JPS61225507A - Flame holding device for heat exchanging - Google Patents

Abstract

PURPOSE:To contrive to miniaturize a heat exchanging part and not to require a long and large burning chamber for preventing incomplete burning by a method wherein a porous object provided with many heat transfer passages communicating a liquid supply header with a liquid exhaust header is arranged via a narrow space over a heat transfer passage group provided between each heat transfer passage. CONSTITUTION:An object to be heated is transferred through a heat transfer passage 5 communicating a liquid supply header 3 with a liquid exhaust header 4. A premixed gas supplied from the lower side is passed toward the upper side through a small clearance 7 of a heat transfer passage group, introduced to a space between a heat transfer passage group A and a porous object B, then, ignited and burnt, a burning exhaust gas is exhausted by passing upward. The heated porous object supplies the heat to the heat transfer passage group, heats the object to be heated, and raises the object temperature. Meantime, the heat transfer passage group is cooled by a liquid to be heated transferred through the heat transfer passage, accordingly, the temperature rising of a premixed gas is restrained at lower level than an igniting temperature, thus, the generation of a backfire is obstructed. The porous object is heated at all time, therefore, the premixed gas is burnt perfectly, also the blow-off of a flame is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a flame stabilizing device for heat exchange in a water heater or the like that performs heat exchange using fuel.

[Conventional technology]

As shown in FIG. 6, in a conventional water heater, gas supplied from a fuel gas supply 20 is premixed with air in a combustion burner 21 and completely combusted in a combustion chamber 22, and this high-temperature combustion gas is mixed with the upper part. Water passing through the finned corrugated pipe 23 undergoes heat exchange to produce hot water or hot water.

In the figure, 24 indicates a water supply pipe, and 25 indicates a hot water outlet.

[Problem that the invention seeks to solve]

However, in such a conventional example, the combustion chamber 22 described above is an absolutely essential component in the water heater, and the combustion burner 21 and the finned flexible pipe 23 are connected to each other in order to prevent incomplete combustion. The spacing is at least 20
We need cm.

For this reason, conventional water heaters that include the combustion chamber 22 as an essential component have a problem in that they cannot be downsized.

[Means for solving problems]

This invention has a large number of heat transfer paths that communicate between a supply header and a discharge header for the liquid to be heated, and also has a small gap that allows the premixed gas supplied from below to pass upward. The structure includes a group of heat transfer paths provided between the heat transfer paths, and a porous object provided above the group of heat transfer paths with a narrow space interposed therebetween.

[Effect]

A heat transfer path communicates the liquid supply header and the liquid discharge header, and transports the heated liquid from the liquid supply header side to the liquid discharge header.

The small gaps in the heat transfer channels allow the premixed gas supplied from below to pass upwardly and guide this gas into the narrow space between the heat transfer channels and the porous body. The premixed gas that has reached this space is always ignited and burned in this space by ignition from a separately prepared ignition device or by the heat of the already combusted premixed gas, causing the porous object and the heat transfer path group to ignite and burn. heat up.

The porous body then allows the combustion exhaust gas to pass upward within the porous body and be discharged.

This heated porous object radiates heat to the group of heat transfer paths, supplies heat to the group of heat transfer paths, and together with the heat from the combustion described above, increases the heat transfer in the group of heat transfer paths. The liquid to be heated that is transported through the route is heated to raise its temperature.

On the other hand, this group of heat transfer paths is cooled by the heated liquid transported inside the heat transfer path, and the temperature of the premixed gas in the small gap of this group of heat transfer paths is prevented from rising to the ignition temperature. To prevent backfire from occurring regardless of the magnitude of the premixed gas delivery load.

Furthermore, since the porous object is constantly heated, it completely burns the premixed gas and prevents the flame from blowing out.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention shown in the drawings will be described in detail below.

In the figure, 1 is an introduction pipe for premixed gas, and this introduction pipe l
are opened at the center of the bottom plate of the case 2 and are connected to each other so as to communicate with the inside of the case 2, which has a rectangular parallelepiped shape and has an open top. Further, 3 is a water supply header, which is a side wall 2a of the case 2.
An adjacent side wall 2 is penetrated and introduced into the case 2 from a location near one side end and is connected to the negative side end of this side wall 2a.
b, and is attached closely along the inner wall surface of the side wall 2C facing the side wall 2a. Furthermore, this case 2
The tip of the water supply header 3 introduced into the tank is closed.

Reference numeral 4 denotes a drainage header, which is introduced into the case 2 from the side wall 2C and is attached closely along the inner wall surfaces of the side wall 2d and the side wall 2a. The section is also closed like the water supply header 3.

