Thermosiphon-assisted natural circulation multistage liquid cooling method

Abstract

The invention relates to a thermosyphon-assisted natural circulation multistage liquid cooling method, which comprises the following steps of: arranging a double-layer heat exchange interface consisting of a lower high-heat-conduction layer and an upper low-heat-conduction layer in a heat source adjacent area to form a local temperature rise abrupt change area; when the temperature reaches a working liquid boiling threshold value, a local thermosyphon flow jump is generated to drive liquid circulation, and the thermosyphon flow jump has the periodic retriggering capacity by adjusting the material and structure parameters of the double-layer heat exchange interface; a plurality of distributed impedance regulation and control nodes are sequentially arranged along a flowing path of the thermosyphon, so that a flow difference is established between adjacent nodes; multiple stages of thermosyphon cavities are arranged on a flowing path in series, and the starting time sequences of the adjacent thermosyphon cavities are matched to achieve stage-by-stage progressive syphon driving. The condensate is adhered and flows stably in a liquid film form in a condensation outlet area of the last-stage thermosyphon cavity; a liquid turning buffer area is arranged behind a condensation outlet, condensate is guided to a mild backflow path, and closed-loop natural circulation is completed.

Description

TECHNICAL FIELD

[0001] The present application relates to a thermosyphon-assisted liquid cooling method, in particular, a thermosyphon-assisted natural circulation multi-stage liquid cooling method. BACKGROUND

[0002] The prior art such as Chinese patent CN112839490A proposes a two-phase flow active-passive multi-stage data center cabinet heat dissipation device and method, which provides an engineering idea in terms of overall heat dissipation efficiency, module level energy integration, PUE (Power Usage Effectiveness) optimization, etc. However, from the comparison of structure mechanism, thermal response capability, system dynamic self-adjusting property, liquid driving mode and other dimensions, the application still has some obvious deficiencies and limitations in the application of the thermosyphon-assisted natural circulation multi-stage liquid cooling system.

[0003] Firstly, the essence of the application is to adopt a mixed active-passive driving + closed-loop two-phase flow architecture, and the core flow driving force depends on the liquid pump to maintain the fluid flow in the main circulation passage, and the gas chamber is used to adjust the gas pressure stability to assist the phase change efficiency. This structure indeed has certain fluid control advantages in the scene of large system size and high load heat flux density, but the passive section (thermosyphon) exists more as a functional supplement, which is not the core circulation driving link, so that the thermosyphon effect cannot form the main flow rhythm regulator in the system. In the absence of precise control of the thermal triggering sequence and multi-stage coupling mechanism, the thermosyphon structure cannot realize the real sense of progressive dynamic driving by stages, and the adaptive behavior in the liquid cooling network is severely limited. Secondly, from the perspective of thermal response coordination, the application does not introduce the thermal response adjustment structure of multi-stage evaporation interval in the design, such as the key control means of thermal conductivity step distribution, thermal interface resistance regulation, microstructure pattern heat conduction design, etc. Therefore, when facing high-frequency thermal disturbance, load mutation or environmental temperature fluctuation, the response timing of the heat dissipation cavity almost completely depends on the gas-liquid pressure difference and the pump control rhythm, and lacks structural adaptive ability, resulting in insufficient robustness of the system as a whole to dynamic uncertain conditions (such as local hot spot jumping, partition power drift).

[0004] Again, although this scheme proposes a multi-level heat dissipation structure, this multi-level nature is more reflected in the physical integration of module stacking and multi-point condensation path, rather than the functional differentiation of heat driving levels. Without building layer-by-layer heat jump triggering, interlayer heat transfer rhythm delay, and heterogeneous thermosyphon cavity sequential response, the entire system is prone to synchronization in jump driving rhythm, strong coupling, and the risk of siphon conflict or liquid bridge backflow blockage, making it difficult to meet the requirements of different power chips in high-density electronic component areas. In addition, although the design of this invention includes a passive switching mechanism to improve energy efficiency, in actual application, the system still needs to maintain a high energy input to ensure cycle stability due to the presence of a pump, and the pump control has obvious response lag to small regional power changes. On the other hand, this invention does not use key elements such as phase change film energy storage layer, local heat capacity regulation cavity, and directional heat conduction structure, so it cannot achieve self-buffering, self-triggering, and self-dissipation of the thermal excitation process under rapid load changes, which can easily lead to phenomena such as subcooled liquid impact, jump cycle disorder, and incomplete condensation, causing unstable liquid backflow pressure, especially in vertical arrangement or distributed chip cooling structures, which will further amplify cycle fluctuations.

[0005] Further analysis shows that this patent is mainly used for large cabinet-level equipment in data centers, with complex structure and high redundancy of components. Although the PUE is optimized, it is difficult to be applied to chip-level packaging, board-level thermal management, edge computing devices, or space resource limited platforms. Finally, from the perspective of engineering generality, this patent emphasizes the use of auxiliary equipment such as gas pressure regulation and liquid reservoir space control to cooperate with the thermosyphon operation. This heat dissipation system that relies on environmental closure and structural integrity has high requirements for maintenance, expansion, and system fault self-recovery ability, and is easily affected by single-point failure. SUMMARY

[0006] The purpose of the present application is to provide a thermosyphon-assisted natural circulation multi-level liquid cooling method, thereby solving some of the problems and deficiencies pointed out in the background art.

[0007] The technical solution adopted by the present application to solve the above technical problems is as follows: a thermosyphon-assisted natural circulation multi-level liquid cooling method, comprising: setting a double-layer heat exchange interface composed of a lower layer of high thermal conductivity layer and an upper layer of low thermal conductivity layer in the vicinity of the heat source to form a local temperature rise mutation zone; when the mutation zone temperature reaches the working liquid boiling threshold, a local thermosyphon flow jump is generated to drive liquid circulation, and by adjusting the material and structural parameters of the double-layer heat exchange interface, the thermosyphon flow jump has periodic retriggering capability.

[0008] A plurality of distributed impedance regulation nodes are arranged along the flow path of the thermosyphon in sequence, each impedance regulation node including an expansion cavity and a capillary contraction groove, for adjusting the flow rate of the fluid passing through the node according to the node position and real-time temperature, thereby establishing a flow difference between adjacent nodes;

[0009] A plurality of stages of thermosyphon cavities are arranged in series on the flow path, each stage of thermosyphon cavity is filled with working liquid with a boiling point successively increased, and the starting time of adjacent thermosyphon cavities is matched by selecting different inner wall thermal conductivities or setting heat transfer delay structures, so as to realize progressive siphon driving by stages;

[0010] A liquidophilic membrane layer and a wall surface with microstructure are arranged at the condensation outlet area of the last stage of thermosyphon cavity, so that the condensed liquid adheres and flows smoothly in the form of liquid film; a heat sink material or a micro-cavity structure is arranged at the condensation outlet area, so as to absorb part of the condensation latent heat and inhibit the impact of supercooled liquid; and a liquid turning buffer zone is arranged after the condensation outlet, so as to guide the condensed liquid to a gentle return path and complete the closed-loop natural circulation.

[0011] Further, the construction method of the thermosyphon flow burst with periodic retriggering capability comprises:

[0012] A composite heat exchange interface composed of a lower layer and an upper layer with a significant difference in thermal conductivity is arranged at the heat source contact area, wherein the thermal conductivity of the lower layer is higher than that of the upper layer; the lower layer quickly transfers heat to the working liquid, so that the local working medium reaches the vaporization condition and generates a steam driving force; the upper layer has heat retention due to the lower thermal conductivity and limited heat capacity, forming a temperature gradient and delaying heat dissipation to the lower layer;

[0013] The establishment and dissipation of the temperature gradient are alternately used to make the vaporization driving force appear in an intermittent manner, so as to repeatedly construct thermosyphon pulses in the circulation channel and drive the working liquid to flow back and forth; by adjusting the material combination, thickness ratio and interface microstructure parameters of the upper and lower layers, the period, amplitude and stability of the thermosyphon pulses can be controlled.

[0014] Further, a local heat capacity energy storage unit is embedded in the heat exchange interface of the upper layer, the heat capacity energy storage unit delays the release after absorbing the heat flow introduced by the lower layer, and forms a temperature drop area in the release stage, which assists in realizing the attenuation process of the thermosyphon flow to promote the thermal reconstruction of the next round of burst; an intermediate interface structure with a preset thermal interface resistance is arranged between the lower layer and the upper layer, the intermediate interface structure is composed of a thermal conductivity gradient material, so as to control the transient heat flux between the upper and lower layers and realize temperature hysteresis modulation of the trigger point.

