Zero-energy-consumption building heat management system with bidirectional pulsating heat pipe cooperating with phase change material

Abstract

The invention discloses a zero-energy-consumption building heat management system with a bidirectional pulsating heat pipe cooperating with a phase change material, which comprises a composite phase change material energy storage / release wall body, a bidirectional self-excitation pulsating heat pipe, an evaporation section pipe body, a cooling section pipe body, a Tesla valve structure, a porous gel evaporation cooling structure and a radiation cooling plate, a steam recovery cavity is formed between the porous gel evaporative cooling structure and the radiation cooling plate, and the cooling section pipe body is embedded in the porous gel evaporative cooling structure. According to the system, the two-way self-excitation type pulsating heat pipe is arranged in the composite phase change material energy storage / release wall body and connected with the combined cooling system, so that the working efficiency of the two-way self-excitation type pulsating heat pipe can be improved, the heat release capacity at night and the heat storage capacity in the daytime of the composite phase change material energy storage / release wall body are improved, and the service life of the composite phase change material energy storage / release wall body is prolonged. The problems that the regeneration rate of a phase-change material wall is insufficient in the cold supply season and the energy efficiency of a multi-effect composite passive cooling building system is too low in the cold supply season are solved.

Description

Technical Field

[0001] The invention relates to the technical field of building energy conservation, and in particular to a zero-energy building thermal management system using a bidirectional pulsating heat pipe and phase-change materials. Background Art

[0002] With the acceleration of urbanization and the increasing demand for comfortable living environment, heating and air-conditioning equipment are gradually increasing, and building energy consumption and the resulting carbon emissions will continue to increase. At present, building energy consumption accounts for more than 30% of the total energy consumption. Among all building energy consumption, heating, air-conditioning and ventilation energy consumption account for about 50% to 60% of building energy consumption. Especially for areas with hot summers and cold winters, building heating and air-conditioning energy consumption even accounts for as much as 65%. Therefore, under the dual pressure of fossil energy depletion and environmental deterioration, effective passive building energy-saving technology can significantly reduce the dependence of buildings on artificial energy, and fully meet the needs of indoor living and working environment based on its own ingenious building structure design and natural cooling methods, so as to develop and build future green zero-carbon buildings.

[0003] The study found that the heat / cold load generated by heat transfer from the building envelope has a great impact on the energy consumption of the building's HVAC system. By rationally designing and optimizing the building envelope itself, the additional air-conditioning energy consumption caused by outdoor environmental thermal disturbances passing through the envelope can be greatly reduced. The embedded coupling system has a good energy-saving effect in mild climate zones (such as Kunming) and hot summer and cold winter areas (such as Wuhan). Compared with ordinary buried pipe air-conditioning systems, the energy-saving efficiency of the embedded pipe wall system can reach 30%, but the circulating working fluid of the internal piping system of the enclosure structure still needs to be driven by additional power sources such as water pumps, resulting in additional energy consumption; the energy-saving enclosure structure using phase change materials as building energy storage and heat insulation does not require additional power sources like water pump piping systems, and can effectively reduce indoor heat gain or heat loss caused by heat transfer of the enclosure structure. Studies have found that the heat storage capacity of a 5 mm thick phase change wall is twice that of a wall without phase change materials, which is equivalent to the heat storage strength of an 8 cm thick concrete wall. A reasonable phase change material maintenance structure can theoretically reduce the maximum cooling load in summer by 35.4% and the heat load in winter by 12.8%. However, the disadvantage of low thermal conductivity of most organic phase change materials (such as paraffin at 0.2-0.3W / m*K) makes the heat dissipation of the enclosure structure slow. When the air temperature is high during the day or at night, the phase change material inside the enclosure structure cannot be completely solidified and regenerated under the action of air convection, which greatly reduces the energy saving efficiency in the cooling season. This incomplete regeneration phenomenon makes the system energy saving rate in the cooling season only reach 3.4%-3.9%, and even only 1% in some Mediterranean climate zones. The traditional optimization method uses siphon heat pipes or flat heat pipes to replace the embedded pipe system and combine it with phase change walls. It can optimize the above problems to a certain extent, but it cannot solve the heat conduction loss caused by the flat maintenance structure and requires additional energy to provide cold source support for the heat pipe. In addition, due to the capillary force limitation in the flat heat pipe, the thermal driving force is weak, resulting in a reduced heat transfer limit, and the phase change thermal conductivity of the phase change material cannot be accurately improved.

[0004] The serpentine structure of the pulsating heat pipe can effectively solve the carrying limit problem caused by gas-liquid countercurrent. The variability of the working fluid enables it to be more flexibly used in different scenarios. According to different design requirements, its equivalent thermal resistance can be as low as 0.2K / W, and its heat transfer efficiency can be up to 12.5 times that of a copper plate. It can start working when the gravity field changes, and its structural characteristics that can be bent at will make it more suitable for the changing characteristics of building structures.

[0005] Radiative cooling utilizes the difference in the atmosphere's transmittance to electromagnetic waves of different frequencies to effectively dissipate heat into the depths of the universe through the "atmospheric window" within a wavelength range of 8 to 13 microns. Releasing thermal radiation to outer space through mid-infrared rays can achieve cooling below ambient temperature in an energy-free manner. This passive cooling method is very consistent with the needs of passive energy-saving buildings, but its limit is only 150w / ㎡, a relatively low heat dissipation power density, and there is still room for optimization as a cooling source. Summary of the invention

[0006] The purpose of the present invention is to provide a zero-energy building thermal management system that combines a bidirectional pulsating heat pipe with a phase change material to address the problems existing in the prior art.

