A solar evaporator with double-helix lateral structure and a preparation method thereof

Abstract

This invention relates to the fields of interfacial water evaporation, seawater desalination, and wastewater treatment, and discloses a solar evaporator with a double-helix lateral structure. The evaporator includes a substrate with water absorption and transport functions. The outer wall of the substrate is provided with a double-helix structure capable of actively inducing micro-air convection. The double-helix structure is an axially extending double-helix groove or double-helix protrusion. During evaporation, the double-helix structure can actively disrupt the stagnant air boundary layer, enhance the outward diffusion of water vapor, and reduce the saturated vapor pressure of the lateral surface, thereby significantly enhancing the evaporation rate of the lateral surface. The core of this invention lies in a unique, functional macroscopic geometric structure, which is an integral part of the evaporator body, rather than an external attachment.

Description

Technical Field

[0001] This invention relates to the technical fields of interfacial water evaporation, seawater desalination, and wastewater treatment, and specifically to a solar evaporator with a double-helix lateral structure. Background Technology

[0002] Solar-driven interfacial water evaporation technology, with its renewable energy utilization, simple system structure, and potentially low operating costs, has become a powerful technological approach for seawater desalination, emergency water supply, and industrial wastewater treatment. The core of this technology lies in the design and manufacture of a highly efficient photothermal conversion evaporator: maximizing solar energy absorption and heat utilization efficiency while ensuring continuous interfacial wetting and high-flux evaporation, thereby achieving a stable water production rate per unit area.

[0003] Significant progress has been made in this field to improve interfacial evaporation efficiency, mainly focusing on two levels: first, innovation at the material level, developing photothermal functional materials with high light absorption and low heat loss; second, optimization of the internal micro / nano structure and water supply system, constructing porous networks with good capillary transport capabilities through special preparation processes to ensure timely water replenishment. These two technical approaches have greatly promoted the improvement of the basic performance of evaporators.

[0004] In terms of device morphology, three-dimensional (3D) structures are widely considered an effective way to improve evaporation rates because they have a larger exposed evaporation surface area than two-dimensional planes. To adapt to engineering production and modular deployment, regular three-dimensional shapes that are easy to mold and process are often used in practice, such as cylinders, cones, and other rotationally or regularly symmetrical structures. Because they are not only easy to fabricate and process, but also convenient for mechanical assembly and stable design of floating systems, they have become the recognized basic device form in this field.

[0005] However, it is precisely in these widely adopted basic device forms that a long-neglected bottleneck problem limiting further performance breakthroughs is gradually emerging. Existing research and engineering implementations often default to the above-mentioned classical configurations and focus on material and internal microstructure for technical optimization, while rarely conducting systematic optimization from a macro-geometric perspective on the side morphology of the evaporator, the coupling between the gas-liquid interface and the surrounding airflow field.

[0006] In actual operation, the lateral surface of the device can contribute a considerable evaporation surface area when wetted. However, under natural or weak wind conditions, a stagnant air boundary layer rich in water vapor often forms near the smooth sidewall, which increases the local vapor pressure on the side and thus significantly inhibits the lateral evaporation flux, becoming a bottleneck restricting the overall performance.

[0007] To address this bottleneck, simply increasing the device height to improve evaporation presents an inherent contradiction. Increasing the device height lengthens the water transport path; if the capillary water supply rate cannot promptly replenish the water required for evaporation at higher elevations, localized dry spots, insufficient water supply, and salting-out phenomena will occur, ultimately reducing overall water production efficiency and increasing maintenance burden. Therefore, simply increasing the size cannot fundamentally overcome the boundary layer limitation.

[0008] In summary, the requirements for engineering and long-term stable operation necessitate new solutions at the macroscopic geometric level: maintaining the advantages of modular manufacturing and mass production of rotationally symmetric devices such as cylinders / cones, while introducing manufacturable and highly functional macroscopic textures or turbulence structures on the sides to endogenously regulate the gas phase flow field, thin the vapor boundary layer, and promote lateral evaporation; at the same time, this structure needs to work in conjunction with an efficient water supply system and anti-saltation / self-cleaning strategies to ensure long-term stability and ease of maintenance.

