Phase change heat dissipation device

Abstract

The present invention discloses a phase change heat dissipation device including a phase change unit containing a phase change heat exchange medium, wherein the phase change heat exchange medium is configured so that the internal pressure of the phase change unit is greater than 0.15 MPa when the phase change heat dissipation device is in operation. The phase change heat dissipation device of the present invention operates at a temperature range of 30-80°C, and the internal pressure is much greater than standard atmospheric pressure, creating a positive pressure non-vacuum environment. This results in a large heat flux from the heat source, a high absolute pressure in the evaporation section of the phase change unit, and large relative pressure differences between different parts of the phase change unit under the same temperature difference. The pressure difference drives more phase change medium, thereby enhancing the heat exchange capacity, improving the fluidity of the internal phase change heat exchange medium, and enhancing the heat flux of heat transfer, thereby facilitating efficient heat dissipation.

Description

[Technical field]

[0001] The present invention relates to the technical field of phase change heat dissipation devices, and in particular to a phase change heat dissipation device for electronic devices. [Background technology]

[0002] Phase change heat dissipation is an efficient heat dissipation method. Its principle is that a phase change heat exchange medium boils and vaporizes at a certain temperature, absorbing heat, and then the vaporized gas condenses and liquefies at another location to dissipate heat, thereby transferring heat. Its heat transfer effect is high and it is widely used.

[0003] At present, phase change radiators generally use heat pipes to perform phase change heat dissipation, and compared with other conventional heat dissipation methods, heat pipe heat dissipation has a higher heat transfer efficiency and a higher heat dissipation effect. A typical heat pipe radiator is mainly composed of three main parts: a heat pipe, a heat dissipation fin, and a heat conduction base. Among them, the heat pipe as a phase change unit transfers heat by phase change, the heat conduction base connects the heat source and the radiator, the heat source transfers heat to the heat pipe through the heat conduction base, and the heat dissipation fin transfers the heat of the heat pipe and the phase change heat exchange medium in the heat pipe to the outside world. One end (evaporation part) of the heat pipe is fitted or welded to the heat conduction base, and the other end (condensation part) is connected to the heat dissipation fin.

[0004] Currently, most of the common phase change radiators use vacuum suction to lower the boiling point of the phase change heat exchange medium so that the phase change heat exchange medium can evaporate at the appropriate temperature. Conventional heat pipes use deionized water or ethanol as the working fluid, so a certain negative pressure must be maintained to evaporate at the operating point.

[0005] Combined with the fact that the heat pipe itself is tubular, the number of heat pipes that can be arranged in one heat pipe radiator is limited, so the area of ​​direct contact between the heat pipe and the heat source is small, which results in an obstacle to the transfer of heat from the heat source to the phase change unit (heat pipe), resulting in low heat transfer efficiency, severely limiting the heat dissipation performance, and causing local high temperatures at the base. In addition, the heat dissipation method of the heat pipe is one-dimensional, such as conducting heat in a linear manner, so the heat pipe itself does not have the optimal heat dissipation capacity or heat dissipation effect, and the processing cost of the heat pipe radiator is high. Most phase change radiators operate in a vacuum environment inside, which limits the flow of the internal phase change heat exchange medium, which is unfavorable to heat dissipation.

[0006] In addition, most of the current heat pipes use red copper as the shell material, while aluminum alloy is used as the base material. Usually, the gap between the heat pipe and the base is filled by low-temperature tin brazing or gluing, which generates a certain thermal resistance and is unfavorable to heat transfer. The defects of low-temperature tin brazing include that the entire radiator needs to be surface-treated, such as nickel plating or copper plating, before welding, which increases the cost and causes environmental pollution due to welding and surface treatment. Soldering makes it difficult to ensure that the flat surface of the heat pipe and the aluminum alloy base is completely filled and does not cause local porosity. Meanwhile, the heat pipe is installed under the power device, and the heat flux is large, so if there is a porosity, the temperature of the heat source device will increase locally, resulting in device wear. Heat pipe radiators have high processing costs and cause environmental pollution.

