A zero-energy building thermal management system using bidirectional pulsating heat pipes and phase change materials

Abstract

This invention discloses a zero-energy building thermal management system using a bidirectional pulsating heat pipe in conjunction with a phase change material (PCM). The system includes a composite PCM energy storage / release wall, a bidirectional self-excited pulsating heat pipe, an evaporation section tube, a cooling section tube, a Tesla valve structure, a porous gel evaporative cooling structure, and a radiant cooling plate. A steam recovery chamber is provided between the porous gel evaporative cooling structure and the radiant cooling plate. The cooling section tube is embedded within the porous gel evaporative cooling structure. By incorporating the bidirectional self-excited pulsating heat pipe within the composite PCM energy storage / release wall and connecting it to the combined cooling system, this system improves the efficiency of the bidirectional self-excited pulsating heat pipe, enhances the heat release capacity of the composite PCM energy storage / release wall at night and its heat storage capacity during the day, solves the problem of insufficient regeneration rate of the PCM wall during the cooling season, and addresses the issue of low energy efficiency in multi-effect composite passive cooling building systems during the cooling season.

Description

Technical Field

[0001] This invention relates to the field of building energy conservation technology, specifically to a zero-energy building thermal management system with bidirectional pulsating heat pipes and phase change materials. Background Technology

[0002] With the acceleration of urbanization and the increasing demand for comfortable living environments, heating and air conditioning equipment are gradually increasing, leading to a continuous rise in building energy consumption and the resulting carbon emissions. Currently, building energy consumption accounts for more than 30% of total energy consumption. Among all building energy consumption, heating, air conditioning, and ventilation account for about 50% to 60%, especially in hot-summer and cold-winter regions, where the proportion of building heating and air conditioning energy consumption can even reach 65%. Therefore, under the dual pressure of fossil fuel depletion and environmental degradation, effective passive building energy-saving technologies can significantly reduce buildings' dependence on artificial energy and fully utilize their ingenious building structural design and natural cooling methods to meet the needs of indoor living and working environments, thus contributing to the development and construction of future green zero-carbon buildings.

[0003] Studies have found that the heat / cooling load generated by heat transfer through the building envelope has a significant impact on the energy consumption of building HVAC systems. By rationally designing and optimizing the building envelope itself, the additional air conditioning energy consumption caused by outdoor environmental heat disturbances through the building envelope can be significantly reduced. Embedded coupling systems have excellent energy-saving effects in temperate climate zones (such as Kunming) and hot-summer-cold-winter regions (such as Wuhan). Compared with ordinary buried pipe air conditioning systems, embedded pipe wall systems can achieve energy-saving efficiency of up to 30%. However, the circulating working fluid of the internal pipe system still requires an additional power source such as a water pump, resulting in additional energy consumption. Energy-saving building envelopes using phase change materials as building energy storage and heat insulation do not require an additional power source like water pump pipe systems and can effectively reduce indoor heat gain or heat loss caused by heat transfer from the building envelope. Studies have found that a 5 mm thick phase change wall has twice the heat storage capacity of a wall without phase change materials, equivalent to the heat storage strength of an 8 cm thick concrete wall. Theoretically, a reasonable phase change material enclosure structure can reduce the maximum cooling load in summer by 35.4% and the heating load in winter by 12.8%. However, the low thermal conductivity of most organic phase change materials (such as paraffin at 0.2-0.3 W / m*K) results in slow heat dissipation from the building envelope. When the air temperature is high during the day or night, the phase change material inside the building envelope cannot completely solidify and regenerate under the action of air convection, which significantly reduces the energy efficiency during the cooling season. This incomplete regeneration phenomenon results in a system energy saving rate of only 3.4%-3.9% during the cooling season, and even as low as 1% in some Mediterranean climate zones. Traditional optimization methods use siphon heat pipes or planar heat pipes to replace the embedded piping system and combine them with phase change walls, which can improve the above problems to some extent. However, they cannot solve the heat conduction loss caused by the planar maintenance structure and require additional energy to provide a cold source support for the heat pipes. Furthermore, due to the capillary force limitation inside the flat heat pipe, the thermal driving force is weak, resulting in a reduced heat transfer limit and failing to accurately improve the phase change thermal conductivity of the phase change material.

[0004] The serpentine structure of the pulsating heat pipe can effectively solve the carrying limit problem caused by gas-liquid counterflow. The variability of the working fluid makes it more flexible to be used in different scenarios. Depending on different design requirements, its equivalent thermal resistance can be as low as 0.2K / W, and its heat transfer efficiency can reach 12.5 times that of copper plates. Its ability to start working under changing gravity fields and its flexible structure make it more suitable for the variable characteristics of building structures.

[0005] Radiation cooling utilizes the difference in atmospheric transmittance to electromagnetic waves of different frequencies to effectively dissipate heat into the depths of space through an "atmospheric window" in the wavelength range of 8 to 13 micrometers. By releasing thermal radiation into outer space through mid-infrared rays, it can achieve cooling below ambient temperature in a non-energy-consuming manner. This passive cooling method is very suitable for the needs of passive energy-saving buildings, but its limit of only 150w / ㎡ heat dissipation power density is relatively low, and there is still room for optimization as a cold source. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the prior art by providing a zero-energy building thermal management system for bidirectional pulsating heat pipes and phase change materials.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A zero-energy building thermal management system using a bidirectional pulsating heat pipe and a phase change material (PCM) includes a composite PCM energy storage / release wall and a bidirectional self-excited pulsating heat pipe connected to the composite PCM energy storage / release wall. The bidirectional self-excited pulsating heat pipe includes a connected evaporation section and a cooling section. The evaporation section is equipped with a Tesla valve structure and is embedded in the composite PCM energy storage / release wall. The cooling section is located in a combined cooling system above the building. The combined cooling system includes a porous gel evaporative cooling structure and a radiant cooling plate connected to the porous gel evaporative cooling structure. A vapor recovery chamber is provided between the porous gel evaporative cooling structure and the radiant cooling plate. The cooling section is embedded in the porous gel evaporative cooling structure.