[0009] Therefore, without sacrificing existing engineering advantages, introducing a macroscopically functionalized structure into the side of common rotationally symmetric column / cone evaporators—one that facilitates mass production, effectively enhances lateral air convection, reduces boundary layer effects, and balances water supply and anti-saltation—has become a key technical problem urgently needing to be solved in this field. Solving this problem will help achieve synergistic optimization of materials, microstructure, and macroscopic geometry, thereby obtaining higher evaporation rates and lower maintenance costs under variable weather conditions.

[0010] Existing technology: Currently, the most common macroscopic geometries in the research and application of three-dimensional solar evaporators are cylindrical and conical evaporators. These structures, due to their rotational or regular symmetry, are easily cast, freeze-formed, or printed using molds, making them suitable for mass production. They have become the recognized basic device forms in this field. The lateral surfaces of these conventional cylindrical or conical evaporators are typically smooth or have only simple morphologies with microscopic roughness of the material itself. Water evaporation occurs not only on the top surface but also simultaneously on the wetted sides. Existing technology mainly relies on evaporation from the top surface and passive evaporation from the sides under natural conditions.

[0011] Limitations: Despite significant advancements in materials and internal structures, the simple macroscopic geometry employed in existing technologies, particularly in the design of lateral surfaces, presents the following limitations that restrict further improvements in overall performance:

[0012] 1. Lateral evaporation efficiency is limited due to the existence of an evaporation "boundary layer" bottleneck. Under natural conditions without forced external ventilation (such as strong winds), a relatively static air boundary layer with a high water vapor concentration forms near the smooth sidewalls of the evaporator during the evaporation process. This high-humidity boundary layer significantly increases the local vapor pressure, thereby inhibiting further evaporation of moisture from the sidewalls and forming an evaporation bottleneck. Traditional simple geometric shapes do not have the ability to actively disrupt or weaken this boundary layer.

[0013] 2. Overall performance improvement has reached a bottleneck due to a lack of simplistic design dimensions. Existing research often relies on increasing the height of the evaporator (i.e., increasing the lateral area) to improve total evaporation. However, increasing the height significantly lengthens the water transport path at the bottom. When the water supply rate cannot keep up with the evaporation rate, it can lead to the top drying out and salt accumulation, limiting performance improvement. This indicates that the strategy of simply increasing size to improve performance has reached a bottleneck, and breakthroughs in new design dimensions are urgently needed.

[0014] 3. Homogeneous design approaches neglect the optimization of the "surface-air" interface. Much research focuses on the "solid-liquid" interface (material light absorption, moisture transport), while neglecting the interaction between the "gas-liquid" evaporation interface and the surrounding air environment. Existing designs lack an intrinsic, energy-free structure capable of actively managing and optimizing the lateral surface microflow field, thus wasting the enormous potential contributed by the lateral evaporation area. Summary of the Invention

[0015] To address the problems existing in the prior art, the present invention provides a rationally designed solar evaporator with a double-helix lateral structure.

[0016] The technical solution of the present invention is as follows:

[0017] A solar evaporator with a double-helix lateral structure includes a substrate with water absorption and transport functions. The outer wall of the substrate is provided with a double-helix structure that can actively induce micro-air convection. The double-helix structure is a double-helix groove or double-helix protrusion extending along the axial direction. During the evaporation process, the double-helix structure can actively disrupt the stagnant air boundary layer, enhance the outward diffusion of water vapor, and reduce the saturated vapor pressure of the lateral surface, thereby significantly enhancing the evaporation rate of the lateral surface.

[0018] Furthermore, the substrate is made of a material with hydrophilic and water-absorbing properties, including but not limited to biomass, porous ceramics, polymer foams (such as polyurethane and melamine foam), 3D-printed polymer / hydrogel skeletons, wood, etc.

[0019] Furthermore, a photothermal material layer is sprayed onto the top surface and the entire side surface of the substrate. This material is used to absorb light energy and convert it into heat energy, thereby forming a photothermal effect. The photothermal material is not limited to graphite powder, but also includes common photothermal materials such as polydopamine, carbon nanotubes (CNT), Mxene, carbon black, and metal nanoparticles.

[0020] Furthermore, the substrate can be a columnar or conical shape. The columnar shape can be a cylinder, square prism, polygonal prism, etc.; the conical shape can be a cone, pyramid, frustum, square frustum, etc.

[0021] Furthermore, the double helix structure can be a continuous or discontinuous structure extending from the top to the bottom of the substrate, or a double helix structure covering a portion of the side surface of the substrate.

