JP2009180422A - Boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boiler (boiler comprising a group of square water pipes) capable of preventing steam from directly flowing into a steam outlet pipe from a water pipe throttle portion, reducing a risk of superheat of the water pipe and the like, and obtaining the steam of comparatively high dryness. <P>SOLUTION: In this boiler 1 comprising an upper header 24, a lower header 25, the group of square water pipes constituted by arranging the group of roughly-vertical water pipes tandem between the upper header 24 and the lower header 25, and a burner 10 disposed on a side face of the group of square water pipes, a baffle plate 100 is disposed on an upper position of the group of square water pipes, and the baffle plate 100 is provided with a plurality of hole portions 101 on a position bypassing the throttle portion 23a of each of the water pipes 23 constituting the group of square water pipes. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a boiler, and more particularly to a boiler having a square water tube group configured by cascading substantially vertical water tube groups between an upper header and a lower header.

  In a steam boiler, the dryness of the produced steam is very important, and various attempts have been made to obtain high-quality steam (steam having a high dryness). As one of the techniques for obtaining this high quality steam, a separator (gas-liquid separator) is known (see, for example, Patent Document 1).

  The separator attached to the steam boiler is a device for separating saturated water and saturated steam and increasing the dryness of the produced steam. As this separator, there are generally known a centrifugal type that gives a swirl flow to the vapor flow to separate the gas and liquid, and a collision type that takes out the vapor phase by colliding the vapor flow with an obstacle. ing. Centrifugal separators are known to be an axial flow type that provides a swirl flow to the steam flow with blades, and a cyclone type that utilizes the action of the cyclone by flowing the steam flow from the tangential direction. It has been.

  On the other hand, in recent years, from the viewpoint of space saving and the like, a rectangular can body (here, “square can body” means, for example, a can body composed of a plurality of parallel water tube rows (a group of square water tubes)). A can body that is housed in a rectangular housing or casing and is assembled so that the entire structure becomes extremely thin by assembling equipment such as a blower, a water supply pump, and a burner. .) Is actively used.

  The steam boiler configured using this square can body cannot take a large header height due to legal restrictions (in general, the header height is low), Saturated water easily flows into the steam outlet pipe provided in communication with the upper header.

  When saturated water flows into the steam outlet pipe, the dryness of the steam to be produced decreases. Therefore, a steam boiler configured using a rectangular can body is usually equipped with one of the separators described above. It is attached.

  However, even if a separator is attached, if the amount of saturated water flowing into the steam outlet pipe is large, the water level of the separator rises, so that the dryness may not be increased effectively.

  In such a case, as one means for increasing the dryness of the steam, there is a method of keeping the water level in the can of the rectangular can body low. If the water level in the can is kept low, the inflow of saturated water to the steam outlet pipe is reduced, and the dryness of the resulting steam can be increased.

  However, when the water level in the can is kept low, there is a risk of adverse effects (such as overheating of the water pipe) on the water pipes constituting the can body. That is, keeping the water level in the can low is an effective means for obtaining steam having a high degree of dryness, but on the other hand, it also takes risks such as overheating of the water pipe.

  Moreover, in such a rectangular can body, one of the main causes of a decrease in dryness is steam (steam containing saturated water) ejected at high speed from the constricted portion of each water pipe constituting the water pipe group. However, it is also possible to directly flow into the steam outlet pipe.

JP 2005-349318 A

  Therefore, the present invention has been made to solve the above-described problems of the prior art, and prevents direct inflow of steam from the water pipe constriction part to the steam outlet pipe and reduces the risk of water pipe overheating and the like. An object of the present invention is to provide a boiler (a boiler having a square water tube group) capable of obtaining steam having a relatively high dryness.

  The present invention has been made to solve the above-mentioned problems, and is configured by arranging an upper header, a lower header, and a substantially vertical water tube group between the upper header and the lower header. And a burner provided on a side surface of the square water tube group, wherein a baffle plate is provided above the square water tube group, and the baffle plate Is characterized in that a plurality of hole portions are provided at positions avoiding the throttle portions of the water tubes constituting the square water tube group.

