HONEYCOMB STRUCTURE FOR HEAT EXCHANGER AND HEAT EXCHANGER

Abstract

A honeycomb structure for a heat exchanger includes: an inner peripheral wall; an outer peripheral wall; and partition walls disposed between the inner peripheral wall and the outer peripheral wall, the partition walls defining a plurality of cells each extending from a first end face to a second end face. In a cross section orthogonal to an extending direction of the cells, the partition walls include one or more first partition walls extending in a radial direction. The inner peripheral wall has an inner diameter of more than 50 mm and 75 mm or less, and the outer peripheral wall has an outer diameter of 60 to 100 mm. The honeycomb structure for a heat exchanger has an opening ratio of 0.15 or more.

Description

FIELD OF THE INVENTION

The present invention relates to a honeycomb structure for a heat exchanger, and a heat exchanger.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention claims the benefit of priority to Japanese Patent Application No 2023-042190 filed on Mar. 16, 2023 with the Japanese Patent Office, the entire contents of which are incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Recently, there is a need for improvement of fuel economy of motor vehicles. In particular, a system is expected that worms up a coolant, engine oil and an automatic transmission fluid (ATF: Automatic Transmission Fluid) at an early stage to reduce friction losses, in order to prevent deterioration of fuel economy at the time when an engine is cold, such as when the engine is started. Further, a system is expected that heats an exhaust gas purifying catalyst in order to activate the catalyst at an early stage.

As one of the systems as described above, for example, there is a heat exchanger. The heat exchanger is a device that exchanges heat between a first fluid and a second fluid by allowing the first fluid to flow inside and the second fluid to flow outside. In such a heat exchanger, for example, the heat can be effectively utilized by exchanging the heat from the first fluid having a higher temperature (for example, an exhaust gas) to the second fluid having a lower temperature (for example, cooling water).

A heat exchanger that uses a heat exchange member having a honeycomb structure has been proposed as the heat exchanger for recovering heat from high-temperature gases such as exhaust gases from motor vehicles. A heat exchanger member having a hollow honeycomb structure including a hollow region that functions as a bypass route for an exhaust gas has also been proposed.

For example, Patent Literature 1 proposes a heat exchange member including: a hollow honeycomb structure having partition walls defining cells each extending from a first end face to a second end face to form a flow path for a first fluid, an inner peripheral wall, and an outer peripheral wall; and a covering member for covering the outer peripheral wall of the honeycomb structure, wherein in a cross section of the honeycomb structure orthogonal to a flow path direction for the first fluid, the cells are radially provided, and the inner peripheral wall and the outer peripheral wall have thicknesses greater than those of the partition walls, and it also proposes a heat exchanger using the heat exchange member.

The hollow honeycomb structure of Patent Literature 1 has partition walls extending in the radial direction and partition walls extending in the circumferential direction in order to provide cells radially. An increase in the number of the partition walls extending in the circumferential direction increases an amount of heat recovery, while it also increases the pressure loss of the first fluid flowing through the cells. Further, an increase in the thickness of the partition walls extending in the radial direction increases the amount of heat recovery, while it also increases the pressure loss of the first fluid flowing through the cells. Thus, there is a trade-off relationship between the increase in the amount of heat recovery and the suppression of the pressure loss, and there is still room for improvement in terms of achieving a good balance between the increase in the amount of heat recovery and the suppression of the pressure loss.

The present invention has been made to solve the problems as described above. An object of the present invention is to provide a honeycomb structure for a heat exchanger that can increase the amount of heat recovery while suppressing the pressure loss, and a heat exchanger using the same.

PRIOR ART

Patent Literature

• • [Patent Literature 1] WO 2019/135312 A1

SUMMARY OF THE INVENTION

As a result of intensive studies for hollow honeycomb structures for heat exchangers, which have partition walls extending in the radial direction and partition walls extending in the circumferential direction in a cross section orthogonal to an extending direction of cells, the present inventors have found that the above problems can be solved by controlling the inner diameter of the inner peripheral wall, the outer diameter of the outer peripheral wall, and the opening ratio to predetermined ranges, and they have completed the present invention. That is, the present invention is illustrated as follows:

[1]

A honeycomb structure for a heat exchanger, the honeycomb structure comprising: an inner peripheral wall; an outer peripheral wall; and partition walls disposed between the inner peripheral wall and the outer peripheral wall, the partition walls defining a plurality of cells each extending from a first end face to a second end face,

wherein, in a cross section orthogonal to an extending direction of the cells, the partition walls comprise one or more first partition walls extending in a radial direction, the inner peripheral wall has an inner diameter of more than 50 mm and 75 mm or less, and the outer peripheral wall has an outer diameter of 60 to 100 mm, and

wherein the honeycomb structure has an opening ratio of 0.15 or more.

[2]

The honeycomb structure for a heat exchanger according to [1], wherein the partition walls further comprise one or more second partition walls extending in a circumferential direction in a cross section orthogonal to an extending direction of the cells.

[3]

The honeycomb structure for a heat exchanger according to [1] or [2], wherein the opening ratio is 0.30 or more.

[4]

The honeycomb structure for a heat exchanger according to any one of [1] to [3], wherein the opening ratio is 0.60 or less.

[5]

A heat exchanger comprising the honeycomb structure for a heat exchanger according to any one of [1] to [4].

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a honeycomb structure for a heat exchanger according to an embodiment of the present invention, which is orthogonal to an extending direction of cells;

FIG. 2 is a cross-sectional view of a honeycomb structure for a heat exchanger according to an embodiment of the present invention, which is parallel to an extending direction of cells;

FIG. 3A is a graph showing a relationship between an opening ratio and an amount of heat recovery per unit area of a honeycomb structure in which an inner peripheral wall has an inner diameter of 60 mm and an outer peripheral wall has an outer diameter of 80 mm;

FIG. 3B is a graph showing a relationship between an opening ratio and a pressure loss of a honeycomb structure in which an inner peripheral wall has an inner diameter of 60 mm and an outer peripheral wall has an outer diameter of 80 mm;

FIG. 4A is a graph showing a relationship between an opening ratio and an amount of heat recovery per unit area of a honeycomb structure in which an inner peripheral wall has an inner diameter of 70 mm and an outer peripheral wall has an outer diameter of 90 mm;

FIG. 4B is a graph showing a relationship between an opening ratio and a pressure loss of a honeycomb structure in which an inner peripheral wall has an inner diameter of 70 mm and an outer peripheral wall has an outer diameter of 90 mm;

FIG. 5A is a graph showing a relationship between an opening ratio and an amount of heat recovery per unit area of a honeycomb structure in which an inner peripheral wall has an inner diameter of 60 mm and an outer peripheral wall has an outer diameter of 90 mm;

FIG. 5B is a graph showing a relationship between an opening ratio and a pressure loss of a honeycomb structure in which an inner peripheral wall has an inner diameter of 60 mm and an outer peripheral wall has an outer diameter of 90 mm; and

FIG. 6 is a cross-sectional view of a heat exchanger according to an embodiment of the present invention, which is parallel to an extending direction of cells.