[0015] Further, a phase-changeable film is arranged on the surface of the upper layer structure of the heat exchange interface, the film absorbs heat and changes phase when reaching a threshold temperature, so as to limit the local temperature rising speed, and quickly releases heat after the phase change is completed, forming a thermal burst adjustment period window.

[0016] Further, the composite heat exchange interface is arranged in a multi-region heterogeneous structure, the material combination and thermal response time of different regions are different, respectively driving multiple local thermal siphon pulse sources to construct a multi-point driving mode staggered in time and space; the circulating channel is provided with a flow guiding structure linked with the thermal siphon cycle response, the guiding structure changes the fluid flow resistance according to different cycle stages through deformation, wettability change or steam power coupling mode, so that the inertial difference between dynamic balance leap driving and condensate backflow is caused.

[0017] Further, the siphon driving method realized in stages includes:

[0018] Adjacent thermal siphon cavities control the starting timing of each cavity by adjusting the thermal response characteristics of the evaporation area; the thermal response characteristics are adjusted and realized by the inner wall thermal conductivity or heat transfer delay structure of the evaporation area of the thermal siphon cavity; the inner wall thermal conductivity is distributed in steps between adjacent cavities, and the cavity with high thermal conductivity responds to the heat source input first to trigger the thermal siphon action; the heat transfer delay structure includes a heat insulation layer, a diffusion buffer layer or an intermediate structure with heat control characteristics between the evaporation section and the heat source, to delay local heat transfer.

[0019] Further, the evaporation area of the thermal response characteristic configuration thermal siphon cavity is integrated with a thermal trigger threshold control unit, the control unit includes a layer of thermosensitive material with critical thermal conductivity switching characteristics, used to change the thermal conductivity behavior when the preset temperature is reached, thereby delaying or advancing the thermal siphon response time of the cavity, to realize dynamic timing reconstruction at the system level.

[0020] Further, a heat flow conduction buffer zone is arranged between adjacent thermal siphon cavities, the buffer zone is based on the cooperative design of bidirectional heat diffusion material and geometric structure, to construct a nonlinear heat conduction delay effect, for adjusting the siphon trigger rhythm between cavities, to prevent unstable flow caused by synchronous driving of the system, to achieve the following time delay heat flux coupling function model for the purpose:

[0021]

[0022] Wherein:

[0023] Ψ n (t) represents the effective thermal excitation intensity transferred from the n-1th thermal siphon cavity to the nth cavity at time t; T n-1 (t-τ n ) represents the wall temperature of the previous stage cavity after a delay time τ n ; T n (t) represents the wall temperature of the current nth cavity at the current time; τ n The effective thermal delay time introduced by the heat flow buffer structure is determined by the thickness of the structure, the thermal diffusivity, the material heat capacity, α nThe adjustment coefficient determined by the internal thermal capacity of the nth cavity, the thermal inertia of the inner wall material, and the boiling point characteristics of the liquid reflects the response speed and inhibition capacity; beta n The local thermal capacity adjustment factor reflects the impedance degree of the cavity to the thermal excitation response; the function guides the excitation response in a logarithmic form inside the thermal coupling buffer, and the nonlinear characteristics make the thermal flow excitation not directly or instantaneously conducted to the next level cavity, but form a delay excitation characteristic that is automatically adjusted with temperature change, which effectively suppresses the siphon conflict or siphon breaking problem caused by synchronous siphon in the multi-stage system.

[0024] Further, the plurality of thermal siphon cavities are configured into a self-synchronous liquid cooling network through a thermal response adjustment configuration, and feedback through mutual thermal input and output under non-ideal environmental changes; the non-ideal environment is the deviation between external operating conditions and system design working conditions, including: non-uniformity of thermal load distribution, sudden increase or decrease of local heat source power, severe fluctuations of overall environmental temperature, and startup failure or response lag of thermal siphon cavities.

[0025] Further, the inner wall surface of the evaporation area is covered with a micro-patterned layer having a directional heat conduction channel structure, the channel is arranged in a vertical direction to the heat source, for strengthening the vertical concentrated conduction of heat in the priority triggered cavity, while inhibiting lateral diffusion, and optimizing the directionality and efficiency of the overall startup sequence.

[0026] The present application has the following advantages: by constructing a double-layer heat exchange interface (lower layer with high thermal conductivity, upper layer with low thermal conductivity) and introducing a thermal jump triggering mechanism, using local thermal siphon effect to realize spontaneous liquid circulation, avoiding external driving devices such as mechanical pumps and fans, improving system reliability and compactness, especially suitable for scenes with limited space and no moving parts design requirements (such as aerospace and microelectronics). The material and structure parameters in the system are adjusted to ensure that the thermal jump is triggered repeatedly at a stable pace, maintaining the pulsatile flow state in the liquid cooling channel, improving the response efficiency and flow control accuracy to periodic thermal loads, especially suitable for chip and power device heat dissipation requirements with frequent load changes. By using thermal conductivity distribution, heat transfer delay structure and thermal triggering threshold material, the thermal siphon cavities are started in a designed sequence, avoiding unstable phenomena such as jump overlap and thermal wave interference, making the liquid flow direction, condensation circuit and energy distribution have high time consistency and directionality.

[0027] Under non-ideal environment, such as sudden change of heat source power, temperature fluctuation, local failure of cavity, etc., through the heat input and output feedback mechanism between the cavities at all levels, the self-synchronization and self-reconfiguration ability of the heat siphon driven network is formed, and the stable operation ability of the system is enhanced. Through the microstructure heat conduction channel, patterned interface and heat capacity energy storage design, the heat flow conduction path and time response window are precisely controlled, the spatial and temporal double scheduling of multi-point and multi-source thermal management is realized, and the uniformity of system heat dissipation and the local hot spot control ability are improved. All key functional units are realized based on passive structure (such as micro groove, phase change film, heat conduction gradient layer, etc.), which is easy to integrate with existing chip packaging, module cooling system, has low manufacturing cost and small maintenance requirement, and is suitable for multiple application fields such as high performance computing, 5G communication, laser cooling, power converter, etc. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The main flow chart of the heat siphon assisted natural circulation multi-stage liquid cooling system of the application.

[0029] Figure 2 The functional relationship diagram of the periodic heat siphon pulse driven system of the application.

[0030] Figure 3 The progressive driving structure diagram of the multi-stage siphon liquid cooling system of the application.

[0031] Figure 4 The structure schematic diagram of the periodic heat siphon multi-stage liquid cooling system of the high performance chip of embodiment 1 of the application.

[0032] Figure 5 The schematic diagram of the three-stage heat siphon cavity series connection and multi-stage adaptive regulation of embodiment 2 of the application. DETAILED DESCRIPTION

[0033] The specific embodiments of the application will be described in detail below with reference to the accompanying drawings.

[0034] The specific embodiments of the application will be described in detail below with reference to the accompanying drawings. Figure 1The application is a thermosyphon-assisted natural circulation multi-stage liquid cooling method, which improves the performance of the natural circulation liquid cooling system in terms of start-up response speed, circulation stability, and heat-driven coordination between multi-stage systems. A double-layer heat exchange interface is set in the vicinity of the heat source, which is composed of a lower high-thermal-conductivity layer and an upper low-thermal-conductivity layer. The lower high-thermal-conductivity layer directly contacts the heat source and is used to quickly guide heat to the area where the interface contacts the working liquid. The upper low-thermal-conductivity layer is overlaid on the lower layer and is used to delay heat diffusion in the local area and form a heat temporary storage effect. Through this structural design, when the system is working, heat is first conducted to the lower layer, which makes this area heat up first and form a local high-temperature mutation area. When the temperature of the mutation area reaches the boiling threshold of the working fluid, the local liquid rapidly vaporizes and generates strong instantaneous steam drive, thereby forming a clear thermosyphon flow jump phenomenon in the thermosyphon path. The jump drives the cooling liquid to flow naturally along the set flow channel, forming a liquid circulation system without mechanical pump drive. Further, to make the thermosyphon flow jump have periodic re-triggering ability, the material thermal conductivity, specific heat capacity, thickness ratio, and surface microstructure form of the double-layer heat exchange interface are adjusted to make it first trigger evaporation jump by quickly transferring heat flow from the high-thermal-conductivity layer during heat input, then gradually release local heat accumulation from the low-thermal-conductivity layer, and promote the system temperature to quickly fall to the liquid re-condensation state after the heat input is interrupted or weakened, thereby realizing thermosyphon driving again when the heat input is restored. Through the design of heat capacity difference and heat release rhythm, the thermosyphon behavior can maintain self-driving, self-resetting, and self-reproducing ability in multiple working cycles, thereby ensuring that the entire natural circulation liquid cooling system can form a non-synchronous and staggered start-up flow rhythm based on local temperature difference changes in the multi-stage structure, improving the liquid cooling efficiency and system thermal response adjustment ability.

