Long-acting storage method for cold source of phase-change material superconducting tube in interlayer of cold fresh storage

Abstract

The invention relates to the technical field of heat energy storage, in particular to a cold fresh warehouse interlayer phase change material superconducting tube cold source long-acting storage method, which comprises the following steps: S1, constructing a finite volume constraint unit with a rigid boundary in a wall interlayer of a cold fresh warehouse, filling a modified water-based phase change material in the finite volume constraint unit, and implanting a fractal pulse tube network and a superconducting tube with a flexible choke section; s2, injecting an external liquid cold source into the fractal pulse tube network, and carrying out transient cooling on the phase change material through a graded flow channel; and S3, a high-pressure stress field is formed in the rigid boundary through the volume expansion effect generated by curing of the phase-change material, the flexible choke section is extruded to be elastically closed, and therefore working medium circulation of the superconducting pipe is physically blocked. According to the invention, physical closing of the cold source transmission channel is realized in the finite volume constraint unit with the rigid boundary, and the expansion effect is converted into turn-off driving force.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermal energy storage, in particular to a cold storage warehouse interlayer phase change material superconducting pipe cold source long-term storage method. BACKGROUND

[0002] As the core node of cold chain logistics, the stability of the internal temperature of the cold storage warehouse is directly related to the quality and safety of temperature-sensitive goods such as food and medicine. With the increasing demand for energy saving and emission reduction, the use of phase change materials for cold energy storage has become the mainstream trend in the industry. By storing cold energy in phase change materials during off-peak periods or using natural cold sources, and releasing it when needed, the load on the power grid can be effectively balanced and operating costs can be reduced. In order to improve the transmission efficiency of cold energy, superconducting pipes are often used to connect external cold sources, phase change energy storage units and cold storage internal environments due to their high thermal conductivity.

[0003] However, in existing cold storage warehouse phase change energy storage systems, the control mechanism of heat transfer and storage has significant limitations. Although superconducting pipes can efficiently conduct cold, they are usually passive heat conduction elements and lack internal switching functions. This means that once the phase change material is fully cooled or solidified, without additional control means, the superconducting pipe will continue to conduct heat from the cold storage interior to the phase change material, or heat will flow in the opposite direction when the external environment temperature fluctuates. This uncontrolled heat exchange can cause the stored cold energy to dissipate prematurely, making it impossible to achieve long-term, non-destructive storage of cold sources, and making it difficult to meet the emergency cooling needs of cold storage warehouses in long power outages or long-term peak shaving scenarios. SUMMARY

[0004] To overcome the above shortcomings, the present application provides a cold storage warehouse interlayer phase change material superconducting pipe cold source long-term storage method, which aims to improve the problem of uncontrollable thermal resistance of superconducting pipes.

[0005] In a first aspect, the present application provides a cold storage warehouse interlayer phase change material superconducting pipe cold source long-term storage method, S1: constructing a finite volume constraint unit with rigid boundaries in the wall interlayer of the cold storage warehouse, filling it with modified water-based phase change materials, and implanting a fractal vascular network and a superconducting pipe with a flexible choke section; S2: injecting an external liquid cold source into the fractal vascular network and using a hierarchical flow channel to instantaneously cool the phase change material; S3: using the volume expansion effect generated by the solidification of the phase change material to form a high-pressure stress field within the rigid boundary, which extrudes the flexible choke section to cause elastic closure, thereby physically blocking the working fluid circulation of the superconducting pipe; S4: stop injecting the cold source and use the continuous expansion stress of the solid phase change material to maintain the closed state of the flexible choke section, so that the superconducting pipe remains in the thermal resistance cutoff mode; S5: Real-time monitoring of the heat load demand and temperature change rate inside the cold storage by the control system; S6: When the cooling release demand is monitored, the control system adjusts the thermal conductivity of the superconducting pipe condensing section, induces the slight melting of the phase change material around the flexible choke section to release stress, and makes the flexible choke section elastically recover to be conductive, so as to realize the on-demand release of cold energy.

[0006] Preferably, the step of constructing the integrated constraint unit comprises: Arranging the main pipeline of the fractal vascular network close to the flexible choke section, and encapsulating both in the limited volume constraint unit region; Configuring the geometric volume of the limited volume constraint unit so that the volume increment generated by the solidification of the phase change material cannot be released through the deformation of the external boundary, but can only be converted into radial compression displacement directed to the flexible choke section.

[0007] Preferably, the operation of implanting the fractal vascular network comprises: Constructing a multi-stage branching network based on the generalized Murray's law; Configuring the diameter ratio of adjacent two-stage pipelines, which is associated with the branching stage number and fluid Murray's coefficient, to ensure that the wall shear stress in each stage pipeline is constant and minimize the fluid resistance during cold source perfusion.

[0008] Preferably, the step of perfusing the cold source network comprises: Injecting liquid nitrogen into the fractal vascular network in the form of pulses until the internal pressure in the limited volume constraint unit reaches the preset self-locking threshold, and the equivalent thermal resistance of the superconducting pipe jumps.