[0022] Furthermore, the double helix structure extends from the top of the substrate to the bottom of the substrate, and forms exactly an integer number of turns;

[0023] A method for preparing a solar evaporator with a double-helix lateral structure includes the following steps:

[0024] Step 1) Preparation of photothermal material:

[0025] A photothermal material solution is prepared by mixing photothermal materials and binders in a certain proportion;

[0026] Step 2) Fabrication of a solar evaporator substrate with a double-helix lateral structure:

[0027] Using materials with hydrophilic and water-absorbing properties, a solar evaporator substrate with a double-helix lateral structure is processed through one or more methods, including subtractive manufacturing (such as carving, cutting, etc.), additive manufacturing (such as 3D printing, etc.), and equal-material manufacturing (such as mold casting, injection molding, etc.).

[0028] Step 3) Spraying the photothermal functional layer:

[0029] The photothermal material prepared in step 1) is uniformly sprayed onto the outer surface of the solar evaporator substrate prepared in step 2); after spraying, it is dried; thus, a cylindrical solar evaporator with a double helix structure is obtained.

[0030] The beneficial effects of this invention are as follows:

[0031] 1) Double helix lateral structure:

[0032] The core of this invention lies in a unique, functional macroscopic geometric structure. Specifically, a double-helix groove (or ridge) structure with specific geometric parameters (such as pitch, depth, width, helix angle, etc.) is designed and fabricated on the lateral surface of a columnar or conical solar evaporator. This structure is an integral part of the evaporator body, rather than an external attachment.

[0033] 2) Enhancement function and mechanism of air micro-convection:

[0034] This invention protects not only the structure but also the functions it provides. When the surface of the evaporator is heated by sunlight, the double-helix structure can utilize the surface height difference and local microenvironment differences created by the double-helix structure (temperature difference on the inner surface for double-helix grooves, and turbulence-blocking effect for double-helix protrusions) to guide and enhance airflow near the sidewalls, forming micro-vortices or directional rising and falling airflows. The intrinsic air micro-convection can actively disrupt and remove the air boundary layer stagnating in high-humidity air, reducing the saturated vapor pressure on the lateral surface, thereby significantly enhancing the evaporation rate of the lateral surface.

[0035] 3) Integrated construction of the evaporator body and side structure:

[0036] This invention protects a complete and integrated technical solution. That is, a solar evaporator with a columnar or conical body as the main body and a double-helix functional texture integrally constructed on its lateral surface; the scope of protection covers any evaporator with the above-mentioned "main body + lateral double-helix structure" feature manufactured by any means such as molding, 3D printing, mechanical etching, etc. Attached Figure Description

[0037] Figure 1 This is an external view of the cylindrical evaporator with a double-helix lateral structure according to the present invention;

[0038] Figure 2 This is a front view of the cylindrical evaporator with a double-helix lateral structure according to the present invention;

[0039] Figure 3 This is a rear view of the cylindrical evaporator with a double-helix lateral structure according to the present invention;

[0040] Figure 4 This is a side view of the cylindrical evaporator with a double-helix lateral structure according to the present invention;

[0041] Figure 5 This is a top view of the cylindrical evaporator with a double-helix lateral structure according to the present invention;

[0042] Figure 6 This is a physical image of the cylindrical evaporator with a double-helix lateral structure according to the present invention;

[0043] Figure 7 This is a flowchart illustrating the fabrication process of the cylindrical evaporator with a double-helix lateral structure according to the present invention.

[0044] Figure 8 This is a simulation cloud map of the air velocity distribution around a cylindrical evaporator with smooth sidewalls, as shown in a comparative embodiment of the present invention.

[0045] Figure 9 In a preferred embodiment of the present invention, a simulation cloud map of the air velocity distribution around a cylindrical evaporator with a double-helix lateral structure is provided.

[0046] Figure 10 This is a simulation cloud map of the air velocity distribution around a cone-shaped evaporator with smooth sidewalls, as shown in the comparative embodiment of the present invention.

[0047] Figure 11 In a preferred embodiment of the present invention, a simulation cloud map of the air velocity distribution around a conical evaporator with a double-helix lateral structure is provided.

[0048] Figure 12 This is a simulation cloud map of the evaporation rate distribution on the surface of a cylindrical evaporator with smooth sidewalls, as shown in the comparative embodiment of the present invention.