DETAILED DESCRIPTION OF THE INVENTION

A honeycomb structure for a heat exchanger according to an embodiment of the present invention includes: an inner peripheral wall; an outer peripheral wall; and partition walls disposed between the inner peripheral wall and the outer peripheral wall, the partition walls defining a plurality of cells each extending from a first end face to a second end face. Also, in a cross section orthogonal to an extending direction of the cells, the partition walls include one or more first partition walls extending in a radial direction. The inner peripheral wall has an inner diameter of more than 50 mm and 75 mm or less, and the outer peripheral wall has an outer diameter of 60 to 100 mm, and the opening ratio is 0.15 or more. Such a structure allows an amount of heat recovery to be increased while suppressing the pressure loss.

A heat exchanger according to an embodiment of the present invention includes the above honeycomb structure for a heat exchanger. Since this heat exchanger includes the honeycomb structure for a heat exchanger that can increase the amount of heat recovery while suppressing the pressure loss, the performance as a heat exchanger can be improved.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. It is to understand that the present invention is not limited to the following embodiments, and those which appropriately added changes, improvements and the like to the following embodiments based on knowledge of a person skilled in the art without departing from the spirit of the present invention fall within the scope of the present invention.

<Honeycomb Structure for Heat Exchanger>

The honeycomb structure for a heat exchanger according to an embodiment of the present invention is a honeycomb structure used for a heat exchanger.

FIG. 1 is a cross-sectional view of a honeycomb structure for a heat exchanger (hereinafter, abbreviated as a “honeycomb structure”) according to an embodiment of the present invention, which is orthogonal to an extending direction of cells, and FIG. 2 is a cross-sectional view of a honeycomb structure for a heat exchanger according to an embodiment of the present invention, which is parallel to an extending direction of cells.

As shown in FIGS. 1 and 2, the honeycomb structure 10 includes: an inner peripheral wall 11; an outer peripheral wall 12; and partition walls 15 that are disposed between the inner peripheral wall 11 and the outer peripheral wall 12, and define a plurality of cells 14 each extending from a first end face 13a to a second end face 13b. In a cross section (FIG. 1) orthogonal to the extending direction of the cells 14 of the honeycomb structure 10, the partition walls 15 include one or more first partition walls 15a extending in a radial direction. The partition walls 15 may further include one or more second partition walls 15b extending in a circumferential direction in a cross section orthogonal to the extending direction of the cells 14. It should be noted that although FIGS. 1 and 2 show an example in which the partition walls 15 include the second partition walls 15b, the second partition walls 15b may not be included.

In the honeycomb structure 10 having the above structure, a fluid can flow through the cells 14. The fluid is not particularly limited, and various liquids or gases may be used. For example, when the honeycomb structure 10 is used in a heat exchanger mounted on a motor vehicle, the fluid is preferably an exhaust gas.

Moreover, since the honeycomb structure 10 has one or more first partition walls 15a extending in the radial direction, the heat of the fluid can be efficiently transmitted to the outer peripheral wall 12 via the first partition walls 15a.

A shape (an outer shape) of the honeycomb structure 10 may be, but not limited to, for example, a circular pillar shape, an elliptic pillar shape, a quadrangular pillar shape or other polygonal pillar shape. Thus, the outer shape of the honeycomb structure 10 (i.e., the outer shape of the outer peripheral wall 12) in the cross section in FIG. 1 may be circular, elliptical, quadrangular or other polygonal.

Also, a shape of a hollow region in the honeycomb structure 10 may be, but not limited to, for example, a circular pillar shape, an elliptic pillar shape, a quadrangular pillar shape or other polygonal pillar shape. Thus, the shape of the hollow region (i.e., the inner shape of the inner peripheral wall 11) in the cross section in FIG. 1 may be circular, elliptical, quadrangular or other polygonal.

Although the shapes of the honeycomb structure 10 and the hollow region may be the same as or different from each other, it is preferable that they are the same as each other, in terms of ensuring the strength.

The inner diameter of the inner peripheral wall 11 (the inner diameter of the inner peripheral wall 11 in a cross section orthogonal to the extending direction of the cells 14) is more than 50 mm and 75 mm or less, and preferably from 55 to 70 mm. By controlling the inner diameter of the inner peripheral wall 11 to such a range, the honeycomb structure 10 can be made compact while achieving both an increase in the amount of heat recovery and suppression of the pressure loss.

It should be noted that when the cross-sectional shape of the inner peripheral wall 11 is not circular, the diameter of the largest inscribed circle inscribed in the cross-sectional shape of the inner peripheral wall 11 is defined as the inner diameter of the inner peripheral wall 11.

The outer diameter of the outer peripheral wall 12 (the outer diameter of the outer peripheral wall 12 in a cross section orthogonal to the extending direction of the cells 14) is 60 to 100 mm, and preferably 70 to 90 mm. By controlling the outer diameter of the outer peripheral wall 12 to such a range, the honeycomb structure 10 can be made compact while achieving both the increase in the amount of heat recovery and the suppression of the pressure loss.

It should be noted that when the shape of the outer peripheral wall 12 is not circular, the diameter of the largest inscribed circle inscribed in the cross-sectional shape of the outer peripheral wall 12 is defined as the outer diameter of the outer peripheral wall 12.

The opening ratio of the honeycomb structure 10 is 0.15 or more, and preferably 0.20 or more, and more preferably 0.25 or more, and still more preferably 0.30 or more. By controlling the opening ratio to such a range, it is possible to achieve both the increase in the amount of heat recovery and the suppression of the pressure loss.

Further, the upper limit of the opening ratio of the honeycomb structure 10 is preferably 0.60 or less, and more preferably 0.55 or less, and even more preferably 0.50 or less, from the viewpoint of ensuring the strength of the honeycomb structure 10, although not particularly limited thereto.

As used herein, the opening ratio of the honeycomb structure 10 refers to a value obtained by dividing the total area of the cells 14 defined by the partition walls 15 by an area (the total area of the inner peripheral wall 11, the outer peripheral wall 12, the partition walls 15, and cells 14) of one end face (the first end face 13a or the second end face 13b), in a cross section orthogonal to the extending direction of the cells 14.

