EVAPORATOR FOR LOOPED HEAT PIPE SYSTEM AND METHOD OF MANUFACTURING THE SAME

Abstract

An evaporator for a looped heat pipe (LHP) system, in which a working fluid circulates to cool a heat generating electronic component that generates heat during operation, the evaporator including: a body including an inlet through which the working fluid enters and an outlet through which the working fluid is discharged; a sintered wick that is included in the body, wherein the sintered wick is formed by sintering a copper powder, and a plurality of pores are formed in the sintered wick; and an additional layer that is formed on a surface of the sintered wick, wherein the additional layer is formed by sintering copper particles having a size smaller than that of the copper powder forming the sintered wick, and the working fluid moved from the sintered wick is changed in a vapor state to be discharged.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2012-0134877, filed on Nov. 26, 2012, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an evaporator that forms a looped heat pipe system with a condenser, a vapor transport line, and a liquid transport line, and a method of manufacturing the evaporator, and more particularly, to an evaporator for a looped heat pipe system, including an additional layer, which is formed by sintering nano-sized particles on an vaporization surface of a sintered wick inside the evaporator, and thus having improved cooling efficiency.

2. Description of the Related Art

Electronic components such as a central processing unit (CPU) or a semiconductor chip, used in various electronic devices such as computers or servers generate a lot of heat during operation. The electronic components are designed to perform their functions usually at room temperature, and thus if the heat generated during operation is not effectively dissipated, not only is performance of the electronic components degraded but the electronic devices are damaged in some circumstances.

As electronic products are reduced in size to be slim, installation intervals between electronic components thereof that generate heat during operation are continuously reduced, and thus, currently, the heat generated during use of the electronic products is not properly dissipated. Also, due to the high integration degree and high performance of the electronic components, a heat generation load of the electronic components is continuously increasing, and thus it is difficult to cool the electronic components using conventional cooling methods.

As a new technology for solving this problem, a phase change heat transport system capable of cooling electronic components having a highly thermal density has been introduced.

One example of the phase change heat transport system is a cylindrical heat pipe. As illustrated in FIG. 1, a typical cylindrical heat pipe 100 is used to perform cooling as a working fluid is circulated using a capillary pumping force of a sintered wick 102 installed on an inner wall of the cylindrical heat pipe 100.

Upon receiving heat from a heat source 101, the working fluid contained in the sintered wick 102 is evaporated and is transferred along an arrow 103 denoting a vapor flow, and then heat of the working fluid is taken away by a heat sink 104, and the working fluid is condensed again and flows through the sintered wick 102 along an arrow 105 denoting a liquid flow, by a capillary pumping force, to thereby circulate.

However, although dependence of a heat pipe on a gravity field is low, there are still limitations regarding arrangement of components; for example, if a condensation section is located below an evaporation section in a gravity field, heat transport capability of the heat pipe decreases greatly. Thus, if the heat pipe is applied as a cooling system in an electronic product, the heat pipe may be a restriction on a structure of the electronic product.

In addition, since a vapor and a liquid flow in opposite directions in a straight cylindrical heat pipe, the vapor and the liquid mix in a middle portion of the pipe. Through the mixture, an amount of heat to be transferred is substantially reduced compared to a heat amount that can be transferred theoretically.

A looped heat pipe (LHP) system is suggested as an ideal heat transfer system to solve the problems due to the structure restriction and the mixing of a vapor and a liquid.

An LHP system is a type of capillary pumped loop heat pipe (CPL) developed by NASA of the US in order to dissipate large amounts of heat generated in communication devices or electronic devices for artificial satellites.

FIG. 2 is a schematic conceptual diagram of a conventional LHP system 110. The conventional LHP system 110 includes a condenser 112, an evaporator 114, and a vapor line 116 and a liquid line 118 that connect the condenser 112 and the evaporator 114 to one another to thereby form a loop.

FIG. 3 is a schematic conceptual diagram illustrating an operation of the LHP system 110 of FIG. 2.