[0009] Preferably, the step of phase change expansion choke comprises: Establishing a stress conduction mechanism to ensure that the effective action pressure of the high-pressure stress field on the surface of the flexible choke section is greater than the pressure value required for the critical buckling instability of the flexible choke section; Wherein, the pressure value required for the critical buckling instability is determined based on the Young's modulus, Poisson's ratio and diameter-thickness ratio of the pipe wall of the flexible choke section.

[0010] Preferably, the step of variable resistance controlled cooling release comprises: Using the air gap thermal switch wrapped outside the superconducting pipe condensing section for control; The control system changes the gas molecular density in the air gap thermal switch interlayer by controlling the air pump, thereby linearly adjusting the convective heat transfer coefficient between the superconducting pipe condensing section and the environment in the library.

[0011] Preferably, the step of variable resistance controlled cooling release further comprises: The air pump is controlled by a pulse width modulation strategy to control the inflation and vacuum frequency; According to the difference between the target temperature and the current temperature, a duty cycle signal is calculated to dynamically adjust the opening degree of the flexible choke section and the heat conduction efficiency of the superconducting tube, so as to maintain the constant temperature of the library.

[0012] Preferably, in the step of constructing the integrated constraint unit: The filled phase change material is a modified water-based phase change liquid, which is configured to have a volume expansion rate greater than 5% during the phase change process; The flexible choke section is selected from a high elastic modulus and low temperature resistant metal thin-walled corrugated pipe or a high molecular composite heat conducting pipe.

[0013] Preferably, the step of variable resistance controlled release cooling further comprises a safety fuse logic: When the stress in the limited volume constraint unit is monitored to exceed the structural safety limit, the control system forcibly opens the heat dissipation channel of the superconducting tube, and rapidly melts part of the phase change material by using external heat to reduce the internal pressure.

[0014] In a second aspect, the present application provides the following technical solutions, a cold fresh library sandwich phase change material superconducting tube cold source long-acting storage system, a construction integrated module for executing the step of constructing the integrated constraint unit, including a limited volume constraint unit arranged in the wall of the cold fresh library, and a phase change material filled therein; A pulse vessel filling module for executing the step of cold source plexus perfusion, including a fractal pulse vessel network implanted in the phase change material, and an external cold source interface connected thereto; A phase change choke module for executing the step of phase change expansion choke, configured to utilize the volume expansion stress field generated by the solidification of the phase change material to extrude the flexible choke section of the superconducting tube inside the phase change material; A self-locking retention module for executing the step of adiabatic self-locking storage, configured to utilize the rigidity support of the solid phase change material to maintain the physical closed state of the flexible choke section; A heat-sensitive monitoring module for executing the step of heat load response monitoring, including temperature sensors distributed in the cold fresh library and connected to the input end of the control system; A controlled release cooling module for executing the step of variable resistance controlled release cooling, including an air gap thermal switch wrapped outside the condensation section of the superconducting tube and a gas pump controlled by the control system.

[0015] The present application has the following beneficial effects: 1. In this invention, the flexible choke section of the superconducting tube is directly squeezed by the volume expansion stress generated when the phase change material is cured within a finite volume constraint unit with rigid boundaries. This achieves the physical closure of the cold source transmission channel, converts the expansion effect into a shut-off driving force, blocks the heat flow without consuming external power, prevents the self-discharge of cold energy, and extends the storage time of the cold source.

[0016] 2. In this invention, by utilizing the material phase change induced by uniform cooling through a fractal vascular network as an endogenous driving force, the risk of failure caused by short circuits due to moisture or lubrication failure of electronic components is fundamentally eliminated, and the system achieves maintenance-free and long-life operation in concealed engineering.

[0017] 3. In this invention, by combining the superconducting condensation section extending into the storage tank with the air gap thermal switch, the convective heat transfer coefficient is changed by adjusting the air gap density through the control system. Stress relaxation is induced by a small amount of external heat exchange, thus solving the problem of the difficulty in controlling passive energy storage systems. Attached Figure Description