FIG. 3A is a graph showing the relationship between the opening ratio and the amount of heat recovery per unit area of the honeycomb structure 10 in which the inner peripheral wall 11 has an inner diameter of 60 mm and the outer peripheral wall 12 has an outer diameter of 80 mm. Moreover, FIG. 3B is a graph showing the relationship between the opening ratio and the pressure loss of this honeycomb structure 10.

In FIGS. 3A and 3B, three types of samples with different average thicknesses of the partition walls 15 (the first partition walls 15a and the second partition walls 15b) were evaluated. The symbol a represents a case where the average thickness of the partition walls 15 (the first partition walls 15a and the second partition walls 15b) is larger, the symbol b represents a case where the average thickness of the partition walls 15 is medium, and the symbol c represents a case where the average thickness of the partition walls 15 is smaller.

As shown in FIG. 3A, as the opening ratio decreases, the amount of heat recovery increases, but there was a tendency for the amount of heat recovery to decrease even if the opening ratio excessively decreased. This tendency is particularly noticeable when the opening ratio is less than 0.15. This is because, as shown in FIG. 3B, when the opening ratio is less than 0.15, the pressure loss increases significantly. When the opening ratio is 0.15 or more, the amount of heat recovery can be increased while suppressing the pressure loss to an acceptable level. In particular, when the opening ratio is 0.30 or more, the amount of heat recovery can be increased while sufficiently suppressing the pressure loss.

All of the honeycomb structures 10 used in the above evaluation were produced according to a known method, and the material was Si-impregnated SiC. Further, the length in the extending direction of the cells 14 was 20 to 200 mm, the average thickness of the inner peripheral wall 11 was 1.5 mm, the average thickness of the outer peripheral wall 12 was 1.5 mm, and the number of the first partition walls 15a was 200 to 400, and the number of the second partition walls 15b was 2 to 4.

The amount of heat recovery was evaluated in the following manner by producing the heat exchanger 100 of FIG. 6 described below. First, air (first fluid) at 400° C. (Tg1) is fed to the cells 14 of the honeycomb structure 10 at a flow rate of 10 g/see (Mg), and water (second fluid) is fed to the outer peripheral side of the honeycomb structure 10 at a flow rate of 166 g/see (Mw) to recover the water. Under each of the above conditions, the feed of the air and the water to the heat exchanger 100 is started, and after reaching a steady state, a temperature (Tw1) of the water in a feed pipe 62 provided in a second outer cylinder member 60 and a temperature (Tw2) of the water in a discharge pipe were measured, and an amount of heat recovered by the water (heat recovery amount Q) was determined. The heat recovery amount Q was determined by division by the volume of the honeycomb structure 10 to calculate the amount of heat recovery per unit volume. It should be noted that the heat recovery amount Q is expressed by the following equation:

$Q\left(\mathrm{kW}\right)=\Delta \mathrm{Tw}\times \mathrm{Cpw}\times \mathrm{Mw}$

In the above equation, ΔTw=Tw2-Tw1, Cpw (specific heat of water)=4182J/(kg·K).

The pressure loss was evaluated in the following manner by producing a heat exchanger 100 shown in FIG. 6 described below. First, a heat exchange test was conducted by feeding the air (first fluid) at 400° C. (Tg1) at a flow rate of 20 g/see (Mg) while closing an on-off valve 70, and also feeding the water (second fluid) from the feed pipe 62 at a flow rate of 166 g/see (Mw) to recover the water from the discharge pipe. In this heat exchange test, pressure gauges were placed on the upstream and downstream sides of the honeycomb structure 10 to measure the pressure. The pressure drop was calculated based on the following equation:

$\mathrm{Pressure}\mathrm{loss}=\mathrm{Py}-\mathrm{Pz}$

In the equation, Py is the pressure on the upstream side of the honeycomb structure 10, and Pz is the pressure on the downstream side of the honeycomb structure 10.

FIG. 4A is a graph showing the relationship between the opening ratio and the amount of heat recovery per unit area of the honeycomb structure 10 in which the inner peripheral wall 11 has an inner diameter of 70 mm and the outer peripheral wall 12 has an outer diameter of 90 mm. Moreover, FIG. 4B is a graph showing the relationship between the opening ratio and the pressure loss of this honeycomb structure 10. It should be noted that in FIGS. 4A and 4B, each of the symbols a to c means the average thickness of the partition walls 15 described in each of FIGS. 3A and 3B.

As shown in FIG. 4A, even in the honeycomb structure 10 having this size, as the opening ratio decreases, the amount of heat recovery amount increases, but there was a tendency for the amount of heat recovery to decrease even if the opening ratio was too low. This is because, as shown in FIG. 4B, when the opening ratio is less than 0.15, the pressure loss increases significantly. When the opening ratio is 0.15 or more, the amount of heat recovery can be increased while suppressing the pressure loss to an acceptable level. In particular, when the opening ratio is 0.30 or more, the amount of heat recovery can be increased while sufficiently suppressing the pressure loss.

It should be noted that the honeycomb structure 10 used in the above evaluation was the same as the honeycomb structure 10 used in the evaluations of FIGS. 3A and 3B, with the exception that the inner diameter of the inner peripheral wall 11 and the outer diameter of the outer peripheral wall 12 were different. Furthermore, the evaluation methods for the amount of heat recovery amount and the pressure loss were also the same.

FIG. 5A is a graph showing the relationship between the opening ratio and the amount of heat recovery per unit area of the honeycomb structure 10 in which the inner peripheral wall 11 has an inner diameter of 60 mm and the outer peripheral wall 12 has an outer diameter of 90 mm. Moreover, FIG. 5B is a graph showing the relationship between the opening ratio and the pressure loss of this honeycomb structure 10. It should be noted that in FIGS. 5A and 5B, each of the symbols a to c means the average thickness of the partition walls 15 described in each of FIGS. 3A and 3B.

As shown in FIG. 5A, even in the honeycomb structure 10 having this size, as the opening ratio decreases, the amount of heat recovery amount increases, but there was a tendency for the amount of heat recovery to decrease even if the opening ratio was too low. This is because, as shown in FIG. 5B, when the opening ratio is less than 0.15, the pressure loss increases significantly. When the opening ratio is 0.15 or more, the amount of heat recovery can be increased while suppressing the pressure loss to an acceptable level. In particular, when the opening ratio is 0.30 or more, the amount of heat recovery can be increased while sufficiently suppressing the pressure loss.

It should be noted that the honeycomb structure 10 used in the above evaluation was the same as the honeycomb structure 10 used in the evaluations of FIGS. 3A and 3B, with the exception that the inner diameter of the inner peripheral wall 11 and the outer diameter of the outer peripheral wall 12 were different. Furthermore, the evaluation methods for the amount of heat recovery amount and the pressure loss were also the same.