The evaporator 114 includes a compensation chamber 112 that accommodates a working fluid that is to be liquefied before permeating into a sintered wick 120 included in the evaporator 114, to buffer the working fluid. In the LHP system 110, the sintered wick 120 is installed only in the evaporator 114, unlike the conventional straight heat pipe 100 (see FIG. 1).

The LHP system 110 having the above-described structure operates according to the following principle.

First, when a heating plate 124 of the evaporator 114 contacting a heat source such as a heat generating component is heated, a working fluid permeated into the sintered wick 120 is heated to a saturation temperature by heat transmitted from the heating plate 124, and is changed into a vapor.

The generated vapor is transferred to the condenser 112 along a vapor line 116 connected to a side of the evaporator 114. Next, as the vapor passes through the condenser 112 and dissipates heat to the outside, the vapor is condensed, and the condensed working fluid is moved to the evaporator 114 again along a liquid line 118 connected to the condenser 112, thereby repeating the above-described operation to cool the heat source 101.

As illustrated in FIG. 3, the sintered wick 120 is bonded to an inner circumferential surface of the evaporator 114, and a space formed by the inner circumferential surface of the sintered wick 120 forms a vapor passage through which the working fluid is changed into a vapor and moves to the vapor line 116.

Meanwhile, the working fluid in a liquid state is changed into a vapor on a surface of the sintered wick 120. Accordingly, this surface is referred to as an evaporation interface or a vapor-liquid interface.

The working fluid circulates while passing by points denoted by P1 through P7. The working fluid is evaporated at the point P1, and the evaporated working fluid moves to the point P2 through the vapor path inside the evaporator 114, and then moves to the point P3 along the vapor line 116. By passing from the points P3 and P4 at an inlet to the point P5 at an outlet of the condenser 112, the working fluid in a vapor state is condensed again. The working fluid in a liquid state passes by the point P6 at the inlet of the evaporator 114 along the liquid line 118 and passes a compensation chamber 122 and is absorbed by the sintered wick 120 at the point P7 to move to the point P1 again.

In the LHP system 110, a force that causes movement of the working fluid is a capillary pumping force of the sintered wick 120. The capillary pumping force is related to a diameter of pores formed in the sintered wick 120.

That is, if the diameter of pores formed in the sintered wick 120 is reduced, a capillary pumping force is increased. However, at the same time, as the size of pores is reduced, flow resistivity of the sintered wick 120 increases and thus permeability thereof decreases. Thus, it is difficult to obtain desired cooling performance just by adjusting a size of pores in the sintered wick 120.

Consequently, a sintered wick included in an evaporator used in an LHP system needs to be configured such that a capillary pumping force is increased but permeability is not decreased, so that a working fluid may be effectively circulated.

SUMMARY OF THE INVENTION

The present invention provides an evaporator for a looped heat pipe (LHP) system, in which a capillary pressure is increased but permeability is not decreased so as to facilitate circulation of a working fluid inside the LHP system, thereby improving cooling efficiency for relatively long distance transportation and under a relatively high heat flux condition.

The present invention also provides a method of manufacturing the evaporator for an LHP system.

According to an aspect of the present invention, there is provided an evaporator for a looped heat pipe (LHP) system, in which a working fluid circulates to cool a heat generating electronic component that generates heat during operation, the evaporator including: a body comprising an inlet through which the working fluid enters and an outlet through which the working fluid is discharged; a sintered wick that is included in the body, wherein the sintered wick is formed by sintering a copper powder, and a plurality of pores are formed in the sintered wick; and an additional layer that is formed on a surface of the sintered wick, wherein the additional layer is formed by sintering copper particles having a size smaller than that of the copper powder forming the sintered wick, and the working fluid moved from the sintered wick is changed in a vapor state to be discharged.

The thickness of the additional layer may be from 0.1 μm to 30 μm.

The thickness of the sintered wick may be from 1.0 mm to 2.0 mm.

By a hot pressing method in which heat and pressure are applied to the additional layer, the additional layer may be sintered and may be combined with the sintered wick at the same time.