[0007] Therefore, the conventional phase change radiator has problems such as large thermal resistance of heat transfer, non-uniform heat transfer, high manufacturing cost, and low heat exchange efficiency. Summary of the Invention [Problem to be solved by the invention]

[0008] To solve the above problems of the prior art, the present invention provides an electronic device phase change heat dissipation device to improve heat transfer efficiency and promote heat diffusion. [Means for solving the problem]

[0009] In order to achieve the above object, the technical solution of the electronic device phase change heat dissipation device of the present invention is specifically as follows:

[0010] A phase change heat dissipation device including a phase change unit having a phase change heat exchange medium disposed therein, The phase change heat exchange medium provided in the phase change unit is configured so that the air pressure inside the phase change unit is greater than 0.15 MPa when the phase change heat dissipation device is in an operating state.

[0011] Furthermore, the phase change heat exchange medium provided in the phase change unit is one or more of R134a, R142b, R114, R124, R1233Zd(E), R1234Ze(Z), R1234Ze(E), R600a, RC318, RE245cb2, R22, R32, R407C, and R410A.

[0012] Furthermore, the phase change unit includes an evaporation section and a condensation section, has an evaporation chamber inside the evaporation section and a condensation chamber inside the condensation section, the evaporation chamber and the condensation chamber are connected, and the phase change heat exchange medium in the evaporation chamber absorbs heat from the heat source and transfers it to the condensation chamber, and the condensation chamber cools the heat source by releasing heat to the outside.

[0013] Furthermore, the evaporation chamber may be a planar or curved cavity.

[0014] Furthermore, the condensation section includes a plurality of condensation branch plates, and the condensation chamber is a planar cavity corresponding to the inside of the condensation branch plates; or The condensation section includes a plurality of condensation branch pipes, and the condensation chamber is a cylindrical cavity corresponding to the interior of the condensation branch pipes; or The condensation section includes a plurality of condensation taper tubes, and the condensation chamber is a conical cavity corresponding to the interior of the condensation taper tubes.

[0015] Furthermore, the condenser section is connected to the evaporator section directly or via a pipe.

[0016] Furthermore, the inner wall of the condenser is provided with a condensation enhancing structure, and the outer wall of the condenser is provided with fins or ribs to increase the condensation area.

[0017] Furthermore, a plurality of ribs, protrusions or fins are provided inside the evaporator and condenser, thereby improving the pressure resistance.

[0018] Further, the outer wall of the evaporation section is provided in contact with a heat source.

[0019] Furthermore, the evaporator has a contact heat absorption surface on its outer surface, the heat source has a heat source surface, the contact heat absorption surface of the evaporator and the heat source surface of the heat source are in contact with each other, and both the heat source surface and the contact heat absorption surface are flat. Effect of the Invention

[0020] The phase change heat dissipation device of the present invention has the following advantages: 1) The evaporator part of the phase change unit is in direct contact with the heat source, so the evaporator part can be in sufficient contact with the heat source, the heat transfer area is large, the heat transfer effect is high, and when the heat flux of the heat source is large, the phase change medium in direct contact with the bottom of the evaporation chamber will be vaporized, and the local gas pressure will increase, resulting in a pressure difference between the area of ​​the highest heat flux where the evaporation chamber and the heat source are in contact and other areas. In this way, the heat of the evaporator part of the phase change unit is quickly diffused, and the temperature difference of the entire evaporator part is small. 2) Since the phase change unit has a three-dimensional heat dissipation structure, once the phase change heat exchange medium is vaporized, it can quickly diffuse to any low-pressure area of ​​the phase change unit, so that the temperature of the phase change unit is uniform, the heat transfer efficiency is high, and the heat transfer is uniform. 3) When the phase change heat dissipation device is working, the working temperature range is 30~80℃, and the internal pressure is much higher than the standard atmospheric pressure, resulting in a positive pressure non-vacuum environment. The heat flux of the heat source is large, the absolute pressure of the evaporation part of the phase change device is high, and the relative pressure difference is large in different parts of the phase change device under the same temperature difference condition, so that more phase change medium is driven by the pressure difference, which enhances the heat exchange capacity, improves the fluidity of the internal phase change heat exchange medium, improves the heat flux of heat transfer, and facilitates efficient heat dissipation. 4) When the phase change heat dissipation device is in operation, the internal absolute pressure is large, and the pressure that the evaporator and condenser receive is large. By providing multiple ribs, protrusions or fins inside the evaporator and condenser, the pressure resistance is improved. 5) Inside the phase change unit, a structure is brazed or sintered to enhance boiling and evaporation heat exchange, so that the phase change heat exchange medium can carry out boiling heat transfer more efficiently, and the heat diffusion is more uniform and rapid, and the heat transfer is also more efficient due to the increased heat exchange area.

