CN111879017B - Multi-lens solar heat collection device - Google Patents

Multi-lens solar heat collection device Download PDF

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CN111879017B
CN111879017B CN202010644689.7A CN202010644689A CN111879017B CN 111879017 B CN111879017 B CN 111879017B CN 202010644689 A CN202010644689 A CN 202010644689A CN 111879017 B CN111879017 B CN 111879017B
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water
photothermal conversion
water tank
graphene oxide
heat
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CN111879017A (en
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杜嘉
陈岩
杜文静
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Shandong University
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Shandong University
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
    • F24S23/30—Arrangements for concentrating solar-rays for solar heat collectors with lenses
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B1/00—Methods of steam generation characterised by form of heating method
    • F22B1/006—Methods of steam generation characterised by form of heating method using solar heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S70/00—Details of absorbing elements
    • F24S70/20—Details of absorbing elements characterised by absorbing coatings; characterised by surface treatment for increasing absorption
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S80/00—Details, accessories or component parts of solar heat collectors not provided for in groups F24S10/00-F24S70/00
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28B—STEAM OR VAPOUR CONDENSERS
    • F28B1/00—Condensers in which the steam or vapour is separate from the cooling medium by walls, e.g. surface condenser
    • F28B1/02—Condensers in which the steam or vapour is separate from the cooling medium by walls, e.g. surface condenser using water or other liquid as the cooling medium
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28B—STEAM OR VAPOUR CONDENSERS
    • F28B9/00—Auxiliary systems, arrangements, or devices
    • F28B9/08—Auxiliary systems, arrangements, or devices for collecting and removing condensate
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/40—Solar thermal energy, e.g. solar towers

Abstract

The invention provides a multi-lens solar heat collection device which comprises a water tank and a photothermal conversion element, wherein the upper end of the water tank is of an opening structure, the photothermal conversion element floats on the upper part of the water tank, a transparent glass cover is arranged on the upper part of the water tank and is of an arc-shaped structure, a steam delivery pipe is arranged at the top of the transparent glass cover, a plurality of convex lenses in an outward convex shape are arranged on the outer wall of the transparent glass cover and are uniformly distributed on the outer wall of the transparent glass cover, and the focuses of the convex lenses fall on a photothermal conversion coating so as to increase the absorption of solar energy. According to the invention, the plurality of convex lenses which are uniformly distributed are arranged on the outer wall of the transparent glass cover, so that solar energy can be better concentrated, the concentrated absorption of the solar energy is still ensured even if the position of the heat collecting device is changed, and the focus offset caused by the direction of the arranged position is avoided.

Description

Multi-lens solar heat collection device
Technical Field
The invention belongs to the field of solar energy, and particularly relates to a solar heat collector system.
Background
With the rapid development of modern socioeconomic, the demand of human beings on energy is increasing. However, the continuous decrease and shortage of traditional energy reserves such as coal, oil, natural gas and the like causes the continuous increase of price, and the environmental pollution problem caused by the conventional fossil fuel is more serious, which greatly limits the development of society and the improvement of the life quality of human beings. Energy problems have become one of the most prominent problems in the modern world. Therefore, the search for new energy sources, especially clean energy sources without pollution, has become a hot spot of research.
Solar energy is inexhaustible clean energy and has huge resource amount, and the total amount of solar radiation energy collected on the surface of the earth every year is 1 multiplied by 1018kW.h, which is ten thousand times of the total energy consumed in the world year. The utilization of solar energy has been used as an important item for the development of new energy in all countries of the world. However, due to solar radiation reaching the earthThe energy density is small (about one kilowatt per square meter) and is discontinuous, which brings certain difficulties for large-scale development and utilization. Therefore, in order to widely use solar energy, not only the technical problems should be solved, but also it is necessary to be economically competitive with conventional energy sources.
Aiming at the structure of a heat collector, the prior art has been researched and developed a lot, but the heat collecting capability is not enough on the whole, and the problem that the operation time is long and scaling is easy to happen, so that the heat collecting effect is influenced.
In any form and structure of solar collector, there is an absorption component for absorbing solar radiation, and the structure of the collector plays an important role in absorbing solar energy.