The sintered wick may be formed by sintering an irregular shaped micro copper powder having a size of 40 μm to 150 μm, and the additional layer may be formed by sintering sphere-shaped nano copper particles each having a diameter of 10 nm to 200 nm.

According to another aspect of the present invention, there is provided a method of manufacturing an evaporator for a looped heat pipe (LHP) system, in which a working fluid circulates to cool a heat generating electronic component that generates heat during operation, the method including: forming a body comprising an inlet through which the working fluid enters and an outlet through which the working fluid is discharged; forming a sintered wick that is included in the body, wherein the sintered wick is formed by sintering a copper powder, and a plurality of pores are formed in the sintered wick; and forming an additional layer that is formed on a surface of the sintered wick, wherein the additional layer is formed by sintering copper particles having a size smaller than that of the copper powder forming the sintered wick, and the working fluid moved from the sintered wick is changed in a vapor state to be discharged, wherein the forming of the additional layer comprises: forming the additional layer by sintering the copper particles and combining the copper particles with the sintered wick at the same time by using a hot pressing method in which heat and pressure are applied to the copper particles, in a state in which the copper particles are placed on the surface of the sintered wick.

A pressure that is applied in the forming of the additional layer may be from 10 Pa to 100 Pa, and a temperature during the forming of the additional layer may be from 100° C. to 200° C.

A temperature during the forming of the additional layer may be from 145° C. to 155° C.

Time during which the pressure and the heat are applied in the forming of the additional layer may be from 5 minutes to 15 minutes.

The thickness of the additional layer may be from 0.1 μm to 30 μm, and the thickness of the sintered wick may be from 1.0 mm to 2.0 mm.

The copper powder forming the sintered wick may be an irregular shaped micro copper powder having a size of 40 μm to 150 μm, and the copper particles may be sphere-shaped nano copper particles each having a diameter of 10 nm to 200 nm.

The forming of the additional layer may be performed under air pressure.

The forming of the sintered wick may be performed for 3 to 7 hours, and the forming of the additional layer may be performed for 5 to 15 minutes.

The evaporator for an LHP system according to the embodiments of the present invention includes a thin additional layer consists of nano copper particles that is formed on a vaporization surface of a sintered wick formed of a micro-size copper powders by using a sintering bonding. Accordingly, the sintered wick coupled to the additional layer that enhances capillary pressure while having minimal impact on permeability.

In addition, a contact thermal resistance between the additional layer and the vaporization surface of the sintered wick can be suppressed. Thus, a pressure loss of the sintered wick coupled to the additional layer is decreased, and thus a working fluid inside the LHP system is circulated smoothly with advanced capillary pressure generated by the sintered wick coupled to the additional layer. Thus, cooling efficiency for relatively long distance transportation and under a relatively high heat flux condition can be improved.

In addition, according to the method of manufacturing an evaporator for an LHP system, the additional layer formed of nano copper particles can be easily formed on the vaporization surface of the sintered wick.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

FIG. 1 is a schematic view illustrating an operation of a conventional cylindrical heat pipe;

FIG. 2 is a conceptual diagram illustrating a conventional looped heat pipe (LHP) system;

FIG. 3 is a conceptual diagram for explaining an operation of the conventional LHP system of FIG. 2;

FIG. 4 is a conceptual diagram illustrating an LHP system in which an evaporator according to an embodiment of the present invention is included;

FIG. 5 is a partial perspective view of the evaporator of FIG. 4 according to an embodiment of the present invention;

FIG. 6 is a conceptual cross-sectional view in which a body, a sintered wick, and a portion of an additional layer, which is illustrated in FIG. 5, are magnified;

FIGS. 7 and 8 are photographic images of cross sections of the sintered wick and additional layer illustrated in FIG. 5, photographed using a scanning electronic microscope (SEM); and

FIGS. 9 through 11 are conceptual diagrams for explaining a method of manufacturing an evaporator for an LHP system according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an evaporator that is one of various elements of a looped heat pipe (LHP) system.

