JP2002005593A - Ceramic component of heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plate rib type heat exchanger which can be used even under high temperature. SOLUTION: A plurality of ceramic ribs 3 are provided integrally on at least one side of a ceramic plate 2 wherein the ceramic principally comprises at least one kind of alumina, aluminum nitride, silicon nitride, silicon carbide, boron carbide, mullite, and cordierite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat exchanger,
In particular, the present invention relates to a plate-rib type heat exchanger suitable for repeated use at a high temperature for a long time such as a chemical plant, a fuel cell plant, a gas turbine, or a micro gas turbine.

[0002]

2. Description of the Related Art A plate fin type heat exchanger, which is a heat exchanger which is excellent in heat exchange efficiency and can be miniaturized, is widely used as a heater for heating a gas or liquid to a predetermined temperature.

The temperature of a high-temperature fluid is 500 ° C. or more in a chemical plant or a fuel cell power plant, etc., and 800 ° C. or more in a gas turbine or a micro gas turbine. Times,
The time of exposure to high temperatures reaches tens of thousands to hundreds of thousands of hours, and recently, the temperature of the high-temperature fluid tends to increase.

The internal structure of this heat exchanger is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 7-167580, as shown in FIG. 6, a flat plate 81 for separating a low-temperature fluid passage from a high-temperature fluid passage, and a heat-transfer plate for promoting heat transfer. Fins 82 are alternately stacked. Further, spacer bars 83 are arranged on both side surfaces. Then, in order to increase the heat transfer from the fins 82 to the flat plate 81,
The fins 82 and the flat plate 81 are connected by welding and laminated to form a core 85.

Here, the fins of the plate fin type heat exchanger are provided to promote heat exchange between the flat plate and the fluid and to enlarge the heat transfer area, and are made of a heat-resistant alloy made of stainless steel or the like. There are various shapes, and a corrugated shape is generally used.

[0006]

However, the temperature of the fluid is increasing, and particularly in a heat exchanger handling a high temperature fluid of 800 ° C. or more, the flat plate 81 and the plate fin described in Japanese Patent Application Laid-Open No. 7-167580. The components constituting the heat exchanger such as the fins 82 and the spacer bars 83 of the mold heat exchanger are softened with metal, the strength of the joint is reduced, and there is a problem of peeling.

In the conventional core structure of the plate-fin type heat exchanger, the fin 82 is repeatedly compressed or buckled and stretched by repeatedly raising and lowering the temperature of the heat exchanger. Damage due to fatigue accumulates at the joint with the flat plate 81, and further, creep damage is added at a high temperature, and the damage of the joint between the fin 82 of the core 85 and the flat plate 81 increases during a long-term operation. And finally had the problem of cracking.

Further, although ceramics is a material that can withstand high temperatures, conventional plate fin type heat exchangers have corrugated fins 82 welded to a flat plate 81 to form such a complicated structure with ceramics. Is difficult,
It was necessary to reconsider the heat exchanger based on a new idea.

Accordingly, an object of the present invention is to provide a plate-rib type heat exchanger which can be easily manufactured from a ceramic material and can be used even at a high temperature.

[0010]

SUMMARY OF THE INVENTION According to the present invention, a fin structure of a plate fin type heat exchanger has a rib structure, and the ribs are optimized by ceramics, so that the ceramics can be used for the plate fin type heat exchanger. ,
It is based on the finding that it can be used as a highly reliable heat exchanger even at high temperatures.

That is, the ceramic heat exchanger component of the present invention is characterized in that a plurality of ceramic ribs are integrally provided on at least one surface of a ceramic flat plate. By adopting this configuration, there is no need for joining by integrating the flat plate and the rib, the heat transfer loss can be reduced, and the manufacture becomes easy, and it is possible to realize ceramics for a heat exchanger.

Preferably, the ceramic flat plate and the ceramic rib are made of a ceramic mainly composed of at least one of metal oxides, nitrides, carbides and borides. In particular, it is preferable to use a ceramic mainly composed of at least one of alumina, aluminum nitride, silicon nitride, silicon carbide, boron carbide, mullite and cordierite. This is because these materials have high chemical stability and excellent mechanical properties and thermal conductivity at high temperatures.

Further, the thermal conductivity of the ceramic plate and the ceramic rib is preferably 20 W / mK or more. This makes it possible to increase the heat exchange rate.

