Passive liquid metal thermal switch and electronic device using the same

Abstract

The present invention discloses a passive liquid metal thermal switch and an electronic device using the same. The thermal switch includes a double-layer cover plate, a fine hollow layer located between the double-layer cover plates, a plurality of array-type liquid holding cavities formed between the double-layer cover plates, and liquid metal filled in the liquid holding cavities; the fine hollow layer is connected to the liquid holding cavity; the cross-sectional area of ​​the fine hollow layer is greater than the sum of the cross-sectional areas of all liquid holding cavities; the liquid metal can flow between the fine hollow layer and the liquid holding cavity as the temperature changes, so that the thermal switch automatically switches between high thermal resistance and low thermal resistance states. The present invention has a simple structure, and can realize automatic opening and closing of the thermal switch only through the wettability of the liquid metal and the capillary action of the fine hollow layer, and realizes two forms of heat dissipation and heat preservation as the temperature changes. When applied to electronic devices, it can realize passive temperature control of electronic devices, prevent internal chips and batteries from overheating or overcooling, and increase the service life of electronic devices.

Description

Technical Field

[0001] The present invention relates to the field of thermal management technology, and in particular to a passive liquid metal thermal switch and an electronic device using the same. Background Art

[0002] In recent years, electronic devices have developed rapidly, and many electronic devices have become daily necessities in life. People have higher and higher requirements for the performance of electronic devices. Therefore, many devices use high-performance chips and batteries. For chips, a large amount of heat energy is generated under high-frequency operation, and batteries also release a lot of heat during the charging and discharging process, which also brings corresponding problems: high-power density equipment has a large heat dissipation demand and uneven temperature distribution. In addition, when the temperature is low, lithium-ion batteries consume power faster in low temperature environments, and stop working when their own temperature is lower than a certain temperature. Generally speaking, the applicable temperature range of lithium-ion batteries is 0 to 50°C. When this range is exceeded, the protection program will be triggered and the battery will shut down automatically.

[0003] In this case, the thermal management of electronic equipment is often not a simple heat dissipation temperature, but faces upper and lower temperature control, dissipating heat at high temperatures and maintaining temperature at low temperatures.

[0004] A thermal switch is a device that achieves heat control by changing the thermal resistance of a heat conduction channel. A thermal switch allows heat to pass through in its ON or closed state, and blocks heat in its OFF or disconnected state. A thermal switch allows heat to pass through in its ON or closed state, and blocks heat in its OFF or disconnected state. These switches are mechanically transmitted and rely on contact between two conductive surfaces (typically made of metal) to allow heat to pass. When the two surfaces are retracted, heat cannot be conducted between the two surfaces except through an air gap. If the device is located in a vacuum, then heat conduction is completely blocked in the off state. Another type of thermal switch involves injecting a gas or liquid into or withdrawing it from a container. When the container is full, heat is conducted. When empty, no conduction occurs, although radiation transfer may still occur through the container. The thermal resistance of the thermal switch in the open state depends on the thermophysical properties of the gap, and the thermal resistance of the thermal switch in the closed state depends on the state of contact between the surfaces. The switches described in the present invention rely on the expansion of a liquid between two heat-conducting surfaces to replace the air layer therein to control the passage of heat. When the liquid contracts, heat can only be conducted through the air layer between the heat-conducting surfaces. Most of the thermal switches in the literature are mechanical devices, which are widely used in the fields of aviation and temperature difference power generation.

[0005] The on / off ratio is a key indicator for measuring the performance of passive liquid metal wetting thermal switches. The on / off ratio is defined as the effective thermal resistance ratio of the on / off state. It can be calculated based on the effective area ratio (A) of the double-layer metal plate in the on / off state of the unit structure. off / A on), indirectly estimating the ratio of the thermal resistance in the closed state to the thermal resistance in the open state of the thermal switch (R off / R on ), we can get that the design structure A off / A on With R off / R on The thermal resistance is calculated by the following equation:

[0006] R off =2×R Cu +R air

[0007] R on =2×R Cu +R Ga

[0008]

[0009] Among them, δ represents the thickness of the material, A represents the area of ​​the heat exchange unit, and λ represents the thermal conductivity. Therefore, the switch ratio of this structure is:

[0010]

[0011] The switch ratio indicates the ratio of the thermal resistance in the ON state to the current in the OFF state. The larger the switch ratio is, the higher the thermal resistance control capability of the passive liquid metal thermal switch 100 is.