FIG. 4 is a conceptual diagram illustrating an LHP system 110 in which an evaporator according to an embodiment of the present invention is included.

Referring to FIG. 4, the LHP system 110 includes an evaporator 1 according to an embodiment of the present invention, a condenser 112, a vapor transport line 116, and a liquid transport line 118.

The condenser 112 changes a working fluid in a vapor state and transmitted from the evaporator 1 into a liquid. The condenser 112 takes heat from the working fluid to dissipate the heat to outer air.

Also, the vapor transport line 116 is a line member that connects the evaporator 1 and the condenser 112 so that the working fluid changed into a vapor state in the evaporator 1 may be transported to the condenser 112. The liquid transport line 118 is a line member that connects the condenser 112 and the evaporator 1 so that the working fluid changed into a liquid state in the condenser 112 may be supplied to the evaporator 1 again.

Meanwhile, the general description and operations as described in the related art of the invention apply to the condenser 112, the vapor transport line 116, and the liquid transport line 118.

Hereinafter, the evaporator 1 for an LHP system according to the current embodiment of the present invention will be described in detail with reference to FIGS. 4 through 8.

FIG. 4 is a conceptual diagram illustrating the LHP system 110 in which the evaporator 1 according to the current embodiment of the present invention is included. FIG. 5 is a partial perspective view of the evaporator 1 of FIG. 4. FIG. 6 is a conceptual cross-sectional view illustrating a body 10, a sintered wick 20, and an additional layer 30, which are included in the evaporator 1 of FIG. 5. FIGS. 7 and 8 are photographic images of the sintered wick 20 and additional layer 30 captured using a scanning electronic microscope (SEM).

The evaporator 1 for an LHP system according to the current embodiment of the present invention includes the body 10, the sintered wick 20, and the additional layer 30.

The body 10 is in contact with a heat generating electronic component (not shown) to receive heat generated during operation of the heat generating electronic component (see “heat” and arrows indicating the same shown in FIG. 4). The body 10 is formed of copper having a relatively high thermal conductivity.

In the current embodiment, the body 10 has a shape in which a hexahedron opened in one direction is formed in a body and a separately formed member is coupled to an open surface of the hexahedron. However, in other embodiments, the body 10 may be variously modified such that a lower surface thereof is formed of a separate member and is coupled to other members.

Meanwhile, the body 10 is formed to contact a heat generating component at a portion of an outer surface of the body 10. That is, the body 10 can receive heat when the heat generating component contacts a portion of an outer lower surface or lateral surface of the body 10.

Inside the body 10, a compensation chamber 16 and the sintered wick 20 including the additional layer 30 are formed. An inlet 12 and an outlet 14 are formed in the body 10. The inlet 12 and the outlet 14 are conceptually illustrated in FIG. 5. According to the current embodiment, the compensation chamber 16 is formed at the inlet 12 of the body 10.

A working fluid that circulates through the LHP system 110 flows into the body 10 in a liquid state through the inlet 12. The working fluid in a liquid state is contained in the compensation chamber 16 before moving to the sintered wick 20. Through the outlet 14, the working fluid in a vapor state is discharged out of the body 10. That is, the working fluid is changed into a vapor by passing through the sintered wick 20 and the additional layer 30, and is discharged out of the body 10 after passing a vapor removal space 18 surrounded by the additional layer 30. The discharged working fluid is moved to the condenser 112 via the vapor transport line 116.

The sintered wick 20 is contained in the body 10. The sintered wick 20 is formed by sintering a copper powder. The sintered wick 20 is a porous material in which a large number of pores are formed.

Meanwhile, according to the current embodiment of the present invention, the thickness of the sintered wick 20 is in the range of from 1.0 mm to 2.0 mm. The sintered wick 20 is formed by sintering an irregular shaped micro copper powder having a size of 40 μm to 150 μm.

The pores formed in the sintered wick 20 may be formed using a general method of forming a sintered wick using a copper powder, and such that a diameter of the pores is in a range from about 100 to about 200 μm.