[0021] Furthermore, the manufacture of the phase change heat dissipation device of the present invention does not require surface treatment processes such as copper plating or nickel plating, and the phase change structure and condensation fins of the heat dissipation device are directly welded together by high-temperature brazing, and the heat source (e.g., the power device CPU) and the phase change heat dissipation device are in contact with each other, and the gaps are filled by low-temperature soldering, thereby avoiding the occurrence of gaps and significantly improving the heat transfer limit of the phase change heat dissipation device of the present invention (far greater than 200W).

[0022] The present invention is applicable to heat dissipation in power electronic devices such as chips, resistors, capacitors, inductors, storage media, light sources, and battery packs. [Brief description of the drawings]

[0023] [Figure 1a] FIG. 2 is a perspective view of a phase change heat dissipation device according to a first embodiment of the present invention, in which a number of condensation branch plates are not connected to each other. [Figure 1b] FIG. 1b is a cross-sectional view of the phase change heat dissipation device of FIG. 1a, in which a plurality of condensation branch plates are connected to each other through a condensation top plate; [Diagram 2] FIG. 2 is a perspective view of a phase change heat dissipation device according to a second embodiment of the present invention. [Figure 3a] FIG. 11 is a perspective view of a phase change heat dissipation device according to a third embodiment of the present invention. [Figure 3b] FIG. 3b is a cross-sectional view of the phase change heat dissipation device of FIG. 3a. [Figure 4a] FIG. 11 is a perspective view of a phase change heat dissipation device according to a fourth embodiment of the present invention. [Figure 4b] FIG. 4b is a cross-sectional view of the phase change heat dissipation device of FIG. 4a. [Figure 5a] FIG. 5 is a perspective view of the fifth embodiment of the phase change heat dissipation device of the present invention, in which the evaporator section and the condenser section are installed separately and communicated through a pipeline, the evaporator section has a hollow rectangular cavity, and the condenser section includes a plurality of condenser branch plates. [Figure 5b] FIG. 5b is a cross-sectional view of the phase change heat dissipation device of FIG. 5a. [Figure 6a] FIG. 6 is a perspective view of the sixth embodiment of the phase change heat dissipation device of the present invention, in which the evaporator section and the condenser section are installed separately and communicated through a pipeline, the evaporator section is a hollow rectangular cavity, the condenser section includes a plurality of condensation branch pipes, and the condensation branch pipes have a plurality of cylindrical cavities. [Figure 6b] FIG. 6b is a cross-sectional view of the phase change heat dissipation device of FIG. 6a. [Figure 7] 1 shows a schematic diagram of the flow of the phase change heat exchange medium of the present invention in a phase change unit. [Figure 8] 1 shows a schematic diagram of the flow of the phase change heat exchange medium of the present invention in a phase change unit. [Figure 9] 1 shows a schematic diagram of the enhanced heat exchange structure of a phase change heat dissipation device. [Figure 10] 1 shows a schematic diagram of the enhanced heat exchange structure of a phase change heat dissipation device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] In order to make the objectives, structure and function of the present invention more understandable, the phase change heat dissipation device for electronic devices of the present invention will be described in further detail below with reference to the drawings.

[0025] The definitions of terms relevant to the present invention are as follows:

[0026] Boiling heat transfer is a heat transfer process in which heat is transferred from a wall to a liquid, causing the liquid to boil and vaporize.

[0027] The vaporizing core is the carrier that initiates liquid boiling.

[0028] Thermal conductivity is the rate at which the temperature of the inside of an object changes over a distance of 1 m and an area of ​​1 m. 2 If two parallel planes are taken that are perpendicular to the direction of heat conduction, and the temperature difference between the two planes is 1K, the heat that is conducted from one plane to the other in one second is defined as the thermal conductivity of this material, and its unit is watt meters. -1 ·Kelvin meters -1 (W m -1 ·K -1 ).

