Patent Application
20200224976
The present invention relates to a copper porous body for vaporization members used as a vaporization member which vaporizes a liquid phase medium that comes into contact with the vaporization member, an evaporative cooler including this copper porous body for vaporization members, and a heat pipe.
Priority is claimed on Japanese Patent Application No. 2017-216634, filed on Nov. 9, 2017, the content of which is incorporated herein by reference.
For example, as a device which cools a heating element such as a semiconductor element of a semiconductor device with excellent efficiency, for example, an evaporative cooler which vaporizes a liquid phase medium by heat from a heating element and cools the heating element using evaporation latent heat in this case, and a heat pipe are provided, as disclosed in PTL 1 and PTL 2.
In the evaporative cooler, it is proposed that a metal porous body having a three-dimensional network structure is disposed on a boiling unit which vaporizes a liquid phase medium, in order to improve heat transmission to efficiently vaporize the liquid phase medium.
In addition, in the heat pipe, it is proposed that a metal porous body having a three-dimensional network structure is disposed as a wick in a pipe body.
This metal porous body includes a stem linked in a three-dimensional manner. A linking hole linked in a three-dimensional manner is formed in this stem, and a specific surface area of the stein increases. Accordingly, a contact area with the liquid phase medium which flows to the linking hole increases. Therefore, by heating the liquid phase medium through the metal porous body, it is possible to efficiently vaporize the liquid phase medium.
As described above, in a case where the gas phase medium vaporized from the metal porous body is not rapidly discharged, the flowing of the liquid phase medium is prevented, and the liquid phase medium may not be efficiently vaporized.
Therefore, PTL 1 proposes a porous body having a structure in which a first porous layer and a second porous layer having porosities different from each other are laminated. In the structure of the porous body disclosed in PTL 1, the vaporization of the liquid phase medium is promoted in the first porous layer having a low porosity, and the discharge of the gas phase medium is promoted in the second porous layer having a high porosity.
[PTL 1] Japanese Unexamined Patent Application, First Publication No. 2013-243249
[PTL 2] Japanese Unexamined Patent Application, First Publication No. H08-047113
As disclosed in PTL 1, in a structure in which a first porous layer and a second porous layer having porosities different from each other are laminated, a size of a metal porous body disposed in a boiling unit (evaporation unit) may increase, a degree of freedom of a device design of an evaporative cooler and a heat pipe may decrease. In addition, the structure of the evaporative cooler and the heat pipe may be complicated and the manufacturing cost may increase.
In a case where the first porous layer having a low porosity is used in the laminated structure, a liquid phase medium may not be efficiently vaporized, in a case where the discharge of a gas phase medium is not rapidly performed.
The invention is made in view of such circumstances, and an object of the invention is to provide a copper porous body for vaporization members capable of ensuring a contact surface with a liquid phase medium, efficiently discharging a gas phase medium, and efficiently vaporizing a liquid phase medium by heat from a heating element, and an evaporative cooler and a heat pipe including this copper porous body for vaporization members.
In order to solve such a problem and achieve the aforementioned object, a copper porous body for vaporization members of the invention is a copper porous body for vaporization members used as a vaporization member which vaporizes a liquid phase medium that comes into contact with the vaporization member, in which the copper porous body is composed of a sintered body of a plurality of copper fibers and has a stem having a three-dimensional network structure. A porosity is in a range of 65% or more and 95% or less, an opening diameter is in a range of 100 μm or more and 2,000 μm or less, and a standardized specific surface area SD=S×R defined as a product of a specific surface area S (m2/g) and a diameter R (m) of the copper fiber is in a range of 0.001 or more and 0.25 or less.
The copper porous body for vaporization members having this configuration includes the stem having a three-dimensional network structure, and the standardized specific surface area SD=S×R defined as a sum of the specific surface area S (m2/g) and the diameter R (m) of the copper fiber is in a range of 0.001 or more and 0.25 or less. Accordingly, a surface of the stem is suitably roughened, a contact surface with the liquid phase medium is sufficiently ensured, and it is possible to efficiently vaporize the liquid phase medium.
Since the opening diameter is in a range of 100 μm or more and 2,000 μm or less, the contact surface with the liquid phase medium is ensured, and it is possible to efficiently discharge the gas phase medium.
