JP6150686B2 - Heat exchanger and heat exchanger manufacturing method - Google Patents

Description

  The present invention relates to a heat exchanger that recovers heat from a heat source and a method for manufacturing the heat exchanger.

The heat exchanger recovers heat from various heat engines such as engines and heat sources such as incineration facilities, lowers the temperature of the heat source, and uses the recovered heat.
A conventional heat exchanger has a configuration in which a heat medium that is a heated body flows inside a tubular heating body, releases heat from the outside of the heat exchanger to the heat medium by heat convection through the heating body, The heat recovered by the heat medium flowing is transferred. In addition, in order to improve the heat recovery efficiency, heat exchange by heat radiation may be used in combination by attaching a ceramic to the heating body (see, for example, Patent Document 1).

  It is also known to further improve the heat recovery efficiency by making the inner wall of the heat pipe a wick structure made of carbon nanotubes (see, for example, Patent Document 2).

JP 2004-340453 A Special table 2009-535598

However, in recent heat exchangers, higher efficiency of heat exchange is required.
Therefore, an object of the present invention is to increase the efficiency of heat exchange in a heat exchanger.

  In order to achieve the above object, a heat exchanger according to the present invention is a heat exchanger that recovers heat from a heat source, and includes a tubular heating body, a heat medium filled in a tube of the heating body, A carbon nanotube having an orientation structure that protrudes toward the heat medium on the inner surface of the heating body with a predetermined length, and a sword mountain structure in which the carbon nanotubes are arranged at predetermined intervals. The sword mountain structure is a structure that resonates the heat radiation emitted in accordance with the temperature of the heat source.

  In addition, the surface of the carbon nanotube is Ti, Cu, Cr, Fe, Co, Ni, Zn, Au, Ag, Si, or an oxide, carbide, or nitride thereof, or a composite of two or more. It is preferable to provide a coating layer containing an object.

  In addition, the heat medium may be made of a simple substance of Si, Al, Mg, Fe, Co, Ni, Cu, Zn, Mo, Ru, Ag, Pt, Au, Ti, Cr, carbide, or nitride, or 2 It is preferable to add an infrared absorbing material containing one or more composites.

  Furthermore, the method for manufacturing a heat exchanger according to the present invention is a method for manufacturing a heat exchanger for recovering heat from a heat source, in which a granular catalyst is arranged in a sword mountain shape at predetermined intervals on the inner surface of a tubular heating body. And a step of growing the catalyst to a predetermined length to form carbon nanotubes oriented in a direction protruding from the inner wall of the heating body, wherein the sword-like structure in which the carbon nanotubes are arranged is the heat source It is characterized by resonating the thermal radiation emitted corresponding to the temperature of.

  Specifically, a method for forming a catalyst for carbon nanotubes in a layered manner and granulating by heating, a method of supporting the granulated catalyst from the beginning on a tubular inner surface by solution impregnation or spraying method, etc. is there.

  As described above, by arranging the carbon nanotubes of the orientation structure in the sword mountain structure in the heating body of the heat exchanger, the sword mountain structure of the carbon nanotubes has a structure in which thermal radiation corresponding to the temperature of the heat source resonates. It is possible to improve the efficiency of heat exchange by heat radiation from the carbon nanotubes.

Schematic showing the configuration of the heat exchanger of the present invention Schematic enlarged view illustrating the arrangement of carbon nanotubes in the heat exchanger of the present invention The schematic enlarged view explaining the structure of the carbon nanotube in the heat exchanger of this invention Process drawing explaining the manufacturing method of the carbon nanotube by which space | interval is controlled by aggregation of a catalyst Process drawing explaining the manufacturing method of the carbon nanotube by which space is controlled by injection of local gas Process drawing explaining the manufacturing method of the carbon nanotube bundled

First, the structure of the heat exchanger of this invention is demonstrated using FIGS. 1-3.
FIG. 1 is a schematic view showing the configuration of the heat exchanger of the present invention, FIG. 2 is a schematic enlarged view illustrating the arrangement of carbon nanotubes in the heat exchanger of the present invention, and FIG. 3 is a schematic view of carbon nanotubes in the heat exchanger of the present invention. It is a schematic enlarged view explaining a structure.