[0029] Thermal resistance is defined as the ratio between the temperature difference across an object and the power of the heat source when heat is transferred across the object, and has units of Kelvin meters per watt (K / W) or degrees Celsius per watt (°C / W).

[0030] The heat transfer coefficient is the heat transferred through a unit area per unit time when the temperature difference between the air on both sides of the surrounding structure is 1°C (K or °C) under stable heat transfer conditions, and is expressed in watts / (m 2 · °C) (W / ·K, where K can be replaced by °C) and reflects the intensity of the heat transfer process.

[0031] Heat flux is the amount of heat transferred per unit area per unit time, and is expressed as q=Q / (S * t)-Q is heat, t is time, S is cross-sectional area, and the unit of heat flux is J / (m 2 ·s).

[0032] Transition boiling occurs when, as the heat flux increases, steam ejected from a large vaporization core becomes a steam beam, and as the steam flow obstructs the liquid being replenished to the heat transfer surface, the liquid on the heat transfer surface dries out in a short period of time, resulting in a sudden rise in the temperature of the heat transfer surface.

[0033] Positive pressure is defined as the pressure inside the phase change unit of the radiator being 1.5 times or more the standard atmospheric pressure (greater than 0.15 MPa) when the temperature of the contact point between the radiator and the heat source becomes stable.

[0034] Slightly positive pressure: When the temperature of the contact part between the radiator and the heat source becomes stable, the pressure inside the phase change unit of the radiator is 0.1MPa to 0.15MPa. For example, when ethanol is used as a phase change heat exchange medium, the air pressure inside the phase change unit is slightly positive pressure.

[0035] Negative pressure: When the temperature of the contact part between the radiator and the heat source becomes stable, if the pressure inside the phase change unit of the radiator is less than 0.1MPa, it is negative pressure. For example, when using water as the phase change heat exchange medium, the pressure inside the phase change unit must be negative pressure, otherwise the phase change heat exchange medium cannot start and the radiator will break down.

[0036] As shown in Figures 1a to 6b, the phase change heat dissipation device 10 of the present invention includes an evaporator 11, a condenser 12, and a phase change heat exchange medium 20 provided in the evaporator 11 or the condenser 12, and both the evaporator 11 and the condenser 12 form a three-dimensional heat exchange structure. When the phase change heat dissipation device 10 is in an operating state, the internal operating pressure is greater than 0.15 MPa and the device is in a positive pressure state. The evaporator 11 and the condenser 12 may be directly connected to each other (see Figures 1a to 4b), or may be separate structures connected via a pipe (see Figures 5a to 6b).

[0037] In the embodiment shown in Figures 5a to 6b, the condensation part 12 may be arranged horizontally or vertically, and the structure and arrangement direction may be changed according to the needs of the structural design of the system including the CPU board. The heat source 30 is directly attached to the evaporation part 11 of the phase change component, and the heat is directly transferred to the phase change heat exchange medium 20 through the thin wall of the evaporation part 11, and the phase change heat exchange medium 20 absorbs heat and undergoes phase change, which creates a pressure difference between the evaporation part 11 and the condensation part 12 in the phase change heat dissipation device 10, thereby making the phase change heat exchange medium 20 flow to the condensation part 12, and the phase change medium 20 condenses in the condensation part 12 and returns to the evaporation part 11 through gravity and capillary force, and circulates in this manner.

[0038] As shown in Figures 1a and 1b, the phase change heat dissipation device 10 of the present invention includes a phase change unit, which is an airtight structure having a cavity therein, and which accommodates a phase change heat exchange medium 20 inside the phase change unit. The internal cavity of the phase change unit has a structure that is generally connected, and the phase change heat exchange medium 20 can circulate throughout the entire internal cavity of the phase change unit.

[0039] The phase change unit has an evaporator 11 and a condenser 12, an evaporator chamber inside the evaporator 11, and a condenser chamber inside the condenser 12, the evaporator chamber of the evaporator 11 communicates with the condenser chamber of the condenser 12, the evaporator chamber and the condenser chamber form an internal cavity of the phase change unit, and the condenser 12 is connected to the condenser fins. The phase change heat exchange medium 20 in the evaporator chamber absorbs heat from the heat source 30 and vaporizes, flows into the condenser chamber to be cooled and liquefied, and the condenser chamber releases heat to the outside through the condenser fins. In this way, the phase change heat dissipation device 10 transfers the heat from the heat source 30 to the air or other gaseous cooling medium to achieve the effect of dissipating and cooling the heat source.

