Phase change heat storage and exchange system and regulation and control method thereof

Abstract

The invention provides a phase change heat storage and exchange system and a regulation and control method thereof.The phase change heat storage and exchange system comprises a heat exchange fluid loop, a phase change heat storage unit, a regulation and control unit and an intelligent regulation and control module, the phase change heat storage unit comprises a box body, the box body is provided with a containing cavity, the containing cavity is filled with a phase change material, and an inner pipe is located in the containing cavity; the inner pipe extends in the containing cavity in a zigzag mode, the containing cavity is provided with a plurality of fins, and the fins are connected with the outer wall of the inner pipe. The regulation and control unit comprises a flexible graphite cushion layer, the flexible graphite cushion layer is arranged between the phase change material and the outer wall of the inner pipe, and the flexible graphite cushion layer is used for self-adaptively compensating a heat transfer gap generated by the solid-liquid phase change volume change of the phase change material. The intelligent regulation and control module is connected with the regulation and control unit, the circulating pump, the flow sensor and the first temperature sensor. The flexible graphite cushion layer can fill a heat transfer gap generated by the solid-liquid phase change volume change of the phase change material, so that the heat conductivity in the heat storage process is improved.

Description

Technical Field

[0001] This application belongs to the field of thermal energy storage and conversion technology, and in particular relates to a phase change thermal energy storage and heat exchange system and its control method. Background Technology

[0002] With the accelerated transformation of the global energy structure, the large-scale application of renewable energy (such as solar and wind power) and the efficient recovery and utilization of industrial waste heat resources have become key paths to solve energy shortages and environmental pollution problems. However, renewable energy is intermittent and fluctuates, while industrial waste heat faces the challenges of large temperature fluctuations and mismatch between supply and demand in time and space. This necessitates reliable thermal storage and heat exchange technologies as the core of energy buffering and regulation to achieve peak shaving and valley filling and efficient energy transfer. As a key device connecting energy production and consumption, the core performance of thermal storage and heat exchange systems directly determines energy utilization efficiency and system operational stability. Currently, in related technologies, the heat transfer gaps created by the solid-liquid phase change volume change of phase change materials in thermal storage systems lead to poor thermal conductivity during the storage process. Summary of the Invention

[0003] The technical problem to be solved by this application is to provide a phase change thermal storage heat exchange system, which aims to solve the problem of poor thermal conductivity during thermal storage caused by the heat transfer gap generated by the solid-liquid phase change volume change of phase change materials.

[0004] To address the aforementioned technical problems, in a first aspect, this application proposes a phase change thermal energy storage and heat exchange system, comprising: A heat exchange fluid circuit includes a heat exchange tube, a circulating pump, a flow sensor, and a first temperature sensor. The heat exchange tube includes an inner tube and an outer tube connected together. The circulating pump, the flow sensor, and the first temperature sensor are disposed on the outer tube. A phase change thermal energy storage unit includes a housing with a receiving cavity filled with a phase change material, an inner tube located in the receiving cavity and extending in a tortuous manner within the receiving cavity, and the receiving cavity having multiple fins connected to the outer wall of the inner tube. The control unit includes a flexible graphite pad, which is disposed between the phase change material and the outer wall of the inner tube. The flexible graphite pad is used to adaptively compensate for the heat transfer gap caused by the volume change of the phase change material due to the solid-liquid phase change. The intelligent control module includes an air gap thermal resistance calculation unit, and the intelligent control module is connected to the control unit, the circulating pump, the flow sensor and the first temperature sensor.

[0005] Furthermore, the intelligent control module is used to acquire the liquid phase fraction, temperature field distribution and flow parameters of the phase change material, and to control the flow sensor and the inlet temperature of the inner tube according to the liquid phase fraction, the temperature field distribution and the flow parameters.

[0006] Furthermore, the air gap thermal resistance calculation unit is used to correct the sudden change in contact thermal resistance caused by the liquefaction flow and volume shrinkage of the phase change material.

[0007] Furthermore, the intelligent control module includes multiple second temperature sensors, which are distributed within the accommodating cavity.

