Integrated flexible deployable radiator of integrated micro-channel and on-orbit deployment method of integrated flexible deployable radiator

Abstract

The invention relates to the technical field of radiators, in particular to an integrated flexible deployable radiator of an integrated micro-channel and an on-orbit deployment method thereof.The integrated flexible deployable radiator comprises a radiator body and a plurality of deployable rotating bases, the deployable rotating bases are symmetrically installed on the side wall of the radiator body, and rotating shafts are arranged on the outer side walls of the deployable rotating bases; the outer side walls of the rotating shafts are coaxially connected with the inner side walls of the radiant panels, and connecting shafts are arranged on the side walls of the radiant panels and connected with the adjacent radiant panels. According to the invention, the filling pressure of the cooling liquid in the heat exchange pipe and the integrated micro-channel layer is set as the unfolding driving force, so that the radiant panel does not need mechanical mechanisms such as a complex spring, a gear or a motor in the unfolding process, and the clamping stagnation and failure risks in the on-orbit unfolding process are reduced; the cooling liquid flow channel and the flexible composite base material form an integral structure, contact thermal resistance between a traditional separated pipeline and the radiant panel is avoided, and the conduction efficiency of heat from a spacecraft to a radiant surface is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radiators, in particular to an integrated flexible deployable radiator with integrated micro flow channels and a method for deploying the radiator in orbit. BACKGROUND

[0002] The heat conduction system of the existing flexible radiator mostly adopts a combination mode of external heat pipes or fluid circuits pasted or bundled with the radiation film. This separated structure has many inherent defects. On the one hand, the contact thermal resistance of the connection interface is large, which leads to low heat transfer efficiency from the fluid circuit to the radiation surface, and it is difficult to meet the rapid heat dissipation demand of high-power chips, especially in high heat flux density scenarios such as H100 clusters, the thermal resistance bottleneck will directly cause the chip to overheat.

[0003] On the other hand, the pasting or bundling connection mode has insufficient reliability. During the satellite launch stage and the in-orbit deployment process, problems such as pipe falling off and folding damage are prone to occur, which seriously affects the stability of the thermal control system.

[0004] In addition, the separated design increases the structural complexity of the radiator, and the folded volume and weight are relatively large, which is not conducive to the batch launch and deployment of satellites. With the development of space data centers to GW-level scale, the radiator needs to have larger heat dissipation area and higher system reliability. The traditional separated structure has been difficult to adapt to this development trend, and an innovative integrated design solution is urgently needed. SUMMARY

[0005] The purpose of the present application is to solve the problems of low heat conduction efficiency, insufficient connection reliability and high structural complexity in the prior art, and to provide an integrated flexible deployable radiator with integrated micro flow channels and a method for deploying the radiator in orbit.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: The integrated flexible deployable radiator with integrated micro flow channels and the method for deploying the radiator in orbit comprise a radiator and a plurality of deployable rotating seats, the deployable rotating seats are symmetrically installed on the side wall of the radiator, the outer side wall of the deployable rotating seat is provided with a rotating shaft, the outer side wall of the rotating shaft is coaxially connected with the inner side wall of the radiation plate, the side wall of the radiation plate is provided with a connecting shaft, the connecting shaft connects adjacent radiation plates, and the radiation plate is a multi-layer composite flexible structure.

[0007] Preferably, the radiation plate is provided with a selective radiation coating, the selective radiation coating is coated on the surface of the radiation plate by using a vacuum sputtering process, and the thickness of the selective radiation coating is 0.1-0.3mm.

[0008] Preferably, the radiation plate is provided with a flexible composite substrate made of graphite foil material and metalized PI film, with a thickness of 0.1-0.3mm, a thermal conductivity coefficient not less than 300W / (m·K), and resistance to space high and low temperature, radiation resistance and fatigue resistance.

[0009] Preferably, the radiation plate surface is provided with a plurality of heat conduction grooves, the groove width is 0.5-1mm, the groove depth is 0.3-0.5mm, and the heat conduction groove 5 spacing is 3-5mm.