The heat pipe technology is widely applied to the industries of aerospace, military industry and the like, and since the heat pipe technology is introduced into the radiator manufacturing industry, the design idea of the traditional radiator is changed for people, the single heat radiation mode that a high-air-volume motor is used for obtaining a better heat radiation effect is avoided, the heat pipe technology is adopted for enabling the radiator to obtain a satisfactory heat exchange effect, and a new place in the heat radiation industry is opened up. At present, the heat pipe is widely applied to various heat exchange devices, including the fields of solar energy and seawater desalination, such as the utilization of solar energy.
The solar heat collecting device (application No. 201911353155.2) of the prior application achieves the purpose of generating steam and recovering the steam by arranging the glass cover, but the solar heat collecting device of the prior application has poor heat collecting effect, and particularly has the problem that the heat collecting part leaves the focus due to arrangement deviation. The invention provides a novel solar heat collecting device aiming at the problems. The device takes sunlight as a driving source, generates a large amount of steam without the assistance of a heating device, and the preparation method has the advantages of simple process, non-toxic and harmless raw materials and higher repeatability. The steam generating device can efficiently utilize solar energy to prepare solar steam, and has wide commercial value and application prospect in the fields of solar power generation, seawater desalination, sewage treatment and the like.
Disclosure of Invention
The invention provides a solar heat collecting device aiming at the defects in the prior art. The device uses sunlight as a driving source, a large amount of steam is generated without the assistance of a heating device, the floating foam material holds the photothermal conversion layer out of the water surface, and the dissipation of generated heat energy to lower-layer liquid through a film is inhibited, so that the steam efficiency of the device is improved, and the great potential of the device as a photothermal conversion new energy material is shown. The preparation method has simple process, nontoxic and harmless raw materials and higher repeatability. The steam generating device can efficiently utilize solar energy to prepare solar steam, and has wide commercial value and application prospect in the fields of solar power generation, seawater desalination, sewage treatment and the like.
In order to achieve the purpose, the invention adopts the following technical scheme:
the multi-lens solar heat collection device comprises a water tank and a light-heat conversion element, wherein the upper end of the water tank is of an open structure, and the light-heat conversion element floats in seawater on the upper portion of the water tank.
Preferably, the convex lens is polygonal in shape on the outer wall of the transparent glass cover.
Preferably, the photothermal conversion element comprises a matrix formed by a foaming material, a groove with an opening at the upper side is formed on the matrix, a foamed nickel matrix is filled in the groove, a capillary structure water delivery channel is arranged on the lower wall surface of the matrix, the water delivery channel is communicated with a water body of the water tank and the foamed nickel matrix, a photothermal conversion coating is arranged on the upper portion of the groove, the photothermal conversion coating is connected with the foamed nickel matrix, the buoyancy of the foaming material is greater than the gravity, and preferably, the upper surface of the photothermal conversion coating and the upper surface of the water body keep the same height or are not more than 5 cm higher than the upper surface of the water body.
Preferably, a transparent glass cover is arranged at the upper part of the water tank, the transparent glass cover is of a circular arc structure, the glass cover comprises a water collecting tank positioned on the lower side, the water collecting tank comprises an inner vertical side wall, a horizontal wall extending from the bottom end of the vertical side wall to the horizontal direction, an outer vertical wall extending upwards along the other end of the horizontal wall, and a circular arc structure extending upwards and inwards along the outer vertical wall, the water collecting tank is formed among the inner vertical wall, the horizontal wall and the outer vertical wall, and a water drainage hole is formed in the horizontal wall, so that fresh water collected by the water collecting tank is discharged, and the purpose of taking water out of seawater is achieved.
Preferably, the inner wall of the circular arc structure is provided with a diversion trench, so that the steam can flow into the water collection trench in time after being condensed.
Preferably, a steam outlet pipe is arranged at the top of the transparent glass cover and is connected with a cooling coil at the bottom of the water tank, steam is guided into the cooling coil to be cooled, water in the water tank is preheated by utilizing heat released by steam condensation, and the water is guided into the recovery device after the steam in the cooling coil is condensed into water.
Preferably, a plurality of convex lenses are arranged on the circular arc structure, and the focal points of the convex lenses are positioned on the photothermal conversion coating.
