An adaptive evaporative cooling passive evaporative cooler and a method of making the same

Abstract

The application discloses a self-adaptive evaporative cooling passive evaporative cooler and a preparation method thereof. The self-adaptive evaporative cooling passive evaporative cooler comprises, from bottom to top, a temperature-sensitive hydrogel layer, a perforated film layer with hydrophobicity and a porous structure layer with hydrophilicity. The self-adaptive evaporative cooling passive evaporative cooler has good cooling effect at high temperature, can inhibit evaporative cooling at low temperature, and can show different cooling capacities according to different temperatures.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cooling materials, in particular to a passive evaporative cooler with adaptive evaporative cooling and a preparation method thereof. BACKGROUND

[0002] In recent years, environmental problems such as climate change and global warming have become increasingly serious. More than 95% of global warming is likely to be caused by human activities. In the process of human activities, a large amount of carbon dioxide, methane, nitrous oxide and other gases are emitted, leading to global warming. Among them, carbon dioxide is the main contributor to global warming. It is worth noting that the carbon emissions of the refrigeration industry account for about 7.8% of the total global greenhouse gas emissions, which has brought great pressure to the ecological balance.

[0003] Common cooling technologies include semiconductor cooling, compression cooling, and adiabatic cooling. In the context of growing global cooling demand, passive evaporative cooling without power consumption has become an ideal solution. Recently, different evaporative cooling materials such as porous materials and superabsorbent polymers have been developed. The evaporative cooling capacity of the materials is continuously improved. However, in some areas, due to the alternation of day and night, the environmental temperature changes rapidly, and cooling is only needed during the day. Unnecessary cooling at night will increase heating energy consumption and even offset the cooling energy saved during hot periods. SUMMARY

[0004] The present application aims to overcome the above technical deficiencies and provide a passive evaporative cooler with adaptive evaporative cooling and a preparation method thereof, which solves the technical problem that the cooling materials in the prior art have significant evaporative cooling at high and low temperatures, and cannot have different cooling capacities according to different temperatures.

[0005] In a first aspect, the present application provides a passive evaporative cooler with adaptive evaporative cooling, which comprises, from bottom to top, a temperature-sensitive hydrogel layer, a perforated film layer with hydrophobicity, and a porous structure layer with hydrophilicity.

[0006] In a second aspect, the present application provides a preparation method of a passive evaporative cooler with adaptive evaporative cooling, comprising the following steps:

[0007] providing a temperature-sensitive hydrogel layer and a perforated film layer with hydrophobicity;

[0008] providing a porous structure layer with hydrophilicity on the surface of the perforated film layer with hydrophobicity;

[0009] providing a temperature-sensitive hydrogel layer on the other surface of the perforated film layer with hydrophobicity away from the porous structure layer with hydrophilicity.

[0010] Compared with the prior art, the present application has the following advantages:

[0011] The passive evaporative cooler of adaptive evaporative cooling provided by the present application has good cooling effect at high temperature, and can inhibit evaporative cooling at low temperature, and can show different cooling capacity according to different temperatures. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a structural schematic diagram of an embodiment of the passive evaporative cooler of adaptive evaporative cooling (AECS) provided by the present application;

[0013] Figure 2 is a working principle diagram of the passive evaporative cooler of adaptive evaporative cooling (AECS) provided by the present application;

[0014] Figure 3 is a physical diagram of the passive evaporative cooler of adaptive evaporative cooling (AECS) prepared in embodiment 1 of the present application;

[0015] Figure 4 is an SEM diagram of the silicon dioxide porous membrane layer in the passive evaporative cooler of adaptive evaporative cooling (AECS) prepared in embodiment 1 of the present application;

[0016] Figure 5 is an SEM diagram of the PNIPAM hydrogel layer in the passive evaporative cooler of adaptive evaporative cooling (AECS) prepared in embodiment 1 of the present application;

[0017] Figure 6 is a DSC diagram of the PNIPAM hydrogel layer in the passive evaporative cooler of adaptive evaporative cooling (AECS) prepared in embodiment 1 of the present application;

[0018] Figure 7 is a schematic diagram of a cooling capacity test experimental device of the passive evaporative cooler of adaptive evaporative cooling (AECS) provided by the present application;

