Heat exchanging member and heat exchanger

A heat exchanging member includes: a pillar shape honeycomb structure having an outer peripheral wall and partition walls extending through the honeycomb structure from a first end face to a second end face to define a plurality of cells forming a through channel of a first fluid, and a covering member for covering the outer peripheral wall of the honeycomb structure. In a cross section of the honeycomb structure perpendicular to a flow direction of the first fluid, the partition walls includes: a plurality of first partition walls extending in a radial direction from the side of a center portion of the cross section; and a plurality of second partition walls extending in a circumferential direction, and a number of the first partition walls on the side of the central portion is less than a number of the first partition walls on the side of the outer peripheral wall.

TECHNICAL FIELD

The present invention relates to a heat exchanging member and a heat exchanger. More particularly, the present invention relates to a heat exchanging member for transmitting heat of a first fluid (on a high temperature side) to a second fluid (a low temperature side), and to a heat exchanger including the heat exchanging member.

BACKGROUND ART

Recently, there is a need for improvement of fuel economy of motor vehicles. In particular, a system is expected that warms up a coolant, engine oil and 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.

In such systems, for example, the use of a heat exchanger is considered. The heat exchanger is an apparatus including a heat exchanging member for conducting heat exchange 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 high temperature (for example, an exhaust gas) to the second fluid having a low temperature (for example, cooling water).

As a heat exchanger for recovering heat from a gas with elevated temperature such as a motor vehicle exhaust gas, a heat exchanger having a heat exchanging member made of a refractory metal has been known. However, there have been problems that the refractory metal is expensive and further difficult to be processed, has high density and heavy weight, and has lower thermal conductivity, and the like. In view of the problems, recently, a heat exchanger is being developed that houses a heat exchanging member having a pillar shape honeycomb structure in a casing, and allows a first fluid to flow through cells of the honeycomb structure, and a second fluid to flow on an outer peripheral surface of the heat exchanging member in the casing.

As a honeycomb structure used for the heat exchanging member, prior art proposes a pillar shape honeycomb structure including: first partition walls each extending in a radial direction from a central portion toward an outer peripheral portion; and second partition walls each extending in a circumferential direction, in a cross section perpendicular to a flow direction of a first fluid (a cell extending direction) (patent document 1).

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, in the pillar shape honeycomb structure as described in Patent Document 1, it is difficult to form cells, because a space between adjacent first partition walls becomes narrower toward the side of the center portion. In particular, to increase thermal conductivity (i.e., a heat recovery efficiency) in the radial direction of the pillar shape honeycomb structure, an increased number of the first partition walls extending in the radial direction is desirable. However, as the number of the first partition walls is increased, it will be more difficult to form the cells on the side of the central portion. If the cells are not formed on the side of the central portion or the cross sectional areas of the cells formed on the side of the center portion are too small, there is an issue that a pressure loss of the heat exchanging member is increased.

In response to the above issue, it is an object of the present invention to provide a heat exchanging member and a heat exchanger which can suppress an increase in a pressure loss while improving a heat recovery efficiency.

Solution to Problem

As a result of extensive research to solve the above issue, the present inventors have found that by decreasing the number of the first partition walls on the side of the central portion as compared with the number of the first partition walls on the side of the outer peripheral wall, the cells can be easily formed even on the central portion side of the honeycomb structure, achieving both improvement of a heat recovery efficiency and suppression of an increase in a pressure loss, and they have completed the present invention.

Thus, the present invention relates to a heat exchanging member comprising: a pillar shape honeycomb structure having an outer peripheral wall and partition walls extending through the pillar shape honeycomb structure from a first end face to a second end face to define a plurality of cells forming a through channel of a first fluid, and a covering member for covering the outer peripheral wall of the pillar shape honeycomb structure, wherein in a cross section of the pillar shape honeycomb structure perpendicular to a flow direction of the first fluid, the partition walls comprise: a plurality of first partition walls extending in a radial direction from the side of a center portion of the cross section; and a plurality of second partition walls extending in a circumferential direction, and a number of the first partition walls on the side of the central portion is less than a number of the first partition walls on the side of the outer peripheral wall.