[0049] Figure 13 A simulation cloud map of the evaporation rate distribution on the surface of a cylindrical evaporator with a double-helix lateral structure, as shown in a preferred embodiment of the present invention.

[0050] Figure 14 This is a simulation cloud map of the evaporation rate distribution on the surface of a cone-shaped evaporator with smooth sidewalls, as shown in the comparative embodiment of the present invention.

[0051] Figure 15 In a preferred embodiment of the present invention, a simulation cloud map of the evaporation rate distribution on the surface of a conical evaporator with a double-helix lateral structure is shown. Detailed Implementation

[0052] The present invention will be further described below with reference to the accompanying drawings.

[0053] Example 1:

[0054] A solar evaporator with a double-helix lateral structure is prepared in two steps.

[0055] Step 1: Preparation process of photothermal materials

[0056] 1) Weigh 0.6 g of polyvinyl alcohol (PVA) powder (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) and 19.2 g of deionized water into a beaker. Place the beaker on a heat-collecting constant-temperature magnetic stirrer and stir continuously for 1 hour under a water bath at 75°C until the PVA powder is completely dissolved to obtain a colorless and transparent PVA solution.

[0057] 2) Subsequently, 0.2 g of dried nano-graphite powder (GNP, particle size D50 < 400 nm, metal matrix ≥ 99.95%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.) was added to the above PVA solution. The mixture was stirred for 30 minutes at a 75°C water bath to allow the graphite powder to be initially wetted and mixed. After stirring, the mixture was removed and subjected to ultrasonic dispersion treatment for 30 minutes using an ultrasonic cleaner to break up the agglomerates, ultimately obtaining a uniformly dispersed black PVA / GNP dispersion for later use.

[0058] It should be noted that the photothermal material of this invention is not limited to graphite powder, but also includes common photothermal materials such as polydopamine, carbon nanotubes (CNT), Mxene, carbon black, and metal nanoparticles. The binder is not limited to PVA. Any combination of materials that can form a photothermal layer should be within the scope of protection.

[0059] Step 2: Fabrication of a cylindrical evaporator with a double-helix lateral structure

[0060] A high-efficiency solar evaporator was fabricated using natural biomass material (King Oyster Mushroom) as a hydrophilic substrate. A macroscopic double-helix structure was constructed through mechanical processing, and combined with a photothermal functional coating. The specific fabrication steps are as follows:

[0061] 1) Formation of cylindrical biomass substrate

[0062] Fresh, dense king oyster mushrooms were selected as raw materials. Using a 4cm inner diameter stainless steel cylindrical cutting mold, the mushrooms were punched and cut along their growth direction to remove the outer skin and irregular parts, resulting in a standard cylinder with a diameter of 4cm. Subsequently, the ends were trimmed with a cutting blade to precisely control the height to 8cm, ensuring the top and bottom surfaces were flat, thus obtaining a smooth cylindrical biomass substrate.

[0063] It should be noted that although the embodiments of the present invention use king oyster mushroom (biomass substrate), the scope of protection covers porous ceramics, polymer foams (such as polyurethane, melamine foam), 3D printed polymer / hydrogel skeletons, wood and other materials with the same function.

[0064] 2) Construction of the lateral double helix macroscopic structure

[0065] Using a 5mm diameter semi-circular carving tool, manually carve the sidewalls of the cylindrical base. The specific carving path design is as follows:

[0066] 2.1) Select two symmetrical points (i.e., the central angles differ by 180°) on the edge of the top surface of the cylinder as the starting points of the double helix.

[0067] 2.2) Starting from the starting point, perform spiral cutting downwards along the side wall of the cylinder, with the cutting depth of the cutter being approximately 2.5 mm, forming a semi-circular groove with a width of 5 mm.

[0068] 2.3) The two spiral grooves continue to extend in an intersecting manner, and the spiral lines are distributed in a double spiral pattern.

[0069] 2.4) Control the pitch of the spiral so that each spiral groove rotates exactly 2 times around the side wall of the cylinder as it extends from the top to the bottom (i.e., the rotation angle is 720°).

[0070] Their structural diagrams are as follows: Figures 1-5 As shown.

[0071] It should be emphasized that the parameters in the above embodiments are "preferred parameters" of the present invention, not "limited parameters"; the pitch and number of rotations can be adjusted according to the height, and are not limited to 2 rotations; the cross-sectional shape of the groove is not limited to a semi-circle, but can also be V-shaped, U-shaped, rectangular, etc.