[0035] A plurality of distributed impedance regulation nodes are arranged in sequence on the flow path of the thermosyphon, which are used to dynamically regulate the fluid flow rate in different regions of the system, and realize the coordinated operation of rhythmized driving and multi-stage thermal regulation. The impedance regulation nodes include an expansion cavity and a capillary contraction groove arranged continuously in structure. The expansion cavity is a region with increased local fluid passage cross-sectional area, which is used to reduce the instantaneous flow rate at the node and promote the residence and heat exchange of the fluid in the region. The capillary contraction groove is a narrow structure adjacent to the expansion cavity, which is significantly smaller than the main passage in geometric size, and is used to generate capillary action and viscous resistance on the micro channel scale to form directional flow control. In operation, the arrangement of such impedance regulation nodes has position dependence and temperature responsiveness, that is, according to the arrangement position of the node on the thermosyphon path and the real-time temperature change of the region where the node is located, the flow resistance state of each node will change. When the temperature of a region rises and the thermosyphon driving force increases, the local flow rate of the corresponding node rises, and under the joint action of the expansion cavity and the contraction groove, the node will exhibit a certain flow rate suppression behavior, which leads to a flow difference between adjacent nodes. This flow difference builds a spatially non-uniform but dynamically self-balancing thermally driven channel in the multi-node system. The flow rate is faster in the high-temperature upstream region and slower in the low-temperature downstream region, thereby realizing the flow distribution regulation in the thermosyphon driving process, preventing local syphon imbalance or sudden blockage, and ensuring the ability of mutual coordination and response rhythm between multi-stage liquid cooling modules. Through the design of the distributed impedance regulation nodes, the natural circulation system has stronger thermal load adaptability and steady flow retention capability.

[0036] A plurality of thermosyphon cavities are arranged in series along the whole flow path, and the thermosyphon cavities are arranged from downstream to upstream in stages according to the arrangement direction of the heat source. Each cavity independently forms an evaporation zone and a condensation zone inside, and is filled with working liquid having different boiling point characteristics in each cavity. The boiling point of the working liquid increases from the first stage to the last stage, so that under the actual heat load, the thermosyphon cavity corresponding to the low-boiling-point working fluid is preferentially brought to the vaporization condition and starts the siphon flow, and the high-boiling-point working fluid is gradually brought to the vaporization state by the residual heat energy transferred by the previous stage cavity, thereby realizing the thermosyphon behavior triggered in stages. To further strengthen the stage difference and stability of the driving time sequence, in each adjacent thermosyphon cavity, the material of the inner wall of the evaporation zone with different thermal conductivities or the heat transfer delay structure with heat control function between the heat source and the evaporation zone is selected, so that the previous stage cavity has faster heat response capability, and the next stage cavity has relatively slower temperature rise speed due to the lower material thermal conductivity or the introduction of a heat diffusion buffer layer, so as to ensure that the system as a whole forms a stable siphon progression sequence on the time axis. The heat transfer delay structure can be an intermediate material with large heat capacity, a micro-cavity thermal insulation film, or a composite interface layer with low thermal diffusivity, which delays the heat excitation transmission of the previous stage heat to the next stage cavity, so that the heat response between the thermosyphon cavities is obviously time-displaced. In addition, since each stage of the thermosyphon cavity will cause the temperature of the local area to drop temporarily due to the heat carried away by vaporization during the working process, the design combining the boiling point layering and heat transfer control can effectively prevent the pressure difference balance failure problem caused by simultaneous start-up, thereby ensuring that the whole natural circulation liquid cooling system can maintain a clear heat driving rhythm during the start-up stage and the stable running stage.

[0037] Aiming at the problems of unstable backflow in the condensation area of the last stage thermosyphon cavity, condensate impacting the heat source area causing siphon interruption, etc., a multi-structure optimization is introduced at the condensation outlet area of the last stage thermosyphon cavity to ensure the stable closed loop of the liquid circuit. A layer of film with high liquid affinity is arranged on the inner wall surface of the first section of the condensation outlet, which is obtained by the wetting characteristics or surface energy control process of the material itself, effectively promoting the continuous and uniform liquid film flow on the wall surface after condensation instead of free dripping or aggregation. In addition, the inner wall of this area is further processed by laser etching, micro-casting or etching process to form micro-structure patterns such as micro-grooves, staggered holes or capillary grooves, so that the liquid film not only has enhanced adhesion, but also is directionally guided during flow, improving its stability and flow adhesion, avoiding liquid droplet peeling or secondary evaporation; a heat sink structure is also arranged downstream of the condensation area, which can use high heat capacity materials such as phase change material micro-pack composite layer, or micro-cavity structure with large specific surface area, its function is to actively absorb the latent heat released during condensation, and reduce the local liquid temperature, to inhibit the thermal shock and disturbance caused by supercooled liquid when falling to the next evaporation area, thereby effectively preventing sudden siphon interruption or unstable gas-liquid flow; a liquid turning buffer zone is arranged after the heat sink, which is designed by geometric space structure such as semi-annular channel, arc wall or spiral guiding groove, etc., so that the condensate completes momentum dissipation and flow direction conversion in the backflow path, further reduces the impact speed and smoothly guides the liquid to flow into the heat source area, thereby forming a continuous, gentle and controllable gravity-driven backflow channel, this closed loop path ensures that the natural circulation system has self-resetting ability and high stability during long-term operation, avoiding typical non-steady state failures such as condensate flow interruption, siphon sudden interruption or liquid bridge imbalance, etc.

[0038] Combined with the drawings Figure 2, a periodic re-triggering ability of the thermosyphon flow surge driving mechanism is constructed to improve the thermal response regulation efficiency and dynamic driving rhythm of the natural circulation system in the multi-stage liquid cooling structure. The implementation method of the mechanism includes setting a group of composite heat exchange interfaces with different thermal response characteristics in the heat source contact area, which is composed of lower and upper layer materials with obvious difference in thermal conductivity. The lower layer directly contacts the heat source, and the material thermal conductivity is significantly higher than that of the upper layer, which is used to quickly transfer the heat input by the heat source to the working liquid interface, so that the local liquid reaches the vaporization condition in a short time and quickly generates steam driving force to trigger the thermosyphon surge. At the same time, the upper layer adopts low thermal conductivity, low specific heat or high thermal resistance material to form a certain degree of heat retention effect in the heat conduction path. The retention makes the upper layer region only slowly absorb heat in the initial stage and does not participate in the vaporization process, and then retains part of the heat energy, which diffuses downward or feeds back to the system over time, thereby affecting the cooling of the lower layer or the preparation stage of the next surge. The overall process builds a periodic alternating evolution relationship of temperature gradient between the rapid heat conduction triggered vaporization of the lower layer and the slow heat release control of the upper layer, so that the vaporization driving does not occur continuously, but is intermittently started to form a thermosyphon pulse. The pulse makes the working liquid in the channel show a reciprocating driving feature, with a heat flow closed loop behavior of self-excitation-attenuation-reexcitation. To regulate the period, amplitude and stability of the thermosyphon surge, further adjust the thermal conductivity combination of the upper and lower layers, the specific heat difference, the thickness ratio of the layers, and the microstructure parameters such as interface roughness, surface microchannel, microgroove arrangement at the interface, and so on, to build a directional heat conduction path and a heat capacity difference coupling mechanism, so that the period length, steam pressure peak and trigger threshold range of the thermosyphon surge can be preset in the design stage, so that the system can maintain good dynamic heat driving rhythm under different heat load conditions, and realize self-sustaining efficient operation of the multi-stage natural circulation liquid cooling system.