[0012] Wetting refers to the phenomenon that the contact between liquid and solid causes the solid surface energy to decrease. The common wetting phenomenon is the process in which the gas on the solid surface is replaced by liquid. For example, water spreads on a clean glass plate to form a new solid / liquid interface, replacing the original solid / gas interface. The completion of this process is closely related to the surface properties of the solid and liquid and the interaction between solid and liquid molecules. Wetting actually involves the gas, liquid, and solid three-phase interface. The angle from the solid-liquid interface through the liquid to the gas-liquid interface at the junction of the three phases is called the contact angle, which is represented by θ and is usually calculated by the Young equation. This equation is the basis for studying liquid-solid wetting. Generally speaking, the size of the contact angle θ is the criterion for determining the wettability. If θ=0, the liquid completely wets the solid surface and the liquid spreads on the solid surface; 0<θ<90°, the liquid can wet the solid, and the smaller θ is, the better the wettability; 90°<θ<180°, the liquid cannot wet the solid; θ=180°, there is no wetting at all, and the liquid condenses into small balls on the solid surface.

[0013] Liquid metal mainly studies gallium and gallium-based liquid metals to replace mercury, among which gallium, eutectic gallium-indium alloy, and gallium-indium-tin alloy have melting points of 29.78°C, 15.6°C, and 11°C, respectively. This type of alloy is liquid at room temperature, and has excellent conductivity of metals and fluidity of liquids, and is non-toxic and has low vapor pressure. Summary of the invention

[0014] The present invention provides a passive liquid metal thermal switch and an electronic device using the thermal switch, the purpose of which is to utilize the characteristics of liquid metal wettability and surface tension changing with temperature, so that the liquid metal can passively control the thermal switch to switch between a heat dissipation state with high heat transfer capacity and a heat preservation state with low heat transfer capacity according to temperature changes under the action of capillary force, thereby realizing automatic control of thermal management methods of chips, batteries, electronic devices, etc. at different temperatures.

[0015] In order to achieve the above object, the present invention adopts the following technical solution:

[0016] A passive liquid metal thermal switch comprises a double-layer cover plate, a micro-hollow layer located between the double-layer cover plates, a plurality of array-type liquid containing cavities formed between the double-layer cover plates, and liquid metal filled in the liquid containing cavities; the micro-hollow layer is connected to the liquid containing cavities; the cross-sectional area of ​​the micro-hollow layer is greater than the sum of the cross-sectional areas of all the liquid containing cavities; the liquid metal can flow between the micro-hollow layer and the liquid containing cavities as the temperature changes, so that the thermal switch automatically switches between a high thermal resistance state and a low thermal resistance state; the liquid metal can flow between the micro-hollow layer and the liquid containing cavities of the liquid metal thermal switch according to the change of its wettability with the temperature, so that the liquid metal thermal switch can automatically adjust the transmission capacity of thermal energy;

[0017] When the liquid metal heat switch is heated, the heat energy transmission capacity increases when the liquid metal flows from the liquid containing cavity to the fine hollow layer; when the temperature decreases, the liquid metal shrinks from the fine hollow layer to the liquid containing cavity, and the heat energy transmission capacity decreases.

[0018] As one of the preferred solutions of the present invention, a plurality of grooves are uniformly or non-uniformly formed on the inner surface of the double-layer cover plate to form the liquid containing cavity.

[0019] As one of the preferred solutions of the present invention, the liquid holding chamber is hemispherical, semi-cylindrical, spherical or cylindrical, and the liquid holding chambers can be arranged in a dotted array, a linear array, or a distribution of dots / lines forming a certain pattern.

