JP2005274023A - Water-tube boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water tube boiler with a canned body having reduced pressure loss and uniformed thermal load on water tubes while achieving high boiler efficiency. <P>SOLUTION: The water tube boiler comprises a first water tube row 4 in an annular shape consisting of the plurality of first water tubes 3, 3 and having gaps 5 formed in a predetermined range between the adjacent first water tubes 3, a combustion chamber 9 formed inside the first water tube row 4, a wall member 11 provided outside the first water tube row 4, and a gas flow path 13 formed by the first water tube row 4 and the wall member 11. The gaps extend in the radial direction of the first water tube row 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a can structure of a water tube boiler such as a once-through boiler, a natural circulation water tube boiler, or a forced circulation water tube boiler.

  In the can structure of the water tube boiler, a plurality of water tubes are annularly arranged to form an inner water tube row, a combustion chamber is formed inside the inner water tube row, and a plurality of water tubes are further provided outside the inner water tube row. Some water tubes are annularly arranged to form an outer water tube row, and a gas flow path is formed by both water tube rows. Radiation heat transfer is mainly performed in the combustion chamber, and convection heat transfer is mainly performed in the gas flow path.

  In the water pipe boiler, in order to improve boiler efficiency, measures are taken to increase the heat transfer area by providing heat transfer fins in each water pipe. Specifically, horizontal fin-shaped heat transfer fins are provided in multiple stages on the heat transfer surface on the gas flow path side in both the water tube rows to improve boiler efficiency (for example, Japanese Patent Publication No. 6-13921). (See U.S. Pat. No. 4,825,813)).

  As an advantage of this structure, there is an advantage that the heat transfer area is increased by the heat transfer fins to improve the boiler efficiency, and the boiler efficiency is less likely to be lowered due to a manufacturing error. However, on the other hand, there is a problem that the pressure loss is large, and it is necessary to use a large blower. In addition, the inflow of gas from the combustion chamber to the gas flow path is performed through an opening provided in the inner water pipe row. When there is only one opening, the area around the opening is There was the subject that the heat load of each water pipe became high.

Japanese Patent Publication No. 6-13921 (US Pat. No. 4,825,813)

  The problem to be solved by the present invention is to achieve a high boiler efficiency in the can of a water tube boiler while keeping the pressure loss low and making the heat load of the water tube uniform.

This invention was made in order to solve the said subject, and invention of Claim 1 is comprised by the some 1st water pipe, and a clearance gap is formed over the predetermined range between each said 1st water pipe adjacent. An annular first water tube row, a combustion chamber formed inside the first water tube row, a wall member provided outside the first water tube row, and the first water tube row and the wall member The gas channel is formed, and the gaps are formed to extend in the radial direction of the first water pipe row .

  Furthermore, the invention described in claim 2 is characterized in that the wall member is an annular second water pipe row constituted by a plurality of second water pipes.

According to this invention, with the configuration formed so as to extend the gap between the first water pipes in the radial direction of the first water pipe row, the heat transfer amount in each gap increases, and a sufficient heat transfer amount can be obtained. Since a plurality of the gaps are formed, the pressure loss is not so large, and both high boiler efficiency and low pressure loss can be achieved. That is, the pressure loss can be kept low while realizing high boiler efficiency. Further, since the gas flows into the gas flow path from the plurality of gaps, the heat transfer amount is distributed to the first water pipes, and the heat load of the first water pipes can be made uniform.

  Next, an embodiment of the present invention will be described. The present invention is implemented as a multi-tube water tube boiler, and is applied to a heat medium boiler that heats a heat medium in addition to a steam boiler and a hot water boiler.

  First, a first embodiment will be described with reference to FIGS. The first embodiment is an example in which the present invention is applied to a multitubular once-through boiler.

  The boiler body includes an upper header 1 and a lower header 2 arranged at a predetermined distance. Between these upper header 1 and lower header 2, a plurality of first water pipes 3, 3,. Each of these first water pipes 3 forms an annular first water pipe row 4, and the upper and lower ends of each of the first water pipes 3 are connected to the upper header 1 and the lower header 2, respectively. The first water pipe row 4 includes a gap holding portion 6 in which gaps 5, 5,... Are respectively formed between the adjacent first water pipes 3, and the first connection fins 7, 7, It is comprised by the water pipe wall part 8 connected and comprised by .... In the first embodiment, the gap holding portion 6 and the water pipe wall portion 8 are set to about ½ each.