As the working fluid in a liquid state flows into the sintered wick 20, the pores having a diameter in the above-described range suppress the flow resistivity of the working fluid and thus allow good permeability of the working fluid. However, the pore size may be adjusted according to the type of working fluid used in the LHP system 200, the length of a transport line, and a cooling range.

The specific shape of the sintered wick 20 may be modified variously as long as the working fluid flown through the inlet 12 satisfies a predetermined condition of being discharged from the outlet 14 after passing the sintered wick 20. That is, in the current embodiment, the sintered wick 20 is made in one body as a shape of a hexahedron opened in one direction. However, according to some embodiments, the sintered wick 20 may be made in a plate shape.

The additional layer 30 is included in the sintered wick 20 as if coated on the sintered wick 20. In the additional layer 30, the working fluid delivered from the sintered wick 20 is changed in a vapor state and is discharged to the outside of the additional layer 30.

The additional layer 30, like the sintered wick 20, is formed of a copper material. Since both the sintered wick 20 and the additional layer 30 are formed of the copper material, contact thermal resistance at an interface therebetween is lowered.

The additional layer 30 is formed by sintering copper particles having a size smaller than that of the copper powder forming the sintered wick 20.

In the current embodiment, the additional layer 30 is formed by sintering sphere-shaped nano copper particles each having a diameter of 10 nm to 200 nm. Since the additional layer 30 is formed by sintering the nano copper particles each having the diameter of 10 nm to 200 nm, a plurality of pores formed therein also have a nano size corresponding to the size of the nano copper particles.

In the current embodiment, the thickness of the additional layer 30 is in a range of from 0.1 μm to 30 μm. If the thickness of the additional layer 30 is less than the thickness in the range, it is difficult to actually form the additional layer 30. If the thickness of the additional layer 30 is greater than the thickness in the range, permeability of the working fluid deteriorates due to flow resistance of the working fluid and thus a pressure loss increases. Accordingly, total pressure drop of the LHP system 110 is lowered so that a heat transfer performance of the LHP system 110 may be higher.

If the shape of the sintered wick 20 is modified, a detailed shape of the additional layer 30 is also modified to correspond to the modification of the shape of the sintered wick 20.

In the current embodiment, by a hot pressing method in which copper particles are heaped on the sintered wick 20 and heat and pressure are applied thereto, the additional layer 30 is sintered and is combined with the sintered wick 20 at the same time to become one body with the sintered wick 20.

However, in another embodiment, after separately forming an additional layer, this additional layer may be combined with the sintered wick 20 by the hot pressing method. In this case, contact thermal resistance is higher compared to the current embodiment, and thus, a vapor temperature increases, thereby increasing an operating temperature of the LHP system 110. Thus, there is a disadvantage that a system thermal resistance increases, but effects other than the disadvantage may be obtained.

FIG. 7 is a photographic image of a cross section of the sintered wick 20 and additional layer 30, photographed using a scanning electronic microscope (SEM), and FIG. 8 is a photographic image in which a cross sectional portion of the additional layer 30 is magnified. Referring to the photographic images of FIGS. 7 and 8, micro pores are formed in the sintered wick 20, and nano pores are formed in the additional layer 30.

Hereinafter, function and effects of the evaporator 1 of the LHP system 200 having the above-described structure will be described in detail.

An operation of the LHP system 110 including the evaporator 1 according to the current embodiment of the present invention will be briefly described with reference to FIG. 4.

A surface of the body 10 of the evaporator 1 is contacted to a heat generating electronic component (not shown). Heat generated by the heat generating electronic component is transmitted to the sintered wick 20 included in the body 10, and the heat is transmitted to the additional layer 30 disposed on a surface of the sintered wick 20. The liquid phase of the working fluid is changed into a vapor phase by the transferred heat and then is discharged from the additional layer 30.

