A heat sink protection system and thermal stress mitigation method

Abstract

The present disclosure relates to the technical field of solar photo-thermal power generation, and particularly relates to a heat absorber protection system and a thermal stress inhibition method. The system comprises: a heat absorber pipe; a heat transfer sleeve arranged on the back light side wall of the heat absorber pipe; a gradient temperature sensitive driving unit connected with the heat transfer sleeve; a cam mechanism connected with the gradient temperature sensitive driving unit; a three-way plug valve connected with the cam mechanism; wherein the profile lead of the cam mechanism is constructed according to the response relationship between the temperature gradient of the heat absorber pipe and the equivalent thermal stress, for nonlinear adjustment of the main road flow when the heat absorber pipe occurs temperature drop, and inhibiting the transient thermal stress rise of the heat absorber pipe, realizing the completion of large proportion energy dissipation within the moment of stress generation, and avoiding the long-term bearing of thermal impact of the pipe material.

Description

Technical Field

[0001] This disclosure relates to the field of solar thermal power generation technology, and in particular to a heat absorber protection system and a method for suppressing thermal stress. Background Technology

[0002] In tower-type concentrated solar power (CSP) plants, the heat-receiving surfaces of the absorber panels need to heat the molten salt inside the tubes to approximately 565°C. Under normal operating conditions, the system maintains thermal balance through pump frequency and mirror field control. Currently, the industry's methods for dealing with sudden irradiance changes (such as cloud cover obstructing the mirror field) are to monitor the absorber outlet temperature and adjust the flow distribution of each panel tube bundle by controlling an electric proportional regulating valve, or to adjust the pump frequency, monitor the total outlet temperature of the absorber panels, and adjust the output frequency of the cold salt pump according to the temperature difference to change the total flow rate of the entire field.

[0003] Therefore, existing technologies suffer from a mismatch between physical regulation logic and thermal stress evolution. The thermal stress generated in the absorber tube at the moment of irradiation disappearance exhibits an exponential burst rather than a linear change. Existing linear linkages or conventional electronic control regulators have insufficient stroke gain in the initial response phase, failing to complete a large proportion of energy dissipation within the instant of stress generation, resulting in the tube being subjected to long-term thermal shock overload. Summary of the Invention

[0004] To address the aforementioned technical problems, this disclosure provides a heat absorber protection system and a method for suppressing thermal stress.

[0005] This disclosure provides a heat absorber system, including: Heat absorption tube; A heat transfer sleeve is disposed on the back side wall of the heat absorption tube. The heat transfer sleeve is used to sense the temperature change of the heat absorption tube and transmit the temperature drop signal. A gradient temperature-sensitive drive unit connected to the heat transfer sleeve is used to generate a drive displacement based on the temperature drop signal. A cam mechanism connected to the gradient temperature-sensitive drive unit, wherein the nonlinear stress-compensated cam mechanism is used to convert the drive displacement into a nonlinearly amplified adjustment stroke; A three-way plug valve connected to the cam mechanism, the three-way plug valve being used to adjust the molten salt flow distribution between the main path and the bypass based on the adjustment stroke; Specifically, the profile lead of the cam mechanism is constructed based on the response relationship between the temperature gradient and the equivalent thermal stress of the heat absorber tube. This is used by the three-way plug valve to nonlinearly adjust the main flow rate when the temperature of the heat absorber tube drops, and to suppress the rise of transient thermal stress in the heat absorber tube.

[0006] Furthermore, the heat transfer sleeve is configured with a double-layer structure, with a liquid metal medium in the inner interlayer. The liquid metal medium is used to transmit the temperature change of the heat absorption tube wall to the gradient temperature-sensitive drive unit.

[0007] Furthermore, the gradient temperature-sensitive driving unit includes: A drive rod, which is formed by nesting at least two shape memory alloys with different phase transformation characteristic temperatures.

[0008] Furthermore, the cam mechanism includes: An irregularly shaped compensating cam and a follower that cooperates with the irregularly shaped compensating cam; The contour curve of the irregularly shaped compensating cam is determined based on the functional relationship between the temperature change of the heat absorber and the equivalent thermal stress change, and is used to increase the displacement amplification factor of the cam lead within the thermal stress sensitive range.

[0009] Furthermore, the three-way plug valve includes: The valve body and the plug valve core rotatably disposed inside the valve body; The plug valve core is used to open the main circuit in the first position and increase the flow rate of the bypass in the second position.

[0010] Furthermore, the three-way plug valve also includes: Thermally coupled bridge plate and molten salt main inlet; The main molten salt inlet is used to supply high-temperature molten salt medium to the main road and bypass; The thermal coupling bridge is installed between the main road and the bypass road to conduct heat from the bypass road to the main road.