  A combustion chamber 9 is formed inside the first water pipe row 4. A burner 10 is attached above the combustion chamber 9. The burner 10 is inserted from the inner central part of the upper header 1 toward the combustion chamber 9. The burner 10 is connected to a blower (not shown) for supplying combustion air.

  A cylindrical wall member 11 is provided outside the first water pipe row 4. The upper and lower ends of the wall member 11 are connected to the upper header 1 and the lower header 2, respectively. The wall member 11 includes an opening 12 in a part thereof. The opening 12 is provided at a position on the opposite side of the gap holding part 6 by about 180 degrees, that is, at a position facing the water pipe wall 8.

  The first water pipe row 4 and the wall member 11 form gas flow paths 13 and 13 extending from the gaps 5 to the opening 12. Both gas flow paths 13 communicate with the combustion chamber 9 via the gaps 5 and communicate with the flue 14 via the opening 12. Therefore, the gas from each gap 5 flows through both the gas flow paths 13, merges at the opening 12, and is discharged from the flue 14 to the outside.

  A heat insulating material 15 is provided outside the wall member 11, and a can cover 16 is provided outside the wall member 11.

  Now, the configurations of the gaps 5 and the gas passages 13 will be described more specifically. In the following description, the gas flow paths 13 are substantially symmetrical as flow paths from the gaps 5 to the openings 12, and therefore, one gas flow path 13 will be described.

First, each gap 5 will be specifically described. Among the first water pipes 3, in the first water pipe 3 constituting the gap holding part 6, the cross section is formed in a non-circular shape, and a pair of facing linear parts (reference numerals omitted) and a pair of facing parts. The first water pipes 3 are arranged so that the straight portions face each other. That is, each gap 5, the is formed so as to extend into the first radial water tube array 4, by the respective straight portions, the formed respectively over a predetermined distance in the direction of flow of the gas in the gap 5 Yes. Each of the extended gaps 5 serves to increase the gas flow rate, and is configured such that a section where the gas flow rate is high and the amount of heat transfer is large becomes long. In the first embodiment, the cross section of each first water pipe 3 has a shape similar to a corn, and each gap 5 is linear in the radial direction of the first water pipe row 4. Is formed.

  Further, the width of each gap 5 is set to be smaller toward the downstream side of the gas flow path 13 in the gas flow direction. This is because the gas gap tends to flow and the gas flow rate tends to increase because the gap 5 on the downstream side is closer to the opening 12, and the deviation of the gas flow rate in each gap 5 is suppressed. With this configuration, the gas flow rate in each gap 5 can be made substantially uniform, and the heat load of each first water pipe 3 in the gap holding portion 6 can be made almost uniform. In this first embodiment, the width of the gap 5 on the most upstream side is 6 mm, and the width is 4 mm, 4 mm, 4 mm, 3 mm, 3 mm, 3 mm, 2 mm, 2 mm, and 2 mm in order toward the downstream side.

  Next, the gas flow path 13 will be specifically described. The flow path cross-sectional area of the predetermined range in the gas flow path 13 (that is, the portion formed by the gap holding portion 6 and the wall member 11 in the gas flow path 13) is the downstream side in the gas flow direction. The structure is gradually increased toward. That is, the distance A (see FIG. 3) between the outer peripheral surface of each first water pipe 3 and the inner peripheral surface of the wall member 11 gradually increases toward the downstream side in the gas flow direction.

  In the gas flow path 13, the flow rate of the gas flowing through the gas flow path 13 increases due to the confluence of the gas from the gaps 5. In addition, the gas flow rate decreases due to heat transfer, and the gas flow rate decreases due to the gas volume reduction associated therewith. However, since the amount of increase in gas flow rate due to merging is larger, the gas flow rate generally increases. Therefore, by adopting a configuration in which the flow path cross-sectional area is gradually increased, the flow velocity of the gas flowing through the predetermined range in the gas flow path 13 can be made substantially constant, and a sufficient amount of heat transfer can be obtained. It is possible to maintain an appropriate gas flow rate in which the pressure loss is not so great.

