of the cutouts and is shaped to match the cutouts.

3. 3. A heat exchanger as described in claim 1 or 2, characterized in that a plurality of offset fins protruding in the thickness direction of the fin are cut out and formed at a predetermined interval in the vertical direction on the upper or lower part of each fin and on the lower or upper side of each protrusion, and each offset fin has a horizontal width which increases from the cutout side toward the protrusion side, and the horizontal width of each offset fin closest to the protrusion is formed to be the same as or smaller than the maximum horizontal width of each protrusion.

4. The heat transfer tubes are connected in a serpentine shape in which adjacent ends in the horizontal direction are alternately connected, and the heat transfer tube located at one end in the horizontal direction serves as an inlet side for a fluid, 3. The heat exchanger according to claim 1, wherein the cutout portion located on the lower or upper side of the heat transfer tube on the inlet side and the protrusion located directly above or directly below the cutout portion have a larger area than the other cutout portions and the other protrusions, respectively.

5. A water heater comprising a burner and the heat exchanger according to claim 1 or 2, and characterized in that heat exchange is possible between the combustion exhaust gas of the burner passing between each of the fins and hot water passing through each of the heat transfer tubes.

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