CN111213026A

CN111213026A - Heat exchanger and method for manufacturing heat exchanger

Info

Publication number: CN111213026A
Application number: CN201880066984.XA
Authority: CN
Inventors: 古贺祥启; 石黑创之介; 村田登志朗
Original assignee: Ibiden Co Ltd
Current assignee: Ibiden Co Ltd
Priority date: 2017-10-17
Filing date: 2018-10-17
Publication date: 2020-05-29
Also published as: US20200318917A1; EP3699540A1; JP2019074266A; WO2019078225A1; JP6854229B2; EP3699540A4

Abstract

The heat exchanger (10) is provided with a 1 st channel through which a 1 st fluid flows, a 2 nd channel through which a 2 nd fluid flows, and a partition wall (12) that partitions the 1 st channel and the 2 nd channel. The partition wall (12) is provided with a skeleton portion (12a) having silicon carbide as a main component, and a metal-containing filling portion (12b) which fills a gap in the skeleton portion (12a) and covers the surface of the skeleton portion (12 a). The surface roughness Ra of the partition wall (12) is 1.0 [ mu ] m or more.

Description

Heat exchanger and method for manufacturing heat exchanger

Technical Field

The present invention relates to a heat exchanger and a method of manufacturing the heat exchanger.

Background

Conventionally, as a heat exchanger mounted on a vehicle or the like, the following heat exchangers are known: the heat exchanger includes a plurality of 1 st flow paths and a plurality of 2 nd flow paths partitioned by partition walls, and performs heat exchange between a 1 st fluid flowing through the 1 st flow path and a 2 nd fluid flowing through the 2 nd flow path by the partition walls. The partition walls of such a heat exchanger are preferably made of a material having high thermal conductivity. For example, patent document 1 discloses a technique for improving the thermal conductivity of partition walls by forming partition walls having a dense structure in which metal silicon is infiltrated into a porous body of silicon carbide. The partition walls of the dense structure are formed by depositing a porous body of silicon carbide in a metal silicon atmosphere and then depositing metal silicon.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2010-271031

Disclosure of Invention

Technical problem to be solved by the invention

Since partition walls formed by infiltrating a metal such as metal silicon into a porous body of silicon carbide have a dense structure, smooth surfaces with few irregularities tend to be easily formed. In particular, as disclosed in patent document 1, when the partition walls are formed by depositing metal silicon by vapor deposition in a porous body of silicon carbide under a metal silicon atmosphere, since the metal silicon exists in very small units, unevenness is not easily formed after vapor deposition, and the partition walls having smooth surfaces are easily formed. Therefore, the contact area between the partition wall and the fluid flowing through the flow path is reduced, which results in a problem of low heat exchange efficiency. The purpose of the present invention is to improve the heat exchange efficiency of a heat exchanger having partition walls formed by infiltrating a metal such as metal silicon into a porous body of silicon carbide.

Means for solving the problems

A heat exchanger according to the present invention for solving the above problems includes a 1 st channel through which a 1 st fluid flows, a 2 nd channel through which a 2 nd fluid flows, and a partition wall that partitions the 1 st channel and the 2 nd channel, and heat is exchanged between the 1 st fluid and the 2 nd fluid, wherein the partition wall includes a skeleton portion containing silicon carbide as a main component, and a metal-containing filling portion that fills a gap between the skeleton portion and covers a surface of the skeleton portion, and a surface roughness Ra of the partition wall is 1.0 μm or more.

By setting the surface roughness Ra of the partition wall to 1.0 μm or more, the contact area between the fluid and the partition wall can be increased, and therefore the heat exchange efficiency can be improved.

In the heat exchanger of the present invention, the metal is preferably metallic silicon. By using silicon metal, the thermal conductivity of the partition wall can be improved, and the heat exchange efficiency can be improved. In addition, since the difference in thermal expansion coefficient between the metal silicon and the silicon carbide forming the skeleton portion is small, breakage due to thermal shock during use can be prevented.

In the heat exchanger of the present invention, the surface roughness of the partition wall is preferably 5.0 μm or less. With this configuration, the flow resistance of the fluid can be reduced.