The working fluid changed into a vapor state is discharged to the outside of the evaporator 1 through the outlet 14. The discharged working fluid is moved to the condenser 112 to be changed into a liquid state as heat is taken away from the working fluid, and then the working fluid flows along the liquid transport line 118 and through the inlet 12 of the body 10 and into the compensation chamber 16 of the body 10.

The working fluid in a liquid state flown into the compensation chamber 16 permeates between the pores of the sintered wick 20 due to a capillary pumping force due to the pores of the sintered wick 20. The working fluid in a liquid state and permeated between the pores of the sintered wick 20 permeates between the pores of the additional layer 30 by a capillary pumping force of the additional layer 30 again. The working fluid permeated between the pores is heated by sensible heat, which is transferred from the heat generating electronic component, and thus is changed into a vapor state, and moves to the space 18 after being changed to latent heat. The working fluid circulates in this way, thereby cooling the heat generating electronic component.

Here, a capillary pumping force, which is generally referred to as “capillary pressure”, is given by the following equation.

$P=\frac{2\sigma }{r}$

P denotes a capillary pressure, σ denotes a surface tension of the working fluid, and r denotes an effective radius of the pores of the sintered wick 20 sintered by metal particles such as copper and aluminum. Since the surface tension of the working fluid is constant, a capillary pumping force is inversely proportional to the effective radius of the pores of the sintered wick 20 sintered by metal particles such as copper, and nickel. That is, the smaller the effective radius of the pores, the greater the capillary pumping force.

Meanwhile, permeability of the working fluid is proportional to the effective radius of the pores. That is, the smaller the effective radius of the pores, the smaller the permeability.

Like general sintered wicks, the sintered wick 20 according to the current embodiment of the present invention also has micro-scale pores, and the additional layer 30 including a plurality of nano-scale pores is formed on the surface of the sintered wick 20 so as to improve a capillary pumping force while to have the minimal impact of permeability of the working fluid. Consequently, the working fluid may be easily circulated, thereby improving cooling performance.

That is, the working fluid in a liquid state may have no difficulty in passing through the sintered wick 20 in which micro-scale pores are formed. In addition, due to the nano-scale pores formed in the additional layer 30, a capillary pumping force is more strengthened, thereby facilitating circulation of the working fluid.

In other words, the evaporator 1 for an LHP system according to the current embodiment of the present invention includes the additional layer 30 including nano-scale pores, which is formed on the surface of the sintered wick 20, and thus, a capillary pumping force is improved and permeability of the working fluid through the sintered wick 20 is not lowered.

That is, by disposing the additional layer 20 formed by sintering of nano-scale copper particles on the sintered wick 20 formed by sintering of micro-scale copper powder, influence on the permeability of the working fluid is minimized and a high capillary pumping force is provided, and thus, cooling performance may be strengthened. In addition, this configuration may maintain the same feat flux and may compensate for a geometrical limitation.

Hereinafter, a method of manufacturing an evaporator for an LHP system according to an embodiment of the present invention will be described.

According to the method of manufacturing an evaporator for an LHP system according to the current embodiment of the present invention, an evaporator that is an element of an LHP system, in which a working fluid circulates to cool a heat generating component heated during operation, is manufactured.

The method of manufacturing an evaporator for an LHP system according to the current embodiment of the present invention will be described with reference to FIGS. 9 through 11 below. FIG. 9 is a diagram form for explaining a process of forming a sintered wick (step 1), and FIG. 10 is a diagram form for explaining a process of forming an additional layer (step 2), and FIG. 11 is a time-temperature graph concerning the process of forming a sintered wick and the process of forming an additional layer.

An evaporator 1 manufactured by the method of manufacturing an evaporator according to the current embodiment of the present invention includes a body 10, a sintered wick 20, and an additional layer 30. Elements of the evaporator 1 are identical or similar to those of the evaporator 1 described above, and thus description thereof will not be repeated, and previous description or appropriate modification of the description will apply.

One of major features of the method of manufacturing an evaporator according to the current embodiment of the present invention is related to how the additional layer 30 is disposed on the sintered wick 20. Hereinafter, configurations related to the additional layer 30 will be mainly described.

