JPH0335108B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to improving 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 that they are arranged alternately in the vertical direction 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 are significantly different, the heat transfer area on the gas side will be significantly insufficient, and the heat transfer area on the water side will have a large margin, resulting in an unbalanced heat transfer and Replacement rate decreases.

"Objective of the Invention" The object of the present invention is to be applicable to heat recovery from high-temperature or corrosive exhaust gas, to have high heat exchange efficiency, and to reduce specific heat and partition walls like heat exchange between gas and liquid. Suitable for heat exchange between fluids with different heat transfer coefficients on both sides, and when assembling the honeycomb body itself,
It is an object of the present invention to provide a ceramic structure that can prevent damage during sintering or use, and can keep the tube-inserted portion of the outer wall of a honeycomb body airtight.

"Summary of the Invention" A ceramic structure according to the present invention includes a ceramic honeycomb body formed by laminating a plurality of layered parts, a thick ceramic end plate fixed to an outer wall of the honeycomb body, and It is characterized by comprising a ceramic tube inserted through and fixed to the end plate and the honeycomb body so as to intersect with the ventilation path of the honeycomb body.

Therefore, by flowing a high-density fluid such as water through the tubes and passing a low-density fluid such as exhaust gas through the ventilation channels of the honeycomb body, the heat transfer area is larger than that of the high-density fluid, which has a high heat transfer coefficient. By increasing the heat transfer area on the low-density fluid side with a low heat transfer coefficient, it is possible to improve heat balance and improve heat exchange efficiency. Further, since the outer wall of the honeycomb body is protected by the end plate, damage to the corners of the honeycomb body can be avoided.

In one preferred embodiment of the present invention, the thickness of the end plates is at least twice the thickness of the partition walls of the honeycomb body.

In another preferred embodiment of the present invention, the end plate and the insertion hole through which the tube is inserted are positioned with higher precision than the tube insertion hole of the honeycomb body.

In yet another preferred embodiment of the present invention, the end plate and the tube are airtightly fixed by a fixing material applied to the abutting portions of the two. Therefore,
Low-density fluid such as exhaust gas flowing into the ventilation passages of the honeycomb body will not leak from the gap between the abutting portions of the honeycomb body, and the heat exchange efficiency can be further improved.

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

In FIG. 1, one example of the structure of the honeycomb body 11 is shown. The honeycomb body 11 is made up of, for example, ceramic corrugated plates 12 and similarly ceramic flat plates 13 stacked alternately. As shown in FIG. 1, for example, these two layers are stacked such that the peaks of the corrugated sheets 12 sandwiched between the flat plates 13 run parallel to each other. Another example of lamination of both is as shown in FIG. 2, in which the running directions of the peaks of the corrugated sheets 12 sandwiched between the flat plates 13 are alternately orthogonal to each other. Still another example of lamination of both is as shown in FIG.
A stacked body running parallel to each other with the two stacked bodies in between is divided into two parts, and the running of the peaks of one stacked body is perpendicular to the running of the peaks of the other stacked body.

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 parallel to each other in FIG. 1, alternately run perpendicular to each other in FIG. 2, and in FIG. perpendicular to the side. Each of these cells 14 functions as a fluid ventilation path. In the case of a ceramic structure having a honeycomb body as shown in Fig. 2 or 3, the same type of gas fluid is flowed through a group of air passages parallel to each other and a group of air passages perpendicular to these. Alternatively, different types of gas fluids having different temperatures and/or compositions may be flowed.

Ceramic end plates 15 are arranged on the outer wall surface of the honeycomb body 11 stacked in this manner so as to press the honeycomb body 11 from both sides thereof. The thickness of the end plate 15 is approximately four times that of the corrugated plate 12 and the flat plate 13, and the honeycomb body 1
1 is reinforced to prevent damage, especially to the ends of the honeycomb body 11. A plurality of through holes 16 and 17 are formed in the end plate 15 and the honeycomb body 11, respectively, and the through holes 16 and 17 intersect with the running direction of the cells 14, and a plurality of tubes 18 made of ceramics are inserted into the holes. . Insertion hole 1 of end plate 15
7 is drilled and positioned with particularly higher fitting precision than the insertion hole 16 of the honeycomb body 11.
This facilitates positioning of the tube 18. That is, the corrugated plate 12 and the flat plate 13 are thin, and it is generally difficult to achieve high precision in surface shape, and high precision is often not required. Therefore, the insertion holes 16 of the honeycomb body 11 are often not necessarily highly accurate. On the other hand, since the end plate 15 is thick and generally flat, the insertion hole 17 can be easily provided with high precision, and the desired sealing performance can thereby be ensured. In this case, the diameter of the inserted tube 18 is made smaller than the longitudinal dimension of the cross-sectional shape of each cell 14, or alternatively, the diameter of the tube 18 is made smaller than twice the longitudinal dimension of the cross-sectional shape of each cell 14. If so, the center of the tube 18 may be located on a line connecting the intermediate slope between the peak and trough portions of the corrugated plate 12.