A method of manufacturing a heat exchanger according to the present invention for solving the above-described problems, the heat exchanger including a 1 st channel through which a 1 st fluid flows, a 2 nd channel through which a 2 nd fluid flows, and a partition wall that partitions the 1 st channel and the 2 nd channel, and performing heat exchange between the 1 st fluid and the 2 nd fluid, the method including: a molding step of molding a mixture containing silicon carbide particles, an organic binder and a dispersion medium to obtain a molded body; a degreasing step of removing the organic binder contained in the molded body to obtain a porous degreased body; and an infiltration step of infiltrating a metal into the degreased body, wherein in the infiltration step, the metal block is heated to a temperature not lower than the melting point of the metal in a state of being in contact with the degreased body, and the metal is infiltrated in an amount corresponding to a volume 1.01 to 1.1 times the pore volume of the degreased body.

The surface roughness of the partition wall can be increased by adjusting the conditions for infiltrating the metal into the porous body of silicon carbide, specifically, by infiltrating the metal by heating the metal block to a temperature not lower than the melting point of the metal in a state where the metal block is in contact with the porous degreased body, and by setting the amount of the infiltrated metal to a predetermined amount. As a result, the heat transfer efficiency from the fluid to the partition wall and the heat transfer efficiency from the partition wall to the fluid can be improved, and the heat exchange efficiency of the heat exchanger can be improved.

In the method for manufacturing a heat exchanger according to the present invention, the metal is preferably metallic silicon. Since the metal silicon has good wettability with silicon carbide forming the skeleton portion, the silicon carbide particles can be filled without gaps.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the heat exchange efficiency of a heat exchanger having a partition wall formed by infiltrating a metal into a porous body of silicon carbide can be improved.

Drawings

Fig. 1 is a perspective view of a heat exchanger.

Fig. 2 is a cross-sectional view taken along line 2-2 of fig. 1.

Fig. 3 is a cross-sectional view taken along line 3-3 of fig. 2.

Fig. 4 is a cross-sectional view taken along line 4-4 of fig. 2.

Fig. 5 is an explanatory view of the molding process.

Fig. 6 is an explanatory view of the machining process (an explanatory view of a state in which the machining jig of the 1 st machining is inserted into the molded body).

Fig. 7 is an explanatory view of the machining process (an explanatory view of the 1 st machined jig after being inserted into the molded body and extracted).

Fig. 8 is an explanatory view of the processing step (explanatory view of the 2 nd processing).

Fig. 9 is an explanatory view of the degreasing step.

Fig. 10 is an explanatory view of the infiltration process.

Detailed Description

An embodiment of the heat exchanger will be described below.

As shown in fig. 1 and 2, the heat exchanger 10 of the present embodiment includes a rectangular tubular peripheral wall 11 and a partition wall 12, and the partition wall 12 partitions the inside of the peripheral wall 11 into a plurality of 1 st cell channels 13a and a plurality of 2 nd cell channels 13b extending in the axial direction of the peripheral wall 11. The rectangular tubular peripheral wall 11 has a pair of longitudinal side walls 11a facing each other and a pair of lateral side walls 11b facing each other, and is configured such that a cross-sectional shape orthogonal to the axial direction of the peripheral wall 11 forms a horizontally long rectangle.

As shown in fig. 2, the partition walls 12 include partition walls 12 parallel to the vertical side walls 11a and partition walls 12 parallel to the horizontal side walls 11b in a cross section perpendicular to the axial direction of the peripheral wall 11, and form a lattice-like cell structure. The structure of the channel formed by the partition walls 12 is not particularly limited, and may be, for example, a structure in which the wall thickness of the partition walls 12 is 0.1 to 0.5mm, and the channel density is 1cm per channel²The cross section orthogonal to the axial direction of the peripheral wall 11 has a pore channel structure of 15-93 pore channels.

As shown in fig. 3, the 1 st cell 13a is a cell through which the 1 st fluid flows, and both ends thereof are sealed by the sealing portions 22. As shown in fig. 4, the 2 nd port hole 13b is a port hole through which the 2 nd fluid flows, and both ends thereof are open.