Since the porosity is in a range of 65% or more and 95% or less, the contact surface with the liquid phase medium is ensured, and it is possible to efficiently discharge the gas phase medium.
In addition, by using a copper porous body for vaporization members having a single phase structure, it is possible to sufficiently ensure the contact surface with the liquid phase medium. Therefore, it is possible to efficiently discharge the gas phase medium.
In the copper porous body for vaporization members of the invention, the diameter R of the copper fiber is in a range of 0.02 mm or more and 1 mm or less, and a ratio L/R of a length L to the diameter R of the copper fiber is preferably in a range of 4 or more and 2,500 or less.
In a case of using this configuration, voids are suitably formed, in a case where the copper fibers are laminated on each other. Accordingly, it is possible to comparatively easily adjust the porosity and the opening diameter, and it is possible to set the porosity to be in a range of 65% or more and 95% or less and the opening diameter to be in a range of 100 μm or more and 2,000 μm or less.
An evaporative cooler of the invention includes a boiling unit which receives heat from a heating element to vaporize a liquid phase medium, and the copper porous body for vaporization members described above is disposed in the boiling unit.
In the evaporative cooler having this configuration, the copper porous body for vaporization members described above is disposed in the boiling unit. Accordingly, it is possible to discharge a gas phase medium, in a case where a liquid phase medium and the copper porous body for vaporization members sufficiently come into contact with each other in the boiling unit, and it is possible to efficiently vaporize the liquid phase medium.
That is, in the boiling unit, it is possible to promote the boiling of the liquid phase medium. Therefore, it is possible to significantly improve cooling performance of the evaporative cooler.
In addition, the copper porous body for vaporization members having a single phase structure can sufficiently come into contact with a liquid phase medium. Therefore, it is possible to efficiently discharge a gas phase medium and simplify the structure of the evaporative cooler.
A heat pipe of the invention includes an evaporation unit which receives heat from a heating element to vaporize a liquid phase medium, and a condensation unit which liquefies the gas phase medium generated by the evaporation unit, and the copper porous body for vaporization members described above is disposed as a capillary structure (evaporation unit wick) provided in the evaporation unit.
In the heat pipe having this configuration, the copper porous body for vaporization members described above is disposed as the capillary structure (evaporation unit wick) disposed in the evaporation unit. Therefore, it is possible to discharge a gas phase medium, in a case where a liquid phase medium and the copper porous body for vaporization members sufficiently come into contact with each other in the evaporation unit, and it is possible to efficiently vaporize the liquid phase medium. Thus, it is possible to significantly improve heat exchanging efficiency of the heat pipe. In addition, the copper porous body for vaporization members having a single phase structure can sufficiently come into contact with a liquid phase medium. Therefore, it is possible to efficiently discharge the gas phase medium and to simplify the structure of the heat pipe.
According to the invention, it is possible to provide a copper porous body for vaporization members capable of ensuring a contact surface with a liquid phase medium, efficiently discharging a gas phase medium, and efficiently vaporizing a liquid phase medium by heat from a heating element, and an evaporative cooler and a heat pipe including this copper porous body for vaporization members.
Hereinafter, a copper porous body for vaporization members, an evaporative cooler, and a heat pipe according to embodiments of the invention will be described with reference to the accompanying drawings.
First, a copper porous body for vaporization members and an evaporative cooler according to a first embodiment of the invention will be described with reference to
An evaporative cooler 1 of the first embodiment is, for example, used for cooling a semiconductor element which is a heating element in a semiconductor device for power control.
As shown in
The heating medium exists in a liquid phase state and a gas phase state in the sealed container 2 and is configured to cool a heating element H by evaporation latent heat of the heating medium.
The condensation unit 7 is configured to cool and liquefy a heating medium in a gas phase state (gas phase medium). In the condensation unit 7, a cooling flow path 8, through which a cooling medium flows, is disposed, and the heating medium in a gas phase state is cooled and liquefied by this cooling flow path 8.
The boiling unit 3 is configured to receive heat from the heating element H, and heats and vaporizes a heating medium in a liquid phase state (liquid phase medium). As shown in
As shown in
The copper porous body for vaporization members 10 has a porosity P of in a range of 65% or more and 95% or less. The porosity P is derived by the following equation.
