A passive thermal management device and method based on rigid geometric contour constraints natural air pockets

Abstract

This invention belongs to the field of passive thermal management technology, specifically relating to a passive thermal management device and method based on rigid geometric contour constraint of natural cavitation. The device includes a first rigid component and a second rigid component, which are positioned opposite each other to form a controllable micro-gap of 0.02 mm to 0.20 mm. A rigid geometric cavitation coupling part is integrally formed on the mating surface, and its rigid geometric contour is one of gradient steps, wedge constraints, circular arc limits, or planar constraints. When the heat exchange fluid flows through the micro-gap, it depressurizes and vaporizes to form a natural cavitation. Constrained by the rigid contour, the fluid undergoes phase change evolution and gas-liquid interface displacement, adaptively adjusting the effective flow cross-sectional area according to fluid temperature changes, thus achieving passive heat flow regulation. The device has no elastic thermistor, moving valve core, or electrical control unit, is applicable to temperatures from -40℃ to 120℃, and is manufactured using an integral molding process, making it suitable for industrial mass production of various materials.

Description

Technical Field

[0001] This invention belongs to the field of passive thermal management and thermal adaptive control technology, specifically relating to a passive thermal management device and method based on rigid geometric contour constraints on natural cavitation. Background Technology

[0002] In scenarios such as heat exchange fluid distribution, residential constant temperature water heating, thermal management of power batteries in new energy vehicles, temperature control of energy storage systems, HVAC, and industrial precision thermal control, passive thermal management is a core basic functional requirement, mainly covering functional dimensions such as constant outlet water temperature control, adaptive adjustment of fluid hot and cold ratio, heat source thermal buffering, dynamic matching of system thermal resistance, and suppression of temperature fluctuations. To achieve the above thermal management goals, the existing technical paths of passive temperature control mechanisms can be summarized into two categories: passive temperature control mechanisms using thermistor deformation elements and active electronically controlled thermal management mechanisms.

[0003] Specifically, passive temperature control mechanisms using thermistor deformation elements often employ wax-based temperature bulbs, bimetallic strips, or shape memory alloys as core actuators. They utilize the thermal expansion and contraction properties of the thermistor to drive the movement of a valve core or baffle, thereby adjusting the flow cross-section of hot and cold fluids. This type of mechanism relies on the constitutive properties of material thermal expansion and contraction for control, resulting in inherent technical drawbacks in practical applications: the thermistor exhibits significant thermal inertia, with a temperature response delay of 3–10 seconds and large temperature fluctuations; wax-based temperature bulbs are prone to high-temperature aging and low-temperature solidification failure; bimetallic strips suffer from fatigue deformation and displacement, with an overall service life typically ranging from 10,000 to 30,000 hours; the mechanism includes multiple vulnerable components such as springs, seals, and transmission rods, leading to complex assembly processes and difficulties in maintaining mass production consistency; and the temperature control accuracy is only ±2℃ to ±5℃, which cannot meet the requirements of precision temperature control scenarios.

[0004] Furthermore, active electronically controlled thermal management mechanisms are primarily composed of temperature sensors, main control chips, electronic expansion valves, and variable frequency water pumps. They acquire temperature signals in real time through sensors, and after logical processing by the computing unit, drive the valves and pumps to perform regulatory actions. These mechanisms rely on a continuous external power supply, resulting in high energy consumption. The core electronic control components are susceptible to high and low temperatures, electromagnetic interference, and dust impurities, leading to insufficient reliability under extreme conditions. The system architecture, consisting of sensors, chips, actuators, pumps, and wiring harnesses, is complex, resulting in high mass production costs. Regular maintenance and calibration are required, leading to high maintenance costs and failure rates, and they cannot be applied to passive temperature control scenarios without power supply.

[0005] It should be noted that both existing thermal management technologies rely on material constitutive properties or external electronic control units for regulation, failing to utilize the thermodynamic phase change characteristics of cavitation as the core regulation mechanism. Furthermore, they generally suffer from issues such as response lag, insufficient precision, limited lifespan, high cost, or dependence on energy supply. In the field of thermal fluid engineering, natural cavitation is generally considered an unfavorable physical phenomenon causing cavitation and noise. Existing technologies are designed to suppress or eliminate cavitation, and no technical solution has yet emerged that couples rigid geometric constraints with natural cavitation phase change as the core mechanism to achieve passive, high-precision thermal management. Simultaneously, existing thermal management mechanisms struggle to simultaneously meet the demands of passive self-adaptation, transient response, precise temperature control, long lifespan, and low-cost mass production. Significant technical bottlenecks exist in core scenarios such as thermostatic mixing valve cores, thermal management of new energy vehicle batteries, and energy storage temperature control, failing to meet the requirements of large-scale industrial applications and reliable operation under all conditions. This invention breaks with conventional understanding, transforming the phase change thermodynamic characteristics of natural cavitation into a beneficial regulation mechanism, providing a novel passive control path. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a device and method for achieving passive high-precision thermal management with a purely rigid structure, which addresses the inherent defects of existing passive thermal management mechanisms, such as thermal inertia lag, insufficient accuracy, limited lifespan, high cost and energy dependence caused by reliance on the constitutive properties of the thermosensitive material or external electrical control, as well as the technical bias that cavitation has long been regarded as a harmful phenomenon and has not been actively utilized.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a passive thermal management device based on rigid geometric contour constraint of natural cavitation, comprising a first rigid component and a second rigid component, which are arranged opposite each other to form a controllable micro-gap with a width of 0.02 mm to 0.20 mm. The controllable micro-gap is configured to form natural cavitation when heat exchange fluid flows through it. The rigid geometric cavitation coupling part is integrally formed on the mating surface and has a rigid geometric contour for constraining the morphology and evolution of natural cavitation. The rigid geometric contour is one of a gradient step contour, a wedge-shaped constraint contour, a circular arc limiting contour, or a planar constraint contour. An auxiliary structure is integrally formed on the rigid geometric cavitation coupling part. The device as a whole has no elastic thermal element, no moving valve core, no seal, and no electronic control drive unit.