[0007] To achieve the above object, the technical solution adopted by the present invention is: A zero-energy building thermal management system of a bidirectional pulsating heat pipe in cooperation with a phase change material, comprising a composite phase change material storage / release wall, and a bidirectional self-excited pulsating heat pipe connected to the composite phase change material storage / release wall; the bidirectional self-excited pulsating heat pipe comprises an evaporation section pipe body and a cooling section pipe body which are connected, the evaporation section pipe body is provided with a Tesla valve structure and is embedded in the composite phase change material storage / release wall, the cooling section pipe body is arranged in a joint cooling system above the building, the joint cooling system comprises a porous gel evaporative cooling structure, and a radiation cooling plate connected to the porous gel evaporative cooling structure, a steam recovery chamber is provided between the porous gel evaporative cooling structure and the radiation cooling plate, and the cooling section pipe body is embedded in the porous gel evaporative cooling structure.

[0008] The zero-energy building thermal management system of the bidirectional pulsating heat pipe and phase change material is able to improve the working efficiency of the bidirectional self-excited pulsating heat pipe by setting the bidirectional self-excited pulsating heat pipe in the composite phase change material storage / release wall and connecting the joint cooling system, thereby improving the heat release capacity of the composite phase change material storage / release wall at night and the heat storage capacity during the day, solving the problem of insufficient regeneration rate of the phase change material wall in the cooling season, and the problem of low energy efficiency of the multi-effect composite passive cooling building system in the cooling season. Moreover, it can fully or partially operate adaptively according to environmental conditions, meet the high cooling needs of the building with extremely low energy consumption, fully improve the cooling capacity of the building, reduce primary energy consumption, and reduce carbon emissions in the process of creating the building's artificial environment.

[0009] 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 exterior wall, and a phase change material plate arranged in the concrete exterior wall, and an aluminum plate is also arranged between the phase change material plate and the concrete exterior wall; the evaporation section pipe body is respectively embedded in the phase change material plates of the south wall and the north wall.

[0010] Furthermore, the phase change material plate is at least composed of a mixture of paraffin, lauric acid, stearic acid and hydrated sodium sulfate, and the phase change temperature of the phase change material plate is 25±2°C.

[0011] Furthermore, the evaporation section tube body is provided at both ends of the cooling section tube body, and the three are connected to form a double-end three-dimensional semi-frame structure; the evaporation section tube body includes at least two U-shaped tube sections, and the outer sides of the U-shaped tube sections are respectively connected to the Tesla valve structures.

[0012] Furthermore, a sintered capillary wick is formed on the inner wall of the evaporation section tube body.

[0013] Furthermore, a low-boiling-point mixed working fluid is injected into the bidirectional self-excited pulsating heat pipe, wherein the low-boiling-point mixed working fluid is mainly composed of acetone and iron oxide is added, wherein the mass fraction of iron oxide is 0.1wt%, and the overall liquid filling rate of the low-boiling-point mixed working fluid is not less than 60%, and before the low-boiling-point mixed working fluid is injected into the bidirectional self-excited pulsating heat pipe, the gas pressure in the pipe is ensured to be lower than 2kPa.

[0014] Furthermore, the porous gel evaporative cooling structure is a box structure with an upper opening, the radiation cooling plate is installed at the upper opening, and the bottom and side surfaces of the porous gel evaporative cooling structure are also covered with a heat insulating sealing plate.

[0015] Furthermore, an atmospheric window coating is provided above the radiation cooling plate, a plurality of arc-shaped condensation drainage fin structures are provided below the radiation cooling plate, and a hydrophobic material coating is provided on the arc-shaped condensation drainage fin structures.

[0016] Furthermore, the porous gel evaporative cooling structure is composed of a multi-skeleton foam metal embedded with a super absorbent gel, the multi-skeleton foam metal uses nano copper as a manufacturing material, the super absorbent gel uses low-crosslinked sodium acrylate as a material, and sodium chloride solution is used as a basic solution of the low-crosslinked sodium acrylate.

