JP3568300B2 - Water tube boiler - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a water tube boiler having a structure in which an upper header and a lower header are communicated with a number of inner water pipes and outer water pipes.
[0002]
[Prior art]
FIG. 4 is a longitudinal sectional view showing the structure of a conventional water pipe boiler of this type, and FIG. 5 is a transverse sectional view. As shown in the figure, an upper header (upper trunk) 1 and a lower header (lower trunk) 2 are communicated with a number of inner water pipes 3 and outer water pipes 4, and a combustion chamber 8 is formed in an inner water pipe wall. A combustion gas passage 5 is formed between the pipe wall and the outer water pipe wall. An opening 10 is provided in the inner water pipe wall to make the combustion chamber 8 communicate with the combustion gas passage 5, and an opening 11 is provided in the outer water pipe wall to make the combustion gas passage 5 communicate with the flue 12. Structure.
[0003]
In this conventional water pipe boiler, the combustion gas that has exited from the combustion chamber 8 through the opening 10 provided in the water pipe wall of the inner water pipe 3 was formed by the water pipe walls of the inner and outer water pipes 3 and 4. By flowing through the combustion gas passage 5, heat is exchanged with the inner water pipe 3 and the outer water pipe 4, and the gas flows toward the flue 12 while lowering the gas temperature.
[0004]
FIG. 6 is disclosed in Japanese Utility Model Laid-Open No. 3-128201, in which all the outer water tubes 4 are fin tubes in which fins are wound around the water tubes in a coil shape. To increase the evaporation amount, that is, to improve the efficiency.
[0005]
[Problems to be solved by the invention]
In the above-described conventional techniques, the following problems remain.
That is, in the boilers having the structures shown in FIGS. 4 and 5, the ratio of the surface area to the volume of the water pipe was small, and the heat transfer amount was insufficient and the efficiency was not good. In order to increase the heat transfer area for the purpose of increasing the heat output (evaporation amount), the number of inner and outer water pipes must be increased or the length of the water pipes must be increased. there were. Further, since the inner water pipe 3 receives uniform radiation from the flame (not shown) from the combustion chamber 8 side, the amount of evaporation is relatively uniform, but the amount of evaporation of the outer water pipe row 4 decreases as the temperature of the combustion gas drops. However, the amount of evaporation was uneven at each of the locations 5a, 5b, and 5c along the flow path, and the amount of evaporation in the low-temperature section 5c was particularly low, so that the heat of the gas could not be effectively used.
[0006]
Further, in the structure of FIG. 6, the high-temperature combustion gas that has passed through the opening 10 provided in the water pipe wall of the inner water pipe 3 passes between the fin tubes and remains at a high temperature to the casing and the heat insulating material. Because of the contact, the casing and the heat insulating material need to have a specification that can withstand high temperatures, which raises costs and raises the problem of durability such as burning of the fins due to high temperatures. Further, since the combustion gas flows on both sides of the fin tube, it is not possible to increase the flow velocity by narrowing the gas passage 5 and improve the heat transfer efficiency. Therefore, there is a disadvantage that the amount of evaporation does not increase in spite of the increase in the heat transfer area, and the efficiency cannot be increased in spite of the cost.
[0007]
The present invention has been made in view of the above points, and solves the above-mentioned problems. By arranging the heat transfer surfaces effectively, the evaporation amount of each water pipe is made uniform, the structure is simple, the cost is low, and the heat transfer efficiency is low. It is an object of the present invention to provide an excellent water tube boiler.
[0008]
[Means for Solving the Invention]
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the invention according to claim 1 forms a double annular water pipe wall by a number of inner water pipes and outer water pipes communicating an upper header and a lower header. A combustion chamber is formed inside the inner water pipe, a combustion gas passage is formed between the inner water pipe and the outer water pipe, and the opening of the inner water pipe wall allows the combustion chamber to communicate with the combustion gas passage. In the boiler having a structure in which the combustion gas passage and the flue are communicated with each other by the openings, a predetermined number of outer water tubes near the openings provided in the outer water tube wall are provided with circumferential fins, and the fins are provided. A water pipe comprising: a bar-shaped baffle having a triangular cross section provided between an outer water pipe and a casing provided outside the outer water pipe; and the baffle is arranged near an opening of the outer water pipe wall. It is a boiler.