The present invention also relates to a heat exchanger comprising the heat exchanging member.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a heat exchanging member and a heat exchanger which can suppress an increase in a pressure loss while improving a heat recovery efficiency.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

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.

FIG.1shows a cross-sectional view of a pillar shape honeycomb structure in a direction parallel to a flow path direction of a first fluid (a cell extending direction), for a heat exchanging member according to a first embodiment of the present invention.FIG.2shows a cross-sectional view taken along the line a-a′ inFIG.1, which illustrates a cross-sectional view of the pillar shape honeycomb structure in a direction perpendicular to the flow direction of the first fluid, for the heat exchanging member according to the first embodiment of the present invention.

A heat exchanging member1includes: a pillar shape honeycomb structure7having an outer peripheral wall6and partition walls5extending through the pillar shape honeycomb structure7from a first end face2to a second end face3to define a plurality of cells4forming a through channel of a first fluid; and a covering member8for covering the outer peripheral wall6of the pillar shape honeycomb structure7. In the heat exchanging member1, the first flows through the plurality of cells4of the pillar shape honeycomb structure7, a second fluid flows through an outer side of the covering member8, heat exchange between the first fluid and the second fluid is performed via the outer peripheral wall6of the pillar shape honeycomb structure7and the covering member8. It should be noted that inFIG.1, the first fluid can flow in both right and left directions on a page surface ofFIG.1. The first fluid is not particularly limited, and various liquids or gases may be used. For example, when the heat exchanging member1is used for a heat exchanger mounted on a motor vehicle, the first fluid is preferably an exhaust gas.

A shape of the pillar shape honeycomb structure7is not particularly limited as long as it can allow the first fluid to flow through the cells4from the first end face2to the second end face3. Examples of the shape of the pillar shape honeycomb structure7include a cylindrical shape, an elliptic cylindrical shape, a square prism shape or other polygonal columnar shapes. Thus, in the cross section perpendicular to the flow direction of the first fluid, the outer shape of the pillar shape honeycomb structure7may be circular, elliptical, square or other polygonal. In the first embodiment, the pillar shape honeycomb structure7is in the form of cylinder and has a circular across-sectional shape.

In a cross section of the pillar shape honeycomb structure7perpendicular to the flow direction of the first fluid (i.e., in the cross section shown inFIG.2), partition walls5forming the pillar shape honeycomb structure7include a plurality of first partition walls5aextending in the radial direction from the side of a center portion of the cross section and a plurality of second partition walls5bextending in the circumferential direction. With such an arrangement, the heat of the first fluid can be transmitted in the radial direction via the first partition walls5a, so that the heat can be efficiently transmitted to the outside of the pillar shape honeycomb structure7.

In the cross section shown inFIG.2, a number of the partition walls5aon the side of the central portion is less than a number of the first partition walls5aon the side of the outer peripheral wall6. With such a configuration, the number of the cells4radially arranged will be decreased toward the central portion, so that the cells4can be easily formed even on the side of the central portion of the pillar shape honeycomb structure7. It is, therefore, possible to suppress an increase in a pressure loss of the heat exchanging member1, which is caused by difficulty in forming the cells4on the side of the central portion of the pillar shape honeycomb structure7.

Here, the number of the first partition walls5aon the side of the central portion of the pillar shape honeycomb structure7means the total number of the first partition walls5aforming a plurality of cells4in a region having a plurality of cells4aligned in the circumferential direction (hereinafter referred to as a “circumferential region”), which region is closest to the central portion of the pillar shape honeycomb structure7(that is, furthest from the outer peripheral wall6). Further, the number of the first partition walls5aon the side of the outer peripheral wall6of the pillar shape honeycomb structure7means the total number of the first partition walls5aforming a plurality of cells4in the circumferential region which is farthest from the central portion of the pillar shape honeycomb structure7(that is, closest to the outer peripheral wall6).