[0018] Figure 1 This is a flowchart of the long-term storage method of the superconducting cold source of phase change material in a cold storage interlayer proposed in this invention. Figure 2 This is a structural diagram of the long-term storage system of the cold storage interlayer phase change material superconducting cold source proposed in this invention. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0020] Example 1 In the first embodiment of the present invention, the present invention provides a method for long-term storage of cold storage materials using superconducting cold sources in a cold storage interlayer, such as... Figure 1 As shown, it includes the following steps: S1: Construct a finite volume confinement unit with rigid boundaries within the wall interlayer of a cold storage facility, fill it with modified water-based phase change material, and implant a fractal vascular network and a superconducting tube with a flexible choke section. The steps for constructing an integrated constraint element include: The main pipes of the fractal vascular network are arranged close to the flexible choke section, and both are encapsulated in a finite volume constrained unit region. The geometric volume of the finite volume constraint unit is configured so that the volume increment generated by the solidification of the phase change material cannot be released by the deformation of the external boundary, but only converted into radial compression displacement directed to the flexible choke section; The operation of implanting the fractal vascular network includes: The multi-stage branched network is constructed based on the generalized Murray's law; The diameter ratio of the adjacent two-stage pipes is configured to be associated with the branching stage number and the fluid Murray coefficient, so as to ensure the constant wall shear stress in each stage pipe and minimize the fluid resistance during the perfusion of the cold source; In the step of constructing the integrated constraint unit: The filled phase change material is a modified water-based phase change liquid, which is configured to have a volume expansion rate greater than 5% during the phase change process; The flexible choke section selects a high-elasticity modulus and low-temperature-resistant metal thin-walled corrugated pipe or a high-molecular composite heat pipe; Specifically, when constructing the integrated constraint unit in the cold fresh-keeping warehouse wall interlayer, first, a finite volume constraint unit with a rigid boundary is established. The finite volume constraint unit is made of high-stiffness materials, such as high-strength stainless steel or carbon fiber reinforced composite materials, and the structural stiffness is configured to be higher than the bulk modulus of the internal filling material. The geometric volume of the unit is set to a fixed value, and the rigid boundary is configured to have an elastic deformation rate in a negligible range when subjected to a predetermined range of internal phase change expansion pressure. This configuration of volume and stiffness ensures that the volume increment generated by the subsequent phase change material during the solidification process cannot be released by the outward deformation of the external boundary, but is forced to convert into a radial compression displacement vector directed to the core area inside the unit, thereby forming an effective closed driving force.

[0021] In the internal cavity of the finite volume constraint unit, a superconducting pipe and a fractal vascular network are implanted. The superconducting pipe penetrates through the finite volume constraint unit, and the pipe segment located inside the constraint unit is defined as a flexible choke section. The flexible choke section selects a high-elasticity modulus and low-temperature-resistant metal thin-walled corrugated pipe, such as beryllium copper alloy corrugated pipe or 304 stainless steel corrugated pipe. The thickness and pitch of the flexible choke section are calculated and configured so that the radial stiffness is lower than the stiffness of the external rigid boundary, so that the elastic buckling deformation occurs preferentially to the rigid boundary when subjected to the radial pressure of the surrounding medium.

[0022] The main pipeline of the fractal vascular network is configured to be arranged close to the outer wall surface of the flexible choke section, both of which are jointly encapsulated in the geometric center region of the limited volume constraint unit. This close arrangement establishes a preferential cooling path when the cold source is injected, so that the phase change of the phase change material around the flexible choke section is preferentially carried out, thereby rapidly establishing an isotropic closed stress ring around the choke section. The operation of implanting the fractal vascular network is not randomly arranged, but a multi-stage branching network is constructed based on the generalized Murray's law to ensure that the flow resistance of the fluid in each stage of the pipeline is minimized and the shear stress distribution is uniform. Specifically, the diameter ratio of two adjacent stages of pipelines is configured to satisfy the following relationship: ; wherein, represents the inner diameter of the parent pipeline of the th stage, represents the inner diameter of the child pipeline of the th stage, represents the branching stage, that is, the number of child pipelines branched from a parent pipeline, represents the fluid Murray coefficient, which is 3 for the flow characteristics of liquid nitrogen or cryogenic refrigerant used in this embodiment under laminar flow conditions. The pipe diameter ratio determined by the mathematical model ensures the hydrodynamic efficiency of the cold source working medium during the infusion process.

[0023] After the positioning and fixing of the above-mentioned components are completed, the modified water-based phase change material is vacuum infused into the limited volume constraint unit. The modified water-based phase change material is compounded from a pure water base, a nucleating agent and a thickening agent, and its thermophysical properties are adjusted to have a volume expansion rate greater than 5% during the phase change from liquid to solid. After filling, the limited volume constraint unit is sealed to form an independent physical entity that exchanges heat only through the superconducting pipe and inputs cold source only through the fractal vascular network interface, providing a basic structural support for subsequent cold source infusion and self-locking operation.

[0024] S2: injecting an external liquid cold source into the fractal vascular network to instantaneously cool the phase change material through the hierarchical flow channel; The steps of the cold source infusion include: Pulsed liquid nitrogen is injected into the fractal vascular network until the internal pressure in the limited volume constraint unit reaches the preset self-locking threshold and the equivalent thermal resistance of the superconducting pipe increases by a step. Specifically, in the cold source infusion step, the control system first establishes a physical connection between the external cold source injection device and the fractal vascular network. The external cold source is liquid nitrogen, which is connected to the inlet interface of the fractal vascular network through a delivery pipeline. An electromagnetic regulating valve driven by the output signal of the control system is configured on the pipeline.

[0025] The control system executes pulse injection control logic, sending discrete on and off signals with specific frequency and duty cycle to the electromagnetic regulating valve. Liquid nitrogen is injected into the fractal network of pipes in the form of pulsed fluid, and is distributed to the inside of the finite volume constraint unit through the hierarchical flow channel network constructed in the previous step, to transiently cool the modified water-based phase change material filled therein.

[0026] During the injection process, the control system starts a real-time monitoring program. This program reads real-time pressure data fed back by pressure sensors deployed inside the finite volume constraint unit through the data acquisition interface, and reads temperature sensor data at both ends of the superconducting pipe, the heat absorption section and the condensation section. The control system runs a thermal resistance calculation algorithm inside, and calculates the equivalent thermal resistance value of the superconducting pipe in real time according to the temperature difference at both ends of the superconducting pipe and the estimated heat flux density.

