PLATE-TYPE HEAT EXCHANGER

FIELD OF THE INVENTION

The present invention relates to a plate-type heat exchanger formed by stacking a plurality of heat exchange units, each of which being configured to exchange heat between a first fluid flowing inside the heat exchange unit and a second fluid flowing outside the heat exchange unit.

DESCRIPTION OF THE RELATED ART

Conventionally, a plate-type heat exchanger having a plurality of heat exchange units in which an upper heat exchange plate and a lower heat exchange plate are joined has been proposed (for example, Patent Prior Art 1: KR 10-1608149 A). Each of the heat exchange units has an internal space through which a heat medium as a first fluid flows between the upper heat exchange plate and the lower heat exchange plate, and a plurality of through holes penetrating the internal space in a non-communicating state and through which combustion exhaust gas as a second fluid passes in a vertical direction.

The plate-type heat exchanger includes a plurality of blocks stacked on top of each other and each of the blocks includes at least one heat exchange unit. Further, adjacent blocks in the vertical direction communicate with each other in such a manner that the heat medium flows therethrough. Further, the adjacent blocks are formed in such a manner that a heat medium flow passage in one block is different indirection to that in another block. According to this configuration, the heat medium flow passage in the heat exchanger becomes longer as the number of blocks increases, leading to improvement in heat efficiency.

In the heat exchange unit having the through hole penetrating the internal space in the non-communicating state as described above, a peripheral portion of the through hole through which the combustion exhaust gas passes is most heated. Therefore, in order to enhance thermal efficiency, a structure of the heat exchange unit in which as much heat of the combustion exhaust gas as possible is efficiently transferred to the heat medium near the peripheral portion of the through hole is preferable.

Further, in the plate-type heat exchanger formed by stacking the plurality of heat exchange units, adjacent heat exchange units are preferably disposed in such a manner that a projection plane of a through hole in one heat exchange unit does not overlap a through hole in another heat exchange unit as seen from a direction of a gas flow passage of the combustion exhaust gas. The gas flow passage of the combustion exhaust gas in the heat exchanger thus becomes long, leading to improvement in heat efficiency.

However, in the heat exchanger having the through hole arrangement structure described above, a through hole in an upstream-side heat exchange unit faces a projection plane where a through hole in a downstream-side heat exchange unit is not located. Therefore, when the combustion exhaust gas passes through the through hole in the upstream-side heat exchange unit, then the combustion exhaust gas collides with the projection plane on a surface of the downstream-side heat exchange unit. Thereafter, the combustion exhaust gas spreads over the surface of the downstream-side heat exchange unit, and then flows to a downstream side of the gas flow passage of the combustion exhaust gas through the through hole in the downstream-side heat exchange unit. Accordingly, in an upstream region of the gas flow passage of the combustion exhaust gas, high-temperature combustion exhaust gas concentratedly heats a small portion of the downstream-side heat exchange unit facing the through hole in the upstream-side heat exchange unit, that is, the projection plane in the downstream-side heat exchange unit, resulting in local heating. In particular, the high-temperature combustion exhaust gas which flows through a through hole in a most upstream heat exchange unit and does not exchange heat with the heat medium flowing inside the most upstream heat exchange unit collides with a downstream-side heat exchange unit adjacent to the most upstream heat exchange unit located on a most upstream side of the gas flow passage of the combustion exhaust gas. As a result, the local heating is likely to occur at the downstream-side heat exchange unit adjacent to the most upstream heat exchange unit.

SUMMARY OF THE INVENTION

The present invention has been made to solve the problem described above, and an object of the present invention is to improve heat efficiency and to prevent local heating at a heat exchange unit in an upstream region of a flow passage of a second fluid.

According to the present invention, there is provided a plate-type heat exchanger comprising a plurality of heat exchange units stacked on each other,

wherein each heat exchange unit is configured to exchange heat between a first fluid flowing inside the heat exchange unit and a second fluid flowing outside the heat exchange unit,

each heat exchange unit has a plurality of through holes allowing the second fluid to flow outside the heat exchange units in a direction intersecting a flow passage plane of the first fluid flowing inside the heat exchange units,

adjacent heat exchange units are disposed in such a manner that a projection plane of the through hole in one heat exchange unit does not overlap the through hole in another heat exchange unit as seen from a direction of a flow passage for the second fluid,

the plurality of heat exchange units includes: a height varying portion-equipped heat exchange unit (P) having, on the projection plane, a height varying portion varying a height of a flow passage for the first fluid; and a planar portion-equipped heat exchange unit (Q) having, on the projection plane, a planar portion making the height of the flow passage for the first fluid substantially constant, and

at least a second heat exchange unit that is adjacent to and located on a downstream side of a most upstream heat exchange unit located on a most upstream side of the flow passage for the second fluid, includes the planar portion-equipped heat exchange unit (Q).