The length of the honeycomb structure 10 in the extending direction of the cells 14 is preferably 10 to 300 mm, and more preferably 20 to 200 mm. By controlling the length in the extending direction of the cells 14 to such a range, it becomes easier to achieve both the increase in the amount of heat recovery and the suppression of the pressure loss while achieving compactness.

Here, the length in the extending direction of the cells 14 is a length from the first end face 13a to the second end face 13b in the cross section parallel to the extending direction of the cells 14.

In the honeycomb structure 10, the inner peripheral wall 11 preferably has an average thickness of 0.1 to 10 mm, and more preferably 0.5 to 3 mm. By controlling the average thickness of the inner peripheral wall 11 to such a range, it becomes easier to achieve both the increase in the amount of heat recovery and the suppression of the pressure loss.

As used herein, the average thickness of the inner peripheral wall 11 is an average value of the thickness of the inner peripheral wall 11 in a cross section orthogonal to the extending direction of the cells 14. The average thickness of the inner peripheral wall 11 can be determined by measuring the thickness of the inner peripheral wall 11 in at least eight arbitrary positions and calculating an average value thereof.

In the honeycomb structure 10, the average thickness of the outer peripheral wall 12 may preferably be 0.1 to 10 mm, and more preferably 0.5 to 3 mm. By controlling the average thickness of the outer peripheral wall 12 to such a range, it becomes easier to achieve both the increase in the amount of heat recovery and the suppression of the pressure loss.

Here, the average thickness of the outer peripheral wall 12 is an average value of the thickness of the outer peripheral wall 12 in the cross section orthogonal to the extending direction of the cells 14. The average thickness of the outer peripheral wall 12 can be determined by measuring the thickness of the outer peripheral wall 12 in at least eight arbitrary positions and calculating an average value thereof.

The average thickness of the first partition walls 15a of the honeycomb structure 10 may preferably be 0.1 to 1 mm, and more preferably 0.2 to 0.6 mm. By controlling the average thickness of the first partition walls 15a to such a range, it becomes easier to achieve both the increase in the amount of heat recovery and the suppression of the pressure loss.

Here, the average thickness of the first partition walls 15a is an average value of the thicknesses of the first partition walls 15a in the cross section orthogonal to the extending direction of the cells 14. The average thickness of the first partition walls 15a can be obtained by measuring the thicknesses of the first partition walls 15a in at least eight arbitrary positions and calculating an average value thereof.

The number of the first partition walls 15a of the honeycomb structure 10 may preferably be 50 to 1,500, and more preferably 100 to 1,000. By controlling the number of the first partition walls 15a to such a range, it becomes easier to achieve both the increase in the amount of heat recovery and the suppression of the pressure loss.

Here, the number of the first partition walls 15a is calculated by considering the partition walls 15 extending in the radial direction from the inner peripheral wall 11 to the outer peripheral wall 12 as one first partition wall 15a in a cross section orthogonal to the extending direction of the cells 14.

The average thickness of the second partition walls 15b of the honeycomb structure 10 may preferably be 0.1 to 1 mm, and more preferably 0.2 to 0.6 mm. By controlling the average thickness of the second partition walls 15b to such a range, it becomes easier to achieve both the increase in the amount of heat recovery and the suppression of the pressure loss.

Here, the average thickness of the second partition walls 15b is an average value of the thicknesses of the second partition walls 15b in the cross section orthogonal to the extending direction of the cells 14. The average thickness of the second partition walls 15b can be obtained by measuring the thicknesses of the second partition walls 15b in at least eight arbitrary positions and calculating an average value thereof.

The number of the second partition walls 15b of the honeycomb structure 10 may preferably be 50 or less, and more preferably 1 to 25. By controlling the number of the second partition walls 15b to such a range, it becomes easier to achieve both the increase in the amount of heat recovery and the suppression of the pressure loss.

Here, the number of the second partition walls 15b is calculated by considering the annular partition walls 15 extending in the circumferential direction as one second partition wall 15b in the cross section orthogonal to the extending direction of the cells 14.

The inner peripheral wall 11, the outer peripheral wall 12 and the partition walls 18 preferably contain ceramics as a main component. The phrase “contain ceramics as a main component” means that a ratio of a mass of ceramics to a mass of the total component is 50% by mass or more.

Each of the inner peripheral wall 11, the outer peripheral wall 12 and the partition walls 15 preferably has a porosity of 10% or less, and more preferably 5% or less, and even more preferably 3% or less. Further, the porosity of the inner peripheral wall 11, the outer peripheral wall 12 and the partition walls 15 may be 0%. The porosity of the inner peripheral wall 11, the outer peripheral wall 12 and the partition walls 15 of 10% or less can lead to improvement of thermal conductivity, thereby increasing the amount of heat recovery.

The inner peripheral wall 11, the outer peripheral wall 12 and partition walls 15 preferably contain SiC (silicon carbide) having high thermal conductivity as a main component. The phrase “contain SiC (silicon carbide) as a main component” means that a mass ratio of SiC (silicon carbide) to the total component is 50% by mass or more.

Specific examples of materials for the inner peripheral wall 11, the outer peripheral wall 12 and partition walls 15 include Si-impregnated SiC, (Si+Al) impregnated SiC, a metal composite SiC, recrystallized SiC, Si₃N₄, SiC, and the like. Among them, Si-impregnated SiC and (Si+Al) impregnated SiC are preferably used because they can allow production at lower cost and have high thermal conductivity.

The honeycomb structure 10 preferably has a thermal conductivity of 50 W/(m·K) or more at 25° C., and more preferably from 100 to 300 W/(m·K), and even more preferably from 120 to 300 W/(m K). The thermal conductivity of the honeycomb structure 10 in such a range can lead to an improved thermal conductivity and can allow the heat inside the honeycomb structure 10 to be efficiently transmitted to the outside. It should be noted that the value of thermal conductivity is a value measured according to the laser flash method (JIS R 1611: 1997).

In the case where an exhaust gas as the first fluid flows through the cells 14 in the honeycomb structure 10, a catalyst may preferably be supported on the partition walls 15 of the honeycomb structure 10. The supporting of the catalyst on the partition walls 15 can allow CO, NOx, HC and the like in the exhaust gas to be converted into harmless substances through catalytic reaction, and can also allow reaction heat generated during the catalytic reaction to be utilized for heat exchange. Preferable catalysts include those containing at least one element selected from the group consisting of noble metals (platinum, rhodium, palladium, ruthenium, indium, silver and gold), aluminum, nickel, zirconium, titanium, cerium, cobalt, manganese, zinc, copper, tin, iron, niobium, magnesium, lanthanum, samarium, bismuth, and barium. Any of the above-listed elements may be contained as a metal simple substance, a metal oxide, or other metal compound.