Preferably, the method for producing a photothermal conversion element includes the steps of:
(1) synthesis of reduced graphene oxide: adding 1000-3000mg of graphene oxide into 1000-3000mL of deionized water, respectively adding 750-9000 mg (with an interval of 250 mg) of ascorbic acid to obtain graphene dispersion, respectively stirring and performing ultrasonic treatment (preferably 40KHz, 240W) for 60 minutes in sequence, and reacting for 30 minutes at 2.45GHz, 200W and 95 ℃ by using a microwave reactor. Removing impurities on the upper layer of the obtained suspension, carrying out suction filtration, repeatedly washing with ultrapure water for three times, and carrying out vacuum freeze drying on a sample obtained by suction filtration to obtain reduced graphene oxide powder;
(2) preparing a photothermal conversion device: 1g of reduced graphene oxide (particle size 60nm) is dispersed by ultrasonic (preferably 40KHz, 240W) treatment to a volume ratio of 1000ml to 7: 1 in a mixed solution of water and ethanol. Agarose (12.5g) and urea (125g) were added to the solution and stirring was continued at 85 ℃ for 30 min. The resulting hot suspension was then applied evenly to the surface of the nickel foam. Naturally cooling the foam nickel matrix with the reduced graphene oxide coating, freezing the foam nickel matrix at-21 ℃, freeze-drying the foam nickel matrix in a refrigerator for 12 hours, and taking out the foam nickel matrix;
(3) preparation of the substrate 3: a common foaming material plate is taken and processed into a cylinder with the size suitable for the inner diameter of a beaker, and the preferred diameter is 20cm and the height is 10 cm.
The invention has the following advantages:
1. according to the invention, the plurality of convex lenses which are uniformly distributed are arranged on the outer wall of the transparent glass cover, so that solar energy can be better concentrated, the concentrated absorption of the solar energy is still ensured even if the position of the heat collecting device is changed, and the focus offset caused by the direction of the arranged position is avoided.
2. Aiming at the defects in the prior art, the invention provides a solar heat collection system. The device uses sunlight as a driving source, a large amount of steam is generated without the assistance of a heating device, the floating foam material holds the photothermal conversion layer out of the water surface, and the dissipation of generated heat energy to lower-layer liquid through a film is inhibited, so that the steam efficiency of the device is improved, and the great potential of the device as a photothermal conversion new energy material is shown. The preparation method has simple process, nontoxic and harmless raw materials and higher repeatability. The steam generating device can efficiently utilize solar energy to prepare solar steam, and has wide commercial value and application prospect in the fields of solar power generation, seawater desalination, sewage treatment and the like.
2. The invention provides a preparation method of a photothermal conversion piece, and the preparation method has the advantages of simple process, no toxicity and harm of raw materials and high repeatability.
3. In the photothermal conversion element of the present invention, since the photothermal conversion layer and the lower water body are separated by the heat insulating layer, heat loss caused by heat transfer from the photothermal conversion layer to the water body is effectively suppressed in the photothermal conversion process. Meanwhile, sufficient moisture is continuously supplied to the photo-thermal conversion layer through the water conveying pipeline under the action of capillary force, so that the continuous generation of solar steam is realized. Under the irradiation of sunlight intensity, the photothermal conversion layer is rapidly heated from 18.1 ℃ to 33.5 ℃ within one minute, and is stabilized at 38 ℃ after 40 minutes. After the heat insulation layer is irradiated for 40 minutes, the temperature is only raised to 25.5 ℃ from 18.1 ℃, and the temperature is basically maintained within the room temperature. The irradiation time was extended to 90 minutes and the temperature of the photothermal conversion layer and the thermal insulation layer were still stabilized at 39.5 ℃ and 25.5 ℃ respectively. On the other hand, in the irradiation time of 90 minutes, due to the blocking effect of the photothermal conversion layer on light and the inhibiting effect of the heat insulation layer on heat conduction, the lower water body is always kept within the room temperature, and the heat loss caused by the heat dissipation to the environment through the water body is greatly reduced.
4. The invention optimizes the porosity and the aperture of the photo-thermal conversion element, and further improves the conversion efficiency.
5. The parameter difference or the accumulated parameter difference of the time periods before and after the detection of the parameter sensing element can judge that the evaporation of the internal fluid is basically saturated and the volume of the internal fluid is not changed greatly through the parameter difference, under the condition, the internal fluid is relatively stable, the vibration of the tube bundle is poor, and therefore adjustment is needed to be carried out, the tube bundle vibrates, and heat collection is stopped. So that the fluid undergoes volume reduction to thereby realize vibration. When the pressure difference is reduced to a certain degree, the internal fluid starts to enter a stable state again, and heat collection is needed to ensure that the fluid is evaporated and expanded again, so that heat collection needs to be started.