[0039] The heat transfer path and timing in the composite heat exchange interface are controlled at multiple levels to build controllable thermosyphon pulse behavior and improve the cycle rhythm and dynamic response stability of the system. A heat capacity energy storage unit is embedded in the upper structure of the composite heat exchange interface. The heat capacity energy storage unit can use a material layer with high specific heat capacity or a phase change micro-coating structure, which is integrated with the upper layer through embedding, laminating or cavity filling. Its role is to actively absorb part of the heat flow and accumulate heat energy in a short time during the process of transferring heat from the heat source to the interface area in the lower heat conduction layer. Then, when the system's local heat load drops after the sudden jump process ends, the energy storage unit gradually releases the stored heat to the upper layer or the surrounding structure in a delayed manner, forming a temperature drop area during the release phase, thereby slowing down the local evaporation intensity and assisting in achieving the decay and termination of the current thermosyphon flow, ensuring that the system enters a natural decay and recovery state after the heat surge, providing transition time and spatial stability for the energy reconstruction and temperature difference formation of the next round of surge. At the same time, an intermediate interface structure is set between the lower heat conduction layer and the upper delayed layer. The interface is composed of a composite material with a controllable thermal conductivity gradient, such as a functionally graded layer constructed by varying the filling density of different thermal particles, or a multi-level material stack structure with a preset thermal interface resistance. The structure forms a discontinuous heat channel for controlling the transient heat flux between the upper and lower layers. The interface resistance not only controls the instantaneous heat transfer rate, but also adjusts the time lag characteristics of thermal excitation through its thickness, thermal directionality and interface roughness, so that the temperature conditions of the surge trigger point can be passively delayed or appropriately suppressed to enhance the response robustness and rhythm adjustment ability of the system to external thermal disturbances. Through the coupling control of the slow-release design of the heat capacity energy storage unit and the intermediate thermal resistance interface, a structural basis with a closed-loop behavior of heat excitation-delayed release-rhythm reconstruction is built, so that the thermosyphon pulse can complete the complete excitation-decay-recovery process in each cycle, thereby greatly improving the operation reliability and adaptability of the liquid cooling system under non-constant steady-state thermal load.

[0040] By actively adjusting the temperature evolution process of the heat exchange interface, the rhythm control and cycle stability improvement of the thermosyphon driving behavior are realized. A phase change film is arranged on the surface of the upper structure in the composite heat exchange interface. The film is a micro-layer of phase change material with solid-liquid or solid-solid phase change characteristics, and its thickness can be controlled between several microns and several hundred microns. The film is made of a material with low thermal conductivity and high specific heat, and is uniformly attached to the surface of the upper layer by physical evaporation, solution spin coating or laser sintering. The phase change film has a set phase change starting temperature and latent heat capacity. When the heat source continuously supplies heat to the lower layer during system operation, the temperature of the interface area gradually rises to the threshold temperature of the phase change film, and the film immediately starts to absorb heat and change phase. This process absorbs a large amount of heat but the temperature remains basically constant, thereby significantly inhibiting the further rise of the local temperature of the upper layer and effectively delaying the formation speed of the heat surge condition. The triggering process of the thermosyphon surge is changed from the original transient heat accumulation mode to the limited release mode. After the phase change process is completed, the film ends the latent heat absorption, and the heat energy absorbed by the film is quickly released to the surrounding interface under the stability of the structure, forming a temperature regulation cycle window composed of heat buffering-heat surge-heat dissipation. This cycle window makes the thermosyphon surge behavior have controllable rhythm and nonlinear start-up response characteristics, prevents the system from being over-saturated or frequently impacted by the surge due to continuous heating, and thus improves the thermal drive stability and cycle rhythm self-adaptive ability of the entire natural circulation liquid cooling system under high heat load, multi-stage heat source or pulse type heat dissipation scenarios. The selection range of the phase change film material can include paraffin modified polymer, metal organic framework coated material or nano microcapsule thermal regulation medium, and the phase change temperature and heat transfer rate are matched according to the specific temperature control range requirement, so that the present application can be flexibly adapted to different heat dissipation environments, structure layouts and working fluid characteristics, and realize the periodical regulation and cycle synchronization of the thermosyphon pulse without external control devices.

[0041] By constructing multi-region heterogeneous structure in the composite heat exchange interface and configuring flow guiding structure with synchronous response in the circulation channel, a liquid cooling system with time-space dislocation pulse driving characteristics is formed. The composite heat exchange interface is divided into multiple independent thermal response sub-regions, each sub-region adopts different material combination and structure parameters, including thermal conductivity, specific heat capacity, interface roughness and thickness configuration, so that each region has different thermal response time and vaporization starting condition. In operation, different regions show non-synchronous surge behavior due to different response speed and thermal excitation capacity when receiving the same heat load, forming multiple local thermal siphon pulse sources with time dislocation. These pulse sources start and drive the working liquid in the channel to form a multi-point driving and time staggered flow mode, thereby avoiding the centralized outbreak of heat surge or flow pulsation in the system, effectively improving the stability of circulation flow and the adjustment accuracy of thermal driving. To further coordinate the fluid inertia change brought by this multi-point driving mode and the relative lag of condensate backflow rate, flow guiding structure with periodic response synchronous linkage capability is set inside the circulation channel. The structure includes elastic flow guide sheet with shape memory function, wetting coating responding to temperature change, or micro valve type structure device driven by vapor pressure difference. Its role is to adjust the flow resistance of the local channel according to the vapor driving strength and condensate quantity change in each stage during the thermal siphon surge period. When the heat surge is excited, the guiding structure is in low resistance on-state, which enhances the liquid flow efficiency. In the condensate backflow stage, it switches to high resistance or variable wetting state, which suppresses the condensate backflow disturbance and improves the system flow rhythm matching degree. Through the cooperation of the above multi-region heterogeneous heat exchange structure and the periodic response guiding structure, a multi-stage liquid cooling system is realized, which constructs distributed thermal driving source in space and forms controllable pulse rhythm complex heat flow network in time.

[0042] The drawings are attached Figure 3, a step-by-step siphon driving method is used to solve the problems of timing disorder, driving conflict or siphon failure of multi-stage thermosyphon cavities in natural circulation liquid cooling systems during startup. By designing evaporation zone structures with differentiated thermal response characteristics between adjacent thermosyphon cavities, the system has the ability to time-lapse the thermal drive trigger. The thermal response characteristics are adjusted and controlled by the thermal conductivity of the evaporation zone inner wall or the heat transfer delay structure, wherein the thermal conductivity design follows the principle of step distribution, that is, the thermal conductivity of the material used by the inner wall of the evaporation zone of the adjacent thermosyphon cavity arranged along the heat source direction is sequentially decreased. The high thermal conductivity cavity can transfer heat to the working fluid interface faster, thus responding to the heat source input and triggering the thermosyphon jump action first, while the low thermal conductivity cavity responds slowly, realizing the spatial time-lapse of the trigger sequence. Further, to enhance the control accuracy and stability of heat transfer rate, a heat transfer delay structure is introduced in some cavities. The structure is arranged between the evaporation section and the heat source to suppress transient heat input and delay local temperature rise. The structure includes a low-thermal-conductivity insulation layer to reduce heat flux per unit time; it can also include a diffusion buffer layer made of high specific heat or low diffusion coefficient material to temporarily store and slowly release heat while keeping the heat channel open; in addition, an intermediate structure with heat control characteristics can also be configured, which forms a relatively adjustable thermal resistance barrier on the heat flow path through functional gradient materials or discontinuous heat channel design, so that heat needs to be transmitted to the evaporation section through a longer path or more complex interface to achieve the purpose of delayed activation. Combined with the gradient configuration of thermal conductivity and the heat transfer path adjustment structure, the entire multi-stage thermosyphon system is activated in the preset startup sequence under the condition of continuous heating of the heat source. Each cavity generates a steam driving force to push the cooling liquid to flow and guide the heat to the next stage cavity after startup, until all cavities complete the sequential startup, building a siphon flow chain with clear rhythm and driving direction, avoiding the problems of pressure difference offset, steam conflict and fluid disturbance caused by simultaneous startup of traditional multi-stage natural circulation systems.