P(%)=(1−(m/(V×DT)))×100
m: mass of copper porous body for vaporization members 10 (g)
V: volume of copper porous body for vaporization members 10 (cm3)
DT: true density of copper fibers 11 configuring copper porous body for vaporization members 10 (g/cm3)
In addition, the copper porous body for vaporization members 10 includes a void opened to the outside, and an opening diameter U of this void is in a range of 100 μm or more and 2,000 μm or less. The copper porous body for vaporization members 10 is configured with a sintered body of a plurality of copper fibers 11, and the opening diameter U is standardized as a cube having a square opening hole, as shown in
First, in
a
2=π×(R/2)2
A material percentage Q=(100−P) is calculated from the porosity P, and the opening diameter U was regulated to satisfy the following equation.
Q/100=(a3+3×U×a2)/(a+U)3
In the copper porous body for vaporization members 10, a standardized specific surface area SD=S×R defined as a sum of a specific surface area S (m2/g) and the diameter R (m) of the copper fiber 11 is in a range of 0.001 or more and 0.25 or less.
The measured specific surface area increases, as the diameter R of the copper fiber 11 decreases. Accordingly, in order to evaluate ruggedness formed on the surface of the stem 12, it is necessary to consider the diameter R of the copper fiber 11. Therefore, in the first embodiment, the standardized specific surface area SD defined as a sum of the specific surface area S (m2/g) and the diameter R (m) of the copper fiber 11 is regulated, and the ruggedness formed on the surface of the stem 12 is evaluated.
The copper fiber 11 configuring the stem 12 is formed of copper or copper alloy, the diameter R is in a range of 0.02 mm or more and 1 mm or less, and a ratio L/R of a length L to the diameter R of the copper fiber 11 is in a range of 4 or more and 2,500 or less. The copper fiber 11 is, for example, configured with C1020 (oxygen free copper).
The shaping such as twisting or bending is performed on the copper fiber 11. An apparent density ratio DA of the copper porous body for vaporization members 10 is 36% or less of the true density DT of the copper fiber 11. The shape of the copper fiber 11 may be any of a straight line or a curved line, as long as the apparent density ratio DA is 36% or less of the true density DT of the copper fiber 11. However, in a case of using the copper fiber 11, part of which is subjected to the predetermined shaping by twisting or bending, it is possible to three-dimensionally and isotropically form void shapes between the copper fibers 11, thereby contributing to the improvement of isotropy of various properties such as thermal conductivity of the copper porous body for vaporization members 10.
The copper fiber 11 is manufactured by cutting to adjust the diameter to the predetermined diameter R and adjust the length to a length so as to satisfy the predetermined L/R, by a drawing method, a coil cutting method, a chatter cutting method, a wire cutting method, and a melt spinning method. The diameter R is a value calculated based on a cross section of each fiber. The cross-sectional shape is assumed as a perfect circle, and the diameter is defined by the following equation.
R=(A/π)1/2×2
As shown in
The specific surface area increases due to the ruggedness of the porous layer 13, and the standardized specific surface area SD=S×R is in a range of 0.001 or more and 0.25 or less.
Hereinafter, a reason for regulating the porosity P, the opening diameter U, the standardized specific surface area SD, the diameter R of the copper fiber 11, and the ratio L/R of the length L of the copper fiber 11 to the diameter R of the copper porous body for vaporization members 10 will be described.
(Porosity P)
In a case where the porosity P of the copper porous body for vaporization members 10 is less than 65%, the gas phase medium may not be efficiently discharged from the copper porous body for vaporization members 10. On the other hand, in a case where the porosity P of the copper porous body for vaporization members 10 is more than 95%, the contact state with the liquid phase medium become insufficient, and the liquid phase medium may not be efficiently vaporized.
As described above, the porosity P of the copper porous body for vaporization members 10 is regulated to be in a range of 65% or more and 95% or less. In order to more efficiently discharge the gas phase medium from the copper porous body for vaporization members 10, the lower limit of the porosity P is preferably equal to or more than 70%. In addition, in order to more efficiently vaporize the liquid phase medium, the upper limit of the porosity P is preferably equal to or less than 93%.