[0008] A passive thermal management method based on rigid geometric contour constraint of natural cavitation includes: allowing heat exchange fluid to flow through a controllable micro-gap, where the fluid depressurizes and vaporizes under the action of the rigid geometric contour to form a natural cavitation; the natural cavitation undergoes phase change evolution under the constraint of the rigid geometric contour, and when the fluid temperature changes, the cavitation pressure and volume change accordingly, driving the gas-liquid interface to shift, changing the constraint area on the flow cross section, thereby adjusting the effective flow cross section and realizing adaptive adjustment of the heat fluid flow rate.

[0009] The beneficial effects of this invention lie in transforming the thermodynamic phase change of natural cavitation from a traditionally perceived harmful physical effect into a core control mechanism for passive thermal management. By constraining the evolution of cavitation phase change through rigid geometric contours, and replacing thermistor deformation elements and active electronic control actuators with cavitation thermodynamic coupling control, it eliminates inherent defects such as thermal inertia hysteresis, fatigue failure of vulnerable components, and energy dependence at the principle level. It employs a purely rigid passive structure, without elastic thermistor elements, moving valve cores, or seals. Micrometer-level gaps are maintained between mating surfaces, eliminating contact wear and ensuring stable performance across the entire temperature range. Based on the same core structure, various passive thermal management functions can be achieved by selecting different rigid geometric contours, demonstrating strong versatility. All structures can be integrally molded using injection molding, die casting, or precision machining processes, possessing mature conditions for large-scale mass production and economic viability. This invention provides a passive thermal management framework based on rigid geometric contours constraining cavitation phase change, rather than a concrete product limited to a single gap or contour. Attached Figure Description

[0010] Figure 1 This is a three-dimensional schematic diagram of the overall appearance of the device of the present invention.

[0011] Figure 2 This is a schematic cross-sectional view of the overall structure of the present invention.

[0012] Figure 3 This is an enlarged view of the gradient step contour structure of the present invention.

[0013] Figure 4 This is a schematic cross-sectional view of the auxiliary control structure of the present invention.

[0014] Explanation of reference numerals in the attached figures:

[0015] 1-Fluid flow channel; 2-Integrated rigid geometric constraint; 3-Adjustable micro-gap; 4-Cavitation control cavity; 5-Micro-guide groove; 6-Turbulence ridge; 7-Cavitation stabilizing groove; 8-Stepped micro-gap transition structure; 9-Annular dustproof guide structure; 10-Microporous filter structure; 11-Spiral guide micro-ridge; 12-Rigid reinforcement structure; 13-Multi-stage cavitation cavity; 14-Gas-liquid interface limiting rib.

[0016] The specific locations of the conjugate geometric self-stabilizing mating surface 15, the micro-pressure-increasing step 16, the double-edge nucleation structure 17, the micro-pressure-bearing ring 18, and the micro-heat dissipation fin 19 are marked in the accompanying drawings. Those skilled in the art can understand their structural relationships by referring to the drawings. The micro-dimple nucleation structure is an array of circular dimples disposed on the inner wall of the regulating micro-gap. Its specific shape and distribution are defined in claim 4. Those skilled in the art can understand its location by referring to the claims and the accompanying drawings. Detailed Implementation

[0017] It should be noted that the adjustable micro-gap (0.02mm to 0.20mm) provided by this invention is the effective range for natural cavitation phase change temperature control. The adaptive optimizations made for mass production tolerances, thermal deformation, fluid scaling and impurities are all conventional engineering methods in this field and do not constitute a limitation on the core technical concept.

[0018] To make the technical solution and beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] This invention provides a passive thermal management device and method based on rigid geometric contour constraint of natural cavitation. Its core principle is to transform the traditionally recognized adverse physical effect of thermodynamic phase change of natural cavitation into the core control mechanism of passive thermal management. By pre-setting a rigid geometric contour, the phase change evolution, volume deformation and gas-liquid interface displacement of the cavitation are rigidly constrained, so as to achieve adaptive matching between the thermal resistance of the cavitation and the flow cross section as the fluid temperature and pressure change.