[0019] Figure 8 is an actual field test photo of the cooling capacity test experimental device of the passive evaporative cooler of adaptive evaporative cooling (AECS) provided by the present application;

[0020] Figure 9 is a full-day test curve diagram and temperature difference schematic diagram of the passive evaporative cooler of adaptive evaporative cooling (AECS) prepared in embodiment 1 of the present application;

[0021] Figure 10 is a cooling capacity comparison diagram of the passive evaporative cooler of adaptive evaporative cooling (AECS) prepared in embodiment 1 of the present application and ordinary superabsorbent polymer (SAP);

[0022] Figure 11is a cooling capacity comparison chart of passive evaporative coolers (AECS) of adaptive evaporative cooling of different structures in the present invention;

[0023] Figure 12 is a chart of the influence of different ambient temperature and humidity on the cooling capacity of passive evaporative coolers (AECS) of adaptive evaporative cooling in the present invention;

[0024] Figure 13 is a chart of the influence of different pore diameters on the cooling capacity of passive evaporative coolers (AECS) of adaptive evaporative cooling prepared in the present invention;

[0025] Figure 14 is a chart of the influence of different numbers of perforations on the cooling capacity of passive evaporative coolers (AECS) of adaptive evaporative cooling prepared in the present invention. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present invention and do not limit the present invention.

[0027] Please refer to Figure 1 , in a first aspect, the present invention provides a passive evaporative cooler of adaptive evaporative cooling, the structure of which comprises, from bottom to top, a temperature-sensitive hydrogel layer 1, a perforated film layer 2 with hydrophobicity, and a porous structure layer 3 with hydrophilicity.

[0028] The present invention selects the temperature-sensitive hydrogel layer 1 as the main material for adjusting the cooling capacity. Near the phase transition point, the temperature-sensitive hydrogel will undergo a hydrophilic / hydrophobic transition, thereby changing the evaporation rate of water.

[0029] The present invention selects the perforated film layer 2 with hydrophobicity as the intermediate layer, which utilizes its low permeability to steam and water. The perforated film with hydrophobicity is coated on the hydrogel, and the water adsorbed in the hydrogel at low temperature can only evaporate through the perforations on the perforated film with hydrophobicity, which greatly reduces the evaporation area and rate of water, thereby inhibiting the evaporative cooling capacity. At the same time, the inventors found in the test process that if the intermediate layer is set as a perforated film layer with hydrophilicity, the evaporative capacity at low temperature cannot be inhibited.

[0030] The present invention selects the porous structure layer 3 with hydrophilicity as the top material of the coating, which utilizes its good hydrophilicity and porosity to quickly diffuse the water permeated through the pores on the perforated film layer with hydrophobicity by capillary force, and ensures that water can cover the entire surface of the perforated film layer with hydrophobicity at high temperature, which ensures the utilization of water evaporation area and fully plays the evaporative cooling capacity.

[0031] In this embodiment, the phase transition temperature of the temperature-sensitive hydrogel layer 1 is 10-50°C, preferably 20-40°C.

[0032] In some embodiments of the present application, the temperature-sensitive hydrogel layer 1 is a PNIPAM (N-isopropyl acrylamide) hydrogel. The critical solution temperature (LCST) of the PNIPAM hydrogel is relatively low, and the LCST is about 32°C, close to the human body temperature. Near the phase transition point, the PNIPAM will undergo a hydrophilic / hydrophobic transition, thereby changing the evaporation rate of water.

[0033] In some more specific embodiments of the present application, the preparation method of the PNIPAM hydrogel comprises the following steps:

[0034] Purification of PNIPAM monomer: N-isopropyl acrylamide is mixed with n-hexane and stirred at 40-60°C until completely dissolved, then the stabilizer is removed, and then the solution after removing the stabilizer is placed in a freezer at -10-0°C, and left until the crystals are completely precipitated, then the crystallization solution mixture is suction filtered to obtain pure N-isopropyl acrylamide powder; in this process, the above operation is repeated several times to improve the purity of the obtained pure N-isopropyl acrylamide powder. Further, the amount ratio of N-isopropyl acrylamide to n-hexane is 1g:(20-100)mL; and the standing time is 3-6h each time.