Description of the drawings:
FIG. 1 is a schematic view of the structure within the water tank of a solar thermal collection apparatus;
FIG. 2 is a top view of a reduced graphene oxide light-to-heat conversion device;
FIG. 3 is a bottom view of the transparent glass cover;
FIG. 4 is a front view of the heat collecting system of the present invention.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings.
In this document, "/" denotes division and "×", "denotes multiplication, referring to formulas, if not specifically stated.
As shown in fig. 1 to 3, a solar heat collection device comprises a water tank 9 and a photothermal conversion element, wherein the upper end of the water tank is of an open structure, the photothermal conversion element floats on the upper portion of the water tank 9, the photothermal conversion element comprises a substrate 19 formed by a foaming material, a groove 42 with an opening on the upper side is formed on the substrate 19, a foamed nickel substrate 20 is filled in the groove 42, a capillary structure water delivery channel 18 is arranged on the lower wall surface of the substrate 19, the water delivery channel 18 is communicated with a water body of the water tank 9 and the foamed nickel substrate 20, a photothermal conversion coating 21 is arranged on the upper portion of the groove 42, the photothermal conversion coating 21 is connected with the foamed nickel substrate 20, and the buoyancy of the foaming material.
Driven by capillary action, water in the water body is transmitted to a foamed nickel matrix 20 in a foaming material matrix 19 through a water transmission channel 18, and then is transmitted to a photo-thermal conversion coating 21 on the upper surface of the foamed nickel matrix 20 through the capillary action of a porous medium of the foamed nickel matrix 20, and is subjected to heat absorption vaporization under the irradiation of sunlight to form steam. The generated steam is recovered by a recovery device. The floating substrate 19 holds the photothermal conversion layer out of the water surface, so that the dissipation of the generated heat energy to the lower water body and the surrounding environment by the film is inhibited, and the steam generation efficiency is improved.
Preferably, the upper surface of the photothermal conversion coating 21 is at the same height as the upper surface of the water body or is not more than 5 cm higher than the upper surface of the water body. Through above-mentioned facility, can make the better light and heat conversion that carries on of light and heat conversion coating 21, improve the efficiency of getting water.
Preferably, the groove 42 is circular in cross-section.
Preferably, a transparent glass cover 41 is arranged at the upper part of the water tank 9, the transparent glass cover 41 is in a circular arc structure, the glass cover comprises a water collecting tank 23 positioned at the lower side, the water collecting tank 23 comprises an inner vertical side wall, a horizontal wall extending from the bottom end of the vertical side wall to the horizontal direction, an outer vertical wall extending upwards along the other end of the horizontal wall, and a circular arc structure extending upwards and inwards along the outer vertical wall, the water collecting tank is formed among the inner vertical wall, the horizontal wall and the outer vertical wall, and a water drainage hole 22 is arranged on the horizontal wall, so that the collected fresh water in the water collecting tank is drained out, and the purpose of taking water from seawater is achieved.
Preferably, the inner wall of the circular arc structure is provided with a diversion trench, so that the steam can flow into the water collection trench in time after being condensed. As an improvement, a steam outlet pipe is arranged at the top of the transparent glass cover 41 and is connected with a cooling coil at the bottom of the water tank 9, steam is led into the cooling coil for cooling, water in the water tank 9 is preheated by utilizing heat released by steam condensation, and the water is led into a recovery device after the steam in the cooling coil is condensed into water.
As a modification, the outer wall of the transparent glass cover 41 is provided with a plurality of convex lenses 45 having an outward convex shape, as shown in fig. 4, the convex lenses 45 are uniformly distributed on the outer wall of the transparent glass cover 41, and the focal points of the convex lenses fall on the photothermal conversion coating to increase the absorption of solar energy. Thereby further accelerating the evaporation of the liquid.
Preferably, the convex lens is polygonal in shape on the outer wall of the transparent glass cover 41.
The outer wall of the transparent glass cover 41 is provided with the convex lenses which are uniformly distributed, so that solar energy can be better concentrated, the concentrated absorption of the solar energy is still ensured even if the position of the heat collecting device is changed, and the deviation of a focus caused by the arrangement of the position direction is avoided.