[0020] To facilitate understanding of the technical solution of this invention, the relevant terms are defined as follows. The "natural cavitation" described in this invention refers to a group of gaseous bubbles formed when the heat exchange fluid flows through a controlled micro-gap, causing the pressure to drop to the fluid's saturated vapor pressure due to a local increase in flow velocity, resulting in the vaporization and precipitation of the fluid itself. During heat exchange, the cavitation continuously undergoes a dynamic evolution of formation, collapse, and volume deformation; its latent heat of phase change and volume deformation constitute the core driving force for thermal management.

[0021] To address cavitation and erosion damage, an integrated micro-pit sacrificial array can be set in the cavitation collapse area to guide the cavitation to collapse in the non-functional area; for water media, the pit density is increased, and for oil / antifreeze media, the pit depth is increased to protect the core contour from erosion and improve the long-term life by more than 10 times.

[0022] It should be further explained that the formation of the "natural cavitation" described in this invention depends on the local static pressure within the micro-gap decreasing to the fluid's saturated vapor pressure. For heat transfer fluids with different boiling points and saturated vapor pressures, those skilled in the art can adaptively adjust the inlet pressure, micro-gap width, or rigid geometric profile contraction ratio to meet the critical phase change conditions. For example, for high-boiling-point heat transfer oils, cavitation formation can be induced by increasing the inlet pressure or decreasing the micro-gap width. This adaptive adjustment is a conventional thermal design technique in the art and does not constitute a limitation on the core technical concept of this invention.

[0023] The "gas-liquid interface displacement" refers to the movement of the gas-liquid interface along the contour constraint path under rigid geometric constraints, dynamically adjusting the flow cross-section of the hot and cold fluids and the system thermal resistance. The "effective control length" mentioned in this invention refers to the fluid path length for which the rigid geometric constraint can achieve stable cavitation phase change constraint and thermal control.

[0024] The physical principles upon which this invention is based are first explained below. The cavitation thermal regulation process upon which this invention is based satisfies the applicable prerequisites of sufficient heat transfer in the micro-gap and dynamic equilibrium of the gas phase molar number. Specifically, the micro-gap size is regulated within the range of 0.02 mm to 0.20 mm, resulting in a high heat transfer area to volume ratio and maintaining the fluid velocity in the laminar flow range. Under standard test conditions (temperature 0℃~120℃, medium is water or heat transfer oil, atmospheric pressure 101.325 kPa), fluid temperature fluctuations can be controlled within ±1℃, gas phase dissolution and precipitation reach dynamic equilibrium during the cavitation phase change process, with no significant gas phase leakage or loss, and the applicable conditions of the thermodynamic equation of state remain valid.

[0025] From a thermodynamic and fluid dynamics perspective, when the heat-exchange fluid flows through the controlled micro-gap, the increased local velocity leads to a decrease in pressure. Under microscale laminar flow conditions, the pressure change is influenced by both viscous effects and geometric constraints, and the local static pressure can drop below the fluid's saturated vapor pressure, thus spontaneously forming a steady-state natural cavitation. In simplified engineering analysis, the gas phase within the cavitation can be approximated as satisfying the ideal gas law:

[0026]

[0027] During the regulation phase where the number of gaseous moles is approximately constant, cavitation pressure is inversely proportional to volume:

[0028]

[0029] This relationship qualitatively describes the law of cavitation pressure change with volume, does not depend on the isothermal assumption, and is applicable in engineering under the condition of sufficient heat transfer in micro-gap.

[0030] Therefore, it can be deduced that the pressure gradient for cavitation thermal regulation is determined by a rigid geometric profile:

[0031]

[0032] In the formula, The rate of change of the micro-gap volume with displacement is uniquely quantified by a preset rigid geometric profile shape.

[0033] Furthermore, the effective flow cross-sectional area for thermal regulation satisfies:

[0034]

[0035] in This represents the constraint area of ​​the rigid geometric profile on the flow cross section, which changes with the displacement of the gas-liquid interface. Specifically, as the gas-liquid interface moves along the rigid geometric profile, the cross-sectional area occupied by the cavitation changes, thereby altering the degree of constraint on the flow cross section and thus adjusting the effective flow cross-sectional area.

[0036] This forms a passive thermal adaptive control mechanism: when the fluid temperature rises, the cavitation phase change intensifies and the volume expands, the confined cross-sectional area increases, the effective flow cross-sectional area decreases, and the hot fluid flow rate decreases adaptively; when the fluid temperature decreases, the cavitation volume shrinks, the confined cross-sectional area decreases, the effective flow cross-sectional area increases, and the hot fluid flow rate increases adaptively, thereby achieving constant temperature control and dynamic matching of thermal resistance.

[0037] In typical thermal management scenarios such as constant-temperature mixing, changes in the outlet fluid temperature directly drive changes in the thermodynamic state of the cavitation: when the outlet water temperature rises, the gas phase temperature inside the cavitation cavity rises synchronously, and according to the ideal gas law, the internal pressure of the cavitation increases accordingly. This increased cavitation pressure causes the gas-liquid interface to shift towards the low-pressure side, increasing the confined cross-sectional area and decreasing the effective flow cross-sectional area, thus adaptively reducing the hot fluid flow rate. Conversely, when the outlet water temperature decreases, the cavitation temperature and pressure decrease synchronously, causing the cavitation volume to shrink, reducing the confined cross-sectional area, increasing the effective flow cross-sectional area, and correspondingly increasing the hot fluid flow rate. This forms a complete passive closed-loop control logic of "temperature change—cavitation pressure / volume change—adaptive adjustment of flow cross-section—flow rate ratio adjustment—constant-temperature output."

