KR101553547B1 - A flat plate pulsating heat pipe applicable at several work setting angles and the manufacturing method thereof - Google Patents

Abstract

The present invention relates to a flat plate pulsating heat pipe (Flat plate PHP), which can be applied at various angles and provide a heat transfer system of high efficiency without using electricity in a compact size electronic device such as a mobile phone or a note book computer. The present invention provides a flat plate PHP which evaluates the thermal performance in cases comprising a single turn loop and a multi-turn loop and in cases comprising a single diameter channel and dual-diameter channels, and has optimum performance regardless of the installation angle of the pulsating heat pipe. The flat plate PHP applicable at various installation angles of the present invention to achieve the above objective includes: a long rectangular silicon wafer bottom plate; a capillary tube including a channel which is formed in a straight line along the length direction of the silicon wafer bottom plate as having a fixed depth from an upper plane of the silicon wafer bottom plate and forms a closed loop connected from both ends of the silicon wafer bottom plate; a wafer upper plate which shields the capillary tube by being combined onto the silicon wafer bottom plate; and a working fluid which is filled in the capillary tube. The capillary tube is formed with an assembly of dual diameter channels including a pair of channels with different widths and a single diameter channel including a pair of channels with equal widths.

Description

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a flat plate vibrating heat pipe applicable to various angles and a manufacturing method thereof,

The present invention relates to a flat vibrating type heat pipe capable of controlling a temperature in an ultra-thin mobile device maximizing portability such as a smart phone and a tablet PC without requiring external power, and being applicable at various angles regardless of installation angle.

Electronic devices have been miniaturized and lightweight due to the improved performance of microprocessors. In recent years, the demand for ultra-thin mobile devices maximizing portability such as smart phones and tablet PCs is increasing rapidly. Since most of these electronic devices are of a laminated structure, a space for the cooling system is structurally very limited and narrow, and a need for an effective cooling method is emerging.

As a miniature cooling system, a typical thermal control device that does not require external power is a heat pipe. Generally, a heat pipe is a closed tube sealed in a vacuum state after filling a certain amount of working fluid therein. The capillary tube has a passageway for the working fluid therein, and incorporates a capillary structure capable of moving the working fluid through the capillary phenomenon. One end of the closed tube is provided with a heating means or a heating means on the outer side to constitute an evaporating portion (heating portion) for evaporating the working fluid, and the other end is disposed on the outer side with a heat dissipating means or a cooling means, (Cooling section).

This heat pipe uses the latent heat that accompanies when the working fluid circulating inside the closed tube continuously causes the phase change between the liquid vapor and the vapor in the evaporator and the condenser to heat the heat from the heat generating means and the heat dissipating means to the heating means and the cooling means Or vice versa, so that the heat transfer performance (thermal conductivity) can be much greater than that using ordinary pure metal. Accordingly, heat pipes are widely used as basic components for heat transfer in various fields of equipment including heat exchangers, cooling devices, heat transfer devices, and the like.

However, in the conventional heat pipe, there is a wick which is a capillary structure having a required thickness or more by using a porous material such as a metal mesh or sintered metal particles or metal fiber for circulating the working fluid, The thinner the thickness, the lower the performance. Therefore, there is a limitation in application to ultra-thin electronic devices.

In order to solve the problems of the heat pipe using such a wick, recently, the closed tube is formed only as a small-diameter tubular tube, and the capillary phenomenon is induced without using a separate wick, and the working fluid is evaporated, moved, A pulsating heat pipe has been developed and used.

However, the conventional vibrating type heat pipe is studied only for a single-turn PHP shape, and only the liquid such as water is used as the working fluid to be used, There is still a problem that an expected heat transfer performance can not be obtained.

In addition, the conventional vibrating type heat pipe greatly varies its performance depending on the installation angle of the vibrating type heat pipe, and thus has a limitation in that it can perform the role of the vibrating type heat pipe only when installed in a vertical state.