  As shown in FIGS. 1 to 3, the heat exchanger 3 of the present invention is a heating body 2 that is a tubular heat pipe, and a gas, liquid, or solid granular material that flows inside the tube of the heating body 2. The heating medium 4 functions as a body to be heated, and the carbon nanotubes 1 are arranged on the inner surface of the heating body 2 and oriented in a direction protruding toward the heating medium 4. The carbon nanotubes 1 are arranged in a sword mountain shape (FIGS. 2A and 2B) so that the wavelength of the heat radiation 6 emitted corresponding to the temperature supplied to the heating body 2 resonates. The carbon nanotubes 1 are arranged at intervals W and lengths L. Thus, by arranging the carbon nanotubes 1 in a sword mountain shape so that the heat radiation 6 having a wavelength corresponding to a predetermined temperature resonates, the sword mountain array of the carbon nanotubes 1 acts as a resonator. Therefore, when a predetermined temperature is supplied to the heat exchanger 3, heat radiation resonates within the sword mountain array of the carbon nanotubes 1, and the efficiently supplied heat is efficiently transferred from the carbon nanotubes 1 to the heat medium 4. Can be released. When the length L of the carbon nanotubes 1 is constant, it is most efficient that the intervals W of the carbon nanotubes 1 are all the same length, but the length of the interval W at a certain ratio or more. If the length is such that it resonates with the wavelength of the heat radiation 6, even if there are intervals of different lengths, a certain effect can be obtained. Further, the target interval W is not limited to one type, and when there are a plurality of wavelengths of the target heat radiation 6, the heat radiation 6 targeting each of the intervals W at a predetermined ratio among the intervals of the carbon nanotubes 1. If the length resonates with the wavelength, a certain heat radiation effect can be improved corresponding to a plurality of heat sources.

  The heat exchanger 3 contacts a heat source (not shown) of various heat engines such as an engine or an incineration facility directly or via a liquid or gaseous medium, recovers heat from the heat source, and lowers the temperature of the heat source. In addition, the recovered heat is used. In the heat exchanger 3 in contact with the heat source, the heating element 2 is heated by the heat source, and the heat is released to the heat medium 4. When heat is released to the heat medium 4, heat is released to the heat medium 4 by convection heat transfer 5 from the heating body 2 and the carbon nanotubes 1 and heat radiation 6 from the carbon nanotubes by far-infrared radiation. Thereby, heat exchange is performed between the heat medium 4 and the heat source, the heat source is cooled, and the heat medium 4 recovers the heat of the heat source. The recovered heat is carried to an external device (not shown) as the heat medium 4 flows, and the heat recovered by the external device is used.

  As described above, the convection heat transfer 5 from the heating body 2 and the carbon nanotube 1 based on the increase in the contact area with the heat medium 4 by the aligned and protruding carbon nanotubes 1, and the carbon nanotubes 1 arranged in a sword mountain shape. Since the heat radiation 6 resonated with the heat radiation efficiency of the heat medium 4 is improved, the heat exchange can be made highly efficient. Here, the carbon nanotubes generally have a high heat radiation rate, and at the same time, since the carbon nanotubes 1 are oriented in the direction toward the heat medium 4, the heat radiation 6 can efficiently release heat to the heat medium 4. Can do. Furthermore, by making the sword mountain-like structure of the carbon nanotube 1 have an interval W and a length L that resonate with the wavelength of the heat radiation 6 emitted corresponding to the temperature of the heat source assumed in advance, the heat radiation can be performed more efficiently. Heat can be released to the heat medium 4 by 6 and heat exchange can be made highly efficient. For example, when the temperature of the heat source is assumed to be 1000 ° C., since the wavelength of the heat radiation 6 is 2 μm, when the length of the carbon nanotube 1 is 10 μm, the interval W between the carbon nanotubes 1 is 1.5 μm, and the temperature of the heat source is When the temperature is assumed to be 400 ° C., since the wavelength of the heat radiation 6 is 4 μm, when the length of the carbon nanotube 1 is 10 μm, the interval W between the carbon nanotubes 1 is 3 μm.

  Here, it is preferable in terms of heat dissipation efficiency that the carbon nanotubes 1 protrude in a direction orthogonal to the heating body 2, but it is not always necessary to protrude in the orthogonal direction, and the carbon nanotubes 1 may protrude in different directions. .

  The length L of the carbon nanotube 1 is preferably 10 μm or more in order to make the specific surface area a certain size or more and to ensure heat exchange efficiency. However, the length L of the carbon nanotube 1 is determined according to the interval W at which the thermal radiation 6 resonates with the wavelength. The length L of the carbon nanotube 1 can be controlled by the CVD time, the supply time of the gas for growing the carbon nanotube, and the like.

