A gallium heat pipe and heat exchange device for a reactor

Abstract

The present invention discloses a gallium heat pipe and a heat exchange device for a reactor. The gallium heat pipe includes a pipe body. One end of the pipe body is a condensation section, the other end of the pipe body is an evaporation section, and there is an adiabatic section between the condensation section and the evaporation section. It is characterized in that a wick is arranged in the pipe body, and gallium and its related working medium are filled in the pipe body and circulate in the pipe body. The gallium heat pipe of the present invention uses liquid metal gallium as the basic working medium. Gallium is in a liquid state at 29.76 °C, and liquid gallium has a wide temperature range and good thermal stability. The present invention can be applied to both medium and low temperature systems and high temperature systems. The implementation scope of the present invention is extensive, simple, convenient and efficient. The gallium heat pipe is particularly suitable for mobile small reactors and can be applied to a wide range of fields such as integrated energy systems, space nuclear reactors, cooling, deep sea, and civil-military integration.

Description

Technical Field

[0001] The present invention belongs to the energy field including nuclear energy and the mechanical equipment field, and particularly relates to a gallium heat pipe with high heat transfer efficiency. Background Art

[0002] Since Gaugler proposed the working principle of the heat pipe, the heat pipe has developed over several decades and various types have been derived. However, from the most basic perspective, the heat pipe is still an efficient heat transfer element that combines boiling and condensation organically. During these decades of rapid development of the heat pipe, various working conditions have promoted in-depth research on the heat pipe principle and the design and development of new structures, and different types of heat pipes such as thermosyphons, reciprocating heat pipes, pulsating heat pipes, loop heat pipes, rotating heat pipes, micro heat pipes, variable-conductance heat pipes, and high-temperature heat pipes have been derived.

[0003] Heat pipes are classified into low-temperature heat pipes (-270°C to 0°C), normal-temperature heat pipes (0°C to 200°C), medium-temperature heat pipes (200°C to 1000°C), and high-temperature heat pipes (above 1000°C) according to temperature. Since Grower et al. successfully developed high-temperature heat pipes in 1963, a large number of scientific researchers have engaged in the research of high-temperature heat pipes. In recent decades, numerous scientific researchers have conducted a large number of experimental and theoretical studies on high-temperature heat pipes, making its system gradually perfect and being widely used in the fields of aerospace, energy, electronics, and chemical engineering. The working medium of high-temperature heat pipes is mainly alkaline metals such as lithium, sodium, and potassium. Therefore, high-temperature heat pipes are also called alkali metal heat pipes. However, gallium has not been used as the working medium.

[0004] Gallium turns into a silvery-white liquid at 29.76°C. Liquid gallium is very easy to supercool, that is, it can be cooled to 0°C without solidifying, and pure liquid gallium has a significant tendency to supercool. Its boiling point is very high, and it has a very low vapor pressure at about 1500°C. Pure gallium and low-melting alloys can be used as heat exchange media for nuclear reactions. Although the unique properties of gallium may be applied in many aspects, its current industrial applications are still very few.

[0005] It has applications in the computer field such as CPU heat dissipation. However, whether it is a desktop computer or a laptop, generally speaking, the normal working temperature range is not higher than 85°C, which belongs to the category of normal-temperature heat exchange. Moreover, most of these gallium media are used in the computer field and are non-heat pipe heat exchange forms; some multi-media heat pipes with liquid metals such as mercury, zinc, and gallium are used in the range of 1800°C - 2300°C, and the temperature is too high, which is not suitable for the characteristics of the neutron physics and chemical environment in the reactor and is not applicable to the nuclear energy field including small reactors.