  The present invention has been made in order to solve the above-mentioned problems. An upper header, a lower header, and a group of substantially vertical water tubes are arranged in a row between the upper header and the lower header. A square water tube group configured as above and a burner provided on a side surface of the square water tube group, wherein a steam take-out portion communicating with the upper header is provided, and the square water tube group A baffle plate is provided at an upper position, and a hole is provided in the baffle plate at a position avoiding the steam extraction portion.

  Further, in the boiler according to the present invention, it is preferable that the baffle plate has a predetermined inclination angle so as to guide the saturated water ejected from the water pipe having a high heat load to the water pipe having a low heat load.

  Moreover, in the boiler concerning this invention, it is preferable that the said baffle board is a structure which has the curved shape approximated to the inner surface shape of the said upper header.

  ADVANTAGE OF THE INVENTION According to this invention, while preventing the inflow of the direct steam with respect to a steam outlet pipe from a water pipe throttle part, reducing the risks, such as water pipe overheating, the boiler which can obtain steam with comparatively high dryness ( A boiler having a square water tube group can be obtained.

  Before describing the embodiments of the present invention, terms used in this specification will be described.

  In the present specification, when simply referred to as “gas”, the gas is a concept including at least one of a gas during a combustion reaction and a gas for which the combustion reaction has been completed, and may also be referred to as a combustion gas. In other words, the gas includes both the gas in the combustion reaction and the gas in which the combustion reaction is completed, the gas in the combustion reaction only, or the gas in which the combustion reaction is completed only. It is a concept that includes. Hereinafter, the same concept is used unless otherwise described.

  Further, the gas temperature means the temperature of the gas during the combustion reaction unless otherwise specified, and is synonymous with the combustion temperature or the combustion flame temperature. Further, the suppression of the gas temperature means that the maximum value of the gas (combustion flame) temperature is kept low. In general, the combustion reaction is extremely small in the above-mentioned “gas for which the combustion reaction has been completed”, but continues, so “completion of the combustion reaction” means 100% completion of the combustion reaction. It is not a thing.

  Hereinafter, embodiments of the present invention will be described.

  First, the boiler according to the first aspect of the present embodiment is configured by cascading a substantially vertical water tube group between an upper header, a lower header, and the upper header and the lower header. A boiler provided with a square water tube group and a burner provided on a side surface of the square water tube group, a baffle plate is provided above the square water tube group, and the baffle plate includes: A plurality of hole portions are provided at positions avoiding the throttle portions of the water tubes constituting the square water tube group.

  According to such a configuration, water in the square water tube group is heated by the burner to generate steam, and a steam outlet pipe (a steam outlet configured to communicate with the upper header to take out steam) When the steam is taken out through the pipe), the dryness of the steam taken out can be increased because the baffle plate is provided above the square water pipe group. More specifically, even if a mixed fluid of saturated water and saturated steam is ejected into the upper header by heating the water in the square water tube group, the baffle plate has the Since the plurality of hole portions are provided at positions avoiding the throttle portions of the water tubes constituting the square water tube group, the mixed fluid does not flow directly from the respective water tubes into the steam outlet tube. That is, according to such a configuration, the mixed fluid ejected from the water pipe restricting portion collides with the baffle plate before flowing into the steam outlet pipe, and a liquid phase component constituting the mixed fluid is removed at the time of the collision. Therefore, steam with high dryness is taken out from the steam outlet pipe through the baffle plate. At this time, since the liquid phase separated by the baffle plate returns to the water pipe side, the risk of water pipe overheating and the like can be reduced according to this configuration.

  Further, the boiler according to the second aspect of the present embodiment is configured by arranging an upper header, a lower header, and a substantially vertical water tube group between the upper header and the lower header. A boiler comprising a square water tube group and a burner provided on a side surface of the square water tube group, wherein a steam take-out portion communicating with the upper header is provided, at a position above the square water tube group Is provided with a baffle plate, and the baffle plate is provided with a hole at a position avoiding the steam extraction portion.