[0027] The control system memory has preset pressure self-locking threshold and thermal resistance step determination threshold. The monitoring program continuously executes logical judgment: comparing the real-time collected internal pressure data with the preset self-locking threshold, and differentiating the real-time calculated equivalent thermal resistance value from the reference value to identify step changes. When the control system detects that the internal pressure value in the finite volume constraint unit reaches or exceeds the preset self-locking threshold, and at the same time detects that the equivalent thermal resistance of the superconducting pipe has a step increase, the logical judgment unit outputs a termination instruction. The control system immediately sends a shutdown signal to the electromagnetic regulating valve, physically cuts off the liquid nitrogen injection channel, and stops the cold source infusion. The triggering of this logic state marks that the volume expansion stress of the phase change material has met the mechanical requirements of the closed flexible choke section, and the working fluid circulation of the superconducting pipe has been physically blocked.

[0028] S3: Use the volume expansion effect generated by the solidification of the phase change material to form a high-pressure stress field in the rigid boundary, and squeeze the flexible choke section to make it elastically close, thereby physically blocking the working fluid circulation of the superconducting pipe; The phase change expansion choke step includes: Establish a stress conduction mechanism to ensure that the effective action pressure of the high-pressure stress field generated on the surface of the flexible choke section is greater than the pressure value required for the critical buckling instability of the flexible choke section; The pressure value required for the critical buckling instability is determined based on the Young's modulus, Poisson's ratio and diameter-thickness ratio of the pipe wall of the flexible choke section; Specifically, in the phase change expansion choke step, as the cold source continues to be injected, the temperature of the modified water-based phase change material in the finite volume constraint unit decreases below the phase change point, and starts to transform from liquid to solid. Since the boundary of the finite volume constraint unit is constructed as a rigid boundary with constant geometric volume, the volume expansion generated by the solidification of the phase change material cannot be released through external volume expansion. This limited volume increment is converted into fluid static pressure and contact stress inside the rigid boundary, thereby forming a high-pressure stress field inside the unit.

[0029] The high-pressure stress field acts on the outer wall of the flexible choke section located at the center of the constraint unit in an isotropic manner. In the process, a stress conduction mechanism is established to focus the phase change expansion force on the flexible choke section through the constraint action of the rigid boundary. The system configuration ensures that the effective action pressure on the surface of the flexible choke section under the action of the high-pressure stress field is greater than the pressure value required for the critical buckling instability of the flexible choke section .

[0030] The pressure value required for the critical buckling instability is a structural mechanics parameter determined according to the physical properties of the flexible choke section, and its calculation follows the formula: ; Where: E represents the Young's modulus of the flexible choke section pipe wall material; ν represents the Poisson's ratio of the flexible choke section pipe wall material; t represents the thickness of the flexible choke section pipe wall; D represents the average diameter of the flexible choke section, and for a corrugated pipe structure, the average value of the crest and trough diameters is taken.

[0031] When the physical process satisfies the condition , the flexible choke section pipe wall elastically destabilizes and collapses under the action of radial pressure. This physical deformation eliminates the flow cross-section in the pipe and physically blocks the circulation path of the gas-liquid working medium inside the superconducting pipe, thereby cutting off the heat flow transmission through the superconducting pipe and making the system enter the thermal resistance cutoff state.

[0032] S4: Stop injecting the cold source and maintain the closed state of the flexible choke section using the sustained expansion stress of the solid phase change material to keep the superconducting pipe in the thermal resistance cutoff mode; Specifically, in the adiabatic self-locking storage step, when the control system confirms that a stable self-locking pressure field has been established inside the finite volume constraint unit based on monitoring data, it immediately executes the cold source cutoff program. The control system sends a cutoff signal to the electromagnetic valve connected in series at the entrance of the fractal vascular network, physically closes the input channel of the external liquid cold source, and sends a shutdown instruction to the external refrigeration equipment. At this time, the active refrigeration process of the system is terminated, and the control logic is switched from the active infusion state to the passive retention state.

[0033] ​In this state, the finite volume constraint unit inside the modified water-based phase change material that has been completely solidified as a passive actuation medium. Due to the geometric constraint characteristics of the rigid boundary, the volume expansion stress generated by the solidification of the phase change material cannot be released through boundary deformation, but is sealed inside the unit, forming a sustained static high pressure field. The static stress continuously applied to the outer wall of the flexible choke section ensures the effective action pressure Always maintained above the critical buckling instability pressure value This mechanical equilibrium mechanism based on the physical properties of the material forcibly maintains the physical closed form of the flexible choke section without consuming any external power or mechanical energy, preventing it from reopening due to material elastic recovery.

