Heat transfer system

Abstract

To provide a heat transfer system having superior heat exchange efficiency.SOLUTION: A heat transfer system comprises a flow passage where fluid circulates, the flow passage includes a flow passage wall defining an internal space where the fluid circulates and a metal porous body provided on the internal space, and the metal porous body is made of metal having a plurality of pores formed, at least some of the pores are open pores, and the metal is a metal made of a metal element selected from the first group of aluminum, magnesium, copper, silver, and gold, a metal in a composite state of two kinds or more of metal element selected from the first group, an alloy consisting of one kind or more of metal elements selected from the first group and one kind or more of elements selected from the second group of iron, cobalt, chromium, nickel, manganese, tin, zinc, silicon, phosphorus, carbon, boron, scandium, molybdenum, tungsten, and titanium, or a metal in a composite state of one kind or more of metal element selected from the first group and one kind or more of element selected from the second group.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to heat transfer systems. [Background technology]

[0002] In heat transfer systems that use fluids as heat transport media, such as boilers, air conditioners, and radiators, the method of transferring heat between a high-temperature medium and a low-temperature medium, called heat exchange, in which heat is transferred from the high-temperature side to the low-temperature side via a highly thermally conductive material, is commonly used and is used for a variety of purposes.

[0003] In order to improve the heat exchange efficiency of a heat exchanger, a technique of providing a metal porous body as a heat transfer member in a fluid flow path has been considered (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2014 / 132528 [Patent Document 2] International Publication No. 2017 / 038380 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, the demand for energy conservation has been increasing, and there is a demand for further improvement in the heat exchange efficiency of heat transfer systems.

[0006] Therefore, an object of the present disclosure is to provide a heat transfer system having excellent heat exchange efficiency. [Means for solving the problem]

[0007] The heat transfer system of the present disclosure comprises: A flow path through which a fluid flows is provided, The flow path is A flow path wall defining an internal space through which the fluid flows; A metal porous body provided in the internal space, The metal porous body is made of a metal having a plurality of pores formed therein, At least a portion of the pores are open pores, The metal is a metal consisting of one metallic element selected from the first group consisting of aluminum, magnesium, copper, silver and gold; An alloy consisting of two or more metal elements selected from the first group; A metal in a composite state of two or more metal elements selected from the first group, An alloy comprising one or more metal elements selected from the first group and one or more elements selected from a second group consisting of iron, cobalt, chromium, nickel, manganese, tin, zinc, silicon, phosphorus, carbon, boron, scandium, molybdenum, tungsten and titanium; or, The metal is a composite of one or more metal elements selected from the first group and one or more elements selected from the second group, The minimum pore size of the pores of the metal porous body is 10 μm or more; The maximum pore size of the pores of the metal porous body is 420 μm or less, The porosity of the metal porous body is 60% or more and 85% or less, The transmittance of the porous metal body is 0.6×10 -12 m 2 That is the heat transfer system. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a heat transfer system having excellent heat exchange efficiency. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a typical configuration example of a heat transfer system according to the first embodiment. [Diagram 2]FIG. 2 is a diagram showing the vicinity of the heat receiving area of ​​the heat transfer system according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described. (1) The heat transfer system of the present disclosure comprises: A flow path through which a fluid flows is provided, The flow path is A flow path wall defining an internal space through which the fluid flows; A metal porous body provided in the internal space, The metal porous body is made of a metal having a plurality of pores formed therein, At least a portion of the pores are open pores, The metal is a metal consisting of one metallic element selected from the first group consisting of aluminum, magnesium, copper, silver and gold; An alloy consisting of two or more metal elements selected from the first group; A metal in a composite state of two or more metal elements selected from the first group, An alloy comprising one or more metal elements selected from the first group and one or more elements selected from a second group consisting of iron, cobalt, chromium, nickel, manganese, tin, zinc, silicon, phosphorus, carbon, boron, scandium, molybdenum, tungsten and titanium; or, The metal is a composite of one or more metal elements selected from the first group and one or more elements selected from the second group, The minimum pore size of the pores of the metal porous body is 10 μm or more; The maximum pore size of the pores of the metal porous body is 420 μm or less, The porosity of the metal porous body is 60% or more and 85% or less, The transmittance of the porous metal body is 0.6×10 -12 m 2 That is the heat transfer system.

[0011] According to the present disclosure, it is possible to provide a heat transfer system having excellent heat exchange efficiency.

[0012] (2) In the above (1), the thermal conductivity of the metal may be 100 W / mK or more. This further improves the heat exchange efficiency of the heat transfer system.

[0013] (3) In the above (1) or (2), the transmittance of the porous metal body is 0.8×10 -12 m 2 This further improves the heat exchange efficiency of the heat transfer system.

[0014] (4) In any one of the above (1) to (3), the open porosity of the pores of the metal porous body may be 60% or more, thereby reducing the flow resistance of the fluid.

[0015] (5) In any one of the above (1) to (4), a fluid filled in the internal space; A pump that circulates the fluid in a predetermined flow direction, The flow path is a heat receiving region in which the fluid receives heat from the outside of the internal space; and a heat dissipation region where the fluid dissipates heat to the outside of the internal space.

[0016] This further improves the heat exchange efficiency of the heat transfer system.

[0017] (6) In the above (5), a heating unit is provided outside the internal space and applies heat to the fluid present in the heat receiving area, The metal porous body may be provided in the heat-receiving area.

[0018] This further improves the heat exchange efficiency of the heat transfer system.

[0019] (7) In any one of the above (1) to (6), the inner wall of the flow path and the metal porous body may be in contact with each other, thereby further improving the heat exchange efficiency of the heat transfer system.

[0020] (8) In the above (5) or (6), a cooling unit may be provided outside the internal space to remove heat from the fluid present in the heat dissipation area, thereby further improving the heat exchange efficiency of the heat transfer system.