[0010] Preferably, the deployable rotating seat is made of lightweight aluminum alloy, and the inside of the deployable rotating seat is provided with a bearing structure matched with the rotating shaft, and the bearing is a ceramic bearing with high temperature resistance and low friction coefficient, which ensures the rotation of the rotating shaft in the space temperature range of-30℃ to +50℃.

[0011] Preferably, the exchange heat pipe is installed on the inside wall of the integrated micro-channel layer, the exchange heat pipe is made of flexible stainless steel pipe, the diameter is matched with the main channel of the micro-channel, the pipe wall thickness is 0.1-0.2mm, and the connection between the exchange heat pipe and the integrated micro-channel layer is sealed by vacuum brazing process, which ensures no cooling liquid leakage.

[0012] Preferably, the radiation plate is provided with an integrated micro-channel layer, the integrated micro-channel layer is provided with a heat insulation cavity, the heat insulation cavity is a closed cavity, the heat insulation cavity is filled with inert gas, the inert gas is a low thermal conductivity inert gas, preferably one of xenon gas and argon gas, the gas pressure is 0.01-0.03MPa, the sealing plate is made of flexible sealing material, and the sealing plate and the end part of the heat insulation cavity are sealed by laser welding.

[0013] Preferably, the radiation plate can be folded and unfolded through the rotating shaft and the connecting shaft, and the unfolding angle is 0-120°.

[0014] Preferably, the radiation plate is provided with a heat insulation layer, the heat insulation layer is a thin film composite material, the heat insulation layer is composed of a plurality of layers of vacuum aluminum-plated polyester film and aerogel, and the thickness of the heat insulation layer is controlled within the range of 0.2-0.5mm.

[0015] Preferably, the in-orbit unfolding method of the integrated flexible deployable radiator of the integrated micro-channel is as follows: S1: folding and fixing before launching; Before launching the spacecraft, a plurality of radiation plates are sequentially folded in a laminated manner through the connecting shaft, so that each radiation plate is folded around the rotating shaft to the radiator body direction to form a compact folded state; After folding, the position of the radiation plate is limited and the angle is constrained through the deployable rotating seat, so that the whole radiator is in a safe locking state for launching.

[0016] S2: Orbiting state monitoring and deployment preparation; After the spacecraft enters the predetermined orbit and completes attitude stabilization, the control system detects the temperature of the area where the radiator is located, the structural state, and the sealing of the fluid circuit; When it is confirmed that the radiator meets the deployment conditions, the locking constraint on the deployable rotating seat is released, and the rotating shaft is in a freely rotatable state.

[0017] S3: Cooling liquid synchronous filling and driving deployment; Start the cooling liquid circuit of the thermal control system, and inject the cooling liquid into the heat exchange pipe and the integrated micro-channel layer; As the cooling liquid continues to fill, a stable fluid pressure is formed inside the micro-channel, which together with the self-flexible restoring force of the radiation plate drives the radiation plate to gradually expand outward around the rotating shaft, realizing "fluid synchronous filling-structure synchronous deployment".

[0018] S4: Multi-stage radiation plate linkage deployment; While a single radiation plate is deployed, the adjacent radiation plates are linked through the connecting shaft to rotate, so that multiple radiation plates are deployed in a predetermined deployment sequence; During the deployment process, the deployment angle of the radiation plate is guided and controlled by the deployable rotating seat, and the deployment angle gradually increases to 0-120° in the preset range.

[0019] S5: Deployment to position and attitude stabilization; When each radiation plate reaches the set deployment angle, the deployable rotating seat limits the angle of the rotating shaft to prevent the radiation plate from over-rotating or rebounding; At this time, the radiation plate forms a stable deployed radiation surface structure, and the radiator as a whole enters the stable deployed state in orbit.

[0020] S6: In-orbit heat dissipation operation; The cooling liquid flows along the heat-conducting grooves and micro-channel networks in the integrated micro-channel layer, and fully exchanges heat with the flexible composite substrate; The selective radiation coating on the surface of the radiation plate releases the absorbed heat in the form of infrared radiation to the outer space, realizing continuous and efficient heat dissipation of the spacecraft.