In the cross section shown inFIG.2, the number of the first partition walls5aon the side of the central portion of the pillar shape honeycomb structure7is preferably decreased from the side of the outer peripheral wall6toward the side of the central portion. A space between the adjacent first partition walls5abecomes narrower toward the central portion, so that it will be difficult to form the cells4. However, with such a configuration, the space between the adjacent first partition walls5acan be maintained, so that the cells4can be easily formed. Thus, an increase in a pressure loss of the heat exchanging member1can be suppressed.

It should be noted that a frequency of a decrease in the number of the first partition walls5ais not particularly limited, and it may be continuous or intermittent.

In the cross section shown inFIG.2, the first partition walls5adefining one cell4are preferably longer than the second partition walls5bdefining one cell4. The first partition walls5acontribute to thermal conductivity in the radiation direction. Therefore, with such an arrangement, the heat of the first fluid flowing through the cells4on the side of the central portion of the pillar shape honeycomb structure7can be efficiently transmitted to the outside of the pillar shape honeycomb structure7.

Each of the first partition walls5apreferably has a thickness greater than that of each of the second partition walls5b. The thickness of each partition wall5correlates with the thermal conductivity. Therefore, such a configuration can lead to larger thermal conductivity of the first partition walls5athan the thermal conductivity of the second partition walls5b. As a result, the heat of the first fluid flowing through the cells4on the side of the central portion of the pillar shape honeycomb structure7can be effectively transmitted to the outside of the pillar shape honeycomb structure7.

In addition, the thickness of the partition walls5(the first partition walls5aand the second partition walls5b) is not particularly limited, and it may be adjusted as needed depending on applications and the like. The thickness of the partition walls5may preferably be from 0.1 to 1 mm, and more preferably from 0.2 to 0.6 mm. The thickness of the partition walls5of 0.1 mm or more can provide the pillar shape honeycomb structure7with a sufficient mechanical strength. Further, the thickness of the partition walls5of 1 mm or less can prevent the pressure loss from being increased due to a decrease in an opening area and the reduction of the heat recovery efficiency due to a decrease in a contact area with the first fluid.

The partition walls5may preferably have a density of from 0.5 to 5 g/cm3. The density of the partition wall5of 0.5 g/cm3or more can provide the partition walls5with a sufficient strength. Further, the density of the partition walls5of 5 g/cm3or less can allow weight reduction of the pillar shape honeycomb structure7. The density within the above range can allow the pillar shape honeycomb structure7to be strengthened and can also provide an effect of improving the thermal conductivity. It should be noted that the density of the partition walls5is a value measured by the Archimedes method.

In the heat exchanging member1, the outer peripheral wall6of the pillar shape honeycomb structure7is subjected to an external impact, a thermal stress due to a temperature difference between the first fluid and the second fluid, and the like. Therefore, in terms of ensuring resistance to these external forces, the thickness of the outer peripheral wall6is preferably increased as compared with the thickness of the partition walls5(the first partition walls5aand the second partition walls5b). With such a configuration, any breakage (for example, cracks, chinks, and the like) in the outer peripheral wall6due to external forces can be suppressed.

It is to understand that the thickness of the outer peripheral wall6is not particularly limited, and it may be adjusted as needed depending on applications and the like. For example, when the heat exchanging member1is used for a general heat exchanging application, the thickness of the outer peripheral wall6is preferably more than 0.3 mm and 10 mm or less, and more preferably from 0.5 mm to 5 mm, and even more preferably from 1 mm to 3 mm. Further, when the heat exchanging member1is used for heat storage, the thickness of the outer peripheral wall6is preferably set to 10 mm or more to increase a heat capacity of the outer peripheral wall6.

The partition walls5and the outer peripheral wall6of the pillar shape honeycomb structure7are mainly based on ceramics. The phrase “mainly based on ceramics” means that a ratio of a mass of ceramics to the total mass of the partition walls5and the outer peripheral wall6is 50% by mass or more.

