A three-dimensional solar evaporation device based on interfacial evaporation

Abstract

The present application belongs to the technical field of solar evaporation device, and discloses a three-dimensional solar evaporation device based on interfacial evaporation, which comprises a top evaporation layer, a side evaporation structure and a water conveying structure, the upper end of the water conveying structure is connected with the top evaporation layer, the lower end of the water conveying structure is in contact with a water source to be treated, the side evaporation structure is sleeved outside the water conveying structure, and the upper plane of the side evaporation structure is arranged at a distance from the lower plane of the top evaporation layer. The top evaporation layer is arranged to form a solar evaporation interface, the side evaporation structure is arranged at a distance from the top evaporation layer, the downward heat transfer of the top evaporation layer is reduced, solar energy is concentrated on the top evaporation layer to realize a high-temperature state, and the upper and lower surfaces of the top evaporation layer can be used for evaporation. In addition, the side evaporation structure makes full use of the energy in the environment, further improves the evaporation rate, and solves the problem of low evaporation rate of the existing evaporation device.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of solar evaporation devices, and more particularly relates to a three-dimensional solar evaporation device based on interfacial evaporation. BACKGROUND

[0002] Water is the source of all things. With the development of economy and the increase of population, people's demand for water resources is increasing. Although most of the earth is covered by water, most of it is not directly drinkable seawater, and freshwater resources are extremely limited.

[0003] In order to solve this global problem, many researchers have spared no effort to develop effective freshwater production technology. Traditional freshwater production technology is powered by non-renewable fossil energy, which has caused serious environmental and sustainability problems. In order to overcome these limitations, more and more people are committed to exploring new freshwater production technology powered by solar energy.

[0004] Starting from the earliest solar evaporation system based on bottom heating, after years of continuous research and improvement, researchers have been committed to improving the evaporation efficiency. Finally in 2014, Chen et al. of Massachusetts Institute of Technology proposed a revolutionary research achievement, which applied double-layer carbon-based materials to solar evaporation through heat localization, namely interfacial heating, reducing unnecessary heating of a large amount of water and greatly improving the evaporation efficiency.

[0005] Generally, the evaporation efficiency of two-dimensional structure is limited by solar radiation. Under the irradiation of 1000W·m -2 of solar energy, assuming that the energy transfer efficiency from solar energy to steam is 100% without any energy loss, the limit evaporation rate of two-dimensional structure is 1.47kg·m -2 ·h -1 Three-dimensional structure can break through this limit evaporation rate and has been concerned, but the current three-dimensional solar evaporation structure still has the problems of complex structure and low evaporation rate. SUMMARY

[0006] In view of the defects or improvement needs of the current three-dimensional structure interfacial evaporation, such as complex structure and low evaporation rate, the present application provides a three-dimensional solar evaporation device based on interfacial evaporation, which aims to improve the evaporation rate of the interfacial evaporation system by three-dimensional structure design and utilizing solar energy and environmental energy.

[0007] To achieve the above purpose, the present application adopts the following technical solutions:

[0008] Provided is a three-dimensional solar evaporation device based on interfacial evaporation, comprising a top evaporation layer, a side evaporation structure, and a water conveying structure, the upper end of the water conveying structure being connected to the top evaporation layer, the lower end of the water conveying structure being in contact with a water source to be treated, the side evaporation structure being sleeved outside the water conveying structure, the upper plane of the side evaporation structure being spaced apart from the lower plane of the top evaporation layer.

[0009] Preferably, the projection of the top evaporation layer in the vertical direction covers the projection of the side evaporation structure in the vertical direction.

[0010] Preferably, the projection of the top evaporation layer and the side evaporation structure in the vertical direction completely coincides.

[0011] Preferably, the side evaporation structure is a cylindrical structure.

[0012] Preferably, the bottom of the side evaporation structure is in contact with the water source to be treated.

[0013] Preferably, a support structure is included, which is connected to the bottom of the water conveying structure or the side evaporation structure, so that the entire device floats on the water surface.