  According to such a configuration, when the water in the square water tube group is heated by the burner to generate steam, and the steam is taken out through the steam outlet pipe, the upper position of the square water tube group is Since the baffle plate is provided on the surface, the dryness of the steam taken out can be increased. More specifically, even if a mixed fluid of saturated water and saturated steam is ejected into the upper header by heating the water in the square water tube group, the baffle plate has the Since the hole is provided at a position avoiding the steam outlet, the mixed fluid does not flow directly from the respective water pipes into the steam outlet pipe. That is, according to such a configuration, since the hole is provided at a position avoiding the steam outlet pipe of the arranged baffle plate, the mixed fluid ejected from the water pipe throttling portion is the steam outlet. Collides with the baffle plate before flowing into the tube. And since the liquid phase component which comprises a mixed fluid will be removed at the time of this collision, the vapor | steam with high dryness will be taken out from the said vapor | steam outlet pipe via the said baffle plate.

  Furthermore, the boiler concerning the 3rd aspect of this embodiment is the structure of the 1st aspect or the 2nd aspect, and the said baffle plate guides the saturated water ejected from the water pipe with a high heat load to the water pipe with a low heat load. Therefore, it is preferable to have a predetermined inclination angle.

  According to this preferable configuration, the saturated water in the mixed fluid separated by the baffle plate is guided to a water pipe having a low heat load (for example, an outer water pipe that is not easily heated by the burner). In addition to the effect, water pipe overheating can be prevented more effectively.

  In the boiler according to the fourth aspect of the present embodiment, the baffle plate may have a curved shape that approximates the inner surface shape of the upper header in the configuration of any one of the first aspect to the third aspect. preferable.

  According to this preferred configuration, since the baffle plate has a curved shape that approximates the inner shape of the upper header, in addition to the various effects described above, the baffle plate is interposed between the steam outlet pipe and the baffle plate. An appropriate inflow passage (inflow area) when the steam flows into the steam outlet pipe can be ensured. In addition, since the inner shape of the upper header is usually an upward convex shape (for example, a convex shape having a convex shape on the upper side), the baffle plate having a curved shape approximating the inner surface shape is used. The saturated water in the mixed fluid separated by the baffle plate can be effectively guided to a water pipe having a low heat load (for example, an outer water pipe that is not easily heated by the burner), and water pipe overheating can be prevented.

  Next, examples of the present invention will be shown. However, the present invention is not limited by the above embodiment and the following examples, and should be implemented with appropriate modifications within a range that can be adapted to the purpose of the preceding and following descriptions. Of course, these are also possible and all fall within the technical scope of the present invention.

  Hereinafter, embodiments of a boiler according to the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory view of a longitudinal section of a steam boiler to which an embodiment of the present invention is applied. Moreover, FIG. 2 is explanatory drawing of the cross section which follows the II-II line | wire of FIG. 3 is a schematic diagram for explaining the baffle plate constituting the boiler shown in FIG. 1, and FIG. 3 (a) shows a state in which the baffle plate is placed at a position above the square water tube group. FIG. 3B is a schematic view showing the baffle plate. Here, in Fig.3 (a), about the water pipe group etc., it has shown with the virtual line (two-dot chain line).

  As shown in FIGS. 1 to 3, the boiler 1 according to the present embodiment has a planar premixed gas ejection surface (a flat combustion surface in which premixed gas ejection holes are formed in substantially the same plane. ) Having a fully premixed burner 10 (corresponding to the “burner” of the present invention) and a large number of heat absorbing water tubes (heat transfer tubes) 21, 22, 23 (“ A can body 20 having an "equivalent to a square water tube group", a blower 30 provided to send combustion air to the burner 10, and an exhaust gas in the can body 20 provided to discharge the exhaust gas from the boiler 1 to the outside. The chimney part 40 and the steam extraction part 80 provided in order to take out the vapor | steam produced | generated in each water pipe 21,22,23 which comprises the can 20 are comprised.

  The burner 10 constituting the boiler 1 according to this embodiment is a premixed gas burner having a premixed gas ejection surface in which premixed gas ejection holes are formed in substantially the same plane, and alternately includes corrugated plates and flat plates. It is configured by stacking. Based on such a configuration, a large number of premixed gas ejection holes are formed in the premixed gas ejection surface (combustion surface) 10 a of the burner 10. And this burner 10 is provided adjacent to the water pipe (water pipe group) which comprises the can 20 mentioned later. Although the detailed structure and the like are omitted here, the burner 10 according to the present embodiment has the same configuration as the “combustion burner” described in Japanese Patent No. 3221582, for example.