[0006] Heat transfer in nuclear reactors is complex. The working process of a conventional heat pipe only involves liquid-vapor phase change and its reverse phase change, and the heat load it receives is often constant. However, the working temperature range faced in heat pipe applications is very wide. Especially in a complex alternating high heat flux density heat load field, its working process not only includes all the phase change processes of the above-mentioned ordinary heat pipes, but often also includes solid-liquid phase change and its reverse phase change, which is much more complex than the working process of ordinary heat pipes. Gallium heat pipe small reactors have broad application prospects in aspects such as space nuclear reactor cooling, remote areas, and deep sea. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to propose a gallium heat pipe and a heat exchange device that use gallium as a base working fluid to increase the heat exchange capacity of the heat pipe.

[0008] Gallium is a liquid at 30 °C, and its liquid range is relatively wide, which can be used for normal temperature applications. The disadvantage is that its boiling point is relatively high, making it not easy to achieve evaporation at normal temperature. On the one hand, the present invention controls the vacuum degree, and on the other hand, adds nanoparticles and another working fluid. Due to the sharp reduction in the size of the nanoparticles, the boiling point drops sharply, and it can also play a role in enhancing heat exchange; the other working fluid can be a low-boiling-point working fluid or an easily vaporizable working fluid. Adding a low-boiling-point working fluid reduces the average boiling point. An easily vaporizable working fluid, such as Freon, water, or other working fluids, is used as the mixed working fluid for heat exchange in the heat pipe. Overall and better utilize gallium as an efficient heat-conducting and flowing medium to transfer heat.

[0009] To solve the above technical problems, the technical solution adopted by the present invention is:

[0010] A gallium heat pipe for a reactor includes a pipe body; one end of the pipe body is a condensation section, and the other end of the pipe body is an evaporation section, with an adiabatic section between the condensation section and the evaporation section; its characteristic lies in that: a wick is arranged in the pipe body, and a gallium working fluid that fills the pipe body and circulates in the pipe body is provided.

[0011] The gallium working fluid is elemental gallium, or nanoparticles are added to elemental gallium, such as metal particles and carbon particles, etc., to enhance the heat exchange capacity.

[0012] In the normal temperature heat pipe and the medium temperature heat pipe, relevant working fluids are mixed in a certain proportion to meet relevant temperature requirements. For example, in normal temperature, R600a, R600, R-123, water, etc. are added in a proportion of 20%-70%; in medium temperature, sodium, potassium, zinc, mercury, etc. are added in a proportion of 20%-60%. The specific proportion is adjusted according to actual needs.

[0013] The inner diameter of the condensation section pipeline of the normal temperature heat pipe is 20 mm to 30 mm, the inner diameter of the adiabatic pipe is 22 mm to 32 mm, and the length is 200 mm to 400 mm. Among them, the lengths of the evaporation end and the condensation end are 300 mm to 600 mm and 200 to 400 mm respectively. The wall thickness is 4 mm to 8 mm. The thickness of the adiabatic sleeve is 5 mm to 9 mm; the wall thickness of the pipe body is 4 mm to 8 mm.

[0014] The inner diameter of the condensation section pipeline of the medium temperature heat pipe is 25 mm to 35 mm, the inner diameter of the adiabatic pipe is 27 mm to 37 mm, and the length is 250 mm to 450 mm. Among them, the lengths of the evaporation end and the condensation end are 350 mm to 650 mm and 250 to 450 mm respectively. The wall thickness is 5 mm to 10 mm. The thickness of the adiabatic sleeve is 6 mm to 12 mm; the wall thickness of the pipe body is 4 mm to 8 mm.

[0015] The inner diameter of the condensation section pipeline of the high temperature heat pipe is 30 mm to 40 mm, the inner diameter of the adiabatic pipe is 32 mm to 42 mm, and the length is 300 mm to 500 mm. Among them, the lengths of the evaporation end and the condensation end are 400 mm to 700 mm and 300 to 500 mm respectively. The wall thickness is 6 mm to 12 mm. The thickness of the adiabatic sleeve is 7 mm to 15 mm; the wall thickness of the pipe body is 4 mm to 8 mm.

