KR102068392B1 - Flexible heat transfer device - Google Patents

Abstract

The present invention relates to a flexible heat transfer device, wherein the flexible heat transfer device according to the present invention is formed of a soft material, an intaglio first flow path through which a working fluid of a liquid flows is formed thereon, and heat is supplied from one end of the lower portion. A first container in which the evaporation process of the working fluid takes place, a second material formed of a soft material, positioned above the first container, and having a negative second flow path through which a working fluid of gas flows; And a moving part formed between the first container and the second container, the moving part being formed of a membrane of a soft material to allow the working fluid to move between the first flow path and the second flow path.

Description

Flexible heat transfer device {FLEXIBLE HEAT TRANSFER DEVICE}

The present invention relates to a flexible heat transfer device, and more particularly, to a flexible heat transfer device formed of a soft material and performing heat transfer in a heat pipe structure.

1 shows the process of mass circulation of working fluid inside a heat pipe, in which the heat pipe is evaporated and moved to the heat supplied by the working liquid as a heat source in a closed container, and the evaporated working gas releases heat and condenses back into the liquid. It is a heat transfer device that circulates and repeats the process of transferring heat from the heat source to the outside.

Heat pipes are very promising in that they transfer heat from the heat source to the outside by using latent heat between liquid and gas and convection of the working gas, but it is difficult to control because the working fluid inside the closed system is used. This has the disadvantage of being prone to collapse.

In particular, if the amount of inflow and outflow by the phase change is different, the deformation of the working liquid occurs. In particular, when the evaporation amount (D-> A) is greater than the liquid inflow amount (C-> D), the interface of the liquid on the flow path retreats as shown in FIG. 2, where the amount of heat transfer from the heat source is drastically reduced and the heat pipe system cannot be collapsed. This is called the dry out limit.

 In addition, evaporation of the working liquid usually occurs at the liquid-gas interface but can also occur at the liquid-solid interface. The evaporation occurring at the liquid-solid interface creates bubbles in the system, and bubbles may act as a resistance to the movement of the working fluid, causing the heat pipe system to collapse.

Republic of Korea Patent Publication No. 10-2016-0113103

Therefore, an object of the present invention is to solve such a conventional problem, the first vessel in which the working fluid flows in the liquid phase and the working fluid in the gas flow in the heat transfer device for performing the heat transfer in accordance with the principle of the heat pipe 2 Form a thin film membrane of flexible material to increase the marginal pressure difference, so that the interface retreats at the evaporator to prevent system collapse by the dry system, and to form a container of soft material to delay the pressure reduction of the working liquid during evaporation. The present invention provides a soft heat transfer device that reduces bubble generation due to evaporation at a solid and liquid interface to prevent system collapse due to bubbles.

Problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

The object is, in accordance with the present invention, is formed of a soft material, the intaglio first flow path is formed in which the working fluid of the liquid flows on the upper side, the heat is supplied from one end of the lower portion of the evaporation process of the working fluid occurs A first container; A second container formed of a soft material and positioned above the first container, and having a negative second flow path through which a working fluid of gas flows; And a moving part formed between the first container and the second container, the moving part being formed of a flexible material membrane to allow the working fluid to move between the first flow path and the second flow path. Can be.

Here, the first container may be formed of a hydrophilic soft material.

Here, the first container may be formed of a hydrophilic hydrogel.

Here, a plurality of pillars may be formed in the second flow path to support the second flow path so as not to collapse by an external force.

Here, the first flow path may be formed of a plurality of straight flow paths arranged in parallel.

Here, a plurality of pillars may be formed in the first flow passage to support the first flow passage so as not to collapse due to bubble generation.

According to the flexible heat transfer apparatus of the present invention as described above, the limit pressure is formed by forming a thin film membrane made of a flexible material in which the working fluid moves between the first vessel in which the working fluid in the liquid flows and the second vessel in which the working fluid in the gas flows. By increasing the difference, the interface delays the retreat at the evaporator, thereby preventing the system collapse by the dry system.