[0072] Step 3: Spraying the photothermal functional layer

[0073] The PVA / GNP black dispersion prepared in the preceding steps was loaded into a spraying device; the carved double-helix structured king oyster mushroom substrate was placed in a ventilated area, and the black dispersion was evenly sprayed onto the top surface and the entire side surface of the substrate using a spraying method. After spraying, the sample was allowed to air dry naturally at room temperature, thus obtaining a cylindrical solar evaporator with a double-helix side structure. A physical image of the evaporator of this invention is shown below. Figure 6 As shown, the preparation flowchart is as follows: Figure 7 As shown.

[0074] Working principle:

[0075] To verify the optimization mechanism of the double-helix lateral structure proposed in this invention on the airflow field around the evaporator, based on Example 1, fluid dynamics simulations were performed using COMSOL multiphysics simulation software under identical illumination, temperature, and ambient wind speed boundary conditions on a cylindrical evaporator with smooth sidewalls (comparative example) and a cylindrical evaporator with a double-helix lateral structure (this invention). The results are as follows: Figure 8 and Figure 9 As shown.

[0076] It should be noted that although this embodiment uses a "cylinder" as a typical representative of "columnar bodies" for demonstration, the fluid dynamics optimization mechanism it reveals—that is, perturbing the boundary layer through a lateral groove structure—is also applicable to other "columnar body" configurations such as square prisms and polygonal prisms.

[0077] The comparative analysis is as follows:

[0078] 1) Lateral flow field disturbance and boundary layer thinning: such as Figure 8 As shown, for an evaporator with smooth sides, the airflow near its sidewalls is relatively gentle and the flow velocity is low (dark blue area), indicating the formation of a thick air stagnation boundary layer that restricts the outward diffusion of water vapor. However, as... Figure 9 As shown, the double helix structure of the present invention significantly alters the flow field distribution near the sidewall. The groove structure induces significant air disturbance, making the high-velocity region (light blue to green region) closer to the evaporator surface. This enhanced lateral convection effectively disrupts and thins the originally stagnant air boundary layer.

[0079] 2.) Evolution of thermal plume morphology: Observing the flow field above both, it can be seen that the natural convection thermal plume formed above the smooth cylinder exhibits a narrow 'straight tube' shape, with limited ability to entrain surrounding air. In contrast, above the evaporator with a double helix structure, the thermal plume exhibits a distinctly divergent shape, and the range of the medium-to-high velocity region (green to red area) is significantly expanded.

[0080] Simulation results strongly demonstrate that the double-helix lateral structure can actively induce micro-air convection, significantly increase the airflow intensity on the sidewalls and top, thereby effectively reducing the local saturated vapor pressure at the gas-liquid interface.

[0081] To further verify the universality of the double-helix lateral structure described in this invention for different macroscopic geometries, this embodiment further performed the same fluid dynamics simulation analysis on an evaporator with a conical configuration. The results are as follows: Figure 10 and Figure 11 As shown.

[0082] Although a "cone" model is shown here, the flow field evolution law is also applicable to other "conical" structures such as pyramids, frustums, and squares, proving that the design of this invention has wide applicability.

[0083] The comparative analysis is as follows:

[0084] like Figure 10 As shown, for a conical evaporator with smooth sidewalls, the airflow is relatively smooth but has a low velocity when it rises along the smooth slope due to its geometry, and it converges into a very narrow rising hot plume at the top, indicating that its sidewalls have limited heat and mass exchange capacity with the surrounding air.

[0085] However, as Figure 11 As shown, the flow field changes significantly after a double-helix structure is introduced into the side of the cone. Similar to the case of the cylinder, the double-helix groove also induces strong air turbulence on the inclined surface (the light blue area expands significantly), effectively disrupting the laminar boundary layer on the sidewall. Simultaneously, observation of the top flow field reveals that the width and intensity of its rising thermal plume are significantly greater than... Figure 10 There is a significant increase (the medium-high velocity region from green to red has widened significantly).

[0086] This result fully demonstrates that the double-helix lateral structure of the present invention is not only applicable to cylinders, but also to other rotationally symmetric structures such as cones. Regardless of the base geometry, this structure can enhance air convection by actively perturbing the lateral flow field.