[0014] Preferably, the top evaporation layer and the side evaporation structure are respectively composed of a porous material with a light absorption rate greater than 90%.

[0015] Preferably, the water conveying structure is composed of a hydrophilic material.

[0016] Overall, the present application has the following technical effects through the above technical solutions conceived:

[0017] 1. A three-dimensional solar evaporation device based on interfacial evaporation is provided, which forms a solar evaporation interface by setting a top evaporation layer, and reduces the downward heat transfer of the top evaporation layer by setting a side evaporation structure at a distance from the top evaporation layer, so that solar energy can be concentrated on the top evaporation layer to achieve a high-temperature state, and the upper and lower surfaces of the top evaporation layer can be used for evaporation, which is conducive to achieving a substantial increase in evaporation efficiency. In addition, the side evaporation structure naturally absorbs heat and cools down to a temperature lower than the ambient temperature, thereby continuously obtaining energy from the environment, improving the utilization rate of energy in the environment, further improving the evaporation rate of the interfacial evaporation system, and solving the problem of low evaporation rate of existing evaporation devices.

[0018] 2. In the present application, the outer diameters of the top evaporation layer and the side evaporation structure are preferably equal, which provides an optimal solution for maximizing the evaporation efficiency and achieving further improvement in evaporation efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1is a schematic diagram of a three-dimensional solar device structure based on interfacial evaporation provided by the embodiments of the present application;

[0020] Figure 2 is a simulated temperature cloud chart of the three-dimensional solar device based on interfacial evaporation provided by the embodiments of the present application;

[0021] Figure 3 is a simulated water concentration distribution chart of the three-dimensional solar device based on interfacial evaporation provided by the embodiments of the present application;

[0022] Figure 4 is a simulated cloud chart of the evaporation rate of the three-dimensional solar device based on interfacial evaporation changing with the diameter and height of the side evaporation structure provided by the embodiments of the present application;

[0023] In all the drawings, the same reference signs are used to represent the same elements or structures, wherein:

[0024] 1 - top evaporation layer, 2 - water transport structure, 3 - side evaporation structure, 4 - support structure. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0026] Please refer to Figure 1The application provides a three-dimensional solar evaporation device based on interface evaporation, which comprises a top evaporation layer 1, a side evaporation structure 3 and a water conveying structure 2, the upper side of the water conveying structure 2 is connected with the top evaporation layer 1, the lower side of the water conveying structure 2 is in contact with a water source to be treated, the side evaporation structure 3 is sleeved outside the water conveying structure 2, and the upper plane of the side evaporation structure 3 is arranged in a spaced mode with the lower plane of the top evaporation layer 1. Under the condition that a solar simulator irradiates the three-dimensional solar evaporation device in a vertical mode, the top evaporation layer 1 absorbs solar energy for evaporation, the side evaporation structure 3 does not receive the irradiation of solar energy, and natural evaporation is achieved by utilizing the energy in the environment, and the evaporation rate is the ratio of the total evaporation amount of water in the device per unit time to the solar radiation area. On one hand, the temperature of the top evaporation layer 1 is increased due to the absorption of solar energy, the higher the temperature is, the smaller the latent heat of evaporation of water is, and the more conducive to evaporation is, and since the temperature of the top evaporation layer 1 is higher than the temperatures of other structures of the device and the water source and the environment, heat transfer to the outside is inevitable, and the heat transfer downward of the top evaporation layer 1 can be reduced by utilizing the air heat insulation mode of the structure arranged in a spaced mode, so that the high-temperature state of the top evaporation layer 1 is maintained as much as possible; on the other hand, the structure enlarges the evaporation area, so that the upper and lower surfaces of the top evaporation layer 1 can be used for evaporation, and solar energy is more effectively utilized.

[0027] Further, the three-dimensional solar evaporation device based on interface evaporation further comprises a supporting structure 4, which is connected to the bottom of the water conveying structure 2 or the side evaporation structure 3, so that the whole device floats on the water surface. The material of the supporting structure 4 can be flexibly selected as a low-density material capable of floating on water, for example, polyethylene foam.