The water supply header 3 and the drainage header 4 arranged in the case 2 in this manner are communicated with each other through a large number of heat transfer thin tubes 5 arranged in parallel. As the heat transfer thin tube 5, a corrosion-resistant metal tube 1 such as stainless steel, titanium, Inconel, or copper tube is selected in order to prevent corrosion and to withstand pressure, and its outer diameter is 1 to 8 mm. Among them, diameters of 1 to 311 are preferred. In addition, these heat transfer thin tubes 5~
5, the interval between the outer surfaces is set to about 1 to 5 fins, and between each heat transfer thin tube 5, as shown in FIGS. 1 to 3, there are The thin wires 6 are arranged in a tatami-like manner.

This thin wire 6 is also preferably corrosion resistant.

Heat-resistant materials such as stainless steel, titanium, Inconel, copper, ceramic fiber, and glass fiber are used.

These heat transfer thin tubes 5 and thin wires 6 constitute a heat transfer path group A, and this heat transfer path group A has a small gap 7 through which the premixed gas supplied from below passes upward. , making up the boiler.

The premixed gas supplied into the case 2 through the introduction pipe 1 is guided to a gas header 10 below the heat transfer path group A.

Further, above the heat transfer path group A, ceramics are provided.

A porous object 8 such as a metal net is provided with a narrow space 9 interposed therebetween. Further, an ignition source (not shown) such as a piezoelectric element is provided at a predetermined portion of this space 9, and is used to start combustion of the premixed gas that has passed through the heat transfer path group A and risen.

In such a configuration, the water flowing through the water supply hender 3 flows along the periphery of the porous body 8, as shown in FIG. 1, and then flows through the heat transfer thin tubes 5 to 5. It reaches the drainage header 4 and, like the water supply header 3, is led out of the case 2 along the periphery of the porous body 8.

Further, the premixed gas supplied from the introduction pipe 1 to the gas header 10 in the case at a predetermined delivery load passes through the small gap 7 of the heat transfer path group A, reaches the space 9, and is ignited by the ignition source. Start combustion. This combustion exhaust gas passes through the porous body 8 and is discharged. Note that the combustion that occurs in this narrow space 9 is a combustion that spreads out in a plane, and the third
A flame 11 as shown in the figure is generated.

By such combustion, the heat transfer path group A is heated by radiant heat transfer and raises the temperature of the water passing through the heat transfer thin tubes S, thereby turning it into hot water or hot water.

Moreover, the porous object 8 is also heated by the combustion, and the heat transfer path group A is further heated by the heat radiation from the porous object 8.

The heated porous object 8 also heats the water supply header 3 and drainage header 4 provided along its periphery, so that indirect heating due to the above-described flame and heat radiation from the porous object 8 occurs. In addition, the temperature of water is increased additively, and a high heat exchange rate can be obtained.

In addition, although the water supply lid 3 is heated by the porous body 8 and raises the temperature of the water passing through the inside as described above,
Since water does not grow below 100° C., the premixed gas passing through the heat transfer path group A does not reach a very high temperature, especially the ignition temperature. In addition, each heat transfer thin tube 5
Since the interval S is narrow and the thin wires 6 are extended in a tatami-weave pattern, the small gap 7 is literally minute, increasing the contact area with the passing premixed gas and reliably suppressing the temperature rise. do. In this way, the heat transfer path group A maintains a so-called flame-out distance, prevents a flashback phenomenon in which upward combustion moves downward, and flame 11 is always maintained at a constant position as surface combustion. Therefore, even if the load on the burner is reduced and the amount of gas is reduced, no flashback phenomenon will occur.

Generally, when the load on the burner is increased, the flow velocity of the premixed gas increases, causing the flame to blow away or disappear. However, according to this embodiment, when the load is increased and the amount of premixed gas is increased, the increment Therefore, the porous object 8 made of ceramics or the like is also heated, and the amount of heat radiated increases. Then, this radiant heat heats the premixed gas immediately after passing through the heat transfer path group A, increasing the combustion speed, so that the flame always starts burning at a fixed position, and heat is transferred to the porous object 8. Planar surface combustion is maintained in the gap (space 9) to the group of paths, resulting in a flame holding effect.

Furthermore, according to such surface combustion, as shown in FIG. 3, the flame 11 is a uniform collection of short flames and burns with a spread in a plane. Because there are no heat transfer points and the heat transfer path group A is water-cooled by the supply water, the combustion temperature is lower than that in normal burner combustion.

Such a lower combustion temperature is a major factor in suppressing the production of nitrogen oxides, and is expected to result in cleaner exhaust gas than ever before.

In the inventors' implementation, the following conditions are selected.

○Conditions/Premixed gas-city gas (10,00Qkcal/h)
・Area of heat transfer path group A (thin tube boiler) - 120mm
120mm・Material of heat transfer capillary tube 5-Stainless steel outer diameter-2×Spacing between each heat transfer capillary tube 5-4wm・Thin wire 6-Stainless steel wire diameter dimension-0.5mm・Outer diameter of water supply header 3 and drainage header 4- 20mm Inner diameter - 9mm Porous object 8 - Ceramic with porosity 80% and thickness 10mm As a result of conducting under the above conditions, water with a water supply temperature of 18°C was
/mid, the recovered hot water (34℃)
was gotten.