The 1 st fluid is not particularly limited, and for example, a known heat transfer medium can be used. Examples of the known heat medium include cooling water (Long Life Coolant): LLC) and organic solvents such as ethylene glycol. The 2 nd fluid is not particularly limited, and examples thereof include exhaust gas of an internal combustion engine.

As shown in fig. 2, in a cross section orthogonal to the axial direction of the peripheral wall 11, the cross-sectional shape of the 1 st cell passage 13a is identical to the cross-sectional shape of the 2 nd cell passage 13 b.

As shown in fig. 2, the heat exchanger 10 includes a plurality of 1 st cell line 14a in which only the 1 st cell 13a is aligned in parallel with the vertical side wall 11a of the peripheral wall 11, and a 2 nd cell line 14b in which only the 2 nd cell 13b is aligned in parallel with the vertical side wall 11 a. In the present embodiment, 4 rows of the 2 nd cell rows 14b are arranged between the adjacent 1 st cell rows 14a, and an arrangement pattern in which the arrangement is repeated is formed.

As shown in fig. 1 and 3, in the heat exchanger 10, the communication portion 15 formed to extend in the longitudinal direction (which is the direction along the longitudinal side wall 11 a) is provided in the 1 st cell row 14a, and the communication portion 15 penetrates the partition wall 12 that partitions the 1 st cell channels 13a adjacent in the longitudinal direction, so that the cell channels constituting the 1 st cell row 14a communicate with each other. An end of one side (upper side in fig. 3) in the longitudinal direction of the communicating portion 15 is opened at the peripheral wall 11 (lateral wall 11b), and an end of the other side (lower side in fig. 3) thereof reaches the 1 st porthole 13a located most to the other side in the longitudinal direction. That is, the communicating portions 15 are all open on the same surface of the peripheral wall 11, and each communicating portion 15 extends to the 1 st porthole 13a located at the position farthest from the opening of the communicating portion 15. The heat exchanger 10 includes, as the communicating portion 15, a 1 st communicating portion 15a provided on the 1 st end portion 10a side, which is one end portion in the axial direction of the heat exchanger 10, and a 2 nd communicating portion 15b provided on the 2 nd end portion 10b side, which is the other end portion in the axial direction of the heat exchanger 10.

As shown in fig. 3, a 1 st flow path 16 including the 1 st cell line 13a, the 1 st communicating portion 15a, and the 2 nd communicating portion 15b is formed inside the heat exchanger 10, and an opening of the 1 st communicating portion 15a and an opening of the 2 nd communicating portion 15b formed in the peripheral wall 11 of the heat exchanger 10 function as an inlet or an outlet of the 1 st flow path 16, respectively. As shown in fig. 4, a 2 nd flow path 17 including the 2 nd cell channels 13b is formed in the heat exchanger 10, and the 1 st end portion 10a and the 2 nd end portion 10b of the peripheral wall 11 function as an inlet or an outlet of the 2 nd flow path 17, respectively. The heat exchanger 10 having the above-described configuration can exchange heat between the 1 st fluid flowing through the 1 st channel 16 and the 2 nd fluid flowing through the 2 nd channel 17 via the partition wall 12.

Next, the materials constituting the peripheral wall 11 and the partition wall 12 of the heat exchanger 10 and the surface shapes of the peripheral wall 11 and the partition wall 12 will be described. Since the peripheral wall 11 and the partition wall 12 of the present embodiment are made of the same material and have the same surface shape, the partition wall 12 will be described in detail below, and the description of the peripheral wall 11 will be omitted.

As shown in fig. 1, the partition wall 12 includes a skeleton portion 12a having a porous structure, and a metal-containing filling portion 12b that fills a gap of the skeleton portion 12a and covers a surface of the skeleton portion 12 a. The skeleton portion 12a contains silicon carbide as a main component. Here, "main component" means 50% by mass or more. The skeleton portion 12a may contain a component other than silicon carbide. Examples of the component other than silicon carbide include ceramic materials such as carbides of tantalum carbide and tungsten carbide, and nitrides of silicon nitride and boron nitride. When a component other than silicon carbide is contained, the component may contain only 1 kind, or may contain 2 or more kinds.