Other objects, features and advantages of the present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic partial cut-away perspective view showing a heat source device having a heat exchanger according to an embodiment of the present invention;

FIG. 2 is a schematic partial exploded perspective view showing the heat exchanger according to the embodiment of the present invention;

FIG. 3 is a schematic diagram showing flows of a first fluid and a second fluid in the heat exchanger according to the embodiment of the present invention;

FIG. 4 is a schematic partial exploded perspective view showing the heat exchanger according to the embodiment of the present invention;

FIG. 5 is a schematic plan view showing one example of an upper surface of one heat exchange plate forming a height varying portion-equipped heat exchange unit (P) in the heat exchanger according to the embodiment of the present invention;

FIG. 6 is a schematic plan view showing one example of an upper surface of another heat exchange plate forming the height varying portion-equipped heat exchange unit (P) in the heat exchanger according to the embodiment of the present invention;

FIG. 7 is a schematic exploded perspective view showing a most upstream heat exchange unit and a second heat exchange unit in the heat exchanger according to the embodiment of the present invention;

FIG. 8 is a schematic plan view showing one example of an upper surface of one heat exchange plate forming a planar portion-equipped heat exchange unit (Q) in the heat exchanger according to the embodiment of the present invention;

FIG. 9 is a schematic plan view showing one example of an upper surface of another heat exchange plate forming the planar portion-equipped heat exchange unit (Q) in the heat exchanger according to the embodiment of the present invention; and

FIG. 10 is a schematic partial cross-sectional view showing the heat exchanger according to the embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

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.

As illustrated in FIG. 1, a heat source device according to the present embodiment is a water heater that heats water (first fluid) flowing into a heat exchanger 1 through an inlet pipe 20, with combustion exhaust gas (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.

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 the top. Additionally, a fan case 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.

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.

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

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.

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.

In other words, 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.

The combustion chamber 2 has a substantially oval shape in a plane 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.

As illustrated in FIG. 2, the heat exchanger 1 has a substantially oval shape in a plane 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.

As illustrated in FIGS. 2 to 4, 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 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” in order from the upstream side. 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 each other, and the most downstream block 5d is formed of six heat exchange units 10 stacked on 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 in such a manner that the water flows in the same direction. In each block 5, adjacent two of heat exchange units 10 communicate with each other in such a manner 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, 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 in such a manner 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.

Next, a configuration of the heat exchanger 1 will be described. As illustrated in FIGS. 2 to 9, the heat exchange units 10 respectively have a common configuration (e.g., a size, a shape). However, the heat exchange units 10 of the second downstream-side block 5c and most downstream block 5d are different in configuration (e.g., a shape of a through hole, presence or absence of a height varying portion) from the heat exchange units 10 of the most upstream block 5a and first downstream-side block 5b as will be described later. In the following, the heat exchange units 10 will be simply referred to a “heat exchange unit 10” as a generic term. The heat exchange units 10 which have height varying portions to be described later and constitute the second downstream-side block 5c and most downstream block 5d will be simply referred to a “heat exchange unit (P)” as a generic term. The heat exchange units 10 which have planar portions to be described later and constitute the most upstream block 5a and first downstream-side block 5b will be simply referred to a “heat exchange unit (Q)” as a generic term. Therefore, the configuration of the heat exchange unit (P) will be described first, and a description on the heat exchange unit (Q) will be mainly given of a difference from the configuration of the heat exchange unit (P). 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.

In the second downstream-side block 5c and most downstream block 5d, each heat exchange unit (P) is formed by superimposing a set of upper and lower heat exchange plates 11, 12 in the vertical direction and joining predetermined positions to be described later with brazing material or the like. The upper and lower heat exchange plates 11, 12 of each heat exchange unit (P) have a common configuration, except for part of configuration such as positions of upper and lower through holes, and presence or absence of water passage holes at corners. As illustrated in FIGS. 4 to 6, the upper and lower heat exchange plates 11, 12 of the heat exchange unit (P) respectively have a substantially oval shape in a plane view. The upper and lower heat exchange plates 11, 12 are made of stainless steel-based metal, for example. The upper and lower heat exchange plate 11, 12 respectively have a number of substantially circular upper and lower through holes 11a, 12a on substantially entire surface thereof except for the corners. The upper and lower heat exchange plates 11, 12 also have upper and lower through hole flange portions 11c, 12c at peripheral portions of the upper and lower through holes 11a, 12a. The upper and lower through holes 11a, 12a may have other shapes such as a substantially ellipse or rectangular shape, respectively.

