Gas–liquid two-phase heat exchange device and method for manufacturing same

Abstract

The present invention addresses the problem of providing a gas–liquid two-phase heat exchange device with high heat dissipation efficiency. As means for solving the problem, the present invention proposes a gas–liquid two-phase heat exchange device comprising at least a working fluid and a wick in an enclosure having an evaporation surface and a heat dissipation surface, wherein a wick having a porous structure (porous structure 2) formed by an element having a porous structure (porous structure 1) or a wick having a periodic structure formed by an element having a porous structure (porous structure 1) is used as the wick.

Description

Gas-liquid two-phase heat exchange device and method for manufacturing the same

[0001] The present invention relates to a gas-liquid two-phase heat exchange device that utilizes a phase change between gas and liquid, such as a heat pipe, vapor chamber, or loop heat pipe, and is particularly suitable for dissipating heat from a heat-generating body such as an electronic device.

[0002] Gas-liquid two-phase heat exchange devices are used as a means of dissipating heat from heat-generating elements such as electronic devices and motors. Vapor chambers, a representative example of a gas-liquid two-phase heat exchange device, diffuse locally generated heat, expanding the heat dissipation area and effectively dissipating heat from electronic devices. Heat from the heating element is transferred to the vapor chamber wall at the contact surface (including the point contact surface, also known as the evaporation surface) between the heating element and the vapor chamber, where the heat evaporates the working fluid enclosed within the vapor chamber. The latent heat of evaporation transfers thermal energy to the vapor, and the mass transfer of the vapor accelerates the transfer of thermal energy. Meanwhile, vapor chambers have a heat dissipation surface located away from the contact surface with the heating element. The vapor condenses and returns to liquid through heat exchange at the heat dissipation surface. The volume change between the gas and liquid at this time further accelerates the mass transfer of the vapor. The working fluid, once liquid, moves from the heat dissipation surface to the evaporation surface using the capillary force of a wick attached to the inner wall of the vapor chamber. At this time, the vaporization of the working fluid on the evaporation surface promotes the movement of the working fluid within the wick. At this time, the vaporization of the working fluid on the evaporation surface and in the vicinity of the evaporation surface promotes the movement of the working fluid within the wick. Heat transfer in gas-liquid two-phase heat exchange devices is carried out through this cycle of evaporation, diffusion, condensation, and reflux.

[0003] The performance of a gas-liquid two-phase heat exchange device is determined by how efficiently and effectively this cycle is carried out, and the role of the wick, which plays a part in the reflux of the working liquid, is extremely important. For example, Patent Document 1 discloses a wick structure, and Patent Document 2 discloses a porous wick.

[0004] JP 2020-57794 A JP 2023-70147 A

[0005] However, the heat dissipation efficiency of conventional gas-liquid two-phase heat exchange devices is not necessarily sufficient, and to handle the heat generated by the increasing sophistication of electric vehicles and electronic devices, gas-liquid two-phase heat exchange devices are required to have even higher heat dissipation efficiency.Therefore, a wick that can improve the heat dissipation efficiency of gas-liquid two-phase heat exchange devices has been desired.

[0006] Therefore, an object of the present invention is to provide a gas-liquid two-phase heat exchange device with high heat dissipation efficiency.