[0020] As one of the preferred solutions of the present invention, the structure of the micro-hollow layer can be a single-layer or multi-layer micro-channel or porous material, and there is gas in the micro-hollow layer.

[0021] As one of the preferred solutions of the present invention, a partition structure is provided at the position of the micro-hollow layer between the liquid containing cavities, and the partition structure divides the micro-hollow layer into a plurality of independent regions, and the number of liquid containing cavities in each independent region is the same or different.

[0022] As one of the preferred solutions of the present invention, the entire or partial area of ​​the micro-hollow layer and / or the inner wall of the liquid containing cavity is provided with a hydrophilic and / or hydrophobic surface, and / or an isolation surface or an anti-corrosion surface.

[0023] As one of the preferred solutions of the present invention, the passive liquid metal thermal switches are stacked in a direction perpendicular to the surface of the double-layer cover plate to form a multi-layer structure.

[0024] As one of the preferred embodiments of the present invention, the liquid metal is single-substance liquid metal gallium, gallium-indium alloy, gallium-indium-tin alloy, gallium-zinc alloy, etc.

[0025] As one of the preferred solutions of the present invention, the double-layer cover plate material is metal and alloy material, PC material thermal conductive plastic, ABS material thermal conductive plastic, plastic-coated aluminum thermal conductive material, shaped composite phase change material, etc.

[0026] The present invention also provides an electronic device using the passive liquid metal thermal switch as described above.

[0027] After adopting the above technical solution, the present invention has the following advantages:

[0028] Since different features of the liquid metal thermal switches involved in the invention can achieve different beneficial effects, only some liquid metal thermal switches are given as examples here to illustrate their beneficial effects. It can be associated in this technical field that the beneficial effects of the invention are not limited to the following examples.

[0029] The passive liquid metal thermal switch of the present invention provides a cavity for containing liquid metal and a fine hollow layer between the double-layer cover plate, so that the liquid metal can flow between the fine hollow layer and the liquid containing cavity as the temperature changes, so that the thermal switch automatically switches between high thermal resistance and low thermal resistance. The present invention has a simple structure, and can realize automatic opening and closing of the thermal switch only through the wettability of the liquid metal and the capillary action of the fine hollow layer, and realizes two forms of heat dissipation and heat preservation as the temperature changes.

[0030] Moreover, this process does not require additional energy or human intervention, and is energy-saving and environmentally friendly.

[0031] In the passive liquid metal thermal switch of the present invention, the structures of the liquid containing cavity and the micro-channel micro-hollow layer can be freely designed according to specific application conditions, and are suitable for various component structures to be heat-dissipated or heat-insulated.

[0032] The present invention applies a passive liquid metal thermal switch to electronic devices, such as mobile terminals such as mobile phones and laptop computers, to enhance / reduce heat exchange at different temperatures to regulate the temperature of the electronic device itself, prevent overheating or overcooling of internal chips and batteries, and increase the service life of the electronic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of a passive liquid metal thermal switch;

[0034] Figure 2 It is a top view cross-section of a passive liquid metal thermal switch (a low temperature b high temperature);

[0035] Figure 3 The side cross-sectional view of a single unit of a passive liquid metal thermal switch (a low temperature b high temperature);

[0036] Figure 4 A three-dimensional schematic diagram of a single unit of a passive liquid metal thermal switch (a low temperature b high temperature);

[0037] Figure 5 It is a schematic diagram of the passive liquid metal thermal switch structure with a partition structure;

[0038] Figure 6 The top view of the passive liquid metal thermal switch with a partition structure (a low temperature b high temperature);

[0039] Figure 7 Schematic diagram of the cross section of a passive liquid metal thermal switch with a hydrophilic / hydrophobic layer;

[0040] Figure 8 Side cross-sectional view of a single unit of a hemispherical liquid-containing chamber thermal switch (a low temperature b high temperature).

[0041] Fig. 9 This is a three-dimensional schematic diagram of a semi-cylindrical liquid-containing chamber thermal switch (a low temperature b high temperature).

