Plate-type heat exchanger

[0022]Hereinafter, referring to drawings, a heat exchanger and a heat source device using thereof according to an embodiment of the present invention will be described in detail.

[0023]As illustrated in FIG. 1, a heat source device according to the present embodiment is a water heater that heats water (heat medium) as first fluid flowing into a heat exchanger 1 through an inlet pipe 20, with combustion exhaust gas as second fluid generated in a burner 31 and supplies the heated water to a hot water supplying terminal (not illustrated) such as a faucet or a shower head through an outlet pipe 21. Although not shown, the water heater is accommodated in an outer casing. Other heating medium (for example, an antifreezing fluid) as the first fluid may be used.

[0024]The water heater includes a burner body 3 constituting an outer shell of the burner 31, a combustion chamber 2, the heat exchanger 1, and a drain receiver 40 that are disposed in this order from above. Additionally, the fan casing 4 housing a combustion fan for feeding a mixture gas of fuel gas and air into the burner body 3 is disposed on one side (a right side in FIG. 1) of the burner body 3. Further, an exhaust duct 41 communicating with the drain receiver 40 is disposed on another side (a left side in FIG. 1) of the burner body 3. The combustion exhaust gas flowing out to the drain receiver 40 is discharged to an outside of the water heater through the exhaust duct 41.

[0025]In this specification, when the water heater is viewed in a state where the fan case 4 and the exhaust duct 41 are disposed on the sides of the burner body 3, a depth direction corresponds to a front-rear direction, a width direction corresponds to a left-right direction, and a height direction corresponds to a vertical direction.

[0026]The burner body 3 has a substantially oval shape in a plan view. The burner body 3 is made of stainless steel-based metal, for example. Although not shown, the burner body 3 opens downward.

[0027]An introducing unit communicating with the fan case 4 projects upward from a center of the burner body 3. The burner body 3 includes a flat burner 31 having a downward combustion surface 30. The mixture gas is supplied to the burner body 3 by rotating the combustion fan.

[0028]The burner 31 is of all primary air combustion type. The burner 31 includes a ceramic combustion plate having many flame ports opening downwardly (not shown) or a combustion mat made by knitting metal fabric woven like net. The mixture gas supplied into the burner body 3 is jetted downward from the downward combustion surface 30 by supply pressure of the combustion fan. By igniting the mixture gas, flame is formed on the combustion surface 30 of the burner 31 and the combustion exhaust gas is generated. Therefore, the combustion exhaust gas ejected from the burner 31 is fed to the heat exchanger 1 via the combustion chamber 2. Then, the combustion exhaust gas having passed through the heat exchanger 1 passes through the drain receiver 40 and the exhaust duct 41 and is discharged to the outside of the water heater.

[0029]In other word, as indicated by a dashed line in FIG. 1, in the heat exchanger 1, an upper side where the burner 31 is provided corresponds to an upstream side of a gas flow passage of the combustion exhaust gas, and a lower side opposite to the side provided with the burner 31 corresponds to a downstream side of the gas flow passage of the combustion exhaust gas.

[0030]The combustion chamber 2 has a substantially oval shape in a plan view. The combustion chamber 2 is made of stainless steel-based metal, for example. The combustion chamber 2 having an upper opening and a lower opening is formed by bending one single metal plate having a substantially rectangular shape and joining both ends thereof.

[0031]As illustrated in FIG. 2, the heat exchanger 1 has a substantially oval shape in a plan view. The heat exchanger 1 is of the plate-type heat exchanger formed by stacking a plurality of (in this embodiment, thirteen) thin plate heat exchange units 10. The heat exchanger 1 may have a housing surrounding an outer circumference thereof.

[0032]As illustrated in FIGS. 2 and 3, the heat exchanger 1 includes a plurality of blocks 5 (in this embodiment, four blocks) stacked on top of each other. Each of the blocks 5 includes one or more heat exchange units 10. In the following, the blocks 5 will be simply referred to a “block 5” as a generic term in some cases. In addition, in accordance with the gas flow passage of the combustion exhaust gas, an uppermost block 5 will be referred to as a “most upstream block 5a” . An upper one of the middle blocks 5 will be referred to as a “first downstream-side block 5b”, and a lower one of the middle blocks 5 will be referred to as a “second downstream-side block 5c” . A lowermost block 5 will be referred to as a “most downstream block 5d”. The most upstream block 5a and first downstream-side block 5b are formed of one heat exchange unit 10, respectively. The second downstream-side block 5c is formed of five heat exchange units 10 stacked on top of each other, and the most downstream block 5d is formed of six heat exchange units 10 stacked on top of each other. The heat exchanger 1 may have three or less or five or more blocks 5. As described later, in a case where one block 5 includes a plurality of heat exchange units 10, water flow passages in the respective heat exchange units 10 of the block 5 extend in parallel such that the water flows in the same direction. In each block 5, adjacent two of heat exchange units 10 communicate with each other such that the water flows upward from below. Further, adjacent two of blocks 5 communicate with each other such that the water flows upward from below. Further, as indicated by a solid arrow in FIG. 3, in the adjacent blocks 5, the water flow passage in each heat exchange unit 10 of one block 5 is opposite in direction to the water flow passage in each heat exchange unit 10 of another block 5. Therefore, the water flow passage in each block 5 is folded back between the adjacent blocks 5 such that the heat exchanger 1 includes 4 passages (4-PASS) in accordance with the number of blocks 5. As a result, the water flow passage in the heat exchanger 1 becomes longer, resulting in improvement in heat efficiency.