(Opening Diameter U)
In a case where the opening diameter U of the copper porous body for vaporization members 10 is smaller than 100 μm, the gas phase medium may not be efficiently discharged from the copper porous body for vaporization members 10. On the other hand, in a case where the opening diameter U of the copper porous body for vaporization members 10 is greater than 2,000 μm, the contact state with the liquid phase medium becomes insufficient, and the liquid phase medium may not be efficiently vaporized.
As described above, the opening diameter U of the copper porous body for vaporization members 10 is regulated to be in a range of 100 μm or more and 2,000 μm or less. In order to more efficiently discharge the gas phase medium from the copper porous body for vaporization members 10, the lower limit of the opening diameter U is preferably equal to or greater than 500 μm. In addition, in order to more efficiently vaporize the liquid phase medium, the upper limit of the opening diameter U is preferably equal to or smaller than 1,700 μm.
(Standardized Specific Surface Area SD)
In a case where the standardized specific surface area SD of the copper porous body for vaporization members 10 is smaller than 0.001, the contact state with the liquid phase medium becomes insufficient, and the liquid phase medium may not be efficiently vaporized. In a case where the standardized specific surface area SD of the copper porous body for vaporization members 10 is greater than 0.25, the ruggedness formed on the stem 12 excessively increases, and the passing of the liquid phase medium or the gas phase medium may be inhibited.
As described above, the standardized specific surface area SD of the copper porous body for vaporization members 10 is regulated to be in a range of 0.001 or more and 0.25 or less. In order to more efficiently vaporize the liquid phase medium, the lower limit of the standardized specific surface area SD is preferably equal to or greater than 0.02 and more preferably equal to or greater than 0.166.
(Diameter R of Copper Fiber 11)
By setting the diameter R of the copper fiber 11 to be equal to or greater than 0.02 mm, the bonding area between the copper fibers 11 is ensured, and it is possible to ensure thermal conductivity. On the other hand, by setting the diameter R of the copper fiber 11 to be equal to or smaller than 1 mm, the number of points of contact between the copper fibers 11 is ensured, and it is possible to ensure thermal conductivity.
As described above, the diameter R of the copper fiber 11 is regulated to be in a range of 0.02 mm or more and 1 mm or less. In order to further ensure the bonding area between the copper fibers 11, the lower limit of the diameter R of the copper fiber 11 is preferably equal to or greater than 0.05 mm. In addition, in order to further ensure the number of points of contact between the copper fibers 11, the upper limit of the diameter R of the copper fiber 11 is preferably equal to or smaller than 0.8 m.
(Ratio L/R of Length L to Diameter R of Copper Fiber 11)
By setting the ratio L/R of the length L to the diameter R of the copper fiber 11 to be equal to or greater than 4, the bulk density DA decreases, in a case where the copper fibers are laminated on each other, and it is possible to obtain the copper porous body for vaporization members 10 having a high porosity P. On the other hand, by setting the ratio L/R of the length L to the diameter R of the copper fiber 11 to be equal to or smaller than 2,500, it is possible to evenly disperse the copper fibers 11, in a case where the copper fibers are laminated on each other, and it is possible to obtain the copper porous body for vaporization members 10 having an even porosity P.
As described above, the ratio L/R of the length L to the diameter R of the copper fiber 11 is set to be in a range of 4 or more and 2,500 or less. In a case of realizing further improvement of the porosity P, the lower limit of the ratio L/R of the length L to the diameter R of the copper fiber 11 is preferably equal to or greater than 5. In addition, in order to obtain the copper porous body for vaporization members 10 having an evener porosity P, the upper limit of the ratio L/R of the length L to the diameter R of the copper fiber 11 is preferably equal to or smaller than 1,000.
Next, a method for manufacturing the copper porous body for vaporization members 10 will be described with reference to a flowchart of
First, as shown in
In this copper fiber laminating step S01, the plurality of copper fibers 11 are laminated so that the bulk density DA after the filling becomes 35% or less of the true density DT of the copper fiber 11. The shaping such as twisting or bending is performed on the copper fibers 11. Accordingly, three-dimensional and isotropical voids are ensured between the copper fibers 11, in a case where the copper fibers are laminated on each other.