[0016] The adiabatic section and the condensation section are straight pipes, and the cross-section of the pipe body is circular or square or equilateral triangle, annular, etc.; the inner diameter of the adiabatic section pipeline is larger than the inner diameters of the evaporation section and the condensation end. The inner diameter of the adiabatic section pipeline is larger than the inner diameters of the evaporation section and the condensation end, which can make the phase-changed gaseous working medium have a changing flow velocity when flowing from the evaporation section to the condensation section, improving the heat transfer. An adiabatic sleeve that wraps the pipe body is provided on the adiabatic section of the pipe body, and the space between the two pipes is evacuated. The adiabatic sleeve reduces the heat dissipation of the working medium in the adiabatic section.

[0017] The evaporation section is a variable cross-section structure with a gradually decreasing and then increasing shape, and the distance H between the tangent line at the minimum cross-section of the variable cross-section structure of the evaporation section and the maximum cross-section is 2 mm to 6 mm. The contact angle θ of the hydrophobic surface > 150°.

[0018] The outer surface of the evaporation section of the pipe body is set as a hydrophobic surface by the combined action of a nano-coating material and the gradually decreasing and then increasing surface of the evaporation section. The nano-coating material is Si, Zr, Al, Ti, TiO2, etc. It can make the high-temperature gas outside the evaporation section of the heat pipe quickly condense when encountering cold, and form water droplets due to the action of surface tension, generating bead condensation with better heat transfer effect.

[0019] The inner surface of the pipe body pipeline adopts sharp corners or rounded corners to protrude. The protrusion height is 2 mm to 4 mm. The materials are copper, graphene, Haynes230, GH2747, etc.

[0020] The tube body uses Haynes230 and 06Cr17Ni12Mo2 as the tube shell materials. The special physical structure of graphene brings excellent thermal conductivity to it. Haynes230 alloy is a nickel-chromium-tungsten-molybdenum alloy, with excellent high-temperature strength, oxidation resistance, extremely long-term thermal stability and good machinability.

[0021] The wick is a metal fiber composite wick, a microgroove wick, an axial channel type core, etc.

[0022] The gallium working fluid in the device flows in the high-temperature heat pipe; gallium and working fluids with boiling points meeting the relevant temperature ranges, such as water or freon, etc., flow in the normal-temperature heat pipe and the medium-temperature heat pipe, and the flow of the external circulating medium, such as water, air, supercritical water, liquid metal, etc., the flow of the two can be in the same direction of co-current or in the opposite direction of counter-current or cross-flow. It can be forced circulation or natural circulation.

[0023] The gallium heat pipe can be arranged vertically in a symmetric parallel or plum blossom shape to better and more evenly export the core heat.

[0024] The medium is the gallium working fluid. By selecting different tube body materials and arrangement methods, its working temperature range is: a normal-temperature heat pipe of 30°C to 200°C; a medium-temperature heat pipe of 200°C to 1000°C; and a high-temperature heat pipe above 1000°C. The gallium working fluid in the high-temperature heat pipe is elemental gallium. For the normal-temperature and medium-temperature heat pipes, water or other working fluids are added to elemental gallium. Nanoparticles can be added to all three types of heat pipes.

[0025] The heat pipe is a gallium working fluid normal-temperature heat pipe, the vacuum degree in the tube is 20 Torr to 25 Torr, and the pipe material uses graphene. The special physical structure of graphene brings excellent thermal conductivity to it. It is applicable to ordinary pressurized water reactors (working temperature around 150°C), especially in the same type of small or micro reactors. The natural circulation of the gallium medium in the tube exchanges heat with the external water.

[0026] The heat pipe is a gallium working fluid medium-temperature heat pipe, the vacuum degree in the tube is 10 Torr to 15 Torr, and the pipe material uses graphene. A certain amount of metal nanoparticles are also added to the gallium working fluid. It is applicable to supercritical water reactors (working temperature around 400°C), especially in the same type of small or micro reactors. The natural circulation of the gallium medium in the tube exchanges heat with the external supercritical water.