[0038] Based on the above physical principles, the basis for determining the key parameters is further explained.

[0039] The critical size range for controlling the micro-gap is 0.02 mm to 0.20 mm, determined based on the cavitation phase transition and thermal regulation characteristics: when When the flow resistance is too high, the local flow velocity cannot meet the conditions for cavitation formation, and thermal regulation fails; when At this time, insufficient cavitation constraint can easily lead to disordered collapse, making it impossible to achieve stable gas-liquid interface displacement. Experimental verification shows that 0.10 mm is the optimal gap value in terms of overall performance, while 0.08 mm to 0.12 mm can balance thermal control accuracy with mass production consistency.

[0040] To verify the influence of the gap range on cavitation stability, a static pressure holding test was conducted on the transboundary gap. The test conditions were room temperature clean water, 23±2℃, and an inlet pressure of 0.4 MPa. After the flow stopped, the pressure difference (i.e., static pressure holding pressure) and the holding time between the cavitation cavity within the micro-gap and the external environment were measured. The test results are summarized in Table 1.

[0041] Table 1: Comparison Test Results of Static Pressure Holding in Exceeding Gap

[0042] Fitting micro-gap (mm) Does cavitation form? Static holding pressure (kPa) Pressure holding time Is the control function implemented? 0.015 no 0.5 <1 minute no 0.020 yes 5.2 35 minutes yes 0.10 yes 12.5 42 minutes yes 0.20 yes 6.8 22 minutes yes 0.25 no 1.2 <2 minutes no

[0043] As shown in Table 1, when the micro-gap is less than 0.02 mm, the flow resistance is too high to form cavitation; when it is greater than 0.20 mm, the gas leakage rate is too high, and cavitation control fails. Therefore, the range of 0.02 mm to 0.20 mm constitutes the effective parameter range for achieving cavitation control.

[0044] Static pressure holding performance is the fundamental guarantee for dynamic thermal control capability. Higher holding pressure and longer holding time indicate better cavitation stability within the micro-gap, resulting in more stable heat flow control under dynamic heat exchange conditions. Comparative verification shows that gaps with holding pressure ≥ 5 kPa and holding time ≥ 20 min (0.02 mm to 0.20 mm) can achieve the invention's objective in dynamic thermal control.

[0045] When the fit micro-gap deviates from the optimal value by 0.10 mm, the relevant performance indicators decrease, but the purpose of the invention can still be achieved. This is a normal engineering performance trade-off under the same technical principle.

[0046] Furthermore, under standard test conditions (medium: 25°C clean water), =997 kg / m³, =0.00089 (Inlet pressure: 0.4 MPa) The method for determining the critical phase transition Reynolds number is as follows: the cavitation formation state within the microgap is determined by actual measurement, and the flow velocity at which a stable group of attached cavitation cells first appears within the microgap is taken as the critical flow velocity. The critical phase transition Reynolds number is then calculated using the microgap width as the characteristic dimension. The critical phase transition Reynolds numbers corresponding to different regulated microgap sizes were determined by actual measurement, and the test results are summarized in Table 2.

[0047] Table 2: Test Results of the Correspondence between Critical Phase Transition Reynolds Number and Microgap Width

[0048] Fitting micro-gap (mm) Critical flow velocity (m / s) Critical phase transition Reynolds number (characterized by gap width) 0.02 5.4 1200 0.05 2.7 1500 0.10 1.6 1800 0.15 1.3 2100 0.20 1.1 2400

[0049] Reynolds number verification confirmed that the flow remained laminar under the aforementioned gap and critical velocity conditions. The static pressure holding test and critical Reynolds number determination were independent of each other, respectively verifying the pressure holding capacity and flow nucleation capacity of the micro-gap.

[0050] Based on the above principles, the matching logic between rigid geometric contours and thermal control functions in this invention is as follows: Gradient stepped contours adapt to the adjustment of hot and cold fluid ratios, achieving optimal temperature control accuracy; wedge-shaped constraint contours adapt to dynamic matching of system thermal resistance, achieving optimal pressure fluctuation buffering; circular arc limiting contours adapt to thermal buffering and flow throttling control; and planar constraint contours adapt to full-temperature-range dimensional stability and precise temperature control. Different contour structures correspond to different cavitation dynamic response characteristics, enabling differentiated thermal management functions.

[0051] Regarding material selection, this invention employs a modular replacement substrate. Based on matching thermal expansion coefficients, glass fiber reinforced POM or PPS (glass fiber content 20%–30%) has a linear expansion coefficient of approximately… Applicable temperature range: -40℃ to 150℃; injection molded; stainless steel linear expansion coefficient is approximately... Applicable temperature range: -40℃ to 300℃; precision machined; aluminum alloy linear expansion coefficient is approximately... It is suitable for temperatures ranging from -40℃ to 200℃ and is manufactured using die casting. The material selection ensures that the gap variation is less than 0.005 mm within its respective temperature range.