Therefore, it is inevitable to provide an improved flat plate vibrating type heat pipe which is stable regardless of the installation angle, heat transfer efficiency, and stable operation in ultra-thin electronic devices.

Korean Patent Publication No. 10-2012-0042403 Korean Patent No. 10-1250326

Accordingly, it is an object of the present invention to provide a vibrating heat pipe using a micro-electro-mechanical system (MEMS) technology to manufacture a flat plate, thereby enabling a highly efficient heat transfer system To provide.

In the case of a flat plate PHP, a single turn loop, a multi-turn loop, a single diameter channel, a dual- -diameter channels), and to provide a flat vibrating type heat pipe which can be applied at various installation angles having optimum performance regardless of the installation angle of the vibrating type heat pipe.

It is also an object of the present invention to provide a flat vibrating type heat pipe applicable to various mounting angles including a working fluid having an optimum efficiency at a main operating temperature by analyzing characteristics of a working fluid used in a flat vibrating type heat pipe.

In order to achieve the above object, a flat plate vibrating type heat pipe applicable at various installation angles of the present invention includes a long rectangular silicon wafer lower plate; And a channel formed in a shape of a straight line along a longitudinal direction of the lower surface of the silicon wafer with a predetermined depth from the upper surface of the lower surface of the silicon wafer, wherein the channel is formed by a closed loop which is bent at both ends of the lower surface of the silicon wafer, ; A wafer upper plate coupled to the lower surface of the silicon wafer to seal the capillary; And a working fluid filled in the capillary tube. The capillary tube is composed of a combination of a double-headed tube including a pair of channels having different widths and a single tube having a pair of channels having the same width .

At this time, the shape of the capillary can be formed in a multi-turn loop, and the diameter of the capillary going from the condensing part to the evaporating part and the diameter of the capillary going from the evaporating part to the condensing part are the same diameter channels or two diametrically different dual-diameter channels.

The capillary tube may be formed of a combination of a single rectangular tube and a double-walled tube.

In the case of the capillary including the double-headed pipe, the operating characteristics of the vibrating type heat pipe vary greatly depending on the inner diameters of both pipes. When the inner diameter difference is small, the effect is insignificant, If the difference is too large, the force imbalance becomes large, and the frictional pressure loss in the small pipe increases sharply and negatively affects the performance. Therefore, it is necessary to set the inner diameter difference between the two pipes so that the vibrating heat pipe provides optimal heat transfer performance Feature

In addition, in order to exhibit consistent heat characteristics at various installation angles, the thermal characteristics of the vibrating heat pipe must be evaluated accurately. In order to properly analyze and evaluate the thermal characteristics of the vibrating heat pipe, Figure of merit) is developed to provide a vibrating heat pipe with optimal heat transfer performance.

Therefore, since the flat plate vibrating type heat pipe of the present invention is manufactured using MEMS technology, it can be utilized as an efficient cooling system in small-sized and ultra-thin devices as well as small-sized electronic devices such as mobile phones and notebooks, There are advantages to be applied to various types of device products.

In addition, since the flat plate vibrating type heat pipe effectively transfers heat without using external power at all, there is no need to consider the capacity of the power source, the problem of connection with the power source, and the like.

Particularly, since the plate vibrating type heat pipe of the present invention is a cooling system regardless of the installation angle, it has a special effect that there is no restriction on the use of the cooling system after the installation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a main configuration of a flat plate vibrating type heat pipe applicable at various angles of the present invention. FIG.
2 is a view showing a kind of a flat plate vibrating type heat pipe according to the capillary shape of the present invention.
3 is a view of an experimental system configured to analyze operating characteristics of a planar vibrating type heat pipe applicable at various angles of the present invention.
4 is a view showing a thermal characteristic of a flat plate vibrating type heat pipe according to an installation angle of a single rectangular pipe and a double rectangular pipe according to an embodiment of the present invention.
5 is a view showing a thermal characteristic of a flat plate vibrating type heat pipe using a single rectangular pipe and a double rectangular pipe in combination according to an embodiment of the present invention.
6 is a view showing the performance index characteristic of a flat plate vibrating type heat pipe applicable at various angles according to an embodiment of the present invention.