[0034] With the closure of the flexible choke section, the gas-liquid working fluid circulation path inside the superconducting pipe is physically blocked, causing it to switch from a high thermal conductivity state to a locked thermal resistance cutoff mode. At this time, the control system enters a low-power static monitoring mode, suspending control output to the air gap thermal switch and other active actuators. The control system only retains the periodic data sampling function for internal pressure and superconducting pipe temperature difference to verify whether the system is continuously in a storage state thermally isolated from the external environment, achieving zero-energy long-term storage of the cold source.

[0035] S5: Real-time monitoring of the thermal load demand and temperature change rate inside the cold fresh-keeping library by the control system; Specifically, in the thermal load response monitoring step, the control system starts the environment perception subprogram and establishes a communication connection with the temperature sensor array deployed at different spatial positions inside the cold fresh-keeping library through the data bus. The control system periodically collects real-time temperature data of each measurement point in the library according to the preset sampling frequency, and converts the collected analog electrical signals into digital temperature sequences . In order to eliminate the influence of environmental noise and the measurement fluctuations of the sensor itself on the control accuracy, the control system performs digital filtering processing on the original data sequence, such as using a sliding average filtering algorithm or a Kalman filtering algorithm, to obtain smooth real-time temperature values with high signal-to-noise ratio.

[0036] Based on the processed temperature data, the operation unit inside the control system calculates the thermal load state parameters inside the cold fresh-keeping library in real time. First, the system calculates the temperature change rate at the current time, which is achieved by performing a difference operation on the temperature data of consecutive time steps. The resulting value represents the dynamic evolution trend of the temperature field inside the library and the rate of external heat intrusion over time. At the same time, the control system reads the user-predefined target constant temperature value from the memory and calculates the deviation value between the current measured average temperature and the target temperature . The deviation value The system quantitatively defines the static thermal load demand at the current time. The control system writes the calculated temperature change rate and temperature deviation value into the system state register in real time as the input variable of the PID control algorithm or fuzzy control logic in the subsequent variable resistance controlled release cooling step, thereby realizing digital real-time monitoring of the thermodynamic state of the cold fresh warehouse.

[0037] S6: When the release cooling demand is monitored, the control system adjusts the thermal conductivity of the superconducting pipe condensing section, induces the slight melting of the phase change material around the flexible choke section to release stress, and makes the flexible choke section elastically recover to be conductive, realizing on-demand release of cold.

[0038] The variable resistance controlled release cooling step includes: Using the air gap thermal switch wrapped outside the superconducting pipe condensing section for regulation and control; The control system changes the gas molecular density in the air gap thermal switch interlayer by controlling the air pump, thereby linearly adjusting the convective heat transfer coefficient between the superconducting pipe condensing section and the environment in the warehouse; The variable resistance controlled release cooling step further includes: Using a pulse width modulation strategy to control the inflation and vacuum frequency of the air pump; According to the difference between the target temperature and the current temperature, the duty cycle signal is calculated to dynamically adjust the opening degree of the flexible choke section and the thermal conductivity of the superconducting pipe, thereby maintaining the constant temperature of the warehouse; The variable resistance controlled release cooling step further includes a safety fuse logic: When the stress in the limited volume constraint unit is monitored to exceed the structural safety limit, the control system forcibly opens the heat dissipation channel of the superconducting pipe, and uses external heat to quickly melt part of the phase change material to reduce the internal pressure; Specifically, in the variable resistance controlled release cooling step, the control system performs closed-loop thermodynamic adjustment according to the logical judgment result. When the state register indicates that there is a release cooling demand, the control system activates the air gap thermal switch adjustment subprogram, adjusts the physical parameters of the air gap thermal switch wrapped outside the superconducting pipe condensing section, and controls the thermal conductivity of the superconducting pipe.

[0039] The control system sends a driving signal to the air pump connected to the air gap thermal switch through a digital output interface DO. In order to realize continuous linear adjustment of the thermal conductivity, the control system adopts a pulse width modulation PWM strategy. The central processing unit uses a proportional-integral-derivative PID control algorithm to control the target duty cycle of the current control period according to the currently collected temperature deviation and temperature change rate . The calculation of the duty cycle follows the following transfer function logic: ; Where, , , These are the preset proportional, derivative, and integral gain coefficients, respectively.

[0040] The control system converts the calculated digital duty cycle signal into a voltage pulse sequence and applies it to the gas pump drive circuit. The gas pump performs either inflation or vacuuming operations based on the received PWM signal frequency and pulse width, thereby altering the gas molecule density within the gas gap thermal switch interlayer. This change in gas density directly and physically modulates the convective heat transfer coefficient between the superconducting condenser section and the external storage environment.

[0041] As the calculated duty cycle increases, the gas density within the air gap increases, and the thermal resistance decreases, allowing a small amount of external heat to be conducted in the reverse direction to the flexible choke region located inside the finite volume confinement unit. This heat input induces a small phase change melting (volume shrinkage) in the solid phase change material surrounding the flexible choke, resulting in radial compressive stress acting on the outer wall of the flexible choke. Decrease. When Reduced below critical buckling pressure At this time, the flexible choke section uses its own elastic modulus to restore its geometry, reopening the working fluid circulation channel inside the superconducting pipe, thereby releasing cold energy into the cold storage. The control system continuously adjusts the duty cycle. The opening of the flexible choke section is dynamically balanced to match the rate of cold energy release with the current heat load demand, thus maintaining a constant storage temperature.