[0033]Next, a configuration of the heat exchanger 1 will be described. Each of the heat exchange units 10 is formed by stacking a set of an upper heat exchange plate 11 and a lower heat exchange plate 12 in the vertical direction and joining predetermined portions (to be described later) with brazing material or the like. The upper and lower heat exchange units 11, 12 of each of the heat exchange units 10 respectively have a common configuration, except that part of configuration such as positions of upper and lower through holes, and presence or absence of water passage holes in the corners. In the following, therefore, a description will mainly be given of a configuration of one of the heat exchange units 10. For clarity sake, the dimensions of elements which are represented in the figures do not correspond to the actual dimensions, and do not limit the embodiment.

[0034]As illustrated in FIGS. 2 and 4 to 6, the upper and lower heat exchange plates 11, 12 respectively have a substantially oval shape in a plan view. The upper and lower heat exchange plates 11, 12 are made of stainless steel-based metal, for example. The upper heat exchange plate 11 has a number of upper through holes 11a on a substantially entire surface thereof except for corners, and upper through hole flange portions 11c formed at peripheral edges of the respective upper through holes 11a. The lower heat exchange plate 12 also has a number of lower through holes 12a on a substantially entire surface thereof, and lower through hole flange portions 12c formed at peripheral edges of the respective lower through holes 12a.

[0035]On peripheral edges of the upper and lower heat exchange plate 11, 12, upper and lower peripheral edge joints W1, W2 projecting upward and serving as an outer peripheral flange portion are respectively formed. Each of the upper and lower peripheral edge joints W1, W2 includes an inclined wall that expands upward at a predetermined angle such that an upper end of the inclined wall is located obliquely upward and outward of a proximal end of the inclined wall. Therefore, in each heat exchange unit 10, the upper heat exchange plate 11 is fitted into the lower heat exchange plate 12 with the upper heat exchange plate 11 stacked on the lower heat exchange plate 12. Further, in the adjacent heat exchange units 10, the lower heat exchange plate 12 of the upper heat exchange unit 10 is fitted into the upper heat exchange plate 11 of the lower heat exchange unit 10. As a result, in the upper and lower heat exchange plates 11, 12 stacked on top of each other, the upper and lower peripheral edge joints W1, W2 overlap each other by a predetermined overlapping margin Hp in the stacking direction of the heat exchange units 10 (see FIG. 8).

[0036]The upper and lower heat exchange plates 11, 12 forming one heat exchange unit 10 are set such that when the lower peripheral edge joint W2 of the lower heat exchange plate 12 and a lower surface peripheral edge of the upper heat exchange plate 11 are joined together, the upper and lower heat exchange plates 11, 12 are spaced from each other at a gap with a predetermined height . Further, the upper and lower heat exchange plates 11, 12 are set such that when the upper peripheral edge joint W1 of the upper heat exchange plate 11 and a lower surface peripheral edge of the lower heat exchange plate 12 of an upward adjacent heat exchange unit 10 are joined together, the upper heat exchange plate 11 of a lower heat exchange unit 10 and the lower heat exchange plate 12 of the upward adjacent upper heat exchange unit 10 are spaced from each other at a gap with a predetermined height.

[0037]Therefore, when the upper and lower heat exchange plates 11, 12 are joined together, an internal space 14 having the predetermined height is defined between a lower surface of the upper heat exchange plate 11 and an upper surface of the lower heat exchange plate 12 (see FIG. 3). In addition, when the heat exchange units 10 are joined together, an exhaust space 15 having the predetermined height is defined between vertically adjacent upper and lower ones of the heat exchange units 10 (see FIG. 3).

[0038]The upper through holes 11a each having a substantially square shape in a plan view are bored in a lattice pattern at a predetermined interval in the front-rear and left-right directions over substantially the entire surface of the upper heat exchange plate 11, except for a peripheral region. The lower through holes 12a each having a substantially square shape in a plan view are also bored in a lattice pattern at a predetermined interval in the front-rear and left-right directions over substantially the entire surface of the lower heat exchange plate 12, except for a peripheral region. Each of the upper through hole flange portions 11c, which are formed at the peripheral edges of the upper through holes 11a each having the substantially square shape in a plan view, extends circumferentially outwardly and substantially horizontally from an open edge of the corresponding upper through hole 11a, and has a substantially square contour in a plan view. Each of the lower through hole flange portions 12c, which are formed at the peripheral edges of the lower through holes 12a each having the substantially square shape in a plan view, extends circumferentially outwardly and substantially horizontally from an open edge of the corresponding lower through hole 12a, and has a substantially square contour in a plan view. The upper through holes 11a each having a substantially pentagonal shape in a plan view are bored at a predetermined interval in the front-rear or left-right direction in the peripheral region of the upper heat exchange plate 11. The lower through holes 12a each having a substantially pentagonal shape in a plan view are also bored at a predetermined interval in the front-rear or left-right direction in the peripheral region of the lower heat exchange plate 12. Further, each of the upper through hole flange portions 11c, which are formed on the peripheral edges of the upper through holes 11a each having the substantially pentagonal shape in a plan view, extends circumferentially outwardly and substantially horizontally from an open edge of the corresponding upper through hole 11a, and has a substantially pentagonal contour in a plan view. Each of the lower through hole flange portions 12c, which are formed on the peripheral edges of the lower through holes 12a each having the substantially pentagonal shape in a plan view, extends circumferentially outwardly and substantially horizontally from an open edge of the corresponding lower through hole 12a, and has a substantially pentagonal contour in a plan view. The upper and lower through holes 11a, 12a may have other shapes such as a substantially circular shape or a substantially elliptical shape respectively. All upper and lower through holes 11a, 12a may have the same size and shape. Further, all upper and lower through hole flange portions 11c, 12c may have the same size and shape.

