Patent Application
20240302113
The present invention claims the benefit of priority to Japanese Patent Application No 2023-036907 filed on Mar. 9, 2023 with the Japanese Patent Office, the entire contents of which are incorporated herein by reference in its entirety.
The present invention relates to a heat recovery member and a heat exchanger.
Heat exchangers often requires properties such as corrosion resistance. Therefore, ceramic heat exchangers are used. In the chemical and pharmaceutical industries, the heat exchangers are used for heating, cooling and condensing various fluids including acids (bromic acid, sulfuric acid, hydrofluoric acid, nitric acid, hydrochloric acid, etc.), alkalis (caustic alkalis, etc.), halides, saline solutions, organic compounds, and the like. Also, the heat exchangers are used for systems that worm up a coolant, an engine oil and an automatic transmission fluid (ATF: Automatic Transmission Fluid) at an early stage at the time of engine startup to reduce friction losses, or systems that heat an exhaust gas purifying catalyst in order to activate the catalyst at an early stage.
The ceramic heat exchanger employs a heat recovery member having a structure in which a honeycomb structure (a pillar shaped ceramic body) is housed in a metal pipe. The heat exchanger having such a structure has an advantage that even if the honeycomb structure is damaged therein, the fluids are not mixed together.
Known as a method for housing the honeycomb structure in the metal pipe is a shrink fitting method in which the metal pipe is heated, and the honeycomb structure is inserted into a predetermined position in the metal pipe, and then cooled (for example, Patent Literature 1).
However, conventional heat recovery members produced by an interference fitting method such as a shrink fitting method may lead to insufficient contact between the metal pipe and the honeycomb structure, so that it is difficult to stably obtain the desired heat recovery performance.
The present invention was made to solve the above problems. An object of the present invention is to provide a heat recovery member that has good contact between a metal pipe and a honeycomb structure and can stably improve heat recovery performance.
As a result of intensive studies for heat recovery members in which a metal pipe is fixed by interference fitting to an outer peripheral wall of a honeycomb structure, the present inventors have found that the above problems can be solved by configuring the heat recovery member so as to satisfy a specific relationship, and they have completed the present invention. That is, the present invention is illustrated as follows:
[1]
A heat recovery member comprising:
[2]
The heat recovery member according to [1], wherein in a cross section parallel to an axial direction of the metal pipe, a contact index X between the honeycomb structure and the metal pipe, represented by the following equation (2), is 0 or more:
in which Lh is a difference [mm] between positions of the first end face or the second end face of the honeycomb structure in an axial direction, θ is an angle (°) formed by a direction orthogonal to the axial direction and the first end face or the second end face, Dh is a length of the honeycomb structure in the extending direction of the cells, and Dp is an inner diameter [mm] of the straight portion in the region other than the interference fitting fixed region.
[3]
The heat recovery member according to [1] or [2], wherein the honeycomb structure is a hollow honeycomb structure further having an inner peripheral wall, the partition walls being disposed between the outer peripheral wall and the inner peripheral wall.
[4]
The heat recovery member according to any one of [1] to [3], wherein the honeycomb structure is made of a Si—SiC material.
[5]
The heat recovery member according to any one of [1] to [4], wherein the metal pipe is a stainless steel pipe.
[6]
A heat exchanger comprising:
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.
In
As shown in
The metal pipe 10 has a straight portion 11. As used herein, the “straight portion 11” means a straight pipe-shaped portion that can be interference-fitted to the honeycomb structure 20 in the state at the raw material stage (State A). Although
The honeycomb structure 20 includes an outer peripheral wall 21 and a plurality of partition walls 25 that are disposed on an inner side of the outer peripheral wall 21 and define a plurality of cells 24 each extending from a first end face 22 to a second end face 23. In the heat recovery member 100, the honeycomb structure 20 is disposed at the straight portion 11 of the metal pipe 10.
The straight portion 11 of the metal pipe 10 is fixed by interference fitting to the outer peripheral wall 21 parallel to the extending direction of the cells 24 of the honeycomb structure 20.
The fixing by interference fitting can be performed by increasing the diameter of the straight portion 11 of the metal pipe 10 by heating the metal pipe 10, as shown in the State B in
In the State C in
The heat recovery member 100 satisfies a relationship of the following equation (1):
Referring now to
In order to fix the metal pipe 10 to the honeycomb structure 20 by interference fitting (fixing by interference fitting) and to improve a contact between the metal pipe 10 and the honeycomb structure 20 in the heat recovery member 100, it is important to perform the fixing by interference fitting in the plastic deformation region of the metal pipe 10.