Hereinafter, a flat vibrating type heat pipe of the present invention will be described in detail with reference to the accompanying drawings.

A heat pipe is a typical thermal control device that does not require external power. However, in the conventional heat pipe, there is a wick structure having a predetermined thickness or more for circulating the working fluid. In general, the performance of the heat pipe decreases as the thickness of the heat pipe decreases. Therefore, there is a limitation in application to ultra-thin electronic devices. To overcome these limitations, a vibrating heat pipe without a wick structure has been proposed.

The vibrating type heat pipe has a structure in which a single capillary tube is bent to form a closed loop. When the inside of the closed loop is evacuated and a proper amount of working fluid is injected, an aligned slug-train unit consisting of a liquid slug and a vapor plug is formed in the closed loop. In this case, when heat is applied to one side of the closed loop, the group of aligned bubbles is subjected to high speed self vibration, and heat is transferred from the evaporator to the condenser.

Thus, the vibrating type heat pipe has no wick structure and is simple in structure, so that it can be easily manufactured in a small size so that it can be applied to a micro electronic device.

1, the plate vibrating type heat pipe applicable at various angles of the present invention includes a silicon wafer lower plate 100, a wafer top plate 200, a capillary tube 300, a working fluid filled in the capillary tube, An evaporator 400 disposed at one end in the longitudinal direction of the lower surface of the silicon wafer and disposed at an external heat source, and an evaporator 400 disposed at the other end in the longitudinal direction of the silicon wafer lower plate of the capillary, A condenser 500, and two through-holes 330 used only for injecting or discharging the operating fluid into the flat plate vibrating type heat pipe.

The silicon wafer lower plate 100 may be a silicon wafer having a thickness of about 1 mm used in a typical microelectromechanical system (MEMS), and the wafer upper plate may be made of the same material as the silicon wafer lower plate 100, A glass material may be used to confirm fluid movement and condition. A typical example of a glass material wafer is pyrex glass.

The manufacturing method of the flat plate vibrating type heat pipe is the same as the conventional MEMS manufacturing process, and one preferred embodiment is as follows.

First, a photoresist is deposited on the silicon wafer 100 having a long rectangular shape by physical or chemical methods. (step (a)),

The photoresist is patterned by removing the photoresist in the shape of a capillary tube 300 forming a closed loop bent at both ends of the silicon wafer 100. The patterning may be performed in various ways such as lithography, photolithography, electron beam lithography, ion beam lithography, x-ray lithography, diamond patterning, and the like. (step (b)),

Thereafter, a capillary 300 and a through-hole 330 are formed on the silicon wafer 100 by wet or dry etching. In this case, both wet etching and dry etching can be applied. In the present invention, deep reactive ion etching (RIE), which is the most typical wet / dry etching method, is applied and etched to a depth of 500 m.

When the photoresist remaining on the silicon wafer is removed and the upper surface of the glass substrate is bonded to the upper surface of the silicon wafer 100, the structure of the flat plate vibrating type heat pipe is completed. In this case, by taking advantage of the property of the glass having a very flat adhesive surface, anodic bonding can produce a flat vibrating heat pipe having excellent adhesive performance.

Lastly, when a working fluid is injected through the through holes 330 provided on both sides of the flat plate vibrating type heat pipe and the through holes 330 are sealed, a flat plate vibrating type heat pipe is completed. At this time, by providing the through holes 330 on both sides of the plate vibrating type heat pipe, when the working fluid is injected or discharged, the working fluid or air is poured on one side and the vacuum fluid is sucked on the other side, It is possible. This enables much faster and more precise control than when only one through-hole is used.

On the other hand, the thermal characteristics of the flat plate vibrating type heat pipe are greatly affected by the shape of the capillary 300 to be etched on the silicon wafer 100.