[0009] This zero-energy building thermal management system, which integrates bidirectional pulsating heat pipes with phase change materials, improves the efficiency of the bidirectional self-excited pulsating heat pipes by installing them within the composite phase change material energy storage / release wall and connecting them to the combined cooling system. This enhances the heat release capacity of the composite phase change material energy storage / release wall at night and its heat storage capacity during the day, addressing the problem of insufficient regeneration rate of the phase change material wall during the cooling season and the low energy efficiency of multi-effect composite passive cooling building systems during the cooling season. Furthermore, it can operate fully or partially adaptively according to environmental conditions, meeting the building's high cooling demands with extremely low energy consumption, significantly improving the building's cooling capacity, reducing primary energy consumption, and minimizing carbon emissions during the creation of the building's artificial environment.

[0010] Furthermore, the composite phase change material energy storage / release wall includes at least a south wall and a north wall, both of which include a concrete outer wall and a phase change material plate disposed within the concrete outer wall. An aluminum plate is also disposed between the phase change material plate and the concrete outer wall. The evaporation section tube is respectively embedded in the phase change material plates of the south wall and the north wall.

[0011] Furthermore, the phase change material plate is composed of at least a mixture of paraffin wax, lauric acid, stearic acid and sodium sulfate hydrate, and the phase change temperature of the phase change material plate is 25±2℃.

[0012] Furthermore, the cooling section pipe is provided with the evaporation section pipe at both ends, and the three are connected to form a double-ended three-dimensional semi-frame structure; the evaporation section pipe includes at least two U-shaped pipe sections, and the Tesla valve structure is connected to the outside of the U-shaped pipe sections respectively.

[0013] Furthermore, a sintered capillary wick is formed on the inner wall of the evaporation section tube.

[0014] Furthermore, the bidirectional self-excited pulsating heat pipe is filled with a low-boiling-point mixed working fluid, which is mainly composed of acetone and contains added iron oxide, wherein the mass fraction of iron oxide is 0.1 wt%. The overall liquid filling rate of the low-boiling-point mixed working fluid is not less than 60%, and the gas pressure inside the pipe is ensured to be lower than 2 kPa before the low-boiling-point mixed working fluid is injected into the bidirectional self-excited pulsating heat pipe.

[0015] Furthermore, the porous gel evaporation cooling structure is an open-top box structure, the radiative cooling plate is installed at the open top, and the bottom and sides of the porous gel evaporation cooling structure are also covered with heat-insulating sealing plates.

[0016] Furthermore, an atmospheric window coating is provided above the radiative cooling plate, and several arc-shaped condensation guiding rib structures are provided below the radiative cooling plate, with a hydrophobic material coating on the arc-shaped condensation guiding rib structures.

[0017] Furthermore, the porous gel evaporation cooling structure is composed of a multi-framework foam metal intercalated with a superabsorbent hydrogel. The multi-framework foam metal is made of nano-copper, and the superabsorbent hydrogel is made of low-crosslinked sodium acrylate, with sodium chloride solution as the base solution for the low-crosslinked sodium acrylate.

[0018] The aforementioned zero-energy building thermal management system with bidirectional pulsating heat pipe and phase change material includes at least the following three operating modes:

[0019] During the daytime conventional thermal radiation mode: the composite phase change material storage / release wall on the south side absorbs heat under sunlight during the day, while the composite phase change material storage / release wall on the north side absorbs heat under diffused light during the day. When the temperature exceeds 24℃, a pressure difference is formed in the working fluid vaporization pipes of the evaporation section pipes on the south and north sides. The working fluid forms a stable circulation from the evaporation section pipes on the south side, through the cooling section pipes, through the evaporation section pipes on the north side, through the cooling section pipes, back to the evaporation section pipes on the south side. The stable circulation ensures that the working fluid carries heat from the evaporation section pipes to the cooling section pipes for dissipation.

[0020] High-temperature daytime radiation pattern: Under high temperature conditions, the liquefaction of the phase change material plate in the composite phase change material storage / release wall on the south side drives the evaporation section tube on the south side to absorb heat. The working fluid inside the tube vaporizes, and the bidirectional self-excited pulsating heat pipe starts to work, carrying the heat to the cooling section tube for absorption by the combined cooling system. At this time, the heat that is not dissipated will continue to be stored in the high-temperature working fluid in the bidirectional self-excited pulsating heat pipe and will reach the evaporation section tube on the north side with the circulation. The temperature of the working fluid inside the evaporation section tube on the north side is higher than the temperature of the phase change material plate in the composite phase change material storage / release wall on the north side, so the heat is absorbed and stored by the phase change material plate on the north side.

