Flexible anti-evaporation unpowered cooling film system capable of being automatically folded and unfolded

Abstract

The invention discloses a flexible anti-evaporation unpowered cooling film system capable of being automatically retracted and released, and aims to solve the problems that an artificial reservoir or a water channel is large in water storage area and large in water evaporation capacity. According to the unpowered cooling film system capable of being automatically retracted and released, two rotary drum frames, a sleeve and a guide roller are installed on a floating plate, an unpowered cooling composite film is wound around the sleeve, two parallel guide rails are arranged on the side face of the floating plate, a first limiting block and a second limiting block are arranged on the guide rails, and each sliding block is arranged on a lead screw in a sleeving mode to form a lead screw pair; the sliding blocks are in sliding connection with the guide rails, and the free end of the unpowered cooling composite film is fixed to the two sliding blocks. According to the unpowered cooling film system capable of being automatically folded and unfolded, the base film is subjected to dip-coating treatment to form a composite coating, the weather resistance of the unpowered cooling film is improved, the unpowered cooling composite film is unfolded through the unfolding mechanism, when the sun directly irradiates the water surface, the unpowered cooling composite film can achieve cooling to the maximum extent, and the service life of the unpowered cooling film is prolonged. Water evaporation is prevented.

Description

Technical Field

[0001] The invention relates to a flexible evaporation-proof and automatically retractable unpowered temperature-reducing film device. Background Art

[0002] Reservoirs are large-scale water projects built artificially to store and regulate water resources. Reservoirs can receive, absorb and delay the peak flow of rivers, reduce the threat of floods in rivers, and regulate the flow of floods by releasing them. Reservoirs can store water sources such as rainwater and river water for urban, agricultural and industrial use. They can provide a stable water supply during dry seasons or water shortages. Reservoirs use the kinetic energy of water flow to convert into electrical energy through hydropower generation technology. Reservoir power generation is a form of renewable energy that can provide a stable power supply for the power grid. The water source of the reservoir can be used to irrigate farmland, provide the amount of water required for crops, improve agricultural production conditions, and increase agricultural output. Reservoirs can provide a rich water ecological environment, providing habitats and food sources for fish, birds and other organisms. They can also be used for wetland protection and ecosystem restoration. However, artificial reservoirs have a large water storage area and evaporate a lot of water, which will cause a lot of water resource waste. For example, based on the average area of ​​20 square kilometers of the reservoir, the average annual evaporation can reach more than 2 meters, and some areas have insufficient precipitation, resulting in serious water resource waste. Summary of the invention

[0003] The purpose of the present invention is to solve the problem of large water storage area and large water evaporation in artificial reservoirs or canals, and to provide a flexible anti-evaporation and automatically retractable unpowered cooling membrane system.

[0004] The flexible anti-evaporation and automatically retractable non-powered cooling film system of the present invention comprises a floating plate, a rotating drum frame, a sleeve, a non-powered cooling composite film, a guide roller and a spreading mechanism, two rotating drum frames and a guide roller are mounted on the upper surface of the floating plate, the two rotating drum frames are arranged opposite to each other, a sleeve is rotatably connected between the two rotating drum frames, the sleeve is driven to rotate by a first motor, and the non-powered cooling composite film is wound on the sleeve;

[0005] The spreading mechanism comprises two guide rails, a first limit block, a second limit block, two sliders, two screw rods and a belt. The two parallel guide rails are arranged on the side of the floating plate. The first limit block is arranged on the side of the guide rail adjacent to the floating plate, and the second limit block is arranged on the side of the guide rail away from the floating plate. The two ends of each screw rod are respectively sleeved in the bearings of the first limit block and the second limit block. The two screw rods are synchronously driven by the belt, one of which is driven to rotate by the second motor, each slider is sleeved on the screw rod to form a screw pair, and the slider is slidably connected to the guide rail;

[0006] The free end of the unpowered cooling composite film is fixed on two slide blocks via guide rollers;

[0007] The preparation method of the non-powered cooling composite membrane is achieved by the following steps:

[0008] Step 1: Prepare SiO2-coated TiO2 particles by liquid phase deposition method;

[0009] Step 2: dissolving polyurethane in DMF solvent to obtain polyurethane sol, dispersing SiO2-coated TiO2 particles in DMF solvent to obtain TiO2 suspension; adding the TiO2 suspension to the polyurethane sol under stirring, stirring evenly, to obtain a first coating;

[0010] Step 3, immersing the base film in the first coating for dip coating, taking out the base film and drying and curing it to obtain a base film with a first coating;

[0011] Step 4: Add nano-silica particles, SiO2-coated TiO2 particles, polydimethylsiloxane and a curing agent into an ethyl acetate solvent, and stir to react for 2 to 4 hours to obtain a second coating;

[0012] Step 5: Immerse the base film with the first coating into the second coating for dip coating, take out the base film, dry and solidify it, and obtain a non-powered cooling composite film.