2, the shape of the capillary 300 can be divided into a single turn loop and a multi-turn loop according to the number of turns of the capillary tube. And are classified into a single diameter channel and a dual-diameter channel depending on whether the diameter of the capillary is changed or not.

Also, capillaries that are typically etched by dry or dry / wet methods are closer to the shape of a quadrilateral rather than a circular one. Therefore, the square capillary is changed into an equivalent circular tube, and the performance of the plate vibrating type heat pipe is analyzed. The diameter (D _h ) of the equivalent circular tube is expressed by the following equation.

(Where A _C is the area, p _w is the length of the perimeter, w is the width of the capillary channel, and h is the height of the capillary)

In the present invention, an experimental system as shown in FIG. 3 is configured to analyze operational characteristics of a flat plate vibrating type heat pipe applicable at various angles.

First, in order to measure the surface temperature of the flat plate vibrating type heat pipe applicable at various angles of the present invention, a plurality of thermocouples 600 are installed in each of the heat generating portion, the condensing portion, and the heat insulating portion. Typical applicable thermocouples are K-type and Omega, and installed thermocouples are transmitted to a control computer 770 through a data acquisition device (DAQ) 760.

Meanwhile, a heat wire 610 coated with Nichrome is connected to a DC power supply (E3631) 710 to provide heat to the heat generating portion of the flat plate vibrating type heat pipe. In order to take heat away from the condensing portion of the flat plate vibrating type heat pipe, the condensing portion is wrapped by the copper block 620 having a high thermal conductivity. The copper block is filled with a certain amount of water supplied by a bath circulator (RW- Temperature water was allowed to flow.

In order to understand the thermal characteristics according to the installation angle of the plate vibrating type heat pipe applicable at various angles, a support base 640 for mounting the plate vibrating type heat pipe is provided, and the support base 640 is rotated, And a rotation unit 650 for changing the installation angle.

Meanwhile, in order to more accurately grasp the thermal characteristics of the flat plate vibrating type heat pipe, it is preferable to provide the flat plate vibrating type heat pipe inside the vacuum chamber 800. The vacuum chamber 800 is maintained in a vacuum state by a rotary pump 810, and preferably maintained at 0.01 torr or less.

At this time, in order to visually observe the behavior of the working fluid inside the flat vibrating type heat pipe, one side of the vacuum chamber 800 is formed as a window 820 made of a transparent glass, And a high-speed camera 720 for photographing the flat plate vibrating type heat pipe through the window 820 from outside. The high-speed camera 720 photographs the flat plate vibrating type heat pipe, and the photographed information transmits the image data to the control computer 770.

On the other hand, two kinds of working fluids are used, FC-72 and ethanol, and the characteristics of FC-72 and ethanol are shown in Table 1.

Properties of working fluid Working fluid Breaking point
(C) Surface tension
(mN / m) Latent heat
(kJ / kg) density
(kg / m3) Vapor density
(kg / m3) Viscosity coefficient
(Pass) specific heat
(kJ / KgK) Ethanol 78.4 22.27 846.19 734.79 1.75 430.43 3.202 FC-72 56 9.48 84.73 1620.94 13.01 447.0 1.096

Experiments on the flat vibrating type heat pipe of the present invention are shown in FIG. 4 with the above experimental system. FIG. 4A shows the case where ethanol is used as the working fluid, and FIG. 4B shows the case where FC-72 is used as the working fluid.

As shown in FIGS. 4A and 4A, the heat resistance of the flat plate vibrating type heat pipe having a double-sided rectangular shape is much lower than that of a single rectangular plate, which shows that the performance of the double-sided type is better.

In addition, in the case of a single rectangular tube, it has the largest value at 0 ° and the lowest value at 90 °. On the other hand, in the case of a double-headed landscape, as shown in FIG. 4A, the smallest diameter difference (1.1-0.9 mm) has the largest value at 0 ° and the lowest value at 90 °, It can be seen that when the difference in diameter is 0.6 mm or more, the angle is not greatly affected.