In addition, by forming a container with a hydrophilic soft material and receiving heat from a heat source, when the working fluid evaporates, the pressure drop inside the working fluid is delayed, thereby suppressing bubble generation due to evaporation at the solid and liquid interface. It also has the advantage of preventing system collapse.

In addition, the entire device may be formed of a flexible material and may be used as a heat transfer device of a flexible device such as a wearable device.

1 is a view for explaining the general operating principle of the heat pipe.
2 is a view showing a state in which the working fluid is evaporated by the heat source and the interface retreats.
3 is a cross-sectional view showing a flexible heat transfer apparatus according to an embodiment of the present invention.
4 is a view showing a first flow path of the first container along a-a 'in FIG. 3.
FIG. 5 is a view showing a second flow path of the second container along b-b 'of FIG. 3.

Specific details of the embodiments are included in the detailed description and drawings.

Advantages and features of the present invention, and methods for achieving them will be apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be embodied in various different forms, and the present embodiments merely make the disclosure of the present invention complete, and those of ordinary skill in the art to which the present invention belongs. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, the present invention will be described with reference to the drawings for describing a flexible heat transfer apparatus according to embodiments of the present invention.

3 is a cross-sectional view illustrating a flexible heat transfer apparatus according to an embodiment of the present invention, FIG. 4 is a view showing a first flow path of a first container along a-a 'of FIG. 3, and FIG. 5 is FIG. 3. It is a figure which shows the 2nd flow path of a 2nd container along b-b 'of the figure.

The flexible heat transfer apparatus according to an embodiment of the present invention may include a first container 110, a second container 120, and a moving unit 130.

The first container 110 has a negative first flow path 112 through which a working fluid in a liquid flows is formed at an upper portion thereof, and receives the heat from a heat source at one end so that the working liquid evaporates into a gas. In the following description, part D of FIG. 3 for receiving heat from a heat source positioned at one end of the first container to evaporate the working liquid into gas will be referred to as an evaporator.

As shown in FIG. 4, the first flow path 112 may be formed of a plurality of straight flow paths arranged in parallel. Although described later, a thin film moving part 130 is formed between the first container 110 and the second container 120 positioned above the first container 110, so that the first flow path 112 of the intaglio is inclined. Can form a flow path sealed by the moving unit 130 located above. As described above, an evaporation part is formed at one end of the first flow path 112, and at the other end, a working fluid condensed by heat release and liquefied again is supplied onto the first flow path 112, so that the first flow path 112 is formed. Due to the pressure difference therein, the first flow path 112 flows.

At this time, in the present invention, the first container 110 may be formed of a soft material, preferably, is formed of a hydrophilic soft material. For example, it may be formed of a hydrophilic hydrogel, but is not limited thereto. The physical meaning of forming the first container 110 of a hydrophilic soft material in the present invention will be described later.

The second container 120 has a negative second flow path 122 through which a gaseous working fluid flows, which is located between the first container 110 and the second container 120. The second flow passage 122 together with 130 forms a closed flow passage to form a path through which the working gas moves. The working fluid evaporated from the evaporator passes through the moving part 130 formed as a membrane of a thin film, and is supplied to the second flow path 122 of the second vessel 120, and the gas supplied onto the second flow path 122. The working fluid of is moved on the second flow path 122 by the pressure difference therein and again moves to the first flow path 112 through the moving part 130 to release heat and condense to change into a liquid.

In this case, like the first container 110, the second container 120 may be formed of a soft material, and preferably, the second container 120 may be formed of the same material as the first container 110.

 As shown in FIG. 5, a plurality of pillars 124 may be formed on the second flow path 122. The flexible second container 120 is deformed by an external force to deform the second flow path 122. To prevent the system from collapsing.

Similarly, in the first container 110 of FIG. 4, the surface 114 formed between the first flow paths 112 may serve as the pillar 124 of the second container 120. In addition, like the second flow path 122, the first flow path 112 may also be formed in a form in which a plurality of pillars (not shown) are formed as shown in FIG. 5.

