Capillary wick having composite lattice structure for heat pipe, heat pipe including same, and manufacturing method therefor

Abstract

A heat pipe including a capillary wick of a composite lattice structure, according to the present invention, includes a capillary wick inserted axially into the inside of a pipe main body, wherein the capillary wick has a structure in which a plurality of lattice layers having lattice structures with different pore sizes are stacked radially, thereby securing capillary force from the outer side to the inner side of the inside of the heat pipe and also increasing transportation capacity of liquid by increasing permeability of liquid at the outer side of the inside of the heat pipe and thus improving the heat conduction rate of the heat pipe. In addition, since the capillary wick according to the present invention is manufactured using 3D printing technology, the capillary wick in which a lattice structure having a complex shape is stacked in a plurality of layers may be more easily manufactured. In addition, according to the present invention, since a wick structure does not need to be additionally processed on the inner wall of the pipe body, the heat pipe may be easily configured and manufactured, and may be applied to existing pipe bodies.

Description

Capillary wick having a composite lattice structure for a heat pipe, a heat pipe including the same, and a method for manufacturing the same

[0001] The present invention relates to a capillary wick having a composite lattice structure for a heat pipe, a heat pipe including the same, and a method for manufacturing the same, and more particularly, to a capillary wick having a composite lattice structure for a heat pipe, a heat pipe including the same, and a method for manufacturing the same, wherein a capillary wick inserted into the interior of a pipe body is formed by laminating a plurality of lattice layers having different lattice structures and pore sizes, thereby securing both the capillary force of the capillary wick and the permeability of a liquid, thereby maximizing the heat transfer rate of the heat pipe.

[0002] In general, a heat pipe is a device in which a working fluid is contained and sealed within the pipe, and vapor that is evaporated by receiving external heat at one end of the pipe, which is a heating end, moves axially inside the pipe to the other end of the pipe, condenses at the other end of the pipe, and releases heat, and the condensate condensed at the cooling end is transported by capillary force through a wick on the inner surface of the pipe and circulates to the heating end.

[0003] However, conventional heat pipes require the formation of groove-shaped wicks on their inner surfaces, making them difficult to manufacture and maintain. Furthermore, while reducing the cross-sectional area of ​​the grooves improves capillary force, it also reduces permeability, lowering heat transfer capacity. Furthermore, increasing the cross-sectional area of ​​the grooves also reduces capillary force.

[0004] The purpose of the present invention is to provide a capillary wick having a composite lattice structure for a heat pipe capable of securing both capillary force and heat of transmission of a liquid, a heat pipe including the same, and a method for manufacturing the same.

[0005] A heat pipe including a capillary wick having a composite lattice structure according to the present invention comprises: a pipe body for accommodating a working fluid; a capillary wick formed by axially inserting a plurality of lattice layers having different lattice structures into the interior of the pipe body and radially stacking them, wherein among the plurality of lattice layers, a lattice layer located on the outer circumference side has a larger pore size than a lattice layer located on the inner circumference side.

[0006] The above capillary wick is formed by 3D printing of the plurality of grid layers.

[0007] The above plurality of grid layers include an inner grid layer formed with a first grid structure having a first pore size and arranged on the inner circumference of the capillary wick, and an outer grid layer formed with a second grid structure having a second pore size larger than the first pore size and a smaller area-to-volume ratio than the first grid structure, which is laminated on the outer circumference of the inner grid layer.

[0008] The above first lattice structure includes a diamond lattice structure.

[0009] The above second lattice structure includes a cubic lattice structure.

[0010] The above inner grid layer is formed by stacking the first grid structure in a radial direction in multiple layers.

[0011] The above outer grid layer is formed by stacking the second grid structure in multiple layers in the radial direction.

[0012] The above pipe body is formed with a flat inner surface.