Each of the partition walls5and the outer peripheral wall6preferably 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 partition walls5and the outer peripheral wall6may be 0%. The porosity of the partition walls5and the outer peripheral wall6of 10% or less can lead to improvement of thermal conductivity.

The partition walls5and the outer peripheral wall6preferably 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 ratio of a mass of SiC (silicon carbide) to the total mass of the partition walls5and the outer peripheral wall6is 50% by mass or more.

More particularly, the material of the pillar shape honeycomb structure7that can be used includes Si-impregnated SiC, (Si+Al) impregnated SiC, 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.

A cell density (that is, the number of cells4per unit area) in the cross section ofFIG.2is not particularly limited, and it may be adjusted as needed depending on applications or the like, and preferably in a range of from 4 to 320 cells/cm2. The cell density of 4 cells/cm2or more can sufficiently ensure the strength of the partition walls5, hence the strength of the pillar shape honeycomb structure7itself and effective GSA (geometrical surface area). Further, the cell density of 320 cells/cm2or less can allow prevention of an increase in a pressure loss when the first fluid flows.

The pillar shape honeycomb structure7preferably has an isostatic strength of more than 5 MPa, and more preferably 10 MPa or more, and still more preferably 100 MPa or more. The isostatic strength of the pillar shape honeycomb structure7of more than 5 MPa can lead to the pillar shape honeycomb structure7having improved durability. The isostatic strength of the pillar shape honeycomb structure7can be measured according to the method for measuring isostatic fracture strength as defied in the JASO standard M505-87 which is a motor vehicle standard issued by Society of Automotive Engineers of Japan, Inc.

A diameter of the pillar shape honeycomb structure7in the cross section ofFIG.2may preferably be from 20 to 200 mm, and more preferably from 30 to 100 mm. Such a diameter can allow improvement of heat recovery efficiency. When the shape of the pillar shape honeycomb structure7in the cross section ofFIG.2is not circular, the diameter of the largest inscribed circle that is inscribed in the shape of the cross section of the pillar shape honeycomb structure7is defined as the diameter of the pillar shape honeycomb structure7in the cross section ofFIG.2.

A length of the pillar shape honeycomb structure7(a length in the flow path direction of the first fluid) is not particularly limited, and it may be adjusted as needed depending on applications and the like. For example, the length of the pillar shape honeycomb structure7may preferably be from 3 mm to 200 mm, and more preferably from 5 mm to 100 mm, and still more preferably from 10 mm to 50 mm.

The pillar shape honeycomb structure7preferably 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 pillar shape honeycomb structure7in such a range can lead to an improved thermal conductivity and can allow the heat inside the pillar shape honeycomb structure7to 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 cells4in the pillar shape honeycomb structure7, a catalyst is preferably supported on the partition walls5of the pillar shape honeycomb structure7. The supporting of the catalyst on the partition walls5can 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, in the case of a catalyst containing a 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 allow suppression of both an increase in a pressure loss and an increase in a manufacturing cost. The support refers to a carrier on which a catalyst metal is supported. Preferable supports include those containing at least one selected from the group consisting of alumina, ceria and zirconia.

The covering member8is not particularly limited as long as it can cover the outer peripheral wall6of the pillar shape honeycomb structure7. For example, it is possible to use a tubular member that is fitted into the outer peripheral wall6of the pillar shape honeycomb structure7to cover circumferentially the outer peripheral wall6of the pillar shape honeycomb structure7.

As used herein, the “fitted” means that the pillar shape honeycomb structure7and the covering member8are fixed in a state of being suited to each other. Therefore, the fitting of the pillar shape honeycomb structure7and the covering member8encompasses cases where the pillar shape honeycomb structure7and the covering member8are 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, or the like.

The covering member8can have an inner surface shape corresponding to the outer peripheral wall6of the pillar shape honeycomb structure7. Since the inner surface of the covering member8is in direct contact with the outer peripheral wall6of the pillar shape honeycomb structure7, the thermal conductivity is improved and the heat in the pillar shape honeycomb structure7can be efficiently transferred to the covering member8.