[0017] The zero-energy building thermal management system of the bidirectional pulsating heat pipe and phase change material includes at least the following three operating modes: Conventional heat radiation mode during the day: the composite phase change material storage / release wall on the south side absorbs heat under the irradiation of sunlight during the day, and the composite phase change material storage / release wall on the north side absorbs heat under the action of diffuse light during the day. When the temperature exceeds 24°C, a pressure difference is formed in the working medium gasification pipe in the evaporation section pipe body on the south and north sides, and the working medium forms a stable circulation from the evaporation section pipe body on the south side, the cooling section pipe body, the evaporation section pipe body on the north side, the cooling section pipe body to the evaporation section pipe body on the south side. The stable circulation ensures that the working medium brings heat from the evaporation section pipe body to the cooling section pipe body for dissipation; Radiation mode of hot weather during the day: Under high temperature conditions, the phase change material plate in the composite phase change material storage / release wall on the south side liquefies and drives the evaporation section pipe body on the south side to absorb heat, the working fluid in the pipe vaporizes, and the bidirectional self-excited pulsating heat pipe starts to work to bring heat to the cooling section pipe body to be absorbed by the combined cooling system; at this time, the heat that cannot be dissipated will continue to be stored in the high-temperature working fluid in the bidirectional self-excited pulsating heat pipe and reach the evaporation section pipe body on the north side with the circulation. The working fluid temperature inside the evaporation section pipe body 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, and the heat is absorbed and stored by the phase change material plate on the north side; Night 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. The liquid phase change material in the composite phase change material storage / energy release wall on the south side and the composite phase change material storage / energy release wall on the north side drives the bidirectional self-excited pulsating heat pipe to continue working in the absence of solar radiation at night, and brings the energy stored during the day to the combined cooling system for dissipation through the working fluid circulation. The composite phase change material storage / energy release wall on the south side and the composite phase change material storage / energy release wall on the north side dissipate the energy stored in the composite phase change material through convection heat exchange with the natural environment on the outside, and the energy stored in the composite phase change material is dissipated inside through the bidirectional self-excited pulsating heat pipe.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. The zero-energy building thermal management system of the bidirectional pulsating heat pipe and the phase change material is able to improve the working efficiency of the bidirectional self-excited pulsating heat pipe by arranging the bidirectional self-excited pulsating heat pipe in the composite phase change material storage / release wall and connecting the combined cooling system, thereby improving the heat release capacity of the composite phase change material storage / release wall at night and the heat storage capacity during the day, solving the problem of insufficient regeneration rate of the phase change material wall in the cooling season, and the problem of low energy efficiency of the multi-effect composite passive cooling building system in 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 so that the gas-liquid two-phase has a stable circulation transport path, and has excellent temperature uniformity performance; improves the number of hydrogel evaporation cores and the evaporative cooling intensity, and increases the hydrogel The contact area with the surrounding environment improves the rewetting ability of the hydrogel nanoparticles; 3. The present invention also solves the problems of weak heat dissipation capacity of the existing phase change material storage / release wall enclosure structure, weak regeneration capacity in the cooling season and low energy-saving efficiency. During the cooling season, the heat on the sunny side of the south wall is transferred to the roof through a two-way self-excited pulsating heat pipe during the day and dissipated through hydrogel evaporative cooling, or transferred to the shady side of the north wall for storage. At night, the residual heat in the wall is extracted through the combined action of hydrogel evaporative cooling and radiation cooling to complete the regeneration cycle of the phase change material storage / release wall, and the two-way self-excited pulsating heat pipe will automatically stop working when the ambient temperature drops to prevent the phenomenon of indoor heat dissipation in winter, thereby reducing the air-conditioning load required for the building; 4. The system integrates technologies such as pulsating heat pipes, radiation cooling, hydrogel evaporative heat dissipation and phase change energy storage, and is suitable for zero-consumption (or near-zero energy consumption) green energy-saving buildings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a three-dimensional structural schematic diagram of a zero-energy building thermal management system of the present invention that uses a bidirectional pulsating heat pipe in conjunction with a phase change material; Figure 2 for Figure 1 Sectional view of the composite phase change material energy storage / release wall on the south side of the middle AA section; Figure 3 for Figure 1 Sectional view of the composite phase change material energy storage / release wall on the north side of the middle section B; Figure 4 for Figure 1 Schematic diagram of the three-dimensional structure of the bidirectional self-excited pulsating heat pipe; Figure 5 for Figure 1 Front view of the combined cooling system of sky radiation and porous gel evaporation; Figure 6 for Figure 1 Side view of the combined cooling system of mid-sky radiation and porous gel evaporation; Figure 7 for Figure 1 Cross-sectional view of porous gel evaporative cooling structure in the middle CC section; Figure 8 for Figure 5 The local enlarged schematic diagram of point D in the middle; Fig. 9 This is a schematic diagram of heat transfer of the thermal management system of this embodiment under high heat load in extreme weather; Fig.10 This is a schematic diagram of heat transfer of the thermal management system of this embodiment under normal heat load; In the figure: 1. Composite phase change material storage / release wall on the south side; 2. Bidirectional self-excited pulsating heat pipe; 3. Combined cooling system; 4. Composite phase change material storage / release wall on the north side; 501. Concrete exterior wall on the south side; 502. Concrete exterior wall on the north side; 601. Aluminum plate on the south side; 602. Aluminum plate on the north side; 701. Phase change material plate on the south side; 702. Phase change material plate on the north side; 801. Evaporation section of bidirectional self-excited pulsating heat pipe on the south wall; 80 2. North wall bidirectional self-excited pulsating heat pipe evaporation section body; 901. South wall Tesla valve; 902. North wall Tesla valve; 10. Sintered capillary wick; 11. Cooling section body; 12. Insulating sealing plate; 13. Radiant cooling plate; 1301. Hydrophobic material coating; 1302. Atmospheric window coating; 14. Porous gel evaporative cooling structure; 1401. Multi-skeleton foam metal; 1402. Super absorbent gel; 15. Steam recovery chamber. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be noted that the directions or positional relationships indicated by terms such as "middle", "upper", "lower", "left", "right", "inside" and "outside" are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0022] Combination Figure 1 to Figure 7 As shown, a zero-energy building thermal management system of a bidirectional pulsating heat pipe in cooperation with a phase change material comprises a composite phase change material storage / release wall (specifically, a south-side composite phase change material storage / release wall 1 and a north-side composite phase change material storage / release wall 4), and a bidirectional self-excited pulsating heat pipe 2 connected to the composite phase change material storage / release wall; the bidirectional self-excited pulsating heat pipe 2 comprises a connected evaporation section pipe body (specifically, a south-wall bidirectional self-excited pulsating heat pipe evaporation section pipe body 801 and a north-wall bidirectional self-excited pulsating heat pipe evaporation section pipe body 802) and a cooling The evaporation section pipe body 11 is provided with a Tesla valve structure and is embedded in the composite phase change material energy storage / release wall. The cooling section pipe body 11 is arranged in a joint cooling system above the building. The joint cooling system includes a porous gel evaporation cooling structure 14 and a radiation 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 radiation cooling plate 13. The cooling section pipe body 11 is embedded in the porous gel evaporation cooling structure 14.