  Moreover, the heat medium 4 which is a to-be-heated body should just have a fluidity | liquidity and a high heat absorption rate, such as a liquid, gas, and granular solid. For example, in the case of liquid, water, silicon oil, dowsum A or the like can be used as the heat medium 4, and in the case of gas, an inert gas such as nitrogen, argon or helium, air, or a vapor made of the above-described liquid. In the case of a granular material, metal, ceramic, etc. can be used. Further, when the heat medium 4 is a liquid or a granular material, an infrared absorbing material is used as an additive 7 that can absorb the heat radiation 6 emitted from the carbon nanotubes 1 or the heating body 2 and efficiently convert it into heat energy. 4 can also be added (FIG. 1B). Thus, the heat radiation 6 radiated from the carbon nanotube 1 or the heating body 2 is efficiently exchanged by adding the additive 7 having a high heat radiation absorption rate and high heat conversion efficiency to the heat medium 4. The heat from the heat source can be recovered efficiently. In addition, the additive 7 itself also functions as a heat transporter, and from this, the heat recovery efficiency can be improved. When the heat medium 4 has a particulate shape, if the particles are too small, the friction between the particles increases and the heat medium 4 becomes difficult to flow. If the particles are large, the space between the particles increases and the amount of heat that can be absorbed decreases. . Therefore, in order to ensure fluidity and reduce the porosity, the particle diameter is preferably 10 μm or more and 100 μm or less. Further, as the additive 7, chromium oxide, copper oxide, indium oxide, monel oxide, nichrome oxide, iron oxide, cast iron, molybdenum oxide, nickel oxide, steel oxide, titanium oxide, SiC, or the like can be used.

  Furthermore, carbon nanotubes can also be added as the additive 7. Carbon nanotubes are excellent as additive 7 because they have high heat absorption and high thermal conductivity. Thus, by adding the carbon nanotubes having high heat absorption and high thermal conductivity as the additive 7, high heat recovery efficiency can be realized as compared with other additive materials. In addition, the same heat recovery efficiency can be realized with a small addition amount. As a result, heat exchange can be made highly efficient.

  Further, when the heat source is a high temperature and the heat medium 4 is a gas containing oxygen or a material that oxidizes the carbon nanotubes 1, the carbon nanotubes 1 are combusted or altered during heat exchange, and the efficiency of heat radiation is increased. May decrease. Thus, when the carbon nanotube 1 is used in a high temperature and oxygen atmosphere, a coating film 8 may be provided on the surface of the carbon nanotube 1 in order to improve heat resistance and environmental resistance (FIG. 3B). )). Thus, by coating the surface of the carbon nanotube 1 with the coating film 8, the heat resistance and environmental resistance of the carbon nanotube 1 can be improved, and at the same time, a high-temperature heat source can be used as a target. Therefore, a large amount of heat can be transferred in a short time due to the temperature difference between the heat source and the carbon nanotubes 1, which can contribute to high efficiency of heat conduction.

  The coating film 8 is preferably made of a material having high heat resistance, acid resistance and other environmental resistance, infrared absorption rate, and high thermal conductivity, such as chromium oxide, copper oxide, indium oxide, monel oxide, oxidation. Nichrome, iron oxide, oxidized iron, molybdenum oxide, nickel oxide, oxidized steel, titanium oxide, SiC and the like can be used. Further, depending on the wavelength of heat radiation, ceramic such as silicon carbide having high heat release efficiency may be used as the coating film 8. Further, if there is a gap in the coating film 8, the carbon nanotubes 1 may be exposed through the gap, and the portion may be burned or altered. Therefore, the coating is preferably performed densely on the entire surface of the carbon nanotube 1 without any gap from the root to the tip.

  Further, when the material of the coating film 8 is smaller in thermal conductivity than the carbon nanotube 1, the thermal conductivity of the coated carbon nanotube 1 is lowered. Therefore, the thickness of the coating film 8 is preferably 100 nm or less. On the contrary, if the coating film 8 is too thin, heat resistance, environmental resistance, etc. cannot be ensured. Therefore, the film thickness of the coating film 8 is preferably 5 nm or more.