[0021] Nighttime operation mode: The phase change temperature of the composite phase change material is higher than the vaporization temperature of the working fluid inside the bidirectional self-excited pulsating heat pipe. Under the condition of no solar radiation at night, the liquid phase change material in the composite phase change material energy storage / release wall on the south side and the composite phase change material energy storage / release wall on the north side drives the bidirectional self-excited pulsating heat pipe to continue working, carrying the energy stored during the day to the combined cooling system for dissipation through the circulation of the working fluid. The energy stored in the composite phase change material is dissipated on the outside of the composite phase change material energy storage / release wall on the south side and the north side through convection heat exchange with the natural environment, while the energy stored in the composite phase change material is dissipated inside through the bidirectional self-excited pulsating heat pipe.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The zero-energy building thermal management system of the present invention, which combines bidirectional pulsating heat pipes with phase change materials, improves the working efficiency of the bidirectional self-excited pulsating heat pipes by setting the bidirectional self-excited pulsating heat pipes in the composite phase change material energy storage / release wall and connecting them to the combined cooling system. This enhances the heat release capacity of the composite phase change material energy storage / release wall at night and the heat storage capacity during the day, solves the problem of insufficient regeneration rate of the phase change material wall during the cooling season, and addresses the problem of low energy efficiency of the multi-effect composite passive cooling building system during the cooling season; 2. The present invention improves the internal pressure difference of the bidirectional self-excited pulsating heat pipe through the above structure, enhances the driving force of the working fluid of the bidirectional self-excited pulsating heat pipe, strengthens the phase change process of the working fluid, and enables the gas-liquid two-phase system to have a stable circulating transport path, resulting in superior temperature uniformity; it also increases the number of hydrogel evaporation nuclei and the evaporative cooling intensity, and increases the hydrogel... The increased contact area with the surrounding environment enhances the rewetting ability of hydrogel nanoparticles; 3. This invention also solves the problems of weak heat dissipation capacity, weak regeneration capacity during the cooling season, and low energy efficiency of existing phase change material energy storage / release wall envelope structures. During the cooling season, the heat from the sunny side of the south wall is transferred to the roof through bidirectional self-excited pulsating heat pipes and dissipated through hydrogel evaporation cooling, or transferred to the shady side of the north wall for storage. At night, the combined action of hydrogel evaporation cooling and radiation cooling completes the removal of residual heat from the wall, completing the regeneration cycle of the phase change material energy storage / release wall. Furthermore, the bidirectional self-excited pulsating heat pipes will automatically stop working when the ambient temperature drops to prevent indoor heat dissipation in winter, reducing the air conditioning load required by the building; 4. This system integrates technologies such as pulsating heat pipes, radiation cooling, hydrogel evaporation cooling, and phase change energy storage, and is suitable for zero-consumption (or near-zero energy consumption) green energy-saving buildings. Attached Figure Description

[0023] Figure 1 This is a three-dimensional structural diagram of a zero-energy building thermal management system for a bidirectional pulsating heat pipe synergistic phase change material according to the present invention.

[0024] Figure 2 for Figure 1 Cross-sectional view of the composite phase change material energy storage / release wall on the south side of section AA;

[0025] Figure 3 for Figure 1 Cross-sectional view of the composite phase change material energy storage / release wall on the north side of section B;

[0026] Figure 4 for Figure 1 Schematic diagram of the three-dimensional structure of a bidirectional self-excited pulsating heat pipe;

[0027] Figure 5 for Figure 1 Front view of the combined cooling system of mid-sky radiation and porous gel evaporation;

[0028] Figure 6 for Figure 1 Side view of a combined cooling system of mid-sky radiation and porous gel evaporation;

[0029] Figure 7 for Figure 1 Cross-sectional view of a porous gel evaporation and cooling structure with a C-section;

[0030] Figure 8 for Figure 5 Enlarged view of a portion of point D;

[0031] Figure 9 This is a schematic diagram of heat transfer in the thermal management system of this embodiment under high heat load in extreme weather conditions;

[0032] Figure 10 This is a schematic diagram of heat transfer in the thermal management system of this embodiment under normal heat load;

[0033] In the diagram: 1. South side composite phase change material energy storage / release wall; 2. Bidirectional self-excited pulsating heat pipe; 3. Combined cooling system; 4. North side composite phase change material energy storage / release wall; 501. South side concrete exterior wall; 502. North side concrete exterior wall; 601. South side aluminum plate; 602. North side aluminum plate; 701. South side phase change material plate; 702. North side phase change material plate; 801. South wall bidirectional self-excited pulsating heat pipe evaporation section; 80 2. North wall bidirectional self-excited pulsating heat pipe evaporator section; 901. South wall Tesla valve; 902. North wall Tesla valve; 10. Sintered capillary core; 11. Cooling section section; 12. Insulation sealing plate; 13. Radiant cooling plate; 1301. Hydrophobic material coating; 1302. Atmospheric window coating; 14. Porous gel evaporative cooling structure; 1401. Multi-frame foam metal; 1402. Superabsorbent gel; 15. Steam recovery chamber. Detailed Implementation

[0034] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely 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.

[0035] In the description of this invention, it should be noted that the terms "middle", "upper", "lower", "left", "right", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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. Therefore, they should not be construed as limitations on this invention.

[0036] Combination Figures 1 to 7 As shown, a zero-energy building thermal management system using a bidirectional pulsating heat pipe and a phase change material includes a composite phase change material energy storage / release wall (specifically, a south-side composite phase change material energy storage / release wall 1 and a north-side composite phase change material energy storage / release wall 4), and a bidirectional self-excited pulsating heat pipe 2 connected to the composite phase change material energy storage / release wall. The bidirectional self-excited pulsating heat pipe 2 includes a connected evaporation section pipe (specifically, a south-side bidirectional self-excited pulsating heat pipe evaporation section pipe 801 and a north-side bidirectional self-excited pulsating heat pipe evaporation section pipe 802) and a cooling... The evaporation section pipe 11 is equipped with a Tesla valve structure and is embedded in the composite phase change material energy storage / release wall. The cooling section pipe 11 is installed in the combined cooling system above the building. The combined cooling system includes a porous gel evaporation cooling structure 14 and a radiant cooling plate 13 connected to the porous gel evaporation cooling structure 14. A steam recovery chamber 15 is provided between the porous gel evaporation cooling structure 14 and the radiant cooling plate 13. The cooling section pipe 11 is embedded in the porous gel evaporation cooling structure 14.