[0043] By regulating the thermal response characteristics of the evaporation zone of each thermal siphon cavity, the dynamic timing reconstruction of the system during the thermal drive process is achieved to avoid the driving conflict and cycle instability problems caused by the simultaneous start-up of multiple cavities. A thermal trigger threshold control unit is integrated in the evaporation zone of the thermal siphon cavity. The control unit includes a layer of thermosensitive material with critical thermal conductivity switching characteristics. The material can be a thermotropic polymer, a reversible phase change composite, or a nanocomposite coating with temperature-sensitive interface reconstruction capabilities. The thermosensitive material maintains a low thermal conductivity state before reaching the preset temperature threshold, effectively inhibiting the conduction of heat from the heat source to the working liquid interface, thereby delaying the start-up time of evaporation and thermal siphon jump. When the temperature in the area where the cavity is located gradually increases and reaches the set critical point, the internal molecular structure of the material undergoes physical rearrangement or phase reconfiguration. The thermal conductivity path is activated or reconstructed instantly, showing a significantly increased thermal conductivity, which allows heat to be quickly transferred to the liquid interface, inducing vaporization behavior and triggering thermal siphon flow. By utilizing this critical thermal conductivity switching mechanism, each thermal siphon cavity can independently complete the dynamic adjustment of the thermal response timing according to the actual temperature rise rate and the load conditions of the hot zone where it is located. Furthermore, by adjusting the phase change temperature, thickness, thermal conductivity switching slope and surface contact mode of the thermosensitive materials in different cavities, the response time window to thermal excitation can be accurately distributed, thereby realizing the transformation of the overall system from static cascade triggering to dynamic rhythm response mode.

[0044] To address the problems of flow instability, pressure difference interference, and drive conflict caused by the synchronous response of multi-stage thermosiphon cavities to thermal loads during operation, a heat flow conduction buffer zone located between adjacent thermosiphon cavities is designed. It is constructed by using bidirectional heat diffusion materials and asymmetric geometric structures. Its function is to construct a type of heat transfer path with nonlinear thermal delay characteristics, thereby actively adjusting the heat transfer timing between the upper and lower cavities and realizing dynamic regulation of the siphon triggering rhythm. The buffer zone differentiates the heat propagation speed in space through the thermal anisotropy of the material itself. At the same time, combined with microstructured channels, extended cavities, or multi-layer interface designs, a hysteresis response mechanism of heat transfer is established on a time scale. In the thermal behavior model, the following time-delayed heat flux coupling function model is established to describe the dynamic regulation law of this process:

[0045]

[0046] where Ψ n (t) is the effective thermal excitation intensity transferred from the n-1th thermosiphon cavity to the nth cavity at time t, reflecting the degree of effect of thermal excitation on the evaporation zone of the lower cavity, T n-1 (t-τ n ) indicates that the previous stage cavity has passed the delay time τ n The wall temperature after nβ is the effective thermal delay time introduced by the buffer zone, which is determined by the structural thickness, material thermal diffusivity and unit volume heat capacity, n α is the local heat capacity adjustment factor of the current nth cavity, which represents the response strength and inhibition ability of the cavity to heat input, n β is the coupling adjustment coefficient, which is set by combining the heat capacity of the cavity itself, the thermal inertia of the inner wall material and the latent heat characteristics of the working liquid used, and is used to measure the thermal excitation sensitivity required before the start of the lower level cavity. The function controls the excitation conduction in the thermal coupling buffer zone in a logarithmic form, and the nonlinear expression structure makes the heat flow response not linear or instantaneous transmission, but presents obvious hysteresis, stage and dynamic adjustment characteristics. In the working process, even if the current level cavity has completed the vaporization jump, the heat needs to gradually affect the next level cavity after the lag time and response threshold determined by the buffer zone, so as to form a time staggered siphon driven wave in the system, avoid the problem of thermal shock, steam pressure difference superposition or backflow wave interference caused by the simultaneous start of multiple cavities, and finally realize the highly ordered heat driven pulse transmission and flow stability protection of the whole natural circulation system on the basis of not relying on external control elements.

[0047] A plurality of thermal siphon cavities are constructed into a liquid cooling network with self-synchronization capability through a thermal response adjustment mechanism, so that the system not only realizes multi-point cascade of heat driven in the running process, but also has the function of self-adaptive recovery of thermal adjustment when non-ideal environmental changes occur. Through the difference design of structural materials, heat conduction interface, heat capacity distribution and starting threshold, multiple thermal siphon cavities form a thermal response configuration that can respond to different temperature zones, load intensity and time rhythm. In the working process, each cavity establishes a local thermal-flow feedback relationship through heat exchange between the evaporation section and the condensation section, gas-liquid driving force conversion and thermal diffusion process. When a cavity completes the thermal siphon jump and releases heat, the heat will diffuse to the adjacent cavity through the heat conduction path or the gas-liquid channel, providing thermal excitation or transferring thermal disturbance to the adjacent cavity, thereby triggering the response of the next level or lateral cavity. This mechanism forms an orderly cascade triggering mode when the system runs smoothly, and when non-ideal environmental conditions occur, such as slow temperature rise in a region due to non-uniform heat load distribution, or power surge or sudden drop of a local heat source, or dramatic fluctuations in the overall environmental temperature of the system, or some thermal siphon cavities fail to start at the preset rhythm due to local working fluid state, structural defects or response disorder, other thermal siphon cavities in the system can actively compensate for the driving force or rhythm gap of the failed part through thermal diffusion enhancement, self-lag response adjustment or thermal coupling effect on external feedback signals, thereby rebuilding the liquid flow path and heat driven rhythm at the system level, realizing dynamic time sequence reorganization and energy redistribution, and ensuring the continuous closed-loop operation of natural circulation. The self-synchronization mechanism does not require external sensing and control devices, and only relies on the physical thermal-flow feedback process between cavities to realize the coupling and coordination of overall behavior.

[0048] The controllability of the heat-driving path and the spatial accuracy of the startup sequence are enhanced by optimizing the heat-conducting directional structure of the inner wall of the evaporation zone. A micro-patterned layer with a directional heat-conducting channel structure is covered on the inner wall surface of the evaporation zone of each thermal siphon cavity. The patterned layer is formed into an array of microstructures on the surface of the metal or composite material using processes such as micro-nano processing, laser etching, hot pressing transfer or plasma etching. Its geometric morphology may include strip grooves, ridge-like protrusions, heat-conducting bridges or longitudinally symmetrical ribs. The channel structure is arranged in a longitudinal direction perpendicular to the main heat transfer direction of the heat source, extending from the bottom of the heat source to the depth of the evaporation area inside the cavity. Its function is to establish a set of controlled heat flow main channels so that the heat input from the heat source is preferentially transferred quickly along the set direction to the thermal siphon cavity with higher thermal conductivity or thermal response priority in that direction, and is not easily transferred to the side or non-target direction. Regional diffusion. On the one hand, this design significantly improves the thermal excitation efficiency of the target cavity, enabling it to achieve thermal siphon jump triggering earlier with a smaller heat input rate. On the other hand, by suppressing lateral heat diffusion, it avoids the non-target cavity from receiving heat too early, resulting in disordered startup sequence or response overlap, thereby optimizing the directionality and controllability of the startup sequence of the multi-stage thermal siphon cavity, so that the entire liquid cooling system has a clearer thermal drive path planning capability and more efficient energy distribution rhythm control. The micro-patterned thermal conductive structure can be customized in shape, arrangement density and pattern period according to the specific heat load characteristics, and a partition change strategy can be adopted in different levels of cavities to further construct a thermal conduction network with directional guidance function.