[0028] Further, the shape of the side evaporation structure 3 can be flexibly arranged, for example, the side evaporation structure 3 can be a cylindrical structure, or can be other shapes, for example, a prism or other irregular shapes, which are not limited in particular.

[0029] Further, the projection of the top evaporation layer 1 in the vertical direction covers the projection of the side evaporation structure 3 in the vertical direction, for example, when the side evaporation structure 3 is a cylindrical structure, the side evaporation structure 3 and the top evaporation layer 1 are coaxially arranged, and the diameter of the side evaporation structure 3 is not greater than the diameter of the top evaporation layer 1. Because when the diameter 2r3 of the side evaporation structure 3 is greater than the diameter 2r1 of the top evaporation layer 1, the top of the side evaporation structure 3 also receives part of the solar energy, and this part of energy is used to increase the temperature of the side evaporation structure 3, and then due to the increase of the overall diameter, the solar radiation area is increased, and the utilization rate of solar energy of the top evaporation layer 1 is higher than that of the side evaporation structure 3, that is, the increased solar radiation area increases the utilization rate of solar energy on the top evaporation layer 1, so that the design of 2r3>2r1 causes energy waste.

[0030] Further, the top evaporation layer 1 and the side evaporation structure 3 are completely overlapped in the vertical direction, for example, when the side evaporation structure 3 is a cylindrical structure, the diameter of the side evaporation structure 3 is equal to the diameter of the top evaporation layer 1, at this time, the side evaporation area reaches the maximum, thereby facilitating the maximum utilization of the energy in the environment for evaporation.

[0031] Further, the side evaporation structure 3 is in contact with the water source to be treated, and has the water conveying capacity.

[0032] In a specific embodiment, the support structure 4 contains a through hole vertically penetrating through the support structure 4, and the surface of the through hole is fitted to the outer surface of the side evaporation structure 3; the lower part of the side evaporation structure 3 penetrates through the through hole of the support structure 4 and is immersed in water.

[0033] Further, the top evaporation layer 1 is composed of a porous material with a light absorption rate greater than 90%, according to actual needs, carbonized corn cob, carbonized wood, carbonized mushroom, carbonized radish, etc. can be selected to meet the requirement of high light absorption rate. The higher the light absorption rate of the porous material, the more solar energy it absorbs, and the higher the evaporation rate of the three-dimensional solar evaporation device. The material of the side evaporation structure 3 can be selected from the same type of material as the top evaporation layer 1, or other materials with high absorption rate, low thermal conductivity, and good hydrophilicity.

[0034] Further, the water conveying structure 2 is composed of a hydrophilic material, the lower end penetrates through the through hole of the support structure 4 and is immersed in water, and the upper end is in communication with the top evaporation layer 1. Specifically, the material of the water conveying structure 2 can be flexibly selected, for example, bamboo paper, plant fiber, carbon felt, etc. with good hydrophilicity to meet the evaporation demand of the top evaporation layer 1.

[0035] Further, the water conveying structure 2 is provided in a cylindrical structure, and its diameter and material determine its water conveying capacity, and the solar evaporation device needs to be adjusted so that the water conveying rate of the water conveying structure 2 matches the evaporation rate of the top evaporation layer 1. The diameter and material of the water conveying structure 2 are determined by the following method:

[0036] Under the condition of sufficient water supply, the evaporation rate of the top evaporation layer 1 under the design working condition is obtained;

[0037] The water supply rate of the water conveying structure of different materials is obtained by experimental method: the cylindrical water conveying structure is vertically placed, the lower end is in contact with the water source, the water absorption amount per unit time is calculated, and the water supply rate of the water conveying structure of corresponding material is obtained by dividing the water absorption amount per unit time by the cross-sectional area of the cylindrical water conveying structure;

[0038] The evaporation rate of the top evaporation layer 1 under the design working condition is divided by the water supply rate to obtain the required cross-sectional area of the water conveying structure of corresponding material, and then the appropriate material and diameter of the water conveying structure 2 are selected.