[0009]
With the above configuration, the combustion gas burned in the combustion chamber reaches the combustion gas passage from the opening of the inner water pipe wall, and performs heat exchange between the inner water pipe and the outer water pipe water pipe wall, From the opening of the outer water pipe wall to the flue. Here, since the circumferential fins are provided only in a predetermined number of the outer water pipes near the opening provided in the outer water pipe wall, the gas flow rate required to obtain a sufficient heat transfer amount and the outer water pipe The balance of the heat transfer area can be set so that the overall heat transfer efficiency is highest. In addition, since the fins are formed in the water pipe near the opening where the gas temperature has decreased, the heat transfer in the low temperature region increases while maintaining the external dimensions, and the heat absorption in each water pipe is balanced, and the water level is increased. To prevent carryover and ensure stable operation.
[0010]
When calculating the fins attached to the water pipe as the heat transfer area, the fins may be 20% of the actual area on one side, so that the boiler efficiency can be improved with a small area increase. Further, in the vicinity where the water pipe having the circumferential fins is disposed, the portion where the combustion gas directly contacts the casing (heat insulating material) has a sufficiently low combustion gas temperature. You don't have to use anything.
[0011]
The invention according to claim 2 is the water pipe boiler according to claim 1, wherein the fins in the circumferential direction are spiral fins.
According to the third aspect of the present invention, the heat transfer area of the water tube having the circumferential fins is changed from the upstream to the downstream of the flow of the combustion gas by changing the pitch and / or the height of the circumferential fins of the outer water tube. The water pipe boiler according to claim 1 or 2, wherein the water pipe boiler is sequentially increased. As a result, the actual heat transfer area of the water tubes 13 having the circumferential fins 14 is set to be larger downstream of the flow of the combustion gas than upstream of the flow of the combustion gas. It is planned.
[0012]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 and 2 show the structure of a water tube boiler according to one embodiment of the present invention. FIG. 1 is a longitudinal sectional view, and FIG. 2 is a transverse sectional view. The upper header 1 and the lower header 2 are both formed in an annular shape, and are connected to the upper header 1 and the lower header 2 by a number of outer water tubes 4 as well as a number of inner water tubes 3.
[0013]
A large number of inner water pipes 3 are arranged in close contact with each other, and a combustion chamber 8 is formed inside by an annular water pipe wall. A burner (combustion device) is provided inside the upper header 1 toward the combustion chamber 8. 9 are provided. Further, the outer water pipes 4 are connected to each other by fins 15 at intervals, and are also formed as annular water pipe walls. A combustion gas passage 5 is formed between the water pipe wall of the inner water pipe 3 and the water pipe wall of the outer water pipe 4. An opening 10 is provided in the inner water pipe wall on the opposite side of the flue 12 so that the combustion chamber 8 and the combustion gas passage 5 formed in the inner water pipe wall communicate with each other. An opening 11 is provided on the side 12 to communicate the combustion gas passage 5 with the flue 12. A casing 6 is provided outside the water pipe wall of the outer water pipe 4, and a heat insulating material 7 is provided outside the casing 6.
[0014]
The inner water pipe 3 and the outer water pipe 4 are arranged so as to be shifted from each other by about a half pitch in the circumferential direction. The number (five in the figure) of the water tube walls of the outer water tube 4 near the opening 11 is a water tube 13 having fins 14 in the circumferential direction. A rod-shaped baffle 17 having a triangular cross section may be provided between the water pipe 13 having the fins 14 and the casing 6 so as to change the flow of the combustion gas.
[0015]
Next, the operation of the water tube boiler having the above structure will be described. The combustion gas combusted in the combustion chamber 8 branches off at an opening 10 provided in the water pipe wall of the inner water pipe 3 and reaches the combustion gas passage 5, where the combustion gas and the water pipe walls of the inner water pipe 3 and the outer water pipe 4 communicate with each other. Heat is exchanged between the two, and they merge at the opening 11 provided in the water pipe wall of the outer water pipe 4 and go to the flue 12. In this case, since the outer water pipe near the opening 11 provided on the water pipe wall of the outer water pipe 4 is the water pipe 13 having the circumferential fins 14, the heat transfer area of the circumferential fins 14 is effectively used. Can increase the amount of heat transfer. Further, when the baffle 17 is provided between the water pipe 13 and the casing 6, the flow of the combustion gas is changed to prevent the stagnation, so that the heat transfer amount is further increased.