[0013] According to another aspect of the present invention, a heat pipe including a capillary wick having a composite lattice structure comprises: a pipe body for accommodating a working fluid; a hollow capillary wick formed by radially stacking a plurality of lattice layers having different lattice structures and pore sizes, which are axially inserted into the interior of the pipe body; wherein the capillary wick is formed by 3D printing, and the plurality of lattice layers include: an inner lattice layer formed by stacking a plurality of layers of diamond lattice structures having a first pore size, which are arranged on the inner periphery of the capillary wick; and an outer lattice layer formed by stacking a plurality of layers of cubic lattice structures having a second pore size larger than the first pore size, which are stacked on the outer periphery of the inner lattice layer so as to have a higher transmittance than the inner lattice layer.

[0014] The above pipe body is formed with a flat inner surface.

[0015] According to another aspect of the present invention, a capillary wick having a composite lattice structure for a heat pipe is formed in a hollow shape so as to be axially insertable into a pipe body, and a plurality of lattice layers having different lattice structures are laminated in a radial direction, and among the plurality of lattice layers, a lattice layer located on the outer circumference side is formed to have a larger pore size than a lattice layer located on the inner circumference side.

[0016] A method for manufacturing a heat pipe including a capillary wick having a composite lattice structure according to the present invention comprises the steps of: 3D printing an inner lattice layer having a pipe shape having a first lattice structure having a first pore size set in advance using a 3D printer; 3D printing an outer lattice layer having a second pore size set larger than the first pore size on an outer surface of the inner lattice layer to form a capillary wick in which the first lattice structure and the second lattice structure are integrally formed; and axially inserting the capillary wick into the interior of a pipe body.

[0017] The above first lattice structure may include a diamond lattice structure.

[0018] The above second lattice structure may include a cubic lattice structure.

[0019] The above pipe body may include an inner surface that is flat.

[0020] A heat pipe including a capillary wick having a composite lattice structure according to the present invention is formed such that a capillary wick inserted axially into the interior of a pipe body has a structure in which a plurality of lattice layers having lattice structures with different pore sizes are laminated radially, thereby not only securing a capillary force in an inward direction from the inside and outside of the heat pipe, but also increasing the transport capacity of the liquid by improving the permeability of the liquid at the inside and outside of the heat pipe, thereby improving the performance of the heat pipe.

[0021] In addition, the capillary wick according to the present invention is manufactured using 3D printing technology, so that it has the advantage of being able to more easily manufacture a capillary wick in which a complex-shaped lattice structure is laminated in multiple layers.

[0022] In addition, according to the present invention, since there is no need to additionally process a wick structure on the inner wall of the pipe body, there is an advantage in that the configuration and manufacturing of the heat pipe are easy and can be applied to existing pipe bodies.

[0023] FIG. 1 is a perspective view showing a portion of a heat pipe including a capillary wick of a composite lattice structure according to an embodiment of the present invention.

[0024] FIG. 2 is a cross-sectional view of a heat pipe including a capillary wick of a composite lattice structure according to an embodiment of the present invention.

[0025] FIG. 3 is a photograph showing the outer surface of the outer grid layer of a capillary wick according to an embodiment of the present invention.

[0026] FIG. 4 is a photograph showing the outer surface of the inner grid layer of a capillary wick according to an embodiment of the present invention.

[0027] FIG. 5 is a cross-section of a capillary wick cut in the axial and transverse directions according to an embodiment of the present invention, and an SEM photograph thereof.

[0028] FIG. 6 is a drawing schematically showing the unit structure of the cubic lattice structure of the outer lattice layer according to an embodiment of the present invention.

[0029] FIG. 7 is a schematic diagram showing the unit structure of the diamond lattice structure of the outer lattice layer according to an embodiment of the present invention.

[0030] FIG. 8 is a graph comparing the fluid mass flow rate of a heat pipe including a capillary wick of a composite lattice structure according to an embodiment of the present invention with that of a conventional case.