  Here, the configuration in which the flow path cross-sectional area is gradually increased is realized, for example, by arranging the first water pipe row 4 and the wall member 11 so as to be eccentric from each other. That is, the first water pipe row 4 is eccentric to the side opposite to the opening 12 with respect to the wall member 11, or the wall member 11 is moved toward the opening 12 with respect to the first water pipe row 4. Make it eccentric. In the first embodiment, the latter eccentric structure is adopted.

  Furthermore, the heat transfer surface structure on the gas flow path 13 side in the first water pipe row 4 will be specifically described. In the first water pipe row 4, horizontal fin-shaped first heat transfer fins 18, 18,... Are provided in multiple stages on each of the first water pipes 3 in the gap holding part 6, and the water pipe wall 8 Are provided in multiple stages in each of the first water pipes 3 in the horizontal fin shape. Each of these heat transfer fins 18 and 19 protrudes from the peripheral surface of each of the first water pipes 3 toward the gas flow path 13 and is provided substantially horizontally, so that the amount of heat transfer is increased while increasing the amount of heat transfer. An increase in the distribution resistance can be suppressed. And according to the temperature of the gas which contacts, the protrusion height of each said 2nd heat transfer fin 19 is made higher than the protrusion height of each said 1st heat transfer fin 18. As shown in FIG. Thus, the first water pipe row 4 has a two-stage heat transfer surface structure.

  By the way, in this 1st embodiment, each said 1st water pipe 3 in the said clearance gap holding part 6 becomes a shape similar to the corn in the cross section, and each said 1st water pipe 3 in the said water pipe wall part 8 is said. Although the cross section of the single water pipe 3 has a circular shape, the cross section of all the first water pipes 3 may have a shape similar to corn depending on the implementation. Moreover, the said water pipe wall part 8 can also comprise each said 1st water pipe 3 closely, without providing each said 1st connection fin 7.

  Moreover, although the said clearance gap holding part 6 is provided in a predetermined range, in the central angle of said 1st water pipe row | line | column 4, it is provided over the range of 140 degree | times -320 degree | times, Preferably it is provided over the range of about 180 degree | times. The width of each gap is set in the range of 0.5 to 3 mm when the fuel is gas fuel, and 1.5 to 8 mm in consideration of prevention of clogging when the fuel is oil fuel. Is set in the range. And according to implementation, the width | variety of each said clearance gap 5 can also be set equally.

  The effect | action is demonstrated in the boiler of the above structure. When the burner 10 is operated, a combustion reaction is performed in the combustion chamber 9, and the gas generated by the combustion reaction (including the gas during the combustion reaction and the gas for which the combustion reaction has been completed) passes through the gaps 5. It flows into the gas flow path 13. The gas merged in the gas flow path 13 flows through the gas flow path 13 and is discharged to the outside as exhaust gas from the opening 12 through the flue 14. In the course of this flow, heat transfer from the gas to the fluid to be heated in each first water pipe 3 is performed, and in the combustion chamber 9, radiant heat transfer is mainly performed, and each gap 5 and each gas In the flow path 13, convective heat transfer is mainly performed. And the to-be-heated fluid in each said 1st water pipe 3 rises, being heated, and is taken out from the said upper header 1 as a vapor | steam.

In each of the gaps 5, the gas flow rate increases due to the action of the gaps 5 , and the section flowing in a state where the flow rate is increased is long. And since the said clearance gap 5 is formed in multiple places, pressure loss does not become so large. Further, in each of the gaps 5, the width of each of the gaps 5 is set to be smaller toward the downstream side, so that a predetermined amount of gas flows out of the gap 5 on the upstream side, The gas flow rate is uniform. Therefore, the heat load of each first water pipe 3 in the gap holding part 6 can be made uniform. If there is a bias in the heat load, the higher the heat load, the higher the heat load, the more the scale, which is a heat transfer inhibiting substance, will adhere to the inner surface of the first water pipe 3, but this problem will be solved by making the heat load uniform. Can be resolved. Furthermore, when the gas passes through the gaps 5, the gas in the combustion reaction comes into contact with the first water pipes 3 and is cooled to reduce the combustion temperature, so that generation of thermal NOx is suppressed and NOx is discharged. The amount is reduced.

  Further, the gas flow rate is substantially constant corresponding to the increase in the gas flow rate due to the merging of the gas from the gaps 5 by the configuration in which the cross-sectional area of the predetermined range in the gas flow channel 13 is gradually increased. Become. Therefore, a sufficient amount of heat transfer can be obtained in the predetermined range of the gas flow path 13, and an appropriate gas flow rate with which pressure loss does not become so large can be maintained.