[0035] Preparation of PNIPAM hydrogel: pure N-isopropyl acrylamide powder, acrylamide, ammonium persulfate and N,N,N',N'-tetramethyl ethylenediamine are mixed and dissolved in deionized water, then the obtained solution is poured into a container, sealed and left at room temperature until the hydrogel is formed, and finally immersed in hot water and cold water alternately to demold. In this process, the hydrogel will be demolded by its own volume change without manual intervention, and a clean PNIPAM thermal-responsive hydrogel can be obtained after several times of alternating hot and cold. Further, the amount ratio of pure N-isopropyl acrylamide powder to acrylamide, ammonium persulfate and N,N,N',N'-tetramethyl ethylenediamine is 1g:(10-200)mg:(1-50)mg:(1-50)μL, and further 1g:50mg:10mg:10μL; and the amount ratio of pure N-isopropyl acrylamide powder to water is 1g:(2-6)mL, and further 1g:3mL.

[0036] In this embodiment, the material of the perforated film layer 2 with hydrophobicity is PET (polyethylene terephthalate), PP (polypropylene) or PE (polyethylene).

[0037] In the hydrophobic perforated film layer 2, the number of perforations is proportional to the cooling effect, and the perforation diameter is inversely proportional to the cooling effect. The inventors found in experiments that the smaller the perforation diameter or the more the number of perforations, the shorter the water diffusion distance and the better the cooling capacity.

[0038] In some embodiments of the present application, the perforation diameter is about 2-5 mm, and the number of perforations is 3-6 per 25 cm 2 .

[0039] In the present embodiment, the material of the above-mentioned hydrophilic porous structure layer 3 is silica. The inventors found in the process of experiments that selecting silica as the material of the hydrophilic porous structure layer 3 is more conducive to improving the bonding force with the hydrophobic perforated film layer 2. Further, the silica particle size formed in the silica porous layer is 50-300 nm.

[0040] Please refer to Figure 2 , the mechanism of the present application will be described by taking the adaptive evaporative cooling passive evaporative cooler composed of a PNIPAM hydrogel layer, a perforated PET layer, and a silica porous layer as an example. In the case where the ambient temperature is higher or lower than the LCST of the PNIPAM hydrogel, the adaptive evaporative cooling passive evaporative cooler of the present application exhibits different cooling capacity. At low temperature (< LCST), the PNIPAM hydrogel is in a hydrophilic state, and most of the water is adsorbed in the hydrogel. In this case, the locked water has no flow capacity, and it can only evaporate through the holes of the PET film. The inhibited water evaporation process leads to poor cooling capacity of the AECS. When the temperature of the environment rises above the LCST, the hydrogel changes from a hydrophilic state to a hydrophobic state, and the adsorbed water will be discharged. The discharged free water can penetrate the PET holes and rapidly diffuse under the capillary action of the silica coating to cover the entire PET surface below. In this case, the discharged free water can evaporate from a larger area and has a faster evaporation rate, which leads to excellent cooling capacity.

[0041] In the present embodiment, the thickness of the temperature-sensitive hydrogel layer 1 accounts for 90-99% of the total thickness of the temperature-sensitive hydrogel layer 1, the hydrophobic perforated film layer 2, and the hydrophilic porous structure layer 3, the hydrophobic perforated film layer 2 accounts for 0.5-9% of the total thickness of the temperature-sensitive hydrogel layer 1, the hydrophobic perforated film layer 2, and the hydrophilic porous structure layer 3, and the hydrophilic porous structure layer 3 accounts for 0.5-2% of the total thickness of the temperature-sensitive hydrogel layer 1, the hydrophobic perforated film layer 2, and the hydrophilic porous structure layer 3.

[0042] Further, the thickness of the temperature-sensitive hydrogel layer 1 accounts for 93% to 97% of the total thickness of the temperature-sensitive hydrogel layer 1, the perforated film layer 2 with hydrophobicity, and the porous structure layer 3 with hydrophilicity, the thickness of the perforated film layer 2 with hydrophobicity accounts for 1% to 5% of the total thickness of the temperature-sensitive hydrogel layer 1, the perforated film layer 2 with hydrophobicity, and the porous structure layer 3 with hydrophilicity, and the thickness of the porous structure layer 3 with hydrophilicity accounts for 1% to 2% of the total thickness of the temperature-sensitive hydrogel layer 1, the perforated film layer 2 with hydrophobicity, and the porous structure layer 3 with hydrophilicity.