[0042] In addition, the control system runs a safety fuse logic subroutine in parallel, possessing the highest priority control authority. This program scans the values ​​of the pressure sensors inside the finite volume constraint unit in real time. If the internal stress exceeds the preset structural safety limit, the control system immediately interrupts the current temperature control process and forcibly outputs a full-speed drive signal with a 100% duty cycle to the air gap thermal switch. This operation minimizes the thermal resistance of the air gap thermal switch, maximizes the introduction of external heat to rapidly melt the phase change material, and quickly reduces the internal pressure through phase change contraction, preventing structural failure of the rigid boundary.

[0043] Example 2: Because the heat exchange channels between phase change materials and the external environment are typically fixed thermal resistance structures, lacking a mechanism for actively shutting off or adjusting heat flow, the cold source, after filling, will experience uncontrollable and continuous cold dissipation due to natural temperature differences even during non-cooling periods. This results in high cold source discharge rates, the inability to achieve long-term, non-destructive, and closed-loop storage of cold energy, and the inability to dynamically adjust the cold release intensity according to the real-time heat load requirements within the storage facility. To address these issues, this invention provides a long-term storage system for a cold storage facility with a phase change material superconducting cold source, the structure of which is as follows: Figure 2 As shown. The specific implementation process of this system is as follows: The integrated module is configured to perform the step of building the integrated constraint unit, which includes a limited volume constraint unit arranged in the wall of the cold storage room, and a phase change material filled therein; The vessel filling module is configured to perform the step of cold source vessel perfusion, which includes a fractal vessel network implanted in the phase change material, and an external cold source interface connected thereto; The phase change choke module is configured to perform the step of phase change expansion choke, which is configured to use the volume expansion stress field generated by the solidification of the phase change material to squeeze the superconducting tube flexible choke section located inside the phase change material; The self-locking holding module is configured to perform the step of adiabatic self-locking storage, which is configured to use the rigidity support of the solid phase change material to maintain the physical closed state of the flexible choke section; The heat-sensitive monitoring module is configured to perform the step of heat load response monitoring, which includes temperature sensors distributed in the cold storage room and connected to the input end of the control system; The controlled release cooling module is configured to perform the step of variable resistance controlled release cooling, which includes an air gap thermal switch wrapped around the outside of the superconducting tube condenser section and an air pump controlled by the control system.

[0044] Specifically, the integrated module is configured to perform the operation of building the integrated constraint unit. The module includes a limited volume constraint unit arranged in the wall interlayer of the cold storage room. The limited volume constraint unit is made of high rigidity material, and its geometric volume is fixed. The rigidity of the unit is configured to be higher than the bulk modulus of the internal filling material, so that the boundary deformation caused by the internal pressure change approaches zero. The limited volume constraint unit is filled with a modified water-based phase change material, which is configured to have a volume expansion rate of more than 5% during the conversion from liquid to solid.

[0045] The integrated module also includes a superconducting tube and a fractal vessel network implanted in the phase change material. The superconducting tube penetrates the limited volume constraint unit, wherein the tube section located inside the constraint unit is defined as a flexible choke section. The flexible choke section selects a metal thin-walled bellows with a certain elastic modulus or a polymer composite heat-conducting tube. The main pipeline of the fractal vessel network is arranged close to the outer wall surface of the flexible choke section, and both are encapsulated in the geometric center region of the limited volume constraint unit. The structure of the fractal vessel network is constructed based on the generalized Murray's law, and the diameter ratio of adjacent two levels of pipelines satisfies the following relationship: ; In the formula, Dp(n) represents the inner diameter of the parent pipeline of the n th level, Dc(n) represents the inner diameter of the child pipeline of the n th level, N represents the bifurcation level, represents the fluid's murray coefficient. The structural parameter configuration aims to ensure the constant wall shear stress in each level of the pipeline, and minimize the fluid resistance during the cold source perfusion.

[0046] The vessel perfusion module is configured to perform the operation of cold source choroid perfusion. The module includes a fluid interface of the fractal vessel network extending outside the finite volume confinement unit, and an external cold source supply device connected to the interface. The external cold source supply device is in communication with the fractal vessel network through an electromagnetic regulating valve. The control system is connected to the electromagnetic regulating valve and is configured to output a pulse control signal to inject the liquid cold source into the fractal vessel network in the form of pulses.

[0047] The vessel perfusion module further includes a pressure sensor deployed within the finite volume confinement unit and a temperature sensor deployed at both ends of the superconducting tube. The control system reads the pressure value of the pressure sensor in real time and calculates the equivalent thermal resistance of the superconducting tube based on the temperature sensor data When the internal pressure reaches a preset self-locking threshold , and the equivalent thermal resistance of the superconducting tube occurs a step increase, the vessel perfusion module stops the cold source injection by closing the electromagnetic regulating valve.