[0039]The upper and lower through holes 11a, 12a and the upper and lower through hole flange portions 11c, 12c are formed at positions corresponding to each other in the vertical direction when the upper and lower heat exchange plates 11, 12 are stacked on top of each other. Further, the upper and lower through holes 11a, 12a and the upper and lower through hole flange portions 11c, 12c are respectively formed, by drawing, on a bottom of a step portion projecting inward such that the facing upper and lower through hole flange portions 11c, 12c come into surface contact with each other when the upper and lower heat exchange plates 11, 12 are stacked on top of each other.

[0040]Therefore, when the upper and lower heat exchange plates 11, 12 are stacked on top of each other and the upper and lower through hole flange portions 11c, 12c are joined by brazing material or the like, flange portions 16 closing the internal space 14 are formed by the upper and lower through hole flange portions 11c, 12c (see FIG. 8) . Further, through holes 13 penetrating the internal space 14 in a non-communicating state are formed by the upper and lower through holes 11a, 12a. In other word, the internal space 14 does not communicate with an interior of the through hole 13.

[0041]The upper heat exchange plate 11 has an upper water passage hole 11e bored in at least one of the corners, except for the upper heat exchange plate 11 of an uppermost heat exchange unit 10 (hereinafter, referred to as a “most upstream heat exchange unit 10a”) . The lower heat exchange plate 12 has a lower water passage hole 12e bored in at least one of the corners. In each heat exchange unit 10, the upper water passage hole 11e in at least one of the corners of the upper heat exchange plate 11 and the lower water passage hole 12e in at least one of the corners of the lower heat exchange plate 12 are bored so as to communicate with the internal space 14 defined between the upper and lower heat exchange plates 11, 12 when the upper and lower heat exchange plates 11, 12 are stacked on top of each other.

[0042]Further, the upper water passage hole flange portions 11f, which are formed on peripheral edges of the upper water passage holes 11e, extend circumferentially outwardly and substantially horizontally from open edges 11h of the corresponding upper water passage water passage holes 11e. The lower water passage hole flange portions 12f, which are formed on peripheral edges of the lower water passage holes 12e, extend circumferentially outwardly and substantially horizontally from open edges 12h of the corresponding lower water passage holes 12e. The upper water passage holes 11e of the upper heat exchange plate 11 are formed at positions corresponding to the lower water passage holes 12e of the lower heat exchange plate 12 of the upward adjacent heat exchange unit 10 in the vertical direction, when the adjacent two of the heat exchange units 10 are stacked on top of each other. The upper water passage hole flange portions 11f of the upper heat exchange plate 11 are formed at positions corresponding to the lower water passage hole flange portions 12f of the lower heat exchange plate 12 of the upward adjacent heat exchange unit 10 in the vertical direction, when the adjacent two of the heat exchange units 10 are stacked on top of each other. Further, the upper water passage holes 11e and the upper water passage hole flange portions 11f are respectively formed, by drawing, on a bottom of a step portion projecting outward such that the facing upper and lower water passage hole flange portions 11f, 12f come into surface contact with each other when the upper heat exchange plate 11 of one heat exchange unit 10 and the lower heat exchange plate 12 of the upward adjacent heat exchange unit 10 are stacked on top of each other. The lower water passage holes 12e and the lower water passage hole flange portions 12f are respectively formed, by drawing, on a bottom of a step portion projecting outward such that the facing upper and lower water passage hole flange portions 11f, 12f come into surface contact with each other when the lower heat exchange plate 12 of the one heat exchange unit 10 and the upper heat exchange plate 11 of a downward adjacent heat exchange unit 10 are stacked on top of each other. The upper and lower water passage holes 11e, 12e have the substantially same size and shape, and the upper and lower water passage hole flange portions 11f, 12f have the substantially same size and shape.

[0043]Therefore, when the upper heat exchange plates 11 of the lower heat exchange unit 10 of the adjacent heat exchange units 10 and the lower heat exchange plate 12 of the upper heat exchange unit 10 of the adjacent heat exchange units 10 are stacked on top of each other and the upper and lower water passage hole flange portions 11f, 12f are joined by brazing material or the like, water passage flange portions 64 closing the exhaust space 15 between the adjacent heat exchange units 10 are formed by the upper and lower water passage flange portions 11f, 12f (see FIG. 8). Further, water passage holes 63 communicating with the internal spaces 14 are formed by the facing upper and lower water passage holes 11e, 12e of the adjacent heat exchange units 10. In addition, the internal space 14 extends upward and downward at the peripheral edges of the upper and lower water passage holes 11e, 12e, so that the portion of the internal space 14 at the peripheral edges of the upper and lower water passage holes 11e, 12e is vertically wider than the remaining portion of the internal space 14. Therefore, in each heat exchange unit 10, an upper recess 65 recessed upward is formed at the peripheral edge of the upper water passage hole 11e. Also, in each heat exchange unit 10, a lower recess 66 recessed downward at the peripheral edge of the lower water passage hole 12e.