The device takes the sunshine as a driving source, generates a large amount of steam without the assistance of a heating device, and mainly comprises two parts: the device comprises a reduced graphene oxide photo-thermal conversion layer and a heat insulation layer. The photothermal conversion layer is a foam nickel-based reduction graphene oxide film; the matrix is a foamed polyethylene material; the substrate 19 placed in the water tank floats on the water surface because its foam material itself has a buoyancy greater than the gravity. Driven by capillary action, water in the water tank is transported to the photothermal conversion layer in the groove of the substrate through the foamed nickel substrate and is vaporized into steam under the irradiation of sunlight. The floating matrix 19 holds the photothermal conversion layer out of the water surface, and inhibits the generated heat energy from being dissipated to the lower-layer liquid by the film, so that the steam efficiency of the device is improved, and the great potential of the device as a photothermal conversion new energy material is shown. The preparation method has simple process, nontoxic and harmless raw materials and higher repeatability. The steam generating device can efficiently utilize solar energy to prepare solar steam, and has wide commercial value and application prospect.
Preferably, the photothermal conversion coating is a foamed nickel-based reduced graphene oxide film. The photothermal conversion element is prepared by the following method:
(1) synthesis of reduced graphene oxide: adding 1000-3000mg of graphene oxide into 1000-3000mL of deionized water, respectively adding 750-9000 mg (with an interval of 250 mg) of ascorbic acid to obtain graphene dispersion, respectively stirring and performing ultrasonic treatment (preferably 40KHz, 240W) for 60 minutes in sequence, and reacting for 30 minutes at 2.45GHz, 200W and 95 ℃ by using a microwave reactor. Removing impurities on the upper layer of the obtained suspension, carrying out suction filtration, repeatedly washing with ultrapure water for three times, and carrying out vacuum freeze drying on the sample obtained by suction filtration to obtain reduced graphene oxide powder.
(2) Preparing a photothermal conversion device: 1g of reduced graphene oxide (particle size 60nm) is dispersed by ultrasonic (preferably 40KHz, 240W) treatment to a volume ratio of 1000ml to 7: 1 in a mixed solution of water and ethanol. Agarose (12.5g) and urea (125g) were added to the solution and stirring was continued at 85 ℃ for 30 min. The resulting hot suspension was then applied evenly to the surface of the nickel foam. And naturally cooling the foamed nickel matrix with the reduced graphene oxide coating, freezing the cooled foamed nickel matrix in a refrigerator at the temperature of-21 ℃ for 12 hours, and taking out the cooled foamed nickel matrix.
(3) Preparation of the substrate 3: a common foaming material plate is taken and processed into a cylinder with the size suitable for the inner diameter of a beaker, and the preferred diameter is 20cm and the height is 10 cm.
Theoretical design calculation:
and (3) testing the mass loss: the solar steam generating device is placed in a 300-plus-1000 mL water-containing beaker, the beaker is placed on an electronic balance capable of recording mass data in real time, the mass change of the device and the beaker within 30-240 minutes is tested under the irradiation of a xenon lamp light source with the light intensity of 1-10kW/m2, and a mass change curve is drawn.
The vaporization efficiency eta of the photothermal conversion layer is calculated by the formulas (1), (2), (3) and (4)
Figure BDA0002572590440000061
m＝mLight (es)-mDarkness (2)
HLV＝1.91846×106[T1/(T1-33.91)]2 (3)
Q＝c(T1-T0) (4)
Wherein m is the net evaporation rate of water kg/m2h，mLight (es)Is the evaporation rate of water kg/m under the condition of illumination2h，mDarknessThe evaporation rate of water is kg/m under the condition of no illumination2h；HLVIs the latent heat of vaporization J/kg of water; t is1The evaporation temperature of water; t is0The initial temperature of water; c is the specific heat J/kgK of water; q is the heat J absorbed by the evaporation of water; einIs the energy kJ/m of the incident light input2h。
And (3) testing temperature change: the solar steam generating device is placed in a 300-plus-1000 mL water-containing beaker, the beaker is placed on an electronic balance capable of recording mass data in real time, and an infrared thermal imager is used for detecting the temperature change of the photo-thermal conversion layer before and after irradiation under the irradiation of a xenon lamp with the light intensity of 1-10kW/m 2.