On peripheral edges of the upper and lower heat exchange plates 11, 12, upper and lower peripheral edge joints W1, W2 projecting upward are respectively formed. The lower peripheral edge joint W2 of the lower heat exchange plate 12 is set in such a manner that when the lower peripheral edge joint W2 and a bottom 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 peripheral edge joint W1 of the upper heat exchange plate 11 is set in such a manner that when the upper peripheral edge joint W1 and a bottom surface peripheral edge of the lower heat exchange plate 12 of an upward adjacent heat exchange unit (P) are joined together, the upper heat exchange plate 11 of a lower heat exchange unit (P) and the lower heat exchange plate 12 of the upward adjacent upper heat exchange unit (P) are spaced from each other at a gap with a predetermined height.

Therefore, by joining the lower peripheral edge joint W2 of the lower heat exchange plate 12 and the bottom surface peripheral edge of the upper heat exchange plate 11, an internal space 14 having a predetermined height is formed (see FIG. 3). In addition, by joining a plurality of heat exchange units (P), an exhaust space 15 having a predetermined height is formed between vertically adjacent heat exchange units (P) (see FIG. 3).

The upper and lower through holes 11a, 12a are bored in a lattice pattern at predetermined intervals in the front-rear and left-right directions over substantially the entire surfaces of the upper and lower heat exchange plates 11, 12 of the heat exchange units (P) except for four corners. Further, the upper and lower through hole flange portions 11c, 12c respectively extend circumferentially outwardly and substantially horizontally from an open edge of the corresponding upper and lower through holes 11a, 12a, and have a substantially regular octagonal contour in a plane view. In the present embodiment, the upper and lower through holes 11a, 12a have the same size and shape. However, a pair of upper and lower through holes 11a, 12a may be different in size and shape from a different pair of upper and lower through holes 11a, 12a as long as one pair of the upper and lower through holes 11a, 12a opposed to each other in the vertical direction has the same size and shape.

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 superimposed with 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 in such a manner 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 superimposed with each other.

Therefore, when the upper and lower heat exchange plates 11, 12 are superimposed with 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. 10). 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.

Substantially circular upper and lower recesses 11b, 12b are respectively formed between four upper and lower through holes 11a, 12a adjacent to each other in the front-rear and left-right directions. Further, in peripheral regions of the upper and lower heat exchange plates 11, 12, substantially ellipse upper and lower recesses 11b, 12b are respectively formed between two upper and lower through holes 11a, 12a adjacent to each other in the front-rear or left-right direction. Further, upper and lower protrusions 11d, 12d are formed at substantially centers of the upper and lower recesses 11b, 12b, respectively. A diameter of each of the upper and lower protrusions 11d, 12d is smaller than that of the corresponding upper and lower recesses 11b, 12b. The upper and lower recesses 11b, 12b and the upper and lower protrusions 11d, 12d are respectively formed at positions corresponding to each other in the vertical direction when the upper and lower heat exchange plates 11, 12 are superimposed with each other. Therefore, the upper and lower recesses 11b, 12b and the upper and lower protrusions 11d, 12d are respectively formed in a lattice pattern at predetermined intervals in the front-rear and left-right directions over substantially the entire surfaces of the upper and lower heat exchange plates 11, 12 except for the four corners. Further, the intervals in the front-rear and left-right directions between adjacent upper and lower recesses 11b, 12b are respectively set to be substantially the same as those between adjacent upper and lower through holes 11a, 12a. Thus, the upper and lower through holes 11a, 12a and the upper and lower recesses 11b, 12b are alternately formed at substantially equal intervals in the front-rear and left-right directions. Further, the upper and lower recesses 11b, 12b are formed in such a manner that the upper and lower recesses 11b, 12b are located at substantially centers of regions surrounded by the four adjacent upper and lower through holes 11a, 12a in the front-rear and left-right directions except for the peripheral regions of the upper and lower heat exchange plates 11, 12. Further, each of the upper and lower recesses 11b, 12b has a diameter smaller than a minimum distance between the two adjacent upper and lower through hole flange portions 11c, 12c in the front-rear and left-right directions.