[0044]The lower water passage holes 12e are formed by burring. Thus, as shown in FIGS. 7 and 8, the lower water passage hole 12e has on its opening edge 12h an insertion wall 12j protruding downward (i.e., a downstream side of the gas flow passage of the combustion exhaust gas). Further, the insertion wall 12j disposed on the opening edge 12h of the lower water passage hole 12e, except for the lower water passage holes 12e in the lower heat exchange plate 12 of the heat exchange unit 10 located on the most downstream side of the gas flow passage of the combustion exhaust gas (hereinafter, referred to as a “most downstream heat exchange unit 10s”) and the lower water passage holes 12e in the rear right corners of the lower heat exchange plates 12 of the remaining heat exchange units 10, includes a tubular portion 12m extending downward from the opening edge 12h of the lower water passage hole 12e and a plurality of claw portions 12n protruding downward from a lower end of the tubular portion 12m. The claw portions 12n are circumferentially spaced by a predetermined angle (e.g., 120 degrees) apart from each other. Therefore, the insertion wall 12j has a distal end with a circumferentially discontinuous protrusion height. The insertion wall 12j also includes a cutout 12p of a certain width between two of the claw portions 12n.

[0045]With regard to the insertion wall 12j, a maximum protrusion height Hs of the distal end protruding downward from the upper water passage hole 11e when the upper and lower heat exchange plates 11, 12 are stacked on top of each other (i.e., a protrusion height of a lower end of each claw portion 12n) is larger than the overlapping margin Hp between the lower peripheral edge joint W2 of the lower heat exchange plate 12 including the insertion wall 12j and the upper peripheral edge joint W1 of the upper heat exchange plate 11 of the downward adjacent heat exchange unit 10 having the upper water passage hole 11e into which the insertion wall 12j is inserted. Note that the insertion wall 12j may include two or less or four or more claw portions 12n. Further, the claw portions 12n may be different in height from one another. The insertion wall 12j does not necessarily include the tubular portion 12m, but may include only the claw portions 12n.

[0046]In the insertion wall 12j, the tubular portion 12m has an outer diameter slightly smaller than an inner diameter of the upper water passage hole 11e located opposite the tubular portion 12m, and the distal end of each claw portion 12n has an outer diameter slightly smaller than the outer diameter of the tubular portion 12m. Namely, the insertion wall 12j is formed such that its distal end is located radially inward of its proximal end.

[0047]Therefore, in the state in which the upper and lower heat exchange plates 11, 12 are properly stacked on top of each other, the insertion wall 12j on the lower water passage hole 12e in the lower heat exchange plate 12 is inserted in the upper water passage hole 11e in the upper heat exchange plate 11 of the downward adjacent heat exchange unit 10, and the distal end of the insertion wall 12j protrudes downward of the upper water passage hole flange portion 11f of the downward adjacent heat exchange unit 10. Namely, in the present embodiment, with regard to the adjacent heat exchange units 10, the lower water passage hole 12e in the lower heat exchange plate 12 of the upper heat exchange unit 10 of the adjacent heat exchange units 10 corresponds to a first opening, and the upper water passage hole 11e in the upper heat exchange plate 11 of the lower heat exchange unit 10 of the adjacent heat exchange units 10 corresponds to a second opening. In addition, in the present embodiment, with regard to the adjacent heat exchange units 10, the upper heat exchange unit 10 corresponds to one heat exchange unit, and the lower heat exchange unit 10 corresponds to another heat exchange unit. Note that the upper water passage hole 11e may be formed by burring.

[0048]As illustrated in FIG. 3, the heat exchange units 10 are arranged such that, as to the adjacent heat exchange units 10, the through hole 13 in one heat exchange unit 10 is shifted from the through hole 13 in another heat exchange unit 10 in a lateral direction perpendicularly intersecting the direction of the gas flow passage of the combustion exhaust gas. In other word, the vertically adjacent heat exchange units 10 are disposed such that a projection plane of the through hole 13 in the one heat exchange unit 10 does not overlap the through hole 13 in the other heat exchange unit 10. Therefore, as indicated by a dashed line, the combustion exhaust gas flowing from the upstream side passes through the through hole 13 in the one heat exchange unit 10, and then flows out to the exhaust space 15 between the one heat exchange unit 10 and the downstream adjacent heat exchange unit 10. Then, the combustion exhaust gas flowing out to the exhaust space 15 collides with the upper heat exchange plate 11 of the downstream adjacent heat exchange unit 10 and further flows from the through hole 13 in the downstream adjacent heat exchange unit 10 toward the downstream side. Namely, when the combustion exhaust gas flows from the upstream side toward the downstream side in the heat exchanger 1, a zigzag-shaped gas flow passage is formed in the heat exchanger 1. As a result, in the heat exchanger 1, a contact time between the combustion exhaust gas and the upper and lower heat exchange plates 11, 12 increases.