[0008] Furthermore, the phase change material is a paraffin-kaolin-stearic acid ternary composite phase change material, the mass ratio of the paraffin-kaolin-stearic acid ternary composite phase change material is paraffin:stearic acid:kaolin = (17-19):(8-9):(4-5), the phase change temperature of the paraffin-kaolin-stearic acid ternary composite phase change material is 52.5°C-58°C, and the latent heat value is ≥175J / g.

[0009] Furthermore, the preparation method of the paraffin-kaolin-stearic acid ternary composite phase change material is as follows: paraffin and stearic acid are melt-blended in a constant temperature water bath at 85°C-90°C according to the mass ratio, and then kaolin nanoparticles are added in three portions, with an interval of 15 minutes between each addition; During the preparation process, dispersion is achieved using ultrasound, with an ultrasound power of 240W-360W.

[0010] Furthermore, the control unit includes a graphite pad micro-compression device, which is connected to the flexible graphite pad and is also connected to the intelligent control module.

[0011] Furthermore, the inner surface of the heat exchange tube is provided with serrated ribs, the helix angle of the serrated ribs is 45°-60°, and the ratio of the rib height H of the serrated ribs to the inner diameter R of the heat exchange tube is 0.08-0.12.

[0012] Furthermore, the axial angle between the fins and the inner tube is 30°-90°, and the ratio of the spacing L1 between adjacent fins to the thickness L2 of the phase change material is 0.15-0.25.

[0013] Furthermore, the fin has a fractal tree-like structure, and the fin includes a connected trunk and multiple branches, with the ratio of the branch length L3 to the fin length L being 0.3-0.7.

[0014] Furthermore, the fin surface is coated with a black nickel coating with a thickness of 50μm-80μm, and the emissivity of the black nickel coating is >0.92.

[0015] Secondly, this application provides a control method applied to a phase change thermal energy storage and heat exchange system as described in any of the above embodiments, the control method comprising: The heat storage stage of the phase change thermal energy storage and heat exchange system: When the liquid phase fraction of the phase change material is detected to be <30%, the inlet temperature of the inner tube is controlled to be 15°C-20°C higher than the phase change point, and the flow velocity of the heat exchange tube is 0.3m / s-0.5m / s; When the liquid phase fraction is detected to be >70%, the inlet temperature of the inner tube is controlled to be 25°C-30°C, and the flow rate of the heat exchange tube is 0.6m / s-0.8m / s; During the heat release phase of the phase change thermal storage and heat exchange system: The initial flow velocity of the heat exchange tube is set to 0.4 m / s. For every 10% decrease in the liquid phase fraction, the flow velocity of the heat exchange tube increases by 0.1 m / s until it reaches 0.8 m / s, in order to maintain a stable heat release power. When the air gap thermal resistance of the phase change thermal storage heat exchange system exceeds the preset threshold of 0.05 m²·K / W, the graphite pad micro-compression device is activated to dynamically compress and compensate the heat transfer gap.

[0016] Furthermore, the mathematical model for calculating the air gap thermal resistance is as follows: , Among them, R gap For air gap thermal resistance, δ gap For real-time air gap thickness, K eff η is the effective thermal conductivity of the phase change material. liquid Let be the liquid phase fraction, and α be the gravity influence coefficient, with a value of 0.3-0.5.

[0017] The phase change thermal energy storage system in this application includes a heat exchange fluid loop, a phase change thermal energy storage unit, a control unit, and an intelligent control module. The heat exchange fluid loop includes a heat exchange tube, a circulation pump, a flow sensor, and a first temperature sensor. The heat exchange tube includes an inner tube and an outer tube connected together. The circulation pump, flow sensor, and first temperature sensor are located on the outer tube. The phase change thermal energy storage unit includes a housing with a receiving cavity filled with phase change material. An inner tube is located in the receiving cavity and extends in a tortuous manner within the receiving cavity. The receiving cavity has multiple fins connected to the outer wall of the inner tube. The control unit includes a flexible graphite pad layer disposed between the phase change material and the outer wall of the inner tube. The flexible graphite pad layer is used to adaptively compensate for the heat transfer gap caused by the solid-liquid phase change volume change of the phase change material. The intelligent control module includes an air gap thermal resistance calculation unit disposed in the receiving cavity and is connected to the control unit, the circulation pump, the flow sensor, and the first temperature sensor. Flexible graphite pads can fill the heat transfer gaps caused by the volume change of phase change materials due to solid-liquid phase change, thereby improving the thermal conductivity during the heat storage process. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the phase change thermal energy storage and heat exchange system in the embodiments of this application; Figure 2 This is a cross-sectional view of the heat exchange tube in an embodiment of this application; Figure 3 This is a flowchart of the control method in the embodiments of this application.