However, as shown in FIG. 4A, it can be seen that when the diameter of the tooth is 0.6 mm, the tooth having the lowest value does not have a lower value as the difference in diameter becomes larger.

Therefore, the above-mentioned tendency means that there is a value in which the difference in diameters of the two pipes is optimal, and the difference in diameters in which the plate vibrating type heat pipe is the optimum performance is expressed by the following equation.

(Where D is the difference between the two diameters, D _avg is the average of the two diameters)

As shown in FIG. 5, in order to examine the tendency of using both a single rectangular pipe and a double rectangular pipe in a flat vibrating type heat pipe, in a flat vibrating type heat pipe having five capillaries, ) And three double-sided landscapes (Fig. 5b).

As shown in FIG. 5A, when one of the double-sided landscapes is included, the thermal conductivity tends to increase as the angle increases. When the angle is between 0 ° and 10 °, the thermal property is not good. On the other hand, when three double-headed landscapes are included, the thermal conductivity is high on the warhead regardless of the angle.

Therefore, in the case of using a single rectilinear tube and a double rectilinear tube simultaneously, it can be seen that the thermal characteristics of the plate vibrating type heat pipe are largely changed according to the ratio including the double rectilinear tube. In order to accurately evaluate the performance of the flat vibrating type heat pipe, (M _PHP , Figure of Merit).

(Here, N is the number of channels of yijungjik scenery, N _t is the total number of channels, ρ _l is the working fluid density, σ is the surface tension, w ₁ has a small channel in the width, w ₂ is yijungjik view of the large channel in yijungjik officer width, h _fg is heat (latent heat), w ₁ for absorbing when the working fluid evaporates is the width of the large channel, w ₂ is the width of the small channel, w is the width of the channel in a single straight-scenery, μ ₁ is a working fluid liquid , C is the coefficient of friction, h is the height of the channel (depth), and all units apply SI units)

In this case, the frictional coefficient C can be calculated in various ways, but in the present invention, a fixed value of 4.0, which is a preferable representative value, is used for easy calculation.

As shown in FIG. 6, the plate vibrating type heat pipe shows a large difference in thermal characteristics depending on the difference in the diameter of the double-headed pipe, the degree of mixing of the single pipe and the double pipe, and the difference in the working fluid.

As shown in FIG. 6A, it can be seen that the difference of the dimensionless diameters (ΔD / D _avg ) showing the optimum thermal performance in the double-headed landscape is in the range of 0.3 and 0.5. Within the above range, the thermal conductivity of the flat plate vibrating type heat pipe has a value of 90% or more based on the maximum value. From FIG. 6C, it can be seen that the same result can be obtained even if the working fluid is changed from ethanol to FC-72.

In addition, it can be seen from the above experiment that the thermal characteristic of the plate vibrating type heat pipe is not influenced by the installation angle when the figure of merit is 2 × 10 ⁵ W / m ² or more in a double-side view. Therefore, this means that when designing a flat plate vibrating type heat pipe, the performance index should be designed to be 2 × 10 ⁵ W / m ² or more.

In addition, as shown in FIG. 6B, it can be seen that the thermal characteristics of the flat plate vibrating type heat pipe are improved as the application ratio of the double-headed view increases. As described above, in order to design the figure of merit to be more than 2 × 10 ⁵ W / m ² , three or more (60% or more) double-headed landscapes must be used, and the difference in the diameter of the multi- D _avg ) should be within the range of 0.3 and 0.5.

Designing a flat vibration type heat pipe is based on the figure of merit (M _PHP) is configured as described above, and those skilled in the art the described contents, so the flat characteristics of the vibration type heat pipe design, have a significant effect by such as operating temperature, the working fluid of this invention It will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

The plate vibrating type heat pipe of the present invention can be applied to various industrial fields such as various electronic apparatuses, small internal combustion engines, small machinery and the like, and has a special effect of exhibiting a certain level of heat without regard to the installation angle of the plate vibrating type heat pipe There is sufficient industrial availability.