[0042] Description of the drawings: 101 - first cover plate, 301 - second cover plate, 201 - micro hollow layer, 202 - liquid holding cavity, 203 - liquid metal, 204 - gas, 205 - partition structure, 206 - hydrophilic / hydrophobic layer. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The described embodiments are only possible technical implementations of the present invention, not all possible implementations. Those skilled in the art can completely combine the embodiments of the present invention to obtain other embodiments without creative work, and these embodiments are also within the scope of protection of the present invention.

[0044] Embodiment 1

[0045] like Figure 1 , 2As shown in Figures 3 and 4, this embodiment provides a passive thermal switch using the wettability change of liquid metal, including liquid metal 203, a micro-hollow layer 201, a spherical liquid containing cavity 202 and a double-layer cover plate 101, 301. The spherical liquid containing cavity 202 is used to contain the liquid metal 203 in agglomerated state, and the micro-hollow layer 201 is used to spread the liquid metal 203. Since there is a certain amount of gas 204 in the micro-hollow layer 201 and the spherical liquid containing cavity 202, in fact, the action process of the passive liquid metal thermal switch is that the liquid metal 203 and the gas 204 exchange positions with each other in the micro-hollow layer 201 and the spherical liquid containing cavity 202.

[0046] The passive liquid metal thermal switch in this embodiment is characterized in that the liquid metal 203 will flow in the spherical liquid holding cavity 202 and the fine hollow layer 201 as the temperature rises or falls, so that the device can switch between low thermal resistance and high thermal resistance. The double-layer cover plates 102 and 302 have high thermal conductivity. The fine hollow layer 201 has a large spreading area, and most of the heat passes through the fine hollow layer 201 when the thermal switch is in the on state. The spherical liquid holding cavity 202 is used to store liquid metal 203 in an agglomerated state, reducing the area of ​​heat conduction and achieving heat preservation. The wettability of the liquid metal 203 is sensitive to temperature changes, and has a high thermal conductivity, making it suitable as a filling medium for a wet heat switch.

[0047] When the passive liquid metal thermal switch is heated, as the temperature rises, the wettability of the liquid metal 203 on the surface of the double-layer cover plates 102 and 302 becomes hydrophilic, and under the action of capillary force, the liquid metal 203 spreads in the fine hollow layer 201 and enters a conductive state. At this time, the thermal resistance is low, and the heat on one side of the cover plate can be dissipated in time through the conductive thermal switch; when the ambient temperature of the passive liquid metal thermal switch is low, as the temperature decreases, the wettability of the liquid metal 203 on the surface of the double-layer cover plates 102 and 302 becomes hydrophobic, and under the action of capillary force, the liquid metal 203 shrinks and aggregates in the spherical liquid holding cavity 202 and enters a heat preservation state. At this time, the thermal resistance is high, and the heat dissipation rate on the side of the cover plate close to the electronic device is slow.

[0048] Embodiment 2:

[0049] like Figure 5 , 6As shown, this embodiment provides a passive liquid metal thermal switch based on liquid wettability. Compared with the first embodiment, this embodiment adds a partition structure 205 between the liquid containing cavities 202. By setting the above partition structure, the fine hollow layer 201 is divided into multiple independent areas. Each independent area can be provided with the same or different numbers of liquid containing cavities, which can achieve more accurate control of the movement path or range of the liquid metal 203 with temperature changes, so that the structural design of the thermal switch meets the diversified heat dissipation component structure, thereby more accurately adjusting the temperature. The remaining structural features are the same as those of the first embodiment.