[0043] In the embodiment, the structure of the passive evaporative cooler with adaptive evaporative cooling further comprises a sealing layer, which is arranged at the bottom of the temperature-sensitive hydrogel layer 1 to seal the temperature-sensitive hydrogel layer 1 without significantly affecting the cooling capacity. The thickness of the sealing layer is not limited in the present application, and can be selected by those skilled in the art according to the actual situation. In some specific embodiments of the present application, the sealing layer is a non-porous PET layer.

[0044] In a second aspect, the present application provides a preparation method of a passive evaporative cooler with adaptive evaporative cooling, comprising the following steps:

[0045] providing a temperature-sensitive hydrogel layer 1 and a perforated film layer 2 with hydrophobicity;

[0046] arranging a porous structure layer 3 with hydrophilicity on the surface of the perforated film layer 2 with hydrophobicity;

[0047] arranging the temperature-sensitive hydrogel layer 1 on the other surface of the perforated film layer 2 with hydrophobicity away from the porous structure layer 3 with hydrophilicity.

[0048] The way of arranging the porous structure layer 3 with hydrophilicity on the surface of the perforated film layer 2 with hydrophobicity is not limited in the present application, and can be selected by those skilled in the art according to the actual situation, for example, screen printing, chemical vapor deposition, etc.

[0049] In some specific embodiments of the present application, the perforated film layer 2 with hydrophobicity is a perforated PET layer, the porous structure layer 3 with hydrophilicity is a porous silica layer, and the step of arranging the porous structure layer 3 with hydrophilicity on the surface of the perforated film layer 2 with hydrophobicity comprises:

[0050] S21, grinding silica and alcohol solvent to uniformity to obtain transparent silica slurry; wherein the alcohol solvent is anhydrous ethanol; the ratio of the amount of silica to alcohol solvent is 1g: (2-10) mL.

[0051] S22, the silica slurry is transferred to the surface of the perforated PET layer, and then hot-pressed to form a perforated PET layer with a silica porous layer on the surface. The hot-pressing pressure is 10-20 MPa, the hot-pressing temperature is 100-150℃, and the hot-pressing time is 5-20 min.

[0052] In the following embodiments of the present application, the size specifications of the passive evaporative cooler with adaptive evaporative cooling are as follows: length 5 cm, width 5 cm, and thickness about 3.2 mm.

[0053] Embodiment 1

[0054] The present embodiment provides a passive evaporative cooler with adaptive evaporative cooling and a preparation method thereof. The passive evaporative cooler with adaptive evaporative cooling comprises a PNIPAM hydrogel layer 1, a perforated PET layer 2, and a silica porous layer 3. The perforated PET layer 2 has a pore diameter of 4 mm, a pore spacing of 10 mm, and 5 pores.

[0055] The preparation method comprises the following steps:

[0056] (1) Purification of PNIPAM monomer: 1 g of N-isopropyl acrylamide is mixed with 40 mL of n-hexane, the mixture is stirred at 50-60℃ until completely dissolved, and the transparent solution is poured out without the yellow particles at the bottom; then, the solution is placed in a freezer at -10℃ to -0℃, and is left to stand for 4 hours until the crystals are completely precipitated. The crystalline solution mixture is suction filtered to obtain NIPAM powder; the above operation is repeated 3 times to obtain pure N-isopropyl acrylamide powder; after the residual solvent in the powder is evaporated, the powder can be bottled and stored in the refrigerator for future use.

[0057] (2) Preparation of PNIPAM hydrogel: 4 g of purified N-isopropyl acrylamide and 200 mg of acrylamide are mixed in 12 mL of deionized water (25℃), and are shaken vigorously for about 10 minutes until the powder is dissolved into a uniform solution; then, 40 mg of ammonium persulfate is added, and the shaking is continued for a few minutes; then, 40 μL of N,N,N',N'-tetramethyl ethylenediamine is added, and after shaking, the obtained solution is poured into a glass dish, sealed with a PE film, and left to stand at room temperature for 4 hours to form a hydrogel, which is finally alternately soaked in hot water (40℃) and cold water (20℃). During this process, the hydrogel will be demolded by its own volume change without manual intervention, and a clean PNIPAM thermoresponsive hydrogel can be obtained after three cycles of cold-hot alternation.