[0040] The evaporator section 11 of the phase change unit is a flat or curved plate-like body having a cavity therein, and has a flat or curved evaporation chamber inside the evaporator section 11, and the flat or curved cavity inside the evaporator section 11 is connected to a condensation chamber inside the condenser section 12.

[0041] The condensation section 12 includes a plurality of condensation branch plates having a cavity therein, the interior of the condensation branch plate being a planar condensation chamber, the plurality of condensation branch plates being connected to the evaporation section 11, the planar condensation chamber inside the condensation branch plate being connected to the planar evaporation chamber or the curved evaporation chamber inside the evaporation section 11. The plurality of condensation branch plates are preferably arranged in parallel, the condensation branch plates being connected vertically to the evaporation section 11, the condensation fins being connected to the outside of the condensation branch plates, and the heat inside the condensation branch plates is released to the outside through the condensation fins. The evaporation section 11 is not limited to a plate-like structure, and may be another columnar structure, as long as the lower bottom surface is flat.

[0042] Furthermore, the inner wall of the condenser section 12 is provided with a condensation-enhancing structure, which may be a capillary structure distributed on the inner wall of the condenser section 12, and the capillary structure is a broad bean-shaped columnar, cylindrical or conical structure, which has a capillary effect and allows the vaporized phase-change heat exchange medium 20 to flow more quickly and uniformly along the condensation chamber, and is also advantageous for the condensed phase-change heat exchange medium 20 to flow back quickly into the evaporation chamber. Furthermore, such a capillary structure increases the heat exchange area of ​​the condensation chamber itself, and accelerates the heat transfer rate.

[0043] As shown in FIG. 2a-2b, the condensation section 12 further includes a condensation top plate 121, and has a flat condensation chamber or a curved condensation chamber inside the condensation top plate 121, and the condensation chamber inside the condensation top plate 121 communicates with the condensation chamber inside the condensation branch plate, and the condensation section 12 is comb-shaped as a whole. The phase change heat exchange medium 20 absorbs heat in the evaporation chamber of the evaporation section 11, dissipates heat through the condensation branch plate and the condensation top plate 121 of the condensation section 12, and dissipates heat from the heat source 30 by circulating between the evaporation chamber of the evaporation section 11 and the condensation branch plate and the condensation chamber inside the condensation top plate 121. The condensation top plate 121 may be integrally molded with the condensation branch plate. The evaporation section 11 and the condensation section 12 of the phase change unit are also preferably integrally molded.

[0044] As shown in Figures 3a-3b, in this embodiment, the condensation branch plate of the condensation section 12 takes another form, that is, the condensation section 12 includes a plurality of cylindrical condensation branch pipes, and the condensation chamber is a cylindrical cavity corresponding to the interior of the condensation branch pipes. As shown in Figures 4a-4b, the condensation section 12 may further include a plurality of condensation taper pipes, and the condensation chamber is a conical cavity corresponding to the interior of the condensation taper pipes.

[0045] As shown in Figures 5a, 5b, 6a and 6b, the condensation chamber of the condenser section 12 is connected to the evaporator section 11 through a pipe rather than directly, so that the condenser section 12 is rationally arranged according to the internal structure of the heat source 30 system.

[0046] As a result, the evaporator section 11 of the phase change unit is directly connected to the condenser section 12, and the evaporator section 11 at one end of the phase change unit is directly connected to the condenser section 12 at the other end of the phase change unit. During evaporation and condensation by the phase change heat exchange medium 20 inside the phase change unit, heat is diffused three-dimensionally in the horizontal and vertical directions from one end of the phase change unit to the other end of the phase change unit, thereby improving the temperature uniformity throughout the entire internal cavity of the phase change unit, particularly the condensation chamber of the condenser section 12.

[0047] The evaporation section 11 is in direct contact with the heat source 30, that is, the surface of the evaporation section 11 (the outer surface of the evaporation chamber) is in direct contact with the heat source 30, and the surface of the evaporation section 11 functions as a substitute for the substrate of a conventional heat dissipation device, thereby improving the heat transfer efficiency between the heat source 30 and the evaporation section 11. The evaporation section 11 is preferably a flat plate-like body having an internal cavity, and has a contact heat absorption surface on one side of the evaporation section 11, the heat source 30 has a flat heat source surface, and the contact heat absorption surface of the evaporation section 11 is provided in contact with the heat source surface of the heat source 30.