[0039] The thickness h3 of the support structure 4 is 5mm-20mm, and the outer diameter r4 is 40mm-100mm; the height h4 of the water delivery structure 2 relative to the upper surface of the support structure 4 is 30mm-100mm, and the diameter r2 is selected to match the evaporation rate with the water delivery rate; the thickness h1 of the top evaporation layer 1 is 0.1mm-10mm, and the diameter r1 is 10mm-50mm; the ratio of the height of the side evaporation structure 3 relative to the upper surface of the support structure 4 to the height of the water delivery structure 2 relative to the upper surface of the support structure 4 is h2 / h4=0.1-0.9, and the ratio of the outer diameter of the side evaporation structure 3 to the outer diameter of the top evaporation layer 1 is r3 / r1=0.1-1, and under the condition of sufficient water supply, the influence of the structure size change on the evaporation rate is explored.

[0040] The top evaporation layer 1 absorbs the highest temperature of solar energy, and the top evaporation layer 1 and the side evaporation structure 3 have a gap, which maintains the high temperature state of the top evaporation layer 1 through air insulation, and the higher the temperature, the smaller the latent heat of water evaporation, which is more conducive to evaporation. At the same time, the side evaporation structure 3 is designed to absorb energy from the environment, and the larger the area and the more contact with the environment, the more conducive to evaporation, and through the close cooperation of the top evaporation layer 1 and the side evaporation structure 3, the water evaporation rate is effectively improved.

[0041] Embodiment 1:

[0042] In this embodiment, as shown in Figure 1 , the cylindrical top evaporation layer 1 and the cylindrical side evaporation structure 3 have the same diameter to maximize the use of energy from the environment. The water delivery structure 2 is made of bamboo paper with good hydrophilicity, and the bamboo paper is cylindrical with a height h4 of 70mm and a diameter r2 of 8mm, and the bottom is immersed in water by 10mm; the support structure 4 is made of circular ring polyethylene foam with a foam thickness h3 of 10mm, an outer diameter r4 of 70mm, and an inner diameter that matches the side evaporation structure 3, and the top evaporation layer 1 is made of carbonized corncob with a height h1 of 0.5mm and a diameter r1 of 30mm, and is 60mm away from the water surface; the cylindrical side evaporation structure 3 is made of carbonized corncob with a height h2 of 65.5mm and a diameter r3 of 30mm, and the bottom is immersed in water by 10mm.

[0043] It is known that the solar energy absorption rate of carbonized corncob is 95%, the environmental temperature is controlled at 20℃, the environmental humidity is 50%, the water delivery rate matches the evaporation rate, and the water delivery rate is 1000W·m -2 Under the condition of vertical irradiation of simulated sunlight, the solar evaporation area is 0.0007065m 2 .

[0044] The evaporation rate of the device under the above setting conditions is calculated by fluid simulation. The specific principle of obtaining the evaporation speed by fluid simulation is as follows:

[0045] The evaporation rate of the solar interface evaporation system can be solved by the following equation:

[0046] The momentum and mass conservation equations of fluid flow are:

[0047]

[0048]

[0049] Where u is the velocity of the fluid, here the fluid refers to water vapor, t is time, p is the density of the fluid, which is related to temperature and pressure, and m is the viscosity.

[0050] The vapor diffusion equation is:

[0051]

[0052] Where c is the concentration of water vapor, D is the water vapor diffusion coefficient, which is 2.6 x 10 -5 m 2 ·s -1 , R v is the evaporation rate, and its calculation equation is:

[0053] R v =K×M v ×(c sat -c);

[0054]

[0055] Where K is the evaporation rate coefficient, K = 1000 m·s -1 , which can make the vapor concentration in the porous medium uniform when saturated; c sat is the saturation concentration of water vapor, p sat (T) is the saturation pressure of water vapor, which is related to temperature and can be obtained from the water vapor saturation pressure table; M v is the molar mass of water vapor, and R is the ideal gas constant, with a value of 8.314 J·mol -1 ·K -1 .

[0056] The relative humidity and temperature of air determine the moisture concentration in the air. The smaller the relative humidity and the higher the temperature, the smaller the moisture concentration in the air, which is conducive to the diffusion of water vapor from the evaporator surface to the air due to the concentration difference.