[0027] The heat pipe is a high-temperature heat pipe with gallium working fluid. The vacuum degree inside the pipe is 5 Torr - 8 Torr. The pipe material is selected as Haynes230, which has excellent high-temperature strength, oxidation resistance, ultra-long-term thermal stability and good workability. It is applicable to high-temperature gas-cooled reactors (with an operating temperature of about 1000 °C), especially in similar small or micro reactors, where the natural circulation of the gallium medium inside the pipe exchanges heat with the high-temperature helium gas.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] The heat pipe of the present invention uses gallium working fluid. The wide temperature range of gallium enables it to be used in the small reactor energy industry, which is simple, convenient and efficient. The use of the heat pipe greatly improves the cooling capacity and safety performance of the system. As an alternative product to replace the shell-and-tube heat exchanger, it can achieve the effects of efficient and passive heat transfer, reduce pipeline links, build an integrated reactor system, and better ensure the safety of the reactor. The gallium heat pipe of the present invention can be applied to a wide range of fields such as mobile nuclear reactors, integrated energy systems, deep sea, and military-civilian integration.

[0030] Adding a certain amount of metal nanoparticles or low-boiling-point working fluid to the gallium working fluid causes a sharp drop in the boiling point and also enhances heat transfer. It is applicable to ordinary pressurized water reactors (with an operating temperature of about 150 °C), especially in similar small or micro reactors, where the natural circulation of the gallium medium inside the pipe exchanges heat with the water outside the pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic structural diagram of the present invention;

[0032] Figure 2 is Figure 1 the A-A sectional view of

[0033] Figure 3 is Figure 1 the B-B sectional view of

[0034] Figure 4 is a schematic cross-sectional view of the evaporation section in the transverse direction;

[0035] Figure 5 is a schematic diagram of the contact between the hydrophobic surface of the evaporation section and the water droplets;

[0036] In the figure: 1, pipe body; 11 - condensation section; 12 - evaporation section; 13 - adiabatic section; 2, wick; 3, pipe wall; 4 - adiabatic sleeve; 5 - nano-coating; 6, liquid droplet; 7, gas flow direction inside the heat pipe; 8, liquid flow direction inside the heat pipe. DETAILED DESCRIPTION OF THE INVENTION

[0037] The following further describes the present invention in conjunction with the drawings and specific embodiments.

[0038] The structure of the gallium heat pipe of the present invention is asFigure 1 As shown in the figure, it includes a tube body 1, a liquid absorption core 2 arranged inside the tube body, and a working medium filled inside the tube body and circulating inside the tube body. The high-temperature working medium is gallium metal, and the normal-temperature and medium-temperature working media are gallium metal and working media with boiling points meeting relevant temperature ranges, such as water or Freon, etc. 50%-70% of refrigerants such as R600a, R600, and R-123 are added at normal temperature; 40%-60% of other boiling-point metals such as sodium, potassium, zinc, and mercury are added at medium temperature. The specific ratio is determined according to actual requirements.

[0039] The working medium gallium of the heat pipe of the present invention is in a liquid state at 29.76°C. Depending on the type and state of the working medium outside the tube, such as water, supercritical water, and high-temperature helium gas, etc., therefore, it is possible to adjust and apply to normal-temperature heat pipes with a working temperature range of 30°C to 200°C; medium-temperature heat pipes with a working temperature range of 200°C to 1000°C; and high-temperature heat pipes with a working temperature above 1000°C.

[0040] The inner diameter of the condensation section pipeline of the normal-temperature heat pipe of the present invention is 20mm to 30mm, the inner diameter of the adiabatic pipe is 22mm to 32mm, and the length is 200mm to 400mm. Among them, the lengths of the evaporation end and the condensation end are 300mm to 600mm and 200 to 400mm respectively. The wall thickness is 4mm to 8mm. The thickness of the adiabatic sleeve is 5mm to 9mm; the wall thickness of the tube body is 4mm to 8mm.

