JPS6039921B2 - Spiral water tube boiler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a combustion chamber formed by winding up a water pipe into a cylindrical shape with a predetermined diameter, and then winding up another cylindrical shape with a different diameter from the cylindrical shape for the combustion chamber. Relating to improvements in the convection heat transfer part of a screw-on water tube boiler, which comprises a convection heat transfer part composed of annular flow paths between cylinders arranged in the same circular shape and having different diameters. .

FIG. 1 shows a schematic diagram of a conventional screw-type water tube boiler.

The water pipe is composed of an inner cylinder 1 wound up in a spiral shape and an outer cylinder 2 arranged in the same D-circle shape.

The water pipes of each cylinder are fully or partially welded to the adjacent water pipes to maintain close contact with each other and prevent combustion gas from leaking between the water pipes. Instead of welding, the outer cylinder 2 may also be rolled up tightly onto an outer casing 3, with which gas sealing is provided. For example, the boiler water supply enters from the upper part of the outer cylinder 2, flows down while circulating the outer cylinder, and at the lower end of the connecting pipe 4.
to the inner cylinder. The boiler water flows up the inner cylinder 1 from the lower part and flows out from the uppermost machine to, for example, steam and moisture porcelain (not shown). The circulation power of canned water is ensured by the pressure of the attached pump. burner 5,
It is attached to the upper part of the inner cylinder 1.

The upper part of the inner cylinder 1 is gas-sealed by an upper refractory 6. The bottom of the outer cylinder 2 is gas-sealed by a bottom refractory 7. Fuel is combusted by the burner 5 using the inside of the inner cylinder 1 as a combustion chamber.

The generated combustion gas flows down inside the combustion chamber, flows upward through the annular flow 8 between the inner cylinder 1 and the outer cylinder 2, and collects at the gas header section 9 at the upper end, where it flows through the exhaust row 0 attached in a certain direction.
More will flow out. Such a screw-on water tube boiler allows the water tubes to be constructed relatively easily, and the entire boiler can be assembled into a compact form, so it is suitable for forced once-through boilers, forced circulation boilers, forced circulation hot soot boilers, etc. It has been put into practical use in many places, with a heat output of 100,000 kcal.
/ hour to 300 kcal/hour.

Heat absorption in this type of boiler can be roughly divided into heat absorption by radiant heat transfer from the combustion flame in the combustion chamber constituted by the inner cylinder 1, and heat absorption by high-temperature combustion gas in the annular flow path between the inner and outer cylinders 1 and 2. This is the sum of the heat absorption due to tactile heat transfer to the flowing wall surface. The radiated heat in the combustion chamber is determined mainly by the size of the combustion flame, the size of the combustion chamber, combustion competition conditions, etc.

In the boiler design method, the size of the combustion chamber is determined by the dimensions required for combustion. Therefore, the heat absorption in the combustion chamber, which is one element of heat absorption in the boiler, is almost uniquely determined by the burner mechanism used in the boiler, and cannot be arbitrarily determined by Yasuju Hishi. In the current normal combustion method, the combustion chamber is 1 and the combustion chamber is 500,000 to 100,000 per volume.
In many cases, the design has a combustion amount of 10,000 kcal/hour, and the amount of heat absorbed in the combustion chamber, that is, the amount of heat absorbed on the inner peripheral side of the inner cylinder in Figure 1 a, is 60% to 40% of the amount of heat absorbed in the entire boiler. %. The remaining required heat absorption of the boiler will be 40-60%.

These amounts of heat must be absorbed by so-called contact heat transfer into the water tube surfaces of the inner and outer cylinders 1, 2 that form a flow path while the combustion gases flow through the annular flow path 8 of FIG.
The amount of heat absorbed by this contact heat transfer is expressed by the equation '1}. △Q=A×K×△T ………'11 Here, Q: Amount of heat absorbed by contact heat transfer kcal
/hA: Contact heat transfer area K
: Heat transfer coefficient due to contact kcal′ h℃△
T: Logarithmic average temperature difference defined by the formula '2' ℃Here, Lamp 1: Gas temperature at the entrance of the annular flow path ℃2: Gas temperature at the exit of the annular flow path ℃tw: Temperature of the boiling water ℃ For a certain type of boiler, tW is determined by the operating conditions of the boiler, and t01 is determined mainly by the size of the combustion chamber.

A is a value that is almost determined by the size of the combustion chamber. K is a value that is almost determined by the flow velocity of the high temperature combustion gas flowing through the annular flow path 8, and the gap 6 of the annular flow path
If it is determined, it becomes a constant value. tG2 is a value that the designer would like to arbitrarily decide on the design efficiency target of POILA, but [1
}, ■If the dimensions of the boiler combustion chamber are determined by the formula,
It is decided uniquely.

In order to lower Niji 1 and increase boiler efficiency, it is necessary not only to always increase the contact heat transfer area A, but also to enlarge the combustion port chamber.
This forces the entire boiler to be unnecessarily large. For this reason, as shown in FIG. 2, it becomes necessary to employ an extra side heat transfer section to create a so-called three-bus boiler.