Although the sintered wick 20 included in the evaporator 1 described above has a shape of a hexahedron having an opened one side and includes the additional layer 30 formed at the sintered wick 20, in the following description of the method of manufacturing an evaporator, a case in which a sintered wick having a plate form is formed and an additional layer is further disposed on the upper side of the sintered wick is explained as an example to conceptually explain the method.

The shape of the hexahedron having an opened one side may be manufactured by a mold having a shape corresponding to the hexahedral shape. For example, a sintered wick, which has a shape of a hexahedron having an opened one side, and an additional layer, which is disposed on the surface of the sintered wick, may be formed by an external mold having an opened one side and an internal mold that is disposed inside the external mold and is located spaced apart from the external mold by a predetermined interval.

The additional layer 30 disposed on the sintered wick 20 is manufactured by a process including a process of forming a sintered wick and a process of forming an additional layer.

The process of forming a sintered wick is a process of forming a sintered wick by heating copper powder. Referring to FIG. 9, copper powder 20′ is put in a usual isothermal furnace and then is sintered by heating the copper powder.

The copper powder 20′ is micro copper powder having an irregular shape and a size of 40 μm to 150 μm. The reference numeral 20′ denotes copper powder before the sintered wick 20 is formed.

The sintered wick 20 is manufactured so that the thickness thereof is in range of 1.0 mm to 2.0 mm. In this case, to obtain a sintered wick having a desired thickness, the amount of necessary copper powder is adjusted by calculating a necessary weight in consideration of the thickness and length of the sintered wick to be manufactured and the density of the copper.

In the process of forming a sintered wick, a preferable heating temperature may be in a range of 500° C. to 700° C., and the most preferable heating temperature is about 600° C. Referring to FIG. 11, the extent of heating and the extent of cooling are shown in the process of forming a sintered wick (step 1). The process of forming a sintered wick is performed for 3 to 7 hours.

Referring to FIG. 9, the inside of the isothermal furnace maintains a vacuum state, thereby suppressing oxidation of the copper powder. In addition, the isothermal furnace includes a heating apparatus and a cooling apparatus, and thus may adjust a temperature of the inside of the isothermal furnace.

Next, the process of forming an additional layer (step 2) is performed. The process of forming an additional layer (step 2) is a process of forming an additional layer on the sintered wick 20 formed through the preceding process.

In the process of forming an additional layer (step 2), copper particles smaller than the copper powder used when forming the sintered wick 20 are used to manufacture an additional layer. Referring to FIG. 10, pressure and heat are applied in a state in which copper particles 30′ are placed on the surface of the sintered wick 20. That is, by using the hot pressing method, the copper particles 30′ are sintered and are combined with the surface of the sintered wick 20 at the same time.

In the current embodiment, a pressure that is applied in the process of forming the additional layer is from 10 Pa to 100 Pa, and a temperature that is applied in the process of forming the additional layer is from 100° C. to 200° C. The most suitable heating temperature is about 150° C. In addition, time during which the pressure and the temperature are applied is from 5 minutes to 15 minutes. The pressure, the temperature, and the time are appropriately determined in consideration of the thickness of the additional layer to be manufactured, the size of the copper particles 30′, and the size of pores.

In the current embodiment, the thickness of the additional layer is from 0.1 μm to 30 μm. Referring to FIG. 10, the copper particles 30′ that are placed on the surface of the sintered wick 20 are sphere-shaped nano copper particles having a diameter of 10 nm to 200 nm. The reference numeral 30′ denotes the copper particles that become the additional layer after sintering.

Referring to FIG. 10, a vacuum pump, a unit for applying pressure, a heating unit, and a cooling unit are provided to perform the process of forming an additional layer (step 2).

Although in the current embodiment, the process of forming an additional layer is performed in a vacuum state, the present invention is not limited thereto. That is, in another embodiment, the process of forming an additional layer may be performed in an air pressure state.