[0023] The zero-energy building thermal management system of the bidirectional pulsating heat pipe and phase change material is capable of improving the working efficiency of the bidirectional self-excited pulsating heat pipe 2 by arranging the bidirectional self-excited pulsating heat pipe 2 in the composite phase change material storage / release wall and connecting the combined cooling system, thereby improving the heat release capacity of the composite phase change material storage / release wall at night and the heat storage capacity during the day, solving the problem of insufficient regeneration rate of the phase change material wall in the cooling season and the problem of too low energy efficiency of the multi-effect composite passive cooling building system in the cooling season.

[0024] The composite phase change material energy storage / release wall can effectively isolate external heat and maintain the indoor temperature of the building near the human body comfort temperature when the ambient temperature exceeds the human body comfort temperature during the day. The bidirectional self-excited pulsating heat pipe uses its evaporation section pipe body to exchange heat with the phase change material in the composite phase change material energy storage / release wall, and its cooling section pipe body can exchange heat with the porous gel evaporative cooling structure in the combined cooling system.

[0025] The bidirectional self-excited pulsating heat pipe 2 can utilize the difference in solar radiation intensity between the south sunny side and the north sun-shielding side of the building during the day to form a corresponding pressure difference in the gas working medium embedded in the south evaporation section and the north evaporation section to drive the internal working medium to work passively. Under the joint action of the cooling section pipe body of the sky radiation and porous gel evaporation combined cooling system embedded in the roof, the passive working 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 pipe body and, through the characteristics of its one-way valve, enable the internal working medium of the bidirectional self-excited pulsating heat pipe to work while the gas plug is locally oscillating. When the heat is dissipated, the temperature difference between the north and south walls can be balanced. In the extreme case of insufficient heat dissipation capacity of the sky radiation and porous gel evaporation combined cooling system during extremely hot daytime weather, the heat on the sunny side of the south wall can be brought to the sun-proof side of the north wall through the working fluid circulation and absorbed by the composite phase change material storage / release wall of the north wall, thereby improving the applied heat storage value of the composite phase change material storage / release wall on the north and south sides and the actual utilization rate of the phase change material.

[0026] In the combined cooling system, the radiation cooling plate 13 can pass through the "atmospheric window" to exchange radiation heat with space to achieve a cooling effect below the atmospheric temperature, providing a cold source support for the bidirectional self-excited pulsating heat pipe 2. The porous gel evaporative cooling structure 14 can make up for the problem of insufficient cooling under the heat dissipation structure of a single radiation cooling plate, and enable the cooling section pipe body 11 of the bidirectional self-excited pulsating heat pipe to maintain a low temperature for continuous heat transfer.

[0027] The present invention improves the internal pressure difference of the bidirectional self-excited pulsating heat pipe through the above-mentioned special structure, enhances the driving force of the bidirectional self-excited pulsating heat pipe working medium, strengthens the phase change process of the working medium so that the gas-liquid two-phase has a stable circulation transportation path, and has excellent temperature uniformity performance; improves the number of hydrogel evaporation cores and the evaporative cooling intensity, increases the contact area between the hydrogel and the surrounding environment, and improves the rewetting ability of the hydrogel nanoparticles; the present invention also solves the problem that the existing phase change material storage / release wall enclosure structure has weak heat dissipation capacity, weak regeneration capacity in the cooling season, and low energy-saving efficiency. During the daytime in the cooling season, the bidirectional self-excited pulsating heat pipe is used to heat the surrounding wall. The heat on the sunny side of the south wall is transferred to the roof for dissipation through hydrogel evaporative cooling, or transferred to the shady side of the north wall for storage. At night, the residual heat in the wall is extracted through the combined action of hydrogel evaporative cooling and radiant cooling to complete the regeneration cycle of the phase change material storage / release wall. The two-way self-excited pulsating heat pipe will automatically stop working when the ambient temperature drops to prevent indoor heat dissipation in winter, reducing the air conditioning load required for the building. This system combines pulsating heat pipes, radiant cooling, hydrogel evaporative heat dissipation and phase change energy storage technologies, and is suitable for zero-consumption (or near-zero-energy) green energy-saving buildings.

