JP2019045105A - Heat transportation system - Google Patents

Abstract

To provide a heat transportation system that can suppress deposition of nanoparticles at a boiling surface of a heat transfer member.SOLUTION: A heat transportation system includes: a heat transfer member 30 with a boiling surface 32; and working fluid 70 coming into contact with the boiling surface 32 and containing a liquid medium and nanoparticles. The boiling surface 32 has an organic monomolecular film.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a heat transport system.

  The heat transport system is used as a heat transport means such as exhaust heat recovery. Therefore, it is considered that the heat transport system is applied to warm-up, heating, cooling, or the like. More specifically, the heat transport system is used as a heat pipe system for warming / heating that uses the exhaust heat of an automobile for engine warming, air conditioning, etc., or a cooling heat pipe system such as inverter cooling for an automobile. It is taken into account.

  The heat transport system can have, for example, a configuration as a heat pipe in which a working fluid as a heat medium is sealed inside a pipe made of metal or the like. In this case, the pipe made of metal or the like functions as a heat transfer member, and the boiling surface of the heat transfer member can come into contact with the working fluid sealed inside to boil the working fluid.

  In order to improve the heat transport efficiency in the heat transport system, it has been proposed that the working fluid of the heat transport system contains nanoparticles such as metal, metal oxide, carbon, and organic material (Patent Documents 1 and 2). ).

JP 2010-271022 A JP 2008-051389 A

  As described above, in order to improve the heat transport efficiency in the heat transport system, it has been proposed that the working fluid contains nanoparticles such as a metal material. However, the nanoparticles contained in such a working fluid accumulate over time on the boiling surface of the heat transfer member, thereby reducing the heat transfer efficiency of the boiling surface and reducing the heat transfer efficiency of the entire heat transfer system. There was something to do.

  Therefore, the present disclosure provides a heat transport system that can suppress deposition of nanoparticles on the boiling surface of the heat transfer member.

  As a result of examining the above problems, the present inventors have arrived at the following present disclosure.

<Aspect 1> A heat transfer member having a boiling surface, and a working fluid in contact with the boiling surface and containing a liquid medium and nanoparticles, and the boiling surface comprising an organic monomolecular film Having a heat transport system.
<Aspect 2> The heat transport system according to aspect 1, wherein the organic monomolecular film is composed of thiol.
<Aspect 3> The heat transport system according to aspect 2, wherein the thiol is selected from the group consisting of an alkanethiol having 6 or more carbon atoms and an aromatic thiol.
<Aspect 4> The heat transport system according to aspect 2 or 3, wherein the thiol is a fluorine-substituted thiol.
<Aspect 5> From the group consisting of perfluorodecanethiol, perfluorooctanethiol, perfluorohexanethiol, 4-trifluoromethyltetrafluorobenzenethiol, pentafluorobenzenethiol, and 4-trifluoromethylbenzenethiol. The heat transport system according to aspect 4, wherein the heat transport system is selected.
<Aspect 6> The heat transport system according to any one of aspects 1 to 5, wherein the boiling surface is made of metal.
<Aspect 7> The heat transport according to any one of aspects 1 to 6, wherein the nanoparticles are made of a material selected from the group consisting of metals, metal oxides, metal nitrides, and metal carbides. system.
<Aspect 8> The heat transport system according to any one of aspects 1 to 7, wherein the nanoparticles have an organic monomolecular film on the surface.

  According to the heat transport system of the present disclosure, deposition of nanoparticles on the boiling surface of the heat transfer member can be suppressed.

FIG. 1 is a schematic diagram for explaining an example of a configuration of a heat transport system of the present disclosure. FIG. 2 is a schematic cross-sectional view for explaining an example of the configuration of the heat exchanger used in the heat transport system of the present disclosure.

  A heat transport system of the present disclosure is a heat transport system including a heat transfer member having a boiling surface, and a working liquid that is in contact with the boiling surface and contains a liquid medium and nanoparticles. Has an organic monomolecular film.