[0021] [Details of the embodiment of the present disclosure] Specific examples of the heat transfer system of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0022] In this specification, the expression "A to B" means the upper and lower limits of a range (i.e., A or more and B or less). When no unit is specified for A and a unit is specified only for B, the unit of A and the unit of B are the same.

[0023] In the present specification, when a compound or the like is represented by a chemical formula, unless the atomic ratio is particularly limited, it is understood to include any conventionally known atomic ratio, and is not necessarily limited to only those within the stoichiometric range, but includes any conventionally known atomic ratio.

[0024] In the present disclosure, when one or more numerical values ​​are described as the lower limit and the upper limit of a numerical range, a combination of any one numerical value described as the lower limit and any one numerical value described as the upper limit is also disclosed. For example, when a1 or more, b1 or more, and c1 or more are described as the lower limit, and a2 or less, b2 or less, and c2 or less are described as the upper limit, a1 or more and a2 or less, a1 or more and b2 or less, a1 or more and c2 or less, b1 or more and a2 or less, b1 or more and b2 or less, b1 or more and c2 or less, c1 or more and a2 or less, c1 or more and b2 or less, and c1 or more and c2 or less are disclosed.

[0025] [Embodiment 1: Heat transfer system] The configuration of a heat transfer system according to an embodiment of the present disclosure (hereinafter also referred to as "this embodiment" or "embodiment 1") will be described with reference to Fig. 1. The heat transfer system 1 of embodiment 1 includes a flow path 3 through which a fluid 2 flows. The flow path 3 includes a flow path wall 3a that defines an internal space 3c through which the fluid 2 flows, and a porous metal body 4 provided in the internal space 3c.

[0026] The heat transfer system 1 may further include a fluid 2 filled in the internal space 3c of the flow path 3. The heat transfer system 1 may further include a pump 5 that circulates the fluid 2 in a predetermined flow direction.

[0027] The flow path 3 may include a heat receiving area 6, which is an area where the fluid 2 receives heat from outside the internal space 3c of the flow path 3, and a heat dissipation area 7, which is an area where the fluid 2 releases heat to the outside of the internal space 3c.

[0028] The heat transfer system 1 may further include a heating unit 8 that is provided outside the internal space 3c and provides heat to the fluid 2 present in the heat receiving area 6. In this embodiment, the heat receiving area 6 is an area facing the heating unit 8 in the flow path 3.

[0029] The heat transfer system 1 may further include a cooling unit 9 provided outside the internal space 3c and configured to remove heat from the fluid 2 present in the heat dissipation region 7. In this embodiment, the heat dissipation region 7 is a region of the flow path 3 facing the cooling unit 9.

[0030] The metal porous body 4 of the first embodiment has high thermal conductivity and high transmittance. Therefore, when the metal porous body 4 is used in a heat transfer system, the efficiency of heat exchange between the fluid and the heat source and / or between the fluid and the cooling source can be improved. The reason for this will be explained with reference to FIG. 2.

[0031] Fig. 2 is a diagram for explaining the principle of heat exchange of a fluid using the porous metal body 4 of the first embodiment. In Fig. 2, the flow path 3 includes a flow path wall 3a and an internal space 3c defined by the flow path wall 3a. The internal space 3c is filled with a fluid 2. The porous metal body 4 is provided in a part of the internal space 3c. A heating unit 8, which is a heat source, is provided outside the internal space 3c. The porous metal body 4 and the heating unit 8 are provided at positions facing each other.

[0032] 2, the porous metal body 4 is provided at a position facing the heating unit 8, and therefore the porous metal body 4 is heated by the heating unit 8. When a driving force is applied to the fluid 2 in the direction of arrow F1 to pass through the porous metal body 4, heat exchange occurs between the fluid 2 and the heating unit 8 via the porous metal body 4.

[0033] The thermal conductivity of the porous metal body of the first embodiment is higher than that of typical fluids (e.g., water, radiator liquid) used in heat transfer systems. Therefore, in the flow path 3 in which the porous metal body 4 is provided in the internal space 3c, heat from the heating unit 8 is easily transferred to the fluid 2 through the porous metal body 4. In other words, the presence of the porous metal body 4 improves the efficiency of heat exchange between the fluid 2 and the heating unit 8.

[0034] On the other hand, when the metal porous body 4 is provided in the internal space 3c, the metal porous body 4 increases the movement resistance (pressure loss) of the fluid 2, and the flow rate of the fluid 2 in the direction of the arrow F1 after passing through the metal porous body 4 tends to decrease. If the flow rate in the direction of the arrow F1 decreases, the heat exchange efficiency between the fluid 2 and the heating unit 8 decreases. Since the metal porous body 4 of the first embodiment has a high permeability, the effect of the increase in the amount of heat transfer due to the large specific surface area (positive effect on the heat exchange efficiency) is greater than the effect of the decrease in flow rate due to the increase in movement resistance (negative effect on the heat exchange efficiency), and the heat exchange efficiency can be improved. Therefore, the amount of decrease in the flow rate due to the provision of the metal porous body 4 is suppressed. Therefore, by using the metal porous body 4 of the first embodiment, the heat exchange efficiency between the fluid 2 and the heating unit 8 is improved overall.

[0035] FIG. 2 shows a configuration in which the heating unit 8 is provided outside the internal space 3c, but instead of the heating unit 8, a cooling unit that is a cooling source can be provided, and the metal porous body 4 can be provided at a position facing the cooling unit. In this case, the metal porous body 4 is cooled by the cooling unit, and the heat of the fluid 2 is easily released to the outside of the internal space 3c through the metal porous body 4. That is, the presence of the metal porous body 4 improves the efficiency of heat exchange between the fluid 2 and the cooling unit. A heat source and a cooling unit can be provided at different positions outside the internal space 3c, and the metal porous body 4 can be provided at positions facing each of them. A pump can also be provided in the flow path as a configuration that gives a driving force to the fluid. The heating unit and the cooling unit may be something like a heat sink or a metal case, or may be a fluid such as a liquid or gas.