[0007] The gas-liquid two-phase heat exchange device of the present invention, which solves the above problems, has the following configuration. [1] A gas-liquid two-phase heat exchange device including at least a working fluid and a wick housed within a housing having an evaporation surface and a heat dissipation surface, wherein the wick has a porous structure (porous structure 2) composed of elements having a porous structure (porous structure 1) or a periodic structure composed of elements having a porous structure (porous structure 1). [2] The gas-liquid two-phase heat exchange device according to [1], wherein the wick and the inner wall of the housing are integrated on the evaporation surface. [3] The gas-liquid two-phase heat exchange device according to [1] or [2], wherein the heat dissipation surface includes heat dissipation fins integrated with the outer wall of the housing. [4] The gas-liquid two-phase heat exchange device according to [3], wherein the outer wall of the housing integrated with the heat dissipation fins has a heat dissipation surface and a space within the fins that allows the gaseous working fluid to reach the heat dissipation surface. [5] The gas-liquid two-phase heat exchange device according to any one of [1] to [4], characterized in that the average pore diameter of the porous structure 1 is 1 μm to 1000 μm and the average pore diameter of the porous structure 2 is 100 μm to 10 mm. [6] The gas-liquid two-phase heat exchange device according to any one of [1] to [5], characterized in that the inner surface side of the housing of the wick is composed only of elements having a porous structure (porous structure 1). [7] The gas-liquid two-phase heat exchange device according to any one of [4] to [6], characterized in that only elements having a porous structure (porous structure 1) are provided on the wall surface of the internal space of the heat dissipation fin, the porous structure is integrated with the wick according to claim 1 or claim 2 at a lower part of the internal space of the fin, and at least the evaporation surface of the wick is composed only of elements having a porous structure (porous structure 1).[8] The gas-liquid two-phase heat exchange device according to any one of [1] to [7], wherein the heat dissipation surface includes a heat dissipation fin integrated with the outer wall of the housing, the outer wall of the housing integrated with the heat dissipation fin has a heat dissipation surface and a space within the fin through which the gas working fluid can reach the heat dissipation surface, a wick is also disposed within the space, and the inner surface side of the wick of the housing is composed only of elements having a porous structure (porous structure 1). [9] A method for manufacturing the gas-liquid two-phase heat exchange device according to any one of [1] to [8], wherein an additive manufacturing method is used, the additive manufacturing method including a step of applying melting energy to raw materials to melt and solidify the raw materials, wherein the melting energy per unit volume when forming the porous structure (porous structure 1) is lower than the melting energy used to form the housing, and the porous structure 2 or the periodic structure is formed by controlling the locations where the raw materials are applied and bonded based on three-dimensional model data stored in the apparatus.

[0008] According to the present invention, a gas-liquid two-phase heat exchange device with high heat dissipation efficiency is provided.

[0009] 1A and 1B are three-sided views illustrating an example of a gas-liquid two-phase heat exchange device of the present invention, where (a) is a bottom view, (b) is a front view, and (c) is a side view. Cross-sectional views of the gas-liquid two-phase heat exchange device of FIG. 1, where (a) is an A-A' cross-sectional view and (b) is a B-B' cross-sectional view. A perspective view illustrating an example of the shape of a wick in a gas-liquid two-phase heat exchange device of the present invention. A perspective view illustrating another example of the shape of a wick in a gas-liquid two-phase heat exchange device of the present invention. A perspective view illustrating another example of the shape of a wick in a gas-liquid two-phase heat exchange device of the present invention. A partially enlarged schematic cross-sectional view illustrating an example of the boundary between a housing and a wick in a gas-liquid two-phase heat exchange device of the present invention. A cross-sectional view illustrating an example of a housing of a gas-liquid two-phase heat exchange device of the present invention provided with fins. A cross-sectional view illustrating another example of a housing of a gas-liquid two-phase heat exchange device of the present invention provided with fins. A cross-sectional view illustrating an example of a gas-liquid two-phase heat exchange device of the present invention provided with fins. A cross-sectional view illustrating another example of a gas-liquid two-phase heat exchange device of the present invention provided with fins. 11 is a cross-sectional view showing another example of the gas-liquid two-phase heat exchange device of the present invention provided with fins. FIG. 12 is a cutaway perspective cross-sectional view of the gas-liquid two-phase heat exchange device of FIG.

[0010] The inventors have discovered that the rate-limiting factors for the heat dissipation efficiency of conventional gas-liquid two-phase heat exchange devices are interference between the evaporated working fluid on the evaporation surface and the returning liquid working fluid, interference between the evaporated working fluid and the condensed liquid working fluid on the heat dissipation surface, and interference between the evaporated and diffusing vapor and the liquid working fluid in the intermediate region. That is, they have discovered that on the evaporation surface, the diffusion and movement of the vaporized working fluid is hindered by the liquid working fluid covering the evaporation surface, preventing the movement of the gaseous working fluid from the wick to the movement space, that on the heat dissipation surface, the liquefied working fluid covering the heat dissipation surface prevents the migrated gaseous working fluid from approaching the heat dissipation surface, and that in the intermediate region, when the working liquid condensed on the heat dissipation surface returns to the evaporation surface between the wicks by capillary force, it interferes with the evaporated vapor on the evaporation surface, preventing the uniform diffusion of the vapor within the housing and the reflux of the working liquid to the evaporation surface.

[0011] Based on this knowledge, the present inventors have conducted extensive research and have invented a gas-liquid two-phase heat exchange device with improved heat dissipation efficiency.