  As described above, according to the above configuration, both high boiler efficiency (heat recovery rate) and low pressure loss can be achieved. Since high boiler efficiency can be realized, fuel consumption can be reduced and energy saving can be realized. Moreover, since a pressure loss can be reduced, a small thing can be used as the said air blower, and electric power consumption can be reduced significantly.

Next, modified examples of the first water pipes 3 will be described with reference to FIGS. In the first modification shown in FIG. 4, the cross section of each first water pipe 3 in which each gap 5 is formed has a substantially streamline shape, and the downstream end in the gas flow direction is adjacent to the first water pipe 3. The shape is bent along the peripheral surface of the single water pipe 3. That is, each said clearance gap 5 is formed in circular arc shape. According to this configuration, the channel length of each gap 5 can be set very long. Further, each gap 5 is formed so as to be inclined with respect to the radial direction of the first water pipe row 4 so as to face the downstream side in the gas flow direction in the gas flow path 13. The pressure loss when flowing into the gas flow path 13 from the gap 5 can be suppressed low. And after flowing in into the gas flow path 13 from each said clearance gap 5 , gas flows along the whole surrounding surface of each said 1st water pipe 3 of a downstream, and heat transfer amount increases.

Moreover, in the 2nd modification shown in FIG. 5, the cross section of each said 1st water pipe 3 in which each said clearance gap 5 was formed becomes an elliptical shape, The long axis is the said 1st water pipe row | line | column 4 It is arranged to face in the radial direction. That is, each gap 5 is formed in a diffuser shape. According to this configuration, the static pressure can be recovered on the downstream side of each gap 5 , and the effect of reducing pressure loss is obtained.

  Next, a second embodiment will be described with reference to FIGS. Similarly to the first embodiment, the second embodiment is an example in which the present invention is applied to a multitubular once-through boiler. Here, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the second embodiment, an annular second water tube row 20 is disposed as the wall member 11. That is, the second water pipe row 20 is disposed outside the first water pipe row 4 to form a double water pipe row structure. The first water pipe row 4 has the same configuration as that of the first embodiment, and the gap holding part 6 and the water pipe wall part 8 are set to about ½ each.

  The second water pipe row 20 is formed by arranging a plurality of second water pipes 21 in an annular shape. Each of the second water pipes 21 has a circular cross section and is connected by second connection fins 22, 22,. The upper and lower ends of each second water pipe 21 are connected to the upper header 1 and the lower header 2, respectively. Further, the second water pipe row 20 includes the opening 12 in a part thereof. The opening 12 is provided at a position on the opposite side of the gap holding portion 6 by about 180 degrees, that is, a position facing the water pipe wall 8. Moreover, each said 1st water pipe 3 and each said 2nd water pipe 21 are arrange | positioned in the state shifted by the half pitch at a circumferential direction.

  The first water pipe row 4 and the second water pipe row 20 form the gas flow paths 13 and 13 extending from the gaps 5 to the opening 12. Both the gas flow paths 13 communicate with the combustion chamber 9 via the gaps 5 and communicate with the flue 14 via the opening 12. Therefore, the gas from each gap 5 flows through both the gas flow paths 13, merges at the opening 12, and is discharged from the flue 14 to the outside.

  The heat insulating material 15 is provided outside the second water pipe row 20, and the can cover 16 is provided outside the heat insulating material 15.

  The specific configurations of the gaps 5 and the gas flow paths 13 are the same as those in the first embodiment, and are as follows. In the following description, the gas flow paths 13 are substantially symmetrical as flow paths from the gaps 5 to the openings 12, and therefore, one gas flow path 13 will be described.

First, each gap 5 will be specifically described. As in the first embodiment, the cross section of each first water pipe 3 in which each gap 5 is formed has a shape similar to a corn, and each gap 5 is formed in the first water pipe. It is formed linearly in the radial direction of the row 4. Here, each said 1st water pipe 3 can also be made into the shape of the modification shown in FIG. 4 or FIG.