In terms of improvement of the heat recovery efficiency, a higher ratio of an area of a portion circumferentially covered with the covering member8in the outer peripheral wall6of the pillar shape honeycomb structure7to the total area of the outer peripheral wall6of the pillar shape honeycomb structure7is 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 wall6of the pillar shape honeycomb structure7is circumferentially covered with the covering member8).

It should be noted that the term “outer peripheral wall6” as used herein refers to a surface parallel to the flow direction of the first fluid of the pillar shape honeycomb structure7, and does not include a surface (the first end face2and the second end face3) perpendicular to the flow direction of the first fluid of the pillar shape honeycomb structure7.

The covering member8is preferably made of a metal in terms of manufacturability. Further, the metallic covering member8is also preferable in that it can be easily welded to a metallic casing23that will be described below. Examples of the material of the covering member8that can be used 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 covering member8preferably 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, for the reason of durability and reliability. The thickness of the covering member8is preferably 10 mm or less, and more preferably 5 mm or less, and still more preferably 3 mm or less, for the reason of reducing thermal resistance and improving thermal conductivity.

A length of the covering member8(a length in the flow path direction of the first fluid) is not particularly limited, and it may be adjusted as needed depending on the size of the pillar shape honeycomb structure7or the like. For example, the length of the covering member8is preferably larger than the length of the pillar shape honeycomb structure7. Specifically, the length of the covering member8is preferably from 5 mm to 250 mm, and more preferably from 10 mm to 150 mm, and still more preferably from 20 mm to 100 mm.

It should be noted that when the length of the covering member8is larger than the length of the pillar shape honeycomb structure7, the covering member8is preferably provided such that the honeycomb structure7is positioned at the central portion of the covering member8.

FIG.3shows a cross-sectional view of the pillar shape honeycomb structure7in the direction perpendicular to the flow direction of the first fluid, for a heat exchanging member10according to a second embodiment of the present invention. It should be noted that components having the same reference numerals as those in the descriptions of the heat exchanging member1according to the first embodiment are the same as those of the heat exchanging member1according to the first embodiment, and descriptions of those components will be thus omitted.

In the heat exchanging member10, a cell4partitioned and formed only from a second partition wall5bis provided at the central portion, in the cross section (that is, the cross section ofFIG.3) of the pillar shape honeycomb structure7, which is perpendicular to the flow direction of the first fluid. With such an arrangement, the cell4can be formed at the central portion even if the number of the first partition walls5ais increased, so that an increase in a pressure loss of the heat exchanging member10can be stably suppressed.

Here, specific examples of the heat exchanging member1,10according to the first or second embodiment of the present invention are shown inFIGS.4to13.FIGS.4to11are front views of the heat exchanging member1,10,FIG.12is a left side view corresponding to the heat exchanging member1,10, andFIG.13is a plan view corresponding to the heat exchanging member1,10. It should be noted that a rear view is expressed in the same manner as the front view, a right side view is expressed in the same manner as the left side view, and a bottom view is expressed in the same manner as the plan view, and so those views will be omitted.

As shown inFIG.11, the heat exchanging member1,10according to the first or second embodiment of the present invention is preferably configured such that in an outer peripheral region having ⅔ of cells aligned from the outer peripheral wall6to the center portion, the total number of the cells4in the circumferential region satisfies the following relationship:
1≥NA/NB>½wherein NArepresents the total number of the cells4in the circumferential region on the side of the central portion adjacent to the cells4in NBand NBrepresents the total number of the cells4in the circumferential region on the side of the outer peripheral wall6adjacent to the cells4in NA. NA/NBis preferably ¾ or more. With such an arrangement, the sectional area of each cell4can be easily controlled to the same extent, so that an increase in a pressure loss of the heat exchanging member1,10can be stably suppressed.
<Heat Exchanger>

The heat exchanger according to the present invention includes the heat exchanging member1,10as described above. A member(s) other than the heat exchanging member1,10is/are not particularly limited, and a known member(s) may be used. For example, the heat exchanger according to the present invention may include a casing that can form a flow path for a second fluid between the casing and the covering member8of the heat exchanging member1,10.