[0012] The gas-liquid two-phase heat exchange device of the present invention comprises at least a working fluid and a wick housed within a housing having an evaporation surface and a heat dissipation surface. The housing can be a sealed space and is configured to prevent the vaporized working fluid from dissipating to the outside. It may also have a port for refilling the working fluid as needed. Furthermore, in a loop heat pipe, the housing may be divided into an evaporation section and a heat dissipation section, connected by a pipe to allow the gas and liquid to circulate. The housing should also be strong enough to absorb the increase in pressure inside the housing due to the vaporized working fluid. From the perspective of thermal conductivity, the housing is generally made of metal. The material for the housing is not particularly limited, but materials containing elements with high thermal conductivity, such as copper or aluminum, are suitable. The housing, including the fin portion, and the wick may be made of resin, as long as the material is resistant to the working fluid.

[0013] The housing also has an evaporation surface and a heat dissipation surface. The evaporation surface is the surface intended to come into contact with the heating element (for example, the surface corresponding to the portion of the housing where the heating element 1 contacts in FIG. 1 ), and the heat dissipation surface is the surface for dissipating the heat of condensation generated when the vaporized working fluid liquefies to the outside. Since no heat transfer occurs from the heating element other than the evaporation surface, the heat dissipation surface can be considered a surface other than the evaporation surface. However, since heat transfer also occurs through the housing wall, it is advantageous to dissipate heat at the location on the inner surface of the housing farthest from the evaporation surface. Furthermore, the heat dissipation surface may be provided on the outer wall side of the housing with a structure such as a fin to promote heat dissipation, or with a cooling structure such as a fan, Peltier element, or coolant heat exchange device.

[0014] Furthermore, the working fluid (not shown) placed inside the housing is not particularly limited as long as it is a liquid substance that can be vaporized by heat transferred from the heating element through the wall of the housing, and the substance to be used can be selected depending on the environment in which it is used.Preferred working fluids include, for example, water, alcohols such as ethanol, acetone, ammonia, etc.

[0015] The gas-liquid two-phase heat exchange device of the present invention has a wick 3 within a housing, and the wick has a porous structure (porous structure 2 (see FIG. 2)) composed of elements having a porous structure (porous structure 1 (see FIG. 2)), i.e., the material forming the porous structure further has a porous structure, or the wick has a periodic structure composed of elements having a porous structure (porous structure 1). By having such a wick, the gas-liquid two-phase heat exchange device of the present invention can efficiently achieve evaporation (vaporization) of the working fluid on the evaporation surface, diffusion of the vaporized working fluid, condensation of the vaporized working fluid on the heat dissipation surface, and movement (reflux) of the condensed working fluid from the heat dissipation surface to the evaporation surface.

[0016] The wick used in the present invention has a portion formed by an element having a porous structure (for convenience, referred to as "porous structure 1"). To explain the element having porous structure 1, a structure is a material that is shaped to have a certain shape, but the element having a porous structure in the present invention means that the material that forms the structure itself has a porous structure.

[0017] In a first embodiment of the wick used in the present invention, an object formed using elements having the porous structure 1 has a porous structure (for convenience, referred to as "porous structure 2"). For example, there are an embodiment in which a three-dimensional mesh structure is formed by the elements, and the gaps in the mesh form a porous structure (see FIG. 3), an embodiment in which a periodic curved structure is continuously formed in a three-dimensional direction, as represented by a gyroid structure, an embodiment in which the elements form a lattice-like structure branched into branches to form a three-dimensional structure, and a embodiment in which a periodic lattice structure is continuously formed in a three-dimensional direction, as represented by a lattice structure, and a combination of these embodiments.

[0018] A second embodiment of the wick used in the present invention has a periodic structure composed of elements having a porous structure (porous structure 1). The elements having a porous structure (porous structure 1) are as described above. The periodic structure refers to a one-dimensional periodic structure or a two-dimensional periodic structure, such as a structure in which rectangular columns or cylinders are periodically arranged in two dimensions (see FIG. 5), a honeycomb structure in which rectangular holes or circular holes are periodically arranged in two dimensions, or a combination of these structures. In either case, the wick may have a structure that promotes the movement of gas in the planar direction, such as through holes in the columns or walls.

