Flat heat pipe coupled plate fuel dual thermoelectric conversion mode heat pipe cooled reactor

Abstract

The present application belongs to the field of energy technology, and discloses a flat heat pipe coupled plate fuel double-heat electric conversion mode heat pipe cooled reactor, which comprises: a heat pipe reactor core section arrangement and a heat pipe reactor coupled heat electric conversion device; the heat pipe reactor core section arrangement specifically comprises: a heat pipe reactor containment structure, a plate heat pipe and plate fuel; the heat pipe reactor coupled heat electric conversion device comprises: a thermionic power generation device, a thermoelectric generation arrangement and a DC-DC converter. The present application adopts full surface welding of flat heat pipes and plate fuel, which can effectively reduce the gap thermal resistance caused by the heat pipe reactor structure framework and improve the heat transfer efficiency. On the other hand, the heat transfer efficiency of the plate heat pipe is superior to that of the traditional round pipe heat pipe under the same power condition, and the plate fuel has the advantages of compact structure and better heat transfer characteristics.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of energy technology, and in particular relates to a flat heat pipe coupled plate fuel dual thermoelectric conversion mode heat pipe cooled reactor. BACKGROUND

[0002] With the intensifying development and deployment of deep space, deep sea, polar and other fields in China, energy problems have become an important factor restricting task execution and interest maintenance. Compared with traditional energy systems, nuclear energy has shown infinite potential due to its unique advantages. As one of the candidate reactor types of the fourth generation advanced nuclear energy system, the core feature of the heat pipe cooled reactor is to realize efficient heat transfer and passive safety of the reactor by using heat pipe technology. With its non-active heat transfer characteristics, high safety, modular design and environmental adaptability, it has become an important research direction in the fields of deep space exploration, deep sea diving and land-based distributed energy.

[0003] There are three major technical bottlenecks in the current heat pipe cooled reactor: (1) The contact between the traditional cylindrical heat pipe and the fuel rod gap results in excessive thermal resistance, and the heat transfer efficiency decays significantly (experimental data show that the contact thermal resistance accounts for more than 30%); (2) The single thermoelectric conversion mode has low energy utilization rate, and the actual measured temperature difference power generation efficiency is less than 8%; (3) The core structure has high redundancy, and the power density is limited (the existing design is generally less than 50kW / L).

[0004] The present technology specifically proposes: ① an integrated configuration of flat heat pipe coupled plate fuel, ② a gradient dual-mode thermoelectric conversion system, and ③ a modular core integration scheme, which breaks through the existing technical bottlenecks. It is particularly suitable for compact energy supply systems in extreme environments such as deep space probes and polar stations. SUMMARY

[0005] In view of the problems existing in the prior art, the present application provides a flat heat pipe coupled plate fuel dual thermoelectric conversion mode heat pipe cooled reactor.

[0006] The present application is implemented as follows: a flat heat pipe coupled plate fuel dual thermoelectric conversion mode heat pipe cooled reactor, which comprises: a core cross-sectional arrangement of a heat pipe reactor and a heat pipe reactor coupled thermoelectric conversion device;

[0007] The core cross-sectional arrangement of the heat pipe reactor specifically comprises: a containment structure of the heat pipe reactor, a plate heat pipe and a plate fuel.

[0008] The containment structure of the heat pipe reactor is composed of neutron absorbing and shielding materials and structural protection materials, and plays a role in protecting the core and radiation protection.

[0009] The plate heat pipe and the plate fuel are arranged together in mutual coupling and are arranged in intercalation; heat is directly transferred through the pipe wall, a skeleton structure of a traditional honeycomb coal type heat pipe stack is not needed, the gap thermal resistance caused by the skeleton structure is effectively reduced, and the heat exchange efficiency of the stack core is improved.

[0010] The heat pipe stack coupled thermoelectric conversion device comprises a thermionic power generation device, a thermoelectric generation arrangement and a DC-DC converter.