[0048] The area of ​​the heat source surface of the heat source 30 is smaller than the area of ​​the contact heat absorption surface of the evaporator 11 of the phase change unit, and the internal phase change heat exchange medium 20 undergoes phase change and flows, so that heat can be rapidly transferred from the heat source 30 to the evaporator 11 of the phase change unit along a two-dimensional direction, and the temperature inside the evaporator chamber of the phase change unit can be made uniform. The vaporized phase change heat exchange medium 20 enters the condensation branch plate and flows along a third direction, which is perpendicular to the evaporator 11 of the flat plate-like body, that is, perpendicular to the two-dimensional heat dissipation direction inside the evaporator 11.

[0049] A plurality of ribs, protrusions or fins are provided inside the evaporator 11 and / or the condenser 12 to improve pressure resistance.

[0050] The phase change unit and the condensation fins may be made of copper, aluminum, copper alloy, aluminum alloy, magnesium alloy, stainless steel material, for example, the phase change unit and the condensation fins are all made of copper or aluminum material, and the phase change unit and the condensation fins are preferably connected by brazing to reduce the contact thermal resistance of the phase change unit and the condensation fins and reduce the temperature difference between the condensation fins and the heat source 30. After the heat source 30 (e.g., the power device CPU) and the phase change heat dissipation device 10 (e.g., the evaporation part 11) are contacted and connected, the gaps are filled by low-temperature soldering to prevent the occurrence of gaps.

[0051] By welding the cooling fins and the outer wall of the condensation branch plate together, the pressure resistance of the condensation branch plate is increased, and when the radiator is operating, the internal operating pressure of the condensation section 12 and the evaporation section 11 increases. When this pressure increases to 1 MPa or more, the cross structure formed by welding the cooling fins and the condensation branch plate ensures the strength of the condensation section 12 required for operation, preventing deformation of the condensation section 12 and ensuring normal operation of the radiator.

[0052] As shown in Figures 9-10, other enhanced heat exchange structures may be used instead of condensation fins, and the enhanced heat exchange structure may be a protrusion or trench (Figure 9) formed on the outer surface of the condenser section 12 or the evaporator section 11, or a porous structure (Figure 10) formed on the surface of the condenser section 12 or the evaporator section 11 by sintering. The enhanced heat exchange structure allows the phase change heat exchange medium 20 to transfer boiling heat more efficiently, and the heat diffusion becomes more uniform and rapid. The increased heat exchange area also makes the heat transfer with the outside more efficient. The enhanced heat exchange structure can be determined according to the power density and manufacturing cost of the heat source 30.

[0053] As shown in Figures 7 and 8, the circulating flow of the phase change heat exchange medium 20 in the phase change unit is shown. After absorbing heat from the heat source 30, the phase change heat exchange medium 20 in the evaporation section 11 diffuses along a two-dimensional plane in the evaporation chamber inside the evaporation section 11, then vaporizes and flows to a condensation branch plate perpendicular to the condensation section 12 of the evaporation section 11, and further flows into the condensation top plate 121. Condensation fins are connected to the outer surfaces of the condensation branch plate and the condensation top plate 121, and the heat contained in the phase change heat exchange medium 20 in the condensation branch plate and the condensation top plate 121 diffuses to the outside through the condensation fins, thereby obtaining a more advantageous heat dissipation effect and performance.

[0054] In the phase change heat dissipation device of the present invention, the evaporation chamber of the evaporation section is a thin-walled cavity with a flat or curved surface, a capillary structure is provided within the evaporation section to enhance boiling heat transfer, the condensation section includes a plurality of hollow condensation branch plates, condensation branch pipes or condensation taper pipes, a structure is provided inside the hollow branch plate, hollow cylinder or hollow cone to enhance condensation heat exchange, and fins or ribs that can increase the area of ​​condensation heat exchange are connected to the outside of the condensation section, providing good heat exchange performance.