[0016]
As described above, in the combustion gas passage 5, heat exchange is performed between the water pipe walls of the inner and outer water pipes 3 and 4. The temperature is lower than the vicinity of the opening 10 provided in the wall, and the heat insulating material 7 may be set to a lower gas temperature specification, so that the cost of the heat insulating material 7 can be reduced.
[0017]
FIG. 3 is a cross-sectional view showing the structure of a water tube boiler according to another embodiment of the present invention. The difference between the water tube boiler of FIG. 3 and the water tube boiler of FIG. 2 is that, in FIG. 2, the rows of the inner water tubes 3 are arranged such that adjacent water tubes are arranged close to each other, whereas in FIG. The row of water pipes 3 is similar to the row of outer water pipes 4 in that the water pipes are connected to each other by fins 16, and the other points are the same.
[0018]
In the embodiment shown in FIGS. 2 and 3, the fins 14 in the circumferential direction are formed in a disk shape separated from each other, but may be formed in a spiral fin having high production efficiency. Further, in the above embodiment, the pitch (interval) and height of the fins are fixed, but the fins are changed appropriately to gradually increase the heat transfer area of the water pipe from upstream to downstream of the flow of the combustion gas. You may make it do. Thereby, the heat transfer amount of each water pipe can be more finely balanced, and the heat transfer efficiency as a whole can be improved.
[0019]
【The invention's effect】
As described above, according to the present invention, since the circumferential fins are provided only in a predetermined number of outer water tubes near the opening provided in the outer water tube wall, it is necessary to obtain a sufficient heat transfer amount. By setting the balance between the gas flow rate and the heat transfer area of the outer water pipe so that the overall heat transfer efficiency is the highest, the boiler can be used without changing the structure of the conventional can body or increasing the dimensions. Efficiency can be improved, and the amount of heat absorbed in each water pipe and the water level are balanced to prevent carryover in which a part of the can water is mixed with the steam and discharged, thereby ensuring stable operation.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a structure of a water tube boiler according to one embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a structure of a water tube boiler according to one embodiment of the present invention.
FIG. 3 is a cross-sectional view illustrating a structure of a water tube boiler according to another embodiment of the present invention.
FIG. 4 is a longitudinal sectional view showing the structure of a conventional water pipe boiler of this type.
FIG. 5 is a cross-sectional view showing the structure of a conventional water pipe boiler of this type.
FIG. 6 is a cross-sectional view showing the structure of another conventional multi-tube once-through boiler.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Upper header 2 Lower header 3 Inner water pipe 4 Outer water pipe 5, 5a-5c Combustion gas passage 6 Casing 7 Insulation material 8 Combustion chamber 9 Combustion device 10 Opening 11 Opening 12 Flue 13 Water pipe with fins in the circumferential direction 14 circumferential fins 15 fins 16 fins 17 baffles 18 coiled fins

Claims (3)

A number of inner and outer water pipes communicating the upper header and the lower header constitute a double annular water pipe wall, a combustion chamber inside the inner water pipe, and a combustion gas passage between the inner water pipe and the outer water pipe. Forming
In a boiler having a structure in which the combustion chamber and the combustion gas passage are communicated with each other through the opening of the inner water pipe wall, and the combustion gas passage and the flue are communicated with each other through the opening of the outer water pipe wall,
Circumferential fins are provided in a predetermined number of outer water pipes near an opening provided in the outer water pipe wall, and a cross section is formed between the outer water pipe having the fins and a casing provided outside the outer water pipe. Wherein the baffle is disposed near an opening of the outer water pipe wall . 2. The water tube boiler according to claim 1, wherein the circumferential fins are spiral fins. The pitch and / or height of the circumferential fins of the outer water pipe are changed to gradually increase the heat transfer area of the water pipe having the circumferential fins from upstream to downstream of the flow of the combustion gas. The water tube boiler according to claim 1.

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