[0019] In the present invention, porous structure 1 serves exclusively as a path through which liquefied working fluid passes, while porous structure 2 serves exclusively as a path through which gaseous working fluid passes. That is, by using porous structure 2 as a large structure as a path through which gaseous working fluid passes and porous structure 1 as a small structure as a path through which liquid working fluid passes, the vaporized working fluid can quickly move from the evaporation surface to the movement space. Meanwhile, the liquefied working fluid moves to porous structure 1, which is advantageous in terms of capillary action, while the vaporized working fluid easily accesses the heat dissipation surface through porous structure 2. That is, by using such a structure, a spatial separation effect can be achieved between the movement of gaseous working fluid and the movement of liquid working fluid. Therefore, the average pore diameter of porous structure 1 is smaller than that of porous structure 2, but the average pore diameter of porous structure 1 is preferably 1 μm to 1000 μm, more preferably 5 μm to 100 μm. The average pore diameter of porous structure 2 is preferably 100 μm to 10 mm, and more preferably 300 μm to 5 mm. Although there is some overlap in the preferred average pore diameters between porous structure 1 and porous structure 2, since capillary action is dominant on the side with smaller pore diameters, it is important to keep the average pore diameter of porous structure 1 smaller than the average pore diameter of porous structure 2. The average pore diameter can be measured by mercury intrusion porosimetry, micro X-ray CT, or the like.

[0020] In addition, as in the prior art, when a three-dimensional network structure is formed using elements that do not have porous structure 1, and the gaps in the network are made porous, two or more pore size distributions can be observed when the porous structure splits the peak. However, such a configuration is disadvantageous in terms of the transfer efficiency of the gaseous or liquid working fluid because the elements that form the porous structure do not have a migration path for the working fluid. That is, the space used for the migration of the gaseous working fluid is invaded by the space used for the migration of the liquid working fluid, and the separation of the migration path is also insufficient. That is, in the wick used in the present invention, the elements that constitute porous structure 2 have porous structure 1, so that the liquid working fluid that has penetrated into the mesh of porous structure 2 can move into the mesh of porous structure 1, thereby preventing the migration of the gaseous working fluid from being hindered by the liquid working fluid.

[0021] Furthermore, as explained above, interference in the movement of the gaseous working fluid and the liquid working fluid occurs at the evaporation surface and the heat dissipation surface. Therefore, the first and second aspects of the wick may be provided in the wick present on the inner wall of the housing corresponding to the evaporation surface and / or the wick present on the inner wall of the housing corresponding to the heat dissipation surface, and preferably at least on the inner wall of the housing corresponding to the evaporation surface. Furthermore, the wick present on the inner wall of the housing between the evaporation surface and the heat dissipation surface does not necessarily have to have porous structure 1 or porous structure 2; it is sufficient that the wick is capable of transferring the liquid working fluid by capillary action. From this perspective, it is sufficient that the average pore diameter of the wick present on the inner wall of the housing between the evaporation surface and the heat dissipation surface is approximately the same as the average pore diameter described for porous structure 1.

[0022] Furthermore, the wick used in the present invention preferably has a structure in which, at least on the heat dissipation surface, a layer having only the porous structure 1 (for convenience, referred to as the "second layer" (see reference numeral 31 in Figure 9)) is laminated on the inner wall side of the housing of a layer having the first embodiment of the wick and / or the second embodiment of the wick (for convenience, referred to as the "first layer"). Having such a structure further promotes vaporization of the working fluid on the evaporation surface and further promotes the movement of the condensed working fluid on the heat dissipation surface. The second layer should be thick enough to prevent interference between the movement of the liquid working fluid and the movement of the gaseous working fluid. The upper limit varies depending on factors such as the latent heat of vaporization of the working fluid and the temperature of the heat-generating surface, but is preferably 1000 μm or less. Furthermore, the first and second layers are preferably integrated to allow smooth heat transfer between the layers. The meaning of "integrated" here is the same as that explained below.

[0023] Furthermore, considering that heat transfer from the heating element occurs through the housing wall surface, it is preferable that the wick used in the present invention be integrated with the housing inner wall at least at the evaporation surface. Here, "integrated" means that there is no boundary surface between the inner wall and the wick, as shown in the schematic cross-sectional view of Figure 6. For example, when made of metal, the inner wall and the wick are fused together and no boundary surface is observed when observing the cross section. This structure eliminates resistance at the boundary surface, which is extremely advantageous in terms of thermal conductivity. An integrated structure can be achieved, for example, by the construction method described below.