[0021] S7: Long-term in-orbit operation guarantee; During the long-term in-orbit operation of the radiator, the heat insulation layer and the heat insulation cavity work together to reduce heat loss in the non-radiation direction; The inert gas forms a stable low-conductivity environment in the heat insulation cavity, reducing the thermal shock on the micro-channel structure and the heat exchange pipe caused by extreme temperature differences in space, and ensuring the stable and reliable operation of the radiator under multiple thermal cycles.

[0022] Compared with the prior art, the present application has the following advantages: 1. The present application sets the filling pressure of the cooling liquid in the heat exchange pipe and the integrated micro-channel layer as the unfolding driving force, so that the radiator does not need complex mechanical mechanisms such as springs, gears or motors in the unfolding process, reduces the risk of jamming and failure in the on-orbit unfolding process, and sets the integrated micro-channel layer to form an overall structure of the cooling liquid channel and the flexible composite substrate, avoids the contact thermal resistance between the traditional separated pipeline and the radiator, and improves the conduction efficiency of heat from the spacecraft to the radiation surface.

[0023] 2. The present application sets the heat conduction groove to make the heat quickly spread on the surface of the radiator and fully exchange heat with the cooling liquid flowing in the micro-channel, effectively reduces the local hot spots, improves the overall radiation efficiency, sets the integrated micro-channel layer to form an overall structure of the cooling liquid channel and the flexible composite substrate, avoids the contact thermal resistance between the traditional separated pipeline and the radiator, and improves the conduction efficiency of heat from the spacecraft to the radiation surface. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 An isometric view of the integrated micro-channel integrated flexible deployable radiator proposed by the present application; Figure 2 A top view of the radiator of the integrated micro-channel integrated flexible deployable radiator proposed by the present application; Figure 3 A cutaway side view of the radiator of the integrated micro-channel integrated flexible deployable radiator proposed by the present application; Figure 4 A cutaway side view of the radiator of the integrated micro-channel integrated flexible deployable radiator proposed by the present application; Figure 5 A cutaway top view of the radiator of the integrated micro-channel integrated flexible deployable radiator proposed by the present application; Figure 6 A cutaway top view of the radiator of the integrated micro-channel integrated flexible deployable radiator proposed by the present application; Figure 7 A use flowchart of the integrated micro-channel integrated flexible deployable radiator and its on-orbit unfolding method proposed by the present application; Figure 8 An on-orbit flowchart of the integrated micro-channel integrated flexible deployable radiator and its on-orbit unfolding method proposed by the present application.

[0025] In the figure: 1, radiator; 2, deployable rotating seat; 3, rotating shaft; 4, radiator; 401, selective radiation coating; 402, flexible composite substrate; 403, integrated micro-channel layer; 404, heat insulation layer; 5, heat conduction groove; 6, micro-flow structure; 7, connecting shaft; 8, heat exchange pipe; 9, heat insulation cavity; 10, sealing plate; 11, inert gas. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application.

[0027] Referring to Figures 1-8 , the integrated flexible deployable radiator with micro flow channels and the on-orbit deployment method thereof include a radiator 1 and a plurality of deployable rotating seats 2. The deployable rotating seats 2 are symmetrically arranged on the side wall of the radiator 1. The outer side wall of the deployable rotating seat 2 is provided with a rotating shaft 3, so that the radiation plate 4 can rotate and deploy around the rotating shaft 3, thereby improving the radiation efficiency and enhancing the stability and durability of the structure.

[0028] As shown in Figure 1 , the outer side wall of the rotating shaft 3 and the inner side wall of the radiation plate 4 are coaxially connected. The side wall of the radiation plate 4 is provided with a connecting shaft 7. The connecting shaft 7 connects adjacent radiation plates 4. The deployable rotating seat 2 is made of lightweight aluminum alloy. The inside of the deployable rotating seat 2 is provided with a bearing structure matched with the rotating shaft 3. The bearing is a ceramic bearing with high temperature resistance and low friction coefficient, which ensures the rotation of the rotating shaft 3 within a space temperature range of -30℃ to +50℃, reduces the overall weight, and ensures reliable operation under extreme space temperature conditions.

[0029] The radiation plate 4 can be folded and unfolded through the rotating shaft 3 and the connecting shaft 7. The unfolding angle is 0-120°, so that the radiator 1 can be compactly folded in the emission stage to reduce the occupied space, and can be fully unfolded after entering the orbit to realize efficient heat radiation.