[0036] <Flow path> In the heat transfer system 1 of this embodiment, the flow path 3 includes a flow path wall 3a that defines an internal space 3c through which the fluid 2 flows, and a metal porous body 4 provided in the internal space 3c. The flow path 3 includes a heat receiving region 6 that is a region where the fluid 2 receives heat from the outside of the internal space 3c, and a heat dissipation region 7 that is a region where the fluid 2 dissipates heat to the outside of the internal space 3c.

[0037] The internal space 3c of the flow path 3 may form at least one closed loop. The closed loop may have a branch within one closed loop. The internal space 3c of the flow path 3 may form a plurality of closed loops arranged in parallel. When the internal space 3c of the flow path 3 forms a closed loop, the fluid 2 circulates within the flow path 3.

[0038] The flow channel wall 3a of the flow channel 3 may have an opening that connects the internal space 3c with the external space of the flow channel 3. In this case, the fluid 2 can move between the internal space 3c and the external space.

[0039] There is no particular limitation on the shape of the flow channel 3, and any conventionally known shape may be used. For example, the flow channel 3 may be tubular with a tubular flow channel wall, or may have a shape in which an internal space 3c is formed within a flow channel wall having any shape (such as a plate shape or a rectangular parallelepiped shape).

[0040] The cross-sectional shape of the internal space 3c in a cross section perpendicular to the flow direction of the fluid 2 is not particularly limited. For example, the cross-sectional shape may be circular, elliptical, or rectangular. The area of ​​the cross section is not particularly limited and may be appropriately changed depending on the application.

[0041] The material of the flow path wall 3a of the flow path 3 can be appropriately selected taking into consideration the resistance to fluid, thermal conductivity, heat insulation, etc. For example, a fluororesin such as polytetrafluoroethylene can be used. Of the flow path walls 3a, the flow path walls located in the heat receiving area 6 and the heat dissipating area 7 may be made of a material having a higher thermal conductivity than the other parts (e.g., aluminum, copper, stainless steel, aluminum oxide). In addition, the flow path walls located in the heat receiving area 6 and the heat dissipating area 7 may be covered with a material different from the flow path walls (e.g., aluminum, copper, stainless steel).

[0042] The inner wall 3b of the flow path wall 3a of the flow path 3 and the metal porous body 4 may be in contact with each other. This increases the amount of heat transferred from the metal porous body 4 to the fluid 2, further improves the flow rate of the fluid, further improves the flow rate generated by the entire heat transfer system, and further improves the heat exchange efficiency. The inner wall 3b and the metal porous body 4 may be integrally molded or soldered. As long as the effect of the present disclosure is not impaired, a configuration in which the inner wall 3b and the metal porous body 4 are not in contact is also included in the scope of the present disclosure. Examples of such a configuration include a case in which a very small gap exists between the inner wall 3b and the metal porous body 4, and a case in which another member with very high thermal conductivity is sandwiched between the inner wall 3b and the metal porous body 4.

[0043] <Porous metal body> In the heat transfer system 1 of the present embodiment, the metal porous body 4 is made of a metal having a plurality of pores formed therein, at least some of which are open pores.

[0044] ≪Composition≫ The metal constituting the metal porous body 4 is a metal consisting of one metallic element selected from the first group consisting of aluminum, magnesium, copper, silver and gold; An alloy consisting of two or more metal elements selected from Group 1; A metal in a composite state of two or more metal elements selected from Group 1, An alloy comprising one or more metal elements selected from a first group and one or more elements selected from a second group consisting of iron, cobalt, chromium, nickel, manganese, tin, zinc, silicon, phosphorus, carbon, boron, scandium, molybdenum, tungsten and titanium; or, The metal is composed of a composite of one or more metal elements selected from the first group and one or more elements selected from the second group.

[0045] The above metals have high thermal conductivity, which further improves the heat exchange efficiency of the heat transfer system.

[0046] In this disclosure, the term "metal" is defined as a concept including metals consisting of one type of metal element, alloys containing two or more types of metal elements, and metals in a composite state of two or more types of metal elements.

[0047] In the present disclosure, "a metal in a composite state of two or more metal elements" means a state in which two or more metals exist as individual substances, not as an alloy. Specifically, it means a state in which the surfaces of two or more metal powders are bonded together to form a mold. "A metal in a composite state of one or more metal elements selected from the first group and one or more elements selected from the second group" means a state in which one or more metal elements selected from the first group and one or more elements selected from the second group exist as individual substances (graphite or diamond in the case of carbon, boron as simple substance in the case of boron), or as metal carbide or metal boride, not as an alloy.

[0048] Examples of alloys include a Cu-1% Ag alloy and an Al-1% Mg-0.6% Si-0.5% Fe-0.25% Cu-0.1% Cr alloy (A6061).

[0049] From the viewpoint of having high thermal conductivity, the metal may be pure copper, pure aluminum, a copper alloy containing 50 mass% or more of copper, or an aluminum alloy containing 50 mass% or more of aluminum. The alloy may be in a state where the constituent elements are in a solid solution in copper, aluminum, etc. The alloy may be in a state where precipitates or different phases are dispersed.

[0050] The composition of the constituent elements of the metal porous body is measured by ICP emission spectrometry.