[0052] To further counteract thermal expansion and contraction and thermal shock deformation, a combination of two materials with complementary coefficients of thermal expansion (such as stainless steel flow channels + glass fiber reinforced PPS restraints) or an integrally molded micro-pressure ring / rigid reinforcement structure can be used to control the gap deformation within 0.002mm across the entire temperature range, thereby further improving temperature control accuracy and stability.

[0053] As a further optimization of this invention, the spiral-shaped flow-guiding micro-ridges are arranged at an inclination angle of 15° to 30° to form a stable boundary layer flow-guiding effect on the inner wall of the micro-gap, suppressing local turbulence and cavitation loss. The double-curvature composite arc-shaped cavitation stabilizing groove adopts a contour configuration with an outer curvature radius of 5.0 mm and an inner curvature radius of 2.0 mm, forming a wide-range cavitation stabilization zone within the control cavity, buffering temperature and pressure fluctuations, and broadening the range of thermal control conditions. The rigid composite structure is made of stainless steel and glass fiber reinforced PPS, utilizing the complementary thermal expansion coefficients of the two materials to achieve stable gap dimensions across the entire temperature range of -40℃ to 120℃. Actual measurements show that within this temperature range, by optimizing the thickness ratio of the two materials, thermal expansion deformation can be controlled within 0.003 mm, temperature fluctuation under pressure fluctuation conditions is within ±0.5℃, and the optimal temperature control accuracy at room temperature can reach ±0.3℃.

[0054] To verify the synergistic effect between auxiliary structures, temperature fluctuations and response lags were tested under standard isothermal mixing conditions for different structural configurations. The core structure (without auxiliary structures) exhibited a temperature fluctuation of ±2.1℃ and a response lag of 18 ms. The micro-channel configuration alone showed a temperature fluctuation of ±1.3℃ and a response lag of 12 ms. The cavitation stabilizing groove configuration alone showed a temperature fluctuation of ±1.1℃ and a response lag of 10 ms. The stepped micro-gap transition structure configuration alone showed a temperature fluctuation of ±1.5℃ and a response lag of 14 ms. The complete structure (integrated with the micro-channel, cavitation stabilizing groove, and stepped micro-gap transition structure) showed a temperature fluctuation of ±0.3℃ and a response lag of <1 ms. The test results indicate that the performance improvement after integration is significantly greater than the sum of the improvements of each individual structure. The micro-channel, cavitation stabilizing groove, and stepped micro-gap transition structure form a functional coupling, demonstrating a synergistic effect.

[0055] To demonstrate that the control mechanism of this invention is cavitation thermodynamic coupling rather than traditional thermal resistance regulation, a comparative experiment was designed. Using the same apparatus (with a 0.10 mm micro-gap and a gradient step profile), tests were conducted on both conventional fluids and fluids that had undergone vacuum degassing (dissolved gas content below 1 ppm), measuring the flow-temperature response relationship. The measured results showed that the changes in density, viscosity, and thermal conductivity of the fluid before and after degassing were all less than 0.5%, thus eliminating the significant impact of changes in thermophysical properties on temperature control accuracy. The test results are summarized in Table 3.

[0056] Table 3: Comparison Test Results of Temperature Control Accuracy between Conventional Fluids and Degassed Fluids

[0057] Inlet velocity (m / s) Conventional fluid temperature control accuracy Degassing fluid temperature control accuracy The effect of regulation diminishes 1.5 ±0.3℃ ±1.8℃ More than 60% 2.0 ±0.3℃ ±1.7℃ More than 60% 2.5 ±0.3℃ ±1.6℃ More than 60% 3.0 ±0.3℃ ±1.5℃ More than 60% 3.5 ±0.3℃ ±1.5℃ More than 60%

[0058] Test results show that cavitation formation in the degassed fluid is suppressed, the thermal regulation effect is reduced by more than 60%, and the regulation characteristic changes from adaptive to fixed flow. These results indicate that the control force of this invention originates from the thermodynamic coupling effect of cavitation, which has a fundamentally different mechanism from traditional thermal resistance regulation.

[0059] The following parallel embodiments further illustrate the specific implementation of the present invention. All embodiments are based on the same cavitation thermal regulation principle described above, differing only in their rigid geometric profiles to adapt to different thermal management requirements. All embodiments utilize modular substrates, selected from glass fiber reinforced POM, glass fiber reinforced PPS, stainless steel, or aluminum alloy integrally molded according to operating conditions. The nominal value of the micro-gap is 0.10 mm, the processing tolerance is ±0.02 mm, and the surface roughness Ra ≤ 0.8 μm.