Next, the copper fibers 11 filled in the stainless steel container 32 is subjected to an oxidation reduction process (oxidation reduction process step S02).
As shown in
As shown in
In the oxidation process step S21, in order to suitably form the oxide layer on the surface of the copper fiber 11, the lower limit of the oxygen concentration in the atmosphere is preferably equal to or more than 7 vol %, the upper limit thereof is preferably equal to or less than 9 vol %, the lower limit value of the holding temperature is preferably equal to or higher than 600° C., and the lower limit value of the holding time is preferably equal to or less than 250 minutes.
As shown in
The atmosphere in the reduction process step S22 can be, for example, a mixed gas atmosphere of nitrogen and hydrogen.
In addition, in the reduction process step S22, the holding temperature is in a range of 500° C. to 1,000° C. and the holding time at the holding temperature is in a range of 10 minutes to 1,000 minutes.
In the reduction process step S22, in order to form the porous layer 13 by reliably reducing the oxide layer formed on the surface of the copper fiber 11, the lower limit of the holding temperature is preferably equal to or higher than 600° C., and the lower limit of the holding time is preferably equal to or longer than 30 minutes.
As described above, the oxide layer is formed on the surface of the copper fiber 11 by the oxidation process step S21, and the plurality of copper fibers 11 are crosslinked to each other by this oxide layer. After that, by performing the reduction process S22, the oxide layer formed on the surface of the copper fiber 11 is reduced and the porous layer 13 is formed.
Next, after forming the porous layer 13 by the oxidation reduction process step S02, the stainless steel container 32 filled with the copper fiber 11 is put into a sintering furnace 35, and the copper fibers 11 are sintered to each other (sintering step S03).
Under the conditions of the sintering step S03, the atmosphere is an inert gas atmosphere such as Ar or N2 (in the first embodiment, Ar gas atmosphere), the holding temperature is in a range of 600° C. to 1,080° C., and the holding time at the holding temperature is in a range of 5 minutes to 300 minutes. By performing this sintering step S03, the sintering of the copper fibers 11 proceeds. In addition, in a case where a closed void is formed in the reduction process step S22, the closed pore is removed by volume diffusion.
In a case where the holding temperature in the sintering step S03 is lower than 600° C., the volume diffusion does not sufficiently proceed, and the sintering may be insufficient. On the other hand, in a case where the holding temperature in the sintering step S03 is higher than 1,080° C., the shape may not be maintained due to the heating at a temperature close to a melting point of the copper, and a deterioration in hardness and porosity may occur.
From the above description, the holding temperature in the sintering step S03 is set to be 600° C. to 1,080° C. In order to reliably perform the sintering of the copper fibers 11, the lower limit of the holding temperature in the sintering step S03 is preferably equal to or higher than 700° C. In addition, in order to reliably prevent a deterioration in hardness and porosity, the upper limit of the holding temperature in the sintering step S03 is preferably equal to or less than 1,000° C. In a case of performing the sintering step S03 subsequent to the reduction process step S22, the holding temperature in the sintering step S03 and the holding temperature in the reduction process step S22 are preferably set to be the same temperature, from a viewpoint of energy saving.
By the manufacturing method described above, the stem 12, in which the copper fibers 11 and 11 are sintered to each other, is formed, and the porous layer 13 is formed on the surface of the stem 12. Accordingly, the copper porous body for vaporization members 10 is manufactured.
The copper porous body for vaporization members 10 having the configuration described above is formed of a sintered body of the plurality of copper fibers 11 and has a stem 12 having a three-dimensional network structure, and the standardized specific surface area SD=S×R defined as a sum of the specific surface area S (m2/g) and the diameter R (m) of the copper fiber 11 is in a range of 0.001 or more and 0.25 or less. Accordingly, the suitable ruggedness is formed on the surface of the stem 12, the contact area with the liquid phase medium is sufficiently ensured, and it is possible to efficiently vaporize the liquid phase medium.
Since the opening diameter U of the copper porous body for vaporization members 10 is equal to or greater than 100 μm and the porosity P thereof is equal to or more than 65%, it is possible to efficiently discharge the vaporized gas phase medium to outside of the copper porous body for vaporization members 10.