[0087] To visually demonstrate the actual improvement in evaporation performance brought about by the double-helix lateral structure, this embodiment further utilizes COMSOL software to numerically simulate the surface evaporation rate of the evaporators with the aforementioned different configurations. The simulation results are as follows: Figures 12 to 15 As shown in the figure, the colors from blue to red represent evaporation rates from low to high (normalized values).

[0088] 1) Evaporation rate analysis for columnar configuration ( Figure 12 , Figure 13 )

[0089] like Figure 12 As shown, for a cylindrical evaporator with smooth sidewalls, most of its side and top surfaces appear dark blue or light blue, indicating a low surface evaporation rate with a relatively uniform distribution and a lack of highly efficient evaporation zones.

[0090] In comparison, such as Figure 13 As shown, the cylindrical evaporator with a double-helix lateral structure exhibits distinctly different surface distribution characteristics. First, the central region of its top surface displays a large area of ​​bright red and yellow (high evaporation rate zone), indicating significantly enhanced evaporation at the top. Second, within the double-helix grooves on the sidewalls, the color is noticeably lighter than on the smooth sidewalls (changing from dark blue to light blue / cyan), indicating that localized evaporation within the lateral grooves is also effectively stimulated.

[0091] Software integral calculations show that, compared to a smooth cylinder, the overall evaporation rate of this double-helix cylindrical evaporator is increased by approximately 83%. This result not only verifies the effectiveness of the aforementioned flow field optimization but also demonstrates the significant potential of this structural design for improving the performance of various cylindrical evaporators, including cylindrical and square evaporators.

[0092] 2) Evaporation rate analysis for cone-shaped configuration ( Figure 14 , Figure 15 )

[0093] The same performance enhancement effect was replicated in the cone configuration.

[0094] like Figure 14 As shown, although the smooth cone exhibits a certain active yellow area in the middle region, its extent is limited. However, as... Figure 15As shown, the cone with a double helix structure has a significantly expanded high evaporation rate region (red / yellow) on its surface, which is clearly distributed along the helix structure, indicating that the helix structure effectively guides the airflow and enhances the mass transfer process along the path.

[0095] Software calculations show that under this operating condition, the overall evaporation rate of the double-helix conical evaporator is increased by approximately 50%. This further confirms that the macroscopic structural optimization strategy proposed in this invention has excellent universality and can significantly improve the water production efficiency of various conical evaporators, including cones and pyramids.

[0096] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the technical solutions of the present invention. Any technical solution that can be implemented based on the above embodiments without creative effort should be considered to fall within the scope of protection of the patent of the present invention.

Claims

1. A solar evaporator with a double-helix lateral structure, comprising a substrate with water absorption and transport functions, characterized in that, The substrate is a columnar or conical body, and the lateral outer wall surface of the substrate is provided with a double-helix lateral structure that can actively induce micro-air convection. The double-helix lateral structure is a double-helix groove or double-helix protrusion extending axially along the lateral surface of the substrate.

2. A solar evaporator with a double-helix lateral structure according to claim 1, characterized in that, The substrate is made of a material with hydrophilic and water-absorbing properties.

3. A solar evaporator with a double-helix lateral structure according to claim 1 or 2, characterized in that, The top surface and the entire side surface of the substrate are coated with a photothermal material layer.

4. A solar evaporator with a double-helix lateral structure according to claim 1, characterized in that, The double-helix lateral structure is a continuous or discontinuous structure extending from the top to the bottom of the substrate, or the double-helix lateral structure covers a portion of the side surface of the substrate.

5. A method for preparing a solar evaporator with a double-helix lateral structure, characterized in that, Includes the following steps: Step 1) Preparation of photothermal material: A photothermal material solution is prepared by mixing photothermal materials and binders in a certain proportion; Step 2) Fabrication of a solar evaporator substrate with a double-helix lateral structure: A solar evaporator substrate with a double-helix lateral structure is formed by using a hydrophilic and water-absorbing material and processing it into a columnar or conical shape. The substrate is then processed on the outer side wall of the columnar or conical shape using one or more methods, including subtractive manufacturing, additive manufacturing, and equal-material manufacturing. The double-helix lateral structure is a double-helix groove or double-helix protrusion extending axially along the lateral surface of the substrate. Step 3) Spraying the photothermal functional layer: The photothermal material prepared in step 1) is uniformly sprayed onto the outer surface of the solar evaporator substrate prepared in step 2); after spraying, it is dried; thus, a solar evaporator with a double helix lateral structure is obtained.

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