[0013] The non-powered cooling composite film of the present invention forms a first coating and a second coating on a base film, wherein the first coating contains SiO2 coated TiO2 particles and polyurethane, TiO2 has a high refractive index, has a strong scattering effect on light, and can absorb ultraviolet radiation to protect polymers, and the TiO2 particles improve the dispersibility of TiO2 nanomaterials after being coated with SiO2, and reduce the photocatalytic activity of the TiO2 particles, while the polyurethane has a low thermal conductivity and good heat insulation performance, and the light aging resistance and heat aging resistance of the composite film are improved by the first coating. The nano silicon dioxide particles and polydimethylsiloxane in the second coating have a high emissivity, play a role in radiation cooling, optimize the ratio of nano silicon dioxide particles and SiO2 coated TiO2 particles, improve weather resistance, and the SiO2 particles improve the nano rough structure of the coating surface, and the polydimethylsiloxane has good hydrophobicity and wear resistance, and the composite film has super hydrophobicity and self-cleaning performance by the second coating.

[0014] The flexible anti-evaporation and automatically retractable non-powered cooling film system of the present invention mainly includes a floating plate, a non-powered cooling composite film and a spreading mechanism. The drum frame and the sleeve are installed on the floating plate, and the non-powered cooling composite film is wound on the sleeve. The non-powered cooling composite film is unfolded by the spreading mechanism. When the sun shines directly on the water surface, the non-powered cooling composite film can achieve cooling to the greatest extent and prevent water evaporation; when the sensor senses that there are continuous raindrops falling, the spreading mechanism can also roll up and recycle the film. When the sensor senses that the rain stops, the non-powered cooling film can be released again to cover the water surface. The non-powered cooling composite film can effectively prevent the evaporation of water in the reservoir. At the same time, the high light transmittance can ensure the supply of sunlight, and the automatic retraction function can realize the process of collecting precipitation. The system has low energy consumption and excellent water-saving effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the flexible anti-evaporation automatically retractable and unpowered cooling membrane system of the present invention.

[0016] Figure 2 It is a schematic diagram of the top view of the support frame and the sleeve;

[0017] Figure 3 It is a schematic diagram of the top view of the spreading mechanism. DETAILED DESCRIPTION

[0018] Specific implementation method 1: The flexible anti-evaporation and automatically retractable non-powered cooling film system of this implementation method comprises a floating plate 1, a drum frame 2, a sleeve 3, a non-powered cooling composite film 4, a guide roller 5 and a spreading mechanism, two drum frames 2 and guide rollers 5 are mounted on the upper surface of the floating plate 1, two drum frames 2 are arranged opposite to each other, and a sleeve 3 is rotatably connected between the two drum frames 2, the sleeve 3 is driven to rotate by a first motor 13, and the non-powered cooling composite film 4 is wound on the sleeve 3;

[0019] The spreading mechanism includes two guide rails 10, a first limit block 6, a second limit block 8, two sliders 7, two screw rods 9 and a belt 11. The two parallel guide rails 10 are arranged on the side of the floating plate 1. The first limit block 6 is arranged on the side of the guide rail 10 adjacent to the floating plate 1, and the second limit block 8 is arranged on the side of the guide rail 10 away from the floating plate 1. The two ends of each screw rod 9 are respectively sleeved in the bearings of the first limit block 6 and the second limit block 8. The two screw rods 9 are synchronously driven by the belt 11, and one of the screw rods 9 is driven to rotate by the second motor 12. Each slider 7 is sleeved on the screw rod 9 to form a screw pair, and the slider 7 is slidably connected to the guide rail 10;

[0020] The free end of the unpowered cooling composite film 4 is fixed on two sliders 7 via a guide roller 5;

[0021] The preparation method of the non-powered cooling composite membrane is achieved by the following steps:

[0022] Step 1: Prepare SiO2-coated TiO2 particles by liquid phase deposition method;

[0023] Step 2: dissolving polyurethane in DMF solvent to obtain polyurethane sol, dispersing SiO2-coated TiO2 particles in DMF solvent to obtain TiO2 suspension; adding the TiO2 suspension to the polyurethane sol under stirring, stirring evenly, to obtain a first coating;

[0024] Step 3, immersing the base film in the first coating for dip coating, taking out the base film and drying and curing it to obtain a base film with a first coating;

[0025] Step 4: Add nano-silica particles, SiO2-coated TiO2 particles, polydimethylsiloxane and a curing agent into an ethyl acetate solvent, and stir to react for 2 to 4 hours to obtain a second coating;

[0026] Step 5: Immerse the base film with the first coating into the second coating for dip coating, take out the base film, dry and solidify it, and obtain a non-powered cooling composite film.

[0027] The method for preparing SiO2-coated TiO2 particles by liquid phase deposition in this embodiment is as follows:

[0028] TiO2 particles are added into deionized water, polyethylene glycol active agent and dispersant are added, and the TiO2 suspension is obtained by high-speed stirring. The solution containing Na2SiO3 is added while continuing to stir, and the pH of the system is adjusted to 4 by sulfuric acid. After stirring and reacting, the system is aged, and SiO2-coated TiO2 particles are obtained after washing and drying.

[0029] The flexible anti-evaporation automatically retractable unpowered cooling membrane system of this embodiment can effectively prevent evaporation on the surface of water bodies such as reservoirs and canals, has the effect of saving water, has the characteristics of low energy consumption, and a high degree of automation.

[0030] The flexible anti-evaporation and automatically retractable non-powered cooling membrane system of this embodiment is also equipped with a controller and a variety of sensors, which detect the external environment through pressure sensing, temperature sensing, light sensing and other sensors to ensure normal water collection function, ensure the water exchange function of the reservoir, etc. The non-powered cooling membrane system can reduce more than 1 / 2 of solar radiation and water evaporation, and has excellent water-saving performance.

[0031] The flexible anti-evaporation automatically retractable unpowered cooling membrane system of this embodiment can be arranged on the water surface of a canal, a river or a reservoir.

[0032] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that a buoy or a buoyancy box is provided on the floating plate 1 .

[0033] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that a travel switch is provided on the first limit block 6 and the second limit block 8 respectively.

[0034] In this embodiment, when the slider contacts the travel switches on the first limit block 6 and the second limit block 8, the operation of the second motor can be turned off.

[0035] Specific embodiment 4: This embodiment is different from specific embodiments 1 to 3 in that a solar panel 14 and a battery 15 are also provided on the floating plate 1 , the solar panel 14 is electrically connected to the battery 15 , and the battery 15 supplies power to the first motor 13 and the second motor 12 .

[0036] Specific embodiment 5: This embodiment is different from specific embodiments 1 to 4 in that a temperature sensor and a light intensity sensor are further provided on the floating plate 1 .

[0037] This embodiment can also detect rainfall conditions on the shore and control the operation of the spreading mechanism through remote communication equipment.

[0038] Specific embodiment 6: This embodiment is different from specific embodiments 1 to 5 in that in step 2 of the method for preparing the unpowered cooling composite film, the first coating contains 3wt% to 8wt% of SiO2-coated TiO2 particles.

[0039] Specific embodiment seven: This embodiment differs from any one of specific embodiments one to six in that the base film described in step three of the method for preparing the unpowered cooling composite film is a polymethyl methacrylate film, a polycarbonate film, a polyethylene film or a polypropylene film.

[0040] Specific embodiment eight: The difference between this embodiment and any one of specific embodiments one to seven is that in step four of the method for preparing the unpowered cooling composite membrane, the mass ratio of nano-silica particles, SiO2-coated TiO2 particles and polydimethylsiloxane is (5-8):1:(10-20).

[0041] Specific embodiment 9: This embodiment is different from any one of specific embodiments 1 to 8 in that in step 4 of the method for preparing the composite membrane without powered cooling, the reaction is stirred at 30 to 35° C. for 2.5 to 3.5 hours.

[0042] Specific embodiment ten: This embodiment differs from specific embodiments one to nine in that in step five of the method for preparing the unpowered cooling composite membrane, the base film with the first coating is immersed in the second coating for a dipping treatment time of 10 to 30 minutes.