[0028] Furthermore, the composite phase change material energy storage / release wall includes at least a south wall and a north wall, and the south wall and the north wall both 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) arranged in the concrete exterior walls, and aluminum plates (south aluminum plate 601 and north aluminum plate 602) are also arranged between the phase change material plates and the concrete exterior walls; the evaporation section pipe body is respectively embedded in the phase change material plates of the south wall and the north wall.

[0029] Specifically, the north phase change material storage / release wall includes a north concrete outer wall 502, a north aluminum plate 602, a north phase change material plate 702, a north wall bidirectional self-excited pulsating heat pipe evaporation section pipe body 802, and a north wall Tesla valve 902. The north concrete outer wall 502 provides external structural support, and the north phase change material plate 702 is encapsulated by the north aluminum plate 602 on the outside, and the north aluminum plate 602 provides sealing requirements for the phase change material. Solar radiation is absorbed and stored by the north phase change material plate 702, and is exported to the cooling section pipe body 11 of the roof bidirectional self-excited pulsating heat pipe through the north wall bidirectional self-excited pulsating heat pipe evaporation section pipe body 802. During the heat export process, the north wall Tesla valve 902 increases the heat absorption area of ​​the north wall bidirectional self-excited pulsating heat pipe evaporation section pipe body 802 and forms a stable circulation while the internal working fluid oscillates locally through the characteristics of its one-way valve.

[0030] The south phase change material storage / release wall and the north phase change material storage / release wall have the same physical structure, but have functional differences due to differences in the distribution of solar radiation during actual operation. The north wall side that is sheltered from the sun receives low solar radiation, so the north phase change material plate 702 absorbs low heat and has a low melting rate. The south wall side that is facing the sun receives high solar radiation, so the south phase change material plate 701 absorbs high heat and has a high melting rate. During the day, solar radiation is absorbed by the south phase change material plate 701 and the north phase change material plate 702, and the heat is transferred to the cooling section of the two-way self-excited pulsating heat pipe 11 through the south wall two-way self-excited pulsating heat pipe evaporation section pipe body 801 and the north wall two-way self-excited pulsating heat pipe evaporation section pipe body 802, and dissipated through the sky radiation and porous gel evaporation combined cooling system 3 as shown in FIG. Fig. 9As shown. The south wall Tesla valve 901 and the north wall Tesla valve 902 can use the characteristics of the one-way valve to make the working medium inside the two-way self-excited pulsating heat pipe 2 form a circulation of the south wall-roof-north wall-south wall while locally oscillating. When the ambient temperature and solar radiation rise, 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 side phase change material plate 701 and conducted through the south wall two-way self-excited pulsating heat pipe evaporation section pipe body 801, and the working medium circulation formed by the south wall Tesla valve 901 and the north wall Tesla valve 902 is conducted to the north side phase change material plate 702 for absorption.

[0031] Furthermore, the evaporation section tube body is respectively provided at both ends of the cooling section tube body 11, and the three are connected to form a double-end three-dimensional semi-frame structure; the evaporation section tube body includes at least two U-shaped tube sections, and the outer sides of the U-shaped tube sections are respectively connected to the Tesla valve structures.

[0032] Specifically, the bidirectional self-excited pulsating heat pipe includes a connected south wall bidirectional self-excited pulsating heat pipe evaporation section tube body 801, a roof cooling section tube body 11, and a north wall bidirectional self-excited pulsating heat pipe evaporation section tube body 802, wherein the south wall bidirectional self-excited pulsating heat pipe evaporation section tube body 801 is embedded in the south side composite phase change material storage / release wall 1, the north wall bidirectional self-excited pulsating heat pipe evaporation section tube body 802 is embedded in the north side composite phase change material storage / release wall 4, the roof cooling section tube body 11 is embedded in the sky radiation and porous gel evaporation combined cooling system 3, the south wall bidirectional self-excited pulsating heat pipe evaporation section tube body 801 includes a plurality of parallel and spaced evaporation tube bundles, 4 of which are shown in the figure, that is, the bidirectional self-excited pulsating heat pipe 2 can undergo various changes according to different building sizes in actual use, and the number of tube bundles of the north wall bidirectional self-excited pulsating heat pipe evaporation section tube body 802 and the roof cooling section tube body 11 changes accordingly with the requirements of the building structure.

[0033] Furthermore, a sintered capillary core 10 is formed on the inner wall of the evaporation section tube body. The inner walls of the south wall bidirectional self-excited pulsating heat pipe evaporation section tube body 801 and the north wall bidirectional self-excited pulsating heat pipe evaporation section tube body 802 are both formed with a sintered capillary core 10. 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 body.

[0034] Furthermore, the phase change material plate is at least composed of a mixture of paraffin, lauric acid, stearic acid and hydrated sodium sulfate, and the phase change temperature of the phase change material plate is 25±2°C.

[0035] The bidirectional self-excited pulsating heat pipe is made of nano-copper and has an integrated tubular structure with an outer diameter of 3mm and an inner diameter of 2mm and a liquid injection port. A low-boiling point mixed working fluid is injected into the interior. In this embodiment, the low-boiling point mixed working fluid is mainly composed of acetone and is added with 0.1wt% of graphene oxide and a surfactant by mass fraction. The overall filling rate of the low-boiling point mixed working fluid is not less than 60%, and before the low-boiling point mixed working fluid is injected into the bidirectional self-excited pulsating heat pipe, the air pressure in the tube is ensured to be lower than 2kPa, that is, the air pressure in the tube is pumped below 2kPa and then the low-boiling point working fluid with a volume fraction of 60% is injected, and then the liquid injection port is sealed.