[0011] Furthermore, at least one micro-circulation adjustment groove is provided on the side of the plug valve core facing the main outlet, and the micro-circulation adjustment groove is used to maintain the micro-flow circulation of the main road when the main road is in the protection condition.

[0012] Furthermore, the microcirculation adjustment groove is configured as a V-shaped groove.

[0013] Furthermore, it also includes: Return spring; The reset spring is connected to the gradient temperature-sensitive drive unit and is used to drive the three-way stop valve back to the rated flow state after the temperature of the heat absorber tube recovers.

[0014] This disclosure also provides a method for suppressing thermal stress, including: The temperature change of the heat absorption tube is sensed by the heat transfer sleeve; Displacement is generated by the gradient temperature-sensitive driving unit based on the temperature change. The displacement is nonlinearly amplified by a cam mechanism to obtain the amplified adjustment stroke. Based on the amplified adjustment stroke, the three-way plug valve is driven to adjust the flow distribution between the main circuit and the bypass; The flow distribution between the main path and the bypass suppresses the growth of thermal stress in the heat absorption tube.

[0015] The technical solution provided in this disclosure has the following advantages compared with the prior art: The system comprises: a heat-absorbing tube; a heat transfer sleeve installed on the back side wall of the heat-absorbing tube, used to sense temperature changes in the heat-absorbing tube and transmit temperature drop signals; a gradient temperature-sensitive drive unit connected to the heat transfer sleeve, used to generate drive displacement based on the temperature drop signal; a cam mechanism connected to the gradient temperature-sensitive drive unit, a nonlinear stress-compensated cam mechanism used to convert the drive displacement into a nonlinearly amplified adjustment stroke; and a three-way stopcock valve connected to the cam mechanism, used to adjust the molten salt flow distribution between the main path and the bypass path based on the adjustment stroke. The profile lead of the cam mechanism is constructed based on the response relationship between the temperature gradient and equivalent thermal stress of the heat-absorbing tube, used by the three-way stopcock valve to nonlinearly adjust the main path flow when the heat-absorbing tube experiences a temperature drop, and to suppress the transient thermal stress rise of the heat-absorbing tube, achieving a large proportion of energy dissipation within the instant of stress generation, thus avoiding long-term thermal shock to the tube. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0017] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of a heat absorber system provided in an embodiment of this disclosure; Figure 2 A schematic diagram of a thermal stress suppression method provided in an embodiment of this disclosure; Figure 3 A schematic diagram showing the comparison of the adjustment characteristic response of this disclosure embodiment with that of the prior art under different wall temperature conditions; Figure 4 This is a schematic diagram comparing the equivalent thermal stress of the pipe wall under sudden cloud cover conditions with that of the prior art, provided in an embodiment of this disclosure.

[0019] In the diagram, 1 is the molten salt main inlet; 2 is the main path; 3 is the bypass path; 10 is the heat absorption pipe; 100 is the heat transfer sleeve; 200 is the gradient temperature-sensitive drive unit; 201 is the drive rod; 300 is the cam mechanism; 301 is the irregularly shaped compensation cam; 400 is the three-way plug valve; 401 is the thermodynamic coupling bridge; 402 is the micro-circulation adjustment groove. Detailed Implementation

[0020] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0021] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0022] Figure 1 This is a schematic diagram of a heat absorber system provided in an embodiment of this disclosure; as shown Figure 1 As shown, a heat absorber system includes: Heat absorption tube 10. A heat transfer sleeve 100 is disposed on the back wall of the heat absorption tube 10, the heat transfer sleeve 100 is used to sense the temperature change of the heat absorption tube 10 and transmit the temperature drop signal; In this embodiment, the heat absorber tube 10 is the core heat exchange component in the solar thermal absorber screen, used to absorb the solar radiation heat gathered by the concentrating system and complete the heat transfer through the molten salt medium flowing inside. In the tower-type solar thermal system, the heat absorber tube 10 operates in a high-temperature environment above 530°C for a long time, and its outer wall is directly exposed to strong solar radiation. Therefore, when conditions such as cloud cover, mirror field disturbance, or local uneven irradiation occur, the surface of the heat absorber tube 10 will experience drastic temperature gradient changes in a very short time. Since the material of the heat absorber tube 10 is usually a high-temperature alloy, its thermal expansion and contraction do not occur instantaneously and uniformly. Therefore, non-uniform thermal strain will rapidly form in the tube wall thickness direction and circumferential direction, thereby inducing transient thermal stress concentration. Especially during sudden cloud cover changes, the temperature of the light-receiving surface of the heat absorber tube 10 drops sharply, while the back-lighting surface remains at a higher temperature, resulting in a strong thermal stress coupling zone inside the material.