[0043] Specific embodiment eleven: This embodiment differs from specific embodiments one to ten in that in step five of the method for preparing the non-powered cooling composite membrane, the drying and curing treatment is performed at 60-80° C. for 1-2 hours.

[0044] Specific embodiment 12: The difference between this embodiment and specific embodiments 1 to 11 is that in step 5 of the method for preparing the unpowered cooling composite membrane, the unpowered cooling composite membrane is immersed in the second coating again for dipping treatment and drying and curing treatment, and the dipping treatment and drying and curing treatment are repeated multiple times.

[0045] In this embodiment, the dipping process is repeated multiple times to increase the coating thickness. The coating thickness on the unpowered cooling composite film is preferably 80 to 200 nm.

[0046] Embodiment 1: The flexible anti-evaporation and automatically retractable non-powered cooling film system of this embodiment comprises a floating plate 1, a rotating drum frame 2, a sleeve 3, a non-powered cooling composite film 4, a guide roller 5 and a spreading mechanism, two rotating drum frames 2, guide rollers 5, a solar panel 14 and a battery 15 are installed on the upper surface of the floating plate 1, the solar panel 14 is electrically connected to the battery 15, the battery 15 supplies power to the first motor 13 and the second motor 12, a buoy is provided on the floating plate 1, the floating plate 1 and the guide rail 10 in the spreading mechanism float on the water surface, the two rotating drum frames 2 are arranged opposite to each other, the sleeve 3 is rotatably connected between the two rotating drum frames 2, the sleeve 3 is driven to rotate by the first motor 13, and the non-powered cooling composite film 4 is wound on the sleeve 3;

[0047] The spreading mechanism includes two guide rails 10, a first limit block 6, a second limit block 8, two sliders 7, two screw rods 9 and a belt 11. The two parallel guide rails 10 are arranged on the side of the floating plate 1 by bolts. The first limit block 6 is arranged on the side of the guide rail 10 adjacent to the floating plate 1, and the second limit block 8 is arranged on the side of the guide rail 10 away from the floating plate 1. The first limit block 6 and the second limit block 8 are horizontally placed between the two guide rails 10. The two ends of each screw rod 9 are respectively sleeved in the bearings of the first limit block 6 and the second limit block 8. The two screw rods 9 are synchronously driven by the belt 11, and one of the screw rods 9 is driven to rotate by the second motor 12. Each slider 7 is sleeved on the screw rod 9 to form a screw pair, and the slider 7 is slidably connected to the guide rail 10.

[0048] A reinforcement strip is arranged on the free end of the non-powered cooling composite film 4, and the non-powered cooling composite film 4 is plugged into two sliders 7 via the guide roller 5, and the first limit block 6 and the second limit block 8 are respectively provided with travel switches;

[0049] The preparation method of the non-powered cooling composite membrane is achieved by the following steps:

[0050] Step 1: Add 2 g of TiO2 particles into deionized water, add 1 g of polyethylene glycol active agent and 0.05 g of (NaPO3)6 dispersant, stir at high speed to obtain a TiO2 suspension, continue stirring and add a solution containing 0.24 g of Na2SiO3, adjust the pH of the system to 4 with sulfuric acid, stir the reaction and age for 10 hours, and obtain SiO2-coated TiO2 particles after washing and drying;

[0051] Step 2, dissolving polyurethane in DMF solvent to obtain polyurethane sol, dispersing SiO2-coated TiO2 particles in DMF solvent to obtain TiO2 suspension; adding the TiO2 suspension to the polyurethane sol under stirring, stirring evenly, to obtain a first coating, wherein the first coating contains 5wt% of SiO2-coated TiO2 particles;

[0052] Step 3, immersing the polymethyl methacrylate base film in the first coating for 30 minutes, taking out the base film, drying (drying temperature is 80° C.) and curing for 2 hours, and then immersing it in the first coating for immersion and curing again to obtain a base film with a first coating;

[0053] Step 4: Add nano-silica particles, SiO2-coated TiO2 particles, polydimethylsiloxane and a curing agent into an ethyl acetate solvent in a mass ratio of 6:1:15:1, and stir and react at 30° C. for 2.5 hours to obtain a second coating;

[0054] Step 5: Immerse the base film with the first coating into the second coating for 20 minutes, take out the base film, dry it (drying temperature is 80°C) and cure it for 2 hours, repeat the immersion in the second coating and the curing treatment to obtain a non-powered cooling composite film with a composite coating thickness of 120nm.