  Further, the can 20 constituting the boiler 1 according to this embodiment includes an upper header 24, a lower header 25, and a plurality of water pipes (which are erected between the upper and lower headers 24, 25). It is configured using a square water tube group composed of an outer water tube 21, an inner water tube 22, and a central water tube 23). In the can body 20, the outer water pipe 21, the inner water pipe 22, and the central water pipe 23 are arranged in the gas flow direction (longitudinal direction of the can body 20), and a central water pipe group (configured using the central water pipe 23). The inner water tube group (water tube group configured using the inner water tube 22) and the outer water tube group (water tube group configured using the outer water tube group 21) are formed in two rows. ing. Adjacent water tubes are arranged in a staggered manner. Furthermore, as shown in FIG. 2, in the can body 20 according to the present embodiment, using the outer water pipes 21 provided on both sides in the longitudinal direction and the connecting portions 26 that connect the outer water pipes 21, A pair of water pipe walls 27 are formed. In the can body 20, a substantially rectangular gas flow space 29 is formed by using the pair of water pipe walls 27 and the upper and lower headers 24, 25, and a predetermined interval is formed in the gas flow space 29. An inner water pipe 22 and a central water pipe 23 are disposed with a gap therebetween.

  Further, the blower 30 constituting the boiler 1 according to the present embodiment is provided for sending combustion air to the burner 10, and the blower 30 and the burner 10 include an air supply path portion 31. Is connected using. A gas fuel supply pipe 32 is provided in the air supply path section 31, and a fuel adjustment valve 33 that adjusts the fuel flow rate during high combustion and low combustion is provided in the gas fuel supply pipe 32. ing. In addition, in this air supply path part 31, it is also possible to provide a constriction part in order to improve the mixing property of fuel and air as needed.

  Moreover, the chimney part 40 which comprises the boiler 1 concerning a present Example is provided in the most downstream side of the can 20 so that the inlet may oppose the burner 10. As shown in FIG. Therefore, in the boiler 1 according to the present embodiment, the gas generated in the burner 10 is in linear contact with the water pipes 21, 22, and 23 that constitute the can body 20 (heat exchange is performed by contact). After), it is discharged out of the boiler 1 through the chimney 40 as exhaust gas.

  Further, in the boiler 1 according to the present embodiment, a steam outlet 80 is provided above the upper header 24, and the upper header 24 and the steam outlet 80 are connected to a steam outlet pipe (first steam outlet). The pipe 81 and the second steam outlet pipe 82) are connected to each other. A baffle plate 100 is provided above the square water tube group in the upper header 24. That is, in this embodiment, the baffle plate 100 is provided between the square water tube group in the upper header 24 and the steam outlet tubes 81 and 82.

  Further, the baffle plate 100 according to the present embodiment has a throttle part (outer water pipe throttle part 21a, inner water pipe throttle part 22a) of each water pipe (outer water pipe 21, inner water pipe 22, central water pipe 23) constituting the square water pipe group. , A plurality of holes (first hole 101, second hole 102) are provided at positions avoiding the central water pipe throttling part 23a). More specifically, as shown in FIGS. 3 (a) and 3 (b), the first hole 101 avoids the central water pipe throttling part 23a in the central part of the baffle plate 100 (each central water pipe throttling). The second hole portion 102 is provided in two rows across the first hole portion 101 so as to avoid the inner water pipe throttle portion 22a and the central water pipe throttle portion 23a. ing.

  The boiler 1 according to the present embodiment is configured as described above, and based on this configuration, the following combustion state is formed in the boiler 1.

  First, the gas fuel supplied from the gas fuel supply pipe 32 and the air supplied from the blower 30 are mixed in the air supply path 31, and the premixed gas mixed here is supplied to the burner 10. .

  The premixed gas ejected from the premixed gas ejection surface 10a of the burner 10 is ignited by ignition means (not shown), and a gas F undergoing a combustion reaction accompanied by a flame is formed in the burner 10. Since the premixed gas is ejected from the burner 10 so as to be substantially perpendicular (perpendicular to) the water pipes 21, 22, and 23 in the can body 20, the gas F in the combustion reaction is Contact is repeated so as to intersect with the water pipes 21, 22, and 23 in the can body 20 (after heat exchange with the water pipes) to become exhaust gas. And this exhaust gas is discharged | emitted outside the boiler 1 via the chimney part 40 provided in the most downstream side of the can 20.