[0011] Further, in the heat pipe stack coupled thermoelectric conversion device, the heat pipe absorbs the heat generated by the fuel element in the evaporation section and transfers the heat to the thermoelectric conversion device; the heat pipe is used as a heat transfer element, and the heat transfer efficiency is improved by hundreds or thousands of times compared with conventional metal heat conduction; in addition, the heat pipe is a passive heat transfer element, and has higher inherent safety; in the condensation section, power generation is performed through two-stage thermoelectric conversion devices.

[0012] Further, the thermionic power generation device can effectively utilize the high-temperature heat pipe condensation section to perform thermoelectric conversion in the high-temperature region, and the efficiency can reach 12-15%; the thermoelectric generation mode is used in the end of the condensation section to generate power, and low-grade energy is used for thermoelectric conversion, and the efficiency can reach 6-8%; the high-voltage low-current output of the thermionic power generation and the low-voltage high-current output of the thermoelectric generation are matched with the load demand through the DC-DC converter in parallel.

[0013] In combination with the above technical solutions and the technical problems solved, the technical solutions to be protected by the present application have the following advantages and positive effects:

[0014] The conventional heat pipe cooled reactor generally uses a round pipe type heat pipe and a rod type fuel, and a skeleton structure is needed for combination, the existence of the skeleton structure causes high contact thermal resistance between the heat pipe and the fuel rod, and the heat transfer efficiency is limited. Experimental data shows that the contact thermal resistance accounts for more than 30% of the total thermal resistance, which seriously affects the overall performance of the system. The present application innovatively uses a flat heat pipe and a full-surface welding of a plate type fuel, eliminates the gap thermal resistance, and makes the heat transfer more efficient and uniform. On the other hand, the heat transfer capacity of the plate heat pipe is better than that of the conventional round pipe heat pipe under the same power condition, and the structure is more compact, so that the overall design of the stack core is more optimized, and the power density and the system heat management capability are further improved.

[0015] The heat-electricity conversion mode of the traditional heat pipe cooled reactor is single, and usually only relies on thermoelectric generation (TEG), resulting in low energy utilization rate of the high temperature section. The application innovatively proposes a double-mode cooperative heat-electricity conversion technology, adopts thermionic power generation (TIC) in the high temperature section (>600 DEG C) of the heat pipe condensing section, and adopts thermoelectric generation (TEG) in the low temperature section (<600 DEG C), forming a gradient energy utilization system. Through the technical scheme, not only the high-grade energy of the high temperature section is fully utilized, but also the waste heat utilization rate of the low temperature section is effectively improved, so that the overall heat-electricity conversion efficiency is increased from 8% of the traditional single mode to more than 18%.

[0016] The application greatly optimizes the core structure by coupling the high energy density of the plate fuel and the high efficient heat transfer characteristics of the plate heat pipe, so that the power output capacity in unit volume is significantly enhanced. In addition, the integration of the double-mode heat-electricity conversion system makes the power density of the heat pipe reactor of the application increased from 50 kW / L of the existing design to 80 kW / L, breaking through the volume and weight limit of the extreme environment power supply system, and providing a more efficient nuclear power supply scheme for future space, deep sea, remote area and other application scenarios.

[0017] In the current international heat pipe cooled reactor research, there is no integrated design of the flat heat pipe and the plate fuel full-surface welding, and there is no public scheme of the gradient double-mode heat-electricity conversion system. The application integrates the high temperature thermionic power generation and the low temperature thermoelectric generation technology, and first realizes the gradient energy utilization in the whole temperature section of the heat pipe condensing section, breaks through the efficiency limit of the single heat-electricity conversion mode, and at the same time, the plate heat pipe and the fuel coupling design are first created in the field of nuclear reactor heat transfer, so that the power density and the structural compactness are significantly improved, and a new direction of the heat pipe cooled reactor is opened up.

[0018] In the traditional heat pipe cooled reactor, the heat transfer efficiency loss caused by the gap contact between the cylindrical heat pipe and the fuel rod is a key technical problem faced by the industry. The application reduces the gap thermal resistance from more than 30% to less than 5% by directly welding the flat heat pipe and the plate fuel, greatly improving the heat transfer efficiency. In addition, through the double-mode heat-electricity conversion technology, the comprehensive energy utilization rate of the system is increased from 8% of the traditional single mode to more than 18%, and the modular core integration scheme makes the power density increased by 60%, so that a more efficient and compact solution for nuclear power supply in extreme environment is provided.