A supported amount of the catalyst (catalyst metal+support) may preferably be from 10 to 400 g/L. Further, when using the catalyst containing the noble metal(s), the supported amount may preferably be from 0.1 to 5 g/L. The supported amount of the catalyst (catalyst metal+support) of 10 g/L or more can easily achieve catalysis. On the other hand, the supported amount of 400 g/L or less can suppress increases in manufacturing cost and pressure loss. The support refers to a carrier on which the catalyst metal is supported. Examples of the supports include those containing at least one selected from the group consisting of alumina, ceria and zirconia.

The honeycomb structure 10 according to the embodiment of the present invention can be produced according to known methods. First, a green body containing ceramic powder is extruded into a desired shape to prepare a honeycomb formed body. At this time, the average thickness and the inner diameter of the inner peripheral wall 11, the average thickness and the outer diameter of the outer peripheral wall 12, the average thickness and the number of the partition walls 15 (the first partition walls 15a and the second partition walls 15b), and the like, can be controlled by selecting dies and jig in appropriate forms. For example, when producing a honeycomb formed body based on a Si-impregnated SiC composite, a binder and water or an organic solvent are added to a predetermined amount of SiC powder, and the resulting mixture is kneaded to form a green body, which is formed into a honeycomb formed body having a desired shape. The resulting honeycomb formed body can be then dried, and the honeycomb formed body can be impregnated with metal Si and fired under reduced pressure in an inert gas or vacuum to obtain the honeycomb structure 10.

<Heat Exchanger>

FIG. 6 is a cross-sectional view of a heat exchanger according to an embodiment of the present invention which is parallel to the extending direction of the cells.

As shown in FIG. 6, a heat exchanger 100 according to an embodiment of the present invention includes: the honeycomb structure 10; a first outer cylindrical member 20; a first inner cylindrical member 30; a second inner cylindrical member 40; a tubular member 50; a second outer cylindrical member 60; an on-off valve 70; and a ring-shaped member 80. In this heat exchanger 100, the first fluid flows through a region on an inner side than the first outer cylindrical member 20 (for example, the cells 14 of the honeycomb structure 10, and the like), and the second fluid flows through a region on an outer side than the first outer cylindrical member 20 (between the first outer cylindrical member 20 and the second outer cylindrical member 60).

In the heat exchanger 100, the end portion of the first inner cylindrical member 30 on the side of an inflow port 31a is joined to the first outer cylindrical member 20 and/or the second inner cylindrical member 40, so that at least one through hole 32 for introducing the first fluid is provided on the upstream side of the first end face 13a of the honeycomb structure 10. Also, an outflow port 41b of the second inner cylindrical member 40 is positioned on a radially inner side of the first inner cylindrical member 30, and on the upstream side of a downstream end portion 33 of the through hole 32 of the first inner cylindrical member 30 based on a flow direction D1 of the first fluid as a reference.

The structure as described above can prevent the flow of the first fluid (exhaust gas) that has flowed out through the outflow port 41b of the second inner cylindrical member 40 from being turned back during the heat recovery mode. Therefore, during the heat recovery mode, an increase in pressure loss (flow path resistance) can be sufficiently suppressed, so that damage or bursting of the heat exchanger 100 is difficult to occur. Moreover, the length of the second inner cylindrical member 40 can be shortened, so that the weight of the heat exchanger 100 and the production cost can be reduced. Further, the diameter of the outflow port 41b of the second inner cylindrical member 40 is smaller than that of the first inner cylindrical member 30, so that the first fluid that has flowed out through the outflow port 41b of the second inner cylindrical member 40 is difficult to pass through the through hole 32 during the non-heat recovery mode and tends to flow smoothly through the first inner cylindrical member 30. Therefore, the heat will be difficult to be transferred to the honeycomb structure 10, so that the heat shielding performance can be improved.

In the heat exchanger 100, based on the flow direction D1 of the first fluid as a reference, the central portion of the axial length of the honeycomb structure 10 is positioned on the downstream side of the central portion of the first outer cylindrical member 20 and the second outer cylindrical member 60. The first end face 13a of the honeycomb structure 10 is aligned at the same position as the downstream end portion 33 of the through hole 32 provided in the first inner cylindrical member 30, and the upstream end portion of the through hole 32 is aligned at the same position as a position of a downstream end portion of the ring-shaped member 80. Therefore, the through hole 32 can be provided so as to be long in the axial direction of the first inner cylindrical member 30, so that the effect of suppressing the increase in pressure loss (flow path resistance) during the heat recovery mode can be enhanced. Further, the contact area of the first outer cylindrical member 20 with the first fluid at elevated temperature can be increased, so that the heat transfer to the second fluid can be increased to improve the heat exchange efficiency.

In the heat exchanger 100, based on the flow direction D1 of the first fluid as a reference, the position of the downstream end portion of the flow path for the second fluid formed between the first outer cylindrical member 20 and the second outer cylindrical member 60 and the position of the second end face 13b of the honeycomb structure 10 are aligned with each other, so that the heat exchange performance during the heat recovery mode is sufficiently ensured.

Further, in the heat exchanger 100, a feed pipe 62 and a discharge pipe (not shown) are arranged in the circumferential direction orthogonal to the axial direction of the second outer cylindrical member 60. By thus providing the feed pipe 62 and the discharge pipe, parts such as an actuator for the on-off valve 70 are easily installed on the surface of the second outer cylindrical member 60 between the feed pipe 62 and the discharge pipe while sufficiently ensuring the heat exchange performance during the heat recovery mode, so that the heat exchanger 200 can be made compact.

The first outer cylindrical member 20 is a cylindrical member that has an inflow port 21a and an outflow port 21b for the first fluid and is fitted to an outer peripheral wall 12 surface of the honeycomb structure 10.

As used herein, the “fitted” means that members are fixed in a state of being suited to each other. Therefore, the fitting of the honeycomb structure 10 and the first outer cylindrical member 20 encompasses cases where the honeycomb structure 10 and the first outer cylindrical member 20 are fixed to each other by a fixing method based on fitting such as clearance fitting, interference fitting and shrinkage fitting, as well as by brazing, welding, diffusion bonding, and the like.

It is preferable that the axial direction of the first outer cylindrical member 20 coincides with the axial direction of the honeycomb structure 10, and the central axis of the first outer cylindrical member 20 coincides with the central axis of the honeycomb structure 10.

Also, the diameter (outer diameter and inner diameter) of the first outer cylindrical member 20 may be uniform in the axial direction, but the diameter of at least a portion (for example, at least one end side in the axial direction or the like) may be decreased or increased.