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 12 having a sine curve cross section.
Then, the tube 18 is formed into a flat plate 13, and an insertion hole 16 is punched in the portion where the tube 18 is to be inserted. The end plate 15 is made of carbon paper four times thicker than the corrugated plate 12 and the flat plate 13, especially carbon paper mixed with resin,
After positioning the insertion hole 8 with high precision at the part to be inserted, the insertion hole 17 is punched out. Such corrugated plates 12 and flat plates 13 are alternately laminated or bonded, and after aligning the insertion holes 16 and 17, end plates 15 are bonded to both end surfaces to form a predetermined honeycomb shape. In this case, insertion hole 1
6 and 17 may be formed after the end plates 15 are bonded to the honeycomb body 11. And this insertion hole 1
A tube 18 made of carbon paper, especially resin-blended carbon paper, is inserted through tubes 6 and 17 to obtain a honeycomb-shaped 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 18 and the abutting portions between the end plates 15 and the tubes 18. Next, the entire honeycomb body 11, the end plates 15 and the tubes 18 are subjected to reaction sintering.
changes to silicon carbide or silicon carbide/silicon, and many of the minute spaces between silicon carbides are filled with silicon. Further, most of the contact portions between the corrugated plate 12, the flat plate 13, the end plate 15, and the tube 18 are filled with silicon, and some of it is further converted into silicon carbide, which becomes a strong fixing material. The tube 18 is firmly joined to the corrugated plate 12, the flat plate 13, and the end plate 15 through this bonding material, and the thermal resistance therebetween is so small as to be virtually negligible. In particular, since the tube 18 and the end plate 15 are airtightly joined by the fixing material, the low-density fluid flowing into the cell 14 will not leak from the abutting portion between the two. Further, after pouring a glaze or a glaze suspension into the inner surface of the tube 18, the airtightness of the tube 18 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.

Opening 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: 4.9 mm Number of tubes 18: 33 Outer diameter of tubes 18: 7 mm Thickness of end plate 15: 2.4 mm Effective heat transfer area: 1.4 m ^2This structure is housed in a casing, and tube 1
Connect both ends of 8 to a metal header and pour water at 30℃.
The flow rate was maintained at 20/min and allowed to flow through the tube 18. 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 performed at 450°C, 300°C, and 200°C. The results are shown in FIG. In the figure, a is Tg=450℃, b is
Tg=300°C and c represent the case when Tg=200°C, respectively. As is clear from the test results, although this structure is extremely compact,
It can be seen that the amount of heat exchange, that is, the amount of heat transfer, and the overall heat transfer coefficient are extremely large. Therefore, when used as a device for recovering heat from the exhaust gas of a bus equipped with a diesel engine, for example, the water flowing through the tube 18 is efficiently heated by the heat of the exhaust gas, and the water flowing through the tube 18 is efficiently heated, for example. It can be used to heat the inside of a car by sending it to a separately installed fan heater. 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, tube 1
The fluid passed through the 8 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 the structure of the present invention has an advantageous configuration in terms of thermal balance when heating these fluids. It's summery.

In the present invention, the tubes 18 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 18 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 18 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. Further, since fluid such as gas is flowed through the partition walls of the honeycomb body that act as fins, the pressure loss of the fluid passing therethrough 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 can prevent soot firing and acid dew point corrosion. can be countered. In addition, the thickness of the tube,
By adjusting the material and processing method, it is easy to prevent fluid leakage, and furthermore, the generated thermal stress can be suppressed to a low level.
In addition, thick end plates are pressed and bonded to the outer wall of the honeycomb body from both sides, so they can be used during assembly before firing, during firing, when connecting metal headers, and even when used as a heat exchanger. During the process, damage to the honeycomb body can be prevented. Further, when the end plate is a thick plate, sealing and assembly between the end plate and the metal casing are facilitated. Furthermore, it is easier to fit and position the tube insertion holes of the end plates with higher precision than that of the honeycomb body, and it is also easier to secure the abutting portions of the two airtightly with adhesive material. Also, it is possible to avoid a situation in which the low-density fluid passing through the cell leaks to the outside from the contact portion. In addition, by using paste between the insertion hole of the thick end plate and the tube before firing to ensure fixation, it is possible to prevent the corrugated plate 12 or flat plate 13 from loosening and coming off the tube by the time of firing. No more troubles. Further, when the end plate is a thick plate, its rigidity can prevent dimensional deviations due to warpage of the honeycomb body during degreasing and firing.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of the present invention;
FIG. 2 is a perspective view showing another embodiment of the honeycomb body constituting the present invention, FIG. 3 is a perspective view showing still another embodiment of the honeycomb body constituting the present invention, and FIG. 4 is the perspective view shown in FIG. FIG. 5 is a performance curve diagram of the structure shown in FIG. 4, and FIG. 6 is a perspective view of a conventional ceramic structure. 11...honeycomb body, 12...corrugated plate, 13...
Flat plate, 14... Cell, 15... End plate, 16, 17
...Through hole, 18...Tube.

Claims (1)

[Scope of Claims] 1. A ceramic honeycomb body formed by laminating a plurality of layered parts, a thick ceramic end plate fixed to an outer wall of the honeycomb body, and a ceramic end plate that intersects with a ventilation path of the honeycomb body. A ceramic structure comprising: a ceramic tube inserted through and fixed to the end plate and the honeycomb body. 2. The ceramic structure according to claim 1, wherein the thickness of the end plate is at least twice the thickness of the partition walls of the honeycomb body. 3. The insertion hole of the end plate through which the tube is inserted is positioned with high precision.
A structure made of ceramics as described in Section. 4. The ceramic structure according to claim 1, wherein the end plate and the tube are airtightly fixed by a bonding material applied to the abutting portions of the end plate and the tube.