[0019] In the attached figures, the reference numerals represent: 1. Heat exchange fluid loop; 11. Heat exchange tube; 111. Inner tube; 112. Outer tube; 113. Serrated rib; 12. Circulation pump; 13. Flow sensor; 14. First temperature sensor; 2. Phase change thermal storage unit; 21. Box; 211. Receiving cavity; 22. Fin; 3. Control unit; 31. Flexible graphite pad; 32. Graphite pad micro-compression device; 4. Intelligent control module; 42. Second temperature sensor. Detailed Implementation

[0020] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0021] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "circumferential", "radial", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0023] As a key device connecting energy production and consumption, the core performance of thermal storage and heat exchange systems directly determines energy utilization efficiency and system operational stability. Currently, in related technologies, the heat transfer gaps created by the solid-liquid phase change volume change of phase change materials in thermal storage systems lead to poor thermal conductivity during the storage process.

[0024] This application proposes a thermal storage and heat exchange system to solve the problems in the aforementioned related technologies.

[0025] As attached Figure 1 The figure shown is a schematic diagram of the overall structure of the phase change thermal energy storage and heat exchange system in an embodiment of this application. As can be seen from the figure, the phase change thermal energy storage and heat exchange system includes a heat exchange fluid loop 1, a phase change thermal energy storage unit 2, a control unit 3, and an intelligent control module 4.

[0026] The heat exchange fluid loop 1 includes a heat exchange tube 11, a circulation pump 12, a flow sensor 13, and a first temperature sensor 14. The heat exchange medium flows within the heat exchange tube 11 to achieve heat exchange. The circulation pump 12 provides the driving force to propel the flow of the heat exchange medium within the heat exchange tube 11. The flow sensor 13 controls the flow rate of the heat exchange medium within the heat exchange tube 11. The first temperature sensor 14 monitors the temperature of the heat exchange medium within the heat exchange tube 11. The heat exchange tube 11 includes an inner tube 111 and an outer tube 112 connected together. The inner tube 111 and the outer tube 112 can be integrally formed or detachably connected. The circulation pump 12, the flow sensor 13, and the first temperature sensor 14 are disposed on the outer tube 112 to control the flow rate and temperature of the heat exchange medium within the outer tube 112. Understandably, the flow sensor 13 and the first temperature sensor 14 are disposed on the outer tube 112 and located at the inlet of the inner tube 111 to monitor the flow rate and temperature of the heat exchange medium at the inlet of the inner tube 111.

[0027] The phase change thermal storage unit 2 includes a housing 21, which has a receiving cavity 211 filled with a phase change material (PCM). PCM is a material that can absorb or release a large amount of heat when it undergoes a phase change; that is, PCM is used for both heat absorption and release. When a PCM absorbs heat, it can change from a solid to a liquid state, thereby storing heat. When a PCM releases heat, it can change from a liquid to a solid state, thereby releasing heat.

[0028] The inner tube 111 is located in the receiving cavity 211, and extends in a tortuous manner within the receiving cavity 211. The inner tube 111 moves back and forth within the receiving cavity 211, thereby allowing the receiving cavity 211 to accommodate a longer heat exchange tube 11, resulting in a larger surface area for the heat exchange tube 11 within the receiving cavity 211, which improves heat exchange efficiency. It is understood that the outer tube 112 refers to the heat exchange tube 11 located outside the housing 21, and the inner tube 111 refers to the heat exchange tube 11 located inside the housing 21. The heat exchange medium within the outer tube 112 does not require heat exchange; exemplarily, the outer wall of the outer tube 112 is provided with an insulation layer to prevent heat loss from the heat exchange medium onto the outer tube 112. The receiving cavity 211 is provided with multiple fins 22, which are connected to the outer wall of the inner tube 111. The fins 22 can conduct heat from the inner tube 111 to the phase change material, and vice versa. Fin 22 has good thermal conductivity, which can improve the heat storage and heat release efficiency of phase change materials.