[0050] Embodiment three:

[0051] like Figure 7 As shown, this embodiment provides a passive liquid metal thermal switch based on liquid wettability, and a hydrophilic or hydrophobic surface 206 is provided on the inner surface of the fine hollow layer 201, and a hydrophilic surface and a hydrophobic surface can also be arranged at intervals in the fine hollow layer 201, which can be a hydrophilic or hydrophobic coating, or a hydrophilic and hydrophobic structure. The hydrophilicity or hydrophobicity of the liquid metal 203 on the hydrophilic and hydrophobic surface also changes with temperature. When hydrophilic, the liquid metal 203 spreads, the thermal switch is turned on, and heat is easily transferred; when hydrophobic, the liquid metal 203 shrinks, the thermal switch is disconnected, and heat is difficult to pass. Through the continuous or discrete changes in the hydrophilic / hydrophobic properties, the hydrophilic / hydrophobic properties can be accurately controlled, thereby controlling the flow of the liquid metal 203 in the spherical liquid holding cavity 202 and the path or filling area of ​​the fine hollow layer 201, realizing the control of the process of the liquid metal 203 and the gas exchange position inside the passive liquid metal thermal switch, avoiding the flow of the liquid metal 203 and the air blocking, and forming bubbles or inaccessible areas inside. The remaining structural features are the same as those of the first embodiment.

[0052] Embodiment 4:

[0053] This embodiment provides a passive liquid metal thermal switch based on liquid wettability, and isolation and corrosion-resistant surfaces are provided on the inner surfaces of the fine hollow layer 201 and the liquid holding cavity 202. Since the liquid metal 203 reacts with a variety of materials, more materials can be used as cover materials by providing isolation and corrosion-resistant surfaces.

[0054] Embodiment five;

[0055] like Figure 8As shown, this embodiment provides a passive liquid metal thermal switch based on liquid wettability. The structural features of this embodiment are different from those of the first embodiment in the design shape of the liquid receiving chamber 202, and the rest of the system components and connection methods are the same as those of the first embodiment. In this embodiment, the liquid receiving chamber 202 is only half of that of the first embodiment, that is, a plurality of grooves are only provided on a certain surface of the double-layer cover plate 101, 301, and the liquid metal 203 is partially or completely absorbed from the liquid receiving chamber 202 into the micro hollow layer 201 after the temperature rises.

[0056] In this embodiment, it is only necessary to set a liquid containing cavity in the first cover plate or the second cover plate to achieve the effect of heat adaptive regulation based on the change of wettability of liquid metal with temperature, thereby reducing the manufacturing cost.

[0057] Embodiment 6

[0058] like Fig. 9 As shown, this embodiment provides a passive liquid metal heat switch based on liquid wettability adaptive adjustment, wherein the shape of the liquid holding cavity 202 is semi-cylindrical, and when the liquid metal gathers, the point distribution changes to a linear distribution, and the linear spreading and contraction can be achieved through the semi-cylindrical liquid holding cavity 202. The rest of the arrangement is the same as that of the first embodiment.

[0059] Embodiment 7

[0060] This embodiment provides a passive liquid metal heat switch based on liquid wettability adaptive adjustment, wherein the liquid metal heat switch can be used at any angle, not limited to horizontal and vertical angles. According to the above liquid metal heat switch, it is not affected by the use angle during use, ensuring that the liquid metal heat switch can work normally at all angles during daily use. The rest of the arrangement is the same as that of the first embodiment.

[0061] Embodiment 8

[0062] This embodiment provides a passive liquid metal thermal switch with adaptive adjustment based on liquid wettability. It adopts the same structure as the first embodiment and is stacked in a direction perpendicular to the surface of the double-layer cover plate to form a multi-layer structure. By selecting the same / different liquid metals 203, the performance and range of the thermal switch under the insulation state can be enhanced, and the design and manufacture of the fine hollow layer 201 can be facilitated.

[0063] Embodiment 9

[0064] This embodiment provides an application of a passive liquid metal heat switch based on liquid wettability adaptive regulation in a mobile phone housing to achieve adaptive management of the mobile phone operating temperature. On the one hand, the reliability of the mobile phone is improved, making the mobile phone usable in cold or hot temperature environments; on the other hand, the safety of the mobile phone lithium-ion battery is improved.