[0023] A heat transfer sleeve 100 (liquid metal heat transfer sleeve 100) is positioned on the back-side wall of the absorber tube 10. This allows for rapid acquisition of wall temperature change information without interfering with the normal heat exchange operation of the absorber tube 10, and the temperature drop signal is transmitted to the subsequent drive unit with high efficiency and low thermal resistance. In a tower-type solar thermal system, the light-receiving surface of the absorber tube 10 directly receives solar radiation, while the back-side, not being directly exposed to areas of high heat flux density, is more suitable as a stable structural installation area.

[0024] The heat transfer sleeve 100 is configured with a double-layer structure, with a liquid metal medium in the inner interlayer. The liquid metal medium is used to conduct the temperature change of the heat absorption tube 10 wall to the gradient temperature-sensitive drive unit 200.

[0025] By covering the backlight side with a heat transfer sleeve 100, local thermal disturbances caused by direct irradiation to the temperature-sensing structure can be effectively avoided, improving the stability of the temperature sensing signal. The heat transfer sleeve 100 preferably adopts a double-layer flexible metal structure with a closed interlayer between the two layers, and a gallium-indium liquid metal medium is placed inside. Preferably, the liquid metal medium can be a gallium-indium alloy. Since liquid metal has a thermal conductivity far higher than that of ordinary solid thermal conductive materials and can form a near-contactless thermal coupling state at the micro-interface, the transient temperature drop of the heat absorber tube 10 wall can be transmitted to the drive unit at millisecond speeds. Furthermore, the flexible sleeve 100 structure can adapt to the thermal deformation and vibration of the heat absorber tube 10 under high-temperature conditions, avoiding local stress concentration or contact failure caused by rigid connections. Temperature drop sensing can be completed in a very short time after cloud cover occurs, thereby significantly shortening the response time of the thermal shock protection link.

[0026] A gradient temperature-sensitive drive unit 200 is connected to the heat transfer sleeve 100, and the gradient temperature-sensitive drive unit 200 is used to generate a drive displacement based on the temperature drop signal. In this embodiment, the gradient temperature-sensitive drive unit 200 is used to receive the temperature drop signal transmitted by the heat transfer sleeve 100 and directly convert the temperature change of the heat absorption tube 10 into mechanical displacement output, thereby providing driving force for subsequent flow regulation.

[0027] The drive unit preferably employs a drive rod 201 structure formed by a gradient nesting of shape memory alloys with different phase transformation characteristic temperatures. For example, a combination of Ni-Ti alloy and Ni-Ti-Nb alloy can be used to form a double-layer gradient phase transformation system. Since different shape memory alloys have different austenite termination temperature Af and martensite initiation temperature Ms, when the heat absorber tube 10 experiences a temperature drop, different materials will undergo phase transformation and contraction sequentially in different temperature ranges, thereby forming a continuously superimposed displacement output process.

[0028] By introducing a gradient material system, a phase transformation compensation relationship is formed between different alloys. When one material enters the hysteresis range, another material continues to provide driving force, thereby effectively reducing the overall hysteresis loop and improving the stability of the driving response.

[0029] The gradient temperature-sensitive driving unit 200 includes a driving rod 201, which is formed by nesting at least two shape memory alloys with different phase transformation characteristic temperatures.

[0030] Specifically, the drive rod 201 in the gradient temperature-sensitive drive unit 200 is formed by gradient nesting of at least two shape memory alloys with different phase transformation characteristic temperatures, thereby constructing a thermal drive structure with multi-stage response characteristics.

[0031] The gradient nested structure enhances the mechanical stability of the overall drive rod 201, maintaining good fatigue resistance and structural strength under high-temperature cyclic conditions. Since the drive rod 201 directly utilizes the material crystal structure changes induced by temperature drop to generate driving force, it is a self-driven actuator utilizing thermal internal energy, requiring no additional electrical, hydraulic, or pneumatic energy to complete displacement output. The drive rod 201 not only achieves highly sensitive response to temperature drop signals but also further solves the problems of response hysteresis and inconsistent action that easily occur with traditional SMA materials under high-frequency thermal cycling conditions.

[0032] A cam mechanism 300 connected to the gradient temperature-sensitive drive unit 200, the nonlinear stress-compensated cam mechanism 300 is used to convert the drive displacement into a nonlinearly amplified adjustment stroke; In this embodiment, the cam mechanism 300 is used to further convert the linear displacement output by the gradient temperature-sensitive drive unit 200 into a nonlinear adjustment stroke that conforms to the thermal stress evolution law, and realize the geometric mapping of thermal stress response characteristics through a specific profile lead.