100 Silicon wafer Lower plate 200 Wafer top plate
300 capillary 330 through-hole
400 evaporator 500 condenser
600 thermocouple 610 hot wire
620 copper block 640 support
650 rotation part
710 DC power supply 720 high speed camera
750 Constant temperature circulation tank 760 Data collection device
770 Control computer 800 Vacuum chamber
810 Rotary Pump 820 Window

Claims (10)

A long rectangular bottom plate;
And a channel formed in a straight line shape along the longitudinal direction of the lower plate with a predetermined depth from the upper surface of the lower plate, wherein the channel is bent at both ends of the lower plate to form a closed loop;
A top plate coupled to the bottom plate to seal the capillary;
And a working fluid filled in the capillary tube
Wherein the capillary tube is a combination of a double rectangular tube including a pair of channels having different widths and a single rectangular tube including a pair of channels having the same width,
The performance of the flat plate vibrating type heat pipe is expressed by the following performance index (M _PHP ), and the performance index (M _PHP ) has a value of 2 × 10 ⁵ W / m ² or more Possible plate oscillating heat pipe.

(Here, N is the number of channels of yijungjik scenery, N _t is the total number of channels, ρ _l is the working fluid density, σ is the surface tension, w ₁ has a small channel in the width, w ₂ is yijungjik view of the large channel in yijungjik officer width, h _fg is heat (latent heat), w ₁ for absorbing when the working fluid evaporates is the width of the large channel, w ₂ is the width of the small channel, w is the width of the channel in a single straight-scenery, μ ₁ is a working fluid liquid , C is the coefficient of friction, h is the height of the channel (depth), and all units apply SI units) The method according to claim 1,
Characterized in that the two diameters of the double-headed obturator satisfy the following equation: < EMI ID = 1.0 >
0.3? D / D _avg ? 0.5
(Where D is the difference between the two diameters, D _avg is the average of the two diameters) The method according to claim 1,
Wherein at least 60% of the capillaries are made of a double-sided tube. delete delete A method for manufacturing a flat plate vibrating type heat pipe using a microelectronic system (MEMS) process,
(a) depositing a photoresist on top of a long rectangular silicon wafer;
(b) removing and patterning the photoresist in the form of a capillary having a closed loop curved at both ends of the silicon wafer;
(c) etching the silicon wafer to form a capillary on top of the silicon wafer lower plate;
(d) removing the photoresist remaining on the silicon wafer;
(e) bonding a wafer top plate to the top of the silicon wafer;
Wherein the capillary is patterned to have a combination of a double-headed landscape including a pair of channels having different widths and a single rectangular tube including a pair of channels having the same width,
The performance of the flat plate vibrating type heat pipe is expressed by the following performance index (M _PHP ), and the performance index (M _PHP ) has a value of 2 x 10 ⁵ W / m ² or more. A method of manufacturing a flat plate vibrating type heat pipe.

(Here, N is the number of channels of yijungjik scenery, N _t is the total number of channels, ρ _l is the working fluid density, σ is the surface tension, w ₁ has a small channel in the width, w ₂ is yijungjik view of the large channel in yijungjik officer width, h _fg is heat (latent heat), w ₁ for absorbing when the working fluid evaporates is the width of the large channel, w ₂ is the width of the small channel, w is the width of the channel in a single straight-scenery, μ ₁ is a working fluid liquid , C is the coefficient of friction, h is the height of the channel (depth), and all units apply SI units) The method according to claim 6,
Wherein the two diameters of the double-headed obturator satisfy the following equation: < EMI ID = 1.0 >
0.3? D / D _avg ? 0.5
(Where D is the difference between the two diameters, D _avg is the average of the two diameters) The method according to claim 6,
Wherein at least 60% of the capillaries are made of a double-sided tube. delete delete

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