[0031] FIG. 9 is a graph comparing the capillary pumping force of a heat pipe including a capillary wick of a composite lattice structure according to an embodiment of the present invention with that of a conventional case.

[0032] Fig. 10 is an SEM photograph showing the surface roughness of a capillary wick of a composite lattice structure according to an embodiment of the present invention.

[0033] Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.

[0034] FIG. 1 is a perspective view illustrating a portion of a heat pipe including a capillary wick of a composite lattice structure according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a heat pipe including a capillary wick of a composite lattice structure according to an embodiment of the present invention.

[0035] Referring to FIGS. 1 and 2, a heat pipe (1) including a capillary wick of a composite lattice structure according to an embodiment of the present invention includes a pipe body (10) and a capillary wick (20).

[0036] The above pipe body (10) is a hollow pipe formed to accommodate a working fluid. The pipe body (10) has a circular cross-section and a smooth and flat inner surface.

[0037] The capillary wick (20) is inserted axially into the interior of the pipe body (10). The capillary wick (20) is described as being inserted axially and detachably into the interior of the previously manufactured pipe body (10) as an example. The outer circumference of the capillary wick (20) is inserted so as to be in close contact with the inner circumference of the pipe body (10).

[0038] The capillary wick (20) is manufactured separately from the pipe body (10) and is formed into a hollow pipe shape by 3D printing using a 3D printer. The capillary wick (20) is formed as a hybrid lattice structure in which a plurality of lattice layers having different pore sizes and lattice structures are laminated in the radial direction. The pore sizes of the plurality of lattice layers become larger as they go in the radial direction.

[0039] Referring to FIGS. 2 to 5, in the present embodiment, the plurality of grid layers are described as including two inner grid layers (21) and an outer grid layer (22), for example. However, the present invention is not limited thereto, and the number of grid layers can be varied to two or more and applied. In addition, it is also possible for the grid layers to be formed with the same grid structure but with different pore sizes.

[0040] The inner grid layer (21) is formed as a first grid structure having a preset first pore size and is placed on the inner circumference of the capillary wick (20).

[0041] Referring to FIGS. 4 and 7, the first lattice structure is described as a diamond lattice structure, for example. Generally, there are various types of lattice structures, but the present invention uses a diamond lattice structure, which has a relatively high surface area to volume ratio. The surface area to volume ratio of the diamond lattice structure is approximately 5 mm. -1 However, it is not limited thereto, and the first grid structure can be changed and applied if it has a structure that can improve capillary force by having a smaller pore size than the grid structure of the outer grid layer (22).

[0042] Figure 7 shows the unit structure of the diamond lattice structure.

[0043] The outer grid layer (22) is laminated on the outer circumference of the inner grid layer (21) to form the outer surface of the capillary wick (20). The outer grid layer (22) has a second pore size larger than the first pore size and is formed as a second grid structure having a smaller area-to-volume ratio than the first grid structure. The outer circumference of the outer grid layer (22) is in close contact with the inner wall of the pipe body (10).

[0044] Referring to FIGS. 3 and 6, the second grid structure is described as an example of a cubic grid structure. However, the present invention is not limited thereto, and the first grid structure can be modified and applied to any structure that can improve transmittance by having a larger pore size than the grid structure of the inner grid layer (21).

[0045] Figure 6 shows a unit structure included in a cubic lattice structure.

[0046] The inner grid layer (21) above acts as a capillary channel that generates capillary force of the working fluid, and is therefore formed with a denser grid structure than the outer grid layer (22). The inner grid layer (21) above is a layer for improving capillary force.

[0047] The above outer grid layer (22) serves as a transport path when transporting the working fluid in the axial direction, and is therefore formed with a coarser grid structure than the inner grid layer (21). That is, the capillary wick (20) is a composite layer structure in which the inner grid layer (21) for improving capillary force and the outer grid layer (22) for improving permeability when transporting the working fluid are laminated.