[0049]With reference to FIG. 3, next, a description will be given of the flows of combustion exhaust gas and water in the heat exchanger 1. Each block 5 has an introduction port 71 for introducing water into the block 5, and a lead-out port 72 for leading the water out of the block 5. In each block 5, predetermined at least one of the lower water passage holes 12e in the heat exchange unit 10 located on a most downstream side of the gas flow passage of the combustion exhaust gas forms the introduction port 71. In each of the blocks 5b, 5c, and 5d excluding the uppermost block 5a, predetermined at least one of the upper water passage holes 11e in the heat exchange unit 10 located on a most upstream side of the gas flow passage of the combustion exhaust gas and a predetermined one of lower water passage holes 12e in the heat exchange unit 10 of the uppermost block 5a form the lead-out port 72. Note that in FIG. 3, parts such as the flange portions 16 and the insertion wall 12j are omitted for simplicity of illustration.

[0050]The inlet pipe 20 is inserted in the lower water passage hole 12e in the front right corner of the lower heat exchange plate 12 of the most downstream heat exchange unit 10s. The outlet pipe 21 is inserted in the lower water passage hole 12e in the rear right corner of the lower heat exchange plate 12 of the most downstream heat exchange unit 10s. The outlet pipe 21 extends upward from the most downstream heat exchange unit 10s to the most upstream heat exchange unit 10a so as to penetrate a part of the heat exchanger 1. An upper end of the outlet pipe 21 is inserted in the lower water passage hole 12e in the rear right corner of the lower heat exchange plate 12 of the most upstream heat exchange unit 10a.

[0051]The upper end opening of the outlet pipe 21 communicates with the internal space 14 in the most upstream heat exchange unit 10a. Further, when the outlet pipe 21 is inserted from the most downstream heat exchange unit 10s to the most upstream heat exchange unit 10a, the outlet pipe 21 passes through, in a non-communicating state, all the internal spaces 14 in the heat exchange units 10 except for the internal space 14 of the most upstream heat exchange unit 10a. Further, the outlet pipe 21 passes through, in a non-communicating state, all the exhaust spaces 15 between the adjacent heat exchange units 10. In other word, the outlet pipe 21 does not communicate with the internal spaces 14 of the heat exchange units 10 except for the most upstream heat exchange unit 10a. Further, the outlet pipe 21 does not communicate with all the exhaust spaces 15 between the adjacent heat exchange units 10.

[0052]Accordingly, when the water flows into the internal space 14 in each heat exchange unit 10 of the most downstream block 5d through the lower water passage hole 12e (the introduction port 71) in the front right corner, then the water laterally flows through the internal space 14 in one direction (from right to left in FIG. 3). When the water flows into the internal space 14 of each heat exchange unit of the second downstream-side block 5c through each of the upper and lower water passage holes 11e, 12e (namely, the lead-out port 72 and the introduction port 71) in front and rear left corners, then the water laterally flows through the internal space 14 in one direction (from left to right in FIG. 3). The water flow passage in the internal space 14 in each heat exchange unit of the second downstream-side block 5c is opposite in direction to that of the most downstream block 5d. Further, when the water flows into the internal space 14 in the heat exchange unit (hereinafter, referred to as a “second heat exchange unit 10b”) of the first downstream-side block 5b through the upper and lower water passage holes 11e, 12e (namely, the lead-out port 72 and the introduction port 71) in a front right corner, then the water laterally flows through the internal space 14 in one direction (from right to left in FIG. 3). The water flow passage in the internal space 14 in the second heat exchange unit 10b is opposite in direction to that of the second downstream-side block 5c. Further, when the water flows into the internal space 14 in the most upstream heat exchange unit 10a through each of the upper and lower water passage holes 11e, 12e (namely, the lead-out port 72 and the introduction port 71) in front and rear left corners, then the water laterally flows through the internal space 14 in one direction (from left to right in FIG. 3). The water flow passage in the internal space 14 in the most upstream heat exchange unit 10a is opposite in direction to that of the heat exchange unit 10b. After the water flows through the internal space 14 in the most upstream heat exchange unit 10a, the water flows into the outlet pipe 21 connected to the lower water passage hole 12e (namely, the lead-out port 72) in the rear right corner of the most upstream heat exchange unit 10a. When the water flows into the outlet pipe 21, then the water flows downward through the outlet pipe 21, and flows out of the heat exchanger 1. As described above, the most upstream heat exchange unit 10a and second heat exchange unit 10b in an upstream region of the gas flow passage of the combustion exhaust gas are connected in series such that the whole of water, which has flowed into the second heat exchange unit 10b, flows into the most upstream heat exchange unit 10a. In addition, the plurality of heat exchange units 10 of the most downstream block 5d are connected in parallel such that multiple flow passages are formed in parallel. A configuration of the second downstream-side block 5c is similar to that of the most downstream block 5d.

[0053]Next, a description will be given of a method for manufacturing the heat exchanger 1 according to the present embodiment. One lower frame plate 101, the predetermined number of upper heat exchange plates 11, the predetermined number of lower heat exchange plates 12, and one upper frame plate 102 are stacked while a joining material such as a brazing material is applied to predetermined portions of these plates. Although not illustrated, the outer diameter of the tubular portion 12m of the lower water passage hole 12e in the lower heat exchange plate 12 of the most downstream heat exchange unit 10s is slightly smaller than an inner diameter of a corresponding one of openings in the lower frame plate 101.