[0033] In the photothermal absorber tube 10, the relationship between temperature drop and thermal stress is usually not linear, especially in certain highly sensitive temperature regions, where even a very small temperature drop can lead to a sharp increase in thermal stress. By establishing a mapping relationship between temperature gradient, thermal stress, and valve displacement, the cam profile can have a larger lead change rate in the highly sensitive thermal stress region.

[0034] When the drive rod 201 produces a small displacement, the cam can rapidly amplify it into a larger valve core rotation angle through a high-slope profile segment, thereby achieving rapid reduction of the flow rate in the main channel 2. The cam profile can be constructed in reverse based on the thermal stress variation curve of the heat absorber tube 10 material in different temperature ranges. The target lead function is generated through nonlinear fitting and numerical integration, so that the mechanical motion law directly corresponds to the thermal stress growth law. It can enter a high-gain regulation state in the early stage of temperature drop, so that the valve action speed precedes the thermal stress formation speed.

[0035] The cam mechanism 300 includes: a shaped compensation cam 301 and a follower that cooperates with the shaped compensation cam 301; the contour curve of the shaped compensation cam 301 is determined according to the functional relationship between the temperature change of the heat absorber 10 and the equivalent thermal stress change, so as to increase the displacement magnification of the cam lead in the thermal stress sensitive range.

[0036] Specifically, the cam mechanism 300 employs a non-linear mechanical amplification structure formed by a non-shaped compensating cam 301 in conjunction with a follower. The profile curve of the non-shaped compensating cam 301 is not designed based on traditional mechanical transmission requirements, but rather constructed in reverse based on the functional relationship between the temperature change and the equivalent thermal stress change of the heat absorber 10. Because the thermal stress growth law of the solar-thermal heat absorber 10 typically exhibits non-linear characteristics under sudden cloud cover conditions, meaning that a rapid and sharp increase in thermal stress occurs within certain temperature ranges, if a conventional linear lead cam is still used, it will be impossible to establish a sufficiently large valve adjustment stroke in a timely manner within the critical thermal stress range.

[0037] By collecting thermal stress data of the heat absorber tube 10 material under different temperature conditions and establishing a mapping relationship between temperature gradient and equivalent thermal stress, a cam lead function is generated based on this mapping relationship, enabling the cam to have a higher displacement amplification factor in the thermal stress sensitive range. When the gradient temperature-sensitive drive unit 200 outputs a small displacement, the irregularly shaped compensation cam 301 can rapidly amplify this displacement using the high lead change segment and drive the downstream valve to move quickly, thereby completing the flow reconstruction in advance before the thermal stress reaches the dangerous peak. At the same time, in the temperature range where the thermal stress growth tends to be gradual, the cam lead gradually decreases to avoid valve overshoot and system oscillation. The cam mechanism 300 not only realizes the mechanical motion conversion but also further realizes the mechanized mapping of thermal stress characteristics, that is, solidifying the thermodynamic evolution law of the material into the mechanical contour structure.

[0038] A three-way plug valve 400 connected to the cam mechanism 300 is used to adjust the molten salt flow distribution between the main line 2 and the bypass line 3 based on the adjustment stroke; In this embodiment, the three-way plug valve 400 is used to dynamically reconstruct the molten salt flow between the main path 2 and the bypass path 3 according to the adjustment stroke output by the cam mechanism 300, thereby realizing the active and slow release of thermal shock to the heat absorption tube 10.

[0039] During normal operation of the solar thermal absorber, most of the high-temperature molten salt flows through the heated tube bundle via the main path 2 to maintain normal heat exchange efficiency. When cloud cover causes a sudden drop in temperature of the absorber tube 10, maintaining the original high flow rate would further exacerbate the cooling rate of the tube wall, leading to a rapid accumulation of thermal stress. A three-way stopcock valve rapidly redistributes the molten salt flow, quickly reducing the flow rate in the main path 2 under protection conditions and guiding more high-temperature molten salt to the bypass path 3 for circulation, thereby mitigating the cooling effect of the molten salt inside the absorber tube 10 on the tube wall.

[0040] The three-way plug valve 400 includes a valve body and a plug valve core rotatably disposed inside the valve body; the plug valve core is used to open the main circuit 2 in the first position and increase the flow rate of the bypass circuit 3 in the second position.

[0041] Specifically, the three-way plug valve 400 includes a valve body and a plug valve core disposed inside the valve body. The plug valve core can rotate between different positions to achieve flow redistribution between the main line 2 and the bypass line 3.