  According to the heat transport system of the present disclosure, deposition of nanoparticles on the boiling surface of the heat transfer member can be suppressed.

  Without being limited to theory, this is due to the suppression of nanoparticles adhering to the boiling surface due to large steric hindrance, small surface energy, etc. of the organic monolayer on the boiling surface, and so on. This is thought to be due to the suppression of further nanoparticle adhesion to the nanoparticles adhered to the surface.

  Further, according to the heat transport system of the present disclosure, the adhesion of nanoparticles is suppressed by the organic monomolecular film as described above, while the increase in thermal resistance by the organic monomolecular film is not substantial.

  Without being limited to theory, this is due to the fact that the organic monolayer is very thin, thereby not substantially hindering heat transfer to the working fluid at the boiling surface of the heat transfer member. Conceivable. In contrast, when coating with a polymer such as a fluorinated polymer is performed, the resulting coating is relatively thick, thereby substantially preventing heat transfer to the working fluid on the boiling surface of the heat transfer member. It is thought that.

  The heat transport method using the heat transport system of the present disclosure is such that the temperature of the boiling surface of the heat transfer member is higher than the boiling point of the working fluid at a pressure near the boiling surface, for example, the temperature of the boiling surface of the heat transfer member. However, it can be carried out so that it is higher than the boiling point of the hydraulic fluid at a pressure near the boiling surface by 5 ° C. or more, 10 ° C. or more, 20 ° C. or more, 30 ° C. or more, 40 ° C. or more, or 50 ° C. or more. Further, for example, the difference between the temperature of the boiling surface of the heat transfer member and the boiling point of the hydraulic fluid at a pressure near the boiling surface is 200 ° C. or less, 150 ° C. or less, 100 ° C. or less, 70 ° C. or less, or 50 ° C. or less. It's okay.

  The heat source for supplying heat to the heat transfer member in the heat transport system of the present disclosure may be a gas, a liquid, a solid, or two or more of these. Examples of the gas include air, water vapor, ammonia, chlorofluorocarbon, and carbon dioxide. Examples of the liquid include water, brine, oil, and Dowsome A (registered trademark). Examples of the solid include a heater, and an air cooler for waste heat cooling.

The heat transport system of the present disclosure is not particularly limited as long as it includes the heat transfer member and the hydraulic fluid as described above, but in one aspect, as shown schematically in FIG. The disclosed heat transport system 300 can have the following configuration:
An evaporator 100 having a heat transfer member having a boiling surface and receiving heat input from the outside indicated by a white arrow to boil and vaporize the working fluid on the boiling surface of the heat transfer member;
A condenser 200 having a heat transfer member having a condensing surface, and condensing and liquefying the working fluid on the condensing surface of the heat transfer member with heat radiation to the outside indicated by an outline arrow;
As shown by the black arrow, the working liquid vaporized by the evaporator is supplied from the evaporator 100 to the condenser 200, and the working fluid liquefied by the gas flow path 10 and the condenser is condensed as shown by the black arrow. A liquid flow path 20 that is supplied from the vessel 200 to the evaporator 100.

In such an embodiment, the evaporator 100 can have the following configuration, as shown in the schematic cross-sectional view cut in the vertical plane in FIG.
A heat transfer member 30 having a boiling surface 32;
A hydraulic fluid 70 in contact with the boiling surface 32 and containing a liquid medium and nanoparticles, and a gas outlet 42 and a liquid supply port 44 and closed or open to the outside; A container 40.

In the use of the heat transport system of the present disclosure shown in FIG. 1, heat transport can be performed as follows:
In the evaporator 100, upon receiving heat input from the outside indicated by a white arrow, the working fluid 70 is boiled and vaporized on the boiling surface 32 of the heat transfer member 30,
The working fluid evaporated in the evaporator 100 is supplied from the evaporator 100 to the condenser 200 as shown by the black arrow in FIG.
In the condenser 200, the hydraulic fluid is condensed and liquefied on the condensation surface of the heat transfer member with heat radiation to the outside indicated by a white arrow, and the hydraulic fluid liquefied by the condenser 200 is converted into a liquid flow path. 20 through the condenser 200 to the evaporator 100 as shown by the black arrows in FIG.