  Further, the width of each gap 5 is set to be smaller toward the downstream side of the gas flow path 13 in the gas flow direction. This is because the gas gap tends to flow and the gas flow rate tends to increase because the gap 5 on the downstream side is closer to the opening 12, and the deviation of the gas flow rate in each gap 5 is suppressed. With this configuration, the gas flow rate in each gap 5 can be made substantially uniform, and the heat load of each first water pipe 3 in the gap holding portion 6 can be made almost uniform. Also in the second embodiment, the width of the gap 5 on the most upstream side is 6 mm, and the width is 4 mm, 4 mm, 4 mm, 3 mm, 3 mm, 3 mm, 2 mm, 2 mm, and 2 mm in order toward the downstream side.

  Next, the gas flow path 13 will be specifically described. In the gas flow path 13, the flow path cross-sectional area of the predetermined range is gradually increased toward the downstream side in the gas flow direction. That is, a distance B between the outer peripheral surface of each first water pipe 3 and the inner side of the second water pipe row 20 (arc line X (indicated by a two-dot chain line) in contact with the outer peripheral surface of each second water pipe 21) (see FIG. 8). ) Gradually increase toward the downstream side in the gas flow direction.

  In the gas flow path 13, the flow rate of the gas flowing through the gas flow path 13 increases due to the confluence of the gas from the gaps 5. In addition, the gas flow rate decreases due to heat transfer, and the gas flow rate decreases due to the gas volume reduction associated therewith. However, since the amount of increase in gas flow rate due to merging is larger, the gas flow rate generally increases. Therefore, by adopting a configuration in which the flow path cross-sectional area is gradually increased, the flow velocity of the gas flowing through the predetermined range in the gas flow path 13 can be made substantially constant, and a sufficient amount of heat transfer can be obtained. It is possible to maintain an appropriate gas flow rate in which the pressure loss is not so great.

  Here, the configuration in which the flow path cross-sectional area is gradually increased is realized, for example, by arranging both the water pipe rows 4 and 20 eccentrically with respect to each other. That is, the first water pipe row 4 is eccentric to the side opposite to the opening 12 with respect to the second water pipe row 20, or the second water pipe row 20 is opened with respect to the first water pipe row 4. Eccentric toward the part 12 side. In the second embodiment, the latter eccentric structure is adopted.

  Further, the heat transfer surface structure on the gas flow path 13 side in both the water pipe rows 4 and 20 will be specifically described. In the first water pipe row 4, as in the first embodiment, each first heat transfer fin 18 having a horizontal fin shape is provided in multiple stages on each first water pipe 3 in the gap holding portion 6. Each of the first water pipes 3 in the water pipe wall portion 8 is provided with the second fins 19 having a horizontal fin shape in multiple stages. The heat transfer fins 18 and 19 protrude from the peripheral surface of the first water pipes 3 toward the gas flow path 13 and are provided substantially horizontally, so that the amount of heat transfer is increased while increasing the heat transfer amount. An increase in distribution resistance can be suppressed. And according to the temperature of the gas which contacts, the protrusion height of each said 2nd heat transfer fin 19 is made higher than the protrusion height of each said 1st heat transfer fin 18. As shown in FIG. Thus, the first water pipe row 4 has a two-stage heat transfer surface structure.

  Moreover, in the said 2nd water pipe row | line | column 20, the heat-transfer surface which consists of the said 2nd water pipe 21 which is not equipped with the heat-transfer fin in order from the upstream, the horizontal fin-shaped 3rd heat-transfer fin 23,23, ... is multistage. Are provided with a heat transfer surface comprising the second water pipe 21 provided in a multi-stage, and a heat transfer surface comprising the second water pipe 21 provided with multi-stage fourth fins 24, 24,. It has a three-stage heat transfer surface structure. Each of these heat transfer fins 23 and 24 protrudes from the peripheral surface of each of the second water pipes 21 toward the gas flow path 13 and is provided substantially horizontally, so that the amount of heat transfer is increased while increasing the amount of heat transfer. An increase in the distribution resistance can be suppressed. And according to the temperature of the gas which contacts, the protrusion height of each said 4th heat transfer fin 24 is made higher than the protrusion height of each said 3rd heat transfer fin 23. FIG.