[0054]Next, an upper end of the inlet pipe 20 is inserted into the lower water passage hole 12e in the front right corner of the most downstream heat exchange unit 10s, through one opening in the lower frame plate 101. The outlet pipe 21 is inserted upward into the lower water passage hole 12e in the rear right corner of the most downstream heat exchange unit 10s, through another opening in the lower frame plate 101. A joining material such as a brazing material is applied to an outer peripheral surface of the inlet pipe 20 inserted in the lower water passage hole 12e in the front right corner of the most downstream heat exchange unit 10s and an outer peripheral surface of the outlet pipe 21 inserted in the lower water passage hole 12e in the rear right corner of the most downstream heat exchange unit 10s. A subassembly prepared as described above is subjected to brazing treatment in a furnace. The heat exchanger 1 is thus manufactured.

[0055]As described above, in the adjacent heat exchange units 10, the upper and lower water passage holes 11e, 12e, which are located opposite each other, form the water passage hole 63 serving as a communication path allowing the internal spaces 14 in the adjacent heat exchange units 10 to communicate with each other. In the plate-type heat exchanger 1 including the multiple upper and lower heat exchange plates 11, 12 alternately stacked on top of each other, an assembly error tends to cause misalignment of the upper and lower water passage holes 11e, 12e located opposite each other. As a result, in the adjacent heat exchange units 10, the upper heat exchange plate 11 of the lower heat exchange unit 10 and the corresponding lower heat exchange plate 12 of the upper heat exchange unit 10 are not properly joined together, so that an assembly failure may occur at the water passage hole flange portion 64 on the peripheral edge of the water passage hole 63. The assembly failure causes communication between the internal space 14 and the exhaust space 15, resulting in leakage of water into the exhaust space 15 through the peripheral edge of the water passage hole 63.

[0056]In view of this, according to the present embodiment, the insertion wall 12j extending downward is provided on the peripheral edge of the lower water passage hole 12e that forms the water passage hole 63. If the heat exchange units 10 are not properly stacked, the insertion wall 12j protruding downward from the peripheral edge of the lower water passage hole 12e runs onto an upper surface of the upper heat exchange plate 11 at the peripheral edge of the upper water passage hole 11e, so that the lower heat exchange plate 12 located above the upper heat exchange plate 11 is inclined. This facilitates recognition of the assembly failure.

[0057]In addition, according to the present embodiment, the claw portions 12n are provided on the distal end of the insertion wall 12j to make the protrusion height of the insertion wall 12j circumferentially discontinuous. Accordingly, even when one of the claw portions 12n is located in the downward upper water passage hole 11e, if the remaining claw portions 12n run onto the peripheral edge of the upper water passage hole 11e due to the assembly error, the lower heat exchange plate 12 located above the upper heat exchange plate 11 is inclined in a manner similar to that described above. This enables recognition of the assembly failure with reliability.

[0058]Further, according to the present embodiment, the insertion wall 12j protrudes inward of the internal space 14 in the downward adjacent heat exchange unit 10, through the upper water passage hole 11e. Therefore, when the water passes by the upper water passage hole 11e, the insertion wall 12j tends to increase flow resistance of the water. However, according to the present embodiment, since the insertion wall 12j has the distal end with the discontinuous protrusion height, the insertion wall 12j has in its distal end the cutouts 12p. With this configuration, even when the insertion wall 12j protrudes inward of the internal space 14 in the downward adjacent heat exchange unit 10, the water passes through the cutouts 12p with less decrease in the water flow passage near the upper water passage hole 11e. This configuration thus suppresses increase in flow resistance of the water passing through the internal space 14 due to the insertion wall 12j. Particularly in the present embodiment, the upper recess 65 recessed upward (toward one side in the stacking direction of the heat exchange units 10) is provided at the peripheral edge of the upper water passage hole 11e in which the insertion wall 12j is inserted. This configuration prevents the insertion wall 12j from largely protruding inward of the internal space 14 in the downward adjacent heat exchange unit 10. This configuration thus further suppresses increase in flow resistance of the water. With regard to the adjacent heat exchange units 10, this configuration therefore allows the water to smoothly flow from the internal space 14 in the lower heat exchange unit 10 to the internal space 14 in the upper heat exchange unit 10. This configuration suppresses reduction in heat efficiency.