[0055] In the non-operating state, the environmental temperature of the radiator is lower than the boiling point of the phase-change medium, the pressure at each part of the internal cavity of the phase-change unit is the same, and the internal pressure can be in a standard atmospheric pressure or negative pressure state. When the phase-change unit is in the operating state, the environmental temperature is higher than the boiling point of the phase-change medium, the temperature at each point inside the phase-change unit is different, and the pressure is different, and the heat exchange inside the phase-change unit is achieved by the pressure difference caused by the difference in temperature of the phase-change unit, and the phase-change heat exchange medium 20 in the evaporator 11 is transported to the condenser 12. The transport power of the phase-change heat exchange medium 20 from the evaporator 11 to the condenser 12 is the pressure difference at different temperatures of the phase-change heat exchange medium 20. Therefore, the larger the pressure difference, the higher the medium transport capacity. In the phase change unit, the transfer capacity from the evaporator section 11 to the condenser section 12 is mainly determined by the pressure difference of the phase change heat exchange medium 20 between the evaporator section 11 and the condenser section 12, the latent heat of vaporization of the phase change heat exchange medium 20 and the density of the phase change heat exchange medium 20.

[0056] In the prior art, commonly used phase change heat exchange media 20 include water, methanol, ethanol and acetone, and in working state, these conventional phase change heat exchange media 20 are under negative pressure or slight positive pressure.

[0057] When using the above phase change heat exchange medium 20, the working pressure is all negative pressure or slight positive pressure, that is, the atmospheric pressure is less than 0.15 MPa. Meanwhile, the heat generating power of electronic devices is becoming increasingly larger at present, and the heat generating power of a normal CPU or GPU is greater than 200 W and the power density is 60000 J / m 2·s. When the surface temperature of the radiator is 60℃, the maximum heat transfer capacity of the condenser 12 of the copper water heat pipe with Φ6mm×150mm is only 35W. Only four can be placed in the space of a commonly used CPU with a size of 45mm×69mm, so the maximum heat transfer capacity of the copper water heat pipe is only about 140W, and the remaining heat needs to be transferred through the bottom of the radiator. By using ethanol, methanol, and acetone as the phase change heat exchange medium 20, the pressure difference increases and the volume flow rate to be transferred increases, but at the same volume flow rate, the latent heat of vaporization of deionized water is much higher than that of ethanol, methanol, acetone, etc., so that in the case of low heat flux, under the same temperature difference, the heat transfer capacity of deionized water is higher than that of ethanol, methanol, acetone, etc. However, due to the increase in heat flux and the limitation due to the volume of the phase change heat dissipation device, the heat transfer capacity of the conventional copper water heat pipe cannot meet the requirements of high power heat dissipation of electronic devices.

[0058] For the heat source 30 with a size of 42mm×69mm, the power of the heat source 30 is frequency converted and adjusted, the condenser section 12 is liquid cooled, the amount of liquid is provided by the liquid cooling test device, the supply liquid temperature is maintained at 35°C, and the temperature of the heat source 30 is controlled at 40°C. Various phase change heat exchange media 20 are used to test the internal working pressure and heat generating power of the phase change unit, and the test results are shown in Table 1.

[0059] Heat flux test results for various phase change heat exchange media 20 are as follows:

[0060] [Table 1]

[0061] Of the heat exchange media, R134a is tetrafluoroethane (CF3CH2F), R114 is dichlorotetrafluoroethane (CClF2CClF2), R124 is tetrafluorochloroethane (CHClFCF3), R125 is pentafluoroethane (CHF2CF3), R1233Zd(E) or R1234Ze(Z) or R1234Ze(E) are all transchlorotrifluoropropene (CF3CH=CHCl), R600a is isobutane (CH(CH3)3), RC318 is octafluorocyclobutane (cyclo-C4F8), R245fa or R245ca are all pentafluoropropane (CHF2CF2CH2F), R32 is trifluoromethane (CH2F2), and R22 is chlorodifluoromethane (CHC1F2).

[0062] Example 1: For the heat source 30 with a size of 30mm x 45mm, the power of the heat source 30 is adjusted by frequency conversion, the condenser section 12 is cooled by air, the air volume is provided by a test wind tunnel, the inlet temperature is 25°C, the outlet temperature is 50°C, and the temperature of the heat source 30 is controlled at 60°C. Various phase change heat exchange media 20 are used to test the internal working pressure and heat generation power of the phase change unit, and the test results are shown in Table 2.