[0036] Before the low-boiling-point mixed working fluid is injected, the air pressure in the bidirectional self-excited pulsating heat pipe is reduced to below 2 kPa, which can reduce the internal acetone working fluid saturation temperature to 24°C. When the environment enters the cooling season and the outside temperature exceeds the human comfort temperature of 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 stop working autonomously to prevent the loss of heat inside the building during the heating season. The internal working fluid saturation temperature is lower than the phase change temperature of the composite phase change material, which can ensure that when the composite phase change material is in a melted state, the bidirectional self-excited pulsating heat pipe can be driven to automatically work until the composite phase change material solidifies and regenerates.

[0037] Furthermore, the porous gel evaporative cooling structure 14 is an upper opening box structure, the radiation cooling plate 13 is installed at the upper opening, and the bottom and side surfaces of the porous gel evaporative cooling structure 14 are also covered with an insulating sealing plate 12. An atmospheric window coating 1302 is provided above the radiation cooling plate 13, and a plurality of arc-shaped condensation drainage fin structures are provided below the radiation cooling plate 13, and a hydrophobic material coating 1301 is provided on the arc-shaped condensation drainage fin structure.

[0038] Specifically, the insulating sealing plate 12 wraps the side and bottom of the combined cooling system 3, and the side has an embedded opening for the cooling section of the bidirectional self-excited pulsating heat pipe. The radiation cooling plate 13 is made of aluminum and has the atmospheric window coating 1302 on the top. The bottom is made into an arc-shaped condensation drainage rib shape and is provided with a hydrophobic material coating 1301. The porous gel evaporative cooling structure 14 is concave and arranged on the side and bottom of the sky radiation and porous gel evaporative combined cooling system 3 structure. The side is connected to the top radiation cooling plate 13, and the space between the concave part and the radiation cooling plate 13 forms a steam recovery chamber 15. Preferably, the atmospheric window coating 1302 adopts ZS-411 material, which has a strong emissivity in the medium and long wave band of 8~13μm, and can achieve a cooling effect below the atmospheric temperature through the "atmospheric window" for radiation heat exchange with space, thereby providing a cold source support for the bidirectional self-excited pulsating heat pipe. Making an arc-shaped condensation drainage fin structure on the back of the radiation cooling plate and laying a hydrophobic coating can increase the heat exchange area while promoting the timely reflux of gas condensate in the steam chamber to the porous gel evaporative cooling structure to complete steam recovery.

[0039] Further, combined with Figure 8 As shown, the porous gel evaporative cooling structure 14 is composed of a multi-skeleton metal foam 1401 embedded with a super absorbent gel 1402. The multi-skeleton metal foam 1401 is made of nano copper, and the super absorbent gel 1402 is made of low-crosslinked sodium acrylate, and sodium chloride solution is used as the basic solution of the low-crosslinked sodium acrylate.

[0040] The porous gel evaporative cooling structure 14 embeds low-crosslinked sodium acrylate with multi-skeleton foam metal, and uses sodium chloride solution as the basic solution of low-crosslinked sodium acrylate to improve the water absorption and rewetting properties of the low-crosslinked sodium acrylate hydrogel. The multi-skeleton foam metal made of nano copper is embedded in the low-crosslinked sodium acrylate hydrogel material as the thermal conductive skeleton of the hydrogel to improve the thermal conductivity and specific surface area of ​​the overall structure. The evaporation enthalpy of water of 2450 J / g is used to provide the heat dissipation performance of the structure. The porous gel evaporative cooling structure 14 can make up for the problem of insufficient cooling under the heat dissipation structure of a single radiation cooling plate, and enable the cooling section of the bidirectional self-excited pulsating heat pipe to remain at a low temperature for continuous heat transfer.

[0041] The working principle of this zero-energy building thermal management system using bidirectional pulsating heat pipes and phase change materials is as follows: The high latent heat value of phase change materials can absorb and store the solar radiation absorbed by the building walls during the day to reduce the indoor energy usage rate. During the day, the solar radiation power received by the south sunny side and the north sun-shielded side of the building is several times different. The bidirectional self-excited pulsating heat pipes are arranged on the evaporation section of the north and south walls. The pressure difference will be formed under the natural solar radiation power difference, thereby driving the working fluid in the bidirectional self-excited pulsating heat pipe to operate passively. Under the action of the Tesla valve structure, the internal working fluid is driven to form a stable circulation under the condition of local oscillation to ensure that the heat can be transported to the The cooling section of the bidirectional self-excited pulsating heat pipe dissipates heat in time, and efficient evaporative cooling is achieved by adsorbing liquid water molecules through super absorbent gel combined with the thermal conductivity and specific surface area of ​​the multi-skeleton foam metal reinforcement structure. At night, radiation cooling at absolute zero is achieved through the sky radiation cooling plate made of ZS-411 coating, while condensation and recovery of water vapor are achieved. Both provide cold source support for the bidirectional self-excited pulsating heat pipe, increase the air pressure difference in the pipe, enhance the driving force of the working fluid, and timely export the heat stored in the phase change material wall and complete the condensation and regeneration of the phase change material at night.