Each of the upper and lower recesses 11b, 12b is formed by drawing so as to project by a predetermined height inwardly of the internal space 14 when the upper and lower heat exchange plates 11, 12 are superimposed with each other. Each of the upper and lower recesses 11b, 12b is set to be a lower inwardly projecting height than each of the upper and lower through hole flange portions 11c, 12c. Each of the upper and lower protrusions 11d, 12d is formed by drawing so as to project by a predetermined height outwardly of the internal space 14 when the upper and lower heat exchange plates 11, 12 are superimposed with each other. Each of the upper and lower protrusions 11d, 12d is set to be a lower outwardly projecting height than the upper and lower peripheral edge joints W1, W2. Therefore, when the upper and lower heat exchange plates 11, 12 are superimposed with each other, a height varying portion 17 decreasing the height of the internal space 14 is formed by the corresponding upper and lower recesses 11b, 12b and an narrow internal space 14 having a predetermined height is defined between the upper and lower recesses 11b, 12b (see FIG. 10). Further, a height varying portion 18 increasing the height of the internal space 14 is formed by the corresponding upper and lower protrusions 11d, 12d formed at the substantially centers of the upper and lower recesses 11b, 12b and a wide internal space 14 having a predetermined height is defined between the upper and lower protrusions 11d, 12d (see FIG. 10). Although not illustrated, the water flow passage is formed between the height varying portion 17 and an adjacent flange portion 16. The upper and lower recesses 11b, 12b and the upper and lower protrusions 11d, 12d may have other shapes such as a substantially ellipse or rectangular shape, respectively. Further, only one of the height varying portions 17, 18 may be formed.

In the heat exchange unit (P), each of the upper and lower heat exchange plates 11, 12 has a water passage hole 63 in at least one corner. At a peripheral portion of the water passage hole 63, a water passage hole flange portion extends circumferentially outwardly and substantially horizontally from an open end of the water passage hole 63. The water passage hole 63 provided at at least one corner of the upper and lower heat exchange plates 11, 12 forming one heat exchange unit (P) is opened so as to communicate with the internal space 14 between the upper and lower heat exchange plates 11, 12 when the upper and lower heat exchange plates 11, 12 are superimposed with each other.

As illustrated in FIGS. 2, 3, 7, 8, and 9, the heat exchange unit (Q) has the same configuration as the heat exchange unit (P), except that upper and lower through holes 11a, 12a, upper and lower through hole flange portions 11c, 12c in and on the heat exchange unit (Q) are different in shape from those in and on the heat exchange unit (P), that neither a recess nor a protrusion is formed in regions surrounded with four upper and lower through holes 11a, 12a adjacent to each other in the front-rear and left-right directions, that no recess is formed between two upper and lower through holes 11a, 12a adjacent to each other in the front-rear or left-right direction in peripheral regions of the upper and lower heat exchange plates 11, 12, and that the upper heat exchange plate 11 of a most upstream heat exchange unit (Q) has no water passage hole. In the most upstream block 5a and first downstream-side block 5b, each heat exchange unit (Q) is formed by superimposing a set of upper and lower heat exchange plates 11, 12 in the vertical direction and joining predetermined positions to be described later with brazing material or the like. The upper and lower heat exchange plates 11, 12 of each heat exchange unit (Q) in the most upstream block 5a and first downstream-side block 5b have a common configuration, except for part of configuration such as positions of upper and lower through holes 11a, 12a, and presence or absence of water passage holes 63 at the corners. Therefore, by joining the upper and lower heat exchange plates 11, 12 of each heat exchange unit (Q), an internal space 14 having a predetermined height is formed (see FIG. 3). In addition, by joining a plurality of heat exchange units (Q), an exhaust space 15 having a predetermined height is formed between vertically adjacent heat exchange units (Q) (see FIG. 3). Further, by joining the heat exchange unit (P) and the heat exchange unit (Q), an exhaust space 15 having a predetermined height is formed between the heat exchange unit (P) and the heat exchange unit (Q) adjacent to each other in the vertical direction (see FIG. 3).

In the heat exchange unit (Q), the upper and lower heat exchange plates 11, 12 respectively have a number of substantially square upper and lower through holes 11a, 12a formed on substantially the entire surface thereof except for the corners and peripheral regions. The upper and lower heat exchange plates 11, 12 also have substantially square upper and lower through hole flange portions 11c, 12c formed at peripheral portions of the substantially square upper and lower through holes 11a, 12a. The upper and lower heat exchange plates 11, 12 respectively have a plurality of substantially pentagonal upper and lower through holes 11a, 12a in the peripheral regions thereof. The upper and lower heat exchange plates 11, 12 also have substantially pentagonal upper and lower through hole flange portions 11c, 12c formed on peripheral portions of the substantially pentagonal upper and lower through holes 11a, 12a. The upper and lower through holes 11a, 12a may have other shapes such as a substantially circular or ellipse shape, respectively. The upper and lower through holes 11a, 12a and the upper and lower through hole flange portions 11c, 12c are formed at substantially the same pitches as those of the heat exchange unit (P). Therefore, when the upper and lower heat exchange plates 11, 12 are joined together, substantially square through holes 13 and substantially square flange portions 16 closing the internal space 14 are formed at a region except for the peripheral region of the heat exchange unit (Q). Further, substantially pentagonal through holes 13 and substantially pentagonal flange portions 16 closing the internal space 14 are formed in the peripheral region of the heat exchange unit (Q). Unlike the heat exchange unit (P), the heat exchange unit (Q) has neither a recess nor a protrusion in a region surrounded with four through holes 13. Therefore, the heat exchange unit (Q) has a planar portion 19 making the height of the internal space 14 substantially constant and being located between the four through holes 13 adjacent to each other in the front-rear and left-right directions.