FIG.14shows a cross-sectional view of the pillar shape honeycomb structure7in the direction parallel to the flow path direction of the first fluid, for the heat exchanger according to an embodiment of the present invention.FIG.15is a cross-sectional view taken along the line b-b′ inFIG.14, which illustrates a cross-sectional view of the pillar shape honeycomb structure7in the direction perpendicular to the flow direction of the first fluid, for the heat exchanger according to an embodiment of the present invention.

The heat exchanger20includes the heat exchanging member1; and a casing23having a second fluid inlet21and a second fluid outlet22, the casing23circumferentially covering the covering member8of the heat exchanging member1such that a flow path24for second fluid is formed between the casing23and the covering member8of the heat exchanging member1. It is preferable that the casing23circumferentially covers the entire heat exchanging member1.

In the heat exchanger20, an inner surface of the casing23is fitted into the outer peripheral surface of the covering member8of the heat exchanging member1. In this case, the heat exchanger20preferably has a structure in which the outer peripheral surface of the covering member8at both end portions in the flow path direction of the first fluid is circumferentially brought into close contact with the inner surface of the casing23, in order to prevent the second fluid from leaking to the outside. A method for bringing the outer peripheral surface of the covering member8into close contact with the inner surface of the casing23includes, but not limited to, welding, diffusion bonding, brazing, mechanical fastening, and the like. Among them, the welding is preferable because it has higher durability and reliability and can improve structural strength.

The casing23is preferably made of a metal in terms of thermal conductivity and manufacturability. Examples of the metal that can be used include stainless steel, titanium alloys, copper alloys, aluminum alloys, brass, and the like. Among them, the stainless steel is preferable because it is inexpensive and has high durability and reliability.

The casing23preferably has a thickness of 0.1 mm or more, and more preferably 0.5 mm or more, and still more preferably 1 mm or more, for the reasons of durability and reliability. The thickness of the casing23is preferably 10 mm or less, and more preferably 5 mm or less, and still more preferably 3 mm or less, in terms of cost, volume, weight and the like.

The casing23may be an integrally formed product, but it may preferably be a joined member formed of two or more members. In the case where the casing23is the joined member formed of two or more members, freedom in design for the casing23can be improved.

In the heat exchanger20, the second fluid flows into the casing23from the second fluid inlet21. Then, while passing through the flow path24for the second fluid, the second fluid undergoes heat exchange with the first fluid flowing through the cells4of the pillar shape honeycomb structure7via the covering member8of the heat exchanging member1, and then flows out from the second fluid outlet22. It should be noted that the outer peripheral surface of the covering member8of the heat exchanging member1may be covered with a member for adjusting a heat transfer efficiency.

The second fluid is not particularly limited, but the second fluid is preferably water or an antifreezing solution (LLC defined in JIS K 2234: 2006) when the heat exchanger20is mounted on a motor vehicle. For the temperatures of the first fluid and the second fluid, the temperature of the first fluid is preferably higher than the temperature of the second fluid, because under the temperature condition, the covering member8of the heat exchanging member1does not expand at the lower temperature and the pillar shape honeycomb structure7expands at the higher temperature, so that the fitted two members is difficult to be loosened. In particular, when the fitting of the pillar shape honeycomb structure7and the covering member8is shrinkage fitting, the above temperature condition can minimize a risk that the fitted members are loosened and the pillar shape honeycomb structure7is fallen out.

In the heat exchanger20, the second fluid inlet21is provided on the opposite side of the second fluid outlet22across the heat exchanging member1. However, there is no limitation for the positions of the second fluid inlet21and the second fluid outlet22, and the positions may be changed as needed to the axial direction and the outer circumferential direction, in view of the installation position of the heat exchanger20, the piping position, and the heat exchange efficiency.

In the above descriptions, the heat exchanger20using the heat exchanging member1has been described. However, needless to say, the heat exchanging member10may be used in place of the heat exchanging member1.