  The effect | action is demonstrated in the boiler of the above structure. When the burner 10 is operated, a combustion reaction is performed in the combustion chamber 9, and the gas generated by the combustion reaction (including the gas during the combustion reaction and the gas for which the combustion reaction has been completed) passes through the gaps 5. It flows into the gas flow path 13. The gas merged in the gas flow path 13 flows through the gas flow path 13 and is discharged to the outside as exhaust gas from the opening 12 through the flue 14. In the course of this flow, heat is transferred from the gas to the fluid to be heated in each of the water pipes 3, 21. In the combustion chamber 9, radiant heat transfer is mainly performed, and each gap 5 and the gas are transferred. In the flow path 13, convective heat transfer is mainly performed. Then, the heated fluid in each of the water pipes 3 and 21 rises while being heated and is taken out from the upper header 1 as steam.

In each of the gaps 5, the gas flow rate increases, and the section that flows while the flow rate is increased is long, so the amount of heat transfer in each of the gaps 5 increases significantly. And since the said clearance gap 5 is formed in multiple places, pressure loss does not become so large. Further, in each of the gaps 5, the width of each of the gaps 5 is set to be smaller toward the downstream side, so that a predetermined amount of gas flows out of the gap 5 on the upstream side, The gas flow rate is uniform. Therefore, the heat load of each first water pipe 3 in the gap holding part 6 can be made uniform. If there is a bias in the heat load, the higher the heat load, the higher the heat load, the more the scale, which is a heat transfer inhibiting substance, will adhere to the inner surface of the first water pipe 3, but this problem will be solved by making the heat load uniform. Can be resolved. Further, when the gas passes through the gaps 5, the gas in the combustion reaction comes into contact with the first water pipes 3 and is cooled to reduce the combustion temperature, so that the generation of thermal NOx is suppressed and NOx is discharged. The amount is reduced.

  Further, the gas flow rate is substantially constant corresponding to the increase in the gas flow rate due to the merging of the gas from the gaps 5 by the configuration in which the cross-sectional area of the predetermined range in the gas flow channel 13 is gradually increased. Become. Therefore, a sufficient amount of heat transfer can be obtained in the predetermined range of the gas flow path 13, and an appropriate gas flow rate with which pressure loss does not become so large can be maintained. In this second embodiment, the gas flow rate in the gas flow path 13 is about 20 m / s, the pressure loss of the entire can body is about 300 mmAq, and the boiler efficiency is about 90%.

  As described above, according to the above configuration, both high boiler efficiency and low pressure loss can be achieved. Since high boiler efficiency can be realized, fuel consumption can be reduced and energy saving can be realized. In addition, the pressure loss is reduced by about 40% compared to the conventional one, and a small fan can be used as the blower, so that power consumption can be greatly reduced.

  In the above embodiments, the cans in which the gas from each gap 5 flows through the gas flow paths 13 have been described. This invention is disclosed in FIGS. 1 and 2 of US Pat. No. 4,257,358, for example. As described, the present invention can also be applied to a can body in which gas flows in one direction so as to make one round of the gas flow path 13.

It is a longitudinal cross-sectional explanatory drawing of 1st embodiment in this invention. It is transverse cross-sectional explanatory drawing which follows the II-II line | wire of FIG. FIG. 3 is an explanatory cross-sectional view showing an enlarged main part of FIG. 2. It is transverse cross-sectional explanatory drawing which shows the 1st modification of a 1st water pipe. It is transverse cross-sectional explanatory drawing which shows the 2nd modification of a 1st water pipe. It is a longitudinal cross-sectional explanatory drawing of 2nd embodiment in this invention. FIG. 7 is a cross sectional explanatory view taken along the line VII-VII in FIG. 6. It is a cross-sectional explanatory drawing which expands and shows the principal part of FIG.

Explanation of symbols

3 1st water pipe 4 1st water pipe row 5 gap 9 combustion chamber 11 wall member 13 gas flow path 20 2nd water pipe row 21 2nd water pipe

Claims (2)

  An annular first water pipe row 4 formed by a plurality of first water pipes 3, 3,... And having a gap 5 formed between the adjacent first water pipes 3 over a predetermined range, and the inner side of the first water pipe row 4 A combustion chamber 9 formed on the wall, a wall member 11 provided outside the first water pipe row 4, and a gas flow path 13 formed by the first water pipe row 4 and the wall member 11. A narrow pipe portion 17, 17,... For increasing the gas flow rate in each gap 5 is formed over a predetermined distance in the gas flow direction in each gap 5. The water pipe boiler according to claim 1, wherein the wall member (11) is an annular second water pipe row (20) constituted by a plurality of second water pipes (21, 21, ...).

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