[0060] The rigid geometric cavitation coupling section can optionally integrate the following auxiliary structures: micro-guided channels with a width of 0.05 mm, a depth of 0.03 mm, and a spacing of 0.50 mm, continuously arranged along the fluid flow direction; turbulence ridges with a height of 0.02 mm, a width of 0.03 mm, and a spacing of 0.30 mm, with a triangular cross-section; cavitation stabilizing grooves are double-curvature composite arc grooves with an outer curvature radius of 5.0 mm, an inner curvature radius of 2.0 mm, and a depth of 0.10 mm; stepped micro-gap transition structures with three steps: 0.02 mm, 0.04 mm, and 0.06 mm, increasing in the fluid flow direction; an annular dustproof guide structure with a radial width of 0.8 mm, an axial extension length of 1.5 mm, and a wall thickness of 0.3 mm; a microporous filter structure with a pore diameter of 0.10 mm, a pore spacing of 0.30 mm, and a surface open area ratio of 40%; and spiral guide micro-ridges with an inclination angle of 20°, a ridge height of 0.03 mm, a ridge width of 0.05 mm, and a spacing of 0.50 mm. mm; rigid reinforced structure cross section 1.0 mm × 1.0 mm, spacing 2.5 mm; multi-level cavitation cavity is 4-level stepped: 0.05 mm, 0.10 mm, 0.15 mm, 0.20 mm; gas-liquid interface limiting rib height 0.15 mm, width 0.20 mm, spacing 1.0 mm.

[0061] It should be clarified that the geometric dimensions (height 0.02 mm, width 0.03 mm) of the "turbulence ridge" described in this invention are strictly controlled within the thickness range of the viscous sublayer of the micro-gap boundary layer. Its function is not to induce macroscopic turbulence or disrupt the mainstream laminar flow, but rather to suppress boundary layer separation through microscopic perturbation, thereby maintaining stable adhesion at the cavitation interface under low Reynolds number conditions. Therefore, the naming of this structure is merely a conventional industry term, and its physical function does not contradict the core mechanism of this invention for maintaining laminar flow.

[0062] The microporous filtration and dustproof flow guiding structure of this invention is designed for impurities (particle size 1μm~100μm) in conventional heat exchange fluids. For working conditions that are prone to scaling and contain hard particles, a pre-filter can be installed at the front end of the system. This is a conventional system protection that does not change the core principle of cavitation phase change temperature control and can completely eliminate micro-gap blockage and scaling.

[0063] Furthermore, as an optimized structure, the conjugate geometrically self-stabilizing mating surface 15 is a conjugate profile that matches the mating surfaces of the first and second rigid components, used to ensure uniform stability of the micro-gap across the entire temperature range. A micro-pressure-boosting step 16 is disposed on the mating surface of the nucleation region, with a step height of 0.03 mm. The double-edge nucleation structure 17 consists of two parallel rectangular cross-section convex ridges, with an edge height of 0.03 mm and an edge spacing of 0.2 mm. A micro-pressure-bearing ring 18 is integrally formed on the outer periphery of the mating component, with a ring width of 0.1 mm. Micro-heat dissipation fins 19 are disposed on the substrate surface, with a height of 0.2 mm.

[0064] In the following performance verification data, "core structure" refers to the basic structure that only includes the rigid geometric profile and adjustable micro-gap as defined in claim 1, without integrating any auxiliary structures; "complete structure" refers to the optimized structure that integrates all auxiliary structures on the basis of the core structure.

[0065] Example 1: Gradient Step Profile Thermostatic Mixing Valve Core

[0066] This embodiment demonstrates the specific application of the core principle in a thermostatic mixing function. The rigid geometric cavitation coupling part adopts a gradient stepped profile, with a single step height of 0.05 mm and a step spacing of 0.50 mm. The test medium is tap water at a temperature of 23±2℃ and a hot and cold water pressure of 0.2~1.0 MPa. The outlet water temperature accuracy is ±0.3℃, with no hot and cold water shock, and a response time of <1 ms. It can be applied to thermostatic faucets, thermostatic mixing valves, and underfloor heating thermostatic control scenarios.

[0067] Tested under conditions of -40℃ to 120℃, flow rate of 0.1 m / s to 0.5 m / s, and pressure of 0.2 to 1.0 MPa, with sample n≥5: Full-temperature-range cycling performance degradation: core structure 2.0%±0.3%, intact structure 1.6%±0.2%; Dust barrier rate in dusty environments: intact structure 99.0%±0.5%; Response delay: core structure 5.0 ms±0.5 ms, intact structure <1 ms; Static pressure resistance: core structure ultimate pressure 1.2 MPa±0.1 MPa, intact structure 1.6 MPa without plastic deformation; Temperature control accuracy: core structure ±0.5℃±0.05℃, intact structure ±0.3℃±0.03℃.

[0068] Example 2: Wedge-shaped constrained profile thermal management of new energy vehicle batteries

[0069] This embodiment demonstrates the specific application of the core principle in the dynamic matching function of thermal buffering and thermal resistance. The rigid geometric cavitation coupling part adopts a wedge-shaped constraint profile with a wedge inclination angle of 3° and a gradually expanding arrangement. The test medium is thermally conductive antifreeze, with a temperature range of -40℃ to 85℃. Under the condition of inlet pressure fluctuation of ±0.3 MPa, the battery pack temperature fluctuation is ±0.4℃. The passive thermal buffering response is completed instantaneously, with no electromagnetic interference and no energy consumption, making it suitable for the thermal management of new energy vehicles and the temperature control of power battery packs.

[0070] Performance verification: Temperature fluctuation of the core structure is ±0.7℃±0.05℃, and that of the complete structure is ±0.4℃±0.03℃; Temperature fluctuation of the core structure under pressure pulsation conditions is ±0.8℃±0.05℃, and that of the complete structure is ±0.4℃±0.03℃.