[0051] The metal porous body of the heat transfer system of this embodiment may contain impurities other than the above metals, as long as the effect of the present disclosure is not impaired. Here, as defined above, the concept of "metal" includes metals consisting of one metal element, alloys containing two or more metal elements, and metals in a composite state containing two or more metal elements. The metal porous body of the first embodiment may be composed of the above metals and impurities. Examples of the impurities include oxygen, hydrogen, carbon, nitrogen, sulfur, phosphorus, boron, silicon, and metal elements other than the metal elements contained in the first and second groups. The impurities are contained independently from the parent phase in the form of precipitates or the like. The content of the impurities may be less than the volume ratio that satisfies a predetermined thermal conductivity. For example, it may be 3 atomic % or less. The content of the impurities is measured by gas chromatography (GC) analysis or ICP emission spectrometry.

[0052] <Structure> The porous metal body 4 is made of a metal in which a plurality of pores are formed. That is, the porous metal body 4 has a plurality of pores. At least a portion of the pores are open pores. The minimum pore size of the pores in the porous metal body is 10 μm or more. The maximum pore size of the pores in the porous metal body is 420 μm or less. The porosity of the porous metal body 4 is 60% or more and 85% or less. The transmittance of the porous metal body 4 is 0.6×10 -12 m 2 This allows the fluid to pass through the interior of the porous metal body via the pores in the porous metal body.

[0053] <Minimum pore diameter> In this embodiment, the minimum pore size of the pores of the metal porous body is 10 μm or more. This suppresses an increase in the flow resistance of the fluid. If the minimum pore size of the pores is less than 10 μm, the movement of the fluid due to the capillary force is difficult to occur, so that even if the pores are open, they will essentially act as closed pores in the part far from the shortest path of the fluid movement path. From the viewpoint of reducing the flow resistance of the fluid, the lower limit of the minimum pore size of the pores of the metal porous body is 10 μm or more, may be more than 10.0 μm, may be 10.1 μm or more, may be 10.5 μm or more, may be 11 μm or more, may be 12 μm or more, may be 15 μm or more, may be 20 μm or more, may be 23 μm or more, may be 24 μm or more, may be 25 μm or more, may be 30 μm or more, may be 35 μm or more, may be 40 μm or more. There is no particular upper limit to the minimum pore size of the pores in the metal porous body, and in principle it is smaller than the maximum pore size.

[0054] The minimum pore size of the metal porous body is measured by mercury intrusion porosimetry. The mercury intrusion porosimetry is performed in accordance with JIS R 1655:2003 "Method of testing pore size distribution of molded fine ceramics by mercury intrusion porosimetry." The AutoPore V9600 by Micrometritics can be used as the measurement device.

[0055] <Maximum pore diameter> In this embodiment, the maximum pore size of the metal porous body is 420 μm or less. The upper limit of the maximum pore size of the metal porous body is 420 μm or less, may be 380 μm or less, 360 μm or less, 330 μm or less, 300 μm or less, or 250 μm or less, from the viewpoint of increasing the contact area with the fluid and promoting the transfer of heat between the metal porous body and the fluid. The lower limit of the maximum pore size of the metal porous body may be 50 μm or more, 60 μm or more, 70 μm or more, or 125 μm or more, from the viewpoint of reducing the flow resistance of the fluid. The maximum pore size of the metal porous body may be 50 μm or more and 420 μm or less, 50 μm or more and 380 μm or less, 50 μm or more and 360 μm or less, 60 μm or more and 330 μm or less, 70 μm or more and 300 μm or less, or 125 μm or more and 250 μm or less. The maximum pore size of the metal porous body is measured by the above-mentioned mercury intrusion method.

[0056] <Porosity> In this embodiment, the porosity of the metal porous body 4 is 60% or more and 85% or less. The lower limit of the porosity of the metal porous body is 60% or more, or may be 70% or more, or may be 75% or more, from the viewpoint of reducing the flow resistance of the fluid. The upper limit of the porosity of the metal porous body is 85% or less, or may be 80% or less, from the viewpoint of increasing the contact area with the fluid and promoting the transfer of heat between the metal porous body and the fluid. The porosity of the metal porous body may be 70% or more and 85% or less, or may be 75% or more and 80% or less.

[0057] The porosity of a porous metal body is defined by the following formula (1). Porosity = {1-[Mass of porous metal body [g] / (Volume of porous metal body [cm 3 ]×Material density [g / cm 3 ])]}×100[%] (1) The volume of the porous metal body in the above formula (1) [cm 3 ]" means the volume based on the external shape of the metal porous body including pores.

[0058] <Transmittance> In this embodiment, the transmittance of the metal porous body is 0.6×10 -12 m2 This reduces the flow resistance of the fluid. The lower limit of the permeability of the metal porous body is 0.60×10 -12 m 2 More than 0.70×10 is also acceptable. -12 m 2 More than 0.75×10 is also acceptable. -12 m 2 More than 0.80×10 is also acceptable. -12 m 2 More than 0.85×10 -12 m 2 More than 0.90×10 is also acceptable. -12 m 2 The upper limit of the transmittance of the metal porous body is not particularly limited, but from the viewpoint of production, it is preferably, for example, 1.0×10 -10 m 2 The transmittance of the metal porous body can be set to 0.60×10 or less. -12 m 2 Above 1.0×10 -10 m 2 Less than 0.70×10 -12 m 2 Above 1.0×10 -10 m 2 Less than 0.75×10 -12 m 2 Above 1.0×10 -10 m 2 Less than 0.80×10 -12 m 2 Above 1.0×10 -10 m 2 Less than 0.85×10 -12 m 2 Above 1.0×10 -10 m 2 Less than 0.90×10 -12 m 2 Above 1.0×10 -10 m 2 The following is also fine.

[0059] The permeability of a porous metal body can be measured by evaluating the permeability of the porous metal body in accordance with JIS R 1671:2006 "Test method for water permeability and hydraulic equivalent diameter of porous fine ceramics bodies." Specifically, an evaluation sample consisting of a porous metal body with a diameter of 25 mm and a thickness of 3 mm is prepared, and evaluation is performed based on the above JIS regulations. If the porous metal body to be evaluated is smaller than the size of the evaluation sample described above, the evaluation sample may be prepared by combining multiple porous metal bodies to obtain a diameter of 25 mm and a thickness of 3 mm.