[0037] This zero-energy building thermal management system, which integrates bidirectional pulsating heat pipes and phase change materials, improves the working efficiency of the bidirectional self-excited pulsating heat pipes 2 by installing them in the composite phase change material energy storage / release wall and connecting them to the combined cooling system. This enhances the heat release capacity of the composite phase change material energy storage / release wall at night and the heat storage capacity during the day, solves the problem of insufficient regeneration rate of the phase change material wall during the cooling season, and addresses the problem of low energy efficiency of multi-effect composite passive cooling building systems during the cooling season.

[0038] The composite phase change material energy storage / release wall can effectively insulate external heat and maintain the indoor temperature of the building at a comfortable level when the ambient temperature exceeds the human body temperature during the day. The bidirectional self-excited pulsating heat pipe exchanges heat with the phase change material in the composite phase change material energy storage / release wall through its evaporation section, and its cooling section can exchange heat with the porous gel evaporative cooling structure in the combined cooling system.

[0039] The bidirectional self-excited pulsating heat pipe 2 utilizes the difference in solar radiation intensity received by the south-facing and north-facing sides of a building during the day to create a corresponding pressure difference in the gaseous working fluid within the embedded south and north evaporation sections, driving the internal working fluid to passively operate. Under the combined effect of rooftop sky radiation and the cooling section of the porous gel evaporation combined cooling system, the passive operating efficiency of the bidirectional self-excited pulsating heat pipe 2 can be improved. The Tesla valve structure can expand the heat absorption surface area of ​​the evaporation section tube, and through its one-way valve characteristic, it allows the internal working fluid of the bidirectional self-excited pulsating heat pipe to operate in a localized oscillating manner within the gas plug. This creates a circulation from the south wall to the roof, then to the north wall, and back to the south wall. This circulation promotes the flow of heat along with the working fluid to the roof, where it is dissipated by both sky radiation and porous gel evaporation combined cooling system, thus enhancing daytime heat dissipation. Simultaneously, this circulation balances the temperature difference between the north and south walls. Furthermore, in extreme cases where the heat dissipation capacity of the sky radiation and porous gel evaporation combined cooling system is insufficient during extremely hot weather, the circulation of the working fluid can carry heat from the sun-facing side of the south wall to the shaded side of the north wall, where it is absorbed by the composite phase change material energy storage / release wall. This, in turn, improves the applied heat storage value of the composite phase change material energy storage / release wall on both the north and south sides and the actual utilization rate of the phase change material.

[0040] In the combined cooling system, the radiant cooling plate 13 achieves a cooling effect below atmospheric temperature by exchanging heat with space through the "atmospheric window," providing a cold source support for the bidirectional self-excited pulsating heat pipe 2. The porous gel evaporation cooling structure 14 can compensate for the insufficient cooling supply under a single radiant cooling plate heat dissipation structure, enabling the cooling section of the bidirectional self-excited pulsating heat pipe 11 to maintain a low temperature for continuous heat transfer.

[0041] This invention enhances the internal pressure difference of the bidirectional self-excited pulsating heat pipe through the aforementioned special structure, thereby strengthening the driving force of the working fluid and enhancing the phase change process of the working fluid. This results in a stable circulating transport path for the gas-liquid two phases, leading to superior temperature uniformity. It also increases the number of hydrogel evaporation nuclei and the intensity of evaporative cooling, and increases the contact area between the hydrogel and the surrounding environment, improving the rewetting ability of the hydrogel nanoparticles. Furthermore, this invention solves the problems of weak heat dissipation capacity, weak regeneration capacity during the cooling season, and low energy efficiency in existing phase change material energy storage / release wall envelope structures. During the cooling season, the bidirectional self-excited pulsating heat pipe... The heat from the sunny side of the south wall is transferred to the roof for evaporative cooling via hydrogel, or transferred to the shady side of the north wall for storage. At night, the combined action of hydrogel evaporative cooling and radiative cooling completes the regeneration cycle of the phase change material energy storage / release wall by removing excess heat from the wall. Furthermore, the bidirectional self-excited pulsating heat pipe automatically stops working when the ambient temperature drops to prevent indoor heat dissipation in winter, thus reducing the building's required air conditioning load. This system integrates technologies such as pulsating heat pipes, radiative cooling, hydrogel evaporative cooling, and phase change energy storage, and is suitable for zero-consumption (or near-zero energy consumption) green energy-saving buildings.

[0042] Furthermore, the composite phase change material energy storage / release wall includes at least a south wall and a north wall. Both the south wall and the north wall include concrete exterior walls (south concrete exterior wall 501 and north concrete exterior wall 502) and phase change material plates (south phase change material plate 701 and north phase change material plate 702) disposed within the concrete exterior walls. An aluminum plate (south aluminum plate 601 and north aluminum plate 602) is also disposed between the phase change material plate and the concrete exterior wall. The evaporation section tube is respectively embedded in the phase change material plates of the south wall and the north wall.

[0043] Specifically, the north-side phase change material (PCM) energy storage / release wall includes a north-side concrete exterior wall 502, a north-side aluminum plate 602, a north-side PCM plate 702, a north-side bidirectional self-excited pulsating heat pipe evaporation section tube 802, and a north-side Tesla valve 902. The north-side concrete exterior wall 502 provides external structural support, and the north-side PCM plate 702 is externally encapsulated by the north-side aluminum plate 602, which provides the necessary sealing for the PCM. Solar radiation is absorbed and stored by the north-side PCM plate 702 and then discharged through the north-side bidirectional self-excited pulsating heat pipe evaporation section tube 802 to the cooling section tube 11 of the roof bidirectional self-excited pulsating heat pipe. During the heat discharge process, the north-side Tesla valve 902 increases the heat absorption area of ​​the north-side bidirectional self-excited pulsating heat pipe evaporation section tube 802 and, through its one-way valve characteristics, allows the internal working fluid to form a stable circulation while undergoing local oscillation.