Examples of the metal constituting the filling portion 12b include metallic silicon, aluminum, iron, and copper. Among these, metallic silicon is particularly preferable. The metal constituting the filling portion 12b may contain only 1 kind of the above-mentioned metals, or may contain 2 or more kinds.

The volume ratio of the skeleton portion 12a to the filled portion 12b (skeleton portion: filled portion) in the partition wall 12 is preferably 60:40 to 40:60, for example. The volume of the metal constituting the filling portion 12b is preferably larger than the volume of the pores, and more preferably 1.01 to 1.1 times the volume of the pores. By making it 1.01 times or more, the surface roughness of the partition wall can be increased; by setting the ratio to 1.1 times or less, metal can be prevented from being deposited on the surfaces of the partition wall and the peripheral wall.

The surface of the partition wall 12 is constituted by the filling portion 12 b. The surface roughness (arithmetic average roughness: Ra) of the partition wall 12 is 1.0 μm or more, preferably 1.2 μm or more. The surface roughness of the partition wall 12 is preferably 5.0 μm or less. The surface roughness of the partition wall 12 can be adjusted by changing the conditions for forming the filling portion 12b by infiltrating a metal into the skeleton portion 12a of the porous structure.

The method for measuring the surface roughness Ra is as follows.

A plate of 10 mm. times.10 mm was cut out from the dividing wall of the heat exchanger to prepare a sample. A surface roughness measuring instrument (for example, Surfcom1400d manufactured by tokyo precision) was used to measure the surface roughness Ra of the sample along the longitudinal direction of the flow path with a span of 2 mm. The same measurement was performed 3 times, and the average value was obtained.

Next, a method of manufacturing the heat exchanger according to the present embodiment will be described with reference to fig. 5 to 10. The heat exchanger is manufactured by sequentially performing a molding step, a processing step, a degreasing step, and an impregnation step described below.

(Molding Process)

As a raw material used for molding a heat exchanger, a clay-like mixture containing silicon carbide particles, an organic binder, and a dispersion medium is prepared. In this case, particles other than silicon carbide, such as ceramic particles, may be mixed as necessary.

The average particle diameter (50% particle diameter) of the silicon carbide particles and the particles other than silicon carbide particles is preferably 0.5 to 50 μm, for example.

Examples of the organic binder include polyvinyl alcohol, methyl cellulose, ethyl cellulose, and carboxymethyl cellulose. Among these organic binders, methylcellulose and carboxymethylcellulose are particularly preferable. In addition, only one of the organic binders may be used, or two or more of them may be used in combination.

Examples of the dispersion medium include water and an organic solvent. Examples of the organic solvent include ethanol. In addition, only one kind of the dispersion medium may be used, or two or more kinds may be used in combination.

In addition, other components may be further contained in the mixture. Examples of the other components include a plasticizer and a lubricant. Examples of the plasticizer include polyoxyalkylene compounds such as polyoxyethylene alkyl ethers and polyoxypropylene alkyl ethers. The lubricant may be, for example, glycerin.

The clay-like mixture was used to form a molded article 20 shown in FIG. 5. The molded body 20 includes a rectangular tubular peripheral wall 11 and a partition wall 12 that partitions the interior of the peripheral wall 11 into a plurality of cell channels 13 extending in the axial direction of the peripheral wall 11. All the cell channels 13 included in the molded body 20 are open at both ends. The molded body 20 can be molded by, for example, extrusion molding. The molded article 20 thus obtained is subjected to a drying treatment for drying the molded article 20.

(working procedure)

In the processing step, the 1 st processing for forming the 1 st communication part and the 2 nd communication part in the molded body and the 2 nd processing for sealing both ends of a part of the cell channels in the molded body are performed.

As shown in fig. 6, in the 1 st process, for example, a method of bringing a heated processing tool 21 into contact with the molded body is used, and the peripheral wall 11 and a part of the partition wall 12 in the molded body 20 are removed to form the 1 st communicating portion 15a and the 2 nd communicating portion 15 b.