[0048] In addition, referring to FIG. 2, in the present embodiment, the inner grid layer (21) is described as having three layers of diamond grid structures laminated in the radial direction, and the outer grid layer (22) is described as having two layers of cubic grid structures laminated in the radial direction. However, the present invention is not limited thereto, and the number of layers, radial thickness, and pore size of the inner grid layer (21) can be applied by changing them in various ways depending on the capillary force.

[0049] In addition, the number of layers, radial thickness, and pore size of the outer grid layer (22) can be varied and applied according to the transmittance.

[0050] A method for manufacturing a heat pipe including a capillary wick of a composite lattice structure according to an embodiment of the present invention configured as described above is described as follows.

[0051] First, the inner grid layer (21) is 3D printed using a 3D printer. The 3D printer can use nTopology, a commercial grid generation software, but is not limited thereto, and various 3D grid generation software can be applied.

[0052] The above inner grid layer (21) is formed in a hollow pipe shape having a first grid structure with a preset first pore size.

[0053] Next, using the 3D printer, the outer grid layer (22) is laminated on the outer surface of the inner grid layer (21). The outer grid layer (22) is formed to have a second grid structure with a second pore size set larger than the first pore size. Accordingly, the capillary wick (20) can be formed integrally by laminating the outer grid layer (22) on the outside of the inner grid layer (21).

[0054] When the capillary wick (20) is axially inserted into the inside of the pipe body (10), the manufacturing of the heat pipe is completed.

[0055] As described above, in the present invention, there is no need for additional processing such as a separate groove or surface treatment on the pipe body (10), so it can be used on an existing pipe body (10) and can be applied to a wider variety of pipe bodies.

[0056] Since the above capillary wick (20) is manufactured by 3D printing, it is easy to implement various pore sizes and complex lattice structures, and it is also easy to laminate the outer lattice layer (22) on the inner lattice layer (21).

[0057] The operation of a heat pipe including a capillary wick having a composite lattice structure as described above is described as follows.

[0058] When the liquid condensed at one end of the heat pipe (1), i.e., the cooling end, is transported back to the evaporation end, it passes through the cubic lattice structure of the outer lattice layer (22) arranged on the outer circumference inside the heat pipe (1).

[0059] Since the cubic lattice structure of the above outer lattice layer (22) has a sufficiently large pore size, the axial flow resistance is reduced during transport of the liquid, thereby reducing the pressure drop of the liquid, and thus the permeability of the liquid can be improved.

[0060] In addition, when heat is transferred from an external heat source to the internal working fluid at the other end of the heat pipe (1), i.e., the heating end, the heat first passes through the cubic lattice structure of the outer lattice layer (22) arranged on the outer circumference side inside the heat pipe (1).

[0061] Since the cubic lattice structure of the above outer lattice layer (22) provides sufficient space for accommodating liquid, the phenomenon of the working fluid drying out under high heat load conditions is prevented, and the operation of the heat pipe can also be prevented from stopping.

[0062] The inner grid layer (21) disposed at the interface between the liquid and the gas in the heat pipe (1) is formed with the diamond grid structure, thereby ensuring high capillary force.

[0063] In general, capillary force is inversely proportional to the pore size of the capillary wick (20), i.e., the capillary radius. In the present invention, the inner lattice layer (21) disposed at the interface between the liquid and the gas is formed in a diamond lattice structure, and thus, the pore size is much smaller than that of other structures such as the cubic lattice structure, thereby ensuring a higher capillary force.

[0064] Accordingly, the inner circumference of the capillary wick (20) forms a diamond lattice structure with smaller pores to further enhance the capillary force, and the outer circumference of the capillary wick (20) forms a cubic structure with larger pores to further enhance the permeability. That is, the capillary wick (20) according to the present invention forms a double layer by stacking lattice structures with at least two different pore sizes in the radial direction, thereby enhancing the capillary force during heat transfer while lowering the pressure drop during liquid transport, thereby increasing the transport capacity of the liquid.