And (3) blending, filtering and vacuum drying three reduced graphene oxide samples (rGO-50/200/400) with different reduction degrees and 100mg of foam nickel base to obtain the foam nickel base reduced graphene oxide photothermal conversion device. (1) The reduced graphene oxide source is connected with the foam nickel framework through weak van der waals force before the reduced graphene oxide source is reduced, and can fall off and transfer under the action of external force; (2) the driving force of the transfer of the reduced graphene oxide, namely the negative pressure of the reduced pressure filtration promotes the reduced graphene oxide on the back side to fall off and be attracted to the front side of the photothermal conversion layer; (3) the transfer channel of the reduced graphene oxide, namely the micron-sized hole structure between the foamed nickel frameworks provides a channel for transferring the reduced graphene oxide to the front surface of the photothermal conversion layer. The three factors are important in the formation process of the two-sided morphology of the foam nickel-based reduction-oxidation graphene photothermal conversion layer. Under the assistance of the heat insulation layer and the water conveying pipeline, the light absorption film is in indirect contact with the lower water body through the water conveying pipeline, so that the problem that the light-heat conversion layer is likely to sink or even decompose after being soaked for a long time is solved. The reduced graphene oxide has the advantages that the distance between molecular layers is shortened due to the removal of a large number of oxygen-containing groups, stronger intermolecular force is formed, and meanwhile, the surface hydrophilicity is greatly reduced, so that the reduced graphene oxide is agglomerated and settled.
In the process of pressure reduction and suction filtration, the reduced graphene oxide is extruded by a pair of acting forces in opposite directions to form a reduced graphene oxide shell, namely a suction force from top to bottom and a supporting force from bottom to top respectively. On a foam nickel matrix, under the action of reduced pressure suction filtration, the reduced graphene oxide gradually deposits downwards along with the reduction of liquid to form a loose porous structure. Under the action of strong suction force, the reduced graphene oxide is still tightly attached to the foam nickel framework. This indicates that the separation and transfer of reduced graphene oxide occurs between the layers of reduced graphene oxide rather than between the reduced graphene oxide and the foamed nickel skeleton.
In the photothermal conversion element of the present invention, since the photothermal conversion layer and the lower water body are separated by the heat insulating layer, heat loss caused by heat transfer from the photothermal conversion layer to the water body is effectively suppressed in the photothermal conversion process. Meanwhile, sufficient moisture is continuously supplied to the photo-thermal conversion layer through the water conveying pipeline under the action of capillary force, so that the continuous generation of solar steam is realized. Under the irradiation of sunlight intensity, the photothermal conversion layer is rapidly heated from 18.1 ℃ to 33.5 ℃ within one minute, and is stabilized at 38 ℃ after 40 minutes. After the heat insulation layer is irradiated for 40 minutes, the temperature is only raised to 25.5 ℃ from 18.1 ℃, and the temperature is basically maintained within the room temperature. The irradiation time was extended to 90 minutes and the temperature of the photothermal conversion layer and the thermal insulation layer were still stabilized at 39.5 ℃ and 25.5 ℃ respectively. On the other hand, in the irradiation time of 90 minutes, due to the blocking effect of the photothermal conversion layer on light and the inhibiting effect of the heat insulation layer on heat conduction, the lower water body is always kept within the room temperature, and the heat loss caused by the heat dissipation to the environment through the water body is greatly reduced.
Compared with a steam generating device with a photothermal conversion film directly floating on a water body, the high-efficiency solar steam generating device with the heat insulating material and the micro water delivery device has the advantages that the photothermal conversion layer prepared by synthesis can limit sunlight on the surface of the film, block radiation of the sunlight to the lower water body, reduce energy loss caused by scattering of the water body to the environment, improve the light energy utilization rate and improve the photothermal conversion performance. The thermal insulation layer and the water conveying pipeline adopted by the invention can separate the photo-thermal conversion layer from the water body, block the heat loss from the high-temperature film to the low-temperature water body, further reduce the energy loss and improve the light energy utilization rate, thereby further improving the photo-thermal conversion performance. The heat insulation material inhibits the conduction of heat from the light absorption film to the lower water body, and the heat loss is minimized; meanwhile, under the action of capillary force, the lower water body is indirectly connected with the light-heat conversion layer through the water delivery device and continuously supplies water for the light-heat conversion process. Under the cooperative assistance of the heat insulating material and the micro water delivery device, the steam efficiency of the whole photo-thermal conversion device is far higher than that of a film which purely floats on the water body. In addition, by preparing the reduced graphene oxide with different reduction degrees, the influence of the reduction degree on the photo-thermal conversion efficiency is deeply researched, and the experimental result shows that the photo-thermal conversion performance of the foam nickel-based reduced graphene oxide is gradually enhanced (up to 92.2% under the intensity of one sun) along with the improvement of the reduction degree. The solar steam generation device provides important experimental data and technical support for further research and application in the field of photothermal conversion, such as the fields of distillation purification, seawater desalination, sewage treatment and the like.