<Methods for Producing Heat Exchanging Member and Heat Exchanger>

Next, methods for producing the heat exchanging member and the heat exchanger according to the present invention will be described for the case of the heat exchanging member1according to the first embodiment as an example. However, the methods for producing the heat exchanging member and the heat exchanger according to the present invention are not limited to those described below.

First, a green body containing ceramic powder is extrusion-molded into a desired shape to prepare a honeycomb formed body. At this time, the shape and density of the cells4, the number, length and thickness of the partition walls5, the shape and the thickness of the outer peripheral wall6, and the like, can be controlled by selecting dies and jig in appropriate forms. The material of the honeycomb formed body that can be used includes the ceramics as described above. For example, when producing a honeycomb formed body mainly 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 metallic Si and fired under reduced pressure in an inert gas or vacuum to obtain a pillar shape honeycomb structure7having cells4defined by partition walls5.

The pillar shape honeycomb structure7is then inserted into the covering member8, whereby the outer peripheral surface of the pillar shape honeycomb structure7is circumferentially covered with the covering member8. By shrinkage-fitting them in this state, the inner peripheral surface of the covering member8is fitted into the outer peripheral surface of the pillar shape honeycomb structure7. As described above, the fitting of the pillar shape honeycomb structure7and the covering member8can be performed by, in addition to the shrinkage fitting, a fixing method based on fitting such as clearance fitting and interference fitting, or by brazing, welding, diffusion bonding or the like. Thus, the heat exchanging member1is completed.

Both end portions of the cover member8of the heat exchanging member1are joined to the inner surface of the casing23. As described above, there are various methods including fitting. If necessary, the joining portions can be joined by welding or the like. Thus, the casing23that circumferentially covers the outer peripheral surface of the cover member8is formed, and the flow path24for the second fluid is formed between the outer peripheral surface of the covering member8and the inner surface of the casing23. The heat exchanger20is thus completed.

It is to understand that while in the above descriptions, the case of using the heat exchanging member1has been described, the heat exchanging member10can be, of course, used in place of the heat exchanging member1.

EXAMPLES

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples.

A green body containing SiC powder was extrusion-molded into a desired shape, dried, processed to have predetermined external dimensions, and impregnated with Si and fired to produce a pillar shape honeycomb structure30. The pillar shape honeycomb structure30had a cylindrical shape, a diameter (outer diameter) of 70 mm, and a length in the flow path direction of the first fluid of 40 mm.FIG.16shows a cross-sectional view of the pillar shape honeycomb structure30in the direction perpendicular to the flow path direction of the first fluid. The pillar shape honeycomb structure30had a cell4defined only by a second partition wall5bat the central portion, and had less number of the first partition walls5aon the side of the central portion than the number of the first partition walls5aon the side of the peripheral wall6, such that the number of cells4was 200 in a circumferential region A, 100 in a circumferential region B, and 50 in a circumferential region C, 25 in a circumferential region D and 5 in a circumferential region E. Further, the pillar shape honeycomb structure30had a thickness of the first partition wall5aof 0.3 mm, a thickness of the second partition wall5bof 0.25 mm, and a thickness of the outer peripheral wall6of 1.5 mm.

Such a shape as described above could allow the cells4to be also formed on the central portion side of the pillar shape honeycomb structure30.

Comparative Example 1

An attempt was made to produce a pillar shape honeycomb structure in the same method as that of Example 1, with the exception that the number of cells4was set to 200 in all the circumferential regions without decreasing the number of first partition walls5aon the side of the central portion. However, it could not be molded and could not produce the pillar shape honeycomb structure.

Comparative Example 2

A pillar shape honeycomb structure40was produced in the same method as that of Example 1, with the exception that the number of cells4was set to 20 in all the circumferential regions without decreasing the number of first partition walls5aon the side of the central portion.FIG.17shows a cross-sectional view of the pillar shape honeycomb structure40in the direction perpendicular to the direction of the flow path of the first fluid. The pillar shape honeycomb structure40had a thickness of the first partition wall5aof 0.3 mm, a thickness of the second partition wall5bof 0.25 mm, and a thickness of the outer peripheral wall6of 1.5 mm.