[0042] Under normal operating conditions of the solar thermal absorber, the stopcock valve core is in the first position, at which point the main circuit 2 remains fully open, and most of the high-temperature molten salt flows through the absorber tube 10 bundle to maintain normal heat exchange efficiency and power generation load. When the absorber tube 10 experiences a temperature drop and triggers a protection action, the cam mechanism 300 drives the stopcock valve core to rotate to the second position, gradually reducing the flow rate of the main circuit 2 while increasing the flow rate proportion of the bypass 3. This quickly weakens the cooling effect of the molten salt inside the absorber tube 10 on the tube wall. As the molten salt flow rate decreases, its residence time inside the absorber tube 10 increases, resulting in a corresponding increase in fluid temperature rise, thus creating a compensating heating effect on the tube wall to offset the cold shock caused by a sudden drop in external irradiance. In addition, the bypass 3 can handle more high-temperature molten salt circulation flow, thereby avoiding excessive flow fluctuations in the overall heat exchange loop of the system. The system can quickly complete flow reconstruction in the early stages of thermal shock formation, effectively reducing the peak thermal stress of the absorber tube 10 and avoiding low-cycle fatigue damage caused by thermal stress concentration.

[0043] Furthermore, the three-way plug valve 400 also includes: a thermocoupled bridge plate 401 and a molten salt inlet 1; the molten salt inlet 1 is used to supply high-temperature molten salt medium to the main line 2 and the bypass 3; the thermocoupled bridge plate 401 is spanned between the main line 2 and the bypass 3 and is used to conduct heat from the bypass 3 to the main line 2.

[0044] Specifically, the three-way plug valve 400 is equipped with a thermocoupled bridge plate 401, which spans between the main circuit 2 and the bypass circuit 3, and is used to continuously transfer the high temperature heat in the bypass circuit 3 to the main circuit 2 under the protection condition.

[0045] During the thermal stress protection process, the flow rate of main circuit 2 is significantly reduced. Therefore, without an additional thermal compensation mechanism, the molten salt inside main circuit 2 may experience crystallization and blockage due to excessively rapid temperature drop. By setting a high thermal conductivity thermocoupler 401, the high-temperature molten salt in bypass 3 can continuously release heat to main circuit 2 through thermal conduction. Even if the flow rate of main circuit 2 has decreased to a low level, the molten salt inside main circuit 2 can still be kept in a safe temperature range above the crystallization point. Preferably, the thermocoupler 401 can be made of a high-temperature resistant and high thermal conductivity alloy material, thus balancing thermal conductivity and high-temperature structural stability. This can suppress thermal stress while preventing blockage or solidification accidents in the molten salt system due to low-temperature crystallization, thereby achieving passive protection under all operating conditions.

[0046] At least one micro-circulation adjustment groove 402 is provided on the side of the plug valve core facing the outlet 2 of the main line 2. The micro-circulation adjustment groove 402 is used to maintain the micro-flow circulation of the main line 2 when the main line 2 is in the protection condition.

[0047] At least one micro-circulation regulating groove 402 is provided on the side of the plug valve core facing the outlet 2 of the main line 2. This is used to maintain a certain scale of micro-flow circulation inside the main line 2 even after the system enters the thermal stress protection condition. Because the flow rate of the main line 2 is rapidly reduced by the three-way plug valve 400 under conditions such as sudden cloud cover, to mitigate the cooling effect of the molten salt inside the heat absorber tube 10 on the tube wall, if the main line 2 is completely cut off, the molten salt is prone to crystallization, solidification, or even blockage due to a continuous drop in local temperature under high-temperature heat exchange conditions. By providing the micro-circulation regulating groove 402 on the surface of the plug valve core, even when the valve core has rotated to a position close to the closed main line 2, a small flow channel can still be formed between the valve core and the valve body, allowing a small amount of high-temperature molten salt to continuously flow through the main line 2 tube bundle, thereby establishing a stable micro-circulation flow state. Furthermore, because the micro-circulation flow rate is small, the cooling effect on the wall of the heat absorber tube 10 is significantly reduced, preventing the re-induction of large thermal stress fluctuations, thus balancing the requirements of thermal shock suppression and molten salt insulation.

[0048] The microcirculation adjustment groove 402 is configured as a V-shaped groove.

[0049] Further improve the stability of the micro-flow regulation process in main line 2. Compared with rectangular grooves, circular arc grooves, or ordinary straight groove structures, V-grooves can form a smoother flow area change pattern during valve core rotation. When the plug valve core gradually approaches the closed position of main line 2, the tip area of ​​the V-groove will first retain a very small flow cross section, thus allowing a small amount of molten salt to continue flowing; as the valve core position changes further, the opening area of ​​the V-groove will gradually increase or decrease according to a geometric gradient law, making the micro-circulation flow exhibit a continuous gradient characteristic.

[0050] The profile lead of the cam mechanism 300 is constructed based on the response relationship between the temperature gradient and the equivalent thermal stress of the heat absorber 10. This is used by the three-way stopcock valve 400 to nonlinearly adjust the flow rate of the main circuit 2 when the temperature of the heat absorber 10 drops, and to suppress the rise of transient thermal stress in the heat absorber 10.