Consequently, a sintered wick including an additional layer may be manufactured via the process of forming a sintered wick (step 1) and the process of forming an additional layer (step 2), and an evaporator including the sintered wick including the additional layer may be manufactured. By using the evaporator in an LHP system, a capillary pumping force of sintered wick 20 may be increased but permeability of sintered wick 20 may not decrease, thereby improving cooling performance.

According to the method of manufacturing an evaporator for an LHP system, the additional layer having nano pores may be formed on the sintered wick having micro pores. In addition, at the same time as sintering the additional layer, the additional layer may be combined with the sintered wick 20. The evaporator manufactured according to the method may obtain the above stated advantages.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

Claims

1. An evaporator for a looped heat pipe (LHP) system, in which a working fluid circulates to cool a heat generating electronic component that generates heat during operation, the evaporator comprising:

a body comprising an inlet through which the working fluid enters and an outlet through which the working fluid is discharged;

a sintered wick that is included in the body, wherein the sintered wick is formed by sintering a copper powder, and a plurality of pores are formed in the sintered wick; and

an additional layer that is formed on a surface of the sintered wick, wherein the additional layer is formed by sintering copper particles having a size smaller than that of the copper powder forming the sintered wick, and the working fluid moved from the sintered wick is changed in a vapor state to be discharged.

2. The evaporator for an LHP system of claim 1, wherein the thickness of the additional layer is from 0.1 μm to 30 μm.

3. The evaporator for an LHP system of claim 1, wherein the thickness of the sintered wick is from 1.0 mm to 2.0 mm.

4. The evaporator for an LHP system of claim 1, wherein by a hot pressing method in which heat and pressure are applied to the additional layer, the additional layer is sintered and is combined with the sintered wick at the same time.

5. The evaporator for an LHP system of claim 1, wherein the sintered wick is formed by sintering an irregular shaped micro copper powder having a size of 40 μm to 150 μm and the additional layer is formed by sintering sphere-shaped nano copper particles each having a diameter of 10 nm to 200 nm.

6. A method of manufacturing an evaporator for a looped heat pipe (LHP) system, in which a working fluid circulates to cool a heat generating electronic component that generates heat during operation, the method comprising:

forming a body comprising an inlet through which the working fluid enters and an outlet through which the working fluid is discharged;

forming a sintered wick that is included in the body, wherein the sintered wick is formed by sintering a copper powder, and a plurality of pores are formed in the sintered wick; and

forming an additional layer that is formed on a surface of the sintered wick, wherein the additional layer is formed by sintering copper particles having a size smaller than that of the copper powder forming the sintered wick, and the working fluid moved from the sintered wick is changed in a vapor state to be discharged,

wherein the forming of the additional layer comprises: forming the additional layer by sintering the copper particles and combining the copper particles with the sintered wick at the same time by using a hot pressing method in which heat and pressure are applied to the copper particles, in a state in which the copper particles are placed on the surface of the sintered wick.

7. The method of claim 6, wherein a pressure that is applied in the forming of the additional layer is from 10 Pa to 100 Pa, and a temperature during the forming of the additional layer is from 100° C. to 200° C.

8. The method of claim 6, wherein a temperature during the forming of the additional layer is from 145° C. to 155° C.

9. The method of claim 6, wherein time during which the pressure and the heat are applied in the forming of the additional layer is from 5 minutes to 15 minutes.

10. The method of claim 6, wherein the thickness of the additional layer is from 0.1 μm to 30 μm, and the thickness of the sintered wick is from 1.0 mm to 2.0 mm.

11. The method of claim 6, wherein the copper powder forming the sintered wick is an irregular shaped micro copper powder having a size of 40 μm to 150 μm, and the copper particles are sphere-shaped nano copper particles each having a diameter of 10 nm to 200 nm.

12. The method of claim 6, wherein the forming of the additional layer is performed under air pressure.

13. The method of claim 6, wherein the forming of the sintered wick is performed for 3 to 7 hours, and the forming of the additional layer is performed for 5 to 15 minutes.