[0029] The control unit 3 includes a flexible graphite pad 31, which is disposed between the phase change material and the outer wall of the inner tube 111. The flexible graphite pad 31 is used to adaptively compensate for the heat transfer gap caused by the solid-liquid phase change volume change of the phase change material. For example, the thickness of the flexible graphite pad 31 is 0.5mm-2mm. When the phase change material stores heat, it changes from a solid to a liquid state. The volume change of the phase change material creates a heat transfer gap. At this time, the volume of the flexible graphite pad 31 increases, filling the heat transfer gap. Furthermore, graphite has good thermal conductivity, which can improve thermal conductivity. When the phase change material releases heat, it changes from a liquid to a solid state. The volume change of the phase change material reduces the heat transfer gap. At this time, the volume of the flexible graphite pad 31 decreases, thereby preventing the housing 21 from cracking due to the increased volume of the phase change material.

[0030] The intelligent control module 4 includes an air gap thermal resistance calculation unit, and is connected to the control unit 3, the circulating pump 12, the flow sensor 13, and the first temperature sensor 14. The intelligent control module 4 is used to control the operating parameters of the phase change thermal storage unit 2 to ensure its normal operation.

[0031] As can be seen from the above embodiments, the phase change thermal storage heat exchange system of this application includes a control unit 3. The flexible graphite pad 31 of the control unit 3 can fill the heat transfer gap caused by the volume change of the phase change material due to the solid-liquid phase change, thereby improving the thermal conductivity during the thermal storage process.

[0032] In some embodiments, the intelligent control module 4 is used to acquire the liquid phase fraction, temperature field distribution, and flow parameters of the phase change material, and to adjust the inlet temperature of the flow sensor 13 and the inner tube 111 according to the liquid phase fraction, temperature field distribution, and flow parameters, so as to avoid heat storage traps and maintain stable heat release power. The liquid phase fraction, temperature field distribution, and flow parameters can be obtained by monitoring with appropriate equipment.

[0033] In some embodiments, the air gap thermal resistance calculation unit is used to correct for abrupt changes in contact thermal resistance caused by the liquefaction flow and volume shrinkage of the phase change material. Exemplarily, the mathematical model for calculating the air gap thermal resistance is: , Among them, R gap For air gap thermal resistance, δ gap For real-time air gap thickness, K eff η is the effective thermal conductivity of the phase change material. liquid Let be the liquid phase fraction, and α be the gravity influence coefficient, with a value of 0.3-0.5.

[0034] Phase change materials exhibit two behaviors that lead to air gaps during the solid-liquid transition: the melting stage and the solidification stage. During the melting stage, the liquid phase change material flows downwards under gravity, causing a detachment cavity to appear on the wall of the upper heat exchange tube 11. ηliquid The temperature rises, but the contact area between the phase change material and the heat exchange tube 11 decreases. During the solidification stage, the phase change material shrinks in volume, with paraffin shrinking by 10%-15%, forming a micron-sized air gap between the heat exchange tube 11 wall and the material. liquid The thermal resistance of the phase change material decreases, but it actually increases. Traditional models in related technologies assume a constant contact thermal resistance, leading to an increase in η. liquid When the value is approximately 0.5, the simulation error can reach over ±25%.

[0035] In this embodiment, δ gap / K eff The air gap thickness δgap is measured in real time by a displacement sensor, achieving 5-8 times greater accuracy than empirical estimates. The correction factor is [1+α(1-η]. liquid ) 2 ], when η liquid When η = 0, the phase change material is entirely solid; with a correction factor of 1, there is no flow in the phase change material, and the air gap is at its maximum. When η... liquid =1, the phase change material is in a fully liquid state; correction factor =1, the phase change material is completely wetted, and the air gap of the phase change material is minimized. When η liquid When the coefficient of variation is approximately 0.5, the phase change material is in a semi-molten state, and the correction factor reaches its peak value of 1 + 0.25α. At this point, the superposition of flow and contraction effects is most intense. Therefore, in this embodiment, the mathematical model for calculating air gap thermal resistance can improve the prediction accuracy of air gap thermal resistance.