[0055] The unpowered cooling composite film prepared in this embodiment has high light transmittance and will not affect the impact of light changes on underwater organisms.

[0056] The process of spreading the unpowered cooling film using the flexible anti-evaporation and automatically retractable unpowered cooling film system is as follows:

[0057] When the water surface temperature is high as detected by the remote controller (wireless communication equipment) or the sensor, the second motor 12 starts, the two screw rods 9 are synchronously driven by the belt 11, and the slider 7 on the screw rod 9 drives the unpowered cooling composite film 4 to move toward the second limit block 8 to realize the spreading of the unpowered cooling composite film 4; when the ambient temperature is low or it rains, the second motor 12 drives in the reverse direction, and the slider 7 on the screw rod 9 drives the unpowered cooling composite film 4 to move toward the first limit block 6, and then the first motor 13 starts to rewind and recover the unpowered cooling composite film 4.

[0058] Comparative Example: The preparation method of the comparative cooling film is implemented according to the following steps:

[0059] a. Add nano-silica particles, TiO2 particles (not coated with SiO2), polydimethylsiloxane and curing agent into ethyl acetate solvent in a mass ratio of 6:1:15:1, and stir the mixture at 30°C for 2.5 hours to obtain a coating;

[0060] b. The base film was immersed in the coating for 20 minutes, and the base film was taken out and dried (the drying temperature was 80° C.) and cured for 2 hours to obtain a comparative cooling film.

[0061] The wettability of the unpowered cooling composite membrane obtained in Example 1 was tested using deionized water droplets, and the static contact angle of the water droplets was 163°, achieving super hydrophobicity.

[0062] For the cooling performance test, a metal plate was set under the unpowered cooling composite membrane with an insulating sponge under it. The temperature of the metal plate was tested from 10:00 to 14:00 on a sunny day in summer, and a metal plate without direct sunlight was used as a comparison. During this period, under direct sunlight, the maximum temperature of the metal plate was about 60°C. Under the shielding condition of the unpowered cooling composite membrane, the maximum temperature of the metal plate was 43°C. During the entire testing phase, the unpowered cooling composite membrane was able to maintain a cooling capacity of 13 to 17°C.

[0063] The weather resistance test includes UV resistance experiment and heat aging resistance experiment. The UV resistance experiment uses UV lamp to continuously irradiate the non-powered cooling composite film for 10 days, and then conducts the cooling performance test again. The non-powered cooling composite film can still maintain a cooling capacity of 11 to 14°C, while the comparison cooling film only has a cooling capacity of 4 to 7°C.

[0064] The heat aging test is carried out in a drying box at a cycle of 60℃ / 12h-25℃ / 12h for 5 days. The non-powered cooling composite film can maintain a cooling capacity of 12-15℃, while the comparative cooling film has a cooling capacity of 5-9℃.

[0065] The flexible evaporation-proof automatically retractable non-powered cooling membrane system described in the embodiment was installed on the surface of the reservoir, and the anti-evaporation performance of the flexible evaporation-proof automatically retractable non-powered cooling membrane system was tested. As shown in Table 1, Example a in the following table adopts the flexible evaporation-proof automatically retractable non-powered cooling membrane system in Example 1, and Comparative Example a is that the flexible evaporation-proof automatically retractable non-powered cooling membrane system is not arranged on the reservoir; Comparative Example b is that the polymethyl methacrylate base film is used to replace the non-powered cooling composite membrane; Comparative Example c is that the comparative cooling membrane is used to replace the non-powered cooling composite membrane.

[0066] Table 1. Performance of the unpowered cooling membrane in each embodiment and comparative example (calculated based on 20 square kilometers of water surface)

[0067] Example Annual evaporation (mm) Solar radiation reduction (%) Water level increase (mm) Embodiment a 350 60 450 Comparative Example a 2350 0 -1520 Comparative Example b 1640 12 -1440 Comparative Example c 380 53 -150 。