At this time, the pillar 114 (not shown) formed on the surface 114 or the first flow path 112 between the first flow path 112 as shown in FIG. 4 is the first flexible container 110 by an external force. Is deformed to block the first flow path 112 to prevent the system from collapsing, and at the same time, as described later, the first flow path is formed by bubbles generated by evaporation at the interface between the first vessel 110 and the working liquid. 112 may serve to support the collapse. In addition, as will be described later, as the area of the surface 114 between the first flow path or the pillar (not shown) formed in the first flow path increases, the pressure drop in the liquid is delayed, thereby delaying the collapse of the system due to bubble formation. Can be.

The moving part 130 is formed of a flexible membrane and is formed between the first container 110 and the second container 120. In the drawings, the first container 110 and the second container 120 are formed on the front surface, which is formed between the first flow path 112 and the second flow path 122 and is closed as described above. It is not limited to this as long as it can form. In this case, when the thickness of the moving part 130 is thick, the moving part 130 may act as a resistance to the movement of the working fluid between the first flow path 112 and the second flow path 122, so that the moving part 130 is preferably made of a thin film. Do.

As described above, the present invention dissipates the heat of the heat source according to the principle of the heat pipe, the operation process will be described. The heat supplied from the heat source evaporates the working fluid of the liquid on the first flow path 112 in the evaporator. The working gas that has evaporated and changed phase into gas moves through the pores of the moving part 130 to the second flow path 122, and the working gas supplied to the second flow path 122 is caused by a pressure difference therein. It moves to the rear end. The working gas reaching the rear end passes through the moving part 130 again, and releases heat to condense and change phase into liquid. The working liquid, which is condensed and supplied again to the rear end of the first flow path 112, flows again toward the evaporation part due to the pressure difference in the interior, and repeats the above process and repeats the latent heat and phase transfer by convection. It can transmit heat from the heat source and release it to the outside.

Hereinafter, the features of the flexible heat transfer apparatus of the present invention described with reference to FIGS. 3 to 5 will be described.

When the temperature of the evaporator increases, the amount of evaporation of the working fluid in the liquid phase increases, which can be explained by the change of the shape of the interface. Evaporation of the liquid occurs in a thin liquid film near the contact line, and an increase in the amount of evaporation means that the thickness of the liquid film is reduced due to the smaller contact angle. This increases the radius of curvature of the interface to reduce the pressure of the liquid in the evaporation zone, expressed as Laplace pressure. Since the flow rate supplied to the evaporator on the first flow path 112 is proportional to the pressure difference, the pressure drop increases the inflow of the working liquid into the evaporator. Preservation is achieved.

However, there is a limiting contact angle at which the interface at the evaporator retreats, and the limit pressure difference at this time may be expressed by the following equation (1).

<Equation 1>

 (Where σ is the surface tension and r is the radius of the pore)

In other words, as r becomes smaller, the threshold pressure difference increases, which can delay the retreat of the interface.

In addition, the flow rate of the liquid flow section corresponding to the first flow path 112 may be represented by the following equation (2) according to Carman-Kozeny theory.

 <Equation 2>

는 기공도,

은 도관의 반지름,

는 작동액체의 점성도,

는 비틀림 정도,

은 액상유동 구간의 길이이다.)(here,

The porosity,

The radius of the conduit,

Is the viscosity of the working liquid,

Is the degree of twist,

Is the length of the liquid flow section.)

Based on Equation 1 and Equation 2, in the heat pipe structure of the present invention, the following two cases can reach the dry system and the system may collapse.

(1) As the temperature of the evaporator rises, the contact angle decreases. When the limit pressure difference is reached and the limit retraction contact angle is reached, the interface of the liquid retreats.

(2) Although the evaporation amount increased due to the increase in the temperature of the evaporation unit, the liquid interface retreats when the flow rate is insufficient due to the large flow resistance of the liquid.