[0058] (3) Preparation of the porous silica membrane: 1 g of silica particles was mixed with 5 mL of absolute ethanol and ground in a mortar to homogeneity to obtain a transparent silica slurry; a 0.1 mm-thick PET film was punched to form holes with a diameter of 4 mm, a hole spacing of 10 mm, and a hole number of 5; the prepared silica slurry was transferred to the surface of the perforated PET film with a thickness of 0.1 mm using screen printing; then, the silica particle membrane was placed on the flat plate of a hot press, and pressed at a pressure of 15 MPa and a temperature of 120°C for 10 min, and naturally cooled to room temperature to obtain a flexible porous silica membrane (thickness of 40 μm).

[0059] (4) Preparation of the AECS structure sample: the porous silica membrane prepared in step (3) was placed on the upper layer, then the PNIPAM hydrogel with a thickness of 3 mm prepared in step (2) was placed under the porous silica membrane, and finally another non-perforated PET film was attached to the lower side of the PNIPAM hydrogel to seal the PNIPAM hydrogel, forming a complete AECS sample, as shown in Figure 3 .

[0060] To illustrate the cooling and refrigeration effect of the passive evaporative cooler prepared in this embodiment 1, the following takes the passive evaporative cooler field test effect as an example for illustration.

[0061] Test group 1

[0062] According to the preparation process of the porous silica membrane in step (3) in embodiment 1, it can be known that the surface of the perforated PET film is covered with a thin layer of transparent material, which is a layer of nano-silica particles. The prepared film was cut to an appropriate size for scanning electron microscope test. Figure 4 The scanning electron microscope image of its surface is shown in Figure 4 From

[0063] Test group 2

[0064] The PNIPAM hydrogel prepared in step (2) in embodiment 1 was placed on a non-perforated PET film, and the film was cut to an appropriate size for scanning electron microscope test. Figure 5 The scanning electron microscope image of its surface is shown in Figure 6 At the same time, the PNIPAM hydrogel was analyzed in a differential scanning calorimeter to obtain a phase transition temperature of 31°C~37°C, as shown in

[0065] Test group 3

[0066] The cooling capacity test of AECS was conducted from 7:30 to 18:00. The AECS sample was wrapped in a foam box, and the surface was covered with aluminum foil, as shown in Figure 7 . Since the test was conducted in winter, the ambient temperature could not reach the phase transition point of the hydrogel, and the change in cooling capacity of the AECS could not be observed. Therefore, we used another foam box covered with black cloth, and placed the AECS inside, as shown in Figure 8 .

[0067] As can be seen from Figure 9 , from 7:30 to 10:00, the T value of the AECS showed a slow upward trend due to the decrease in ambient humidity and the increase in ambient temperature. However, the ambient temperature was lower than the phase transition point of the hydrogel, resulting in a low evaporation rate of water in the AECS. The result was that the average T of the AECS was only about 1℃. After 10:00, as the ambient temperature increased and exceeded the phase transition point of the hydrogel, the evaporation rate of water in the AECS increased rapidly, resulting in a sharp increase in the T of the AECS, reaching a maximum of 12.3℃. From 10:30 to 15:30, the ambient temperature remained above 40℃, and the T of the AECS remained at an average of about 10.2℃. From 15:30 to 16:30, the ambient temperature gradually decreased and fell below the phase transition point of the hydrogel, and the T of the AECS decreased sharply. From 16:30 to 18:00, the ambient temperature was below 20℃, and the average T of the AECS was only about 1℃. The test results were consistent with the theoretical analysis, verifying that the AECS could automatically adjust its cooling capacity by changing the evaporation rate of water. During the entire heating and cooling process, when the same ambient temperature was reached, the temperature of the AECS during the heating process was significantly lower than that during the cooling process, which was due to the large sensible heat of water, resulting in a slow response of the temperature change of the AECS.

[0068] Test Group 4

[0069] The cooling performance comparison test of AECS with superabsorbent polymer (SAP) and ACES functional unit, the results are shown in Figure 10 and 11 .