Claims

1. Flexible anti-evaporation, automatically retractable and unpowered cooling film system, characterized by The flexible anti-evaporation and automatically retractable non-powered cooling film system comprises a floating plate (1), a rotating drum frame (2), a sleeve (3), a non-powered cooling composite film (4), a guide roller (5) and a spreading mechanism, wherein two rotating drum frames (2) and the guide roller (5) are mounted on the upper surface of the floating plate (1), the two rotating drum frames (2) are arranged opposite to each other, and a sleeve (3) is rotatably connected between the two rotating drum frames (2), the sleeve (3) is driven to rotate by a first motor (13), and the non-powered cooling composite film (4) is wound on the sleeve (3); The spreading mechanism comprises two guide rails (10), a first limit block (6), a second limit block (8), two sliders (7), two screw rods (9) and a belt (11); the two parallel guide rails (10) are arranged on the side of the floating plate (1); the first limit block (6) is arranged on the side of the guide rail (10) adjacent to the floating plate (1); the second limit block (8) is arranged on the side of the guide rail (10) away from the floating plate (1); the two ends of each screw rod (9) are respectively sleeved in the bearings of the first limit block (6) and the second limit block (8); the two screw rods (9) are synchronously driven by the belt (11); one of the screw rods (9) is driven to rotate by the second motor (12); each slider (7) is sleeved on the screw rod (9) to form a screw pair; the slider (7) is slidably connected to the guide rail (10); The free end of the unpowered cooling composite film (4) is fixed on two slide blocks (7) via a guide roller (5); The preparation method of the non-powered cooling composite membrane is achieved by the following steps: Step 1: Prepare SiO2-coated TiO2 particles by liquid phase deposition method; Step 2: dissolving polyurethane in DMF solvent to obtain polyurethane sol, dispersing SiO2-coated TiO2 particles in DMF solvent to obtain TiO2 suspension; adding the TiO2 suspension to the polyurethane sol under stirring, stirring evenly, to obtain a first coating; Step 3, immersing the base film in the first coating for dip coating, taking out the base film and drying and curing it to obtain a base film with a first coating; Step 4: Add nano-silica particles, SiO2-coated TiO2 particles, polydimethylsiloxane and a curing agent into an ethyl acetate solvent, and stir to react for 2 to 4 hours to obtain a second coating; Step 5: Immerse the base film with the first coating into the second coating for dip coating, take out the base film, dry and solidify it, and obtain a non-powered cooling composite film.

2. The flexible anti-evaporation automatically retractable unpowered cooling film system according to claim 1 is characterized in that A buoy or a buoyancy box is arranged on the floating plate (1).

3. The flexible anti-evaporation automatically retractable unpowered cooling film system according to claim 1 is characterized in that Travel switches are respectively arranged on the first limit block (6) and the second limit block (8).

4. The flexible anti-evaporation automatically retractable unpowered cooling film system according to claim 1 is characterized in that A solar panel (14) and a storage battery (15) are also provided on the floating plate (1). The solar panel (14) is electrically connected to the storage battery (15), and the storage battery (15) supplies power to the first motor (13) and the second motor (12).

5. The flexible anti-evaporation automatically retractable unpowered cooling film system according to claim 1 is characterized in that A temperature sensor and a light intensity sensor are also arranged on the floating plate (1).

6. The flexible anti-evaporation automatically retractable unpowered cooling film system according to claim 1 is characterized in that In step 2 of the method for preparing the unpowered cooling composite film, the first coating contains 3 wt % to 8 wt % of SiO 2 coated TiO 2 particles.

7. The flexible anti-evaporation automatically retractable unpowered cooling film system according to claim 1 is characterized in that The base film described in step 3 of the method for preparing the unpowered cooling composite film is a polymethyl methacrylate film, a polycarbonate film, a polyethylene film or a polypropylene film.

8. The flexible anti-evaporation automatically retractable unpowered cooling film system according to claim 1 is characterized in that In step 4 of the method for preparing the unpowered cooling composite membrane, the mass ratio of nano-silica particles, SiO2-coated TiO2 particles and polydimethylsiloxane is (5-8):1:(10-20).

9. The flexible anti-evaporation automatically retractable unpowered cooling film system according to claim 1 is characterized in that In step 5 of the method for preparing the unpowered cooling composite membrane, the base membrane with the first coating is immersed in the second coating for a dipping treatment time of 4 to 10 minutes.

10. The flexible anti-evaporation automatically retractable unpowered cooling film system according to claim 1 is characterized in that In step 5 of the method for preparing the non-powered cooling composite membrane, the membrane is dried and cured at 60-80° C. for 1-2 hours.

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