  In the present embodiment, the first region 61 (see FIG. 2) provided between the central water tube group and the outer water tube group functions as a combustion reaction promoting region. That is, by providing the first region 61 which is a predetermined space, combustion can be promoted in the space, and CO in the gas can be actively oxidized. Furthermore, in the present embodiment, the second region 71 on the most downstream side of the can 20 can also function as a combustion reaction promoting region. Although not specifically shown here, for example, at least one of the first region 61 and the second region 71 may be provided with a CO oxidation catalyst material in order to further promote the combustion reaction.

  The water in each of the water pipes 21, 22, and 23 is heated and vaporized by heat exchange with the gas ejected from the burner 10. This steam is supplied to the steam use facility (not shown) through the upper header 24, the steam outlet pipes 81 and 82, and the steam outlet 80. If necessary, a separator may be provided inside the steam extraction unit 80 or on the downstream side of the steam extraction unit 80.

  In the boiler 1 according to the present embodiment, the combustion state as described above is formed inside, and the water in the water pipe group (square water pipe group) constituted by the water pipes 21, 22, and 23 is heated and steamed. Therefore, the following effects can be obtained.

  First, the boiler 1 according to the present embodiment has an angle formed by arranging an upper header 24, a lower header 25, and a substantially vertical water tube group between the upper header 24 and the lower header 25 in tandem. The boiler 1 includes a mold water tube group and a burner 10 provided on a side surface of the square water tube group, and a baffle plate 100 is provided above the square water tube group. In a position avoiding the throttle parts (outer water pipe throttle part 21a, inner water pipe throttle part 22a, central water pipe throttle part 23a) of each water pipe (outer water pipe 21, inner water pipe 22, central water pipe 23) constituting the square water pipe group, A plurality of holes (first hole 101, second hole 102) are provided.

  According to such a configuration, when the water in the square water tube group is heated by the burner 10 to generate steam, and the steam is taken out via the steam outlet pipes 81 and 82, the upper position of the square water tube group. Since the baffle plate 100 is provided, the dryness of the extracted steam can be increased. More specifically, even if a mixed fluid of saturated water and saturated steam is ejected into the upper header 24 by heating the water in the square water tube group, the baffle plate 100 has a square shape. Since the plurality of hole portions 101 and 102 are provided at positions avoiding the throttle portions 21a, 22a, and 23a of the water tubes 21, 22, and 23 that constitute the water tube group, the mixed fluid is supplied to each of the water tube throttle portions 21a. , 22a, 23a does not flow directly into the steam outlet pipes 81, 82. That is, according to such a configuration, the mixed fluid ejected from the water pipe restrictors 21a, 22a, and 23a collides with the baffle plate 100 before flowing into the steam outlet pipes 81 and 82, and the mixed fluid is discharged at the time of the collision. Since the constituent liquid phase is removed, steam having a high dryness is taken out from the steam outlet pipes 81 and 82 via the baffle plate 100.

  As described above, according to the present embodiment, by providing the baffle plate 100 shown in FIG. 1 and the like, the direct inflow of steam from the water pipe throttling parts 21a, 22a, 23a to the steam outlet pipes 81, 82. In addition, it is possible to obtain a boiler (a boiler having a square water tube group) capable of obtaining steam with a relatively high dryness while reducing the risk of water pipe overheating and the like.

  Note that the present invention is not limited to the above-described embodiments and examples, and can be implemented with various modifications as necessary within the scope that can meet the spirit of the present invention. Are included in the technical scope of the present invention.

  In the above embodiment, a case where a large number of holes are provided in one baffle plate has been described. However, the present invention is not limited to this configuration, and the throttle portions of the water tubes constituting the square water tube group are avoided. As long as a plurality of holes are provided at the position, any configuration may be used. Therefore, for example, a plurality of baffle plates are provided above the square water tube group, and a plurality of hole portions are provided in the baffle plates at positions avoiding the throttle portions of the water tubes constituting the square water tube group. It may be a configuration.

  Further, in the above-described embodiment, the case where the shape of the hole portion is circular has been described. However, the present invention is not limited to this configuration, and if necessary (for example, considering the influence of pressure loss or the like), the circular shape. It is good also as shapes (for example, ellipse etc.) other than.