Each of the through holes 13 in the region except for the peripheral region of the heat exchange unit (Q) is disposed in such a manner that four vertexes are respectively directed to front, rear, left, and right sides of the peripheral edge of the heat exchange unit (Q), and one side of each through hole 13 extends in substantially parallel to one side of the through hole 13 diagonally adjacent thereto. Therefore, each through hole 13 is arranged in such a manner that the vertexes thereof protrude to the region surrounded with the four through holes 13 adjacent thereto, as seen from the direction of the gas flow passage of the combustion exhaust gas. Further, each flange portion 16 is formed in such a manner that each of the four vertexes (e.g., the right vertex) of the flange portion 16 is located closer to a center of the through hole 13 diagonally adjacent thereto than an opposite vertex (e.g., the left vertex) of the flange portion 16 diagonally adjacent thereto. In other word, each flange portion 16 is arranged so as to partially overlap the diagonally adjacent flange portions 16 as seen from the front-rear and left-right directions of the heat exchange unit (Q).

The water passage hole 63 provided at at least one corner of the upper and lower heat exchange plates 11, 12 forming one heat exchange unit (Q) is opened so as to communicate with the internal space 14 between the upper and lower heat exchange plates 11, 12 when the upper and lower heat exchange plates 11, 12 are superimposed with each other.

As illustrated in FIG. 3, the heat exchange units (P), (Q) are arranged in such a manner that, as to adjacent two of the 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 in such a manner that a projection plane of the through hole 13 in the one heat exchange unit 10 does not over lap the through hole 13 in the other heat exchange unit 10. Therefore, 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 downward 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. Further, each of the height varying portion 17 of the heat exchange unit (P), the height varying portion 18 of the heat exchange unit (P), and the planar portion 19 of the heat exchange unit (Q) is located on a projection plane 55 of the corresponding through hole 13 in the adjacent heat exchange unit 10 (see FIG. 10). The relationship between the through holes 13 in the heat exchange unit (P) and the through holes 13 in the heat exchange unit (Q) is similar to that described above (see FIGS. 3 and 10).

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 water passage holes 63 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, and predetermined at least one of the water passage holes 63 in the heat exchange unit 10 located on a most upstream side of the gas flow passage of the combustion exhaust gas forms the lead-out port 72. Note that in FIG. 3, the flange portions 16 around the through holes 13 and the recesses and the protrusions are omitted for simplicity of illustration.

In the heat exchange unit (P) 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”), the water passage hole 63 in a front right corner of the lower heat exchange plate 12 is connected to the inlet pipe 20. Also, a lead-out pipe 23 is inserted into the water passage hole 63 in a rear right corner of the lower heat exchange plate 12 in the most downstream heat exchange unit 10s. The lead-out pipe 23 extends upward from the most downstream heat exchange unit 10s to the heat exchange unit (Q) located on the most upstream side of the gas flow passage of the combustion exhaust gas (hereinafter, referred to as a “most upstream heat exchange unit 10a”). An upper end of the lead-out pipe 23 is connected to the water passage hole 63 in a rear right corner of the lower heat exchange plate 12 of the most upstream heat exchange unit 10a. An outer peripheral surface of the lead-out pipe 23 and an inner periphery of the water passage hole 63 in the rear right corner of the lower heat exchange plate 12 of the most downstream heat exchange unit 10s are joined together by a brazing material or the like. An upper end opening of the lead-out pipe 23 communicates with the internal space 14 in the most upstream heat exchange unit 10a. Further, when the lead-out pipe 23 is inserted from the most downstream heat exchange unit 10s to the most upstream heat exchange unit 10a, the lead-out pipe 23 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 lead-out pipe 23 passes through, in a non-communicating state, all the exhaust spaces 15 between the adjacent heat exchange units 10.