[0030] As shown in Figure 4 , the radiation plate 4 is a multi-layer composite flexible structure. The radiation plate 4 is provided with a selective radiation coating 401. The selective radiation coating 401 is coated on the surface of the radiation plate 4 by using a vacuum sputtering process. The thickness of the selective radiation coating 401 is 0.1-0.3mm, which ensures uniform and firm adhesion of the coating. At the same time, the thickness range can ensure good radiation performance while controlling the overall weight of the radiation plate.

[0031] As shown in Figure 4 , the radiation plate 4 is provided with a flexible composite substrate 402. The flexible composite substrate 402 is made of graphite foil material and metalized PI film. The thickness of the flexible composite substrate 402 is 0.1-0.3mm, the thermal conductivity coefficient is not less than 300W / (m·K), and it has the properties of space high and low temperature resistance, radiation resistance and fatigue resistance. Therefore, the flexible composite substrate 402 has good flexibility and can efficiently conduct heat, meeting the thermal control requirements of the spacecraft in complex space environment.

[0032] As shown in Figure 2As shown, multiple heat-conducting grooves 5 are formed on the surface of the radiant plate 4. The groove width of the heat-conducting groove 5 is 0.5-1mm, the groove depth is 0.3-0.5mm, and the spacing between the heat-conducting grooves 5 is 3-5mm. This increases the surface area of ​​the radiant plate 4, promotes the heat exchange efficiency between the coolant and the radiant plate 4, and also helps to guide the flow direction of the coolant and improve the uniformity of heat dissipation.

[0033] like Figure 5 As shown, the radiating plate 4 has an integrated microchannel layer 403, and the integrated microchannel layer 403 has a heat insulation cavity 9. The heat insulation cavity 9 is a closed cavity and is filled with an inert gas 11. The inert gas 11 is a low thermal conductivity inert gas, preferably one of xenon or argon, with a gas pressure of 0.01-0.03 MPa. The sealing plate 10 is made of flexible sealing material, and the sealing plate 10 and the end of the heat insulation cavity 9 are sealed by laser welding, which effectively reduces heat conduction, reduces heat loss in the non-radiation direction, improves the thermal control efficiency of the radiator, and ensures the sealing and stability of the heat insulation cavity.

[0034] like Figure 5 As shown, the radiating plate 4 is provided with a heat insulation layer 404. The heat insulation layer 404 is a thin film composite material. The heat insulation layer 404 is made of multi-layer vacuum-metallized polyester film and aerogel. The thickness of the heat insulation layer 404 is controlled within the range of 0.2-0.5mm, which effectively blocks the heat transfer in the space environment, reduces heat loss in the non-radiative direction, and ensures the stable operation of the radiator in the complex space thermal environment.

[0035] The working principle of this invention is as follows: S1: Folding and securing before launch; Before the spacecraft is launched, multiple radiating plates are folded in sequence through connecting shafts, so that each radiating plate is gathered around the rotation axis in the direction of the radiator body, forming a compact folded state. After folding, the position and angle of the radiator are limited by the unfoldable rotating seat, so that the radiator as a whole is in a safe and locked state for launch.

[0036] S2: Orbit insertion status monitoring and deployment preparation; After the spacecraft enters its predetermined orbit and achieves attitude stabilization, the control system monitors the temperature, structural condition, and fluid loop sealing of the radiator area. Once it is confirmed that the radiator meets the deployment conditions, the locking constraint on the deployable rotating base is released, allowing the rotating shaft to rotate freely.

[0037] S3: Coolant synchronous charging drive deployment; Start the thermal control system coolant circuit and inject coolant into the heat exchange tubes and integrated microchannel layer; As coolant continues to be injected, a stable fluid pressure is formed inside the microchannel. This fluid pressure, together with the flexible restoring force of the radiating plate itself, drives the radiating plate to gradually unfold outward around the rotation axis, achieving "synchronous fluid injection - synchronous structural unfolding".