The first outer cylindrical member 20 may preferably have an inner surface shape corresponding to the outer peripheral wall 12 surface of the honeycomb structure 10. Since the inner surface of the first outer cylindrical member 20 is in direct contact with the outer peripheral wall 12 surface of the honeycomb structure 10, the thermal conductivity is improved and the heat in the honeycomb structure 10 can be efficiently transferred to the first outer cylindrical member 20.

In terms of improvement of the heat recovery efficiency, a higher ratio of an area of a portion of the outer peripheral wall 12 surface of the honeycomb structure 10, which is circumferentially covered with the first outer cylindrical member 20, to the total area of the outer peripheral wall 12 surface of the honeycomb structure 10 is preferable. Specifically, the area ratio is preferably 80% or more, and more preferably 90% or more, and even more preferably 100% (that is, the entire outer peripheral wall 12 surface of the honeycomb structure 10 is circumferentially covered with the first outer cylindrical member 20).

It should be noted that the term “the outer peripheral wall 12 surface” as used herein refers to a surface of the honeycomb structure 10, which is parallel to the flow path direction of the first fluid, and does not include surfaces (the first end face 13a and the second end face 13b) of the honeycomb structure 10, which are perpendicular to the flow path direction of the first fluid.

The first outer cylindrical member 20 is preferably made of a metal in terms of manufacturability, although not particularly limited thereto. Further, the metallic first outer cylindrical member 20 is also preferable in that it can be easily welded to other members such as a second inner cylindrical member 70. Examples of the material of the first outer cylindrical member 20 that can be used herein include stainless steel, titanium alloys, copper alloys, aluminum alloys, brass and the like. Among them, the stainless steel is preferable because it has high durability and reliability and is inexpensive.

The first outer cylindrical member 20 preferably has a thickness of 0.1 mm or more, and more preferably 0.3 mm or more, and still more preferably 0.5 mm or more, although not particularly limited thereto. The thickness of the first outer cylindrical member 20 of 0.1 mm or more can ensure durability and reliability. The thickness of the first outer cylindrical member 20 is preferably 10 mm or less, and more preferably 5 mm or less, and still more preferably 3 mm or less. The thickness of the first outer cylindrical member 20 of 10 mm or less can reduce thermal resistance and improve thermal conductivity.

The first inner cylindrical member 30 is a cylindrical member that has an inflow port 31a and an outflow port 31b for the first fluid and is fitted to the inner peripheral wall 11 surface of the honeycomb structure 10. Here, the first inner cylindrical member 30 may be directly fitted to the inner peripheral wall 11 surface of the honeycomb structure 10, or may be fitted indirectly via another member such as a seal member.

The axial direction of the first inner cylindrical member 30 preferably coincides with that of the honeycomb structure 10, and the central axis of the first inner cylindrical member 30 preferably coincides with that of the honeycomb structure 10. Also, the diameter (outer diameter and inner diameter) of the first inner cylindrical member 30 may be uniform in the axial direction, but the diameter of at least a portion (e.g., the outflow port 31b side) may be decreased or increased.

The shape of the through hole 32 provided in the first inner cylindrical member 30 is not particularly limited, and various shapes such as circular, elliptical, and quadrangular shapes can be used. Also, the number of through holes 32 is not particularly limited, and a plurality of through holes 32 may be provided in the circumferential direction of the first inner cylindrical member 30 or may be provided in the axial direction of the first inner cylindrical member 30. When the plurality of through holes 32 are provided, the above “downstream end portion 33 of the through hole 32 of the first inner cylindrical member 30” means the downstream end portion 33 of the through hole 32 located on the most downstream side of the first inner cylindrical member 30.

The first inner cylindrical member 30 is preferably made of a metal in terms of manufacturability, although not particularly limited thereto. Examples of the material of the first inner cylindrical member 30 that can be used herein include stainless steel, titanium alloys, copper alloys, aluminum alloys, brass and the like. Among them, the stainless steel is preferable because it has high durability and reliability and is inexpensive.

The first inner cylindrical member 30 preferably has a thickness of 0.1 mm or more, and more preferably 0.3 mm or more, and still more preferably 0.5 mm or more, although not particularly limited thereto. The thickness of the first inner cylindrical member 30 of 0.1 mm or more can ensure durability and reliability. The thickness of the first inner cylindrical member 30 is preferably 10 mm or less, and more preferably 5 mm or less, and still more preferably 3 mm or less. The thickness of the first inner cylindrical member 30 of 10 mm or less can reduce the weight of the heat exchanger 100.

The second inner cylindrical member 40 is a cylindrical member that has an inflow port 41a and an outflow port 41b for the first fluid.

The axial direction of the second inner cylindrical member 40 preferably coincides with that of the honeycomb structure 10, and the central axis of the second inner cylindrical member 40 preferably coincides with that of the honeycomb structure 10. Also, the diameter (outer diameter and inner diameter) of the second inner cylindrical member 40 may be uniform in the axial direction, but the diameter of at least a portion (e.g., the outflow port 41b side or the like) may be decreased or increased.

The inner diameter of the outflow port 41b of the second inner cylindrical member 40 is smaller than that of the inflow port 31a of the first inner cylindrical member 30. By thus controlling the inner diameter of the outflow port 41b of the second inner cylindrical member 40, the first fluid flowing out through the outflow port 41b of the second inner cylindrical member 40 tends to flow smoothly into the first inner cylindrical member 30 during the non-heat recovery mode. Therefore, heat is difficult to be transferred to the honeycomb structure 10, so that the heat shielding performance can be improved.

The second inner cylindrical member 40 preferably has a streamlined structure having a diameter gradually decreasing toward the outflow port 41b. Such a structure can enhance the effect that the first fluid flowing out thought the outflow port 41b of the second inner cylindrical member 40 tends to flow smoothly into the first inner cylindrical member 30 during the non-heat recovery mode. Moreover, the pressure loss when the fluid passes through the second inner cylindrical member 40 can be reduced.

Although the shape of the outflow port 41b of the second inner cylindrical member 40 is not particularly limited, it is preferably polygonal or elliptical. Such a structure can stably enhance the effect that the first fluid flowing out through the outflow port 41b of the second inner cylindrical member 40 tends to flow smoothly into the first inner cylindrical member 30 during the non-heat recovery mode.

A method of fixing the second inner cylindrical member 40 is not particularly limited, but the second inner cylindrical member 40 may be fixed to the first cylindrical member 20, or the second inner cylindrical member 40 may be fixed to a ring-shaped member 80. The fixing method includes, but not limited to, a fixing method by fitting such as clearance fitting, interference fitting and shrinkage fitting, as well as by brazing, welding, diffusion bonding, and the like.

