JPH0588183B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a ceramic structure suitable for recovering thermal energy contained in exhaust gas from, for example, a diesel engine or a boiler.

"Prior art and its problems" In structures such as heat exchangers that use tubes, when a fluid such as water flows inside the tubes and gas flows outside the tubes, providing fins on the outside of the tubes will reduce heat. It is well known that exchange is effective. For this reason, it is widely practiced to wrap metal fins around a metal tube to form a finch tube. However, when high-temperature gas exceeding 800°C is forced to flow outside the tube, ordinary metal fins do not have the heat resistance, and special heat-resistant alloys have drawbacks such as being expensive and having poor thermal conductivity. In addition, when exhaust gas from a diesel engine, etc. is used as a fluid outside the tube, the black smoke powder contained in the exhaust gas causes intermittent and local soot firing, causing high temperature areas exceeding the melting point of the metal fin. Therefore, it was difficult to use metal fins. Furthermore, when fuel combustion gas containing impurities such as sulfur is used as a fluid outside the tube, low-temperature corrosion of the outer surface of the fins and tubes becomes a problem, and the life of ordinary metals as a heat exchanger is significantly shortened. It had the disadvantage of being

As a way to solve these drawbacks, it is easy to think of a method of making a ceramic tube and a ceramic fin separately and gluing them together, or a method of making a finned tube by ceramic casting, injection molding, or hydraulic press. It has not yet been put to practical use because a technique for bonding fins with low thermal resistance has not been established, and a uniform molding technique that is less likely to generate thermal stress cannot be obtained at low cost.

On the other hand, structures using ceramic honeycombs are known (for example, see Utility Model Laid-Open No. 56-93695 and Japanese Patent Laid-open No. 57-31792). For example, as shown in FIG. A first fluid passage 2 is formed vertically in parallel so as to pass through a pair of opposing walls of 1, and a second fluid passage 3 is formed in the passage 2 so as to pass through another opposing wall. On the other hand, those formed so as to be arranged vertically with thin partition walls interposed therebetween are also used. This structure 1 has no problem when the specific heat and heat transfer coefficient on both sides of the partition wall are the same, such as when exchanging heat between exhaust gas and air. If the heat transfer coefficients on both sides of are significantly different, then
The heat transfer area on the gas side is significantly insufficient, and the heat transfer area on the water side is left with a large margin, resulting in poor heat transfer balance and reduced heat exchange efficiency.

"Objective of the Invention" The object of the present invention is to be able to be applied to heat recovery from high-temperature or corrosive exhaust gas, etc., to have high heat exchange efficiency, and to have a high specific heat and partition wall as in heat exchange between gas and liquid. It is an object of the present invention to provide a ceramic structure suitable for heat exchange between fluids having different heat transfer coefficients on both sides of the body, and which can be manufactured to any size according to demand.

"Summary of the Invention" A ceramic structure according to the present invention includes a ceramic honeycomb body and a ceramic tube inserted through the honeycomb body so as to intersect with the air passages of the honeycomb body. The honeycomb body is a structure made of corrugated sheets or a corrugated sheet and a flat sheet laminated together,
All of the ventilation passages formed by this lamination are arranged in parallel.

Therefore, by passing a high-density fluid such as water through the tubes and flowing a low-density fluid such as exhaust gas through the ventilation channels of the honeycomb body configured by the above-mentioned laminated layers, the high-density fluid side with a high heat transfer coefficient can be By increasing the heat transfer area on the low-density fluid side, which has a lower heat transfer coefficient than the heat transfer area of , it is possible to improve heat balance and improve heat exchange efficiency.

In a preferred embodiment of the present invention, the honeycomb body is formed by abutting the peaks of two adjacent corrugated plates with a flat plate in between.

In another preferred embodiment of the present invention, the honeycomb body is formed by abutting the crests of corrugated sheets facing each other, and the cross-sectional area of the cells formed thereby is greater than when the above-mentioned flat plates are interposed. It is approximately twice as large as the previous year. Therefore, when heat is recovered from exhaust gas containing a lot of soot, it is possible to reduce the possibility that soot will accumulate on the inner wall of the ventilation passage and increase the pressure loss on the gas side.

In another preferred embodiment of the present invention, the honeycomb body is formed by abutting the corrugated portions of flat corrugated plates having small protruding corrugated portions on both surfaces alternately.