In addition, also when using a carbon nanotube as the additive 7, you may provide a coating film similarly to the above.
Moreover, you may use what bundled the several carbon nanotube 1 as a carbon nanotube (FIG.2 (c)). In this case, the interval W between the carbon nanotubes is the distance between the center positions of the bundled carbon nanotubes. As described above, by using bundled carbon nanotubes, the strength is increased as compared with the case where single carbon nanotubes are arranged at intervals W. Further, since the carbon nanotubes can be easily bundled by a method such as dropping as described later, strong carbon nanotubes can be easily arranged at a predetermined interval W. Further, the individual carbon nanotubes to be bundled may be coated as described above. As described above, the length of each bundled carbon nanotube is preferably 10 μm or more. Further, a groove structure 16 (FIG. 2 (d)) formed with bundled carbon nanotubes on the inner surface of the heating body 2 and having an interval W, or an array structure of triangular pyramids arranged at equal intervals W vertically and horizontally 17 (FIG. 2E) may be formed.

Next, a method for producing carbon nanotubes with controlled intervals will be described with reference to FIGS. 2 and 4 to 6.
FIG. 4 is a process diagram for explaining a method for producing carbon nanotubes in which the interval is controlled by aggregation of the catalyst, FIG. 5 is a process diagram for explaining a method for producing carbon nanotubes in which the interval is controlled by injection of local gas, and FIG. It is process drawing explaining the manufacturing method of the carbon nanotube bundled.

  First, a layered catalyst 9 is formed on the inner wall of the tubular heating body 2 of the heat exchanger (FIGS. 4A, 5A, and 6A). The catalyst 9 is a single alloy of Fe, Co, Ni, or two or more alloys.

  Next, the layered catalyst 9 is heated to form the particulate catalyst 10 supported on the inner wall of the heating body 2 (FIGS. 4B, 5B, and 6B). Further, the layered catalyst 9 is etched (removed unnecessary catalyst 9) by a method such as photolithography so as to have a predetermined particle interval, and heated to atomize to form the particle catalyst 10. May be.

  Although the case where the layered catalyst 9 is formed into a particulate catalyst 10 has been described as an example, the granulated catalyst 10 is supported on the inner surface of the tubular heating body 2 by solution impregnation or a spray method. You can also At this time, the particle interval can be adjusted by the solution concentration, and the particle interval increases as the concentration decreases. Further, a portion having high or low wettability is formed on the inner surface of the tubular heating body 2 using a mask or the like, and the granular catalyst 10 is impregnated by solution impregnation or spraying to form a tubular heating body. 2 may be carried on the inner surface.

  Next, when the interval W between the carbon nanotubes 1 is controlled by aggregation, the particulate catalyst 10 is heated to increase the particle diameter and increase the particle interval so that the catalyst 10 is arranged at a constant interval. Aggregates into particulate aggregates. At this time, the aggregates are arranged at equal intervals in the vertical and horizontal directions. The interval is controlled by the heating time, and this interval is made to coincide with the desired interval W of the carbon nanotubes 1. For example, when the heating time is short, the particle diameter of the aggregate 11 is small and the interval is small (FIG. 4C). Conversely, when the heating time is long, the particle size of the aggregate 12 is large and the interval is also large (FIG. 4 (d)).

  Finally, the carbon nanotubes 1 that are oriented in the direction protruding from the inner wall of the heating element 2 are grown by vapor deposition such as CVD using the aggregate formed at the interval W between the desired carbon nanotubes 1 (FIG. 4 (e), FIG. 4 (f)). As a result, a sword mountain structure of carbon nanotubes 1 arranged in a sword mountain shape is formed. This sword mountain-like structure controls the length of the carbon nanotubes 1 and the distance W between them such that the heat radiation radiated in accordance with the temperature of the heat source resonates.

  When the interval is controlled by local gas injection, after the particulate catalyst 10 supported on the inner wall of the heating body 2 is formed (FIG. 5B), the catalyst 10 is heated by heating for a certain time. Aggregates into particulate aggregates 13 arranged at regular intervals (FIG. 5C). Then, by selectively injecting the local gas 14 to the aggregates 13 at intervals W of the desired carbon nanotubes 1 (FIG. 5D), only the aggregates 13 at the desired intervals W are fixed in a certain direction. The carbon nanotubes 1 having a desired interval W are formed (FIG. 5E). The gas for growing the carbon nanotubes used here is basically a hydrocarbon gas, and uses acetylene, ethylene, methane, ethane or the like.