[0019] It is generally believed in the industry that high-temperature thermionic power generation (TIC) and low-temperature thermoelectric power generation (TEG) are difficult to work together, and the complexity of the dual-mode system is high, and it is difficult to realize engineering application. The present application ensures the efficient parallel operation of the two power generation modes through gradient heat dissipation material layout (such as LaB6 cathode in high-temperature area and Yb-doped skutterudite module in low-temperature area) and intelligent power management strategy (MPPT maximum power point tracking circuit + redundancy control). Under variable working conditions, the efficiency loss of the system is controlled within 5%, which greatly improves the engineering practicability of multi-mode thermoelectric conversion technology, successfully breaks the inherent cognition of the industry on the feasibility of dual-mode thermoelectric conversion technology, and lays an important technical foundation for future efficient and compact nuclear power supply systems. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is the core cross-sectional layout of the heat pipe reactor provided by the embodiment of the present application;

[0021] Figure 2 is the structure diagram of the heat pipe reactor coupled with the thermoelectric conversion device provided by the embodiment of the present application;

[0022] In the figure: 1, containment structure of the heat pipe reactor; 2, plate heat pipe; 3, plate fuel; 4, thermionic power generation device; 5, thermoelectric power generation arrangement; 6, DC-DC converter. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application will be further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0024] As shown in Figure 1 , 2 The embodiment of the present application provides a flat heat pipe coupled with a plate fuel dual-thermoelectric conversion mode heat pipe cooled reactor, which comprises: a core cross-sectional layout of a heat pipe reactor and a heat pipe reactor coupled with a thermoelectric conversion device;

[0025] The core cross-sectional layout of the heat pipe reactor specifically comprises: a containment structure 1 of the heat pipe reactor, a plate heat pipe 2, and a plate fuel 3.

[0026] The containment structure of the heat pipe reactor is composed of neutron absorption and shielding materials and structural protection materials, and plays a role of protecting the core and radiation protection;

[0027] The plate heat pipe and the plate fuel are arranged together and embedded with each other, and heat is directly transferred through the pipe wall, effectively reducing the gap thermal resistance and improving the heat exchange efficiency of the core;

[0028] The heat pipe stack coupled thermoelectric conversion device comprises a thermionic power generation device 4, a thermoelectric generation arrangement 5, and a DC-DC converter 6.

[0029] In the heat pipe stack coupled thermoelectric conversion device, the heat pipe absorbs heat generated by the fuel element in the evaporation section and transmits it to the thermoelectric conversion device; the heat pipe is used as a heat transfer element, and its heat transfer efficiency is hundreds or even thousands of times higher than that of conventional metal heat conduction; in addition, the heat pipe is a non-energy heat transfer element, and has higher inherent safety; in the condensation section, power generation is performed by two-stage thermoelectric conversion devices.

[0030] The thermionic power generation device 4 can effectively utilize the high temperature heat pipe condensation section initial section temperature higher area for thermoelectric conversion, and the efficiency can reach 12-15%; the thermoelectric generation mode is used at the end of the condensation section to generate power, and low-grade energy is used for thermoelectric conversion, and the efficiency can reach 6-8%; the high-voltage low-current output of the thermionic power generation and the low-voltage high-current output of the thermoelectric generation are connected in parallel through the DC-DC converter 6 to match the load demand.

[0031] 1. Gradient thermoelectric material layout

[0032] High temperature area: The thermionic emission adopts a lanthanum-doped lanthanum hexaboride (LaB6) cathode, which can withstand temperatures of >1000℃ and has an escape work as low as 2.7eV.

[0033] Low temperature area: The skutterudite thermoelectric module has a ZT value of 1.4 (at 500℃) by filling Yb nanoparticles

[0034] 2. Internal heat transfer enhancement of plate-shaped heat pipe

[0035] Along the evaporation section to the condensation section of the heat pipe, there are numerous groove structures that can effectively provide capillary force to suck and return the working medium, improving the non-active heat transfer characteristics of the heat pipe. In addition, laser etching micro channels can be used on the inner surface of the heat pipe to effectively improve the capillary force. Point welding of the wick on the inner wall of the heat pipe further improves the return ability of the working medium in the heat pipe.