Accordingly, when the water flows into the internal space 14 in each heat exchange unit (P) of the most downstream block 5d through the water passage hole 63 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 (P) of the second downstream-side block 5c through each of the water passage holes 63 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 (P) 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 (Q) (hereinafter, referred to as a “second heat exchange unit 10b”) of the first downstream-side block 5b through the water passage hole 63 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 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 water passage holes 63 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 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 lead-out pipe 23 connected to the water passage hole 63 in the rear right corner of the most upstream heat exchange unit 10a. When the water flows into the lead-out pipe 23, then the water flows downward through the lead-out pipe 23, and flows out of the heat exchanger 1 through the outlet pipe 21 connected to the most downstream heat exchange unit 10s. 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 in such a manner 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 heat exchange units (P) of the most downstream block 5d are connected in parallel in such a manner 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.

With reference to FIG. 10, next, a description will be given of the flow of combustion exhaust gas in the upstream region of the gas flow passage of the combustion exhaust gas and the flow of water in the internal space 14 in each of the heat exchange units (P), (Q). Note that FIG. 10 is a partial cross-sectional view of the heat exchange units (P), (Q) taken along an inclined direction at a certain degree with respect to the front-rear and left-right directions so as to make the difference between the heat exchange units (P), (Q) clear.

The water flows between laterally distant water passage holes 63 in each of the heat exchange units (P), (Q). The heat exchange unit (P) has the height varying portions 17, 18 where the height of the water flow passage in the region surrounded with the through holes 13 increases and decreases. Therefore, when the water flowing from the upstream side of the internal space 14 passes the height varying portions 17, 18, the height varying portions 17, 18 increase flow resistance of the water to reduce a flow rate of the water. In addition, when the water passes the height varying portions 17, 18, the height varying portions 17, 18 cause turbulence of the water to narrow a temperature distribution of the water. Further, since the height varying portions 17, 18 increase a surface area of the heat exchange unit (P), the heat exchange unit (P) has a larger heat receiving area. According to this configuration, heat received from the combustion exhaust gas can be efficiently transferred to the water at the downstream side of the gas flow passage of the combustion exhaust gas. Furthermore, since the heat exchange units (P) excellent in heat transferability are stacked on the downstream side of the heat exchange unit (Q), the upstream-side heat exchange unit (Q) absorbs sensible heat of the high-temperature combustion exhaust gas, and the downstream-side heat exchange unit (P) absorbs latent heat of the combustion exhaust gas. This configuration can thus improve heat efficiency.

On the other hand, in the present embodiment, the combustion exhaust gas flows vertically through the through holes 13 in each heat exchange unit 10. In each heat exchange unit 10, therefore, the through holes 13 are bored to allow the combustion exhaust gas to flow outside the heat exchange unit 10 in a direction intersecting substantially perpendicularly to a flow passage plane of the water flowing inside the heat exchange unit 10. In addition, the through holes 13 are arranged in the front-rear and left-right directions at substantially regular spacings over substantially the entire surface of each heat exchange unit 10. Therefore, the combustion exhaust gas flowing from the upstream side of the gas flow passage of the combustion exhaust gas collides with the entire surface of the most upstream heat exchange unit 10a except for the through holes 13 to heat the most upstream heat exchange unit 10a. In other words, a portion of the most upstream heat exchange unit 10a except for the through holes 13 serves as a heat receiving plane. As described above, the adjacent heat exchange units 10 are disposed in such a manner that the projection plane of the through hole 13 in the one heat exchange unit 10 does not over lap the through hole 13 in the other heat exchange unit 10. Therefore, after the combustion exhaust gas flows through each through hole 13 in the most upstream heat exchange unit 10a, the combustion exhaust gas concentratedly collides with the corresponding projection plane 55 having a small area on the second heat exchange unit 10b. The combustion exhaust gas, which collides with the second heat exchange unit 10b, includes the high-temperature combustion exhaust gas which is not in contact with the most upstream heat exchange unit 10a (i.e., the combustion exhaust gas which does not exchange heat with the water flowing through the internal space 14 in the most upstream heat exchange unit 10a). For this reason, if the heat exchanger 1 only consists of the heat exchange unit (P) having the height varying portions 17, 18, local overheating is likely to occur at the second heat exchange unit 10b that is adjacent to and is located on the downstream side of the most upstream heat exchange unit 10a.