  Further, when the carbon nanotubes 1 are bundled, after the particulate catalyst 10 supported on the inner wall of the heating body 2 is formed (FIG. 6B), the catalyst 10 is fixed for a certain period of time by heating. Aggregates into particulate aggregates 13 arranged at intervals (FIG. 6C). Next, the aggregate 13 is grown in a certain direction to form the carbon nanotube 1 (FIG. 6D). The interval between the carbon nanotubes 1 formed at this time is not particularly limited, but is not more than half of the desired interval W (about 1/10 to 1/50 of the interval W when the interval W is 500 to 1000 nm). In addition, the formation method of the carbon nanotube 1 so far may be formed by any of the methods described in FIG. 4 or FIG. 5, but only the interval between the carbon nanotubes 1 is different. Next, a liquid 15 such as a water droplet is dropped at every interval W (FIG. 6E). Thus, by dropping the liquid 15 onto the plurality of carbon nanotubes 1, the carbon nanotubes 1 in the region where the liquid 15 is dropped are entangled and bundled (FIG. 6 (f)). Thereby, the interval between the bundled carbon nanotubes 1 becomes W (FIG. 2C). In the figure, the case where two carbon nanotubes 1 are bundled has been described. However, by adjusting the dropping position and amount of the liquid 15, a plurality of carbon nanotubes 1 are bundled and bundled at a predetermined interval W. Carbon nanotubes are formed.

  In the above description, the figure shows a diagram in which the interval is controlled only in the flow direction of the heating medium of the heating body 2, but the carbon nanotubes 1 are similarly formed at the same interval in the direction orthogonal to the flow direction. .

  In particular, when the carbon nanotubes 1 are bundled, the vicinity of the center of the four carbon nanotubes 1 forming a square with the two carbon nanotubes 1 adjacent to each other in the flow direction and the two carbon nanotubes 1 adjacent in the direction perpendicular to the flow direction. It is also possible to control the bundle of four carbon nanotubes 1 by dropping the liquid 15 into the bundle so that the interval between the bundled carbon nanotubes becomes W.

Alternatively, the carbon nanotubes 1 may be formed regardless of the desired interval W, and the desired interval W may be obtained by removing unnecessary carbon nanotubes 1 with a laser or the like.
Further, in the above description, the method of forming the carbon nanotubes 1 directly oriented on the inner surface of the heating body 2 has been described. However, the carbon nanotubes 1 are formed on the substrate at regular intervals by the above method. Alternatively, the substrate on which is formed may be attached to the inner surface of the heating body 2 or the carbon nanotubes 1 may be transferred to the inner surface of the heating body 2.

DESCRIPTION OF SYMBOLS 1 Carbon nanotube 2 Heating body 3 Heat exchanger 4 Heat medium 5 Convective heat transfer 6 Heat radiation 7 Additive 8 Coating film 9 Catalyst 10 Catalyst 11 Aggregate 12 Aggregate 13 Aggregate 14 Local gas 15 Liquid 16 Groove structure 17 Triangular pyramid Array structure

Claims (4)

A heat exchanger for recovering heat from a heat source,
A tubular heating body;
A heating medium filled inside the tube of the heating body;
Carbon nanotubes having an orientation structure projecting toward the heat medium on the inner surface of the tube of the heating body with a predetermined length determined in advance,
The heat exchanger characterized in that the carbon nanotubes have a sword mountain structure arranged at predetermined intervals, and the sword mountain structure resonates the heat radiation emitted corresponding to the temperature of the heat source. .   Single, or two or more composites made of Ti, Cu, Cr, Fe, Co, Ni, Zn, Au, Ag, Si, or oxides, carbides, and nitrides thereof on the surface of the carbon nanotube. The heat exchanger according to claim 1, wherein a coating layer is provided.   Si, Al, Mg, Fe, Co, Ni, Cu, Zn, Mo, Ru, Ag, Pt, Au, Ti, Cr alone, carbide, nitride, or two or more of the heat medium The heat exchanger according to claim 1, wherein an infrared absorbing material containing a composite of the above is added. A method of manufacturing a heat exchanger that recovers heat from a heat source,
A step of arranging a granular catalyst in a sword mountain shape at a predetermined interval on the inner surface of the tubular heating body;
Forming a carbon nanotube oriented in a direction protruding from the inner wall of the heating body by growing the catalyst to a predetermined length, and the sword mountain structure in which the carbon nanotubes are arranged is at the temperature of the heat source. A method of manufacturing a heat exchanger, characterized by resonating correspondingly emitted heat radiation.

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