[0065] In addition, since the pipe body (10) of the present invention does not require a wick structure or separate processing, it can be easily applied to existing pipe bodies.

[0066] Additionally, because it utilizes 3D printing technology, no additional processing or welding processes are required, and complex lattice structures can be manufactured more easily by stacking multiple layers.

[0067] The heat transfer enhancement effect of a heat pipe equipped with a capillary wick having two or more lattice structures with different pore sizes according to the present invention is described as follows.

[0068] Referring to mathematical equation 1, it can be seen that the heat transfer rate (q) of a heat pipe generally varies depending on the mass flow rate.

[0069]

[0070] Here, λ represents latent heat.

[0071] Referring to mathematical expression 2, it can be seen that the mass flow rate of the working fluid is determined by the ratio of the permeability (K) and the capillary radius (r), which are terms determined by the wick structure.

[0072]

[0073] Here, ρ is the density of the working fluid, σ is the surface tension of the working fluid, μ is the viscosity of the working fluid, A wick is the area of ​​the wick, L eff where is the effective length of the heat pipe, K is the permeability, and r is the capillary radius of the wick.

[0074] Therefore, it can be seen that the heat transfer rate (q) of the heat pipe varies depending on the mass flow rate, and the mass flow rate varies depending on the permeability (K) and the capillary radius (r).

[0075] Referring to Fig. 8, a capillary phenomenon was tested in a case where a conventional wick structure was provided with a screen mesh and in a case where a 3D printed composite lattice wick was provided by combining lattice structures with different pore sizes using the 3D printing technology according to the present invention.

[0076] Test results show that the liquid permeability (K) of the 3D printed composite lattice wick is approximately 132.0[10 -10 m 2 ] and, in the case of the conventional wick structure, the transmittance of the first screen mesh (#100 screen mesh) is about 2.40 [10 -10 m 2 ] and the transmittance of the second screen mesh (#400 screen mesh) is approximately 0.789[10 -10 m 2 ] was shown. That is, it can be seen that the liquid permeability (K) of the 3D printed composite lattice wick is higher than that of conventional wick structures.

[0077] Additionally, for the 3D printed composite lattice wick, the mass flow rate is approximately 108.0[10 -4 kg / s], and in the case of the conventional wick structure, the mass flow rate of the first screen mesh (#100 screen mesh) is approximately 1.56 [10 -4kg / s], and the mass flow rate of the second screen mesh (#400 screen mesh) is 0.16[10 -4 kg / s]. That is, it can be seen that the mass flow rate of the 3D printed composite lattice wick is higher than that of conventional wick structures.

[0078] Accordingly, it can be seen that the transmittance (K) of the 3D printing composite grid wick according to the present invention is greater than that of the conventional case, and accordingly, the mass flow rate of the 3D printing composite grid wick is also greater than that of the conventional case.

[0079] Since the mass flow rate of the 3D printed composite lattice wick according to the present invention is greater than that of a conventional wick, the heat transfer rate (q) of the 3D printed composite lattice wick according to the present invention is also greater. Therefore, the heat transfer rate of the heat pipe according to the present invention can be improved.

[0080] FIG. 9 is a graph comparing the capillary pumping force of a heat pipe including a capillary wick of a composite lattice structure according to an embodiment of the present invention with that of a conventional case. Referring to FIG. 9, it can be seen that the capillary pumping force of the 3D-printed composite lattice wick is greater than that of conventional wick structures.

[0081] Meanwhile, Fig. 10 is an SEM photograph showing the surface roughness of a capillary wick having a composite lattice structure according to an embodiment of the present invention. Referring to Fig. 10, when a capillary wick is manufactured using stainless steel powder through 3D printing, the surface roughness of the residual powder occurs as observed in the SEM photograph, thereby improving the wettability of the surface, thereby enhancing the capillary force of the capillary wick.