[0042] A working process of the zero-energy building thermal management system of the bidirectional pulsating heat pipe and phase change material is as follows: (1) Conventional thermal radiation working process during the day Combination Fig.10As shown, the south composite phase change material storage / release wall 1 absorbs heat under the irradiation of sunlight during the day, and the north composite phase change material storage / release wall 4 absorbs heat under the action of diffuse light during the day, wherein the heat energy is absorbed and stored by the south phase change material plate 701 and the north phase change material plate 702. After reaching the phase change temperature, the south phase change material plate 701 and the north phase change material plate 702 change from solid phase to liquid phase. At this time, the phase change material that continues to absorb heat will continue to heat up. When the temperature exceeds 24°C, a pressure difference is formed in the working medium vaporization pipe in the south wall bidirectional self-excited pulsating heat pipe evaporation section pipe body 801 or the north wall bidirectional self-excited pulsating heat pipe evaporation section pipe body 802. Due to the large difference in solar radiation intensity in the north and south directions, the radiation heat flux density received by the south sunny side is 800~1000w / ㎡, while the diffuse light radiation heat flux density on the north inverse sun side is about 150w / ㎡. This high power difference will increase the pressure difference in the south wall two-way self-excited pulsating heat pipe evaporation section tube body 801 and the north wall two-way self-excited pulsating heat pipe evaporation section tube body 802, providing additional driving force for the working medium. Under the joint action of the characteristics of the one-way valves of the south wall Tesla valve 901 and the north wall Tesla valve 902 and the difference in heat flux density of the double evaporation sections, the working medium inside the two-way self-excited pulsating heat pipe 2 forms a stable circulation. The circulation can ensure that the liquid working medium forms the south wall two-way self-excited pulsating heat pipe evaporation section tube body 801 → the cooling section tube body 11 of the two-way self-excited pulsating heat pipe → the north wall two-way self-excited pulsating heat pipe evaporation section tube body 802 → the cooling section tube body 1 of the two-way self-excited pulsating heat pipe 1→stable flow path of the bidirectional self-excited pulsating heat pipe evaporation section tube body 801 on the south wall, the circulation can ensure that the working fluid brings heat from the bidirectional self-excited pulsating heat pipe evaporation section tube body to the cooling section tube body for dissipation. During the day, the solar radiation energy received by the roof is concentrated in the high-frequency band, and the radiation cooling plate 13 in the sky radiation and porous gel evaporation combined cooling system 3 reduces the absorption of high-frequency light waves through the ZS-411 material used in the atmospheric window coating 1302 and increases the release of low-frequency infrared light waves. The radiation cooling effect is achieved by the atmospheric window. Because it is unavoidable to absorb part of the solar radiation band, 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 porous gel evaporation cooling structure 14 The water molecules around the cooling section tube body 11 of the bidirectional self-excited pulsating heat pipe embedded on the bottom side absorb the heat brought from the evaporation section tube body 801 of the south wall bidirectional self-excited pulsating heat pipe and the evaporation section tube body 802 of the north wall bidirectional self-excited pulsating heat pipe, and then vaporize and dissipate into the steam recovery chamber 15. The gel around the tube loses water and becomes dry. The super absorbent gel in the porous gel evaporative cooling structure 14 uses its ultra-high water absorption and the osmotic pressure difference of the water molecules around the tube 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, taking away the heat absorbed from the south side composite phase change material storage / energy release wall 1 and the north side composite phase change material storage / energy release wall 4, and solving the problem of low energy saving effect of traditional phase change material storage / energy release walls in the cooling season through heat dissipation.

[0043] (2) Working process in extreme weather with high heat radiation during the day Combination Fig. 9 As shown, under extremely high temperatures in summer, the high heat flux density of the south wall causes the south phase change material plate 701 to liquefy, driving the working medium in the heat absorption pipe of the evaporation section of the south wall two-way self-excited pulsating heat pipe 801 to vaporize, and the two-way self-excited pulsating heat pipe 2 starts to work. The circulation formed by the south wall Tesla valve 901 and the north wall Tesla valve 902 check valve brings the heat to the cooling section of the two-way self-excited pulsating heat pipe 11, which is absorbed by the sky radiation and porous gel evaporation combined cooling system 3. However, the extreme conditions cause the evaporation section of the south wall two-way self-excited pulsating heat pipe to The working medium temperature in the heat absorbing pipe 801 is too high, and the cooling load of the sky radiation and porous gel evaporation combined cooling system 3 is too heavy. At this time, the heat that cannot be dissipated will continue to be stored in the high-temperature working medium in the two-way self-excited pulsating heat pipe 2 and reach the north wall two-way self-excited pulsating heat pipe evaporation section pipe body 802 with the circulation. At this time, the working medium temperature inside the north wall two-way self-excited pulsating heat pipe evaporation section pipe body 802 is higher than the temperature of the north side phase change material plate 702 in the north side composite phase change material storage / release wall 4, and the heat is absorbed and stored by the north side phase change material plate 702. The north side stores the heat of the south side, improves the overall phase change material utilization rate of the building, and thus achieves the purpose of delaying the indoor temperature rise time and reducing indoor energy consumption in extreme weather.