Although the shape as described above could allow production of the pillar shape honeycomb structure40, no cell4could be formed at the center portion.

<Production of Heat Exchanging Member and Heat Exchanger>

Heat exchanging members and heat exchangers were produced using the pillar shape honeycomb structure30of Example 1 and the pillar shape honeycomb structure40of Comparative Example 2.

First, using a tubular member made of stainless steel as a covering member8, each of the pillar shape honeycomb structures30,40was inserted to an inner center of the tubular member, and an inner peripheral surface of the tubular member was then fitted into each of the honeycomb structures30,40, to produce a heat exchanging member having the structure shown inFIG.1.

For the heat exchangers, each heat exchanging member was disposed in a casing23, and both end portions of the cover member8of each heat exchanging member was joined to an inner surface of the casing23, to produce heat exchangers each having the structures shown inFIGS.14and15.

The heat exchangers thus produced were subjected to a heat exchanging test by the following method. Air (the first fluid) having a temperature (Tg1) of 400° C. flowed through each of the honeycomb structures30,40at a flow rate (Mg) of 10 g/s. On the other hand, cooling water (the second fluid) at 40° C. was supplied from the second fluid inlet21at a flow rate (Mw) of 10 L/min, and the cooling water after heat exchange was recovered from the second fluid outlet22.

Immediately after passing air and cooling water through each heat exchanger for 5 minutes from the start of supply under the above conditions, a temperature (Tw1) of the cooling water at the second fluid inlet21and a temperature (Tw2) of the cooling water at the second fluid outlet22were measured to obtain a heat recovery efficiency.

Here, a heat quantity Q recovered by the cooling water is expressed by the following equation:
Q(kW)=ΔTw×Cpw×Mw, with:
ΔTw=Tw2−Tw1, andCpw(specific heat of water)=4182 J/(kg·K).

Also, the heat recovery efficiency η of the heat exchanger is expressed by the following equation:
η (%)=Q/{(Tg1−Tw1)×Cpg×Mg}×100, with:
Cpg(specific heat of air)=1050 J/(kg·K).
<Pressure Loss Test>

In the above heat exchanging test, pressure gauges were disposed in the flow path for air located in front of and behind each heat exchanging member, respectively. The pressure loss of the air flowing through each heat exchanging member (through the cells4) was measured from a differential pressure obtained from the measurement values for those pressure gauges.

A urethane rubber sheet having a thickness of 0.5 mm was wound around the outer peripheral surface of each of the pillar shape honeycomb structures30,40, and aluminum disks each having a thickness of 20 mm were further disposed on both end portions of each of the pillar shape honeycomb structures30,40while interposing circular urethane rubber sheets between both end portions and the aluminum disks. The aluminum disks and urethane rubber sheets used had the same shape and the same size as those of the end portions of each of the pillar shape honeycomb structures30,40. Further, a vinyl tape was wound along the outer periphery of each aluminum disk, whereby a space between the outer periphery of each aluminum disk and each urethane rubber sheet was sealed to obtain a test sample. The test sample was then placed in a pressure vessel filled with water. A water pressure in the pressure vessel was increased to 200 MPa at a rate of from 0.3 to 3.0 MPa/min, and the water pressure at the time when each of the pillar shape honeycomb structures30,40was broken was measured. In the evaluation results, a case where breakage did not occur even at a water pressure of 200 MPa is expressed as “≥200 (MPa)”.

The results of the respective tests as described above are shown in Table 1.

As shown in Table 1, in Example 1, the pressure loss was less, the heat recovery efficiency was higher, and the isostatic strength was also higher.

However, in Comparative Example 2, although the pressure loss was small because the cells4were large, the heat recovery efficiency was lower and the isostatic strength was also lower.

As can be seen from the above results, the present invention can provide a heat exchanging member and a heat exchanger that can suppress an increase in a pressure loss while improving a heat recovery efficiency.

DESCRIPTION OF REFERENCE NUMERALS