[0049] Example 1:

[0050] Combined with attachment Figure 4 This embodiment is based on a high-performance computing chip cooling application scenario. For an AI acceleration chip with a package power of 180W, the local heat flux density in the core area can reach 100W / cm during full-load computing. 2, the start-up delay is obvious and the flow rate fluctuation is large, and the dynamic response to the rapid thermal pulse cannot be realized. The periodic thermosyphon jump structure is applied to the main heat exchange interface, and a 20mmx20mm composite heat exchange structure is arranged at the top of the chip. The structure is composed of a lower layer of pure copper sheet (thermal conductivity k1≈390W / m·K) and an upper layer of porous aluminum oxide coating (thermal conductivity k2≈3W / m·K). The lower layer is 1.0mm thick and is used to quickly guide the heat of the heat source to the liquid interface, while the upper layer is 0.5mm thick and has certain heat release capacity and heat capacity delay characteristics. The working liquid is selected as a low-boiling medium HFE-7100 with a boiling point of 61℃. It is found that the chip surface temperature rises to 70℃ within 30 seconds of operation. At this time, the copper layer quickly guides the heat into the liquid contact interface, forming strong local vaporization and promoting the occurrence of siphon flow jump. With the vaporization of the bubbles and the removal of heat, the heat storage of the upper aluminum oxide layer is gradually released, so that the interface temperature falls below 65℃ for a short time, and the liquid is re-condensed. This process completes a complete jump-attenuation-recovery cycle. Through the high-speed thermal imager and micro-flow rate sensor linkage monitoring data, it is found that the structure realizes an average of one complete thermosyphon pulse every 12.8 seconds, which can drive the cooling liquid to form a 2.4cm / s pulsating flow rate in a 2mm inner diameter channel. Subsequently, the structure parameters are optimized, and the thickness of the aluminum oxide layer is adjusted to 0.8mm, and the jump period is extended to 18 seconds, and the pulse flow rate is reduced to 1.7cm / s. It is verified that the thickness and thermal conductivity of the upper structure directly affect the jump rhythm and driving strength, and further introduces a micro-groove structure (depth 20μm, pitch 60μm) at the interface, the thermosyphon jump trigger delay time is shortened by about 17%, the overall flow pulse is more stable, and the temperature fluctuation is reduced from ±3.4℃ to ±1.1℃, which shows that the microstructure strengthens the local nucleation control ability and jump trigger sensitivity of the liquid. Finally, the system maintains an average jump frequency of 4.7 times per minute within 90 minutes of operation, without any thermosyphon interruption or liquid bridge interference phenomenon.

[0051] To further verify the self-adaptive regulation ability of the thermosyphon-assisted natural circulation multi-stage liquid cooling method under high dynamic heat load conditions, the composite heat exchange interface used in the previous stage test was upgraded in structure and function. A complete multi-point heat-driven, time-triggered, self-regulating flow closed-loop system was constructed by integrating local thermal capacity energy storage units, thermal interface resistance structures, phase change films, regional heterogeneous thermal conduction systems, and flow direction control modules. Several thermal capacity energy storage unit cavities with a diameter of 1.5 mm and a depth of 0.3 mm were opened in the upper layer of aluminum oxide, and were filled with paraffin-based energy storage material with a specific heat capacity of 2.9 J / g·K. The melting temperature was set to 64.5°C, slightly higher than the boiling point of HFE-7100. Through this design, local heat flow was absorbed synchronously during the sudden trigger stage, and heat was slowly released after vaporization to assist in forming a condensation and decay zone. Infrared testing showed that this design increased the wall cooling rate after the sudden end from 4.2°C / s to 6.8°C / s, effectively shortening the re-sudden preparation time by about 15%. A thermal conductivity gradient structure was introduced between the copper and the aluminum oxide, consisting of three layers of composite interface material with thermal conductivities of 150 W / m·K, 40 W / m·K, and 8 W / m·K, respectively. The thickness of each layer was controlled to be within 0.2 mm. Through this intermediate interface resistance structure, nonlinear regulation of transient heat flux before the sudden trigger was achieved, reducing the risk of synchronous driving caused by sudden response too quickly. Testing showed that this structure lengthened the minimum interval between multiple-point surges from 1.7 seconds to 3.4 seconds, significantly reducing heat-driven interference and improving fluid steady-state distribution.

[0052] A 120μm-thick phase-change composite film is further sprayed onto the surface of this structure. The material is polyethylene glycol coated with nanosilver particles. It has a melting point of approximately 62°C and a latent heat of phase change of approximately 160J / g. It absorbs heat at the critical point of temperature rise before the thermal jump, effectively passivating the local temperature rise slope and controlling the synchronization of the thermal jump. In actual measurements, it was found that the wall temperature rise rate can be reduced from 2.6°C per second to 1.1°C per second within a complete phase change cycle, controlling the thermal trigger window to fluctuate between 6 and 10 seconds, and improving cycle stability. To address the problems of uneven chip heat source distribution and dynamic changes in power density, the entire heat exchange interface is designed as a four-zone heterogeneous structure. The high thermal conductivity and high response material (copper + phase-change polymer composite layer) is configured near the core processor heat source, while the peripheral area away from the core adopts a medium thermal conductivity and low heat capacity structure (graphite / ceramic composite). Each zone forms an independent micro-thermosiphon cavity, each with a different start threshold and energy storage structure, forming multiple point jumps staggered in time and space, ultimately forming a stable A specific thermal drive wave train is recorded by an array of micro-thermal flow sensors. When the power fluctuation frequency is 0.2 Hz, the system adaptively adjusts the response cycle to maintain the chip surface temperature difference within ±1.4°C. Furthermore, shape-memory guide vanes are embedded throughout the liquid circuit channel. Driven by the steam pulse during the sudden burst phase, these vanes bend along the flow direction to reduce local flow resistance. After the sudden burst, during the condensation and reflow phase, the temperature drops and the vanes gradually return to their original shape, resulting in a periodic change in flow resistance. Furthermore, an intelligent wetting switching coating is applied at key reflow corners, with a contact angle that switches between 88° and 42° with temperature. This allows the condensate to flow more easily along the wall during the non-sudden burst phase, forming a stable liquid film. These structures work together to form a complete thermal management network with temporal regulation, spatial coordination, self-recovery of the drive rhythm, and closed-loop coupling of the condensation and reflow circuits. During a 72-minute pulsed heat load test, an average sudden burst frequency of 5.2 times / minute, a chip surface thermal gradient of less than 1.6°C, and no significant siphon interruption or liquid bridge imbalance were achieved.

[0053] Example 2:

[0054] Combined with attachment Figure 5, based on example 1, a natural circulation experimental platform with a three-stage thermosyphon cavity series structure is further constructed to simulate the gradient heat response driving process under multi-stage heat source distribution. The experimental platform is based on the heat load characteristics of the high-density computing unit arranged in a zonal manner in the actual application scenario. Three heat source regions (named ZoneA, ZoneB, and ZoneC) are respectively arranged equidistantly on the chip surface, with powers of 80 W, 60 W, and 40 W, respectively. The total heating area is 3 cm x 8 cm. Three groups of thermosyphon cavities are used for correspondence in sequence. Each group of cavities is filled with the same low-temperature medium HFE-7100 with a boiling point of 61°C. However, different heat response characteristics are formed through structural differences. The first cavity corresponding to ZoneA uses a pure copper evaporation wall (thermal conductivity of about 390 W / m·K) with a thickness of 0.5 mm and no heat transfer delay structure. The second cavity corresponding to ZoneB uses a copper-aluminum composite inner wall (equivalent thermal conductivity of about 160 W / m·K), and a layer of silica gel-based thermal insulation layer with a thickness of 0.3 mm and a thermal conductivity of 0.15 W / m·K is embedded between the evaporation area and the heat source. The third cavity corresponding to ZoneC uses a stainless steel evaporation wall (thermal conductivity of about 16 W / m·K) and a 0.5 mm low-thermal-diffusion porous ceramic buffer layer, which forms the strongest delay unit in the heat transfer path. The three cavities are connected in series through a gravity circuit, and the condenser shares an integrated water cooling plate device. By applying heat load and conducting synchronous monitoring of thermal infrared and thermocouple, at the initial stage of chip operation, when the system temperature rises to about 65°C, the ZoneA cavity responds first, the liquid starts to vaporize and forms a steam jump, and the system generates a primary siphon flow. As the ZoneA steam carries away part of the heat, the temperature of the ZoneB region rises to about 66.5°C, which is the critical temperature. Due to the reduced thermal conductivity of the inner wall and the presence of the thermal insulation layer, the thermal response of ZoneB lags behind ZoneA by about 13.2 seconds. After ZoneB is triggered, the heat drive is further strengthened. ZoneC takes a longer time to reach the vaporization threshold due to the presence of the ceramic buffer layer, with a total trigger delay of about 28.7 seconds. It is precisely measured that the siphon start time interval of each stage is controlled between 10-30 seconds, and the liquid flow rate increases in a stepwise pulsatile manner from 0.5 cm / s to 1.9 cm / s. In addition, by adjusting the thickness of the buffer layer of ZoneC from 0.5 mm to 0.3 mm, it is observed that the start delay is shortened to 21.4 seconds, and the siphon formation time is significantly advanced, indicating that the structure has a clear heat transfer response regulation capability. Finally, the system runs continuously for 80 minutes, maintains a stable cascade trigger sequence in multiple heat load change cycles, and the chip surface temperature fluctuation range is controlled within ±1.7°C, with good heat drive synchronization and no jump overlap phenomenon.