[0036] When the phase change thermal storage heat exchange system is in the thermal storage stage, η liquid The error ranges from 0 to 0.7. Traditional models have an error of +18% to -22%, while this mathematical model has an error of ±6.5%. The corresponding improvement in the phase change thermal storage heat exchange system control involves triggering the phase change material flow rate increase 15 seconds in advance, which can avoid localized overheating. When the phase change thermal storage heat exchange system is in the exothermic phase, η... liquid The error of the traditional model is -25% to +15%, while the error of this mathematical model is ±7.2%. The corresponding improvement in the control of the phase change thermal storage system is the precise timing of air gap compensation activation, preventing thermal storage traps. After 200 cycles of the phase change thermal storage system's operation in both the storage and release phases, the error of the traditional model is ±30%, while the error of this mathematical model remains within 8%. The corresponding improvement in the control of the phase change thermal storage system is a 3-fold increase in the accuracy of lifespan prediction.

[0037] In some embodiments, the intelligent control module 4 includes a plurality of second temperature sensors 42, which are dispersedly disposed within the receiving cavity 211. The plurality of second temperature sensors 42 are used to obtain the temperature field distribution of the phase change material within the housing 21. For example, the plurality of second temperature sensors 42 are uniformly distributed within the receiving cavity 211 to obtain the temperature field distribution of the phase change material within the receiving cavity 211.

[0038] In some embodiments, the phase change material is a paraffin-kaolin-stearic acid ternary composite phase change material, with a material mass ratio of paraffin:stearic acid:kaolin = (17-19):(8-9):(4-5). The phase change temperature of the paraffin-kaolin-stearic acid ternary composite phase change material is 52.5°C-58°C, and the latent heat value is ≥175J / g. With this configuration, the phase change material in this embodiment improves heat storage efficiency and heat storage capacity.

[0039] In some embodiments, the preparation method of the paraffin-kaolin-stearic acid ternary composite phase change material is as follows: paraffin and stearic acid are melt-blended in a constant temperature water bath at 85°C-90°C according to a certain mass ratio, and then kaolin nanoparticles are added in three portions, with an interval of 15 minutes between each addition. During the preparation process, ultrasonic dispersion is performed using an ultrasonic power of 240W-360W to ensure that the ternary composite phase change material forms a stable three-dimensional network thermally conductive structure.

[0040] In some embodiments, the control unit 3 includes a graphite pad micro-compression device 32 connected to a flexible graphite pad 31. During heat storage of the phase change material, the phase change material changes from solid to liquid. Due to the solid-liquid phase change volume change, a heat transfer gap is created. At this time, the pressure of the graphite pad micro-compression device 32 on the flexible graphite pad 31 decreases, and the volume of the flexible graphite pad 31 increases, filling the heat transfer gap. Furthermore, graphite has good thermal conductivity, which can improve thermal conductivity. During heat release of the phase change material, the phase change material changes from liquid to solid. Due to the liquid-solid phase change volume change, the heat transfer gap decreases. At this time, the pressure of the graphite pad micro-compression device 32 on the flexible graphite pad 31 increases, and the volume of the flexible graphite pad 31 decreases, thereby preventing the housing 21 from cracking due to the increased volume of the phase change material. The graphite pad micro-compression device 32 is connected to the intelligent control module 4. The graphite pad micro-compression device 32 is controlled by the intelligent control module 4. The intelligent control module 4 obtains the air gap thermal resistance calculated by the air gap thermal resistance calculation unit and controls the graphite pad micro-compression device 32 according to the air gap thermal resistance, so that the flexible graphite pad 31 can be used to adaptively compensate for the heat transfer gap caused by the solid-liquid phase change volume change of the phase change material.

[0041] As attached Figure 2 As shown, in some embodiments, the inner surface of the heat exchange tube 11 is provided with serrated ribs 113, the helix angle of the serrated ribs 113 is 45°-60°, and the ratio of the rib height H of the serrated ribs 113 to the inner diameter R of the heat exchange tube 11 is 0.08-0.12. This design can enhance the fluid turbulence intensity of the heat exchange tube 11 and reduce the convective thermal resistance.