The left side of the above equation (1) represents an interference fitting margin that provides a tightening pressure required for performing the fixing by interference fitting in the plastic deformation region of the metal pipe 10. Further, since the inner diameter of the straight portion 11 in the region R2 other than the interference fitting fixed region R1 is substantially the same as the diameter of the straight portion 11 of the metal pipe 10 in the State A (a state at the raw material stage), the right side of the above equation (1) represents an interference fitting margin (a value obtained by subtracting the inner diameter of the straight portion 11 of the metal pipe 10 from the outer diameter of the honeycomb structure 20) in a state at the raw material stage (State A). Then, by satisfying the relationship of the equation (1) described above, the metal pipe 10 can be tightened and fixed (interference-fitted) to the honeycomb structure 20 in the plastic deformation region of the metal pipe 10. If the relationship of the equation (1) described above is not satisfied, the metal pipe 10 will be tightened and fixed to the honeycomb structure 20 in the elastic deformation region of the metal pipe 10, so that the metal pipe 10 and the honeycomb structure 20 will not be sufficiently contacted with each other.
The nominal strain [%] at the yield point of the metal pipe 10 varies depending on the material and shape of the metal pipe 10. The nominal strain [%] at the yield point of the metal pipe 10 can be determined by creating a graph representing the relationship between the nominal strain and the nominal stress in accordance with JIS Z2241:2011.
Referring now to
As shown in
In the above evaluation, the interference fitting margin was adjusted by using the honeycomb structure 20 having the same material and shape, and changing the inner diameter of the straight portion 11 of the metal pipe 10. The amount of heat recovered can be determined by producing a heat exchanger in which the outer cylindrical member is arranged at an interval on the outer side of the metal pipe 10 of the heat recovery member 100 in the radial direction so as to form a water flow path, and feeding air at 400° C. (Tg1) to the cells 24 of the honeycomb structure 20 of the heat recovery member 100 at a flow rate of 10 g/sec (Mg), and feeding water to the outer periphery of the heat recovery member 100 at a flow rate of 166 g/sec (Mw), and recovering the water. Under each of the above conditions, the feeding of the air and the water to the heat exchanger was started, and once a steady state was reached, a temperature (Tw1) of the water in the feed pipe provided in the outer cylindrical member and a temperature (Tw2) of the water in the discharge pipe were measured to determine an amount of heat recovered by water (heat recovery amount) Q. The heat recovery amount Q is expressed by the following equation:
From the viewpoint of improving the contact between the metal pipe 10 and the honeycomb structure 20 in the heat recovery member 100, in the interference-fitting fixed region R1, the straight portion 11 of the metal pipe 10 is preferably parallel to the outer peripheral wall 21 of the honeycomb structure 20 in the extending direction of the cells 24. However, in the actual production of the heat recovery member 100, the straight portion 11 of the metal pipe 10 and the outer peripheral wall 21 of the honeycomb structure 20 parallel to the extending direction of the cells 24 may not become parallel to each other in the interference-fitting fixed region R1.
From the viewpoint of improving the contact between the metal pipe 10 and the honeycomb structure 20 even in such a state, in the cross section parallel to the axial direction of the metal pipe 10, the heat recovery member 100 has a contact index X of 0 or more, between the honeycomb structure 20 and the metal pipe 10, expressed by the following equation (2):
In the equation (2), Lh is a difference [mm] between positions of the first end face 22 or the second end face 23 of the honeycomb structure 20 in the axial direction, θ is an angle (°) formed by a direction orthogonal to the axial direction and the first end face 22 or the second end face 23, Dh is a length of the honeycomb structure 20 in the extending direction of the cells 24, and Dp is an inner diameter [mm] of the straight portion in the region R2 other than the interference-fitting fixed region R1.
The contact index X represented by the above equation (2) is an index representing the contact between the metal pipe 10 and the honeycomb structure 20 due to the inclination of the honeycomb structure 20. By setting the contact index X to 0 or more, the tightening pressure of the metal pipe 10 against the honeycomb structure 20 is sufficient, so that stable contact between the metal pipe 10 and the honeycomb structure 20 can be ensured. On the other hand, if the contact index X is less than 0, the tightening pressure of the metal pipe 10 against the honeycomb structure 20 is insufficient, so that a gap may be generated between the metal pipe 10 and the honeycomb structure 20.
The material for the metal pipe 10 forming the heat recovery member 100 preferably has heat resistance and corrosion resistance, although not particularly limited thereto. Examples of the metal pipe 10 include stainless steel pipes, copper pipes, brass pipes, titanium pipes, Ni alloy pipes, and Al alloy pipes. Among these, the stainless steel pipes are preferable from the viewpoint of heat resistance, corrosion resistance, and cost. Further, the metal pipe 10 may employ a jointed pipe in which two or more of the various types of pipes illustrated may be joined together.