[0055] On the basis of the aforementioned three-stage thermosyphon cascade liquid cooling experimental platform, in order to further improve the time sequence adaptive ability of the multi-stage liquid cooling system in the process of dynamic change of heat load, a heat trigger threshold control unit with critical heat conduction switching characteristics is integrated in the evaporation area of each thermosyphon cavity to realize the reconstruction control of the system level dynamic heat response time sequence. The evaporation surfaces of ZoneA, ZoneB and ZoneC are respectively introduced with a 200μm thick heat sensitive heat conduction material coating. The heat sensitive layer adopts a graphene / polymer composite phase change substrate. The material thermal conductivity remains at 1.2W / m·K below 40℃. When the preset trigger temperature (58℃ for ZoneA, 64℃ for ZoneB and 68℃ for ZoneC) is reached, due to the thermal induced phase change or chain segment relaxation of the substrate polymer, the thermal conductivity can quickly jump to 6.4W / m·K within 2 seconds, thereby improving the local heat response speed of the evaporation area and starting the thermosyphon jump.

[0056] The experimental data show that in the initial stage, ZoneA realizes the sudden increase of heat conduction first due to the lower trigger temperature of the heat sensitive layer. Bubble aggregation and vaporization jump occur in ZoneA first at the 15th second after the power load is started, and the thermosyphon drive is formed, which drives the liquid backflow in the condensation area. In this process, the heat sensitive layer of ZoneB is in the untriggered state and still maintains the low heat conduction buffer stage, so that the heat transfer is delayed for about 6.3 seconds. When the temperature of the evaporation surface of ZoneB reaches 64℃, the thermal conductivity jumps, the thermosyphon starts and cooperates with ZoneA, and the heat response of ZoneC is the latest. Finally, the heat conduction switching is triggered at the 43rd second due to the continuous heat transfer, thereby forming a complete three-stage thermosyphon cascade jump process. Compared with the control group without integrating the heat sensitive regulation unit, the average jump start sequence of the cavities in the system maintains a consistency deviation of less than ±1.8 seconds, and maintains high repeatability and stability in multiple cycles of heat load rising-stable-falling. In order to further evaluate the adjustability of the heat sensitive material, another heat induced material with a higher response slope is used in ZoneB cavity, and the heat conduction jump time is shortened to 1 second. The results show that the trigger point of ZoneB is moved to the 21st second, which is closer to ZoneA in advance, and the overall thermosyphon jump interval of the system is shortened from the original 15 seconds to 8.9 seconds. However, the trigger lag time of ZoneC does not change, and the system appears a round of jump overlap phenomenon, indicating that the response window of the heat sensitive material must be matched with the system thermal inertia, working medium characteristics and jump maintenance time, otherwise it will cause jump competition or uneven heat flow. Finally, under the condition of setting different response thresholds and slopes for the three groups of heat sensitive layer materials, the system can actively adjust the start sequence and trigger rhythm of each cavity according to the actual heat load distribution, realize the transition from fixed stage to dynamic reconstruction, and successfully realize the reverse conversion of the cavity response sequence in the reverse kick scenario of the simulated heat source from ZoneC to ZoneA.

[0057] Further introduce the heat flow conduction buffer structure, for precise control of the adjacent cavity between the heat driven rhythm, avoid the system in the heat load suddenly or non-uniform conduction conditions under the problem of synchronous siphon, especially when the multi-stage structure close to the threshold of vaporization at the same time, if not to intervene easily lead to siphon drive wave superposition, steam collision and flow disorder. By setting between the n-1 and n level heat siphon cavity by bidirectional thermal diffusion material (such as graphene / polymer heterogeneous composite material) and nonlinear geometric structure (such as tapered microcavity, spiral channel or depth groove buffer cavity) together constitute a thermal buffer structure unit, in the structure of physical layer on the introduction of clear thermal response lag, build a kind of with time delay response characteristics of thermal excitation transmission mechanism.

[0058] In order to quantitatively analyze the thermal buffer effect, the system uses the following nonlinear coupling function for dynamic simulation and verification:

[0059]

[0060] In this model, the following parameter range and experimental instance data are set:

[0061] Thermal delay time τ n : In this experimental platform, the buffer zone thickness is 1.2mm, the composite material thermal diffusivity is about 1.8×10 -6 m 2 / s, the material unit volume heat capacity is about 1.4×10 6 J / m 3 ·K, after the empirical conversion, the effective thermal delay τ n ≈7.5~12 seconds is obtained.

[0062] Adjustment coefficient α n : related to the thermal capacity C th of the n cavity, the internal wall material thermal inertia I m , the liquid boiling point T b , in the experiment, the second cavity adopts aluminum alloy inner wall, and the working medium is HFE-7100 (boiling point 61℃), the value range α n =0.85~1.6.

[0063] Local impedance factor β n : reflects the inhibition ability of the cavity thermal inertia, which depends on its condensation efficiency, flow channel geometry and structure thermal capacity, the range β n =0.015~0.09.

[0064] In the test, after the chip ZoneA completes the jump, the wall temperature T n-1 (t-τ n ) reaches 70℃, after 9.5 seconds of thermal buffer delay, the wall temperature of ZoneB is 60.2℃, and the model calculation is as follows:

[0065]

[0066] At this time, the system considers that Ψ2(t) > 7.5 is a trigger threshold, the second cavity starts a jump and forms a second level siphon wave, and the progressive start is completed. Compared with the traditional direct heat conduction system, the siphon jump coincidence rate of Zone A and Zone B is more than 60% under the same heat load, and the coincidence probability is reduced to <10% after using the buffer structure, which greatly reduces the fluid shock and reflux interference phenomenon caused by the synchronization of the jump.

[0067] Further verify the nonlinear regulation characteristics of the function, set a higher impedance factor β3 = 0.08 in Zone C, and increase the buffer layer thickness to 1.8 mm, form τ3 = 13.6 seconds delay, test shows that Zone C start time is delayed to the 42nd second, compared with Zone B, it is delayed by nearly 14 seconds, effectively realizing the sequential start reconstruction in the reverse excitation environment, when the chip heat load changes (local heat burst of Zone C), the system can still maintain the siphon response of the rhythm misplacement, thereby maintaining the stable flow rate of the cooling channel.

[0068] In summary, the thermal buffer structure not only realizes the time delay filtering function of the heat driven rhythm through physical means, and the coupling model Ψ n (t) can be realized by parameterized adjustment to achieve engineering-level dynamic scheduling for different chip load structures and heat diffusion characteristics, without external control logic, it can realize multiple target control such as heat pulse modulation, siphon drive delay, jump decoupling, etc. in the system, suitable for multi-chip heterogeneous cooling, high-speed pulse load thermal management and adaptive liquid cooling system architecture design.

[0069] Further improve the robustness and self-organizing thermal regulation ability of the system in non-ideal operating environment, introduce thermal response adjustment configuration to constitute a dual design strategy of self-synchronous liquid cooling network and directional heat conduction channel micro patterning layer, and establish an intelligent cascaded liquid cooling system with high thermal coupling feedback ability. In this experimental platform, three thermal siphon cavities (Zone A, B, C) are respectively covered on different heat source regions of the AI chip array, and the chips will generate different levels and different positions of heat flux input according to task allocation during operation. The initial start priority is set as Zone A > Zone B > Zone C through the difference in thermal conductivity, thermal delay structure and phase change material at the initial design stage of the system.

[0070] To cope with non-ideal environment, such as local heat source power surge or ZoneB cavity heat transfer failure, the system introduces a directional heat conduction channel micro-patterning layer in the inner wall of each cavity evaporation surface. The pattern adopts a longitudinal micro-slot array structure with a width of 40 μm, a depth of 20 μm, and a pitch of 60 μm, which is prepared on the surface of a high thermal conductivity silicon substrate by plasma etching. The micro-channel is perpendicular to the chip heat surface to enhance the ability of heat conduction from the chip core area to the liquid interface, and significantly inhibit the heat from spreading horizontally to the cavity, forming a clear heat guide line mechanism. The thermal infrared test results show that ZoneA's temperature rise rate increases by 23.4% when the power input is 80W and the environmental temperature rises by 3℃ (from 25℃ to 28℃), and after the surge, part of the heat is transferred to the untriggered ZoneB area through the guide structure, and the evaporation area of ZoneB is successfully activated within 2.8 seconds after the heat resistance of ZoneB occurs. The following control coupling index modeling verification is set:

[0071] ZoneA's heat input is Q A = 80 W , and the conduction efficiency of the heat transferred through the patterned conduction structure after the surge is increased to 63.2%,

[0072] Under the condition that the heat resistance of ZoneB increases (α B drops to 0.7), the traditional system cannot form an effective steam drive in ZoneB due to the lack of cross-cavity heat input compensation,

[0073] But in the presence of the conduction structure, ZoneB receives the transferred excitation from ZoneA, which exceeds the threshold of 4.7, successfully triggers the local vaporization response, and the system realizes self-synchronous siphon reconstruction.