[0051] In this embodiment, the thermal stress of the heat absorber 10 does not increase uniformly with decreasing temperature, but rather exhibits a significant surge within a specific temperature range, i.e., a highly sensitive thermal stress region. Within this range, even a small temperature drop can lead to a rapid amplification of the internal thermal strain of the material, quickly approaching its fatigue limit. By collecting, fitting, and mapping the temperature change-thermal stress data of the heat absorber 10 material, the thermal stress growth law is directly converted into a cam lead function, giving the cam a higher displacement amplification factor within the thermal stress sensitive region. Thus, when the heat absorber 10 experiences an initial temperature drop, the drive unit only produces a small displacement, allowing the cam mechanism 300 to quickly output a large-angle valve action, achieving advanced regulation of the flow rate in the main path 2. As the temperature drop further increases, the cam lead gradually enters a flattening region, thereby avoiding valve overshoot and system oscillation.

[0052] In some possible implementations, the system further includes a reset spring; the reset spring is connected to the gradient temperature-sensitive drive unit 200 and is used to drive the three-way stop valve 400 back to the rated flow state after the temperature of the heat absorber tube 10 recovers.

[0053] In this embodiment, under protective conditions such as sudden cloud cover changes, the gradient temperature-sensitive drive unit 200 triggers phase change contraction due to temperature drop, and pushes the three-way plug valve 400 into the main circuit 2 flow-limiting state through the cam mechanism 300. However, when the clouds dissipate and solar radiation recovers, the temperature of the heat absorber tube 10 will rise again. If the valve is reset solely by the restoring force of the shape memory alloy, the reset speed may be insufficient due to material thermal hysteresis, valve core friction resistance, and fluid pressure difference, thus causing the system to maintain a low flow state for a long time, affecting the normal heat exchange efficiency and power output of the solar thermal power plant. By setting a reset spring, an additional mechanical reset force is formed during the temperature recovery phase. When the gradient temperature-sensitive drive unit 200 gradually returns to its original length, the reset spring will release elastic potential energy simultaneously, and together with the restoring force of the drive unit, it will act on the cam mechanism 300 and the three-way plug valve 400, thereby quickly overcoming the static friction of the valve core and fluid resistance, allowing the valve to quickly return to the normal flow position.

[0054] Furthermore, the return spring can also preload the drive mechanism during system operation, thereby reducing mechanical backlash and motion lag, and improving the response consistency of the entire mechanical transmission chain. Since the reset process is completed purely mechanically, even in the event of an external power system failure, the valve can still achieve autonomous reset by relying on the material's restoring force and the spring's elastic potential energy, thus ensuring the system possesses complete closed-loop autonomous capability.

[0055] Figure 2 A schematic diagram of the thermal stress suppression method provided in the embodiments of this disclosure; as shown Figure 2 As shown, this disclosure also provides a method for suppressing thermal stress, including: step S1, sensing the temperature change of the heat-absorbing tube 10 through the heat transfer sleeve 100; step S2, driving the gradient temperature-sensitive drive unit 200 to generate a displacement based on the temperature change; step S3, nonlinearly amplifying the displacement through the cam mechanism 300 to obtain the amplified adjustment stroke; step S4, driving the three-way stopcock valve 400 to adjust the flow distribution between the main circuit 2 and the bypass circuit 3 based on the amplified adjustment stroke; step S5, suppressing the growth of thermal stress in the heat-absorbing tube 10 through the flow distribution between the main circuit 2 and the bypass circuit 3.

[0056] In some possible ways of implementation, Figure 3 This is a schematic diagram comparing the adjustment characteristic response of this disclosure embodiment with that of the prior art under different wall temperature conditions; as shown. Figure 3 As shown, the heat transfer sleeve 100, namely the liquid metal high transient heat transfer sleeve 100: The sleeve 100 is a double-layer flexible metal structure that tightly wraps around the backlight side wall of the heat absorber tube 10. A gallium-indium liquid metal layer is sandwiched inside the sleeve 100. The heat transfer sleeve 100 is connected to the gradient temperature-sensitive drive unit 200 via a thermally conductive corrugated pipe. Utilizing the high thermal conductivity and contactless thermal resistance of the liquid metal, the tube wall temperature drop signal can be transmitted to the internal temperature sensing element at millisecond speeds.

[0057] Gradient temperature-sensitive drive unit 200: The unit is housed within a sealed stainless steel corrugated sleeve, with its core being a drive rod 201 composed of a gradient nesting of Ni-Ti-Nb alloy and Ni-Ti alloy. The proximal end of the drive rod 201 is fixed, while the distal end passes through the sleeve 100 and connects to the driven push rod of the cam mechanism 300. The two materials have different phase transition characteristic temperatures, and the resulting stress compensation effect can counteract the inherent thermal hysteresis of a single SMA material.