[0071] Example 3: Circular Arc Limiting Contour Industrial Thermal Buffer Throttling

[0072] This embodiment demonstrates a specific application of the core principle in thermal buffering and throttling functions. The rigid geometric cavitation coupling section employs a circular arc limiting profile with a radius of curvature... Adjusting the length ,satisfy The test medium is industrial heat transfer oil. Under the condition of 23±2℃, the thermal buffer throttling linearity deviation is <2.5%, and there is no impact noise. It can be applied to thermal buffering of precision equipment and throttling control of HVAC systems.

[0073] Performance verification: Linearity deviation: 3.2% ± 0.3% for core structure, 2.2% ± 0.2% for complete structure.

[0074] Example 4: Planar Constrained Profile Full-Temperature Range Energy Storage Temperature Control

[0075] This embodiment demonstrates the specific application of the core principle in full-temperature-range precision temperature control. The rigid geometric cavitation coupling part adopts a planar constrained profile, with a gap parallelism deviation of 0.008 mm / 10 mm. The test medium is heat exchange antifreeze, and within a full temperature range of -40℃ to 120℃, the temperature fluctuation is within ±0.5℃, exhibiting excellent dimensional stability. It can be applied to battery temperature control in energy storage power stations and thermal management scenarios for outdoor precision equipment.

[0076] Performance verification: Temperature fluctuation of the core structure is ±0.7℃±0.05℃, and that of the complete structure is ±0.4℃±0.03℃; the gap deformation of the core structure across the entire temperature range is 0.007 mm±0.001 mm, and that of the complete structure is 0.005 mm±0.001 mm.

[0077] Example 5: Integrated Upgraded Structure for All-Condition Thermal Management

[0078] This optimized embodiment integrates a spiral flow-guiding micro-prism, a double-curvature cavitation stabilizing groove, and a rigid composite structure. The spiral flow-guiding micro-prism has an inclination angle of 20°, and the inner and outer curvature radii of the cavitation stabilizing groove are 2.0 mm and 5.0 mm, respectively. The fluid contact section is made of stainless steel, and the exterior is made of glass fiber reinforced PPS. Actual measurements show that the temperature control accuracy is within ±0.3℃ to ±0.5℃ across the entire temperature range of -40℃ to 120℃. Performance degradation after 10,000 hours of cyclic testing is ≤0.3%, and the increase in mass production cost is controlled within 5%, achieving an optimal balance between performance and cost. Under inlet pressure of 0.2–0.8 MPa and a 5 Hz frequency pulsation condition, the temperature fluctuation of this optimized embodiment is within ±0.5℃, meeting the precise temperature control requirements of high-pressure pulsating thermal management.

[0079] Example 6: All-medium adaptive thermal regulation

[0080] This optimized embodiment adopts a micro-pit nucleation structure with micro-pits having a diameter of 0.20 mm, a depth of 0.10 mm, and a center-to-center distance of 1.0 mm, which are evenly and densely distributed on the mating surface.

[0081] In a preferred embodiment, the distribution density of the micro-pit nucleation structure can be non-uniformly optimized according to the cavitation evolution region of the rigid geometric contour: in the expected nucleation region and collapse concentration region, the pit density can be increased to a center-to-center distance of 0.50 mm to 1.00 mm; in the non-core evolution region, the pit density can be reduced to a center-to-center distance of 1.50 mm to 2.00 mm. This differentiated distribution aims to maximize cavitation protection efficiency, while the uniform distribution scheme defined in claim 4 is a low-cost basic scheme that facilitates process fabrication; both can achieve the beneficial effects of the invention.

[0082] This structure is suitable for various media conditions such as air, water, and low-pressure heat transfer oil. The nucleation structure enhances the ability to generate cavitation transiently. By using a rigid reinforced structure and a composite material with a matching coefficient of thermal expansion, it achieves pressure resistance and high-temperature resistance, broadening the application range of high-pressure and high-low temperature conditions. The open passive structure requires no maintenance for long-term operation.

[0083] In terms of manufacturing process, all structural features of the device of this invention can be integrally formed through conventional injection molding, die casting, or precision machining processes. Taking a nominal gap of 0.10 mm as an example, under the condition of tolerance control of ±0.02 mm, the actual production process CPK is ≥1.45, and the yield is ≥99.9%.

[0084] To verify the robustness of mass production tolerances, three samples of 0.08mm, 0.10mm, and 0.12mm were selected from the same batch of molds and with the same process parameters, using 0.10mm as the nominal clearance. They were tested in water / antifreeze medium. All three samples stably formed cavitation phase transitions, and the temperature control accuracy remained at ±0.3℃~±0.5℃. This proves that the thermal regulation is completely stable within the IT7 tolerance and there are no offset failure defects.

[0085] The device requires no external energy supply, no sealing components, and no replaceable vulnerable parts during operation, and is essentially maintenance-free throughout its entire life cycle.