[0044] The south and north phase change material (PCM) energy storage / release walls have the same physical structure, but their functions differ due to the different distribution of solar radiation during actual operation. The north wall receives less solar radiation due to its shaded location, resulting in lower heat absorption and a lower melting rate for the PCM plate 702. Conversely, the south wall receives more solar radiation due to its sun-facing location, leading to higher heat absorption and a higher melting rate for the PCM plate 701. During the day, solar radiation is absorbed by the south and north PCM plates 701 and 702, and the heat is transferred to the cooling section 11 of the bidirectional self-excited pulsating heat pipe through the evaporation sections 801 and 802 on both walls. The heat is then dissipated through a combined cooling system 3 consisting of sky radiation and porous gel evaporation. Figure 9As shown. The south wall Tesla valve 901 and the north wall Tesla valve 902 can utilize their one-way valve characteristics to create a circulation of south wall-roof-north wall-south wall while the working fluid inside the bidirectional self-excited pulsating heat pipe 2 oscillates locally. When the ambient temperature and solar radiation increase and the heat dissipation load of the sky radiation and porous gel evaporation combined cooling system 3 is insufficient, the solar radiation load on the sunny side of the south wall can be absorbed by the south phase change material plate 701 and conducted through the evaporation section of the south wall bidirectional self-excited pulsating heat pipe tube 801. It is then conducted to the north phase change material plate 702 for absorption through the working fluid circulation formed by the south wall Tesla valve 901 and the north wall Tesla valve 902.

[0045] Furthermore, the cooling section pipe body 11 has evaporation section pipe bodies at both ends, and the three are connected to form a double-ended three-dimensional semi-frame structure; the evaporation section pipe body includes at least two U-shaped pipe sections, and the Tesla valve structure is connected to the outside of the U-shaped pipe sections respectively.

[0046] Specifically, the bidirectional self-excited pulsating heat pipe includes a connected bidirectional self-excited pulsating heat pipe evaporation section tube 801 on the south wall, a cooling section tube 11 on the roof, and a bidirectional self-excited pulsating heat pipe evaporation section tube 802 on the north wall. The bidirectional self-excited pulsating heat pipe evaporation section tube 801 on the south wall is embedded in the composite phase change material energy storage / release wall 1 on the south side, and the bidirectional self-excited pulsating heat pipe evaporation section tube 802 on the north wall is embedded in the composite phase change material energy storage / release wall 4 on the north side. The cooling section tube 11 on the roof is embedded in the combined cooling system of sky radiation and porous gel evaporation 3. The bidirectional self-excited pulsating heat pipe evaporation section tube 801 on the south wall contains multiple parallel evaporation tube bundles that maintain a certain spacing. The figure shows four tubes. In other words, the bidirectional self-excited pulsating heat pipe 2 can be varied according to different building dimensions in actual application. The number of tube bundles in the bidirectional self-excited pulsating heat pipe evaporation section tube 802 on the north wall and the cooling section tube 11 on the roof varies accordingly with the requirements of the building structure.

[0047] Furthermore, a sintered capillary core 10 is formed on the inner wall of the evaporation section tube. The sintered capillary core 10 is formed on the inner wall of both the south wall bidirectional self-excited pulsating heat pipe evaporation section tube 801 and the north wall bidirectional self-excited pulsating heat pipe evaporation section tube 802. The sintered capillary core 10 can effectively enhance the capillary force and heat absorption capacity of the bidirectional self-excited pulsating heat pipe evaporation section tube.

[0048] Furthermore, the phase change material plate is composed of at least a mixture of paraffin wax, lauric acid, stearic acid and sodium sulfate hydrate, and the phase change temperature of the phase change material plate is 25±2℃.

[0049] The bidirectional self-excited pulsating heat pipe is a one-piece tubular structure made of nano-copper with an outer diameter of 3mm and an inner diameter of 2mm, and has a liquid injection port. The inside is filled with a low-boiling-point mixed working fluid. In this embodiment, the low-boiling-point mixed working fluid is mainly composed of acetone, with the addition of 0.1wt% graphene oxide and surfactant. The overall liquid filling rate of the low-boiling-point mixed working fluid is not less than 60%. Before injecting the low-boiling-point mixed working fluid into the bidirectional self-excited pulsating heat pipe, it is ensured that the gas pressure inside the pipe is lower than 2kPa. That is, the gas pressure inside the pipe is pumped down to below 2kPa before injecting the low-boiling-point working fluid with a volume fraction of 60%, and then the liquid injection port is sealed.

[0050] Before injecting the low-boiling-point mixed working fluid, reducing the gas pressure inside the bidirectional self-excited pulsating heat pipe to below 2 kPa can lower the saturation temperature of the internal acetone working fluid to 24°C. When the environment enters the cooling season and the outside temperature exceeds 24°C, the bidirectional self-excited pulsating heat pipe automatically starts working. When the environment enters winter and the outside temperature drops below 24°C, the bidirectional self-excited pulsating heat pipe can autonomously stop working to prevent heat loss from the building interior during the heating season. Furthermore, the saturation temperature of the internal working fluid is lower than the phase change temperature of the composite phase change material, ensuring that when the composite phase change material is in a molten state, the bidirectional self-excited pulsating heat pipe can automatically work until the composite phase change material solidifies and regenerates.