The inner diameter of the straight portion 11 of the metal pipe 10 is smaller than the outer diameter of the honeycomb structure 20 in the state at the raw material stage (State A in
The outer shape of the honeycomb structure 20 is not particularly limited, and the cross section perpendicular to the axial direction (the extending direction of the cells 24) may be circular, elliptical, oval with a combination of circular arcs, quadrilateral, or other polygonal. Further, the honeycomb structure 20 may be of a hollow type having a hollow portion in the central portion in a cross section perpendicular to the axial direction.
Here, each of
The honeycomb structure 20 shown in
It should be noted that the shape of each cell 24 in the cross section perpendicular to the axial direction of the honeycomb structure 20 is not limited to the illustrated shape, and it may be a circle, an ellipse, a polygon such as a triangle, or the like.
A cell density (that is, the number of cells 24 per unit area) in the cross section of the honeycomb structure 20 perpendicular to the axial direction is not particularly limited. The cell density may be adjusted as needed depending on the applications and the like, and it may preferably be in a range of from 4 to 320 cells/cm2. The cell density of 4 cells/cm2 or more can sufficiently ensure the strength of the partition walls 25, hence the strength of the honeycomb structure 20 itself and effective GSA (geometrical surface area). Further, the cell density of 320 cells/cm2 or less can allow an increase in a pressure loss to be prevented when the fluid flows.
The thickness of the partition wall 25 of the honeycomb structure 20 may be appropriately designed depending on the purposes, and is not particularly limited. The thickness of the partition wall 25 is preferably 50 μm to 2 mm, and more preferably 60 μm to 600 μm. The thickness of the partition wall 25 of 50 μm or more can result in improved mechanical strength to prevent damages due to impact or thermal stress. On the other hand, the thickness of the partition wall 25 of 2 mm or less reduces a pressure loss of the fluid due to an increased proportion of the cell volume on the side of the honeycomb structure 20, so that the heat exchange efficiency can be improved.
The thicknesses of the outer peripheral wall 21 and the inner peripheral wall 26 of the honeycomb structure 20 may also be appropriately designed depending on the purposes, and are not particularly limited. When the heat recovery member 100 is used for general heat exchange applications, the thickness of each of the outer peripheral wall 21 and the inner peripheral wall 26 is 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. Moreover, when the heat recovery member 100 is used for a thermal storage application, the thickness of the outer peripheral wall 21 is preferably 10 mm or more, in order to increase a heat capacity of the outer peripheral wall 21.
Each of the outer peripheral wall 21, the partition walls 25 and the inner peripheral wall 26 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 outer peripheral wall 21, the partition walls 25 and the inner peripheral wall 26 may be 0%. The porosity of the outer peripheral wall 21, the partition walls 25 and the inner peripheral wall 26 of 10% or less can lead to improvement of thermal conductivity.
The honeycomb structure 20 is preferably based on ceramics. The phrase “based on ceramics” means that a ratio of a mass of ceramics to the total mass is 50% by mass or more.
The honeycomb structure 20 is preferably based on SiC (silicon carbide) having high thermal conductivity. The phrase “based on SiC (silicon carbide)” means that a ratio of a mass of SiC (silicon carbide) to the total mass is 50% by mass or more.
More particularly, the material of the honeycomb structure 20 that can be used herein includes Si—SiC materials such as Si-impregnated SiC and (Si+Al) impregnated SiC, metal composite SiC, recrystallized SiC, Si3N4, SiC, and the like. Among them, the Si—SiC material is preferably used, because it can be produced at a lower cost, and has high thermal conductivity.
The honeycomb structure 20 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 20 in such a range can lead to an improved heat conductive property and can allow the heat inside the pillar shaped ceramic body 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).
The honeycomb structure 20 preferably has an isostatic strength of more than 100 MPa, and more preferably 150 MPa or more, and more preferably 200 MPa or more. The isostatic strength of the honeycomb structure 20 of more than 100 MPa can lead to the honeycomb structure 20 having improved durability. The isostatic strength of the honeycomb structure 20 can be measured according to the method for measuring isostatic fracture strength as defied in the JASO standard M 505-87 which is a motor vehicle standard issued by Society of Automotive Engineers of Japan, Inc.
The honeycomb structure 20 can be produced by a method known in the art.