In addition, since the opening diameter U of the copper porous body for vaporization members 10 is equal to or smaller than 2,000 μm and the porosity P thereof is equal to or less than 95%, the contact area with the liquid phase medium is ensured, and it is possible to efficiently vaporize the liquid phase medium.
Since the diameter R of the copper fiber 11 is in a range of 0.02 mm or more and 1 mm or less and the ratio L/R of the length L to the diameter R of the copper fiber 11 is in a range of 4 or more and 2,500 or less, voids are three-dimensionally formed, in a case where the copper fibers are laminated, and it is possible to comparatively easily adjust the porosity P and the opening diameter U of the copper porous body for vaporization members 10.
In the evaporative cooler 1, the copper porous body for vaporization members 10 described above is disposed on the boiling unit 3, and the copper porous body for heating vaporization members 10 comes into contact with the heating element H through a wall surface of the sealed container 2. Accordingly, the heat of the heating element H is transmitted to the copper porous body for heating vaporization members 10, and the liquid phase medium is heated and vaporized.
In a case where the copper porous body for vaporization members 10 has the configuration described above, the liquid phase medium and the copper porous body for vaporization members 10 can sufficiently come into contact with each other, and the vaporized gas phase medium can be rapidly discharged to the outside of the copper porous body for vaporization members 10. Therefore, it is possible to efficiently vaporize the liquid phase medium. Thus, it is possible to significantly improve cooling performance of the evaporative cooler 1.
The copper porous body for vaporization members 10 having a single phase structure is disposed in the boiling unit 3, and the boiling unit has a configuration of sufficiently coming into contact with the liquid phase medium and efficiently discharging the gas phase medium, by this copper porous body for vaporization members 10. Therefore, it is possible to simplify the structure of the evaporative cooler 1.
Next, a heat pipe 51 according to a second embodiment of the invention will be described with reference to the accompanying drawings.
As shown in
The pipe main body 52 is preferably configured with metal having excellent thermal conductivity, for example, copper or a copper alloy, aluminum or an aluminum alloy, and in the second embodiment, the pipe main body is configured with oxygen free copper.
In the condensation unit 57, a cooling mechanism 58 is disposed outside of the pipe main body 52, and the condensation unit 57 is configured so as to cool and liquefy the heating medium in a gas phase state (gas phase medium) by this cooling mechanism 58. In the evaporation unit 53, the copper porous body for vaporization members 10 described above is disposed as an evaporation unit wick in the pipe main body 52. The copper porous body for vaporization members 10 disposed in the evaporation unit 53 is disposed so as to come into contact with the heating element H through a wall surface of the pipe main body 52.
The copper porous body for vaporization members 10 according to the first embodiment is disposed in the heat pipe 51 having the configuration described above, as the evaporation unit wick disposed in the evaporation unit 53. Accordingly, in the evaporation unit 53, the liquid phase medium and the copper porous body for vaporization members 10 sufficiently come into contact with each other, and the gas phase medium can be rapidly discharged from the copper porous body for vaporization members 10. Therefore, it is possible to efficiently vaporize the liquid phase medium. Thus, it is possible to significantly improve heat exchanging efficiency of the heat pipe 51.
The copper porous body for vaporization members 10 having a single phase structure can sufficiently come into contact with the liquid phase medium. Therefore, it is possible to efficiently discharge the gas phase medium and simplify the structure of the heat pipe 51.
Hereinabove, the embodiments of the invention have been described, but the invention is not limited thereto, and suitably modifications can be performed within a range not departing from technical ideas of the invention. For example, the copper porous body for vaporization members 10 manufactured by using the manufacturing facility shown in
In the embodiments of the invention, the use of the copper fiber formed of oxygen free copper (JIS C1020) has been described, but there is no limitation thereto, and pure copper such as phosphorus deoxidized copper (JIS C1201, C1220) or tough pitch copper (JIS C1100), and other copper alloys may be used.
The evaporative cooler 1 having the structure shown in
As an evaporative cooler 201 shown in
As an evaporative cooler 301 shown in
As an evaporative cooler 401 shown in
As shown in
Hereinafter, the result of confirmation experiment performed for confirming the effect to the invention will be described.