[0058] Nonlinear stress-compensating cam mechanism 300: The mechanism includes a planar cam 301 with an irregular profile and a roller follower. The profile lead of the irregular compensating cam 301 is generated by nonlinear fitting based on the "temperature gradient-thermal stress" response function of the heat absorber tube 10 material. The input end of the irregular compensating cam 301 is connected to the drive rod 201, and the output end drives the three-way plug valve 400 to rotate via a rotating shaft.

[0059] 400 self-balancing thermally compensated three-way plug valve: The valve includes a valve body, a rotary plug valve core, and a thermocoupler bridge 401 integrated inside the valve body. The plug valve core has a V-shaped micro-circulation adjustment groove 402 engraved on the end facing the outlet of the main line 2. The thermocoupler bridge 401 is installed between the bypass 3 and the main line 2 to achieve passive heat exchange under protection conditions.

[0060] Cam profile design method: The study employed measured or simulated data pairs of "pipe wall temperature change - thermal stress". Thermal stress values ​​(in MPa) were recorded every 5°C as the temperature decreased from 565°C to 450°C. This data was normalized to obtain a curve showing the relationship between stress growth rate and temperature drop. This curve was then converted into a relationship between the expected displacement and rotation angle of the cam follower. Specifically, the lift h(θ) of the cam follower and the stress σ(T) satisfy dh / dθ = k dσ / dT, where k is the proportionality coefficient. The polar coordinate equation of the cam profile is obtained through numerical integration. The cam profile is generated using the equation and verified by motion simulation. In the initial stage of temperature drop (within 500ms), the cam lead angle linearly increases from 0° to 45°, corresponding to the valve core rotation angle increasing from 0° to 70°.

[0061] Parameters of gradient SMA drive lever 201: The drive rod 201 is composed of an inner Ni-Ti alloy layer (6 mm in diameter) and an outer Ni-Ti-Nb alloy layer (2 mm in wall thickness). The austenite termination temperature (Af) of the inner Ni-Ti alloy is 80℃, and the martensite initiation temperature (Ms) is 40℃; the outer Ni-Ti-Nb alloy has Af = 120℃ and Ms = 70℃. During the cooling process, the two alloys undergo phase transformations sequentially, and the resulting contraction forces are superimposed, making the overall drive displacement curve approximately two linearly superimposed segments, effectively eliminating the hysteresis loop of a single material. Experiments show that using this gradient rod reduces the displacement hysteresis during heating and cooling processes from 25℃ to 8℃ compared to using a single material.

[0062] Parameters of V-shaped micro-circulation adjustment groove 402: Six V-shaped grooves are evenly spaced on the valve core at the outlet side of main line 2, with a groove depth of 3mm, a groove width of 2mm, and an included angle of 60°. Molten salt flow simulation shows that when the valve core of main line 2 is in the closed position (70° angle), these V-shaped grooves can still maintain approximately 3% of the rated flow rate (i.e., micro-circulation flow rate). Combined with a thermocoupled bridge plate 401 (made of Inconel 625, with a thermal conductivity of approximately 21W / m·K), the molten salt temperature within the main line 2 pipe bundle can be maintained above 320°C (crystallization point of 290°C) when the bypass temperature is 530°C, providing a safety margin of approximately 30°C.

[0063] Protection implementation process: Rated heat exchange stage (steady-state operation): When the heat-receiving surface of the heat absorber tube 10 is in the normal operating range of 530℃~565℃, the drive rod 201 is in the austenitic phase elongation state, and the output displacement is locked at the low lead starting section of the irregular compensation cam 301. The three-way plug valve 400 maintains 2100% flow in the main circuit, and the molten salt exchanges heat at full speed.

[0064] Figure 4 This is a schematic diagram comparing the equivalent thermal stress of the pipe wall under sudden cloud cover conditions with that of the prior art, provided as an embodiment of this disclosure. Figure 4 As shown, the stress burst suppression stage (nonlinear energy dissipation): Cloud cover triggers a sudden change in radiation, causing a temperature drop in the pipe wall. The liquid metal sleeve 100 instantly transmits the signal to the drive rod 201, inducing the alloy to transform from austenite to martensite and contract. The drive rod 201 pulls the irregularly shaped compensation cam 301 into a high-slope transition section, where the minimal linear displacement of the SMA is instantly amplified into a large-angle rotation of the valve core. The valve core rapidly reduces the flow rate of the main line 2, artificially increasing the temperature rise of the pipe wall by utilizing the principle of "reduced flow rate, increased temperature rise" to counteract the cold shock. Measured data shows that a significant flow diversion can be completed within 500ms before the temperature drop, suppressing the peak thermal stress within a safe range.