In addition, during this implementation, no backfire or blow-out phenomenon occurred and a flame-holding effect could be obtained.

Next, another embodiment to which this invention is applied, shown in FIGS. 4 and 5, will be described.

In this embodiment, as shown in FIG. 5, the heat transfer path group A is formed by forming a large number of liquid transport holes 13 in parallel at predetermined intervals in a ceramic plate 12, which communicates between the water supply header 3 and the drainage header 4. At the same time, a large number of gas flow holes 14 are opened between each liquid transport hole 13 to allow the premixed gas to pass from the bottom surface to the top surface. In addition,
This gas distribution hole 14 does not interfere with the liquid transport hole 14, and allows the premixed gas supplied from below to
Any structure is sufficient as long as it allows passage upward, and for example, as shown in FIG. 5, it may be opened at an angle with respect to the vertical direction of the ceramic plate 12. Particularly, when the gas flow holes 14 are inclined in this manner, the above-mentioned flame extinguishing distance is sufficiently ensured, and backfire can be reliably prevented.

In this embodiment, as shown in FIG. 4, a heat transfer path group A made of ceramic plates 12 is arranged between a straight pipe-shaped water supply header 3 and a drainage header 4 arranged in parallel. However, it is of course possible to arrange the headers 3 and 4 along the periphery of the heat transfer path group A, as in the embodiment described above.

Further, in this embodiment as well, a porous body 8 is provided, and the heat transfer path group A and this porous body 8 are
A similar flame-holding effect can also be obtained by generating surface combustion in the space 9 between the two.

Although the embodiments have been described above, in the present invention, the liquid to be heated is not limited to water, but various liquids can be heated depending on the purpose.

Further, the area, shape, etc. of the heat transfer path group A can be changed in design as appropriate, and there is no particular need for it to be rectangular.

Further, in the above embodiment, the porous body 8 is made of ceramic material, but other materials such as metal rope, asbestos, etc. can also be used.

〔Effect of the invention〕

As is clear from the explanation above, even when the premixed gas is burned under high load, no blow-off or blow-off phenomenon occurs, and even when burned under low load, no backfire occurs, which greatly improves safety. It has the effect of improving

In addition, by adopting a configuration that allows surface combustion to occur in the narrow space between the heat transfer path group and the porous object, it is possible to reduce the area and volume of the heat exchange section, making it compact and space-saving. This has the effect of making it possible to create a hot water supply system that does not require a conventional method.

Furthermore, since the porous object that is heated during combustion completely burns the premixed gas, there is no need for a long combustion chamber that is installed in conventional water heaters to prevent incomplete combustion. Combined with the miniaturization of the heat exchange section, fundamental miniaturization is possible.

Furthermore, the flame temperature is lowered due to the planar combustion and the cooling effect of the heat transfer path group, which has the effect of suppressing the generation of harmful nitrogen oxides.

Furthermore, since the heat transfer path group receives indirect heating due to radiant heat from the combustion of the premixed gas and heat radiation from the heated porous object, it has the effect of improving the heat exchange rate.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway perspective view of a flame stabilizing device for heat exchange to which the present invention is applied, Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1, and Fig. 3 shows the combustion state in the same embodiment. FIG. 4 is a perspective view showing a state in which a group of heat transfer paths is attached to a water supply header and a drainage header in another embodiment to which the present invention is applied;
Fig. 5 is a partially cutaway enlarged perspective view showing the heat transfer path group;
The figure is an explanatory diagram showing a conventional water heater. 3...Water supply header, 4...Drain header, 5...Heat transfer thin tube, 6...Thin wire, 7.
...Small gap, 8...Porous object, 9...
····space. IKs diagram Figure 4 Figure 5

Claims (3)

[Claims] (1) It has a large number of heat transfer paths that communicate between the supply header and the drain header for the liquid to be heated, and has a small gap that allows the premixed gas supplied from below to pass upward. A flame holding device for heat exchange, comprising a group of heat transfer paths provided between the heat transfer paths, and a porous object provided above the group of heat transfer paths with a narrow space interposed therebetween. . (2) The flame stabilizing device for heat exchange according to claim 1, wherein the heat transfer path is constituted by a thin tube. (3) The heat transfer path group consists of a large number of liquid transport holes that are penetrated through a heat-resistant block such as ceramics, and the heat-resistant block has a large number of holes that do not interfere with the liquid transport holes and are penetrated in the vertical direction. The flame stabilizing device for heat exchange according to claim 1, wherein holes for gas circulation are provided.