[0063] [Table 2]

[0064] As can be seen from the data in Table 2, the present invention uses a phase change heat exchange medium 20 with a boiling point of less than 30°C at standard atmospheric pressure, and the pressure difference in the phase change unit is increased, so the transmission capacity of the phase change unit is greatly increased. For a CPU with a size of 45mm x 69mm, in a radiator with the same volume, when using phase change heat exchange media 20 such as R134a, R142b, R114, R124, R1233Zd(E), R1234Ze(Z), R1234Ze(E), R600a, RC318, and RE245cb2, the transmission capacity is all significantly improved (much greater than 200W).

[0065] Thus, by providing the phase change unit with the above phase change heat exchange media, i.e., R134a, R142b, R114, R124, R1233Zd(E), R1234Ze(Z), R1234Ze(E), R600a, RC318, RE245cb2, etc., or a combination thereof, when the phase change heat dissipation device is in an operating state, the air pressure inside the phase change unit is greater than 0.15 MPa, and the above phase change heat exchange media are commercially available.

[0066] It can be seen from the test data that the heat transfer capacity of the phase change unit is positively correlated with the internal air pressure of the phase change unit, and the higher the pressure, the greater the heat exchange power.

[0067] The present invention is applicable to heat dissipation in power electronic devices such as chips, resistors, capacitors, inductors, storage media, light sources, and battery packs.

[0068] Although the present invention has been described with reference to several embodiments, those skilled in the art will appreciate that various changes and equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, the features and embodiments may be modified to suit particular situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be included within the scope of the present invention.

Claims

1. A phase change heat dissipation device including a phase change unit having a phase change heat exchange medium disposed therein, The phase change heat exchange medium provided in the phase change unit is configured such that the air pressure inside the phase change unit is greater than 0.15 MPa when the phase change heat dissipation device is in an operating state; the phase change unit includes an evaporator section and a condenser section, the evaporator section has an evaporation chamber inside, the condenser section has a condensation chamber inside, the outer wall of the evaporator section is provided in contact with a heat source so that the phase change heat exchange medium in the evaporation chamber can absorb heat from the heat source, the evaporation chamber and the condensation chamber are connected to each other so that the phase change heat exchange medium in the evaporation chamber can transfer the heat to the condensation chamber, and the condensation chamber is configured to cool the heat source by releasing heat to the outside, The evaporation chamber is a planar or curved cavity, and the phase change heat dissipation device further comprises an enhanced heat exchange structure, the enhanced heat exchange structure being a protrusion or trench formed on the outer surface of the evaporation section.

2. The phase change heat dissipation device according to claim 1, characterized in that the phase change heat exchange medium provided in the phase change unit is one or more of the following: R134a, R142b, R114, R124, R1233Zd(E), R1234Ze(Z), R1234Ze(E), R600a, RC318, RE245cb2, R22, R32, R407C, R410A.

3. The condensation section includes a plurality of condensation branch plates, and the condensation chamber is a planar cavity provided inside the condensation branch plates; or The condensation section includes a plurality of condensation branches, and the condensation chamber is a cylindrical cavity provided inside the condensation branches, or 2. The phase change heat dissipation device according to claim 1, wherein the condenser section includes a plurality of condensation taper tubes, and the condensation chamber is a conical cavity provided inside the condensation taper tubes.

4. 2. The phase change heat dissipation device according to claim 1, wherein the condenser is connected to the evaporator directly or through a pipe.

5. 2. The phase change heat dissipation device as claimed in claim 1, wherein the inner wall of the condensation section is provided with a condensation strengthening structure, and the outer wall of the condensation section is provided with fins or ribs to increase the condensation area.

6. The phase change heat dissipation device according to claim 1 , wherein a plurality of ribs, protrusions or fins are provided inside the evaporator and the condenser to improve pressure resistance.

7. The phase change heat dissipation device of claim 1, characterized in that the evaporator has a contact heat absorption surface on its outer surface, the heat source has a heat source surface, the contact heat absorption surface of the evaporator and the heat source surface of the heat source are in contact, and the heat source surface and the contact heat absorption surface are both flat surfaces.

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