[0042] In some embodiments, the axial angle between the fins 22 and the inner tube 111 is 30°-90°, and the ratio of the spacing L1 between adjacent fins 22 to the thickness L2 of the phase change material is L1 / L2, where L1 / L2 is 0.15-0.25. This configuration enhances the heat storage and heat release efficiency of the phase change thermal storage unit 2, and while ensuring the heat storage and heat release efficiency of the phase change thermal storage unit 2, it also sets the number of fins 22 within a reasonable range, reducing the cost of the phase change thermal storage heat exchange system.

[0043] In some embodiments, the fin 22 has a fractal tree structure, and the fin 22 includes a connected trunk and multiple branches. The ratio of the branch length L3 to the fin 22 length L is 0.3-0.7. This configuration can enhance the thermal conductivity of the fin 22, thereby improving the heat storage efficiency and heat release efficiency.

[0044] In some embodiments, the surface of the fin 22 is coated with a black nickel coating with a thickness of 50μm-80μm and an emissivity >0.92. This configuration can enhance the combined thermal conductivity and radiation heat transfer of the fin 22.

[0045] As can be seen from the above embodiments, the phase change thermal energy storage and heat exchange system of this application solves the bottleneck problems such as poor thermal conductivity, thermal storage traps and local overheating that exist in related phase change thermal energy storage systems.

[0046] This application also provides a control method applicable to any of the phase change thermal energy storage and heat exchange systems described in the above embodiments. (See attached...) Figure 3 As shown, the control methods include: In the heat storage stage of a phase change thermal energy storage and exchange system: S101: When the liquid phase fraction of the phase change material is detected to be <30%, the inlet temperature of the inner tube 111 is controlled to be 15°C-20°C higher than the phase change point, and the flow rate of the heat exchange tube 11 is 0.3m / s-0.5m / s; S102: When the liquid phase ratio is detected to be >70%, the inlet temperature of the inner tube 111 is controlled to be 25°C-30°C, and the flow rate of the heat exchange tube 11 is 0.6m / s-0.8m / s.

[0047] The inlet temperature of the inner tube 111 is monitored by a first temperature sensor, and the flow rate of the heat exchange tube 11 is obtained by a flow sensor. When the liquid phase fraction is >70%, it automatically switches to a high-temperature, high-speed mode (inlet temperature 25°C-30°C higher, flow rate 0.6m / s-0.8m / s) to avoid "heat storage traps".

[0048] During the heat release phase of a phase change thermal storage and heat exchange system: S201: The initial flow velocity of heat exchange tube 11 is set to 0.4 m / s. For every 10% decrease in liquid phase fraction, the flow velocity of heat exchange tube 11 increases by 0.1 m / s until it reaches 0.8 m / s. This setting can maintain a stable heat release power of the phase change thermal storage system.

[0049] S301: When the air gap thermal resistance of the phase change thermal storage system exceeds the preset threshold of 0.05 m²·K / W, the graphite pad micro-compression device 32 is activated to dynamically compress and compensate the heat transfer gap. The air gap thermal resistance is calculated by the air gap thermal resistance calculation unit. Activating the graphite pad micro-compression device 32 compresses the flexible graphite pad 31, reducing its volume; or, reducing the pressure of the graphite pad micro-compression device 32 on the flexible graphite pad 31 increases its volume, thereby dynamically compressing and compensating the heat transfer gap. This setting can prevent local overheating of the phase change thermal storage unit 2.

[0050] Understandably, steps S101, S102, S201, and S301 are executed in different threads, and each step does not interfere with the others. Steps S101 and S102 are not sequential; the labels are for easy identification and description.

[0051] In some embodiments, the mathematical model for calculating the air gap thermal resistance is: , Among them, R gap For air gap thermal resistance, δ gap For real-time air gap thickness, K eff η is the effective thermal conductivity of the phase change material. liquid Let be the liquid phase fraction, and α be the gravity influence coefficient, with a value of 0.3-0.5. The mathematical model for calculating air gap thermal resistance is used to correct for abrupt changes in contact thermal resistance caused by the liquefaction flow and volume shrinkage of the phase change material.