[0060] <Open porosity> In the present disclosure, "open porosity" refers to the volume ratio (volume %) of open pores to the total pores (including open pores and closed pores) contained in the metal porous body. "Open pores" refer to pores contained in the metal porous body that communicate with the surface of the metal porous body. "Closed pores" refer to pores contained in the metal porous body that do not communicate with the surface of the metal porous body.

[0061] In this embodiment, the lower limit of the open porosity of the pores of the metal porous body may be 50% or more, 60% or more, or 70% or more from the viewpoint of reducing the flow resistance of the fluid. The upper limit of the open porosity of the pores is not particularly limited and may be 100% or less. The open porosity of the pores may be 50% or more and 100% or less, 60% or more and 100% or less, or 70% or more and 100% or less.

[0062] The method for measuring the open porosity of pores in a porous metal body is as follows: First, the apparent porosity P1 (corresponding to the open porosity of a porous metal body) is measured by the Archimedes method or the mercury intrusion method (specified in JIS R 1655:2003 "Test method for pore size distribution of molded bodies by mercury intrusion method for fine ceramics").

[0063] The porosity P2 of the metal porous body (corresponding to the total porosity of the metal porous body) is calculated based on the above formula (1).

[0064] The percentage of the apparent porosity P1 of the porous metal body relative to the porosity P2 of the porous metal body is calculated as (P1 / P2) x 100. This percentage is the open porosity of the pores of the porous metal body.

[0065] <Thermal conductivity of porous metal bodies> In this embodiment, the thermal conductivity of the metal porous body may be 10 W / mK or more. This makes it easier for heat from the outside of the internal space to be transmitted to the fluid through the metal porous body. The lower limit of the thermal conductivity of the metal porous body may be 10 W / mK or more, 11 W / mK or more, 12 W / mK or more, 15 W / mK or more, 20 W / mK or more, or 25 W / mK or more. The upper limit of the thermal conductivity of the metal porous body is not particularly limited, but may be, for example, 205 W / mK or less from the viewpoint of manufacturing.

[0066] The method for measuring the thermal conductivity of a porous metal body is as follows. The top and bottom surfaces (circular parts) of a porous metal body machined to φ10 mm x 2.2 mmt are polished to a thickness of 2.0 mm by 0.1 mm using emery paper in a non-oxidizing room temperature atmosphere with an oxygen concentration of 10,000 ppm. After removing shavings using an air blower or the like, pure aluminum foil of φ10 mm x 20 μm thickness is brought into contact with the polished top and bottom surfaces of the porous metal body. In this state, a load of 50 kgf is applied with a hand press to bring the aluminum foil into close contact with the porous metal body, and a measurement sample is obtained.

[0067] The thermal conductivity of the metal porous body is measured by the laser flash method using the above-mentioned measurement sample. More specifically, the thermal diffusion coefficient is measured using LFA457MicroFlash (manufactured by NETZSCH), and the thermal conductivity in the thickness direction of the metal porous body is calculated based on the thermal diffusion coefficient and the volume ratio and specific heat of each constituent material.

[0068] When calculating the thermal conductivity above, the specific heat of each constituent material is determined based on the Metals Data Book, 4th Edition (2004, Maruzen Publishing), edited by the Japan Institute of Metals. Pores can be treated as air, and their specific heat is calculated as 1.0 kJ / (kg K). Prior to measuring the thermal conductivity, the thermal conductivity of a pure copper sample of the same shape is measured under the same conditions, and the result is used as a reference to correct the measurement results.

[0069] If the planar shape of the metal porous body to be evaluated is smaller than a circle with a diameter of 10 mm, cut out several samples and align them so that their surfaces are on the same plane to obtain a 50 mm 2 The above measurement area may be secured for evaluation.

[0070] <Thermal conductivity of metals> In the metal porous body of the heat transfer system of this embodiment, the thermal conductivity of the metal may be 100 W / mK or more. Factors that affect the thermal conductivity of the metal porous body include the thermal conductivity of the material, the volume ratio of the metal in the metal porous body, and, when the metal porous body is formed by bonding metal powders, the interface thermal resistance between the metal powders. When the thermal conductivity of the metal is 100 W / mK or more, the thermal conductivity of the metal porous body is improved.

[0071] The lower limit of the thermal conductivity of the metal may be 100 W / mK or more, 200 W / mK or more, or 350 W / mK. The upper limit of the thermal conductivity of the metal is not particularly limited, but may be, for example, 400 W / mK or less.

[0072] The method for measuring the thermal conductivity of metals is as follows. The metal porous body is heated in a hydrogen atmosphere at a temperature (K) that is 80% of the lowest melting temperature (K) of the materials that make up the body, and the metal porous body is made into a state in which no oxide film of the base metal exists on the inner wall of the metal porous body. Then, while maintaining a non-oxidizing atmosphere, the body is densified by a spark plasma sintering method in a vacuum (10 Pa or less). The heating temperature is the above-mentioned hydrogen atmosphere treatment temperature, the pressure is 30 MPa, and the pressure time is 10 minutes. The thermal conductivity of the obtained dense body is measured by a laser flash method. More specifically, the thermal diffusion coefficient is measured using an LFA457MicroFlash (manufactured by NETZSCH), and the thermal conductivity in the thickness direction is calculated based on the thermal diffusion coefficient and the volume ratio and specific heat of each constituent material.

[0073] When calculating the thermal conductivity above, the specific heat of each constituent material is determined based on the Metals Data Book, 4th Edition (2004, Maruzen Publishing), edited by the Japan Institute of Metals. Pores can be treated as air, and their specific heat is calculated as 1.0 kJ / (kg K). Prior to measuring the thermal conductivity, the thermal conductivity of a pure copper sample of the same shape is measured under the same conditions, and the result is used as a reference to correct the measurement results.