First, a green body containing ceramic powder is extruded into a desired shape to prepare a honeycomb formed body. At this time, the shape and density of the cells 24, the number, length and thickness of the partition walls 25, the shapes and the thicknesses of the outer peripheral wall 21 and the inner peripheral wall 26 and the like, can be controlled by selecting a die and jig in appropriate forms. The material of the honeycomb formed body that can be used herein includes the ceramics as described above. For example, when producing a honeycomb formed body based on a Si-impregnated SiC composite, a binder and water or an organic solvent can be added to a predetermined amount of SiC powder, and the resulting mixture can be kneaded to form a green body, which can be 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 20.
The method for producing the heat recovery member 100 according to the embodiment of the present invention is not particularly limited as long as it can produce the heat recovery member 100 having the above features, and can be performed according to a known interference fitting method.
Hereinafter, an example of the method for producing the heat recovery member 100 according to the embodiment of the present invention will be described.
In the method for producing the heat recovery member 100 according to the embodiment of the present invention, the metal pope 10 and the honeycomb structure 20 that satisfy the relationship of the following equation (3) are used as raw materials.
By using the metal pipe 10 and the honeycomb structure 20 that satisfy the relationship of the equation (3) above as raw materials, the metal pipe 10 is tightened and fixed (fixed by interference fitting) to the honeycomb structure 20 in the plastic deformation region of the metal pipe 10, so that the contact between the metal pipe 10 and the honeycomb structure 20 can be improved.
The method for producing the heat recovery member 100 according to the embodiment of the present invention includes a step of disposing the metal pipe 10, a step of heating the metal pipe 10, a step of disposing the honeycomb structure 20, and a step of cooling the metal pipe 10.
The step of disposing the metal pipe 10 is a step of disposing the metal pipe 10 such that one end of the metal pipe 10 is covered onto a plurality of protruding jigs installed at a bottom portion of a heating device.
Each protruding jig is a jig that has a function of determining the position of the honeycomb structure in the metal pipe 10 in addition to the position of the metal pipe 10 in the heating device. Therefore, each protruding jig has a structure for obtaining such a function. For example, each protruding jig has a width (horizontal length) smaller than an inner diameter of the straight portion 11 of the metal pipe 10 so that the one end of the metal pipe 10 can be covered. Also, it has a height (vertical length) corresponding to a predetermined position so that the honeycomb structure 20 can be arranged at the predetermined position in the straight portion 11 of the metal pipe 10. Furthermore, it has a width (horizontal length) smaller than the diameter of the honeycomb structure 20 so that the interference-fitted member can be removed after the interference fitting step.
The outer shape of each protruding jig can be set as needed depending on the shape of the metal pipe 10. For example, when the metal pipe 10 is cylindrical, the outer shape of the protruding jig may be various shapes such as a cylindrical shape or a prismatic shape, but the cylindrical shape is preferable. Further, when the metal pipe 10 has a rectangular cylindrical shape, the outer shape of the protruding jig may have various shapes such as a cylindrical shape or a prismatic shape, but the prismatic shape is preferable.
Each protruding jig preferably has a protruded portion that can be inserted into a hollow portion when the honeycomb structure 20 is of a hollow type. The use of each protruding jig having the protruded portion can provide easy accurate positioning of the honeycomb structure 20 in the interference fitting step.
The material of each protruding jig is not particularly limited as long as it is made of a material that can withstand the heating temperature during the interference fitting step. Examples of such a material include alumina and the like.
The step of heating the metal pipe 10 is a step of increasing the diameter of the straight portion 11 of the metal pipe 10 by heating. The heating temperature of the metal pipe 10 is not particularly limited as long as it is a temperature that allows the diameter of the metal pipe 10 to be increased, and it may be adjusted as needed depending on the type of the metal pipe 10. A typical heating temperature for the metal pipe 10 is 900 to 1200° C.
The step of disposing the honeycomb structure 20 is a step of disposing the honeycomb structure 20 at the straight portion 11 of the metal pipe 10 where the diameter has been increased by heating.
Since the protruding jig is installed at the bottom portion of the metal pipe 10 having the increased diameter, the honeycomb structure 20 can be disposed at a predetermined position in the straight portion 11 of the metal pipe 10. The honeycomb structure 20 can be arranged by fixing the second end face 23 to a tip of a drive device and driving the drive device in the vertical direction. The drive device is not particularly limited as long as it can be driven in the vertical direction.
The step of cooling the metal pipe 10 is a step of interference-fitting the straight portion 11 of the metal pipe 10 to the honeycomb structure 20 by cooling the metal pipe 10.
The method of cooling the metal pipe 10 is not particularly limited, and it may be natural cooling or forced cooling using a refrigerant or the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-036907 | Mar 2023 | JP | national |