[0044] (3) Night operation mode At night, since the phase change temperature of the prepared 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 in the absence of solar radiation at night, and bring the energy stored during the day to the sky radiation and porous gel evaporation combined cooling system 3 through the working fluid circulation for dissipation. The outer side of the south composite phase change material storage / release wall 1 and the north composite phase change material storage / release wall 4 dissipates the energy stored in the composite phase change material through convection heat exchange with the natural environment, and the inner side dissipates the energy stored in the composite phase change material through the bidirectional self-excited pulsating heat pipe 2, thereby improving the solidification regeneration efficiency of the phase change material and solving the problem of low regeneration rate of the traditional phase change material storage / release wall. Since there is no solar radiation at night, the cooling effect of the radiation cooling plate 13 will be improved, and water vapor condensation recovery will be achieved under the joint action of the lower arc-shaped condensation drainage fins and the hydrophobic material coating 1301.

[0045] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A zero-energy building thermal management system using a bidirectional pulsating heat pipe and phase change materials, characterized in that: It includes a composite phase change material storage / release wall, and a bidirectional self-excited pulsating heat pipe connected to the composite phase change material storage / release wall; the bidirectional self-excited pulsating heat pipe includes an evaporation section pipe body and a cooling section pipe body that are connected, the evaporation section pipe body is provided with a Tesla valve structure and is embedded in the composite phase change material storage / release wall, the cooling section pipe body is arranged in a joint cooling system above a building, the joint cooling system includes a porous gel evaporative cooling structure, and a radiation cooling plate connected to the porous gel evaporative cooling structure, a steam recovery chamber is provided between the porous gel evaporative cooling structure and the radiation cooling plate, and the cooling section pipe body is embedded in the porous gel evaporative cooling structure.

2. The zero-energy building thermal management system of bidirectional pulsating heat pipe and phase change material according to claim 1 is characterized in that: 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 exterior wall and a phase change material plate arranged in the concrete exterior wall, and an aluminum plate is also arranged between the phase change material plate and the concrete exterior wall; the evaporation section pipe body is respectively embedded in the phase change material plates of the south wall and the north wall.

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

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

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

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

7. The zero-energy building thermal management system of bidirectional pulsating heat pipe and phase change material according to claim 1 is characterized in that: The porous gel evaporative cooling structure is a box structure with an upper opening, the radiation cooling plate is installed at the upper opening, and the bottom and side surfaces of the porous gel evaporative cooling structure are also covered with a heat insulating sealing plate.

8. The zero-energy building thermal management system of bidirectional pulsating heat pipe and phase change material according to claim 1 is characterized in that: An atmospheric window coating is arranged above the radiation cooling plate, and a plurality of arc-shaped condensation drainage fin structures are arranged below the radiation cooling plate. A hydrophobic material coating is arranged on the arc-shaped condensation drainage fin structures.

9. The zero-energy building thermal management system of bidirectional pulsating heat pipe and phase change material according to claim 1 is characterized in that: The porous gel evaporative cooling structure is composed of a multi-skeleton foam metal embedded with a super absorbent gel. The multi-skeleton foam metal uses nano copper as a manufacturing material, and the super absorbent gel uses low-crosslinked sodium acrylate as a material, and sodium chloride solution is used as a basic solution of the low-crosslinked sodium acrylate.

10. The zero-energy building thermal management system of bidirectional pulsating heat pipe and phase change material according to claim 1 is characterized in that: There are at least three operating modes: Conventional heat radiation mode during the day: the composite phase change material storage / release wall on the south side absorbs heat under the irradiation of sunlight during the day, and the composite phase change material storage / release wall on the north side absorbs heat under the action of diffuse light during the day. When the temperature exceeds 24°C, a pressure difference is formed in the working medium gasification pipe in the evaporation section pipe body on the south and north sides, and the working medium forms a stable circulation from the evaporation section pipe body on the south side, the cooling section pipe body, the evaporation section pipe body on the north side, the cooling section pipe body to the evaporation section pipe body on the south side. The stable circulation ensures that the working medium brings heat from the evaporation section pipe body to the cooling section pipe body for dissipation; Radiation mode of hot weather during the day: Under high temperature conditions, the phase change material plate in the composite phase change material storage / release wall on the south side liquefies and drives the evaporation section pipe body on the south side to absorb heat, the working fluid in the pipe vaporizes, and the bidirectional self-excited pulsating heat pipe starts to work to bring heat to the cooling section pipe body to be absorbed by the combined cooling system; at this time, the heat that cannot be dissipated will continue to be stored in the high-temperature working fluid in the bidirectional self-excited pulsating heat pipe and reach the evaporation section pipe body on the north side with the circulation. The working fluid temperature inside the evaporation section pipe body 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, and the heat is absorbed and stored by the phase change material plate on the north side; Night 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. The liquid phase change material in the composite phase change material storage / energy release wall on the south side and the composite phase change material storage / energy release wall on the north side drives the bidirectional self-excited pulsating heat pipe to continue working in the absence of solar radiation at night, and brings the energy stored during the day to the combined cooling system for dissipation through the working fluid circulation. The composite phase change material storage / energy release wall on the south side and the composite phase change material storage / energy release wall on the north side dissipate the energy stored in the composite phase change material through convection heat exchange with the natural environment on the outside, and the energy stored in the composite phase change material is dissipated inside through the bidirectional self-excited pulsating heat pipe.

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