Further, the strength of the ceramic flat plate and the ceramic rib is preferably 250 MPa or more. Thereby, it is possible to withstand the pressure of the fluid and to reduce the failure rate at the time of assembling, moving or operating the heat exchanger.

Further, the method for manufacturing a ceramic heat exchanger component according to the present invention is directed to a method for manufacturing a ceramic heat exchanger component, comprising the steps of: forming a cylindrical compacting roller having a plurality of irregularities engraved on a flat plate surface formed of a mixture of a ceramic powder and an organic binder; The method is characterized by rotating under a constant pressure, forming a rib on at least one surface of the flat plate, and firing.

Further, a viscous fluid comprising a mixture of a ceramic powder and an organic binder is extruded from a slit having irregularities to form ribs on at least one surface of the flat plate of the molded body, and then fired. I do. By these methods, a ceramic in which the flat plate and the rib are integrated can be formed.

Further, the ceramic core for a heat exchanger of the present invention stacks the ceramic heat exchanger constituent parts of the present invention,
A fluid passage is provided between the ribs. With this configuration, a core constituting a heat exchanger that can be used even at a high temperature can be realized.

In particular, the fluid passage is preferably straight, and the concavo-convex shape of the compacting roller for forming the ceramic heat exchanger components can be simplified. This facilitates the production of the ceramic core, increases the yield, and contributes to cost reduction.

Preferably, the fluid passage is non-linear, which increases the efficiency of heat transfer between the fluid and the ribs,
High heat exchange rates can be achieved and throughput and heat exchanger size can be optimized.

Still further, a plate rib type heat exchanger of the present invention is characterized by having the ceramic heat exchanger component and / or the ceramic core for a heat exchanger of the present invention. As a result, a heat exchanger that can operate at a high temperature can be realized.

[0021]

FIG. 1 is a perspective view of the components of a ceramic heat exchanger according to the present invention. According to the heat exchanger component 1 of the present invention, as shown in FIG. 1, a ceramic rib 3 is integrally provided on a ceramic flat plate 2. With this configuration, the flat plate and the fin have been conventionally joined, but the heat exchanger component of the present invention eliminates the need for joining the ceramic flat plate 2 and the ceramic rib 3, and the ceramic rib 3 is connected to the ceramic flat plate 2. The heat transfer loss can be reduced, and the problem of peeling of the joint between the flat plate and the fin can be avoided. Further, since the shape is relatively simple, it is easy to manufacture ceramics having lower toughness than metal.

FIG. 2 is a perspective view of another ceramic heat exchanger component of the present invention. In the heat exchanger component 11 of FIG. 2A, ceramic ribs 13 are integrally provided on both surfaces of a ceramic flat plate 12. The ceramic ribs 13 are provided on opposite sides of the ceramic flat plate 12.

Further, the ceramic heat exchanger component 21 shown in FIG. 2B has a ceramic flat plate 22 on both sides of which ceramic ribs 23 are integrally provided, as in FIG. 2A. This ceramic rib 23 is shown in FIG.
As shown in FIG.

FIG. 3 shows yet another ceramic heat exchanger component of the present invention. FIG. 3 (a)
The ceramic heat exchanger component 31 has a ceramic flat plate 32 on which ceramic ribs 33 are integrally provided on one side, and the ceramic ribs 3, 13, and 23 in FIGS. 3A is a substantially rectangular shape, whereas the ceramic rib 33 shown in FIG. 3A has a polygonal shape. In other words,
The ceramic ribs 33 have a "-"-shaped bent portion, and the flow of fluid between the ribs is disturbed, so that the heat transfer efficiency is increased.

The ceramic heat exchanger component 41 shown in FIG. 3B has a ceramic flat plate 42 and a ceramic rib 43 provided integrally on one surface thereof. Is a shape consisting of multiple repetitions,
It is more preferable to increase the heat transfer efficiency. In particular, it is preferable to increase the bending angle of the above-mentioned "<" to cause turbulence in the fluid and increase the heat transfer efficiency.

The ceramic rib of the ceramic heat exchanger component of the present invention may have a curve such as an "S" shape in addition to the "" shape. For example, the ceramic heat exchanger component 51 shown in FIG. 3C has a ceramic flat plate 52 on which ceramic ribs 53 are integrally provided on one surface, and the ceramic has low toughness. By using it, chipping can be prevented. The non-linear ceramic ribs shown in FIGS. 3A to 3C can be provided on both surfaces of the ceramic flat plate to further enhance the heat transfer efficiency.