[0052] Phase change materials exhibit two behaviors that lead to air gaps during the solid-liquid transition: the melting stage and the solidification stage. During the melting stage, the liquid phase change material flows downwards under gravity, causing a detachment cavity to appear on the wall of the upper heat exchange tube 11. η liquid The temperature rises, but the contact area between the phase change material and the heat exchange tube 11 decreases. During the solidification stage, the phase change material shrinks in volume, with paraffin shrinking by 10%-15%, forming a micron-sized air gap between the heat exchange tube 11 wall and the material. liquid The thermal resistance of the phase change material decreases, but it actually increases. Traditional models in related technologies assume a constant contact thermal resistance, leading to an increase in η. liquid When the value is approximately 0.5, the simulation error can reach over ±25%.

[0053] In this embodiment, δ gap / Keff The air gap thickness δgap is measured in real time by a displacement sensor, achieving 5-8 times greater accuracy than empirical estimates. The correction factor is... When η liquid When η = 0, the phase change material is entirely solid; with a correction factor of 1, there is no flow in the phase change material, and the air gap is at its maximum. When η... liquid =1, the phase change material is in a fully liquid state; correction factor =1, the phase change material is completely wetted, and the air gap of the phase change material is minimized. When η liquid When the coefficient of variation is approximately 0.5, the phase change material is in a semi-molten state, and the correction factor reaches its peak value of 1 + 0.25α. At this point, the superposition of flow and contraction effects is most intense. Therefore, in this embodiment, the mathematical model for calculating air gap thermal resistance can improve the prediction accuracy of air gap thermal resistance.

[0054] In some embodiments, the control method includes constructing a heat transfer correlation law model, and the steps of constructing the heat transfer correlation law model include S401, S402, S403, and S404.

[0055] S401: Establish the four-region coupled energy conservation equation of heat exchange medium-heat exchange tube 11-fin 22-phase change material; S402: The non-uniform anisotropic melting process of phase change materials was simulated using the LBM-enthalpy porous media model. S403: Obtaining the dimensionless correlation equation through dimensional analysis: In this context, Nu refers to the Nusselt number, which is dimensionless; Ste is the Stefan number; C is the fin 22 structure correction factor; β is the phase change interface dynamic correction factor; Re is the Reynolds number; and Pr is the Prandtl number. By introducing the dimensionless correlation between Re and Pr, the synergistic influence of flow state and fluid thermal properties on the heat transfer performance of the phase change thermal storage and release system can be quantified, providing a theoretical basis for the intelligent control module 4. For example, the pump speed can be adjusted according to the real-time Re number to maintain turbulent enhanced heat transfer, or the control strategy can be optimized according to the change of Pr number (different heat transfer media). The sensitivity coefficient determines the priority of the control strategy. This layered control strategy based on the sensitivity coefficient shortens the development cycle of the phase change thermal storage and release system by 20-25%, reduces manufacturing costs by 15-18%, and ensures core performance indicators.

[0056] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A phase change thermal energy storage and heat exchange system, characterized in that, include: A heat exchange fluid circuit includes a heat exchange tube, a circulating pump, a flow sensor, and a first temperature sensor. The heat exchange tube includes an inner tube and an outer tube connected together. The circulating pump, the flow sensor, and the first temperature sensor are disposed on the outer tube. A phase change thermal energy storage unit includes a housing with a receiving cavity filled with a phase change material, an inner tube located in the receiving cavity and extending in a tortuous manner within the receiving cavity, and the receiving cavity having multiple fins connected to the outer wall of the inner tube. The control unit includes a flexible graphite pad, which is disposed between the phase change material and the outer wall of the inner tube. The flexible graphite pad is used to adaptively compensate for the heat transfer gap caused by the volume change of the phase change material due to the solid-liquid phase change. The intelligent control module includes an air gap thermal resistance calculation unit, and the intelligent control module is connected to the control unit, the circulating pump, the flow sensor and the first temperature sensor.