[0024] Furthermore, the gas-liquid two-phase heat exchange device of the present invention preferably includes heat dissipation fins 4 integrated into the outer wall of the housing on the heat dissipation surface side, as shown in Figure 7. This configuration can help dissipate heat transferred through the inner wall of the housing to the outside. In a preferred embodiment of the present invention, the outer wall of the housing integrated with the heat dissipation fins preferably has a heat dissipation surface inside the fins that comes into contact with the wick used in the present invention and a space within which the gaseous working fluid can reach the heat dissipation surface. This configuration can ensure a wide heat dissipation surface and is also extremely advantageous in terms of heat dissipation to the outside.

[0025] Furthermore, as shown in FIG. 8, the fins 4 preferably have a hollow structure, with the hollow portion communicating with the internal space of the housing. It is also preferable to form a wick within the hollow portion, as shown in FIG. 9. On the other hand, thinner fins are considered advantageous in terms of allowing more fins to be installed and improving the heat dissipation effect. However, it is expected that the hollow portion of the fin will be narrow. In such a case, as shown in FIG. 10, it is preferable to not form a wick within the space within the fin 4, or to provide a thin porous structure 1 (reference numeral 32) on the inner wall of the fin to ensure space through which vapor can move. The latter embodiment is particularly preferable because the movement of the liquid working fluid on the inner wall of the fin can be achieved by utilizing capillary action.

[0026] Furthermore, as shown in Figures 11 and 12, a preferred embodiment is one in which the wick in the portion other than the fin internal space is replaced with a porous structure (porous structure 2) composed of elements having a porous structure (porous structure 1) and instead is composed of a periodic structure composed of elements having a porous structure (porous structure 1). In the embodiment shown in Figures 11 and 12, the liquid working fluid liquefied in the fin internal space can return to the evaporation surface without straying, thereby improving cooling efficiency. Furthermore, in the embodiment shown in Figures 11 and 12, the second layer described above is also provided on the surface of the casing on the evaporation surface side, thereby promoting the movement of the liquid working fluid that has migrated through the periodic structure composed of elements having a porous structure (porous structure 1) along the casing wall surface. The external shape of the fin is not particularly limited, but possible structures include one-dimensional periodic structures such as plate-type structures, two-dimensional periodic structures such as pin-type structures, and three-dimensional periodic structures such as lattice structures and gyroid structures, as well as combinations thereof. Such complex structures, which are integrated into the outer wall of the casing and further have an internal structure, can be realized, for example, by the construction method described below.

[0027] Next, a method for obtaining a gas-liquid two-phase heat exchange device of the present invention will be described using examples. However, the present invention should not be construed as being limited by the following description. A porous structure (porous structure 2) composed of elements having a porous structure (porous structure 1), or a periodic structure composed of elements having a porous structure (porous structure 1), can be fabricated, for example, by additive manufacturing. Selective laser melting deposition modeling (SELF) using metal powder is particularly suitable. In SELECTF, three-dimensional CAD data representing the shape of the gas-liquid two-phase heat exchange device is created, and this data is used to divide the device into thin layers, obtaining two-dimensional slice data for each layer. The two-dimensional slice data includes data corresponding to at least three parts: data corresponding to the housing, data corresponding to the wick, and data corresponding to the space. The laser irradiation position and output are selectively controlled based on this data. The raw material is supplied at a thickness corresponding to the thickness of the divided layers. For example, if a 10 mm heat exchange device is divided into 100 layers with a layer thickness of 0.1 mm, the raw material is also supplied so that the layers are stacked 0.1 mm apart. In the melting process, the raw material is irradiated with a laser to melt and solidify, forming the shape layer by layer. This manufacturing method forms a structure by repeatedly performing this process for each slice data, stacking each layer one by one. In the gas-liquid two-phase heat exchange device of the present invention, two structures must be realized: the housing is an airtight structure that does not allow liquid or gas to pass through in order to enclose the working fluid, and porous structure 1 is a porous structure that is not airtight so that the working liquid can permeate. These can be created by controlling the energy density of the laser irradiation. Furthermore, complex three-dimensional structures such as porous structure 2 can be realized by controlling the position of laser irradiation using slice data. Furthermore, using this method, it is easy to obtain a state in which the inner wall of the housing and the wick are integrated.