The ceramic used in the present invention is at least one of metal oxides, nitrides, carbides and borides.
Preferably, it is made of a ceramic mainly composed of seeds,
In particular, it is preferable to use a ceramic mainly composed of at least one of alumina, aluminum nitride, silicon nitride, silicon carbide, boron carbide, mullite and cordierite. These materials are suitable for use at high temperatures because of their high chemical stability and excellent mechanical properties at high temperatures. Among these, silicon nitride, aluminum nitride, and silicon carbide have a high thermal conductivity, and therefore can be suitably used in terms of a heat exchange rate. In particular, silicon nitride has high fracture toughness and is most suitable in terms of product life.

Further, the ceramic has a thermal conductivity of 2
It is preferably at least 0 W / mK, particularly preferably at least 30 W / mK. This makes it possible to increase the heat exchange rate.

Further, the strength of the ceramic is 2
50 MPa or more, especially 350 MPa or more, furthermore 45
The pressure is preferably 0 MPa or more. Thereby, it is possible to withstand the pressure of the fluid and to reduce the failure rate at the time of assembling, moving or operating the heat exchanger.

The ceramic used in the ceramic heat exchanger component of the present invention has a fracture toughness of 3 MPa.
m ^1/2 or more, especially 4 MPa · m ^1/2 or more, and further 5 MP
a · m ^1/2 or more is preferable for increasing the product yield.

Furthermore, the relative density of the ceramic used in the ceramic heat exchanger component of the present invention is preferably 95% or more, particularly 97% or more, more preferably 98% or more, and most preferably 99% or more. This reduces the amount of porosity, increases strength and thermal conductivity, and makes it difficult for microorganisms, dust, and the like in the fluid to adhere, so that the number of maintenance operations can be reduced.

The ceramic heat exchanger component of the present invention having the above-described structure can be used at a high temperature by using a fin structure having a rib structure optimized for ceramics and using a specific material. By integrating the ribs and the ribs, there is no need for joining, so that the production becomes easy, the heat transfer loss can be reduced, and the heat exchange rate can be increased.

Next, a method of manufacturing the above-described ceramic heat exchanger components will be described.

First, a desired ceramic powder and an organic binder are mixed to form a ceramic flat plate having ribs.

As shown in FIG. 4, for example, the first method of forming a molded body is as follows: first, a known molding method such as a die press, a casting molding, a cold isostatic pressing, an extrusion molding, a doctor blade method, or the like. On the surface of the formed body 61 of the formed body 61, a cylindrical pressure roller 63 in which a plurality of irregularities are engraved is moved under a constant pressure in the X direction while rotating in the direction r as indicated by an arrow to form the recess 65. A corresponding rib 67 is formed.

In particular, in order to form ribs on both sides of a ceramic flat plate, a compact or viscous fluid, which is made of a mixture of ceramic powder and an organic binder and is easily deformed, is passed between a pair of compaction rollers. By transferring the unevenness of the roller from the lower surface, a molded body having ribs on both surfaces can be formed. In addition, one of the rollers may be of a fixed type, and may not be of a cylindrical shape. Further, since the formed body or the viscous fluid spreads in the lateral direction between the upper and lower rollers, it is preferable to provide a wall surface for suppressing the spread.

In the second method of forming a compact, a compact can be obtained by a method of extruding a viscous fluid comprising a mixture of a ceramic powder and an organic binder from a slit having irregularities, that is, a so-called extrusion molding method. In such a method, a molded article having ribs on one or both sides can be easily formed by changing the shape of the slit in various ways.

Then, the member as shown in FIGS. 1 to 3 can be manufactured by heating and sintering the obtained molded body to a temperature at which each ceramic can be sufficiently sintered.

As described above, since the ceramic rib is provided integrally on at least one surface of the ceramic flat plate at the time of molding, the sintered body obtained by firing is used as a component of the ceramic heat exchanger, so that the ceramic rib is formed by heat conduction. By improving the heat transfer property, the heat exchange rate can be increased.