[0038] S4: Multi-level radiant panels deploy in tandem; While a single radiating plate unfolds, adjacent radiating plates rotate in tandem via a connecting shaft, causing multiple radiating plates to unfold sequentially according to a preset unfolding order. During the unfolding process, the unfolding angle of the radiant plate is guided and controlled by the unfoldable rotating seat, and the unfolding angle gradually increases to 0–120° within the preset range.

[0039] S5: Deployment in place and stable posture; Once each radiating plate reaches the set unfolding angle, the rotating seat can be unfolded to limit the angle of the rotating shaft, preventing the radiating plate from rotating excessively or springing back. At this point, the radiating plate forms a stable unfolding radiating surface structure, and the radiator as a whole enters a stable on-orbit unfolding state.

[0040] S6: On-orbit cooling operation; The coolant flows along the heat-conducting grooves and microchannel network within the integrated microchannel layer, fully exchanging heat with the flexible composite substrate. The selective radiation coating on the surface of the radiating plate releases the absorbed heat into outer space in the form of infrared radiation, achieving continuous and efficient heat dissipation for the spacecraft.

[0041] S7: Long-term on-orbit operation support; During the long-term on-orbit operation of the radiator, the heat insulation layer and the heat insulation cavity work together to reduce heat loss in non-radiative directions; The inert gas creates a stable, low thermal conductivity environment within the insulation cavity, reducing the thermal shock caused by extreme temperature differences in the space to the microfluidic structure and heat exchange tubes, and ensuring the radiator operates stably and reliably under multiple thermal cycles.

[0042] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An integrated flexible deployable radiator with integrated microchannels, comprising a radiator (1) and multiple deployable rotating seats (2), wherein the deployable rotating seats (2) are symmetrically mounted on the sidewall of the radiator (1), characterized in that, The outer wall of the deployable rotating seat (2) is provided with a rotating shaft (3). The outer wall of the rotating shaft (3) and the inner wall of the radiation plate (4) are coaxially connected. The side wall of the radiation plate (4) is provided with a connecting shaft (7). The connecting shaft (7) connects adjacent radiation plates (4). The radiation plate (4) is a multi-layer composite flexible structure.

2. The integrated flexible deployable radiator with integrated microchannels according to claim 1, characterized in that, The radiation plate (4) is provided with a selective radiation coating (401), which is applied to the surface of the radiation plate (4) by vacuum sputtering process, and the thickness of the selective radiation coating (401) is 0.1-0.3 mm.

3. The integrated flexible deployable radiator with integrated microchannels according to claim 2, characterized in that, The radiant plate (4) is provided with a flexible composite substrate (402). The flexible composite substrate (402) is made of graphite foil material and metallized PI film. Its thickness is 0.1-0.3mm, its thermal conductivity is not less than 300W / (m·K), and it has the properties of being resistant to high and low temperatures in space, radiation resistance and fatigue resistance.

4. The integrated flexible deployable radiator with integrated microchannels according to claim 3, characterized in that, The surface of the radiant plate (4) is provided with a plurality of heat conduction grooves (5), the width of the heat conduction grooves (5) is 0.5-1mm, the depth of the grooves is 0.3-0.5mm, and the spacing between the heat conduction grooves (5) is 3-5mm.

5. The integrated flexible deployable radiator with integrated microchannels according to claim 4, characterized in that, The deployable rotating seat (2) is made of lightweight aluminum alloy. The interior of the deployable rotating seat (2) is equipped with a bearing structure adapted to the rotating shaft (3). The bearing is a high-temperature resistant, low-friction coefficient ceramic bearing to ensure that the rotating shaft (3) rotates within a space temperature range of -30℃ to +50℃.

6. The integrated flexible deployable radiator with integrated microchannels according to claim 5, characterized in that, The heat exchange tube (8) is installed on the inner wall of the integrated microfluidic layer (403). The heat exchange tube (8) is made of flexible stainless steel, with a diameter that matches the main channel of the microfluidic channel and a wall thickness of 0.1-0.2 mm. The connection between the heat exchange tube (8) and the integrated microfluidic layer (403) is sealed by vacuum brazing to ensure no coolant leakage.