[0070] From Figure 10It can be seen that when the ambient temperature is lower than 25℃, the cooling capacity of AECS is significantly lower than that of SAP, and the cooling capacity of AECS is less than 20% of that of SAP. As the ambient temperature exceeds the phase transition point of PNIPAM hydrogel, the cooling capacity of AECS increases rapidly. When the ambient temperature is 45℃, the cooling capacity of AECS is close to 10℃, reaching 90% of the cooling capacity of SAP. At low temperature, the perforated PET film in AECS greatly reduces the evaporation area of the hydrogel, resulting in a huge difference in cooling capacity between AECS and SAP. After the ambient temperature reaches the phase transition point, the infiltrated water rapidly spreads to the entire surface through the silica coating, and the evaporation area of AECS rapidly increases, so that the cooling capacity of AECS and SAP is comparable.

[0071] In addition, through comparative experiments, we demonstrate the functions of the functional units of ACES. From Figure 11 It can be seen that a single PNIPAM hydrogel has a cooling capacity of close to 4℃ at low temperature, and the addition of a layer of perforated PET on the surface of the hydrogel can suppress the cooling capacity to below 1℃. However, the perforated PET film also suppresses the cooling capacity of the system at high temperature. Due to the poor hydrophilicity of PET, the infiltrated water cannot spread to the entire surface, resulting in poor high-temperature cooling capacity of the system, only about 4℃. The porous silica layer with hydrophilicity can effectively solve this problem. This coating can quickly spread the infiltrated water, reduce the adverse effects of PET perforation on the high-temperature cooling capacity of AECS, and increase the high-temperature cooling capacity to 5-6℃ without affecting the low-temperature cooling capacity.

[0072] Test group 5

[0073] The cooling capacity of AECS is also affected by environmental conditions. We have verified the effects of ambient temperature and relative humidity on the cooling effect of AECS at the same wind speed (the wind speed is fixed at 0.8m / s). As Figure 12 shown, when the relative humidity is fixed, the cooling capacity of AECS increases with the increase of ambient temperature. The increase of ambient temperature increases the diffusion rate of water molecules, thereby increasing the cooling capacity of AECS. When the ambient temperature is fixed, the cooling capacity of AECS decreases with the increase of ambient humidity. The increase of ambient relative humidity reduces the driving force of water evaporation, resulting in a decrease in the cooling capacity of AECS.

[0074] Example 2

[0075] The cooling capacity of AECS is related to the aperture of the perforation. Under the condition that the total area of the perforation is constant, holes with aperture of 2mm, 3mm, 4mm and 4.5mm are punched on the AECS respectively. As Figure 13 shown, the smaller the aperture, the better the cooling capacity of AECS at high temperature.

[0076] Example 3

[0077] The cooling capacity of the AECS is also related to the number of perforations. The AECS is punched with holes of 4mm in diameter, and the number of holes is 3, 4, 5, and 6, respectively. As shown in the table, the more holes, the better the cooling capacity of the AECS at high temperature. Figure 14

[0078] As can be seen from Example 2 and Example 3, the smaller the perforation diameter, the more the number of holes, the shorter the water diffusion distance, and the better the cooling capacity.

[0079] Compared with the prior art, the present application also has the following beneficial effects:

[0080] ① The passive evaporative cooler of the present application has the ability to exhibit different cooling effects according to different temperatures. Since the phase transition point of PNIPAM is fixed, the adjustment of the cooling capacity of AECS in response to temperature is also fixed, which limits the application range of AECS, but different concentrations of ion monomers can be added to change the phase transition point of PNIPAM hydrogel (for example, the amount of acrylamide added is different, and the phase transition point of the hydrogel is also different, acrylamide can be 32-45℃, and acrylic acid and propanol can also be used to control the phase transition point of the hydrogel) to control different cooling capacities, thereby solving the problem of different cooling capacities in different environments and further expanding the application range of the cooler.

[0081] ② The silica nanoparticles in the AECS have a relatively high evaporation speed at high temperature within 30-500nm, and the water permeated into the PET layer hole is quickly diffused by capillary force, and the water can cover the entire PET surface at high temperature, which improves the cooling capacity at high temperature compared with the pure non-porous PET film.

[0082] ③ The cooler of the present application has a small driving force for water evaporation in high humidity areas, resulting in insufficient cooling capacity of the AECS, but the AECS can be used in combination with a humidity generator. When the environmental humidity is high, the humidity generator helps to increase the output voltage and reduce the environmental humidity to promote evaporative cooling, thereby playing a synergistic role.