In the conventional plate fin type heat exchanger, it is necessary to join the flat plate and the fins by welding or the like, which causes difficulties in manufacturing, high cost and heat transfer loss. According to this, since the flat plate and the rib can be integrally formed, these problems can be solved and mass productivity can be improved. Particularly, when the ceramic heat exchanger components are stacked and used, the ribs can be arranged so as to be in contact with each other, so that the height of the ribs can be reduced by forming the ribs on both sides of the flat plate. Thereby, the heat transfer loss can be reduced and the heat exchange rate can be improved.

The ceramic heat exchanger components of the present invention formed as described above and shown in FIGS. 1 to 3 are stacked to form a ceramic core for a heat exchanger having a plurality of fluid passages between ribs. In stacking, the ribs may be integrally formed by joining the ribs or the ribs and the flat plate, but the joining is not necessarily required. Do not join, just stack and fix the side,
By storing in a container, manufacture becomes easy and cost can be reduced.

Further, the ceramic heat exchanger component parts of the present invention may be cut into desired dimensions, stacked and fired to form a ceramic core for a heat exchanger.

In the ceramic core for a heat exchanger of the present invention, the fluid passage may be straight like the rib of FIG. 1 or FIG. 2, or may be non-linear like the rib of FIG. In the case of a straight line, manufacturing is easy and the shape of the compacting roller can be simplified,
Manufacturing yield can be increased and costs can be reduced. Extrusion molding can also be used easily.

When the direction of travel of the fluid is deflected at at least one location and the fluid passage is non-linear, the pressure of the fluid applied to the ribs increases, and the heat transfer efficiency increases. In particular,
When a fluid generates turbulence, a high heat exchange rate can be achieved, and the throughput and the size of the heat exchanger can be optimized. The formation of such ribs can be achieved by a method of extruding the viscous fluid while rotating, by moving the shape of the concavities and convexities of the roller, moving the position of the slit, and rotating the viscous fluid.

Further, since the plate-rib type heat exchanger of the present invention includes the ceramic heat exchanger constituent parts and / or the ceramic core for the heat exchanger of the present invention, the ceramic heat exchanger can be easily manufactured and the high temperature can be obtained. And a heat exchanger having a high heat exchange rate can be realized.

For example, FIG. 5 is a perspective view showing a part of a plate rib type heat exchanger. As shown in FIG. Are formed integrally with each other, and the components are stacked in five stages to form a ceramic core 75 for a heat exchanger.

The case 76 may be made of metal, but is preferably made of ceramics in consideration of corrosion and deformation due to high temperature fluid. In particular, the heat conductivity of the case 76 is set to 20 W / m so that the heat from the case 76 does not escape to the outside.
K or less, especially 15 W / mK or less, further 10 W / mK
The following is preferred.

Since the case 76 contacts the high-temperature fluid and the low-temperature fluid, the thermal expansion coefficient of the case 76 at 40 to 800 ° C. is set to 1 × 10 ⁻⁵ / ° C. in order to reduce the generated thermal stress.
^Or less, especially 8 × 10 ⁻⁶ / ° C. or less, and further 5 × 10 ⁻⁶ / ° C.
C. or lower, more preferably 3.5 × 10 ⁻⁶ / ° C. or lower, and most preferably 2 × 10 ⁻⁶ / ° C. or lower.

In FIG. 5, the fluid passages are divided into five stages, and the high-temperature fluid passages and the low-temperature fluid passages are alternately arranged in the opposite directions. You can change it. The number of stages is not limited to five, and a desired number of stages can be used. Further, although not shown in FIG. 5, since the two fluids need to be separated, it is necessary to provide a device for separating the two types of fluids at both ends of the heat exchanger.

[0050]

EXAMPLE 18 kg of α-type silicon nitride silicon nitride powder having a particle diameter of 0.5 μm, 18 kg of Y ₂ O ₃ powder having a particle diameter of 1.0 μm,
20 kg of silicon nitride balls, 20 kg of methanol and 2 kg of an organic binder were weighed, mixed and pulverized by a barrel mill for 30 hours, and formed into a compact by a roll rolling method. That is, the viscous fluid obtained by the barrel mill is poured between a pair of compaction rollers, and the pair of ceramic ribs is integrally formed with the ceramic flat plate at a position where the pair of ceramic ribs face each other as shown in FIG. The formed molded body was formed. Here, the number of ribs is 90, the rib thickness is 2 mm, the height is 4 mm, the rib interval is 3 mm, and the shape of the ceramic flat plate is 450 × 450 × 2.
mm.