In a further preferred embodiment of the present invention, the honeycomb body has a corrugated plate in which a sine curve is gently formed, and the corrugated plate has corrugated parts that further protrude at the peaks and troughs, and the corrugated plate faces each other with a flat plate in between. They are alternately laminated. By forming the honeycomb body into such a shape, it is possible to reduce the pitch between the fin plates.

According to these aspects, it becomes easy to select the tube insertion hole to be drilled in the corrugated plate.

In yet another preferred embodiment of the present invention, the honeycomb body is formed by alternately laminating corrugated plates and flat plates, with the corrugated plates having their peaks and valleys oriented in the same direction. According to this, at the contact area between the corrugated plate and the flat plate, the flat plate is in contact with only one corrugated plate, so
Less prone to damage due to thermal stress, etc.

In the present invention, both the corrugated plate and the flat plate as described above are made of ceramics having high thermal conductivity. Preferred examples of such ceramics with high thermal conductivity include those whose main component is one or more selected from silicon carbide, silicon nitride, aluminum nitride, sialon, and silicon. A material containing silicon carbide and silicon as main components is preferable. However, the materials of the ceramics that make up the corrugated plate and the flat plate are not necessarily limited to these.
For example, oxide-based ceramics with high thermal conductivity such as alumina and magnesia may also be used in some cases. The thermal conductivity of the ceramic forming the corrugated plate or flat plate is preferably 15 Kcal/m/hr/°C or higher, particularly 50 Kcal/m/hr/°C or higher.

In manufacturing the structure of the present invention by such a lamination method, for example, carbon paper, especially resin-containing carbon paper, is formed into a corrugated shape, and these are laminated or bonded to form a predetermined shape. It has a honeycomb shape. After cutting out the tube insertion portion so as to penetrate the corrugated plate of the obtained honeycomb-shaped product, a tube made of carbon paper, especially carbon paper mixed with resin, was inserted, and then these tubes were placed in a molten metal silicon bath. By immersing a part of the metal silicon, the metal silicon is completely impregnated by capillary action, and
The gaps between the abutting portions of the honeycomb body and the tubes are also filled with metallic silicon, and then by reaction sintering, the honeycomb body, the tubes, and the bonding material change to silicon carbide or silicon carbide/silicon. A solid structure is obtained. In this case, the step of cutting out the tube insertion portion may be performed on the corrugated sheet before it is laminated or bonded, and the tube may be made of silicon carbide in advance. Furthermore, before treatment with a molten metal silicon bath, a portion or substantially all of the resin may be removed by heat treatment or bath medium treatment.

"Embodiments of the Invention" Preferred embodiments of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, a honeycomb body 11 is made up of corrugated ceramic plates 12 and ceramic flat plates 13 stacked alternately. When stacking, in this embodiment, the peaks of two adjacent corrugated sheets 12 with the flat plate 13 in between are butted against each other. A large number of cells 14 each having a semicircular cross section are formed by laminating the corrugated plate 12 and the flat plate 13 in this manner.
The cells 14 run in parallel and each function as a ventilation path. On both end faces of the honeycomb body 11 laminated in this manner, end plates 15 made of ceramic with guaranteed dimensional accuracy are arranged to prevent damage and protect the honeycomb body 11. End plate 15
The honeycomb body 11 is provided with a plurality of through holes perpendicularly intersecting the running direction of the cells 14, and a plurality of ceramic tubes 16 are inserted into the holes. In this case, the inserted tube 16
In order to prevent each cell 14 from being occluded by
The center of the tube 18 may be located on a line connecting the intermediate slope between the peak and valley of the corrugated sheet 12, as long as it is less than twice that.

In manufacturing the structure of the present invention by such a lamination method, carbon paper, particularly resin-blended carbon paper, is used as a corrugated plate 1 having a sine curve cross section.
2 and flat plate 13, then tube 16
The part to be inserted is punched out. Such corrugated plates 12 and flat plates 13 are alternately laminated or bonded, and end plates 15 having insertion holes formed on both end surfaces are bonded to form a predetermined honeycomb shape.
The size of the corrugated plate 12 and the flat plate 13, and the laminated thickness of both can be freely changed according to demand. In this case, the insertion holes may be formed in the honeycomb body 11 obtained by alternately laminating corrugated plates 12 and flat plates 13. Then, a tube 16 made of carbon paper, especially resin-blended carbon paper, is inserted into this insertion hole to obtain a honeycomb molded body.