  Here, in the evaporator 100, as shown in FIG. 2, the working liquid 70 containing the liquid medium and the nanoparticles is supplied from the liquid supply port 44 to the container 40 through the liquid flow path, and the white arrow In response to heat input from outside shown in FIG. 4, the heat transfer member 30 is boiled and vaporized on the boiling surface 32 of the heat transfer member 30 and discharged from the container 40 through the gas discharge port 42. In this vaporization, only the liquid medium in the hydraulic fluid is vaporized, and the nanoparticles are left in the hydraulic fluid.

<Heat transfer member>
The heat transfer member in the heat transfer system of the present disclosure has a boiling surface that comes into contact with the liquid medium and the working fluid containing the nanoparticles.

  In the heat transfer member, the ratio of the area of the boiling surface to the total area of the surface in contact with the hydraulic fluid is as high as possible from the viewpoint of performing stable boiling while maintaining the efficiency of heat exchange as high as possible. Is desired. The ratio of the area of the boiling surface to the total area of the surface in contact with the liquid in the heat transfer member may be, for example, 80% or more, 90% or more, or 95% or more, or 100%. .

  As long as the heat transfer member has the above boiling surface on the surface in contact with the hydraulic fluid, the size, shape, and the like may be appropriately set according to the characteristics of the hydraulic fluid to be used and the heat source. The shape of the heat transfer member may be, for example, a disk shape or a tubular shape.

  The boiling surface of the heat transfer member may be made of, for example, a material selected from the group consisting of a carbon-based material, a metal, and a semimetal, particularly a metal. Examples of the carbon-based material include carbon nanotubes, diamond, and artificial graphite. Examples of the metal include copper, aluminum, and stainless steel. An example of the semimetal is silicon.

  The boiling surface of the heat transfer member has an organic monomolecular film.

  The organic monomolecular film may be composed of, for example, thiol. In this case, the thiol group (—SH) of the thiol has a high affinity for the boiling surface, particularly the boiling surface composed of metal, so that the thiol group adheres to the boiling surface, thereby increasing the number of the thiol groups. The thiol is densely accumulated on the boiling surface to form a monomolecular film.

  This thiol preferably has a relatively large number of carbon atoms in order to increase the steric hindrance of the organic monomolecular film. Thus, for example, the thiol can be selected from the group consisting of alkane thiols having 6 or more carbon atoms and aromatic thiols. The carbon number of this thiol may be 8 or more, or 10 or more, and may be 20 or less, 15 or less, or 12 or less.

  In addition, this thiol preferably forms an organic monomolecular film having a low surface energy in order to suppress the adhesion of nanoparticles, and thus is a fluorine-substituted thiol in which hydrogen groups are partially or entirely substituted with fluorine groups. It may be.

  Specifically, as the fluorine-substituted thiol, from perfluorodecane thiol, perfluorooctane thiol, perfluorohexane thiol, 4-trifluoromethyltetrafluorobenzene thiol, pentafluorobenzene thiol, and 4-trifluoromethylbenzene thiol Mention may be made of fluorine-substituted thiols selected from the group consisting of

<Working fluid>
The hydraulic fluid used in the heat transport system of the present disclosure contains a liquid medium and nanoparticles dispersed in the liquid medium. This hydraulic fluid functions as a heat medium in the heat transport system.

  Examples of the liquid medium include water, a fluorine-based solvent, ammonia, acetone, alcohol, and the like. Among these, a fluorine-based solvent is preferable with respect to heat transfer efficiency.