Specifically, as shown in fig. 6, as the machining tool 21, inserts (blades) having an outer shape corresponding to the 1 st communicating portion 15a and the 2 nd communicating portion 15b are prepared. The insert is formed of a heat-resistant metal (e.g., stainless steel) and is set to a thickness not exceeding the width of the 1 st cell channel 13 a. Next, the insert is heated to a temperature at which the organic binder contained in the shaped body 20 is burned off. For example, when the organic binder is methylcellulose, the insert is heated to 400 ℃ or higher.

As shown in fig. 7, the heated insert sheet is inserted into the molded body 20 from the circumferential outside and then pulled out, thereby forming the 1 st communicating portion 15a and the 2 nd communicating portion 15 b. At this time, when the heated tab comes into contact with the molded body 20, the organic binder contained in the molded body 20 in the contact portion burns and is burned off. Therefore, the insertion resistance of the insert into the molded body 20 is very small, and the insert is not easily deformed or broken at the peripheral portion of the inserted portion. In addition, burn-out occurs by the organic binder, and the amount of generated machining chips decreases.

As shown in fig. 8, in the 2 nd processing, of the plurality of cell channels 13 formed in the molded body 20, clay-like mixtures used in the molding step are filled into both end portions of the cell channels 13 constituting the 1 st cell channel 13a, and seal portions 22 for sealing both end portions of the cell channels 13 are formed. Then, the molded body 20 is subjected to a drying process for drying the sealing portion 22.

The molded article is obtained by undergoing the processing steps including the 1 st processing and the 2 nd processing. The order of the 1 st process and the 2 nd process is not particularly limited, and the 1 st process may be performed after the 2 nd process.

(degreasing Process)

In the degreasing step, the organic binder contained in the work-molded body is burned out by heating the work-molded body. This can provide a degreased body obtained by removing the organic binder from the molded body. As shown in fig. 9, the degreased body 30 obtained by removing the organic binder from the worked molded body through the degreasing step has a porous structure having gaps between particles of silicon carbide. Here, the volume of the gap (pore volume) in the degreased body 30 is preferably 40 to 60 vol%. The pore volume of the degreased body 30 can be adjusted by changing the content of the silicon carbide particles in the mixture used in the molding step.

(infiltration step)

In the infiltration step, a metal such as metal silicon is infiltrated into the inside of each wall constituting the degreased body. In the infiltration step, the metal block is heated to a temperature equal to or higher than the melting point of the metal (for example, to 1450 ℃ or higher in the case of metallic silicon) in an inert gas atmosphere such as argon or nitrogen or in a vacuum while being in contact with the degreased body. As a result, as shown in fig. 10, the molten metal enters gaps between particles constituting the degreased body by a capillary phenomenon, and the metal penetrates into the gaps. The portion of the degreased body that contacts the metal block is not particularly limited, and from the viewpoint of high efficiency, the metal block is preferably brought into contact with the upper portion of the degreased body.

In the case of using metallic silicon, it is preferable to use metallic silicon having a purity of less than 98%. Metallic silicon (a bulk of metallic silicon) has a tendency to have a melting point that decreases as its purity decreases. Therefore, by using low-purity metallic silicon, the heating temperature required in the infiltration step can be suppressed to be low. As a result, the manufacturing cost can be suppressed. The purity of the metal silicon is, for example, 95% or more.

Here, the amount of the metal lumps (the amount of the metal charged into the degreased body) in contact with the degreased body is made larger than the amount corresponding to the pore volume of the degreased body 30 or smaller than the amount corresponding to the pore volume of the degreased body 30. Specifically, the amount of the metal to be charged is set to an amount corresponding to 1.01 to 1.1 times the volume of pores of the degreased body 30.

When the amount of metal to be charged is larger than the amount corresponding to the volume of the pores of the degreased body 30, a part of the metal to be infiltrated overflows from the pores of the degreased body 30 to form a convex portion on the surface. As a result, the surface roughness of the peripheral wall and the partition wall formed increases. When the amount of metal to be charged is smaller than the amount corresponding to the volume of the pores of the degreased body 30, the uneven shape of the pores of the degreased body 30 appears on the surfaces of the peripheral wall and the partition wall. As a result, the surface roughness of the peripheral wall and the partition wall formed increases.