[0036] 3. Power management strategy

[0037] The thermionic module and the thermoelectric module are independently controlled by a maximum power point tracking (MPPT) circuit, and the load impedance is optimized in real time.

[0038] The staggered parallel Boost topology is adopted, and the output voltage fluctuation is stabilized within ±1%.

[0039] When the variable power causes the temperature of the condensation section of the heat pipe to change, the efficiency of the thermoelectric conversion module may even fail due to the temperature being out of the power generation range. Through the adjacent module redundancy circuit, the load is taken over, and the system efficiency loss is within 5%.

[0040] The application is suitable for compact nuclear power supply of lunar, Mars and other extraterrestrial bases, and can provide continuous and stable energy for detectors, communication equipment and life support systems. Due to the large temperature difference in outer space environment, the traditional power supply system is difficult to operate stably for a long time, and the application adopts double-mode thermoelectric conversion + high-efficiency heat pipe cooling, which can maintain high energy conversion in extreme temperature environment, and provides a more reliable energy solution for future deep space exploration.

[0041] The application can be used as a high-power density power supply for unmanned underwater vehicle (UUV) or deep sea station, and can provide stable energy for long-term underwater operation. Compared with the traditional nuclear power system, the plate type fuel + heat pipe direct coupling structure of the application can maintain good heat transfer performance in the underwater high pressure environment, the double-mode thermoelectric conversion technology can maximize the utilization of energy in different temperature ranges, improve the endurance of the underwater vehicle, and enable it to perform longer detection tasks underwater.

[0042] The application can be used as a distributed energy system for polar scientific research stations, border sentry stations and remote observation stations, and is particularly suitable for extreme low temperature environments. In extremely cold conditions, the efficiency of traditional battery storage and diesel generators decreases significantly, while the high-efficiency heat pipe heat transfer + double-mode thermoelectric conversion system of the application can operate stably and adapt to extreme climate conditions, ensuring long-term energy supply.

[0043] The application can be used as a backup power supply or off-grid energy source to meet the needs of disaster emergency power supply, military covert energy supply and the like. Compared with the traditional nuclear micro-heap, the modular core design of the application makes it easier to expand, and can provide stable and efficient power output in small nuclear power applications, improving safety and practicality.

[0044] The application embodiment obtains the related evidence of the technical effect.

[0045] 1. Improved heat transfer efficiency and reduced contact thermal resistance

[0046] According to Fourier heat conduction law, the contact thermal resistance R contact is inversely proportional to the contact area A, that is:

[0047] R contact = 1 / h c A

[0048] In the formula, h c is the contact heat transfer coefficient. The line contact of the traditional cylindrical heat pipe and the fuel rod leads to small contact area (A 线接触 ∝ r·L, r is the radius, and L is the length), while the flat contact area of the plate heat pipe and the fuel of the application is significantly increased (A 面接触 ∝ W·L, W is the plate width). Combined with vacuum diffusion welding technology (interface defect rate ≤ 0.1%), the contact heat transfer coefficient h c is improved.

[0049] 2. Energy efficiency optimization theory of dual-mode thermoelectric conversion

[0050] a. High-temperature zone thermionic power generation efficiency

[0051] The current density J in thermionic power generation follows the Richardson-Dushman equation:

[0052] J = AT 2 e -φ / kT

[0053] In the formula, A is the emission constant, φ is the work function, and T is the cathode temperature. Using a LaB6 cathode (φ = 2.7 eV) at 650℃, the theoretical current density is J = 12 A / cm². 2 With optimized electrode spacing (d = 50 μm), the theoretical conversion efficiency can reach 15.5%.