However, according to the present embodiment, the heat exchange unit (Q) having the planar portion 19 making the height of the water flow passage substantially constant is used as the second heat exchange unit 10b. The planar portion 19 is disposed on the region surrounded with the four through holes 13, that is, the projection plane 55 of the corresponding through hole 13 in the most upstream heat exchange unit 10a (see FIGS. 7 to 10). Therefore, the flow passage resistance of the water passing the projection plane 55 in the heat exchange unit (Q) is smaller than that of the water passing the projection plane 55 in the heat exchange unit (P), leading to increase in the flow rate of the water passing the projection plane 55 in the heat exchange unit (Q). In addition, since the planar portion 19 has no irregularities, the combustion exhaust gas colliding with the planar portion 19 uniformly spreads in all directions. This results in relief from heat concentration on the projection plane 55 where the combustion exhaust gas concentratedly collides. Thus, this configuration can prevent the local overheating at the second heat exchange unit 10b.

Further, since the highest-temperature combustion exhaust gas collides with the most upstream heat exchange unit 10a, the peripheral portion of each through hole 13 through which the combustion exhaust gas flows is most heated. Therefore, when the flow rate of the water is low, local overheating may occur at the most upstream heat exchange unit 10a. However, according to the present embodiment, the heat exchange unit (Q) is used as the most upstream heat exchange unit 10a. Therefore, the planar portion 19 is disposed on the region surrounded with the four through holes 13 in the most upstream heat exchange unit 10a, that is, the projection plane 55 of the corresponding through hole 13 in the second heat exchange unit 10b. Thus, this configuration can prevent the local overheating at the most upstream heat exchange unit 10a.

Further, according to the present embodiment, the most upstream heat exchange unit 10a and second heat exchange unit 10b in the upstream region of the gas flow passage of the combustion exhaust gas are connected in series in such a manner that the water flows through the second heat exchange unit 10b and the most upstream heat exchange unit 10a in this order. With this configuration, the whole of water, which has flowed through the second heat exchange unit 10b, flows into the most upstream heat exchange unit 10a. This configuration therefore can prevent the local overheating at the second heat exchange unit 10b and most upstream heat exchange unit 10a even when the amount of water to be supplied to the heat exchanger 1 is small.

Further, according to the present embodiment, the most upstream heat exchange unit 10a and second heat exchange unit 10b respectively have the substantially square through holes 13. Further, the respective vertexes of each substantially square through hole 13 protrude to the region surrounded with the substantially square through holes 13 adjacent thereto, that is, the projection plane 55 as seen from the direction of the gas flow passage of the combustion exhaust gas. This configuration can accelerate the velocity of the water passing the region surrounded with the substantially square through holes 13. Thus, this configuration can further prevent the local overheating.

Further, according to the present embodiment, the heat exchange unit (Q), that is, each of the most upstream heat exchange unit 10a and second heat exchange unit 10b has a protrusion protruding outward between adjacent two of the through holes 13 in the peripheral region of the heat exchange unit (Q). The projection planes 55 are also formed in the peripheral region; however, no through hole 13 is bored in a peripheral edge side of each projection plane 55. On the other hand, each of the projection planes 55 except for the projection planes 55 in the peripheral region of the heat exchange unit (Q) is surrounded with the four through holes 13. Therefore, the amount of heat received from combustion exhaust gas on each projection plane 55 surrounded with the four through holes 13 is larger than that on each projection plane 55 located on the peripheral region, so that local overheating is likely to occur. Therefore, by disposing the planar portions 19 at least on the projection planes 55 except for the projection planes 55 located on the peripheral region of the heat exchange unit (Q), the local overheating can be effectively prevented. Further, when the irregularities are disposed between adjacent two of the through holes 13 in the peripheral region of the heat exchange unit (Q), the heat of the combustion exhaust gas can be efficiently transferred to the water.

According to the present invention, not only heat efficiency can be improved but local heating at the heat exchange unit in the upstream region of the gas flow passage of the combustion exhaust gas can be prevented. Accordingly, the plate-type heat exchanger excellent in heat efficiency and durability can be provided.

OTHER EMBODIMENTS

(1) In the above embodiment, the downstream-side heat exchange units downstream of the second heat exchange unit only consist of the heat exchange unit (P) having the height varying portion. However, if local overheating occurs at one or more downstream-side heat exchange units downstream of the second heat exchange unit, the heat exchange unit (Q) may be used as part of the downstream-side heat exchange units instead of the heat exchange unit (P). Further, the heat exchange unit (P) may be used as the most upstream heat exchange unit instead of the heat exchange unit (Q).

(2) In the above embodiment, the burner having the downward combustion surface is disposed above the heat exchanger. However, a burner having an upward combustion surface may be disposed below the heat exchanger.

(3) In the above embodiment, the plurality of heat exchange units is stacked in the vertical direction. However, a plurality of heat exchange units may be stacked in the left-right direction.