[0057] The energy conservation equation is:

[0058]

[0059] Where T is the temperature, C pis the constant pressure heat capacity, whose value is 1107 J·kg -1 ·K -1 , κ is the thermal conductivity, whose value is 0.05 W·m -1 ·K -1 , Q is the heat source, which can be solved according to the following equation:

[0060] Q=-R v ×H evap ;

[0061] H evap =45000-42.95×(T-273);

[0062] wherein, H evap is the latent heat of water evaporation, which is related to temperature. The faster the evaporation rate, the more heat the water evaporation endotherm takes away, and finally reaches a steady state, the system temperature reaches the maximum value.

[0063] For the upper surface of the top evaporation layer 1, it can absorb solar energy, and the energy input condition is:

[0064] -n.q=Q b ;

[0065] wherein, the left side of the equation is the net heat flow into the vertical surface, q is the heat flux density, and n is the direction vector perpendicular to the surface of the object; the right side of the equation Q b is the absorbed solar energy, which is equal to the solar radiation intensity multiplied by the absorption rate of the material, that is, Q b =1000×95% W·m -2 . Q b can be substituted into the above energy conservation equation, and the evaporation rate of the finite element unit of the top evaporation layer 1 is obtained through finite element simulation, and then the evaporation amount and evaporation rate of the top evaporation layer 1 are obtained.

[0066] The main variables of the control equation of the evaporation system are time, moisture concentration and temperature. When the system reaches a steady state, the moisture concentration and temperature distribution of the system can be obtained, and thus the evaporation rate at the steady state is obtained according to the simulation calculation:

[0067] The evaporation amount of the top evaporation layer 1 is 7.251×10 -4 kg·h -1 , the evaporation amount of the side evaporation structure 3 is 3.269×10 -4 kg·h -1 , the total evaporation amount is 10.52×10 -4 kg·h -1 , and then the unit area evaporation rate is 1.49 kg·m -2 ·h -1 .

[0068] AsFigure 2 Fig. 2 shows a simulated temperature cloud chart of the present embodiment, Figure 3 Fig. 3 shows a simulated water concentration distribution chart of the present embodiment, the top evaporation layer 1 has a higher temperature due to absorbing solar energy, and the evaporation water concentration is large, while the side evaporation structure 3 has a lower temperature than the ambient temperature due to the evaporation of water.

[0069] Comparative Example 1:

[0070] Comparative Example 1 is different from Example 1 only in that there is no top evaporation layer 1 and water delivery structure 2, and the height of the upper end of the cylindrical side evaporation structure 3 relative to the upper surface of the support structure 4 is 70 mm, and the remaining structures and conditions are consistent with Example 1.

[0071] According to the calculation of Example 1, when the system reaches a steady state, the evaporation amount of the upper surface of the side evaporation structure 3 is 2.809 x 10 -4 kg·h -1 , the side surface evaporation amount is 5.494 x 10 -4 kg·h -1 , the total evaporation amount is 8.303 x 10 -4 kg·h -1 , the solar evaporation area is 0.0007065 m 2 , and thus the evaporation rate is 1.18 kg·m -2 ·h -1 .

[0072] Comparative Example 2:

[0073] Comparative Example 2 is different from Example 1 only in that there is no side evaporation structure 3, and the remaining structures and conditions are consistent with Example 1.

[0074] According to the calculation of Example 1, when the system reaches a steady state, the evaporation amount of the upper surface of the top evaporation layer 1 is 7.319 x 10 -4 kg·h -1 , the calculation of the evaporation amount of the side surface of the water delivery structure is 1.271 x 10 -4 kg·h -1 , the calculation of the total evaporation amount is 8.59 x 10 -4 kg·h -1 , the solar evaporation area is 0.0007065 m 2 , and thus the evaporation rate is 1.22 kg·m -2 ·h -1 .