[0059]Furthermore, according to the present embodiment, the heat exchange units 10 are stacked on top of each other such that the lower surface peripheral edge of the lower heat exchange plate 12 is fitted into the upper peripheral edge joint W1 as the outer peripheral flange portion on the peripheral edge of the upper heat exchange plate 11 while the lower surface peripheral edge of the upper heat exchange plate 11 is fitted into the lower peripheral edge joint W2 as the outer peripheral flange portion on the peripheral edge of the lower heat exchange plate 12. The upper and lower heat exchange plates 11, 12 are stacked to overlap each other with the predetermined overlapping margin Hp when the insertion wall 12j is properly inserted in the upper water passage hole 11e. On the other hands, the maximum protrusion height Hs of the distal end of the insertion wall 12j is larger than the overlapping margin Hp. Therefore, when the insertion wall 12j runs onto the peripheral edge of the upper water passage hole 11e due to the assembly error, a gap is defined between the peripheral edges of the adjacent heat exchange units 10. Namely, in the present embodiment, with regard to one heat exchange unit 10, the upper heat exchange plate 11 corresponds to a first heat exchange plate, and the lower heat exchange plate 12 corresponds to a second heat exchange plate. Further, with regard to the adjacent heat exchange units 10, the lower heat exchange plate 12 of the upward adjacent heat exchange unit 10 located above the lower heat exchange unit 10 (located on one side in the stacking direction of the heat exchange units 10) corresponds to a proximate heat exchange plate. Especially, according to the present embodiment, since the water passage hole 63 is provided in the corner on the peripheral edge of each heat exchange unit 10, the gap is easily recognized by outward appearance. This enables recognition of the assembly failure with reliability.

[0060]Moreover, according to the present embodiment, with regard to the insertion wall 12j, the distal end is located radially inward of the lower water passage hole 12e than the proximal end is. Therefore, in the state in which the insertion wall 12j is inserted in the upper water passage hole 11e, the distal end is located radially inward of the upper water passage hole 11e than the proximal end is. In stacking the upper and lower heat exchange plates 11, 12, the insertion wall 12j is easily guided into the upper water passage hole 11e. This configuration further suppresses reduction in assembly failure.

[0061]In the present embodiment, the insertion wall on the peripheral edge of the lower water passage hole is inserted in the upper water passage hole located opposite the lower water passage hole. Alternatively, an insertion wall provided on the peripheral edge of the upper water passage hole may be inserted in the lower water passage hole located opposite the upper water passage hole. In this case, with regard to the adjacent heat exchange units, the lower heat exchange unit corresponds to one heat exchange unit, and the upper heat exchange unit corresponds to another heat exchange unit. Further, with regard to the adjacent heat exchange units, the upper water passage hole corresponds to a first opening, and the lower water passage hole corresponds to a second opening.

Other Miscellaneous

[0062](1) In the above embodiment, the upper heat exchange plate includes the upper peripheral edge joint serving as an outer peripheral flange portion, and the lower heat exchange plate includes the lower peripheral edge joint serving as an outer peripheral flange portion. However, according to the present invention, as illustrated in FIG. 9, one of the upper heat exchange plate 11 and the lower heat exchange plate 12 may include an outer peripheral flange portion disposed upright on one side in the stacking direction of the heat exchange unit 10. In this case, as in the above embodiment, the insertion wall 12j has a distal end with a maximum protrusion height Hs larger than an overlapping margin Hp between the outer peripheral flange portion W1 of the upper heat exchange plate 11 corresponding to a first heat exchange plate and the peripheral edge of the lower heat exchange plate 12 corresponding to a second heat exchange plate (i.e., the peripheral edge of the lower heat exchange plate 12 of the upper heat exchange unit 10 located on one side in the stacking direction of the heat exchange units 10, the lower heat exchange plate 12 being adjacent to the upper heat exchange plate 11 of the lower heat exchange unit 10). Further, according to the present invention, although not illustrated, even in a case where the insertion wall is provided downward on the peripheral edge of the lower water passage hole, only the lower heat exchange plate may include the lower peripheral edge joint as an outer peripheral flange portion such that the lower heat exchange plate of each heat exchange unit corresponds to the first heat exchange plate and the upper heat exchange plate of each heat exchange unit corresponds to the second heat exchange plate. In this case, the lower heat exchange plate of the upper heat exchange unit adjacent to each heat exchange unit (one side in the stacking direction of the heat exchange units) corresponds to a proximate heat exchange plate.

[0063](2) In the above embodiment, the heat exchanger has the plurality of blocks having different flow passage of the first fluid. Alternatively, according to the present invention, the heat exchanger may have one flow passage of the first fluid. In this case, the first fluid flows in the same direction in all heat exchange units.

[0064](3) In the above embodiment, the burner having the downward combustion surface is disposed above the heat exchanger. Alternatively, according to the present invention, a burner having an upward combustion surface maybe disposed below the heat exchanger. In this case, since a gas flow passage of the combustion exhaust gas is reversed, an uppermost heat exchange unit corresponds to a most downstream heat exchange unit and a lowermost heat exchange unit corresponds to a most upstream heat exchange unit. Further, the combustion exhaust gas may flow in a left-right direction in the plate-type heat exchanger.

[0065](4) In the above embodiment, the insertion wall extends from the opening edge of the first opening to the second opening. According to the present invention, the insertion wall may alternatively extend from a predetermined position located circumferentially outward of the opening edge of the first opening, toward the second opening as long as the insertion wall is insertable into the second opening.

[0066](5) In the above embodiment, the heat medium is used as the first fluid flowing in the internal space of the heat exchange unit and the combustion exhaust gas is used as the second fluid flowing outside the heat exchange unit. Alternatively, according to the present invention, combustion exhaust gas may be used as first fluid and heat medium may be used as second fluid.

[0067](6) In the above embodiment, the plurality of heat exchange units is stacked in the vertical direction. Alternatively, according to the present invention, a plurality of heat exchange units may be stacked in the left-right direction.

[0068](7) In the above embodiment, the water heater is used. Alternatively, according to the present invention, a heat source device such as a boiler may be used.