  The nanoparticles may contribute to an improvement in the thermal conductivity of the hydraulic fluid. The nanoparticles may be composed of a material selected from the group consisting of metals, metalloids, and combinations thereof, and their oxides, nitrides, and carbides, particularly metals. Such metals and metalloids are, for example, selected from metals selected from gold, silver, platinum, copper, nickel, iron, aluminum, titanium, silicon, zinc, and zirconium, more particularly copper and aluminum. Mention may be made of metals. The nanoparticles may be composed of carbon or an organic material.

  The nanoparticles may be subjected to a surface treatment, and can have, for example, an organic monomolecular film on the surface. By subjecting the surface of the nanoparticles to surface treatment, aggregation of the nanoparticles in the hydraulic fluid can be suppressed. The nanoparticle organic monomolecular film may be the same as the boiling surface or may be different from the boiling surface.

  If the particle diameter of the nanoparticles is too large, precipitation of the nanoparticles in the working fluid may occur. Therefore, the upper limit of the average particle diameter of the nanoparticles may be 500 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, or 100 nm or less.

  On the other hand, the lower limit of the average particle diameter of the nanoparticles is not particularly limited as long as aggregation and precipitation of the nanoparticles can be suppressed by surface treatment of the nanoparticles. Therefore, the average particle diameter of the nanoparticles may be 10 nm or more, 20 nm or more, 30 nm or more, 40 nm or more, or 50 nm or more.

  The average particle diameter of the nanoparticles was measured by directly measuring the projected area circle equivalent diameter based on the photographed image by observation with a scanning electron microscope (SEM), transmission electron microscope (TEM), etc. The number average primary particle diameter can be obtained by analyzing the particle group.

  In the present disclosure, “nanoparticles” include non-spherical particles such as nanorods and nanowires. In this case, the length of the nanorod or nanowire may be, for example, 500 nm or more, or 1,000 nm or more, and may be 20,000 nm or less, 10,000 nm or less, or 5,000 nm or less.

  The working fluid in the present disclosure may contain a dispersant such as polyvinyl pyrrolidone in order to suppress aggregation of the nanoparticles in the working fluid.

  The present disclosure is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has the same configuration as the technical idea described in the claims of the present disclosure and has the same function and effect regardless of the present embodiment. It is included in the technical scope of the disclosure.

  In the following, the present disclosure will be further described using examples.

<Example 1>
(Preparation of copper nanoparticles)
Copper (II) chloride dihydrate 0.170 g (1 mmol), glucose 0.391 g (2 mmol), hexadecylamine 1.44 g (6 mmol) was added to 80 mL of ultrapure water and stirred for 5 hours to give an emulsion. Got. This emulsion was put in a pressure vessel and heated at 150 ° C. for 2 hours in a constant temperature dryer. Then, it wash | cleaned in order of the ultrapure water and hexane, 35 degreeC acetic acid was added, and the hexadecylamine was removed. After further centrifugation for 10 minutes at 13000 rpm, washing with hexane three times, and immersing in a liquid in which 1H, 1H, 2H, 2H-perfluorodecanethiol is dissolved in an organic solvent for 5 hours for 24 hours, The surface-treated copper nanoparticles were obtained.

(Production of hydraulic fluid)
A dispersant (high molecular weight polyvinyl pyrrolidone) was added to a fluorine-based refrigerant (Du Pont Cinera) as a liquid medium, and copper nanoparticles were dispersed to obtain a working fluid.

(Surface treatment of boiling surface)
The surface of the oxygen-free copper plate is polished in order of increasing abrasive particle size using lapping sheets (abrasive particle size: 3 μm, 1 μm, 0.5 μm) with different abrasive particle sizes, and the concentration is increased in a glove box under a nitrogen atmosphere. 7 vol. Wet etching soaked in% hydrochloric acid was performed and washed with water. Then, the copper plate was immersed in the liquid which melt | dissolved perfluorodecane thiol in hexane, the organic monomolecular film was formed in the boiling surface, and the copper plate as a heat-transfer member which has an organic monomolecular film in a boiling surface was obtained. It was confirmed that the monomolecular film was obtained by the measurement result that the film thickness was 2 nm or less by the X-ray reflectivity method (XRR).