The second inner cylindrical member 40 is preferably made of a metal in terms of manufacturability, although not particularly limited thereto. Examples of the material of the second inner cylindrical member 40 that can be used herein include stainless steel, titanium alloys, copper alloys, aluminum alloys, brass and the like. Among them, the stainless steel is preferable because it has high durability and reliability and is inexpensive.

The second inner cylindrical member 40 preferably has a thickness of 0.1 mm or more, and more preferably 0.3 mm or more, and still more preferably 0.5 mm or more, although not particularly limited thereto. The thickness of the second inner cylindrical member 40 of 0.1 mm or more can ensure durability and reliability. The thickness of the second inner cylindrical member 40 is preferably 10 mm or less, and more preferably 5 mm or less, and still more preferably 3 mm or less. The thickness of the second inner cylindrical member 40 of 10 mm or less can reduce the weight of the heat exchanger 100.

The tubular member 50 is a member connected to the outflow port 21b side of the first outer cylindrical member 20. Further, the tubular member 50 has a portion arranged at a space so as to form the flow path for the first fluid on the radially outer side of the first inner cylindrical member 30.

The connection of the tubular member 50 to the first outer cylindrical member 20 may be either direct or indirect. In the case of indirect connection, for example, the second outer cylindrical member 60 or the like may be arranged between the first outer cylindrical member 20 and the tubular member 50.

The tubular member 50 has an inflow port 51a and an outflow port 51b.

The axial direction of the tubular member 50 preferably coincides with that of the honeycomb structure 10, and the central axis of the tubular member 50 preferably coincides with that of the honeycomb structure 10. Further, the diameter (outer diameter and inner diameter) of the tubular member 50 may be uniform over the axial direction, but the diameter of at least a portion may be decreased or increased.

The tubular member 30 is preferably made of a metal in terms of manufacturability, although not particularly limited thereto. Examples of the material of the tubular member 20 that can be used herein include stainless steel, titanium alloys, copper alloys, aluminum alloys, brass and the like. Among them, the stainless steel is preferable because it has high durability and reliability and is inexpensive.

The tubular member 50 preferably has a thickness of 0.1 mm or more, and more preferably 0.3 mm or more, and still more preferably 0.5 mm or more, although not particularly limited thereto. The thickness of the tubular member 50 of 0.1 mm or more can ensure durability and reliability. The thickness of the tubular member 50 is preferably 10 mm or less, and more preferably 5 mm or less, and still more preferably 3 mm or less. The thickness of the tubular member 50 of 10 mm or less can reduce the weight of the heat exchanger 100.

The second outer cylindrical member 60 is a cylindrical member arranged at a space on a radially outer side of the first outer cylindrical member 20. A second fluid can flow between the second outer cylindrical member 60 and the first outer cylindrical member 20.

The second outer cylindrical member 60 has an inflow port 61a and an outflow port 61b.

The axial direction of the second outer cylindrical member 60 preferably coincides with that of the honeycomb structure 10 and the central axis of the second outer cylindrical member 60 preferably coincides with that of the honeycomb structure 10.

The second outer cylindrical member 60 is preferably connected to both a feed pipe 62 for feeding the second fluid to a region between the second outer cylindrical member 60 and the first outer cylindrical member 20, and a discharge pipe for discharging the second fluid from a region between the second outer cylindrical member 60 and the first outer cylindrical member 20. The feed pipe 62 and the discharge pipe are preferably provided at positions corresponding to both axial end portions of the honeycomb structure 10, respectively.

The feed pipe 62 and the discharge pipe may extend in the same direction, or may extend in different directions.

The second outer cylindrical member 60 is preferably arranged such that inner peripheral surfaces of both end portions in the axial direction are in direct or indirect contact with the outer peripheral surface of the first outer cylindrical member 20.

A method of fixing the inner peripheral surfaces of both end portions in the axial direction to the outer peripheral surface of the first outer cylindrical member 20 that can be used herein includes, but not limited to, a fixing method by fitting such as clearance fitting, interference fitting and shrinkage fitting, as well as by brazing, welding, diffusion bonding, and the like.

The diameter (outer diameter and inner diameter) of the second outer cylindrical member 60 may be uniform in the axial direction, but the diameter of at least a portion (for example, a central portion in the axial direction, both ends in the axial direction, or the like) of the second outer cylindrical member 60 may be decreased or increased. For example, by decreasing the diameter of the central portion in the axial direction of the second outer cylindrical member 60, the second fluid can spread throughout the outer peripheral direction of the first outer cylindrical member 20 in the second outer cylindrical member 60 on the feed pipe 62 and discharge pipe sides. Therefore, an amount of the second fluid that does not contribute to the heat exchange at the central portion in the axial direction is reduced, so that the heat exchange efficiency can be improved.

The second outer cylindrical member 60 is preferably made of a metal in terms of manufacturability, although not particularly limited thereto. Examples of the material of the second outer cylindrical member 60 that can be used herein include stainless steel, titanium alloys, copper alloys, aluminum alloys, brass and the like. Among them, the stainless steel is preferable because it has high durability and reliability and is inexpensive.

The second outer cylindrical member 60 preferably has a thickness of 0.1 mm or more, and more preferably 0.3 mm or more, and still more preferably 0.5 mm or more, although not particularly limited thereto. The thickness of the second outer cylindrical member 60 of 0.1 mm or more can ensure durability and reliability. The thickness of the second outer cylindrical member 60 is preferably 10 mm or less, and more preferably 5 mm or less, and still more preferably 3 mm or less. The thickness of the second outer cylindrical member 60 of 10 mm or less can reduce the weight of the heat exchanger 100.

The on-off valve 70 is arranged on the outflow port 31b side of the inner cylindrical member 30.

The on-off valve 70 is rotatably supported by a bearing 71 arranged on a radially outer side of the tubular member 50, and is fixed to a shaft 72 arranged so as to penetrate the tubular member 50 and the inner cylindrical member 30.

The shape of the on-off valve 70 is not particularly limited, but it may be appropriately selected depending on the shape of the inner cylindrical member 30 in which the on-off valve 70 is to be arranged.

The on-off valve 70 can drive (rotate) the shaft 72 by an actuator (not shown). The on-off valve 70 can be opened and closed by rotating the on-off valve 70 together with the shaft 72.

The on-off valve 70 is configured so that the flow of the first fluid inside the inner cylindrical member 30 can be controlled. More particularly, by closing the on-off valve 70 during the heat recovery mode, the first fluid can be circulated through the honeycomb structure 10. Further, by opening the on-off valve 70 during the non-heat recovery mode, the first fluid can be circulated from the outflow port 31b side of the inner cylindrical member 30 to the tubular member 50 to discharge the first fluid to the outside of the heat exchanger 100.