  Furthermore, in the above-described embodiment, the case where the holes have the same (same diameter) circular shape has been described. However, the present invention is not limited to this configuration, and if necessary (for example, considering the influence of pressure loss or the like) And a plurality of circular shapes having different diameters. As a matter of course, even when the hole portion has a shape other than the circular shape, a plurality of hole portions having different sizes may be provided.

  Further, in the above embodiment, the case where the baffle plate has a flat plate shape has been described. However, the present invention is not limited to this configuration, and a plurality of the water pipes constituting the rectangular water tube group are disposed at positions avoiding the throttle portions. If the hole is provided, it may have a curved shape. For example, if the baffle plate has a chevron shape (bent shape) or a saddle shape with a vertex in the vicinity of the center of the steam outlet pipe (that is, a configuration having a predetermined inclination angle), the heat load is reduced. It becomes possible to guide the saturated water ejected from the high water pipe to the water pipe having a low heat load. According to such a configuration, the saturated water in the mixed fluid separated by the baffle plate is guided to a water pipe having a low heat load (for example, the outer water pipe 21 that is not easily heated by the burner 10). Can be prevented.

  Furthermore, in the baffle plate according to the above-described embodiment, the case where a plurality of holes are provided at positions avoiding the throttle portions of each water tube constituting the square water tube group has been described, but the present invention is limited to this configuration. Alternatively, the hole may be provided at any position of the baffle plate as long as direct flow of steam (mixed fluid) from the throttle portion of each water pipe to the steam extraction portion can be prevented. Therefore, for example, the baffle plate may have a configuration in which a hole is provided at a position avoiding the steam extraction portion. In addition, for example, the baffle plate may have a configuration in which holes are provided at positions where the water pipes constituting the square water pipe group are avoided from the throttle parts and positions where the steam extraction parts are avoided.

It is explanatory drawing of the longitudinal cross-section of the steam boiler to which one Example of this invention is applied. It is explanatory drawing of the cross section which follows the II-II line | wire of FIG. FIG. 3 is a schematic diagram for explaining a baffle plate constituting the boiler shown in FIG. 1, and FIG. 3 (a) is a schematic diagram showing a state in which the baffle plate is placed above the square water tube group, FIG. (B) is a top view of a baffle board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Boiler 10 ... Burner 10a ... Premixed gas ejection surface 20 ... Can body 21 ... Outer water pipe (water pipe)
21a ... Outer water pipe throttling part 22 ... Inner water pipe (water pipe)
22a ... Inner water pipe throttling part 23 ... Central water pipe (water pipe)
23a ... Central water pipe throttling part 24 ... Upper header 25 ... Lower header 26 ... Connection part 27 ... Water pipe wall 29 ... Gas flow space 30 ... Blower 31 ... Air supply path part 32 ... Gas fuel supply pipe 33 ... Fuel adjustment valve DESCRIPTION OF SYMBOLS 40 ... Chimney part 61 ... 1st area | region 71 ... 2nd area | region 80 ... Steam extraction part 81 ... 1st steam outlet pipe 82 ... 2nd steam outlet pipe 100 ... Baffle plate 101 ... 1st hole 102 ... 2nd hole

Claims (4)

An upper header, a lower header, a square water tube group configured by cascading substantially vertical water tube groups between the upper header and the lower header, and a side surface of the square water tube group; A boiler with a burner provided,
A baffle plate is provided above the square water tube group, and the baffle plate is provided with a plurality of holes at positions avoiding the throttle portions of the water tubes constituting the square water tube group. Boiler characterized by being. An upper header, a lower header, a square water tube group configured by cascading substantially vertical water tube groups between the upper header and the lower header, and a side surface of the square water tube group; A boiler with a burner provided,
A steam extraction portion communicating with the upper header is provided, a baffle plate is provided above the rectangular water tube group, and a hole is provided in the baffle plate at a position avoiding the steam extraction portion. The boiler characterized by being provided. The boiler according to claim 1 or 2, wherein the baffle plate has a predetermined inclination angle so as to guide saturated water ejected from a water pipe having a high heat load to a water pipe having a low heat load. The boiler according to any one of claims 1 to 3, wherein the baffle plate has a curved shape approximate to an inner surface shape of the upper header.

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