The heat treatment in the infiltration step may be performed continuously with the heat treatment in the degreasing step. For example, the organic binder may be removed by heating at a temperature lower than the melting point of the metallic silicon in a state where the metallic silicon block is brought into contact with the work-forming body to prepare a degreased body, and then the heating temperature may be increased to the melting point of the metallic silicon or higher to infiltrate the molten metallic silicon into the degreased body.

The heat exchanger can be obtained by undergoing the infiltration process described above.

Here, in the present embodiment, special temperature control is performed in the steps after the degreasing step. That is, the steps after the degreasing step are performed at a temperature lower than the sintering temperature of the silicon carbide contained in the mixture used in the molding step so that the molded body and the degreased body are not exposed to a temperature equal to or higher than the sintering temperature. Therefore, in the degreasing step, the organic binder is heated at a temperature not lower than the temperature at which the organic binder can be burned out and lower than the sintering temperature. Similarly, in the infiltration step, heating is performed at a temperature equal to or higher than the melting point of the metal silicon and lower than the sintering temperature.

Next, the operation and effect of the present embodiment will be described.

(1) The heat exchanger includes a 1 st channel through which a 1 st fluid flows, a 2 nd channel through which a 2 nd fluid flows, and a partition wall that partitions the 1 st channel and the 2 nd channel. The partition wall includes a skeleton portion containing silicon carbide as a main component, and a metal-containing filling portion filled in a gap of the skeleton portion and covering a surface of the skeleton portion. The surface roughness Ra of the partition wall is 1.0 [ mu ] m or more.

With the above configuration, the contact area between the partition wall and the fluid when the 1 st fluid and the 2 nd fluid flow through can be increased. As a result, the heat transfer efficiency from the fluid to the partition wall and the heat transfer efficiency from the partition wall to the fluid can be improved, and the heat exchange efficiency of the heat exchanger can be improved.

(2) The filling part is metal silicon.

By forming the filling portion made of metal silicon, the thermal conductivity of the partition wall can be improved, and the heat exchange efficiency can be improved. In addition, since the difference in thermal expansion coefficient between the metal silicon and the silicon carbide forming the skeleton portion is small, breakage due to thermal shock during use can be prevented.

(3) The surface roughness Ra of the partition wall is 5.0 [ mu ] m or less.

With the above configuration, it is possible to suppress the 1 st fluid and the 2 nd fluid flowing along the partition wall from being turbulent due to the surface shape of the partition wall, and increase the flow resistance.

(4) A method for manufacturing a heat exchanger having a 1 st channel through which a 1 st fluid flows, a 2 nd channel through which a 2 nd fluid flows, and a partition wall that partitions the 1 st channel and the 2 nd channel, comprises the steps of: a molding step of molding a mixture containing silicon carbide particles, an organic binder and a dispersion medium to obtain a molded body; a degreasing step of removing the organic binder contained in the molded body to obtain a porous degreased body; and an infiltration step of infiltrating the metal into the degreased body. In the infiltration step, the metal block is heated to a temperature not lower than the melting point of the metal while being in contact with the degreased body, and the metal is infiltrated in an amount corresponding to a volume 1.01 to 1.1 times the pore volume of the degreased body.

Generally, since a partition wall formed by infiltrating a metal such as metal silicon into a porous body of silicon carbide has a dense structure, a smooth surface with few irregularities tends to be easily formed. In particular, as disclosed in patent document 1, when the partition walls are formed by depositing metal silicon by vapor deposition in a porous body of silicon carbide under a metal silicon atmosphere, since the metal silicon exists in very small units, unevenness is not easily formed after vapor deposition, and the partition walls having smooth surfaces are easily formed. In contrast, with the above configuration, even when the partition wall is formed by infiltrating a metal into the porous body of silicon carbide, the surface roughness of the partition wall can be increased.

(5) The metal infiltrated into the degreased body is metal silicon.