[0069]As described in detail, the present invention is summarized as follows.

[0070]According to the present invention, there is provided a plurality of heat exchange units stacked on top of each other, [0071] wherein each of the plurality of heat exchange units is configured to exchange heat between first fluid flowing through an internal space in the heat exchange unit and second fluid flowing outside the heat exchange unit, [0072] adjacent heat exchange units of the plurality of heat exchange units are stacked such that the internal space in one heat exchange unit of the adjacent heat exchange units and the internal space in another heat exchange unit of the adjacent heat exchange units communicate with each other through a first opening in the one heat exchange unit and a second opening in the other heat exchange unit, [0073] the one heat exchange unit of the adjacent heat exchange units includes an insertion wall disposed on a peripheral edge of the first opening and inserted in the second opening when the adjacent heat exchange units are stacked, and [0074] the insertion wall has a distal end with a circumferentially discontinuous protrusion height.

[0075]According to the plate-type heat exchanger above, the insertion wall which is inserted in the second opening is provided on the peripheral edge of the first opening. Therefore, in the state where the one heat exchange unit and the other heat exchange unit are stacked on top of each other, if misalignment of the first and second holes located opposite each other occurs, the insertion wall runs onto the peripheral edge of the second opening. In such a case, a gap between the adjacent heat exchange units becomes larger than that in the state in which the adjacent heat exchange units are properly stacked on top of each other. This facilitates recognition of the assembly failure.

[0076]On the other hand, the first opening communicates with the internal space in the one heat exchange unit, and the second opening communicates with the internal space in the other heat exchange unit. Further, the insertion wall is inserted in the second opening, and the insertion wall protrudes inward of the internal space in the other heat exchange unit. Therefore, when the first fluid passes through the internal space near the second hole, flow resistance of the first fluid increases due to the insertion wall, and there is a concern that heat efficiency is reduced.

[0077]However, according to the plate-type heat exchanger above, since the insertion wall has the distal end with the discontinuous protrusion height, the insertion wall has in its distal end the circumferential cutout of a certain width. With this configuration, even when the insertion wall protrudes inward of the internal space in the other heat exchange unit, the first fluid passes through the cutout with less decrease in a flow passage of the first fluid near the second opening. This configuration suppresses increase in flow resistance of the first fluid passing through the internal space and prevents the insertion wall from reducing the heat efficiency.

[0078]Preferably, in the plate-type heat exchanger above, [0079] each of the plurality of heat exchange units includes a set of a first heat exchange plate and a second heat exchange plate joined together, [0080] of the set of the first and second heat exchange plates of each heat exchange unit, at least the first heat exchange plate has on its peripheral edge an outer peripheral flange portion disposed upright on one side in a stacking direction of the heat exchange units, [0081] with regard to the adjacent heat exchange units, the first heat exchange plate of the one heat exchange unit and a proximate heat exchange plate corresponding to one of the set of the first and second heat exchange plates of the other heat exchange unit adjacent to the one heat exchange unit on the one side in the stacking direction, the proximate heat exchange plate being located near the first heat exchange plate of the one heat exchange unit, are stacked such that the outer peripheral flange portion of the first heat exchange plate of the one heat exchange unit and a peripheral edge of the proximate heat exchange plate of the other heat exchange unit adjacent to the one heat exchange unit on the one side in the stacking direction overlap each other in the stacking direction by a predetermined overlapping margin, and [0082] the distal end of the insertion wall has a maximum protrusion height larger than the overlapping margin.

[0083]According to the plate-type heat exchanger above, the maximum protrusion height of the distal end of the insertion wall is larger than the overlapping margin. Therefore, when the insertion wall runs onto the peripheral edge of the second opening due to the assembly error, the gap of a predetermined height is defined between the peripheral edges of the adjacent heat exchange units. This enables recognition of the assembly failure with reliability.

[0084]Preferably, in the plate-type heat exchanger above, [0085] the distal end of the insertion wall is located radially inward of the first opening than a proximal end is.

[0086]According to the plate-type heat exchanger above, in stacking the upper and lower heat exchange plates, the insertion wall is easily guided into the second opening. This configuration further suppresses reduction in assembly failure.

[0087]Preferably, in the plate-type heat exchanger above, [0088] when the adjacent heat exchange units are stacked, the other heat exchange unit of the adjacent heat exchange units has, at a peripheral edge of the second opening, a recess recessed toward the first opening of the one heat exchange unit of the adjacent heat exchange units.

[0089]According to the plate-type heat exchanger above, the other heat exchange unit of the adjacent heat exchange units has, at the peripheral edge of the second opening, the recess recessed toward the first opening of the one heat exchange unit of the adjacent heat exchange units. This configuration prevents the insertion wall from largely protruding inward of the internal space in the other heat exchange unit. This configuration thus further suppresses increase in flow resistance of the water.

[0090]The present application claims a priority based on a Japanese Patent Application No. 2020-168811 filed on Oct. 6, 2020, the content of which is hereby incorporated by reference in its entirely.

[0091]Although the present invention has been described in detail, the foregoing descriptions are merely exemplary at all aspects, and do not limit the present invention thereto. It should be understood that an enormous number of unillustrated modifications may be assumed without departing from the scope of the present invention.