[0082] While the present invention has been described with reference to the embodiments illustrated in the drawings, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the appended claims.

[0083] The present invention enables the manufacture of a heat pipe with improved performance.

Claims

1. A pipe body that accommodates the working fluid; A plurality of grid layers having different grid structures are formed by being axially inserted into the inside of the pipe body and radially stacked, and among the plurality of grid layers, a grid layer located on the outer circumference side includes a capillary wick having a larger pore size than a grid layer located on the inner circumference side. A heat pipe comprising a capillary wick of composite lattice structure.

2. In claim 1, The above capillary wick is, The above multiple lattice layers are formed by 3D printing, A heat pipe comprising a capillary wick of composite lattice structure.

3. In claim 1, The above multiple grid layers are, An inner grid layer formed with a first grid structure having a first pore size and arranged on the inner side of the capillary wick, An outer grid layer is formed by laminating the outer surface of the inner grid layer and having a second grid structure having a second pore size larger than the first pore size and a smaller area-to-volume ratio than the first grid structure. A heat pipe comprising a capillary wick of composite lattice structure.

4. In claim 3, The above first lattice structure includes a diamond lattice structure. A heat pipe comprising a capillary wick of composite lattice structure.

5. In claim 3, The above second lattice structure includes a cubic lattice structure. A heat pipe including a capillary wick of lattice structure.

6. In claim 3, The above inner grid layer is, The above first grid structure is formed by stacking multiple layers in the radial direction. A heat pipe comprising a capillary wick of composite lattice structure.

7. In claim 3, The above outer grid layer is, The above second grid structure is formed by stacking multiple layers in the radial direction. A heat pipe comprising a capillary wick of composite lattice structure.

8. In claim 1, The above pipe body has a flat inner surface, A heat pipe comprising a capillary wick of composite lattice structure.

9. A pipe body that accommodates the working fluid; It includes a hollow capillary wick that is inserted axially into the inside of the pipe body and formed by radially stacking a plurality of grid layers with different grid structures and pore sizes, The above capillary wick is formed by 3D printing, The above multiple grid layers are, An inner grid layer formed by stacking multiple layers of diamond grid structures having a first pore size and arranged on the inner side of the capillary wick, An outer grid layer is formed by stacking multiple layers of cubic grid structures having a second pore size larger than the first pore size, and is laminated on the outer surface of the inner grid layer so that the transmittance is higher than that of the inner grid layer. A heat pipe comprising a capillary wick of composite lattice structure.

10. In claim 9, The above pipe body has a flat inner surface, A heat pipe comprising a capillary wick of composite lattice structure.

11. A hollow pipe body is formed so that it can be inserted axially into the pipe body, and multiple grid layers having different grid structures are laminated in the radial direction, and among the multiple grid layers, the grid layer located on the outer circumference side has a larger pore size than the grid layer located on the inner circumference side. Capillary wick with composite lattice structure for heat pipes.

12. A step of 3D printing a pipe-shaped inner grid layer having a first grid structure with a preset first pore size using a 3D printer; A step of 3D printing an outer grid layer having a second pore size set larger than the first pore size on the outer surface of the inner grid layer to form a capillary wick in which the first grid structure and the second grid structure are integrally formed; Comprising the step of axially inserting the capillary wick into the interior of the pipe body, A method for manufacturing a heat pipe including a capillary wick having a composite lattice structure.

13. In claim 12, The above first lattice structure includes a diamond lattice structure. A method for manufacturing a heat pipe including a capillary wick having a composite lattice structure.

14. In claim 12, The above second lattice structure includes a cubic lattice structure. A method for manufacturing a heat pipe including a capillary wick having a composite lattice structure.

15. In claim 12, The above pipe body has a flat inner surface, A method for manufacturing a heat pipe including a capillary wick having a composite lattice structure.

Images