[0075] Comparative Analysis:

[0076] Under the same environmental conditions, the water evaporation rates of Example 1, Comparative Example 1, and Comparative Example 2 are compared in the following table:

[0077]

[0078] In Comparative Example 1 and Comparative Example 1, the evaporation amount of the upper surface of the side evaporation structure 3 in Example 1 and Comparative Example 1 is not much different, but the evaporation amount of the top evaporation layer 1 in Example 1 is increased by 158.13% compared with the evaporation amount of the upper surface in Comparative Example 1. This is mainly due to the fact that the top evaporation layer 1 is arranged in a spaced manner with the side evaporation structure 3, which blocks the downward heat transfer of the top evaporation layer 1, and the solar energy only heats a small amount of water in the top evaporation layer 1, thereby ensuring the rapid heating of the water in the top evaporation layer 1, and at the same time, the evaporation area is expanded, and the two superimposed effects greatly improve the solar evaporation efficiency, and the utilization of solar energy is more sufficient, and finally good results are achieved. Compared with Comparative Example 1, the evaporation rate of Example 1 is increased by 26.3%.

[0079] In Comparative Example 1 and Comparative Example 2, the evaporation amount of the upper surface of the top evaporation layer 1 in Example 1 and Comparative Example 2 is not much different, but the evaporation amount of the side evaporation structure 3 in Example 1 is increased by 157.20% compared with the evaporation amount of the side surface in Comparative Example 2. This is mainly due to the fact that the side evaporation structure 3 in Example 1 has a larger surface area for natural evaporation than Comparative Example 2, and the utilization of energy in the environment is more sufficient, and good results are achieved. Compared with Comparative Example 2, the evaporation rate of Example 1 is increased by 22.1%. By adjusting the ratio of r3 / r1 and h2 / h4, it can be calculated that the larger the value of r3 / r1 and h2 / h4, the more sufficient the utilization of energy in the environment, and the greater the evaporation rate. The influence of the size change of the side evaporation structure 3 on the evaporation rate is shown in Figure 4

[0080] In general, under the same experimental conditions, the top evaporation layer 1 of Example 1 can make full use of solar energy, and the side evaporation structure 3 is more conducive to the utilization of energy in the environment. Through the mutual cooperation of the two structures, Example 1 obtains a greater evaporation rate, and under the same conditions of sunlight irradiation, the evaporation efficiency of the interface evaporation system is effectively improved.

[0081] Those skilled in the art will readily understand that the above description is only a preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A three-dimensional solar evaporation device based on interfacial evaporation, characterized in that, It includes a top evaporation layer (1), a side evaporation structure (3), and a water conveying structure (2). The upper end of the water conveying structure (2) is connected to the top evaporation layer (1), and the lower end of the water conveying structure (2) is in contact with the water source to be treated. The side evaporation structure (3) is sleeved outside the water conveying structure (2). The upper plane of the side evaporation structure (3) is spaced apart from the lower plane of the top evaporation layer (1). The vertical projection of the top evaporation layer (1) covers the vertical projection of the side evaporation structure (3). The side evaporation structure (3) is a cylindrical structure.

2. The three-dimensional solar evaporation device based on interface evaporation as described in claim 1, characterized in that, The projections of the top evaporation layer (1) and the side evaporation structure (3) in the vertical direction completely overlap.

3. The three-dimensional solar evaporation device based on interface evaporation as described in claim 1, characterized in that, The bottom of the side evaporation structure (3) is in contact with the water source to be treated.

4. The three-dimensional solar evaporation device based on interfacial evaporation as described in any one of claims 1-3, characterized in that, Includes a support structure (4), which is connected to the bottom of the water conveying structure (2) or the side evaporation structure (3), so that the entire device floats on the water surface.

5. The three-dimensional solar evaporation device based on interfacial evaporation as described in any one of claims 1-3, characterized in that, The top evaporation layer (1) and the side evaporation structure (3) are respectively composed of porous materials with a light absorption rate greater than 90%.

6. The three-dimensional solar evaporation device based on interfacial evaporation as described in any one of claims 1-3, characterized in that, The water conveyance structure (2) is made of hydrophilic material.

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