7. The integrated flexible deployable radiator with integrated microchannels according to claim 6, characterized in that, The radiant plate (4) is provided with an integrated microfluidic layer (403), and a heat insulation cavity (9) is provided in the integrated microfluidic layer (403). The heat insulation cavity (9) is a closed cavity and is filled with an inert gas (11). The inert gas (11) is a low thermal conductivity inert gas, preferably one of xenon or argon, with a gas pressure of 0.01-0.03 MPa. The sealing plate 10 is made of flexible sealing material, and the sealing plate (10) and the end of the heat insulation cavity (9) are sealed by laser welding.

8. The integrated flexible deployable radiator with integrated microchannels according to claim 7, characterized in that, The radiating plate (4) can be folded and unfolded via the rotating shaft (3) and the connecting shaft (7), with an unfolding angle of 0-120°.

9. The integrated flexible deployable radiator with integrated microchannels according to claim 8, characterized in that, The radiant plate (4) is provided with a heat insulation layer (404), which is a thin film composite material. The heat insulation layer (404) is made of multi-layer vacuum-metallized polyester film and aerogel. The thickness of the heat insulation layer (404) is controlled within the range of 0.2-0.5mm.

10. An on-orbit deployment method for an integrated flexible deployable radiator with integrated microchannels, applied to the integrated flexible deployable radiator with integrated microchannels in claim 9, with the following specific operation steps; S1: Folding and securing before launch; Before the spacecraft is launched, multiple radiating plates (4) are folded in sequence through the connecting shaft (7) so that each radiating plate (4) is gathered around the rotating shaft (3) towards the radiator (1) body to form a compact folded state. After folding, the position limit and angle constraint of the radiator (4) are performed by the unfoldable rotating seat (2), so that the radiator (1) is in a safe and locked state for launch. S2: Orbit insertion status monitoring and deployment preparation; After the spacecraft enters the predetermined orbit and completes attitude stabilization, the control system detects the temperature, structural status and fluid loop sealing of the area where the radiator (1) is located; When it is confirmed that the radiator (1) meets the deployment conditions, the locking constraint on the deployable rotating seat (2) is released, so that the rotating shaft (3) is in a state of free rotation; S3: Coolant synchronous charging drive deployment; Start the thermal control system coolant circuit and inject coolant into the heat exchange tube (8) and the integrated microchannel layer (403); As the coolant continues to fill, a stable fluid pressure is formed inside the microchannel. This fluid pressure, together with the flexible restoring force of the radiating plate (4), drives the radiating plate (4) to gradually expand outward around the rotation axis (3), realizing "synchronous fluid filling - synchronous structural expansion". S4: Multi-level radiant panels deploy in tandem; While a single radiating plate (4) unfolds, adjacent radiating plates (4) rotate in tandem through a connecting shaft (7), causing multiple radiating plates (4) to unfold sequentially according to a preset unfolding order; During the unfolding process, the unfolding angle of the radiating plate (4) is guided and controlled by the unfoldable rotating seat (2), and the unfolding angle gradually increases to 0–120° within the preset range; S5: Deployment in place and stable posture; Once each radiating plate (4) reaches the set unfolding angle, the rotating seat (2) can be unfolded to limit the angle of the rotating shaft (3) to prevent the radiating plate (4) from over-rotating or rebounding. At this time, the radiating plate (4) forms a stable unfolding radiating surface structure, and the radiator (1) as a whole enters the stable unfolding state in orbit. S6: On-orbit cooling operation; The coolant flows along the heat-conducting groove (5) and the microchannel network in the integrated microchannel layer (403) and exchanges heat fully with the flexible composite substrate (402); The selective radiation coating (401) on the surface of the radiating plate (4) releases the absorbed heat into the outer space in the form of infrared radiation, thereby achieving continuous and efficient heat dissipation of the spacecraft. S7: Long-term on-orbit operation support; During the long-term on-orbit operation of the radiator (1), the heat insulation layer (404) and the heat insulation cavity (9) work together to reduce heat loss in the non-radiative direction; The inert gas (11) forms a stable low thermal conductivity environment in the insulation cavity (9), reducing the thermal shock caused by extreme temperature differences in space to the microfluidic structure and heat exchange tube (8), and ensuring that the radiator (1) operates stably and reliably under multiple thermal cycles.

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