[0041] The inner diameter of the condensation section pipeline of the medium-temperature heat pipe of the present invention is 25mm to 35mm, the inner diameter of the adiabatic pipe is 27mm to 37mm, and the length is 250mm to 450mm. Among them, the lengths of the evaporation end and the condensation end are 350mm to 650mm and 250 to 450mm respectively. The wall thickness is 5mm to 10mm. The thickness of the adiabatic sleeve is 6mm to 12mm; the wall thickness of the tube body is 4mm to 8mm.

[0042] The inner diameter of the condensation section pipeline of the high-temperature heat pipe of the present invention is 30mm to 40mm, the inner diameter of the adiabatic pipe is 32mm to 42mm, and the length is 300mm to 500mm. Among them, the lengths of the evaporation end and the condensation end are 400mm to 700mm and 300 to 500mm respectively. The wall thickness is 6mm to 12mm. The thickness of the adiabatic sleeve is 7mm to 15mm; the wall thickness of the tube body is 4mm to 8mm.

[0043] For the gallium heat pipe of the present invention, the straight pipe between the evaporation section 12 and the condensation section 11 has a circular, square, equilateral triangle, annular, or other cross-sectional shapes.

[0044] The evaporation section 12 of the heat pipe of the present invention adopts an inwards concave manner, such as Figure 4 as described, the evaporation section 12 is a surface of revolution, and the inwards concave depth H is 2mm to 6mm.

[0045] The hydrophobic surface of the evaporation section of the heat pipe of the present invention is composed of a nano - coating, and the nano - coating materials are Si, Zr, Al, Ti, TiO2, etc.

[0046] The tube wall 3 of the heat pipe of the present invention uses Haynes230, 06Cr17Ni12Mo2, etc. as the shell materials.

[0047] The wick 2 of the gallium heat pipe of the present invention is a metal fiber composite wick liquid core, micro - groove wick, axial channel wick, etc. It can provide a large capillary force, reduce the pressure loss of the reflux liquid, and reduce the influence of the inclination change on the starting performance of the heat pipe. The filling ratio of this device is about 30% - 80%.

[0048] The gallium working fluid in the tube of the present invention flows in the heat pipe, or nano - particles such as metal particles and carbon particles are added to it to enhance the heat transfer ability.

[0049] The flow of the external circulation medium of the heat pipe of the present invention, such as water, air, liquid metal, supercritical CO2, etc.

[0050] The flow of both the inside and outside of the heat pipe of the present invention can be in the same - direction co - current, or in the opposite - direction counter - current, or cross - flow. It can be forced circulation or natural circulation.

[0051] One end of the heat pipe body 1 of the present invention is the condensation section 11, and the other end of the tube body is the evaporation section 12. There is an adiabatic section 13 between the condensation section 11 and the evaporation section 12, and the inner diameter of the pipeline of the adiabatic section 13 is larger than the inner diameters of the evaporation section 12 and the condensation end 11. An adiabatic sleeve 4 wrapping the tube wall 3 is arranged in the adiabatic section 13 of the tube body; the outer surface of the evaporation section of the tube body is set as a hydrophobic surface. The contact angle θ of the hydrophobic surface > 150°, which is convenient for water droplets to condense on the wall surface of the evaporation section.

[0052] The condensation state of the gas outside the heat pipe of the present invention is as Figure 5 shown. During the working process of the heat pipe, the outer surface of the evaporation section 12 of the heat pipe adopts a slightly concave structure, and after adopting the nano - material coating, the evaporation section 1 forms a lotus effect, forming a hydrophobic surface. The high - temperature gas outside the tube is cooled (the temperature of the evaporation section is lower, and it condenses when the temperature of the outer wall surface of the tube is lower than the steam saturation temperature), and due to the action of surface tension, liquid droplets 6 are formed. The bead - like condensation heat transfer effect produced is better than the non - hydrophobic film - like condensation.