[0065] Dynamic antifreeze protection phase (self-heating balance): After the system enters protection mode, most of the high-temperature molten salt flows through bypass 3. The heat energy of bypass 3 is continuously conducted to main circuit 2 through the thermocoupled bridge plate 401. At the same time, the V-shaped micro-orifice 402 on the plug valve core ensures that a micro-flow of 2.5% to 3.5% still flows through main circuit 2. This "conductive heat + micro-convection" mechanism ensures that even in extremely cold environments, the temperature of the molten salt in main circuit 2 is always maintained at approximately 30°C above the crystallization point.

[0066] Cloud cover recovery phase (rapid reset): After the temperature rise caused by irradiation recovery, the rapid reset section in drive rod 201 and the reset spring generate a combined force, quickly overcoming the static friction of the valve seat, causing the cam to reset and driving the valve back to the rated flow mode. The complementary properties of the gradient materials avoid response overshoot or secondary impact.

[0067] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0068] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A heat absorber system, characterized in that, include: Heat absorption tube; A heat transfer sleeve is disposed on the back side wall of the heat absorption tube. The heat transfer sleeve is used to sense the temperature change of the heat absorption tube and transmit the temperature drop signal. A gradient temperature-sensitive drive unit connected to the heat transfer sleeve is used to generate a drive displacement based on the temperature drop signal. A cam mechanism connected to the gradient temperature-sensitive drive unit, wherein the nonlinear stress-compensated cam mechanism is used to convert the drive displacement into a nonlinearly amplified adjustment stroke; A three-way plug valve connected to the cam mechanism, the three-way plug valve being used to adjust the molten salt flow distribution between the main path and the bypass based on the adjustment stroke; Specifically, the profile lead of the cam mechanism is constructed based on the response relationship between the temperature gradient and the equivalent thermal stress of the heat absorber tube. This is used by the three-way plug valve to nonlinearly adjust the main flow rate when the temperature of the heat absorber tube drops, and to suppress the rise of transient thermal stress in the heat absorber tube.

2. The absorber system according to claim 1, characterized in that, The heat transfer sleeve is configured with a double-layer structure, with a liquid metal medium in the inner interlayer. The liquid metal medium is used to transmit the temperature change of the heat absorption tube wall to the gradient temperature-sensitive drive unit.

3. The heat absorber system according to claim 1, characterized in that, The gradient temperature-sensitive driving unit includes: A drive rod, which is formed by nesting at least two shape memory alloys with different phase transformation characteristic temperatures.

4. The absorber system according to claim 1, characterized in that, The cam mechanism includes: An irregularly shaped compensating cam and a follower that cooperates with the irregularly shaped compensating cam; The contour curve of the irregularly shaped compensating cam is determined based on the functional relationship between the temperature change of the heat absorber and the equivalent thermal stress change, and is used to increase the displacement amplification factor of the cam lead within the thermal stress sensitive range.

5. The absorber system according to claim 1, characterized in that, The three-way plug valve includes: The valve body and the plug valve core rotatably disposed inside the valve body; The plug valve core is used to open the main circuit in the first position and increase the flow rate of the bypass in the second position.

6. The absorber system according to claim 5, characterized in that, The three-way plug valve also includes: Thermally coupled bridge plate and molten salt main inlet; The main molten salt inlet is used to supply high-temperature molten salt medium to the main road and bypass; The thermal coupling bridge is installed between the main road and the bypass road to conduct heat from the bypass road to the main road.

7. The absorber system according to claim 5, characterized in that, The plug valve core is provided with at least one micro-circulation adjustment groove on the outlet side facing the main road. The micro-circulation adjustment groove is used to maintain a micro-flow circulation of the main road when the main road is in a protection condition.

8. The absorber system according to claim 7, characterized in that, The microcirculation adjustment groove is configured as a V-shaped groove.

9. The absorber system according to claim 1, characterized in that, Also includes: Return spring; The reset spring is connected to the gradient temperature-sensitive drive unit and is used to drive the three-way stop valve back to the rated flow state after the temperature of the heat absorber tube recovers.

10. A method for suppressing thermal stress, characterized in that, For controlling the absorber protection system according to any one of claims 1 to 9, comprising: The temperature change of the heat absorption tube is sensed by the heat transfer sleeve; Displacement is generated by the gradient temperature-sensitive driving unit based on the temperature change. The displacement is nonlinearly amplified by a cam mechanism to obtain the amplified adjustment stroke. Based on the amplified adjustment stroke, the three-way plug valve is driven to adjust the flow distribution between the main circuit and the bypass; The flow distribution between the main path and the bypass suppresses the growth of thermal stress in the heat absorption tube.

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