[0074] If the planar shape to be evaluated is smaller than a circle with a diameter of 10 mm, cut out multiple samples and align them so that their surfaces are on the same plane to obtain a 50 mm 2 The above measurement area may be secured for evaluation.

[0075] <Method of manufacturing porous metal body> An example of a method for manufacturing the porous metal body of the heat transfer system of this embodiment will be described below. The method for manufacturing the porous metal body of this embodiment may include a preparation step, a mixing step, a sintering step, and a cleaning step.

[0076] ≪Preparation process≫ In the preparation step, a raw material powder of the porous metal body and sodium chloride powder (NaCl powder) are prepared.

[0077] Examples of the raw material powder include metal powders consisting of one metal element selected from Group 1 consisting of aluminum, magnesium, copper, silver, and gold, alloy powders consisting of two or more metal elements selected from Group 1, and powders consisting of one or more metal elements selected from Group 1 and one or more elements selected from Group 2 consisting of iron, cobalt, chromium, nickel, manganese, tin, zinc, silicon, phosphorus, carbon, boron, scandium, molybdenum, tungsten, and titanium.

[0078] The particle diameter D10 of the raw powder is 6 to 45 μm, the D50 is 13 to 75 μm, and the D90 is 27 to 106 μm. Here, the particle diameter D10 of the raw powder is the particle diameter at which the cumulative volume ratio from the small diameter side is 10% in a histogram where the horizontal axis indicates the particle diameter and the vertical axis indicates the volume ratio. The particle diameter D50 of the raw powder is the particle diameter at which the cumulative volume ratio from the small diameter side is 50% in the histogram. The particle diameter D90 of the raw powder is the particle diameter at which the cumulative volume ratio from the small diameter side is 90% in the histogram. The above D10, D50, and D90 are measured by a laser diffraction / scattering method.

[0079] The particle diameter D50 of the NaCl powder is 45 to 500 μm. Here, the particle diameter D50 of the NaCl powder is the particle diameter at which the cumulative volume ratio from the small diameter side is 50% in a histogram in which the horizontal axis indicates the particle diameter and the vertical axis indicates the volume ratio. The histogram is created based on the results of sieving the sample using sieves specified in JIS Z 8801-1:2019 "Test sieves - Part 1: Metal mesh sieves" and measuring the mass of the sample remaining on each sieve.

[0080] ≪Mixing process≫ Next, in the mixing step, the raw material powder and NaCl powder are mixed to obtain a mixed powder. The mixing ratio of the raw material powder and NaCl powder is appropriately adjusted according to the porosity of the metal porous body to be manufactured. The percentage of NaCl powder in the mixed powder varies depending on the average particle size of the NaCl powder, and is 60 to 88 volume % if the average particle size is 45 to 70 μm, and 79 to 88 volume % if the average particle size is more than 70 μm and 500 μm or less.

[0081] The mixed powder is sealed in a cylindrical glass container with a diameter of 100 mm and a wall thickness of 1 mm, and mixed for 10 minutes by rotating the glass container at 120 rpm with the axial direction of the container as the rotation axis. For example, a rotary mill can be used for mixing. If the raw material powders and NaCl powder can be mixed uniformly, a W-type mixer, V-type mixer, or drum-type mixer can also be used. If there is a risk of dust explosion from the mixed powder, the inside of the glass container can be replaced with a low-oxygen atmosphere or an inert atmosphere.

[0082] <Sintering process> Next, in the sintering process, the mixed powder is loaded into a mold made of graphite or alloy tool steel for hot working, and pressure sintering is performed to obtain a sintered body. The conditions for pressure sintering are 20 to 750°C, pressure 10 to 2000 MPa, and holding time 1 second to 30 minutes. Before pressure sintering, the mixed powder may be preformed to form a green compact.

[0083] <Cleaning process> Next, in the cleaning process, the sintered body is immersed in water, and NaCl is dissolved in the water to obtain a metal porous body. Specifically, about 1 L of pure water is prepared for 10 g of the sintered body. The pure water is placed in a beaker, and the sintered body is immersed in the pure water and stirred. By immersing for a total of about 50 hours while changing the pure water every 5 hours, NaCl is sufficiently dissolved outside the metal porous body. In this way, the metal porous body of the heat transfer system of this embodiment can be obtained.

[0084] <Volume of porous metal body> In this embodiment, the porous metal body 4 is provided in the heat receiving area 6, and the volume of the porous metal body 4 may be 30% or more of the volume of the heat receiving area 6. This increases the amount of heat transferred from the porous metal body 4 to the fluid 2, further improving the flow rate of the fluid, further improving the flow rate generated by the entire heat transfer system, and further improving the heat exchange efficiency.

[0085] From the viewpoint of improving heat exchange efficiency, the lower limit of the volume occupied by the metal porous body 4 with respect to the volume of the heat receiving area 6 may be 30% or more, 40% or more, 50% or more, or 90% or more. The upper limit of the volume occupied by the metal porous body 4 with respect to the volume of the heat receiving area 6 may be 100% or less. The volume occupied by the metal porous body 4 with respect to the volume of the heat receiving area 6 may be 30% or more and 100% or less, 40% or more and 100% or less, 50% or more and 100% or less, or 90% or more and 100% or less.

[0086] <Heat receiving area> In the heat transfer system 1 of this embodiment, the heat receiving area 6 is an area where the fluid 2 receives heat from the outside of the internal space 3c.

[0087] <Heat radiation area> In the heat transfer system 1 of this embodiment, the heat dissipation region 7 is a region where the fluid 2 dissipates heat to the outside of the internal space 3c.