[0051] Furthermore, the porous gel evaporation cooling structure 14 is an open-top box structure, with the radiative cooling plate 13 installed at the upper opening. The bottom and sides of the porous gel evaporation cooling structure 14 are also covered with an insulating sealing plate 12. An atmospheric window coating 1302 is provided above the radiative cooling plate 13, and several arc-shaped condensation guiding rib structures are provided below the radiative cooling plate 13. The arc-shaped condensation guiding rib structures are coated with a hydrophobic material coating 1301.

[0052] Specifically, the heat-insulating sealing plate 12 wraps around the sides and bottom of the combined cooling system 3, and the sides have embedded openings for the cooling section of the bidirectional self-excited pulsating heat pipe. The radiant cooling plate 13 is made of aluminum and has the atmospheric window coating 1302 on its top. Its bottom is formed into an arc-shaped condensation guide fin and has a hydrophobic material coating 1301. The porous gel evaporation cooling structure 14 is concave and is located inside the side and bottom of the sky radiation and porous gel evaporation combined cooling system 3. The side is connected to the top radiant cooling plate 13. The space between the concave part and the radiant cooling plate 13 forms a vapor recovery chamber 15. Preferably, the atmospheric window coating 1302 is made of ZS-411 material, which has a strong emissivity in the medium-long wavelength band of 8~13μm. It can achieve a cooling effect below the atmospheric temperature by radiating heat exchange with space through the "atmospheric window", providing cold source support for the bidirectional self-excited pulsating heat pipe. By fabricating an arc-shaped condensation guide fin structure on the back of the radiant cooling plate and laying a hydrophobic coating, the heat exchange area can be increased while promoting the timely return of gas condensate in the steam chamber to the porous gel evaporative cooling structure to complete steam recovery.

[0053] Furthermore, in combination Figure 8 As shown, the porous gel evaporation cooling structure 14 is composed of a multi-framework foam metal 1401 embedded with a superabsorbent hydrogel 1402. The multi-framework foam metal 1401 is made of nano-copper, and the superabsorbent hydrogel 1402 is made of low-crosslinked sodium acrylate, with sodium chloride solution as the base solution of the low-crosslinked sodium acrylate.

[0054] The porous gel evaporative cooling structure 14 integrates low-crosslinked sodium acrylate with multi-framework foam metal. Using sodium chloride solution as the base solution for low-crosslinked sodium acrylate can improve the water absorption and rewetting properties of the low-crosslinked sodium acrylate hydrogel. The multi-framework foam metal made of nano-copper is integrated into the low-crosslinked sodium acrylate hydrogel material as a thermally conductive framework for the hydrogel, which can improve the overall thermal conductivity and specific surface area of ​​the structure. The enthalpy of evaporation of water (2450 J / g) provides the heat dissipation performance of the structure. The porous gel evaporative cooling structure 14 can compensate for the insufficient cooling under a single radiative cooling plate heat dissipation structure, and promote the continuous heat transfer of the cooling section of the bidirectional self-excited pulsating heat pipe at a low temperature.

[0055] The working principle of this bidirectional pulsating heat pipe synergistic phase change material zero-energy building thermal management system is as follows:

[0056] The high latent heat value of phase change materials can absorb and store solar radiation absorbed by building walls during the day, reducing indoor energy consumption. During the day, the solar radiation power received by the south-facing and north-facing sides of the building differs by several times. The evaporator sections of the bidirectional self-excited pulsating heat pipes, arranged on both sides of the north and south walls, create a pressure difference under the natural difference in solar radiation power, thus driving the working fluid within the bidirectional self-excited pulsating heat pipes to passively operate. Under the action of the Tesla valve structure, the internal working fluid forms a stable circulation under localized oscillations, ensuring that heat can be transported with the working fluid to... The cooling section of the bidirectional self-excited pulsating heat pipe dissipates heat in a timely manner. It achieves efficient evaporative cooling by adsorbing liquid water molecules through superabsorbent hydrogel and combining the thermal conductivity and specific surface area of ​​the multi-framework foam metal reinforcement structure. At night, the sky radiation cooling plate made of ZS-411 coating achieves radiation cooling at absolute zero and realizes the condensation and recovery of water vapor. Both provide cold source support for the bidirectional self-excited pulsating heat pipe, increase the gas pressure difference in the pipe, enhance the driving force of the working fluid, and promptly export the heat stored in the phase change material wall and complete the condensation and regeneration of the phase change material at night.

[0057] One working process of this zero-energy building thermal management system using a bidirectional pulsating heat pipe and phase change material is as follows:

[0058] (1) Daytime routine thermal radiation working process

[0059] Combination Figure 10As shown, the south-side composite phase change material (PCM) energy storage / release wall 1 absorbs heat under sunlight during the day, while the north-side PCM energy storage / release wall 4 absorbs heat under diffused light during the day. The heat energy is absorbed and stored by the PCM plates 701 on the south side and 702 on the north side. After reaching the phase change temperature, the PCM plates 701 and 702 change from a solid phase to a liquid phase. If heat absorption continues, the PCM will continue to heat up. When the temperature exceeds 24℃, a pressure difference is formed in the working fluid vaporization pipes of either the south-side bidirectional self-excited pulsating heat pipe evaporation section 801 or the north-side bidirectional self-excited pulsating heat pipe evaporation section 802. Due to the significant difference in solar radiation intensity between the north and south sides, the radiative heat flux density on the south-facing sunny side is between 800 and 1000 W / m². The diffuse radiation heat flux density on the north-facing side is approximately 150 W / m², while the diffuse radiation heat flux density on the north-facing side is approximately 150 W / m². This high power difference will increase the pressure difference between the evaporator section 801 on the south wall and the evaporator section 802 on the north wall, providing additional driving force for the working fluid. Under the combined effect of the one-way valve characteristics of the Tesla valve 901 on the south wall and the Tesla valve 902 on the north wall, as well as the difference in heat flux density between the two evaporator sections, a stable circulation of the working fluid inside the bidirectional self-excited pulsating heat pipe 2 is formed. This circulation ensures that the liquid working fluid forms a circulation from the evaporator section 801 on the south wall → the cooling section 11 of the bidirectional self-excited pulsating heat pipe → the evaporator section 802 on the north wall → the cooling section 1 of the bidirectional self-excited pulsating heat pipe. 1→ The stable flow path of the evaporator section 801 of the bidirectional self-excited pulsating heat pipe on the south wall ensures that the working fluid carries heat from the evaporator section to the cooling section for dissipation. During the day, the solar radiation energy received by the roof is concentrated in the high-frequency band. The radiation cooling plate 13 in the combined sky radiation and porous gel evaporation cooling system 3 reduces the absorption of high-frequency light waves and increases the release of low-frequency infrared light waves through the ZS-411 material used in the atmospheric window coating 1302, thus achieving the effect of radiation cooling through the atmospheric window. Because the absorption of some bands of solar radiation cannot be avoided, the cooling effect of the radiation cooling plate 13 is limited during the day. By setting the porous gel evaporation cooling structure 14, the cooling demand during the day can be effectively compensated. The water molecules around the cooling section 11 of the bidirectional self-excited pulsating heat pipe embedded on the bottom absorb the heat from the evaporation section 801 of the bidirectional self-excited pulsating heat pipe on the south wall and the evaporation section 802 of the bidirectional self-excited pulsating heat pipe on the north wall, and then vaporize and dissipate into the steam recovery chamber 15. The gel around the pipe loses water and dries. The superabsorbent gel in the porous gel evaporation cooling structure 14 uses its high water absorption and the osmotic pressure difference of the water molecules around the pipe to capture the surrounding gel-bound water and the liquid water at the bottom of the steam recovery chamber to achieve gel rewetting and provide a continuous cooling effect. It removes the heat absorbed from the composite phase change material storage / release wall 1 on the south side and the composite phase change material storage / release wall 4 on the north side. The heat dissipation solves the problem of low energy-saving effect of traditional phase change material storage / release walls during the cooling season.

[0060] (2) Working process during extreme weather with high heat radiation during the day

[0061] Combination Figure 9 As shown, under extreme summer temperatures, the high heat flux density of the south wall causes the phase change material plate 701 on the south side to liquefy, driving the working fluid inside the absorber tube 801 of the evaporation section of the bidirectional self-excited pulsating heat pipe on the south wall to vaporize. The bidirectional self-excited pulsating heat pipe 2 begins to work, and the circulation formed by the one-way valves Tesla valve 901 on the south wall and Tesla valve 902 on the north wall carries the heat to the cooling section tube 11 of the bidirectional self-excited pulsating heat pipe, which is absorbed by the combined cooling system 3 of sky radiation and porous gel evaporation. However, extreme conditions cause the evaporation section tube of the bidirectional self-excited pulsating heat pipe on the south wall to... When the temperature of the working fluid inside the 801 heat absorber is too high, the cooling load of the combined cooling system 3 (sky radiation and porous gel evaporation) becomes excessive. The undissipated heat will continue to be stored in the high-temperature working fluid inside the bidirectional self-excited pulsating heat pipe 2 and will reach the evaporation section 802 of the bidirectional self-excited pulsating heat pipe on the north wall via circulation. At this point, the temperature of the working fluid inside the evaporation section 802 of the bidirectional self-excited pulsating heat pipe on the north wall is higher than the temperature of the north phase change material plate 702 in the north composite phase change material energy storage / release wall 4. Therefore, the heat is absorbed and stored by the north phase change material plate 702. This achieves the storage of heat from the south side on the north side, improving the overall utilization rate of the building's phase change materials, thereby delaying the rise in indoor temperature and reducing indoor energy consumption under extreme weather conditions.

[0062] (3) Nighttime operation mode

[0063] At night, because the phase change temperature of the composite phase change material is higher than the vaporization temperature of the working fluid inside the bidirectional self-excited pulsating heat pipe 2, the liquid phase change material in the south phase change material plate 701 and the north phase change material plate 702 can drive the bidirectional self-excited pulsating heat pipe 2 to continue working at night without solar radiation. Through the circulation of the working fluid, the energy stored during the day is carried to the sky for radiation and dissipation by the porous gel evaporation combined cooling system 3. The energy stored in the composite phase change material on the outside of the south composite phase change material storage / release wall 1 and the north composite phase change material storage / release wall 4 is dissipated by convection heat exchange with the natural environment, and the energy stored in the composite phase change material on the inside is dissipated by the bidirectional self-excited pulsating heat pipe 2. This improves the solidification and regeneration efficiency of the phase change material and solves the problem of low regeneration rate of traditional phase change material storage / release walls. Since there is no solar radiation at night, the cooling effect of the radiation cooling plate 13 will be improved. Under the combined action of the lower arc-shaped condensation guide fins and the hydrophobic material coating 1301, water vapor condensation and recovery are achieved.