[0083] The specific embodiments of the present application described above do not constitute a limitation on the scope of protection of the present application. Any other corresponding changes and modifications made in accordance with the technical concept of the present application shall be included in the scope of protection of the claims of the present application.​

Claims

1. A self-adapting evaporative cooling passive evaporative cooler, characterized in that, The structure of the passive evaporative cooler of the adaptive evaporative cooling comprises, from bottom to top, a temperature-sensitive hydrogel layer, a hydrophobic perforated film layer, and a hydrophilic porous structure layer; the perforations in the hydrophobic perforated film layer are through holes.

2. The self-adaptive evaporative cooling passive evaporative cooler according to claim 1, wherein, The phase transition temperature of the temperature-sensitive hydrogel layer is 10-50℃.

3. The self- adaptive evaporative cooling passive evaporative cooler according to claim 1, wherein, The temperature-sensitive hydrogel layer is a PNIPAM hydrogel; the material of the hydrophobic perforated film layer is PET, PP, or PE; and the material of the hydrophilic porous structure layer is silicon dioxide.

4. The self- adaptive evaporative cooling passive evaporative cooler of claim 1, wherein, The temperature-sensitive hydrogel layer is a PNIPAM hydrogel, and the preparation method of the PNIPAM hydrogel comprises the following steps: Purification of PNIPAM monomers: N-isopropyl acrylamide is mixed with n-hexane and stirred at 40-60℃ until completely dissolved, then the stabilizer is removed, and the solution after removing the stabilizer is placed in a freezer at -10-0℃, and left to stand until the crystals completely precipitate, then the crystallization solution mixture is suction filtered to obtain pure N-isopropyl acrylamide powder; Preparation of the PNIPAM hydrogel: pure N-isopropyl acrylamide powder, acrylamide, ammonium persulfate, and N,N,N',N'-tetramethyl ethylenediamine are mixed and dissolved in deionized water, then the obtained solution is poured into a container, sealed, and left to stand at room temperature until a hydrogel is formed, and finally soaked in hot water and cold water alternately for demolding.

5. The self- adaptive evaporative cooling passive evaporative cooler according to claim 1, wherein, The perforated film layer with hydrophobicity has a perforation diameter of 2-5 mm and a number of perforations of 3-6 per 25 cm 2 .

6. The self- adaptive evaporative cooling passive evaporative cooler of claim 1, wherein, The thickness of the temperature-sensitive hydrogel layer accounts for 90-99% of the total thickness of the temperature-sensitive hydrogel layer, the hydrophobic perforated film layer, and the hydrophilic porous structure layer; the thickness of the hydrophobic perforated film layer accounts for 0.5-9% of the total thickness of the temperature-sensitive hydrogel layer, the hydrophobic perforated film layer, and the hydrophilic porous structure layer; and the thickness of the hydrophilic porous structure layer accounts for 0.5-2% of the total thickness of the temperature-sensitive hydrogel layer, the hydrophobic perforated film layer, and the hydrophilic porous structure layer.

7. The self- adaptive evaporative cooling passive evaporative cooler according to claim 1, wherein, The structure of the passive evaporative cooler of the adaptive evaporative cooling further comprises a sealing layer; the sealing layer is arranged at the bottom of the temperature-sensitive hydrogel layer to seal the temperature-sensitive hydrogel layer.

8. The self- adaptive evaporative cooling passive evaporative cooler according to claim 7, wherein, The sealing layer is a non-porous PET layer.

9. A method of making a self-adapting evaporative cooling passive evaporative cooler according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: providing a temperature-sensitive hydrogel layer and a hydrophobic perforated film layer; arranging the hydrophilic porous structure layer on the surface of the hydrophobic perforated film layer; arranging the temperature-sensitive hydrogel layer on the other surface of the hydrophobic perforated film layer away from the hydrophilic porous structure layer.

10. The method of claim 9, wherein the passive evaporative cooler is an adaptive evaporative cooler. The hydrophobic perforated film layer is a perforated PET layer, the hydrophilic porous structure layer is a silicon dioxide porous layer, and the step of arranging the hydrophilic porous structure layer on the surface of the hydrophobic perforated film layer comprises: mixing and grinding silicon dioxide with an alcohol solvent until uniform to obtain a transparent silicon dioxide slurry; transferring the silicon dioxide slurry to the surface of the perforated PET layer, then hot-pressing to form a perforated PET layer with a silicon dioxide porous layer arranged on the surface.

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