After the resin is removed from the molded body thus obtained, a portion thereof is immersed in a molten metal silicon bath. As a result, metal silicon is impregnated into the entire honeycomb body 11 by capillary action, and is also filled into the gap between the abutting portions of the honeycomb body 11 and the tubes 16. Next, by reaction sintering, the entire honeycomb body 11 and tubes 16 change to silicon carbide or silicon carbide/silicon,
Furthermore, many of the fine spaces between silicon carbide are filled with silicon. Furthermore, a corrugated plate 12, a flat plate 13, an end plate 1
Most of the abutting portions between the tube 5 and the tube 16 are filled with silicon, and some of it is further converted into silicon carbide to become a strong bonding material. The tube 16 is firmly joined to the corrugated plate 12, the flat plate 13, and the end plate 15 through this fixing material, and the thermal resistance therebetween is so small as to be virtually negligible. Furthermore, after pouring a glaze or a glaze suspension into the inner surface of the tube 16, the airtightness of the tube 16 is ensured by sintering it, or by introducing or coating a plastic material such as fluororesin.
Fluid leakage from pinholes and minute cracks is prevented.

The specifications of the structure obtained as described above are as follows.

Frontage A 125mm Height B 132mm Depth C 160mm Number of corrugated plates 12: 23 Number of flat plates 13: 24 (including end plates 15 on both sides) Length between peaks of corrugated plates 12: 22mm Length between peaks of corrugated plates 12 Height between peaks and valleys: 4.9mm Number of tubes 16: 33 Outer diameter of tubes 16: 7mm Effective heat transfer area: 1.4m ^2This structure is housed in a casing, and tubes 1
Connect both ends of 6 to a metal header and add 30℃ water.
The flow rate was kept at 20/min and allowed to flow through the tube 16. On the other hand, exhaust gas from a diesel engine was introduced into the cell 14, which functions as a ventilation path, and the performance of this structure was tested. In addition, the gas inlet temperature
Tg was 450℃, 300℃, and 200℃. The results are shown in FIG. In the figure, a is Tg=450℃, b is Tg=
300°C and c represent the case where Tg=200°C, respectively. As is clear from the test results, although this structure is extremely compact, it has a very large amount of heat exchange, ie, heat transfer, and an overall heat transfer coefficient. Therefore,
For example, in buses equipped with diesel engines,
When used as a device to recover heat from the exhaust gas of the engine, the tube 1
The water flowing through the interior of the vehicle is efficiently heated and can be used for heating the interior of the vehicle by sending it to a separately installed fan heater, for example. Furthermore, transferring the thermal energy of the exhaust gas to the cooling water when starting the engine has a great effect on warming up the engine quickly, so it can also be used as a preheater. Furthermore, by heating water in a system independent of engine cooling water, it can be used in various ways in addition to warming air, such as providing services to bus passengers. In addition, in the present invention, the fluid passed through the tube 16 side is not limited to liquids such as water, but can also be applied to high-density fluids such as high-pressure air and high-pressure gas, and even in heating these fluids, the present invention The structure has an advantageous configuration.

3 to 6 show different embodiments of the honeycomb body 11 formed by laminating corrugated plates 12 or corrugated plates 12 and flat plates 13.

In the embodiment shown in FIG. 3, only corrugated sheets 12 are used, and the corrugated sheets 12 are laminated with their peaks facing each other.
The waveform of each corrugated plate 12 is the same as the example shown in FIG. 1, but since the flat plate 13 is not interposed, the cross-sectional area of the cell 14 is approximately twice that of the case shown in FIG. Therefore, when heat is recovered from exhaust gas containing a lot of soot, it is possible to reduce the possibility that soot will accumulate on the inner wall of the ventilation passage and increase the pressure loss on the gas side.

In the embodiment shown in FIG. 4, flat corrugated plates 18 having small protruding corrugated portions 17 on both surfaces alternately are laminated with the corrugated portions 17 butted against each other. Further, in the example shown in FIG. 5, a flat plate 13 and a corrugated plate 20 having a gently formed sine curve and further protruding corrugated portions 19 at the peaks and troughs are arranged with the corrugated portions 19 facing each other. These are alternately laminated. By forming the honeycomb body 11 in the shape shown in FIGS. 4 and 5, for example, when metal silicon is impregnated, the metal silicon fills a narrow gap and prevents a situation where the metal silicon does not become a fin. It becomes possible to reduce the pitch between the fin plates.