Next, the compacts were laminated, and the
Degreased by heat treatment at 20 ° C for 20 hours, then 1900 ° C in nitrogen
At the above temperature to produce a ceramic heat exchanger component. The obtained sintered bodies were stacked alternately orthogonally to produce a ceramic core for a heat exchanger. That is, the ceramic core for a heat exchanger was configured such that the high-temperature fluid and the low-temperature fluid were orthogonal to each other. Also, an alumina container was prepared. And
The ceramic core for a heat exchanger was packed in a container to obtain a plate-rib type heat exchanger.

The operation of the heat exchanger was confirmed using low-temperature air at 25 ° C. and high-temperature fluid at 800 ° C. No abnormality was found in the device in both the production stage and the operation stage, and the temperature efficiency was 80%.

Note that the temperature efficiency used above is such that the inlet temperature of the low-temperature fluid is T _{Low (in)} , and the outlet temperature of the low-temperature fluid is T _{Low (in)} .
_{When low (out)} and the inlet temperature of the high-temperature fluid are T _{High (in)} , (T _{Low (out)} −T _{Low (in)} ) / (T _{High (in)} −
T _{Low (in)} ).

[0054]

The plate-rib type heat exchanger of the present invention can be used as a highly reliable heat exchanger even at high temperatures by optimizing the rib structure for ceramics.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a structure of a ceramic heat exchanger component of the present invention.

FIG. 2 is a perspective view showing another structure of the ceramic heat exchanger component of the present invention, a) a structure having opposing ceramic ribs, and (b) a ceramic rib at a position shifted from the opposing position. Structure.

FIGS. 3A and 3B show still another structure of the ceramic heat exchanger component of the present invention, wherein FIG. 3A is a perspective view of a structure having a bent portion, and FIG. FIG. 3C is a plan view of a structure having a plurality of “S” -shaped bends.

FIG. 4 is a conceptual diagram illustrating a method for manufacturing a ceramic heat exchanger component of the present invention.

FIG. 5 is a perspective view schematically showing a part of the plate-rib type heat exchanger of the present invention.

FIG. 6 is an exploded perspective view showing the structure of a conventional ceramic core for a heat exchanger.

[Explanation of symbols]

 1, 11, 21, 31 ... core components for heat exchanger 2, 12, 22, 32 ... ceramic flat plate 3, 13, 23, 33 ... ceramic rib

Claims (11)

[Claims] 1. A ceramic heat exchanger component, wherein a plurality of ceramic ribs are integrally provided on at least one surface of a ceramic flat plate. 2. A ceramic heat exchanger according to claim 1, wherein said ceramic flat plate and said ceramic rib are made of a ceramic mainly composed of at least one of metal oxides, nitrides, carbides and borides. Component part. 3. The ceramic flat plate and the ceramic rib are made of a ceramic mainly composed of at least one of alumina, aluminum nitride, silicon nitride, silicon carbide, boron carbide, mullite and cordierite. The ceramic heat exchanger component according to claim 1 or 2. 4. The ceramic heat exchanger component according to claim 1, wherein the thermal conductivity of the ceramic flat plate and the ceramic rib is 20 W / mK or more. 5. The ceramic heat exchanger component according to claim 1, wherein the strength of the ceramic flat plate and the ceramic rib is not less than 250 MPa. 6. A compact roller made of a mixture of a ceramic powder and an organic binder, which is rotated under a constant pressure on a surface of a compact roller having a plurality of concaves and convexes formed on the surface of the compact, thereby forming at least one of the compact flat plates. Forming a rib on a surface of the ceramic heat exchanger and then firing the rib. 7. A molded body flat plate is formed by extruding a viscous fluid comprising a mixture of a ceramic powder and an organic binder from a slit having irregularities to form a rib on at least one surface of the molded body flat plate, and then firing. Of manufacturing ceramic heat exchanger components. 8. A ceramic core for a heat exchanger, wherein the ceramic heat exchanger components according to claim 1 are stacked and a fluid passage is provided between the ribs. 9. The ceramic core for a heat exchanger according to claim 8, wherein said fluid passage is straight. 10. The ceramic core for a heat exchanger according to claim 8, wherein said fluid passage is non-linear. 11. A ceramic heat exchanger component according to any one of claims 1 to 5, and / or a ceramic core for a heat exchanger according to any one of claims 8 to 10. Plate-rib type heat exchanger.