[0048] The phase change choke module is configured to perform the operation of phase change expansion choke. The module utilizes the rigid boundary characteristics of the finite volume confinement unit to convert the volume increment generated by the modified water-based phase change material during the solidification process into a radial compression displacement directed to the flexible choke section. This physical process establishes an isotropic high-pressure stress field within the finite volume confinement unit. The structural parameters of the phase change choke module are configured to ensure that the effective action pressure of the high-pressure stress field on the surface of the flexible choke section is greater than the pressure value required for the critical buckling instability of the flexible choke section.

[0049] The critical buckling instability pressure value is determined based on the geometric dimensions and material mechanical properties of the flexible choke section, and its calculation formula is: ; In the formula, represents the Young's modulus of the flexible choke section pipe wall material, represents the Poisson's ratio of the flexible choke section pipe wall material, represents the pipe wall thickness of the flexible choke section, represents the average diameter of the flexible choke section. When , the flexible choke section occurs elastic closure, physically cutting off the gas-liquid working medium flow path inside the superconducting tube.

[0050] The self-locking holding module is configured to perform the operation of adiabatic self-locking storage. The module is not an independent hardware entity, but a logical definition of the system in a specific physical state. After stopping the cold source injection, the self-locking holding module maintains the physical closed state of the flexible choke section by using the rigid support effect of the completely solidified phase change material. Since the rigid boundary limits the volume rebound of the phase change material, the radial pressure on the flexible choke section is continuously maintained above, so that the superconducting tube maintains the thermal resistance cutoff mode, realizing the zero-energy consumption sealing of the cold source.

[0051] The heat-sensitive monitoring module is configured to perform the operation of heat load response monitoring. The module includes an array of temperature sensors distributed in the internal space of the cold fresh-keeping library and a data acquisition unit of the control system. The control system periodically acquires the temperature data in the library and performs digital filtering processing. The heat-sensitive monitoring module calculates the temperature deviation and the temperature change rate at the current time.

[0052] The temperature deviation is defined as the difference between the current temperature and the preset target temperature : The temperature change rate is defined as the first-order derivative of temperature with respect to time: These two parameters are used as control input variables for the subsequent controlled release cooling module.

[0053] The controlled release cooling module is configured to perform the operation of variable resistance controlled release cooling. The module includes a gas gap thermal switch wrapped outside the condensing section of the superconducting tube, a gas pump connected to the gas gap thermal switch through a pipeline, and a corresponding driving circuit. The gas gap thermal switch is a cavity structure with a double-layer wall, and the interlayer space is in communication with the gas pump. The control system controls the inflation and vacuum frequency of the gas pump using the pulse width modulation (PWM) strategy based on the and output by the heat-sensitive monitoring module.

[0054] The control system changes the gas molecular density in the interlayer of the gas gap thermal switch by adjusting the operation of the gas pump, thereby linearly adjusting the convective heat transfer coefficient between the condensing section of the superconducting tube and the environment in the library. The duty cycle of the gas pump driving signal is calculated based on proportional-differential calculation, and the calculation formula is as follows: ; wherein , , Kp, Kd, Ki are proportional, derivative and integral gain coefficients respectively. When the duty cycle increases, leading to the increase of gas density, the external minute heat is transferred to the superconducting tube through the air gap thermal switch, and is conducted to the periphery of the flexible choke section in the opposite direction. The heat induces the phase change material at the periphery of the flexible choke section to melt slightly, causing the radial pressure acting on the flexible choke section to decrease. When the pressure drops below , the flexible choke section elastically recovers to be conductive, and the superconducting tube recovers the working medium circulation and releases cold energy.

[0055] The controlled cold release module further comprises a safety fuse logic unit. The unit monitors the stress sensor data in the finite volume constraint unit in real time. When the monitored internal stress exceeds the preset structural safety limit, the control system forcibly outputs a full duty cycle signal to the air pump, maximizes the heat conduction efficiency of the air gap thermal switch, rapidly melts part of the phase change material using external heat to reduce the internal pressure, and prevents the rigid boundary from being broken.

[0056] Finally, it should be noted that: the above only for the preferred embodiments of the present application, and not for limiting the present application, although the foregoing embodiments of the present application are described in detail, for those skilled in the art, it still can be modified, or part of the technical features of the equivalent replacement, within the spirit and principles of the present application, any modification, equivalent replacement, improvement, etc., should be included in the scope of the present application.

Claims

1. A long-term storage method of cold fresh-keeping interlayer phase change material superconducting pipe cold source, characterized in that, Comprise: S1: build a finite volume constraint unit with rigid boundary in the cold fresh store wall interlayer, fill it with modified water-based phase change material, and implant fractal vascular network and superconducting tube with flexible choke section; S2: inject external liquid cold source into the fractal vascular network, and perform transient cooling on the phase change material through hierarchical flow channels; S3: use the volume expansion effect generated by the solidification of the phase change material to form a high-pressure stress field in the rigid boundary, extrude the flexible choke section to make it elastically close, thereby physically blocking the working fluid circulation of the superconducting tube; S4: stop injecting cold source, and use the continuous expansion stress of the solid phase change material to maintain the closed state of the flexible choke section, so that the superconducting tube remains in thermal resistance cutoff mode; S5: real-time monitor the heat load demand and temperature change rate inside the cold fresh store through the control system; S6: when the cold release demand is monitored, the control system adjusts the thermal conductivity of the condensing section of the superconducting tube, induces the slight melting of the phase change material around the flexible choke section to release stress, makes the flexible choke section elastically recover to open, and realizes the on-demand release of cold.