In addition, the embodiment shown in FIG. 6 has a corrugated plate 12 and a flat plate 13.
When the corrugated sheets 12 are alternately laminated, the peaks and valleys of the corrugated sheets 12 are shown oriented in the same direction.
According to this, since the flat plate 13 is in contact with only one corrugated plate 12 at the contact portion between the corrugated plate 12 and the flat plate 13, damage due to thermal stress or the like is unlikely to occur.

In the present invention, the tubes 16 only need to intersect with the ventilation passages of the honeycomb body 11, and therefore, they do not need to be orthogonal to each other, and may be obliquely intersected as appropriate. Further, the tubes 16 do not necessarily have to be parallel to each other, and instead of protruding from the outer surface of the end plate 15, the ends of the tubes 16 may extend up to the outer surface of the end plate 15.

"Effects of the Invention" As explained above, according to the present invention, by inserting tubes into a honeycomb body, a structure having the same effect as a finch tube can be provided at a low cost. In addition, when applied to heat exchange between fluids with significantly different heat transfer coefficients such as water and gas, the surface area of the honeycomb body, or fins, can be freely increased compared to the inner area of the tube, resulting in a good heat balance and heat transfer. Exchange efficiency can be increased. Furthermore, since fluid such as gas is flowed parallel to the partition walls of the honeycomb body that act as fins, the loss of the fluid passing through can be kept low. Furthermore, it can be applied to high pressure gases and corrosive gases that conventional metal heat exchangers cannot handle. For example, when applied to diesel engine exhaust gas, it prevents soot firing and acid dew point corrosion. can be countered. In addition, by adjusting the thickness, material, and processing method of the tube, it is easy to prevent fluid leakage.
The thermal stress generated can also be suppressed to a low level. In addition, since the honeycomb body is formed using a lamination method, the size of the honeycomb body can be changed freely according to demand, and the material and corrugated sheet shape can be easily selected, allowing for inexpensive manufacturing. becomes.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing one embodiment of the present invention;
The figure is a performance curve diagram of the structure shown in Figure 1,
4, 5 and 6 are partially enlarged side views showing different embodiments of the present invention, and FIG. 7 is a perspective view of a conventional ceramic structure. 11... Honeycomb body, 12, 20... Corrugated plate, 1
3...Flat plates 13, 14...Cells, 15...End plates,
16...Tube, 17, 19...Waveform section, 18
...Flat corrugated plate.

Claims (1)

[Scope of Claims] 1. A ceramic structure comprising a ceramic honeycomb body and a ceramic tube inserted through the honeycomb body so as to intersect with the ventilation path of the honeycomb body, The honeycomb body is a ceramic structure in which corrugated plates or corrugated plates and flat plates are laminated, and the ventilation passages formed by the lamination are parallel to each other. 2. The ceramic structure according to claim 1, wherein the lamination of the corrugated sheet and the flat sheet is formed by abutting the peaks of two adjacent corrugated sheets with a flat sheet in between. 3. The ceramic structure according to claim 1, wherein the corrugated sheets are stacked such that the peaks of the corrugated sheets are butted against each other. 4. The lamination of the corrugated sheets is made by stacking flat corrugated sheets having small protruding corrugated portions on both surfaces alternately, butting the corrugated portions of the corrugated sheets facing each other. Ceramic structure. 5. The lamination of the corrugated plate and the flat plate is made by corrugated plates having gently sine curved peaks and troughs with further protruding corrugated parts facing each other at their corrugated parts with the flat plate in between. A ceramic structure according to claim 1. 6. The ceramic structure according to claim 1, wherein the lamination of the corrugated sheet and the flat sheet is such that the peaks and valleys of the corrugated sheet are oriented in the same direction with the flat sheet in between. 7. The ceramic structure according to any one of claims 2 to 6, wherein the corrugated plate and the flat plate are both made of ceramics having high thermal conductivity. 8. The ceramic structure according to claim 7, wherein the ceramic having high thermal conductivity is mainly composed of one or more selected from silicon carbide, silicon nitride, aluminum nitride, sialon, and silicon. .