[0074] Further, in a non-ideal fluctuation simulation, the experiment suddenly applies a heat load to the ZoneC area (power increases from the original 40W to 60W), and the test finds that the system can complete the driving rhythm reversal within 9 seconds: ZoneC reaches the critical trigger temperature of the heat conduction pattern layer (67℃) first, and the conduction efficiency jumps from the initial 41% to 69%, the system heat surge starts from bottom to top, and ZoneB and ZoneA are activated, so that the system completes the heat response order reconstruction from ZoneA>B>C to ZoneC>B>A.

[0075] The method of the present application can still rely on the micro heat channel design and the local heat input and output coupling to establish an adaptive coordination strategy under the condition of multi-heat-source nonlinear disturbance, forming a heat-driven synchronous network without external control. This mechanism not only improves the starting rhythm adjustment capability, but also enhances the anti-impact and thermal self-recovery capability of the system in real working conditions such as heat siphon interruption, local failure of the cavity, and environmental thermal drift.

[0076] The basic principles, main features and advantages of the present application are shown and described above. Those skilled in the art should understand that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. Thermosyphon assisted natural circulation multi-stage liquid cooling method, characterized in that include: A double-layer heat exchange interface consisting of a lower high-thermal conductivity layer and an upper low-thermal conductivity layer is set in the vicinity of the heat source to form a local temperature rise mutation zone. When the temperature in the mutation zone reaches the boiling threshold of the working liquid, a local thermosiphon flow jump is generated to drive liquid circulation. By adjusting the material and structural parameters of the double-layer heat exchange interface, the thermosiphon flow jump has the ability to be periodically retriggered. A plurality of distributed impedance control nodes are sequentially arranged along the flow path of the thermosiphon, each impedance control node including an expansion cavity and a capillary contraction groove, for adjusting the flow rate of the fluid passing through the node according to the node position and real-time temperature, thereby establishing a flow difference between adjacent nodes; Multiple stages of thermosiphon cavities are arranged in series on the flow path, each stage of the thermosiphon cavity is filled with a working liquid with successively increasing boiling points, and the start-up timing of adjacent thermosiphon cavities is matched by selecting different inner wall thermal conductivities or setting a heat transfer delay structure to achieve progressive siphon drive; A lyophilic membrane layer and a microstructured wall are set in the condensation outlet area of ​​the last-stage thermal siphon cavity to allow the condensate to adhere and flow smoothly in the form of a liquid film; a heat sink material or a microcavity structure is set in the condensation outlet area to absorb part of the latent heat of condensation and suppress the impact of supercooled liquid; and a liquid turning buffer zone is set after the condensation outlet to guide the condensate to a gentle reflux path, completing a closed-loop natural circulation.

2. The thermosiphon-assisted natural circulation multi-stage liquid cooling method according to claim 1, characterized in that The method for constructing the thermosiphon flow jump with periodic re-triggering capability includes: A composite heat exchange interface consisting of a lower layer and an upper layer with significantly different thermal conductivities is provided in the heat source contact area, wherein the thermal conductivity of the lower layer is higher than that of the upper layer; the lower layer quickly transfers heat to the working fluid, causing the local working fluid to reach vaporization conditions and generate steam driving force; the upper layer retains heat due to its lower thermal conductivity and limited heat capacity, forming a temperature gradient and delaying heat dissipation to the lower layer; Through the alternating effects of establishing and dissipating the temperature gradient, the vaporization driving force appears intermittently, thereby repeatedly constructing thermal siphon pulses in the circulation channel, driving the working liquid to flow back and forth; by adjusting the material combination, thickness ratio and interface microstructure parameters of the upper and lower layers, the period, amplitude and stability of the thermal siphon pulses can be controlled.

3. The thermosiphon-assisted natural circulation multi-stage liquid cooling method according to claim 2, characterized in that A local heat capacity energy storage unit is embedded in the heat exchange interface of the upper layer. The heat capacity energy storage unit delays the release after absorbing the heat flow introduced by the lower layer, and forms a temperature drop zone during the release phase, thereby assisting in the attenuation process of the thermal siphon flow to promote the thermal reconstruction of the next round of sudden jump. An intermediate interface structure with a preset thermal interface resistance is provided between the lower layer and the upper layer. The intermediate interface structure is composed of a thermal conductivity gradient material to control the transient heat flux between the upper and lower layers and realize the temperature hysteresis modulation of the trigger point.

4. The thermosiphon-assisted natural circulation multi-stage liquid cooling method according to claim 3, characterized in that A phase-changeable film is provided on the surface of the upper structure of the heat exchange interface. The film absorbs heat and changes phase when the threshold temperature is reached to limit the local temperature rise rate, and quickly releases heat after the phase change is completed to form a thermal jump regulation cycle window.

5. The thermosiphon-assisted natural circulation multi-stage liquid cooling method according to claim 4, characterized in that The composite heat exchange interface is configured as a multi-region heterogeneous structure, with different regions having different material combinations and thermal response times, which drive multiple local thermosiphon pulse sources to construct a multi-point driving mode staggered in time and space; A flow guide structure is provided in the circulation channel, which is synchronously linked with the thermosiphon cycle response. The guide structure changes the fluid flow resistance according to different cycle stages through deformation, wettability change or steam dynamic coupling, so as to dynamically balance the inertia difference between the sudden jump drive and the condensation reflux.

6. The thermosiphon-assisted natural circulation multi-stage liquid cooling method according to claim 1, characterized in that The step-by-step siphon driving method includes: Adjacent thermosiphon cavities control the startup timing of each cavity by adjusting the thermal response characteristics of the evaporation zone; the thermal response characteristics are achieved by adjusting the thermal conductivity of the inner wall of the evaporation zone of the thermosiphon cavity or the heat transfer delay structure; the thermal conductivity of the inner wall is distributed in a stepped manner between adjacent cavities, and the cavity with high thermal conductivity preferentially responds to the heat source input to trigger the thermosiphon action; the heat transfer delay structure includes an insulating layer, a diffusion buffer layer or an intermediate structure with heat control characteristics located between the evaporation section and the heat source, which is used to delay local heat transfer.

7. The thermosiphon-assisted natural circulation multi-stage liquid cooling method according to claim 6, characterized in that The evaporation zone of the thermosiphon cavity is integrated with a thermal trigger threshold control unit, which includes a layer of thermosensitive material with critical thermal conductivity switching characteristics, which is used to change the thermal conductivity behavior when the preset temperature is reached.

8. The thermosiphon-assisted natural circulation multi-stage liquid cooling method according to claim 7, characterized in that A heat conduction buffer zone is provided between adjacent thermosiphon cavities. The buffer zone is made of bidirectional heat diffusion material and forms a thermal coupling delay through geometric structure design, so that the heat output of the previous stage cavity affects the next stage cavity only after a time delay.

9. The thermosiphon-assisted natural circulation multi-stage liquid cooling method according to claim 8, characterized in that The plurality of thermosyphon cavities are configured to form a self-synchronous liquid cooling network through thermal response adjustment, and feedback is provided between the thermal input and output under non-ideal environmental changes; The non-ideal environment is the deviation between the external operating conditions and the system design conditions, including: non-uniform heat load distribution, sudden increase or decrease in local heat source power, drastic fluctuations in the overall ambient temperature, and failure to start the thermosiphon cavity or delayed response.

10. The thermosiphon-assisted natural circulation multi-stage liquid cooling method according to claim 9, characterized in that The inner wall surface of the evaporation zone is covered with a micro-patterned layer having a directional heat conduction channel structure. The channels are arranged in a direction perpendicular to the heat source to enhance the longitudinal concentrated conduction of heat in the priority trigger cavity while suppressing lateral diffusion, thereby optimizing the directionality and efficiency of the overall startup sequence.

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