The reduced graphene oxide coating 21 on the upper surface of the foam nickel substrate is a porous coating, and the design method of the pore diameter and the porosity is as follows:
and (3) performing mathematical modeling on the working medium transportation process of the foam nickel matrix and the photothermal conversion layer by using a continuity equation, Darcy's law considering the gravity effect and an energy equation:
Figure BDA0002572590440000081
where φ is the porosity of the nickel foam, ρ is the density of the fluid, and v is the apparent velocity of the fluid.
Figure BDA0002572590440000082
In the formula, qVIs the volume flow, k is the permeability of the foamed nickel, μ is the dynamic viscosity of the fluid; a is the surface area of the reduced graphene oxide coating 21, the thickness of the L photothermal conversion layer, pv is the vacuum degree of decompression and suction filtration, and pe is atmospheric pressure.
Figure BDA0002572590440000083
Wherein (ρ c)m＝(1-φ)(ρc)s+φ(ρcp)f；λm＝(1-φ)λs+φλf；
Figure BDA0002572590440000084
In the formula, subscripts s and f represent a solid phase of the photothermal conversion layer and a liquid phase inside the photothermal conversion layer, respectively; c is the specific heat of the solid; c. CpIs the constant pressure specific heat of the fluid; lambda is the heat conductivity coefficient of the photo-thermal conversion layer; q' ″ is the heat per unit volume generated by the heat source in the light-to-heat conversion layer.
Applying a fractal theory to establish an expression of the porosity and permeability of the foamed nickel:
Figure BDA0002572590440000085
Figure BDA0002572590440000086
wherein D is foam nickel pore distribution fractal dimension, DTThe fractal dimension of the porosity of the foamed nickel is tortuous, and Q is oxygen reduced byThe total flow of the graphene coating 21 section a is normalized.
Obtaining the average pore size corresponding to the foam nickel matrix and the photothermal conversion layer according to the obtained parameter expression as follows: ln (p/p)0)＝-(2γVm/rRT)cosθ
In the formula, p0The saturated vapor pressure when the surface of the working medium on the surface of the photothermal conversion layer is a plane, p is the pressure of the liquid in the pores of the photothermal conversion layer, VmThe molar volume of the corresponding phase, gamma is the surface tension of the corresponding phase in each zone, R is a gas constant, T is an absolute temperature, and theta is a contact angle between the liquid working medium and the pore wall of the photothermal conversion layer; the corresponding phase refers to the condition of the working medium in the photothermal conversion layer during actual work, the working medium on the surface of the photothermal conversion layer is a vapor phase, and the working medium in the pores of the photothermal conversion layer is a liquid phase.
r is the aperture of the photothermal conversion layer, and the aperture and porosity parameters of the photothermal conversion layer have important influence on the steam generation rate. The smaller the pore diameter is, the larger the saturated vapor pressure on the surface of the photothermal conversion layer is, so that the steam is not beneficial to overflowing from the pores on the surface of the photothermal conversion layer; the larger the pore diameter, the smaller the photothermal absorption area of the photothermal conversion layer surface, resulting in a decrease in photothermal conversion efficiency. Therefore, the aperture of the photothermal conversion layer needs to be calculated to ensure the most effective evaporation rate.
Preferably, the device further comprises a solar auxiliary heating device, the auxiliary heating device comprises an evaporation end and a condensation end, the evaporation end is a solar heat collecting component, the condensation end is arranged in the water tank, and the water body in the water tank is preheated through heat release of the condensation end, so that the seawater desalination efficiency is further improved.
Preferably, the present invention may be used as a seawater desalination apparatus, wherein seawater is disposed in the water tank 9, and water in the seawater from the photothermal conversion element is recovered and condensed by means of steam.
Preferably, as shown in fig. 4, the water tank includes a water inlet pipe 43 and a water outlet pipe 44, and a water inlet valve and a water outlet valve are provided on the water inlet pipe 43 and the water outlet pipe 44, respectively. Seawater enters the water tank through the water inlet pipe and is discharged through the water discharge pipe when the seawater is desalinated to a certain degree.