Since the metal silicon has good wettability with silicon carbide forming the skeleton portion, the silicon carbide particles can be filled without gaps.

(6) In the infiltration step, the metal block is heated while being placed on the degreased body.

With the above configuration, the metal can be efficiently infiltrated by the action of the molten metal flowing down along the walls of the degreased body.

(7) The heat exchanger according to the present embodiment is manufactured under the above-described temperature control, whereby the silicon carbide particles are arranged in contact with each other to form the skeleton portion, and the gaps in the skeleton portion are filled with the metal silicon to maintain the shape. That is, the silicon carbide particles are in a state of not having a bonded portion (neck portion) by sintering. Thus, even if strain is generated in the partition walls due to a temperature difference in the heat exchanger during use, cracks can be prevented from being generated in the necks between the silicon carbide particles. And the crack can be inhibited from spreading by the neck.

This embodiment can be modified as follows. The configuration of the above embodiment or the configurations shown in the following modifications may be combined as appropriate.

The shape of the heat exchanger (for example, the outer shape of the heat exchanger body and the shape of the duct) is not limited to the above embodiment, and may be appropriately modified.

In the above embodiment, the peripheral wall is also configured to include the skeleton portion and the filling portion and to have a surface roughness Ra of 1.0 μm or more, as in the partition wall, but the material of the peripheral wall and the surface shape of the peripheral wall are not particularly limited.

In the method of manufacturing the heat exchanger, a part or all of the processing steps may be omitted. The machining step is a step for bringing the shape of the molded body obtained in the molding step close to the shape of the heat exchanger to be manufactured. Therefore, in the processing step, only necessary processing may be performed in accordance with the shape of the heat exchanger to be manufactured and the shape of the molded body. In the processing step, processing other than the 1 st processing and the 2 nd processing may be performed. Among them, the processing including the removal of a part of the molded body is preferably performed by an operation of bringing a processing tool heated to a temperature at which the organic binder is burned out into contact with the molded body.

The method for manufacturing the heat exchanger may further include steps other than the molding step, the processing step, the degreasing step, and the infiltrating step. For example, the infiltration step may be followed by surface processing such as polishing. Among these, it is preferable that the treatment performed after the degreasing step is performed at a predetermined temperature or lower, as in the impregnation step.

Examples

Examples further embodying the above embodiments will be described below.

(example 1)

First, a mixture of the following composition was prepared.

Particles of silicon carbide having an average particle diameter of 15 μm (large particles): 52.5 parts by mass

Particles (small particles) of silicon carbide having an average particle diameter of 0.5 μm: 23.6 parts by mass

Methylcellulose (organic binder): 5.4 parts by mass

Glycerin (lubricant): 1.1 parts by mass

Polyoxyalkylene compound (plasticizer): 3.2 parts by mass

Water (dispersion medium): 11.5 parts by mass

Using this mixture, a molded article having the same shape as shown in FIG. 5, a longitudinal dimension of 50mm, a lateral dimension of 100mm, a longitudinal dimension of 100mm, a peripheral wall thickness of 0.3mm, a partition wall thickness of 0.25mm, and a cell width of 1.2mm was molded.

Next, a plate-like jig heated to 400 ℃ was inserted into the peripheral wall of the molded body to form the 1 st communicating portion and the 2 nd communicating portion. Further, a clay-like mixture having the same composition as the above mixture was used to seal predetermined cells, thereby producing a molded article having a 1 st cell and a 2 nd cell. Subsequently, the molded article was heated at 450 ℃ for 5 hours to obtain a degreased article from which the organic binder was removed. Then, the plate material 153g (charge amount: amount corresponding to a volume 1.05 times as large as the pore volume of the degreased body) of metallic silicon was placed on the degreased body, and the degreased body was heated at 1550 ℃ for 7 hours under vacuum, thereby infiltrating the metallic silicon, and the heat exchanger of example 1 was obtained.

(example 2)

A heat exchanger of example 2 was obtained in the same manner as in example 1, except that the amount of the plate material of metal silicon (charged amount) was changed to 147.2g (an amount corresponding to a volume 1.01 times as large as the pore volume of the degreased body).