[0088] <Fluid> In the heat transfer system 1 of the present embodiment, the fluid 2 may be a liquid. There are no particular limitations on the type of fluid 2, so long as it is a type that is generally used in heat transfer systems. Examples of the fluid 2 include water, radiator liquid, acetone, and ethanol. There are no particular limitations on the viscosity of the fluid 2, so long as it is within a range that is generally used in transfer systems. The viscosity of the fluid 2 may be, for example, 0.1 mPa·s or more and 10 mPa·s or less.

[0089] <Heating part> The heat transfer system 1 of this embodiment may further include a heating unit 8 that is provided outside the internal space 3c of the flow path 3 and provides heat to the fluid 2 present in the heat receiving area 6. The heating means of the heating unit 8 is not particularly limited. For example, a direct heat source such as a semiconductor device, an electric heater, an air heater, or a lamp heater, or waste heat recovered from sunlight, an engine, a heat treatment furnace, or the like may be used.

[0090] <Cooling section> The heat transfer system 1 of the present embodiment may further include a cooling unit 9 that is provided outside the internal space 3c of the flow path 3 and removes heat from the fluid 2 present in the heat dissipation area 7. The cooling means of the cooling unit 9 is not particularly limited. For example, a heat exchange mechanism with a refrigerant such as a radiator, forced air cooling by a cooling fan, etc. may be used. EXAMPLES

[0091] The present embodiment will be described more specifically with reference to examples, although the present embodiment is not limited to these examples.

[0092] <Production of porous metal bodies> ≪Preparation process≫ Raw material powders and NaCl powder were prepared. The composition of the raw material powders, D10, D50, D90, and average particle size of the NaCl powder are as shown in the "Raw material powders" and "NaCl powder" columns of Tables 1 and 2.

[0093] ≪Mixing process≫ A mixed powder was obtained by mixing the raw material powder and NaCl powder in such a ratio that the amount of each powder in the mixed powder was the mass % shown in the "Mixed Powder" column of Tables 1 and 2. A rotary mill was used for mixing. The mixing conditions (rotation speed, time) are as shown in the "Mixing" column of Tables 3 and 4.

[0094] The volumetric content B (volume %) of NaCl powder in the mixed powder was converted based on the mass content A (mass %) of NaCl powder in the mixed powder, and shown in the "Volume % (converted value)" column of "NaCl powder" in Table 1. The volumetric content B (volume %) of NaCl powder in the mixed powder was calculated according to the following formula. B(volume%)=100×(A(mass%) / 2.17) / (A(mass%) / 2.17+(100-A(mass%)) / ρ) In the above formula, ρ indicates the density of the metal (aluminum = 2.73, copper = 8.96).

[0095] <Sintering process> The mixed powder was packed into a graphite mold of φ40 mm so that the final thickness after densification would be 8 to 12 mm, and pressure sintering was performed to obtain a sintered body. The pressure sintering conditions (pressure, temperature, time) are as shown in the "Sintering" column of Tables 3 and 4.

[0096] <Cleaning process> Next, the sintered body was immersed in water to dissolve NaCl into the water, and a metal porous body of each sample was obtained. In all samples, the shape of the metal porous body was cylindrical. The diameter of the bottom surface of the metal porous body was 40 mm, and the height was 10 mm.

[0097] [Table 1]

[0098] [Table 2]

[0099] [Table 3]

[0100] [Table 4]

[0101] <Evaluation of porous metal bodies> The obtained metal porous body was measured for composition, thermal conductivity of metal, porosity, open porosity of pores, minimum pore size, maximum pore size of pores, thermal conductivity of metal porous body, and transmittance of metal porous body. The measurement method for each item is as described in embodiment 1. The results are shown in Tables 5 and 6.

[0102] [Table 5]

[0103] [Table 6]

[0104] <Production of heat transfer system> Using the porous metal bodies of each sample, a heat transfer system 1 having the configuration shown in FIG. 1 and in which a heating unit 8 and a flow path wall 3a are joined was produced. In the samples in which "integral molding" is written in the "Joining method" column of Tables 7 and 8, the inner wall 3b of the flow path wall 3a and the porous metal body 4 were integrally molded. In the samples in which "solder bonding" is written in the "Joining method" column of Tables 7 and 8, the inner wall 3b of the flow path wall 3a and the porous metal body 4 were solder bonded. In the samples in which "silver brazing" is written in the "Joining method" column of Tables 7 and 8, the inner wall 3b of the flow path wall 3a and the porous metal body 4 were silver brazing bonded.

[0105] The material of the flow passage wall 3a of the flow passage 3 of the heat transfer system 1 is polytetrafluoroethylene. The cross section of the internal space 3c in a cross section perpendicular to the flow direction of the fluid 2 is elliptical, with a maximum diameter of 2.0 mm, a minimum diameter of 1.6 mm, and a cross-sectional area of ​​2.0 mm. 2 It is.

[0106] As the fluid 2, water was used.

[0107] As a comparative standard, a heat transfer system was fabricated using the same flow path wall 3a as above, but without providing a metal porous body in the internal space.

[0108] <Efficiency evaluation test of heat transfer system> An efficiency evaluation test of the heat transfer system was conducted using water as fluid 2. Water at three different temperatures, 30°C, 20°C, and 10°C, was prepared as fluid 2 and tests were conducted at each temperature. The viscosity of water varies depending on the temperature, and between 10°C and 30°C, the lower the temperature, the greater the viscosity. The viscosity of water at 10°C is 1.3 mPa s, and at 30°C it is 0.8 mPa s.