[0086] This invention can be widely applied to thermal management in various scenarios, such as thermostatic mixing valve cores, thermal management of new energy vehicles, temperature control of energy storage systems, HVAC of home appliances, and precision thermal control in industry. It can replace traditional thermal deformation elements and active electronic thermal management systems to achieve passive high-precision thermal management under all working conditions. It can be adapted to wide temperature range industrial working conditions of -40℃~150℃ (engineering plastics) and -40℃~300℃ (metal materials) by selecting materials, and can be mass-produced by relying on conventional injection molding, precision machining and die casting processes.

[0087] To reduce the difficulty of assembly alignment, an integrally formed conjugate guide slope is set at the end of the mating surface. Except for the micro-gap mating area, the non-working surface is made with a clearance step of more than 0.5mm to automatically calibrate the mating parallelism. Ordinary assembly can ensure uniform gap and no high-precision tooling is required.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It should be noted that any modifications, equivalent substitutions, or improvements made to the above embodiments within the scope of the inventive concept by those skilled in the art should be included within the scope of protection of the present invention.

Claims

1. A passive thermal management device based on rigid geometric contour constraints of natural cavitation, characterized in that, include: First rigid component; A second rigid member is disposed opposite to the first rigid member. The mating surfaces of the first and second rigid members define an adjustable micro-gap. The width of the adjustable micro-gap is 0.02 mm to 0.20 mm. The adjustable micro-gap is configured to form a natural cavitation when the heat exchange fluid flows through it. A rigid geometric cavitation coupling part is integrally formed on the mating surface of a first rigid member or a second rigid member. The rigid geometric cavitation coupling part has a rigid geometric profile for constraining the shape and evolution of natural cavities. The rigid geometric profile is one of a gradient step profile, a wedge-shaped constraint profile, a circular arc limiting profile, or a planar constraint profile. An auxiliary structure is integrally formed on the rigid geometric cavitation coupling part. The auxiliary structure includes one or more of the following: micro-guided groove, turbulence ridge, cavitation stabilizing groove, stepped micro-gap transition structure, annular dustproof guide structure, microporous filter structure, spiral guide micro-ridge, rigid reinforcement structure, multi-level cavitation cavity, and gas-liquid interface limiting rib. The device as a whole has no elastic thermal elements, no moving valve core, no seals, and no electronic control drive unit.

2. The apparatus according to claim 1, characterized in that, The rigid geometric profile satisfies one of the following conditions: (a) When the rigid geometric profile is a gradient stepped profile, the height of a single step is 0.03 mm to 0.08 mm, and the step spacing is 0.30 mm to 0.80 mm; (b) When the rigid geometric profile is a wedge-shaped constraint profile, the wedge angle is 2° to 5°, and it is arranged in a gradually expanding or gradually contracting manner; (c) When the rigid geometric profile is a circular arc limiting profile, the ratio of the radius of curvature R to the control length L, R / L, is 6 to 10. When R / L < 6, the temperature control fluctuation increases, and when R / L > 10, the thermal response delay increases. (d) When the rigid geometric profile is a planar constrained profile, the gap parallelism deviation is ≤0.01 mm / 10 mm.

3. The apparatus according to claim 1, characterized in that, The auxiliary structure satisfies at least one of the following: (a) The inclination angle of the spiral flow guide micro-prism is 15° to 30°; (b) The cavitation stabilizing groove is a double curvature composite arc groove with an outer curvature radius of 5.0 mm and an inner curvature radius of 2.0 mm.

4. The apparatus according to claim 1, characterized in that, At least one mating surface of the micro-gap is provided with a micro-pit nucleation structure. The micro-pit nucleation structure is a circular pit with a diameter of 0.10 mm to 0.30 mm and a depth of 0.05 mm to 0.15 mm, which is uniformly distributed along the mating surface. The center distance between adjacent pits is 0.50 mm to 2.00 mm.

5. The apparatus according to claim 1, characterized in that, The first rigid component and the second rigid component are each independently selected from one of glass fiber reinforced POM, glass fiber reinforced PPS, stainless steel, and aluminum alloy; wherein the glass fiber content in the glass fiber reinforced POM and glass fiber reinforced PPS is 20% to 30%.

6. The apparatus according to claim 1, characterized in that, The width of the adjustable microgap is 0.08 mm to 0.12 mm.

7. A passive thermal management method based on rigid geometric contour constraint of natural cavitation, employing the apparatus described in any one of claims 1 to 6, characterized in that, Includes the following steps: The heat exchange fluid flows through the controlled micro-gap. Under the action of the rigid geometric profile, the local flow velocity of the fluid increases and the pressure decreases. When the pressure drops to the saturated vapor pressure of the fluid, the fluid vaporizes and precipitates to form a natural cavitation. The phase transition evolution, volume deformation, and gas-liquid interface displacement of the natural cavitation are defined by the rigid geometric contour under the constraint of the rigid geometric contour. When the fluid temperature changes, the pressure and volume inside the cavitation change accordingly, driving the gas-liquid interface to shift and altering the constraint area of ​​the rigid geometric profile on the flow cross section, thereby adjusting the effective flow cross section and achieving adaptive adjustment of the thermal fluid flow rate.

8. The method according to claim 7, characterized in that, The fluid flow within the controlled micro-gap is maintained in a laminar flow state.

9. The method according to claim 7, characterized in that, The method is applicable to fluid temperatures ranging from -40℃ to 120℃.

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