[0053] For the gallium heat pipe of the present invention, when a heat source is applied to the evaporation section 12 of the heat pipe, the liquid working medium gallium in the high-temperature evaporation section 12 of the heat pipe absorbs heat and its temperature continuously rises. After the working medium rises to the phase change point, it undergoes a phase change and becomes vapor, which can flow from left to right in the pipe body 1 and pass through the protrusions on the inner surface of the pipe to flow through the device; the normal-temperature and medium-temperature heat pipes use gallium with high thermal conductivity to transfer heat and water that can undergo a phase change to realize the subsequent phase change process of the heat pipe. Among them, the materials for the protrusions on the inner surface of the pipe are copper, graphene, Haynes 230, GH2747, etc., which can achieve different heat transfer effects.

[0054] For the heat pipe of the present invention, the vapor runs to the condensation section 11, releases heat and condenses into a liquid working medium. The liquid working medium in the condensation section flows back to the evaporation section 12 under the action of the capillary driving force generated by the wick 4, and a new cycle begins. Such continuous cycling efficiently transfers heat from the evaporation section 12 to the condensation section 11.

[0055] For the heat pipe of the present invention, external heat is absorbed by the low-temperature evaporation section 12, and internal heat is discharged from the condensation section 11 to the outside of the pipe.

Claims

1. A gallium heat pipe for a reactor, comprising a pipe body; one end of the pipe body is a condensation section, the other end of the pipe body is an evaporation section, and an adiabatic section is provided between the condensation section and the evaporation section; characterized in that: A liquid absorption core is arranged in the tube body, and a gallium-based gallium working medium filled in the tube body and circulating in the tube body; the gallium working medium is formed by adding nanoparticles and other working media to elemental gallium, the other working medium is a low-boiling-point working medium, and the proportion of the low-boiling-point working medium is 20%-70%. The low-boiling-point working medium includes a mixture formed by any one or more combinations of R600a, R600, R-123 or water. The cross-sectional area of the adiabatic section pipeline is larger than the cross-sectional areas of the evaporation section and the condensation end.

2. The gallium heat pipe for a reactor according to claim 1, wherein: The added nanoparticles are metal particles or carbon particles.

3. The gallium heat pipe for a reactor according to claim 1, wherein: The hydrophobic surface located on the outer surface of the evaporation section is composed of a nano-coating located on the outer surface of the evaporation section, and the contact angle θ of the hydrophobic surface > 150°.

4. The gallium heat pipe for a reactor according to claim 3, characterized in that: The evaporation section is a variable cross-section structure with a gradually decreasing and then increasing cross-section, and together with the nano-coating, it forms a lotus effect surface on the evaporation section; the distance H between the tangent line at the minimum cross-section of the evaporation section with the variable cross-section structure and the maximum cross-section is 2 mm to 6 mm.

5. The gallium heat pipe according to claim 3, wherein: The nano-coating material is Si, Zr, Al, Ti or TiO2.

6. The gallium heat pipe according to claim 1, characterized in that: The adiabatic section and the condensation section are straight pipes; the adiabatic section adopts a casing method of an inner pipe and an outer pipe, and the space between the inner pipe and the outer pipe is evacuated.

7. The gallium heat pipe according to claim 1, characterized in that: The inner surface of the pipeline adopts sharp corners or rounded corners to protrude; the height of the protrusion is 2 mm to 4 mm; the material of the protrusion is copper, graphene, Haynes230 or GH2747.

8. A heat exchange device, characterized in that, Use the gallium heat pipe described in any one of claims 1-7; the flow of the gallium working medium inside the gallium heat pipe and the external circulating medium outside the gallium heat pipe is in the same direction of co-current or in the opposite direction of counter-current or cross-flow; the circulation method is forced circulation or natural circulation; the gallium heat pipes are arranged in a vertical manner, a symmetric parallel manner or a plum blossom manner.

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