[0028] The parts other than the wick can be manufactured by referring to known methods.

[0029] An additive manufacturing method was used to fabricate an aluminum alloy gas-liquid two-layer heat exchange device having the structure shown in FIG. 1 . This gas-liquid two-layer heat exchange device had no interface between the housing and the wick, as shown in FIG. 6 . Furthermore, an additive manufacturing method was used to fabricate an aluminum alloy gas-liquid two-layer heat exchange device having the structure shown in FIG. 11 . That is, a wick (wick 1) with porous structure 1 was formed on the inner wall of the fins and the housing wall surface (including the top and bottom surfaces), and columnar wicks (wick 2) with porous structure 1 were periodically arranged to connect between the fins on the top surface of the housing and between the bottom surface of the housing. This gas-liquid two-layer heat exchange device had no interface between the housing and the wick, and no interface existed between wick 1 and wick 2. In the former gas-liquid two-layer heat exchange device, a heat source was placed in contact with the vicinity of a corner of the bottom surface, and in the latter gas-liquid two-layer heat exchange device, with the heat source being placed in contact with the center of the bottom surface, and the heat dissipation efficiency of each was examined.It was confirmed that in both cases an interface exists between the housing and the wick according to conventional technology, and that the heat dissipation efficiency is superior to that of a gas-liquid two-layer heat exchange device that does not have a porous structure 2.

[0030] 1 Heating element 2 Housing 3 Wick 31 Wick portion (second layer) composed only of elements having the porous structure 1 32 Wick portion present in the fin composed only of elements having the porous structure 1 33 Wick portion present on the housing inner wall composed only of elements having the porous structure 1 4 Fin 101 Gas-liquid two-phase heat exchange device

Claims

1. A gas-liquid two-phase heat exchange device comprising at least a working fluid and a wick within a housing having an evaporation surface and a heat dissipation surface, wherein the wick has a porous structure (porous structure 2) composed of elements having a porous structure (porous structure 1), or a periodic structure composed of elements having a porous structure (porous structure 1).

2. The gas-liquid two-phase heat exchange device according to claim 1, wherein the wick and the inner wall of the housing are integrated on the evaporation surface.

3. A gas-liquid two-phase heat exchange device according to claim 1 or 2, characterized in that the heat dissipation surface is provided with heat dissipation fins integrated into the outer wall of the housing.

4. A gas-liquid two-phase heat exchange device as described in claim 3, characterized in that the outer wall of the housing integrated with the heat dissipation fins has a heat dissipation surface inside the fins and a space that allows the gaseous working fluid to reach the heat dissipation surface.

5. A gas-liquid two-phase heat exchange device as described in claim 1 or 2, characterized in that the average pore diameter of the porous structure 1 is 1 μm to 1000 μm, and the average pore diameter of the porous structure 2 is 100 μm to 10 mm.

6. A gas-liquid two-phase heat exchange device as described in claim 1 or 2, characterized in that the inner surface of the housing of the wick is composed only of elements having a porous structure (porous structure 1).

7. A gas-liquid two-phase heat exchange device as described in claim 4, characterized in that only elements having a porous structure (porous structure 1) are provided on the wall surface of the internal space of the heat dissipation fin, and the porous structure is integrated with the wick described in claim 1 or claim 2 at the bottom of the internal space of the fin, and at least on the evaporation surface, the inner surface side of the housing of the wick is composed only of elements having a porous structure (porous structure 1).

8. A gas-liquid two-phase heat exchange device as described in claim 1 or 2, characterized in that the heat dissipation surface is provided with heat dissipation fins integrated into the outer wall of the housing, the outer wall of the housing into which the heat dissipation fins are integrated has a heat dissipation surface and a space inside the fins that allows the gaseous working fluid to reach the heat dissipation surface, a wick is also arranged within this space, and the inner surface side of the wick of the housing is composed only of elements having a porous structure (porous structure 1).

9. A method for manufacturing a gas-liquid two-phase heat exchange device according to claim 1 or 2, using an additive manufacturing method including a step of applying melting energy to raw materials to melt and solidify the raw materials, wherein the melting energy per unit volume used to form the porous structure (porous structure 1) is lower than the melting energy used to form the housing, and wherein porous structure 2 or the periodic structure is formed by controlling the locations where the raw materials are applied and bonded based on three-dimensional model data stored in the device.

Images