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A zero-energy building thermal management system for bidirectional pulsating heat pipes and phase change materials, characterized in that, The system includes a composite phase change material (PCM) energy storage / release wall and a bidirectional self-excited pulsating heat pipe connected to the PCM energy storage / release wall. The PCM energy storage / release wall includes at least a south wall and a north wall. The bidirectional self-excited pulsating heat pipe includes a connected evaporation section and a cooling section. The evaporation section is equipped with a Tesla valve structure and is embedded in the PCM energy storage / release wall. The cooling section is located in a combined cooling system above the building. The combined cooling system includes a porous gel evaporative cooling structure and a radiant cooling plate connected to the porous gel evaporative cooling structure. A vapor recovery chamber is provided between the porous gel evaporative cooling structure and the radiant cooling plate. The cooling section is embedded in the porous gel evaporative cooling structure. The zero-energy building thermal management system includes at least the following three operating modes: During the daytime conventional thermal radiation mode: the composite phase change material storage / release wall on the south side absorbs heat under sunlight during the day, while the composite phase change material storage / release wall on the north side absorbs heat under diffused light during the day. When the temperature exceeds 24℃, a pressure difference is formed in the working fluid vaporization pipes of the evaporation section pipes on the south and north sides. The working fluid forms a stable circulation from the evaporation section pipes on the south side, through the cooling section pipes, through the evaporation section pipes on the north side, through the cooling section pipes, back to the evaporation section pipes on the south side. The stable circulation ensures that the working fluid carries heat from the evaporation section pipes to the cooling section pipes for dissipation. High-temperature daytime radiation pattern: Under high temperature conditions, the liquefaction of the phase change material plate in the composite phase change material storage / release wall on the south side drives the evaporation section tube on the south side to absorb heat. The working fluid inside the tube vaporizes, and the bidirectional self-excited pulsating heat pipe starts to work, carrying the heat to the cooling section tube for absorption by the combined cooling system. At this time, the heat that is not dissipated will continue to be stored in the high-temperature working fluid in the bidirectional self-excited pulsating heat pipe and will reach the evaporation section tube on the north side with the circulation. The temperature of the working fluid inside the evaporation section tube on the north side is higher than the temperature of the phase change material plate in the composite phase change material storage / release wall on the north side, so the heat is absorbed and stored by the phase change material plate on the north side. Nighttime operation mode: The phase change temperature of the composite phase change material is higher than the vaporization temperature of the working fluid inside the bidirectional self-excited pulsating heat pipe. Under the condition of no solar radiation at night, the liquid phase change material in the composite phase change material energy storage / release wall on the south side and the composite phase change material energy storage / release wall on the north side drives the bidirectional self-excited pulsating heat pipe to continue working, carrying the energy stored during the day to the combined cooling system for dissipation through the circulation of the working fluid. The energy stored in the composite phase change material is dissipated on the outside of the composite phase change material energy storage / release wall on the south side and the north side through convection heat exchange with the natural environment, while the energy stored in the composite phase change material is dissipated inside through the bidirectional self-excited pulsating heat pipe.

2. The zero-energy building thermal management system with bidirectional pulsating heat pipe and phase change material according to claim 1, characterized in that, Both the south wall and the north wall include a concrete exterior wall and a phase change material plate disposed within the concrete exterior wall. An aluminum plate is also disposed between the phase change material plate and the concrete exterior wall. The evaporation section pipe is respectively embedded in the phase change material plate of the south wall and the north wall.

3. The zero-energy building thermal management system with bidirectional pulsating heat pipe and phase change material according to claim 2, characterized in that, The phase change material plate is composed of at least a mixture of paraffin wax, lauric acid, stearic acid and sodium sulfate hydrate, and the phase change temperature of the phase change material plate is 25±2℃.

4. The zero-energy building thermal management system with bidirectional pulsating heat pipe and phase change material according to claim 1, characterized in that, The cooling section pipe is provided with the evaporation section pipe at both ends, and the three are connected to form a double-ended three-dimensional semi-frame structure; the evaporation section pipe includes at least two U-shaped pipe sections, and the Tesla valve structure is connected to the outside of the U-shaped pipe sections respectively.

5. The zero-energy building thermal management system with bidirectional pulsating heat pipe and phase change material according to claim 1, characterized in that, The inner wall of the evaporation section tube is also formed with sintered capillary cores.

6. The zero-energy building thermal management system with bidirectional pulsating heat pipe and phase change material according to claim 1, characterized in that, The bidirectional self-excited pulsating heat pipe is filled with a low-boiling-point mixed working fluid, which is mainly composed of acetone and contains added iron oxide, wherein the mass fraction of iron oxide is 0.1 wt%. The overall liquid filling rate of the low-boiling-point mixed working fluid is not less than 60%, and the gas pressure inside the pipe is ensured to be lower than 2 kPa before the low-boiling-point mixed working fluid is injected into the bidirectional self-excited pulsating heat pipe.

7. The zero-energy building thermal management system with bidirectional pulsating heat pipe and phase change material according to claim 1, characterized in that, The porous gel evaporation cooling structure is an open-top box structure, with the radiant cooling plate installed at the upper opening. The bottom and sides of the porous gel evaporation cooling structure are also covered with heat-insulating sealing plates.

8. The zero-energy building thermal management system with bidirectional pulsating heat pipe and phase change material according to claim 1, characterized in that, An atmospheric window coating is provided above the radiant cooling plate, and several arc-shaped condensation guiding rib structures are provided below the radiant cooling plate. The arc-shaped condensation guiding rib structures are coated with a hydrophobic material.

9. The zero-energy building thermal management system with bidirectional pulsating heat pipe and phase change material according to claim 1, characterized in that, The porous gel evaporation cooling structure is composed of a multi-framework foam metal intercalated with a superabsorbent hydrogel. The multi-framework foam metal is made of nano-copper, and the superabsorbent hydrogel is made of low-crosslinked sodium acrylate, with sodium chloride solution as the base solution for the low-crosslinked sodium acrylate.

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