Even in this 3-pass boiler, when the gas temperature at the turning point from 2-pass to 3-pass reaches 400 to 45 psi, normal steel cannot be used for the shell, so there is a limit to the manufacturing capacity of this type of boiler. , it becomes impossible to manufacture large-capacity products. The present invention compensates for the above-mentioned drawbacks of the screw-on water tube boiler and enables efficient manufacture of large-capacity models.The structure, operation, and effects thereof will be described in detail below based on examples.

Figure 3 is a cross-section of the annular gas flow separation of the screw type water tube boiler in the gas flow direction, showing the gap 6 formed by the water tubes (diameters D, D2) constituting the outer and inner cylinders. Gas flows through the channel.

Since both ends of the gap are constituted by the outer surface of the tube, the gas flow sequentially flows through the large gap, creating appropriate turbulence. For this reason, convective heat transfer is somewhat better than smooth flow, but it does not reach a value as good as so-called extra-tube cross flow. FIG. 4 is an embodiment of the present invention for promoting heat transfer in the annular channel of a screw-on water tube spoiler.

Round rods with a diameter d are arranged on the surface of the cylinder at a certain angle 8 with respect to the combustion gas flow direction and at an interval pitch P. FIG. 4a is a sectional view taken along a plane parallel to the cylinder axis X--X, and FIG. 4b is a view of the inner cylinder viewed from Y-Y. The heat transfer promoting baffles are arranged along the outer surface of the cylinder made of water tubes, so they are actually machined into an elliptical shape. By arranging the baffles in the annular channel in this manner, the combustion gas flow changes flow angle by 8 along the baffle in one portion and flows across the baffle in another portion.

The former component of the flow increases the relative velocity of the gas to the wall of the water tube by (1/cos8), thereby increasing the heat transfer coefficient. Other flow components flow over the baffle, creating a vortex behind the baffle, thereby creating turbulence in the flow near the wall and increasing heat transfer.
The heat transfer coefficient of the heat transfer surface prepared as shown in FIG. 4 is significantly improved by these two fluid elements. FIG. 5 is an exploded view of the cylinder.

Figure a shows eight baffles for promoting heat transfer arranged at an angle a to the gas flow angle. Although such an arrangement has a sufficient effect, if the angle of the baffle is changed midway to form a' as shown in Figure b, the turbulence effect due to the baffle is even greater and heat transfer is further improved.
FIG. 6 is an example of a screw-type water tube boiler based on the basic idea of promoting heat transfer coefficient as described above.

The combustion gas produced by the burner 5 flows down the combustion chamber and upwards in the annular channel 8 between the inner cylinder 1 and the outer cylinder 2. At this time, heat transfer from the combustion gas flow to the water tube is significantly improved by the heat transfer promoting baffle 11 attached to the inner cylinder 1, and the heat retained in the combustion gas is sufficiently transferred to the boiler water. As an example of the effect of heat transfer promoting baffles,
A comparative example of a conventional boiler without a baffle and a boiler according to the invention having a baffle is described below. in this way,
By adding a heat transfer promoting baffle, the boiler exhaust gas temperature can be reduced by 11,000 degrees, and the boiler efficiency can be improved by 6%. The fuel consumption of a 500k9/H boiler is 37 so/day using A heavy oil, and the 6% efficiency improvement results in a fuel savings of 5,000 to 10,000 yen per year, which is a significant effect.

Further, other examples for boilers larger than the above example will be described below. This is the 3pass boiler shown in Figure 2.
This is a comparison between a case where a baffle is attached to the s section and a case where a baffle is not attached.

By using the heat transfer enhancing baffle of the present invention, boiler efficiency is increased by 6%, resulting in significant fuel savings.

Furthermore, in a normal boiler design, the temperature of the turning section from the main ass section to the 3 pass section reaches 500 qC, making it impossible to design a boiler structure using ordinary steel materials, and this type of boiler no longer works. In comparison, the design of the present invention has a capacity of 370 qo, so generally steel can be used, and the range of application of the screw-on water tube boiler can be expanded to include large boilers.

As described above, the effects of this invention are remarkable.

In the above explanation, an example has been described in which a baffle is attached to the outside of the inner cylinder, but the effects of the present invention are also exhibited when baffles are attached to the inside of the outer cylinder or both the inner and outer cylinders. . The same applies to the case where 3pass in FIG. 2 is marked with a full mark.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of a conventional screw-on water tube boiler, where a is a longitudinal section, b is a cross-section, Fig. 2 is a schematic diagram of a 3-pass screw-on water tube boiler, and Fig. 3 is an annular flow path. FIG. 4 is a conceptual diagram of an annular flow path having a baffle for promoting heat transfer according to the present invention, FIG. The figure shows a screw type water tube boiler according to the present invention. 1...Inner cylinder, 2...Outer cylinder, 3...
...Outer casing, 4...Connection pipe, 5.
...Burner, 6...Upper refractory, 7...
Bottom refractory, 8... Annular channel, 9... Gas header section, 10... Exhaust port, I1... Heat transfer promoting baffle. ZI Ugly Melon 1 (2 to 3)

Claims (1)

[Claims] 1 In a water tube boiler that winds up water tubes in a spiral shape to form a cylinder with a predetermined diameter, a convection heat transfer section consisting of an annular flow path between cylinders with different wound diameters is located in the direction of combustion gas flow. A screw-on water tube boiler characterized in that it is made of round or square rods arranged at an angle and has a buttful whose outer diameter or height is smaller than the width of the annular flow path.