2. The long-term storage method of cold fresh-keeping layer phase change material superconducting pipe cold source according to claim 1, characterized in that, The step of building an integrated constraint unit comprises: Arrange the main pipeline of the fractal vascular network close to the flexible choke section, and encapsulate both in the finite volume constraint unit area; Configure the geometric volume of the finite volume constraint unit, so that the volume increment generated by the solidification of the phase change material cannot be released through the external boundary deformation, but can only be converted into radial compression displacement directed to the flexible choke section.

3. The long-term storage method of cold fresh-keeping layer phase change material superconducting pipe cold source according to claim 1, characterized in that, The operation of implanting the fractal vascular network comprises: Build a multi-stage branching network based on the generalized Murray's law; Configure the diameter ratio of adjacent two-stage pipelines, which is associated with the branching stage number and fluid Murray's coefficient, to ensure that the wall shear stress in each stage pipeline is constant and minimize the fluid resistance during cold source infusion.

4. The long-term storage method of cold fresh-keeping interlayer phase change material superconducting pipe cold source according to claim 1, characterized in that, The step of cold source network infusion comprises: Inject liquid nitrogen into the fractal vascular network in pulse form until the internal pressure in the finite volume constraint unit reaches the preset self-locking threshold, and the equivalent thermal resistance of the superconducting tube increases by a step.

5. The long-term storage method of cold fresh-keeping interlayer phase change material superconducting pipe cold source according to claim 1, characterized in that, The step of phase change expansion choke comprises: Establish a stress conduction mechanism to ensure that the effective action pressure of the high-pressure stress field on the surface of the flexible choke section is greater than the pressure value required for the critical buckling instability of the flexible choke section; Wherein, the pressure value required for the critical buckling instability is determined based on the Young's modulus, Poisson's ratio and diameter-thickness ratio of the pipe wall of the flexible choke section.

6. The long-term storage method of cold fresh-keeping interlayer phase change material superconducting pipe cold source according to claim 1, characterized in that, The step of variable resistance controlled cold release comprises: Use the air gap thermal switch wrapped outside the condensing section of the superconducting tube for control; The control system changes the gas molecular density in the air gap thermal switch interlayer by controlling the air pump, thereby linearly adjusting the convective heat transfer coefficient between the condensing section of the superconducting tube and the environment inside the store.

7. The long-term storage method of cold storage sandwich phase change material superconducting pipe cold source according to claim 1, characterized in that, The step of variable resistance controlled cold release further comprises: Use pulse width modulation strategy to control the inflation and vacuum frequency of the air pump; According to the difference between the target temperature and the current temperature, calculate the duty cycle signal to dynamically adjust the opening degree of the flexible choke section and the thermal conductivity of the superconducting tube, and maintain constant store temperature.

8. The long-term storage method of cold store sandwich phase change material superconducting pipe cold source according to claim 1, characterized in that, In the step of building an integrated constraint unit: The filled phase change material is a modified water-based phase change liquid configured to have a volume expansion rate greater than 5% during phase change; The flexible choke section is selected from a high elastic modulus and low temperature resistant metal thin-walled corrugated pipe or a high molecular composite heat conducting pipe.

9. The long-term storage method of cold storage sandwich phase change material superconducting pipe cold source according to claim 1, characterized in that, The step of variable resistance controlled release cooling further comprises a safety fuse logic: When the stress in the limited volume constraint unit is monitored to exceed the structural safety limit, the control system forces the heat dissipation channel of the superconducting pipe to be opened, and part of the phase change material is quickly melted by external heat to reduce the internal pressure.

10. The long-term storage system of cold fresh-keeping interlayer phase change material superconducting pipe cold source, characterized in that, The long-term storage method for the cold fresh store sandwich phase change material superconducting pipe cold source of any one of claims 1-9, the system comprises: The construction integrated module is configured to perform the step of constructing the integrated constraint unit, including a limited volume constraint unit arranged in the wall of the cold fresh store, and a phase change material filled therein; The vessel filling module is configured to perform the step of cold source plexus perfusion, including a fractal vessel network implanted in the phase change material and an external cold source interface connected thereto; The phase change choke module is configured to perform the step of phase change expansion choke, configured to utilize the volume expansion stress field generated by the solidification of the phase change material to squeeze the flexible choke section of the superconducting pipe inside the phase change material; The self-locking retention module is configured to perform the step of adiabatic self-locking storage, configured to utilize the rigidity support of the solid phase change material to maintain the physical closed state of the flexible choke section; The heat sensitive monitoring module is configured to perform the step of heat load response monitoring, including temperature sensors distributed in the cold fresh store and a control system input connected thereto; The controlled release cooling module is configured to perform the step of variable resistance controlled release cooling, including an air gap thermal switch wrapped outside the superconducting pipe condensing section and an air pump controlled by the control system.

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