(example 3)

A heat exchanger of example 3 was obtained in the same manner as in example 1, except that the amount of the plate material of metal silicon (charged amount) was 160.3g (amount corresponding to a volume 1.1 times as large as the pore volume of the degreased body).

Comparative example

A heat exchanger of a comparative example was obtained in the same manner as in example 1, except that the amount of the plate material of metallic silicon (charged amount) was set to 145.7g (amount corresponding to a volume 1.0 times the pore volume of the degreased body).

(measurement of surface roughness)

As a sample for measurement, a partition wall having a width of 10 mm. times.10 mm in length was cut out from the heat exchangers of examples and comparative examples. The surface roughness (arithmetic average roughness: Ra) of the sample for measurement was measured by using a surface roughness measuring instrument. As the surface roughness measuring device, Surfcom1400d manufactured by tokyo precision corporation was used. The results are shown in table 1.

(measurement of exhaust Heat recovery amount)

In the heat exchangers of examples and comparative examples, cooling water of 40 ℃ was introduced from the inlet port into the 1 st port at a flow rate of 10L/min, and high-temperature gas of 400 ℃ was introduced into the 2 nd port at a flow rate of 10g/sec, and the temperature difference between the inflow time and the discharge time of the cooling water was measured to calculate the recovery amount of waste heat in each heat exchanger. The results are shown in table 1.

[ Table 1]

As shown in Table 1, in the comparative examples in which the volume of pores of the degreased body was 1 time, the surface roughness of the partition wall was 0.5. mu.m. On the other hand, in examples 1 to 3 in which the amount of silicon metal charged in the infiltration step was larger than the pore volume of the degreased body, the surface roughness of the partition wall was 1.0 to 4.5. mu.m. From the results, it was found that the surface roughness of the partition wall can be increased by increasing the amount of the metal silicon to be charged relative to the pore volume of the degreased body.

Further, it was confirmed from the results of examples 1 to 3 that the contact area between the fluid and the partition wall can be increased and the amount of exhaust heat recovery can be increased by increasing the surface roughness Ra of the partition wall. From this, it is understood that the heat exchange efficiency can be improved by increasing the surface roughness Ra of the partition wall.

Description of the symbols

10 … heat exchanger, 11 … peripheral wall, 12 … dividing wall, 12a … skeleton part, 12b … filling part, 13a … 1 st pore canal, 13b … nd pore canal, 20 … formed body and 30 … degreased body.

Claims

1. A heat exchanger comprising a 1 st channel through which a 1 st fluid flows, a 2 nd channel through which a 2 nd fluid flows, and a partition wall that partitions the 1 st channel and the 2 nd channel, wherein heat is exchanged between the 1 st fluid and the 2 nd fluid,

the partition wall has a skeleton portion containing silicon carbide as a main component, and a metal-containing filling portion which fills a gap in the skeleton portion and covers a surface of the skeleton portion,

the surface roughness Ra of the dividing wall is more than 1.0 μm.

2. The heat exchanger of claim 1, wherein the metal is metallic silicon.

3. The heat exchanger according to claim 1 or 2, wherein the dividing wall has a surface roughness Ra of 5.0 μm or less.

4. A method for manufacturing a heat exchanger having a 1 st channel through which a 1 st fluid flows, a 2 nd channel through which a 2 nd fluid flows, and a partition wall that partitions the 1 st channel and the 2 nd channel, wherein heat is exchanged between the 1 st fluid and the 2 nd fluid, the method comprising:

a molding step of molding a mixture containing silicon carbide particles, an organic binder and a dispersion medium to obtain a molded body;

a degreasing step of removing the organic binder contained in the molded body to obtain a porous degreased body; and

an infiltration step of infiltrating a metal into the degreased body,

in the infiltration step, the metal block is heated to a temperature not lower than the melting point of the metal while being in contact with the degreased body, and the metal is infiltrated in an amount corresponding to a volume 1.01 to 1.1 times the pore volume of the degreased body.

5. The method of manufacturing a heat exchanger as claimed in claim 4, wherein the metal is metallic silicon.