(4) In the above embodiment, the water heater is used. However, a heat source device such as a boiler may be used.

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

According to the present invention, there is provided a plate-type heat exchanger comprising a plurality of heat exchange units stacked on each other,

wherein each heat exchange unit is configured to exchange heat between a first fluid flowing inside the heat exchange unit and a second fluid flowing outside the heat exchange unit,

According to the heat exchanger described above, the heat exchange unit (P) has the height varying portion where the height of the flow passage for the first fluid varies, and the height varying portion is located on the projection plane of a corresponding through hole in an adjacent heat exchange unit. Therefore, flow resistance of the first fluid increases at the height varying portion, which results in reducing a flow rate of the first fluid passing the projection plane. Further, since turbulence of the first fluid occurs when the first fluid passes the projection plane, a temperature distribution of the first fluid narrows. Further, since the height varying portion increases a surface area of the heat exchange unit (P), the heat exchange unit (P) has a larger heat receiving area. According to this configuration, heat received from the second fluid can be efficiently transferred to the first fluid.

On the other hand, in an upstream region of the second fluid, a high-temperature second fluid flowing through the through hole in the most upstream heat exchange unit concentratedly collides with a corresponding projection plane having a small area on the second heat exchange unit. As described above, when the projection plane has the height varying portion, the flow rate of the first fluid passing the projection plane is likely to decrease. For this reason, if the heat exchanger only consists of the heat exchange unit (P) having the height varying portion, local overheating is likely to occur at the projection plane in the second heat exchange unit which corresponds to the through hole in the most upstream heat exchange unit. However, according to the heat exchanger described above, the second heat exchange unit includes the heat exchange unit (Q) having the planar portion making the height of the water flow passage substantially constant, and the planar portion is disposed on the projection plane of the corresponding through hole in the adjacent heat exchange unit. Therefore, the flow passage resistance of the first fluid passing the projection plane in the heat exchange unit (Q) is smaller than that of the first fluid passing the projection plane in the heat exchange unit (P), leading to increase in the flow rate of the first fluid passing the projection plane in the heat exchange unit (Q). In addition, since the planar portion has no irregularities, the second fluid colliding with the planar portion uniformly spreads in all directions. This results in relief from heat concentration on the projection plane of the second heat exchange unit.

Preferably, in the heat exchanger described above,

the most upstream heat exchange unit includes the planar portion-equipped heat exchange unit (Q).

According to the heat exchanger described above, local overheating at the most upstream heat exchange unit where the high-temperature second fluid collides can be prevented.

Preferably, in the heat exchanger described above,

the planar portion is formed on the projection plane in a region except for a peripheral region of the planar portion-equipped heat exchange unit (Q).

As to adjacent two of heat exchange units, when the projection plane of the corresponding through hole in one heat exchange unit is disposed in the peripheral region of another heat exchange unit, no through hole is provided in a peripheral edge side of the projection plane. On the other hand, the projection plane in the region except for the peripheral region of the heat exchange unit is surrounded with the four through holes. Therefore, an amount of heat received from the second fluid on the projection plane surrounded with the four through holes is larger than that on the projection plane located on the peripheral region. As a result, in the upstream region of the second fluid, local overheating is likely to occur at the projection plane in the region except for the peripheral region. Therefore, by disposing the planar portion at least on the projection plane in the region except for the peripheral region of the heat exchange unit (Q), the local overheating can be effectively prevented.

Preferably, in the heat exchanger described above,

the second heat exchange unit and the most upstream heat exchange unit are connected in series in such a manner that the first fluid passes inside the second heat exchange unit and the most upstream heat exchange unit in this order.

According to the heat exchanger described above, the whole of water, which has flowed through the second heat exchange unit, flows into the most upstream heat exchange unit. This configuration therefore can prevent the local overheating at the second heat exchange unit and the most upstream heat exchange unit even when the amount of water to be supplied to the heat exchanger is small.

Preferably, in the heat exchanger described above,

the through hole of the planar portion-equipped heat exchange unit (Q) has a substantially rectangular shape, and

the through hole having the substantially rectangular shape is arranged in such a manner that at least one vertex protrudes to the projection plane.

According to the heat exchanger described above, the velocity of the first fluid passing the projection plane in the heat exchange unit (Q) can be accelerated. Thus, this configuration can further prevent the local overheating.

The present application claims a priority based on a Japanese Patent Application No. 2019-188709 filed on Oct. 15, 2019, the content of which is hereby incorporated by reference in its entirely.

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.

PLATE-TYPE HEAT EXCHANGER

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