(Evaluation of deposition position and thickness of copper nanoparticles)
In the sealed heat-resistant container, the working fluid containing the liquid medium and copper nanoparticles obtained as described above, and a copper plate as a heat transfer member having an organic monomolecular film on the boiling surface were placed, and the container was sealed. Thereafter, the entire sealed pressure vessel was placed in a constant temperature bath at 120 ° C., heated for 6 hours, then cooled, and the copper plate was taken out from the sealed pressure vessel.

  The cross section of the copper plate taken out from the sealed pressure vessel was observed using a scanning electron microscope, and the deposition position and thickness of the copper nanoparticles deposited on the boiling surface of the copper plate were evaluated. The evaluation results are shown in Table 1 below together with the types of molecules used to construct the organic monomolecular film.

<Examples 2 to 6>
A copper plate having an organic monomolecular film on the boiling surface was obtained in the same manner as in Example 1 except that the molecules used to construct the organic monomolecular film were changed as shown in Table 1. Similarly, the deposition position and thickness of the copper nanoparticles were evaluated. The evaluation results are shown in Table 1 below together with the types of molecules used to construct the organic monomolecular film.

<Comparative example 1>
The deposition position and thickness of the copper nanoparticles were evaluated in the same manner as in Example 1 except that a copper plate not subjected to surface treatment was used and the dispersant added to the working fluid was changed to low molecular weight polyvinylpyrrolidone. The evaluation results are shown in Table 1 below.

  As shown in Table 1, in Examples 1 to 6 having an organic monomolecular film on the boiling surface, copper nanoparticles were deposited only on a part of the boiling surface, and the deposition thickness of the copper nanoparticles was The maximum was 25 μm. On the other hand, as shown in Table 1, in Comparative Example 1 having no organic monomolecular film on the boiling surface, copper nanoparticles were deposited on the entire boiling surface, and the deposition thickness was 30 μm. . From this, it is possible to suppress the adhesion of copper nanoparticles to the boiling surface by having an organic monomolecular film on the boiling surface, and thereby to the boiling surface due to the further adhesion of copper nanoparticles to the deposited copper nanoparticles. It is understood that the deposition of copper nanoparticles can be suppressed.

DESCRIPTION OF SYMBOLS 10 Gas flow path 20 Liquid flow path 30 Heat transfer member 32 Boiling surface 40 Container 42 Gas discharge port 44 Liquid supply port 70 Working liquid 100 Evaporator 200 Condenser 300 Heat transport system

Claims (8)

A heat transfer member comprising a heat transfer member having a boiling surface; and a working fluid in contact with the boiling surface and containing a liquid medium and nanoparticles, wherein the boiling surface has an organic monomolecular film. system.   The heat transport system according to claim 1, wherein the organic monomolecular film is composed of thiol.   The heat transport system according to claim 2, wherein the thiol is selected from the group consisting of an alkanethiol having 6 or more carbon atoms and an aromatic thiol.   The heat transport system according to claim 2 or 3, wherein the thiol is a fluorine-substituted thiol.   The thiol is selected from the group consisting of perfluorodecanethiol, perfluorooctanethiol, perfluorohexanethiol, 4-trifluoromethyltetrafluorobenzenethiol, pentafluorobenzenethiol, and 4-trifluoromethylbenzenethiol, The heat transport system according to claim 4.   The heat transport system according to any one of claims 1 to 5, wherein the boiling surface is made of metal.   The heat transport system according to any one of claims 1 to 6, wherein the nanoparticles are made of a material selected from the group consisting of metals, metal oxides, metal nitrides, and metal carbides.   The heat transport system according to any one of claims 1 to 7, wherein the nanoparticles have an organic monomolecular film on a surface.

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