[0065] For example, in the cold winter, the mobile phone battery may lose power due to the cold. At this time, the liquid metal thermal switch can be turned off, and the liquid metal gathers in the liquid holding cavity to achieve the effect of keeping the phone warm. When the temperature is too high, the CPU will reduce the frequency and affect the running speed. At the same time, the lithium-ion battery will also be in danger of thermal runaway due to the high temperature. At this time, the liquid metal is spread all over the fine hollow layer, and the heat can be conducted in time to achieve the purpose of timely heat dissipation. Ensure that the mobile phone maintains a normal operating temperature during normal operation.

Claims

1. Passive liquid metal thermal switch, characterized by: The invention comprises a double-layer cover plate, a micro-hollow layer located between the double-layer cover plates, a plurality of array-type liquid containing cavities formed between the double-layer cover plates, and liquid metal filled in the liquid containing cavities; the micro-hollow layer is connected to the liquid containing cavities; the cross-sectional area of ​​the micro-hollow layer is greater than the sum of the cross-sectional areas of all the liquid containing cavities; the liquid metal can flow between the micro-hollow layer and the liquid containing cavities as the temperature changes, so that the thermal switch automatically switches between the high thermal resistance state and the low thermal resistance state; Liquid metal can flow between the micro-hollow layer of the liquid metal heat switch and the liquid containing cavity according to the change of its wettability with temperature, so that the liquid metal heat switch can automatically adjust the transmission capacity of thermal energy; When the liquid metal heat switch is heated, the heat transfer capacity increases when the liquid metal flows from the liquid receiving cavity to the micro-hollow layer; when the temperature decreases, the liquid metal shrinks from the micro-hollow layer back to the liquid receiving cavity, and the heat transfer capacity decreases; The structure of the micro-hollow layer is a single-layer or multi-layer micro-channel or porous material; the passive liquid metal thermal switch realizes automatic opening and closing of the thermal switch through the wettability of the liquid metal and the capillary action of the micro-hollow layer, and realizes two forms of heat dissipation and heat preservation as the temperature changes; The entire or partial area of ​​the inner wall of the micro hollow layer and / or the liquid containing cavity is provided with a hydrophilic and / or hydrophobic surface.

2. The passive liquid metal thermal switch according to claim 1, characterized in that: The inner surface of the double-layer cover plate is uniformly or non-uniformly provided with a plurality of grooves to form the liquid containing cavity.

3. The passive liquid metal thermal switch according to claim 2, characterized in that: The liquid containing chamber is hemispherical, semi-cylindrical, spherical or cylindrical, and the liquid containing chambers are arranged in a dotted square array, a linear square array, or a distribution of dots / lines forming a pattern.

4. The passive liquid metal thermal switch according to claim 1, characterized in that: There is gas in the fine hollow layer.

5. The passive liquid metal thermal switch according to claim 1, characterized in that: The micro hollow layer is provided with a partition structure at a position between the liquid containing cavities, and the partition structure divides the micro hollow layer into a plurality of independent regions, and the number of liquid containing cavities in each independent region is the same or different.

6. The passive liquid metal thermal switch according to claim 1, characterized in that: The entire or partial area of ​​the micro-hollow layer and / or the inner wall of the liquid containing cavity is provided with an isolation surface or an anti-corrosion surface.

7. The passive liquid metal thermal switch according to claim 1, characterized in that: The passive liquid metal thermal switches are stacked in a direction perpendicular to the surface of the double-layer cover plate to form a multi-layer structure.

8. The passive liquid metal thermal switch according to any one of claims 1 to 7, characterized in that: The liquid metal is any one of single substance liquid metal gallium, gallium-indium alloy, gallium-indium-tin alloy and gallium-zinc alloy.

9. The passive liquid metal thermal switch according to any one of claims 1 to 7, characterized in that: The double-layer cover plate material is any one of metal and alloy materials, PC thermal conductive plastic, ABS thermal conductive plastic, plastic-coated aluminum thermal conductive material, and shaped composite phase change material.

10. An electronic device, characterized in that: It comprises a heating element, on which the passive liquid metal thermal switch according to any one of claims 1 to 9 is arranged.

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