[0109] While the pump 5 was applying a driving force to the fluid 2 (water), the heating unit 8 was operated to apply heat to the fluid 2 present in the heat receiving area 6, thereby driving each sample and the comparative standard heat transfer system 1. The power of the heating unit was set to 2 W, and 30 minutes after the start of heating, the temperature T1 of the joint interface between the heating unit 8 and the flow path wall 3a in each sample heat transfer system was measured using a thermocouple. The power of the heating unit was also set to 2 W, and 30 minutes after the start of heating, the temperature T2 of the joint interface between the heating unit 8 and the flow path wall 3a in the comparative standard heat transfer system was also measured using a thermocouple. The difference (T1-T2) between T1 and T2 is shown in Tables 7 and 8. The smaller the value of the difference (T1-T2), the more improved the heat exchange efficiency of the heat transfer system.

[0110] [Table 7]

[0111] [Table 8]

[0112] <Consideration> The heat transfer systems of Samples 1 to 22 correspond to the examples. The heat transfer systems of Samples 1 to 22 were confirmed to have excellent heat exchange efficiency, with the heat exchange efficiency being equal to or higher than the comparison standard at all temperatures of 30°C, 20°C, and 10°C. The heat transfer systems of Samples 1-1 to 1-14 correspond to the comparative examples. The heat exchange efficiency of Samples 1-1 to 1-14 was lower than the comparison standard at least at any one of temperatures of 30°C, 20°C, and 10°C.

[0113] Among the examples, particularly Samples 3, 7, 8, 13, 15, and 18 to 21 exhibited excellent heat exchange efficiency even at low temperatures (10° C.) where the fluid was highly viscous.

[0114] In Samples 10 to 22, the material of the metal porous body was copper. The porous structure (metal skeleton) of the metal porous body of the present disclosure is formed by heating and softening the metal below the melting point of NaCl crystals and applying pressure to cause plastic deformation. In the case of copper, it can be realized by heating to a processing temperature of 700°C (973K), which is 70% of the melting point (unit: Kelvin) of the melting point (1084°C = 1357K). Therefore, the metal porous body of the heat transfer system of the present disclosure can be realized even if the material is aluminum (melting point 660°C = 933K), magnesium (melting point 650°C = 923K), copper, silver (melting point 960°C = 1233K), and gold (melting point 1064°C = 1337K), or an alloy of these elements. Examples of the alloy include an alloy of two or more metal elements selected from the first group consisting of aluminum, magnesium, copper, silver, and gold, a metal in a composite state of two or more metal elements selected from the first group, an alloy of one or more metal elements selected from the first group and one or more elements selected from the second group consisting of iron, cobalt, chromium, nickel, manganese, tin, zinc, silicon, phosphorus, carbon, boron, scandium, molybdenum, tungsten, and titanium, or a metal in a composite state of one or more metal elements selected from the first group and one or more elements selected from the second group. These are just a few examples, and the metal porous body of the present disclosure can be realized as long as it satisfies the condition of a melting point of 1084°C or less and is not reactive with NaCl.

[0115] The porous metal body was made of aluminum in Samples 1 to 9, and copper in Samples 10 to 22. Since the porous metal body in the heat transfer system of the present disclosure is made of a metal, high heat exchange efficiency can be obtained even in a heat transfer system using a porous metal body made of a material other than aluminum or copper.

[0116] Although the embodiments and examples of the present disclosure have been described above, it is intended from the outset that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways. The embodiments and examples disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is indicated by the claims, not by the embodiments and examples described above, and is intended to include the meaning equivalent to the claims and all modifications within the scope. [Explanation of symbols]

[0117] 1. Heat Transfer System 2 fluid 3. Flow Path 3a Channel wall 3b Inner wall 3c interior space 4. Porous metal 5. Pump 6 Heat receiving area 7 Heat dissipation area 8 Heating section 9 Cooling section

Claims

1. A flow path through which a fluid flows is provided, The flow path is A flow path wall defining an internal space through which the fluid flows; A metal porous body provided in the internal space, The metal porous body is made of a metal having a plurality of pores formed therein, At least a portion of the pores are open pores, The metal is a metal consisting of one metal element selected from the first group consisting of aluminum, magnesium, copper, silver and gold; An alloy consisting of two or more metal elements selected from the first group; A metal in a composite state of two or more metal elements selected from the first group, An alloy comprising one or more metal elements selected from the first group and one or more elements selected from a second group consisting of iron, cobalt, chromium, nickel, manganese, tin, zinc, silicon, phosphorus, carbon, boron, scandium, molybdenum, tungsten and titanium; or, The metal is a composite of one or more metal elements selected from the first group and one or more elements selected from the second group, The minimum pore size of the pores of the metal porous body is 10 μm or more; The maximum pore size of the pores of the metal porous body is 420 μm or less, The porosity of the metal porous body is 60% or more and 85% or less, The transmittance of the porous metal body is 0.6×10 －１２ m ２ That's it for the heat transfer system.

2. The heat transfer system of claim 1 , wherein the thermal conductivity of the metal is 100 W / mK or greater.

3. The transmittance of the porous metal body is 0.8×10 －１２ m ２ The heat transfer system according to claim 1 or 2, wherein:

4. 3. The heat transfer system according to claim 1, wherein the open porosity of the pores of the metal porous body is 60% or more.

5. A fluid filled in the internal space; A pump that circulates the fluid in a predetermined flow direction, The flow path is a heat receiving region in which the fluid receives heat from the outside of the internal space; The heat transfer system according to claim 1 or 2, further comprising a heat dissipation region, which is a region where the fluid dissipates heat to the outside of the internal space.

6. A heating unit is provided outside the internal space and applies heat to the fluid present in the heat receiving area. The heat transfer system according to claim 5 , wherein the porous metal body is provided in the heat receiving area.

7. 3. The heat transfer system according to claim 1, wherein the inner wall of the flow path and the porous metal body are in contact with each other.

8. The heat transfer system according to claim 5 , further comprising a cooling section provided outside the internal space and configured to remove heat from the fluid present in the heat dissipation area.

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