[0054] b. Low-temperature thermoelectric power generation performance

[0055] The dimensionless figure of merit ZT of cobaltite thermoelectric materials determines the upper limit of conversion efficiency:

[0056]

[0057] By doping with Yb nanoparticles (ZT = 1.4 at around 500℃), the theoretical efficiency reaches 8.2% at ΔT = 300℃ (Th = 500℃, Tc = 200℃).

[0058] c. Energy level matching in dual-mode collaboration

[0059] Thermo-ionization power generation outputs high voltage (V) TI ≈0.8V) and thermoelectric low voltage (V) TEG (≈0.2V) is connected in parallel through a DC-DC converter, the total system efficiency η total It can be modeled as:

[0060]

[0061] When P TI :P TEG When the ratio is 3:2, the theoretical overall efficiency η total＝ With an efficiency of 18.3%, this invention can achieve lower thermal resistance and higher overall conversion efficiency.

[0062] It should be noted that embodiments of the present invention can be implemented in hardware, software, or a combination of both. The hardware portion can be implemented using dedicated logic; the software portion can be stored in memory and executed by a suitable instruction execution system, such as a microprocessor or dedicated-design hardware. Those skilled in the art will understand that the above-described devices and methods can be implemented using computer-executable instructions and / or included in processor control code, for example, such code provided on a carrier medium such as a disk, CD, or DVD-ROM, a programmable memory such as read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The devices and modules of the present invention can be implemented by hardware circuitry such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field-programmable gate arrays, programmable logic devices, etc., or by software executed by various types of processors, or by a combination of the above-described hardware circuitry and software, such as firmware.

[0063] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A flat heat pipe coupled plate type fuel dual thermoelectric conversion mode heat pipe cooled reactor characterized by, The application relates to a heat pipe reactor, which comprises the following parts: a reactor core cross-section arrangement of a heat pipe reactor, which comprises a containment structure, a plate heat pipe and a plate fuel; a heat pipe reactor coupled with a thermoelectric conversion device, which comprises a thermionic power generation device, a thermoelectric generation arrangement and a DC-DC converter; the plate heat pipe and the plate fuel adopt a full-surface welding structure, the evaporation section of the plate heat pipe is directly contacted with the fuel, and heat is transmitted through the pipe wall; the thermionic power generation device is arranged in a high-temperature area of the condensation section of the heat pipe, and the thermoelectric generation arrangement is arranged in a low-temperature area of the condensation section of the heat pipe; the DC-DC converter is used for voltage adjustment and matching of load requirements of electric outputs of the thermionic power generation device and the thermoelectric generation arrangement.

2. The flat heat pipe coupled plate fuel dual thermoelectric conversion mode heat pipe cooled reactor according to claim 1, wherein, the containment structure of the heat pipe reactor is composed of neutron absorption material, shielding material and structural protection material, and forms a closed structure around the heat pipe reactor.

3. The flat heat pipe coupled plate fuel dual thermoelectric conversion mode heat pipe cooled reactor of claim 1, wherein, the evaporation section surface of the plate heat pipe is provided with a micro-channel structure, and a wick is spot-welded on the inner wall of the heat pipe to enhance the capillary return ability of the working medium.

4. The flat heat pipe coupled plate type fuel dual thermoelectric conversion mode heat pipe cooled reactor according to claim 1, wherein the thermionic power generation device adopts a lanthanum-doped lanthanum hexaboride (LaB6) cathode, and the cathode spacing is less than 100 mu m.

5. The flat heat pipe coupled plate fuel dual thermoelectric conversion mode heat pipe cooled reactor of claim 1, wherein, the thermoelectric generation arrangement adopts a skutterudite thermoelectric material and fills Yb nanoparticles to improve the thermoelectric conversion efficiency.

6. The flat heat pipe coupled plate fuel dual thermoelectric conversion mode heat pipe cooled reactor of claim 1, wherein, the DC-DC converter adopts an interleaved parallel Boost topology and has a maximum power point tracking (MPPT) circuit to optimize the load impedance.

7. The flat heat pipe coupled plate fuel dual thermoelectric conversion mode heat pipe cooled reactor of claim 1, wherein, the heat pipe reactor adopts a modular design, and the reactor core units of the heat pipe reactor can be connected in parallel to expand to meet different power requirements.

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