Therefore, the width r of the first flow path 112 can be reduced in order to increase the threshold pressure difference and delay the retreat of the interface. However, this can act as a flow resistance in the flow in the first flow path 112 as shown in Equation 2 can reduce the flow rate of the working liquid supplied to the evaporator.

Accordingly, in the present invention, the first flow path 112 is formed of a plurality of flow paths having an optimized width as shown in FIG. 4 to minimize the flow resistance but increase the limit pressure difference. Furthermore, in the present invention, the micropore formed in the membrane-shaped moving part 130 forming the upper surface of the flow path acts to decrease the radius r of the pore in Equation 1, thereby increasing the limit pressure difference. The retraction of the interface can be delayed.

In addition, evaporation of the working liquid usually occurs at the liquid-gas interface of the working liquid, but may also occur at the liquid-solid interface. In this case, if bubbles are generated at the interface between the solid first vessel 110 and the working liquid, and these bubbles block the micropores, they may act as a flow resistance to the working liquid and collapse the system. Therefore, it is necessary to suppress the generation of bubbles due to evaporation at the liquid-solid interface.

When the limit pressure is reached at the liquid-solid interface, evaporation occurs. The magnitude of the limit pressure is larger as the bonding force between the working liquid and the first vessel 110 increases. Therefore, when water is used as the working liquid, it is preferable to form the first vessel 110 with a hydrophilic material to increase the magnitude of the threshold pressure.

In addition, as the evaporation occurs and the volume of the liquid decreases, the pressure inside the liquid decreases. In this case, when the first flow path 112 through which the working liquid flows is formed of a soft material, the pressure inside the liquid becomes equal to the tensile stress of the soft material, and when the first flow path 112 is formed of the soft material, the pressure is increased. You can delay the rate of decline.

The pressure of the working liquid in the present invention can be approximated by the following equation (3).

<Equation 3>

는 작동액체의 압력,

는 제 1 용기(110)의 Young's modulus,

는 액상유동 경로에서 액체가 차지하는 비율,

는 순 증발량(증발량-응축량)을 의미한다.)(Here,

Is the working liquid pressure,

Young's modulus of the first vessel (110),

Is the proportion of liquid in the liquid flow path,

Means net evaporation (evaporation-condensation).)

Therefore, as the first container 110 is formed of a softer soft material, the larger the ratio of the soft material in the liquid flow path is, the lower the rate of decrease in the internal pressure of the working liquid is, and due to evaporation occurring at the liquid-solid interface, The generation of bubbles can be suppressed.

The scope of the present invention is not limited to the above-described embodiments but may be implemented in various forms of embodiments within the scope of the appended claims. Without departing from the gist of the invention claimed in the claims, it is intended that any person skilled in the art to which the present invention pertains falls within the scope of the claims described herein to various extents which can be modified.

110: first container 112: first flow path
120: second container 122: second flow path
124: pillar 130: moving part

Claims (6)

A first container formed of a soft material and having an intaglio first flow path through which a working fluid of a liquid flows, and receiving heat from one end of the lower part to evaporate the working fluid;
A second container positioned above the first container and having a negative second flow path through which a working fluid of gas flows; And
A moving part formed between the first container and the second container, the moving part being formed of a flexible material membrane for allowing the working fluid to move between the first flow path and the second flow path,
The first container is formed of a soft material to reduce the rate at which the pressure of the working fluid decreases when the working fluid evaporates, so that bubbles are generated due to evaporation occurring at the interface between the working fluid of the liquid and the first container. To prevent pores of the membrane to decay the heat transfer system. The method of claim 1,
And the first container is formed of a hydrophilic soft material. The method of claim 2,
The first vessel is a flexible heat transfer device formed of a hydrophilic hydrogel. The method of claim 1,
And a plurality of pillars formed in the second flow passage to support the second flow passage so as not to collapse by an external force. The method of claim 1,
And the first flow path is formed of a plurality of straight flow paths arranged in parallel. The method of claim 1,
And a plurality of pillars formed in the first flow passage so as to prevent the first flow passage from collapsing due to bubble generation.

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