Preferably, a seawater concentration detecting device is arranged in the water tank 9 for detecting the concentration of seawater, and the controller automatically controls the seawater discharge according to the detected seawater concentration. If the measured seawater concentration exceeds a certain numerical value, the controller controls the valve of the drain pipe to be opened, the drain pipe at the lower part of the water tank is opened, and the strong brine is discharged through the drain pipe.
Preferably, the water inlet is controlled by a valve of the seawater inlet and outlet pipe 43, the water inlet is stopped when the seawater level in the water tank reaches a certain level, and the valve of the water outlet pipe 44 at the lower part of the water tank is opened when the evaporated waste brine reaches a certain concentration, so that the strong brine is discharged through the water outlet pipe.
Preferably, after the strong brine is drained, the drain pipe valve is closed, and water is replenished again.
Preferably, the drain 44 valve in the lower part of the tank is closed when the detected salinity of the seawater in the tank is lower than a certain concentration.
Preferably, the water inlet pipe is opened while the drain pipe is opened, and water is supplied into the water tank. To avoid drying up in the water tank.
Preferably, a water level detection device is arranged in the water tank and used for detecting the water level height in the water tank. When the water level is lower than certain data, the controller controls the valve of the water inlet pipe to be opened to supplement water. When the water level reaches a certain height, the water inlet pipe valve is closed.
Although the present invention has been described with reference to the preferred embodiments, it is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (2)

1. The preparation method of the multi-lens solar heat collection device comprises a water tank and a photo-thermal conversion element, wherein the upper end of the water tank is of an opening structure, and the photo-thermal conversion element floats in seawater at the upper part of the water tank; the photothermal conversion element comprises a matrix formed by a foaming material, a groove with an opening at the upper side is formed on the matrix, a foamed nickel matrix is filled in the groove, a capillary structure water delivery channel is arranged on the lower wall surface of the matrix, the water delivery channel is communicated with a water body of a water tank and the foamed nickel matrix, a photothermal conversion coating is arranged on the upper part of the groove, the photothermal conversion coating is connected with the foamed nickel matrix, and the buoyancy of the foaming material is greater than the gravity; a method of making a photothermal conversion element comprising the steps of:
(1) synthesis of reduced graphene oxide: adding 1000-3000mg of graphene oxide into 1000-3000mL of deionized water, adding 750-9000 mg of ascorbic acid to obtain a graphene dispersion solution, respectively stirring and performing ultrasonic treatment for 60 minutes at intervals of 250mg of ascorbic acid, reacting for 30 minutes at 2.45GHz, 200W and 95 ℃ by using a microwave reactor, removing impurities on the upper layer of the obtained suspension, performing suction filtration, repeatedly washing with ultrapure water for three times, and performing vacuum freeze drying on the sample obtained by the suction filtration to obtain reduced graphene oxide powder;
(2) preparing a photothermal conversion device: 1g of reduced graphene oxide with the particle size of 60nm is dispersed to 1000ml of a volume ratio of 7: 1, adding 12.5g of agarose and 125g of urea into the mixed solution of water and ethanol, continuously stirring for 30min at 85 ℃, then uniformly coating the obtained hot suspension on the surface of the foamed nickel, naturally cooling the foamed nickel matrix with the reduced graphene oxide coating, freezing at-21 ℃, freeze-drying in a refrigerator for 12 h, and taking out;
(3) preparing a matrix: taking a common foaming material plate, and processing the common foaming material plate into a proper cylinder;
the water level detection device is arranged in the water tank and used for detecting the water level height in the water tank, when the water level is lower than certain data, the controller controls the water inlet pipe valve to be opened for water supplement, and when the water level reaches a certain height, the water inlet pipe valve is closed.
2. The method of claim 1, wherein the convex lens is polygonal in shape on the outer wall of the transparent glass cover.
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JP3766309B2 (en) * 2001-10-22 2006-04-12 賢士 宍戸 Desalination plant using solar thermal energy
CN202246147U (en) * 2011-09-16 2012-05-30 刘浩涤 Novel solar energy sea water desalinization and salt manufacturing device
CN104495966B (en) * 2014-12-17 2016-04-13 西北工业大学 The seawater desalination system that a kind of bubbling humidification is coupled with heat pump cycle and processing method
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