2. The phase change thermal energy storage and heat exchange system according to claim 1, characterized in that, The intelligent control module is used to acquire the liquid phase fraction, temperature field distribution and flow parameters of the phase change material, and to control the flow sensor and the inlet temperature of the inner tube according to the liquid phase fraction, temperature field distribution and flow parameters. and / or The air gap thermal resistance calculation unit is used to correct the sudden change in contact thermal resistance caused by the liquefaction flow and volume shrinkage of the phase change material.

3. The phase change thermal energy storage and heat exchange system according to claim 2, characterized in that, The intelligent control module includes multiple second temperature sensors, which are distributed within the accommodating cavity.

4. The phase change thermal energy storage and heat exchange system according to claim 1, characterized in that, The phase change material is a paraffin-kaolin-stearic acid ternary composite phase change material. The mass ratio of the paraffin-kaolin-stearic acid ternary composite phase change material is paraffin:stearic acid:kaolin = (17-19):(8-9):(4-5). The phase change temperature of the paraffin-kaolin-stearic acid ternary composite phase change material is 52.5°C-58°C, and the latent heat value is ≥175J / g.

5. The phase change thermal energy storage and heat exchange system according to claim 4, characterized in that, The preparation method of the paraffin-kaolin-stearic acid ternary composite phase change material is as follows: paraffin and stearic acid are melted and mixed in a constant temperature water bath at 85°C-90°C according to the mass ratio, and then kaolin nanoparticles are added in three portions, with an interval of 15 minutes between each addition. During the preparation process, dispersion is achieved using ultrasound, with an ultrasound power of 240W-360W.

6. The phase change thermal energy storage and heat exchange system according to claim 1, characterized in that, The control unit includes a graphite pad micro-compression device, which is connected to the flexible graphite pad and the intelligent control module.

7. The phase change thermal energy storage and heat exchange system according to claim 1, characterized in that, The inner surface of the heat exchange tube is provided with serrated ribs, the helix angle of the serrated ribs is 45°-60°, and the ratio of the rib height H of the serrated ribs to the inner diameter R of the heat exchange tube is 0.08-0.

12.

8. The phase change thermal energy storage and heat exchange system according to claim 1, characterized in that, The angle between the fins and the axial direction of the inner tube is 30°-90°, and the ratio of the spacing L1 between adjacent fins to the thickness L2 of the phase change material is 0.15-0.25; and / or The fin has a fractal tree-like structure, comprising a connected main trunk and multiple branches, wherein the ratio of the branch length L3 to the fin length L is 0.3-0.7; and / or The fin surface is coated with a black nickel coating with a thickness of 50μm-80μm, and the emissivity of the black nickel coating is >0.

92.

9. A control method, characterized in that, The control method, applied to the phase change thermal energy storage and heat exchange system as described in any one of claims 1-8, includes: The heat storage stage of the phase change thermal energy storage and heat exchange system: When the liquid phase fraction of the phase change material is detected to be <30%, the inlet temperature of the inner tube is controlled to be 15°C-20°C higher than the phase change point, and the flow velocity of the heat exchange tube is 0.3m / s-0.5m / s; When the liquid phase fraction is detected to be >70%, the inlet temperature of the inner tube is controlled to be 25°C-30°C, and the flow rate of the heat exchange tube is 0.6m / s-0.8m / s; During the heat release phase of the phase change thermal storage and heat exchange system: The initial flow velocity of the heat exchange tube is set to 0.4 m / s. For every 10% decrease in the liquid phase fraction, the flow velocity of the heat exchange tube increases by 0.1 m / s until it reaches 0.8 m / s, in order to maintain a stable heat release power. When the air gap thermal resistance of the phase change thermal storage heat exchange system exceeds the preset threshold of 0.05 m²·K / W, the graphite pad micro-compression device is activated to dynamically compress and compensate the heat transfer gap.

10. The control method according to claim 9, characterized in that, The mathematical model for calculating the air gap thermal resistance is as follows: ， Among them, R gap For air gap thermal resistance, δ gap For real-time air gap thickness, K eff η is the effective thermal conductivity of the phase change material. liquid Let be the liquid phase fraction, and α be the gravity influence coefficient, with a value of 0.3-0.5.

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