A copper porous sintered body having a width of 50 mm, a length of 50 mm, and a thickness of 2 mm was manufactured by the manufacturing method shown in the embodiment described above by using a sintering raw material (copper fiber) shown in Table 1. The condition of the oxidation process step was shown in Table 1. In addition, the reduction process step was performed under the condition of holding in an atmosphere of N2—3 vol % H2, for 1 hour at 600° C. The sintering step was performed under the condition of holding in N2 atmosphere at 600° C. for 1 hour.
The diameter R of the copper fiber which is a raw material and the ratio L/R of the length L to the diameter R were measured as follows. The porosity P, the opening diameter U, and the standardized specific surface area SD of the obtained copper porous sintered body were measured as follows. The vaporization efficiency of water was evaluated as follows.
(Diameter R of Copper Fiber)
A cross section of the copper fiber which is a sintering raw material orthogonal to a length direction was observed with an optical microscope, and a simple average value of a circle conversion diameter (Heywood diameter) R=(A/π)0.5×2 calculated by an imaging process by using the captured image was calculated. This was set as the diameter R of the copper fiber.
(Ratio L/R of Length L to Diameter R)
As the length L of the copper fiber, a simple average value calculated by performing image analysis with respect to the copper fiber which is a sintering raw material by using a particle analysis device “Morphologi G3” manufactured by Malvern Panalytical Ltd. was used. The ratio L/R of the length L to the diameter R was calculated by using this.
(Porosity P)
The true density DT (g/cm3) was measured by a water method using a precision balance and the porosity P was calculated by the following equation. A mass of the copper porous sintered body was shown with m (g), and a volume of the copper porous sintered body was shown with V (cm3).
Porosity P(%)=(1−(m/(V×DT)))×100
(Opening Diameter U)
As shown in the section of the embodiments and
a
2=π×(R/2)2
A material percentage Q=(100−P) is calculated from the porosity P, and the opening diameter U was regulated to satisfy the following equation.
Q/100=(a3+3×U×a2)/(a+U)3
(Standardized Specific Surface Area SD)
As the specific surface area S of the copper porous sintered body, a value measured by a BET method using krypton gas was used based on JIS Z8830. The standardized specific surface area SD=S×R was calculated from the measured specific surface area S (m2/g) and the diameter R (m) of the copper fiber.
(Vaporization Efficiency)
The obtained copper porous sintered body was disposed in a copper container, and this was placed on a heater set at 140° C. and sufficiently heated. After that, 3 g of water was added to the copper porous sintered body at one time. A temperature change in this case was measured using a thermocouple. An evaporation time, during which the temperature was decreased by adding water to obtain water in a boiling state, the temperature was set constant, water is totally evaporated and becomes vapor, and the temperature increases again, was evaluated. As this time is short, the vaporization efficiency becomes excellent.
In the example of the related art in which the oxidation reduction process is not performed, the standardized specific surface area SD was 0.0003 which was smaller than the range of the invention, and the evaporation time was 191 seconds. In Comparative Example 1 in which the porosity P was 61.6% which was smaller than the range of the invention, the evaporation time was 192 seconds. In Comparative Example 2 in which the porosity P was 96.5% which is greater than the range of the invention and the opening diameter U was 3,503 μm which was greater than the range of the invention, the evaporation time was 197 seconds. In Comparative Example 3 in which the opening diameter U was 42 μm which was smaller than the range of the invention, the evaporation time was 209 seconds.
In contrast, in Examples of the Invention 1 to 17 in which the porosity P, the opening diameter U, and the standardized specific surface area SD were in the range of the invention, the evaporation time was 176 seconds or shorter. In addition, the same effect can be also observed, in a case where the material of the copper fiber was changed.
From the above description, according to Examples of the Invention, it was found that, it is possible to provide a copper porous body for vaporization members, capable of ensuring the contact area with the liquid phase medium, efficiently discharging the gas phase medium, and efficiently vaporizing a liquid phase medium by heat from a heating element.
According to the invention, it is possible to provide a copper porous body for vaporization members capable of ensuring a contact surface with a liquid phase medium, efficiently discharging a gas phase medium, and efficiently vaporizing a liquid phase medium by heat from a heating element, and an evaporative cooler and a heat pipe including this copper porous body for vaporization members.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-216634 | Nov 2017 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2018/037085 | 10/3/2018 | WO | 00 |