The ring-shaped member 80 is a cylindrical member for connecting the inflow port 21a side of the first outer cylindrical member 20 to the second inner cylindrical member 40 so as to form the flow path for the first fluid. The connection position of the second inner cylindrical member 40 to which the ring-shaped member 80 is connected is not particularly limited, and it may be on the inflow port 41a side, on the outflow port 41b side, or near the central portion of the second inner cylindrical member 40, but it may preferably be such that the distance between the inflow port 41a of the second inner cylindrical member 40 and the inflow port 21a of the first outer cylindrical member 20 in the flow direction D1 of the first fluid is preferably 20 mm or less, and more preferably 1 to 15 mm, and more preferably 5 to 10 mm. The reason is as described above.

The connection of the first outer cylindrical member 20 to the second inner cylindrical member 40 by the ring-shaped member 80 may be either direct or indirect. In the case of indirect connection, for example, the second outer cylindrical member 60 or the like may be arranged between the first outer cylindrical member 20 and the ring-shaped member 80.

The axial direction of the ring-shaped member 80 preferably coincides with that of the honeycomb structure 10, and the central axis of the ring-shaped member 80 preferably coincides with that of the honeycomb structure 10.

Although the shape of the ring-shaped member 80 is not particularly limited, it may have a curved surface structure. Such a structure allows the first fluid to flow smoothly through the honeycomb structure 10 during the heat recovery mode (when the on-off valve 70 is closed), thereby reducing the pressure loss.

The ring-shaped member 80 is preferably made of a metal in terms of manufacturability, although not particularly limited thereto. Examples of the material of the ring-shaped member 80 that can be used herein include stainless steel, titanium alloys, copper alloys, aluminum alloys, brass and the like. Among them, the stainless steel is preferable because it has high durability and reliability and is inexpensive.

The ring-shaped member 80 preferably has a thickness of 0.1 mm or more, and more preferably 0.3 mm or more, and still more preferably 0.5 mm or more, although not particularly limited thereto. The thickness of the ring-shaped member 80 of 0.1 mm or more can ensure durability and reliability. The thickness of the ring-shaped member 80 is preferably 10 mm or less, and more preferably 5 mm or less, and still more preferably 3 mm or less. The thickness of the ring-shaped member 80 of 10 mm or less can reduce the weight of the heat exchanger 100.

The first fluid and the second fluid used in the heat exchanger 100 are not particularly limited, and various liquids and gases can be used. For example, when the heat exchanger 100 is mounted on a motor vehicle, an exhaust gas can be used as the first fluid, and water or engine antifreeze coolants (LLC defined by JIS K2234: 2006) can be used as the second fluid. Further, the first fluid can be a fluid having a temperature higher than that of the second fluid.

The heat exchanger 100 can be produced in accordance with a method known in the art. For example, the heat exchanger 100 can be produced in accordance with the method as described below.

First, the honeycomb structure 10 is inserted into the first outer cylindrical member 20, and the first outer cylindrical member 20 is fitted to the outer peripheral wall 12 of the honeycomb structure 10. Subsequently, the first inner cylindrical member 30 is inserted into the hollow region of the honeycomb structure 10 and the first inner cylindrical member 30 is fitted to the inner peripheral wall 11 of the honeycomb structure 10. The second outer cylindrical member 60 is then arranged on and fixed to the radially outer side of the first outer cylindrical member 20. The feed pipe 62 and the discharge pipe may be previously fixed to the second outer cylindrical member 60, but they may be fixed to the second outer cylindrical member 60 at an appropriate stage. Next, the second inner cylindrical member 40 is arranged on the predetermined position, and fixed to the first outer cylindrical member 20. Further, when the ring-shaped member 80 is provided, the ring-shaped member 80 is arranged between the second inner cylindrical member 40 and the first outer cylindrical member 20 or the second outer cylindrical member 60 and fixed. The tubular member 50 is then placed on the outflow port 21b side of the first outer cylindrical member 20 and connected. The on-off valve 70 is then attached to the outflow port 31b side of the first inner cylindrical member 30.

In addition, the arranging and fixing (fitting) orders of the respective members are not limited to the above orders, and they may be changed as needed within a range in which the members can be produced. As the fixing (fitting) method, the above method may be used.

DESCRIPTION OF REFERENCE NUMERALS

• • 10 honeycomb structure
  • 11 inner peripheral wall
  • 12 outer peripheral wall
  • 13a first end face
  • 13b second end face
  • 14 cell
  • 15 partition wall
  • 15a first partition wall
  • 15b second partition wall
  • 20 first outer cylindrical member
  • 21a inflow port
  • 21b outflow port
  • 30 first inner cylindrical member
  • 31a inflow port
  • 31b outflow port
  • 32 through hole
  • 33 downstream end portion
  • 40 second inner cylindrical member
  • 41a inflow port
  • 41b outflow port
  • 50 tubular member
  • 51a inflow port
  • 51b outflow port
  • 60 second outer cylindrical member
  • 61a inflow port
  • 61b outflow port
  • 62 feed pipe
  • 70 on-off valve
  • 71 bearing
  • 72 shaft
  • 80 ring-shaped member
  • 100 heat exchanger

Claims

1. A honeycomb structure for a heat exchanger, the honeycomb structure comprising: an inner peripheral wall; an outer peripheral wall; and partition walls disposed between the inner peripheral wall and the outer peripheral wall, the partition walls defining a plurality of cells each extending from a first end face to a second end face,

wherein, in a cross section orthogonal to an extending direction of the cells, the partition walls comprise one or more first partition walls extending in a radial direction, the inner peripheral wall has an inner diameter of more than 50 mm and 75 mm or less, and the outer peripheral wall has an outer diameter of 60 to 100 mm, and

wherein the honeycomb structure has an opening ratio of 0.15 or more.

2. The honeycomb structure for a heat exchanger according to claim 1, wherein the partition walls further comprise one or more second partition walls extending in a circumferential direction in a cross section orthogonal to an extending direction of the cells.

3. The honeycomb structure for a heat exchanger according to claim 1, wherein the opening ratio is 0.30 or more.

4. The honeycomb structure for a heat exchanger according to claim 2, wherein the opening ratio is 0.30 or more.

5. The honeycomb structure for a heat exchanger according to claim 1, wherein the opening ratio is 0.60 or less.

6. The honeycomb structure for a heat exchanger according to claim 2, wherein the opening ratio is 0.60 or less.

7. A heat exchanger comprising the honeycomb structure for a heat exchanger according to claim 1.

8. A heat exchanger comprising the honeycomb structure for a heat exchanger according to claim 2.