CN106915790B

CN106915790B - Liquid-filled flexible light-gathering underwater solar seawater desalination device

Info

Publication number: CN106915790B
Application number: CN201710165845.XA
Authority: CN
Inventors: 张楠; 郑宏飞; 陶涛; 王秋实
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2017-03-20
Filing date: 2017-03-20
Publication date: 2020-01-21
Anticipated expiration: 2037-03-20
Also published as: CN106915790A

Abstract

The invention discloses a liquid-filled flexible light-condensing underwater solar seawater desalination device, and belongs to the technical field of solar heat collection and seawater desalination. The main device comprises: the system comprises a liquid-filled flexible condenser, a flask-type vacuum heat collecting pipe, a liquid level balance pipe, a self-siphon condenser, a fresh water collector and a one-way valve. And a liquid-filled flexible condenser is utilized to refract incident light twice, converge the refracted incident light on the surface of the outer tube of the flask type vacuum heat collecting tube and absorb the refracted incident light by the selective absorption coating on the outer surface of the inner tube for the third time. The fresh seawater is heated to evaporate, and the water vapor meets condensation knots on the outer surface of the condensation section of the self-siphon condenser and flows into the fresh water collecting device along the outer surface of the condensation pipe. The collected fresh water can be taken out by the one-way valve.

Description

Liquid-filled flexible light-gathering underwater solar seawater desalination device

Technical Field

The invention belongs to the technical field of solar energy condensation and seawater desalination and utilization. In particular to a novel structure formed by combining a liquid-filled flexible condenser and seawater desalination.

Background

The vast majority of water on earth is stored in the ocean almost exclusively. Water on the earth is changed into water vapor to be evaporated into the air after being irradiated by sunlight, the water vapor is condensed into small water drops when meeting cold air at high altitude, the small water drops form clouds, and finally the water drops fall on the land to form fresh water for human use. Solar desalination is a basic way for the nature to produce fresh water. The solar energy desalination can better take energy and water source requirements into consideration, save energy, protect environment, form huge economic and environmental benefits, help to solve the drinking water problems in regions such as bitter and salty water areas and isolated islands in rural areas in China, and help to promote the development of desalination technology in China. At present, the condenser of the solar seawater desalination system in China mainly takes a hard solar heat collector as a main part and is mostly installed on land, so that the occupied area is large, and the pressure on the land is not easy to relieve. The sand blown by the wind also has certain influence to the spotlight effect, is unfavorable for the dismouting, needs extra device extraction sea water scheduling problem.

In order to solve the contradictions and fully utilize the ocean area, a liquid-filled flexible light-gathering underwater seawater desalination device is designed. The underwater solar seawater desalination is realized according to the underwater geometric optics principle.

Disclosure of Invention

In view of this, the present invention provides a seawater desalination system based on the combination of a liquid-filled condenser and a flask-type evacuated collector tube, which directly generates fresh water by using solar energy. The system can refract and condense underwater solar energy in the forward direction, and the whole device can automatically generate fresh water completely, so that the system has the characteristics of high heat collection efficiency and high yield.

The invention relates to an underwater solar seawater desalination system based on a liquid-filled condenser, which mainly comprises the following devices: the system comprises a liquid-filled flexible condenser, a flask-type vacuum heat collecting pipe, a liquid level balance pipe, a self-siphon condenser, a fresh water collector, a one-way valve, a water-proof breathable film and a fresh water guide pipe.

The technical scheme adopted by the invention for solving the technical problems is as follows:

the liquid-filled flexible condenser is deformed into a shape similar to a dish Fresnel lens after liquid filling. The interior is filled with a liquid having a refractive index greater than that of seawater. After the light is refracted twice on the upper surface and the lower surface of the condenser, the light is received by a flask type vacuum heat collecting tube arranged at the lower end of the liquid-filled flexible condenser, a light plate is formed on the surface of the heat collecting tube, and seawater in the heat collecting tube is heated to evaporate the seawater. The steam goes upward to pass through the waterproof and breathable film to fill the upper space of the whole flask type vacuum heat collecting tube and is arranged on the outer wall of the spiral condensing tube of the self-siphon condenser. The seawater in the condenser is automatically circulated under the action of left and right temperature difference. The lower end of the liquid level balance tube extends into the interior of the heat collecting tube below the free liquid level, and the upper end of the liquid level balance tube extends out through a small hole formed in the sealing end of the upper portion of the heat collecting tube to keep the liquid level balance. The evaporated seawater falls on the water-proof and breathable film under the action of gravity, and based on the characteristic that the seawater cannot pass through the water-proof and breathable film, the fresh water flows into the fresh water draft tube to form a liquid film, and finally flows into the fresh water collector to be collected.

The working principle is as follows:

the liquid-filled flexible condenser can be filled with liquid with different pressures, so that the liquid-filled flexible condenser adapts to the pressures of different depths and keeps stable shape and focal length. When sunlight passes through the upper surface of the liquid-filled flexible condenser, seawater with a relatively small refractive index enters a liquid filled body with a relatively large refractive index, so that refraction with a refraction angle smaller than an incidence angle is generated. Then the liquid with relatively large refractive index is injected into the substance with relatively small refractive index through the lower surface to be refracted by the refraction angle larger than the incidence angle, so that the forward refraction and condensation are realized. The condensed light is emitted to the spherical structure of the vacuum heat collecting tube. The flask type is designed because the refractive index of seawater is larger than vacuum, and the seawater cannot be absorbed by the selective absorption film to prevent total reflection due to the incident angle of light being larger than or equal to the critical angle.

The height of the free liquid level in the cavity is controlled by a liquid level balance pipe, and the lower end of the balance pipe is positioned below the spherical structure of the heat collecting pipe and below the free liquid level. The liquid level is just above and below the beginning of the spherical structure under the action of pressure balance. The light is absorbed by the selective absorption film on the outer surface of the high-temperature inner tube, the surface temperature of the inner tube rises continuously, the high-temperature inner tube heats the seawater in the cavity, and water vapor is generated at the free liquid level. The water vapor ascends through the water-proof breathable film and fills the whole area above the water-proof breathable film. The self-siphoning condenser is filled with seawater under water, and the seawater in the condenser is kept stable before the whole system is not operated. The upward water vapor contacts with the outer surface of the spiral condensing pipe section filled with cold seawater and is condensed into liquid drops on the surface, and the liquid drops fall under the action of gravity. Part of fresh water directly enters the fresh water guide pipe, part of the fresh water falls on the water-proof breathable film, and the characteristic of the film shows that water cannot permeate through the film and then flows into the fresh water guide pipe along the gradient of the film to form a liquid film. Finally, the fresh water enters a fresh water collector to collect the fresh water.

The seawater in the spiral condensation section in the self-siphon condenser is heated due to condensation heat release, the density is reduced, and the seawater with higher temperature rises along the spiral condensation pipe due to the effect of buoyancy. Therefore, the seawater in the seawater eduction pipe and the seawater at the outlet of the effluent pipe generate pressure difference, and the seawater at the inlet of the seawater eduction pipe and the seawater in the pipe generate pressure difference, thereby realizing self-siphoning. The part above the outlet of the seawater eduction tube is wrapped by the heat insulation layer to control the water temperature in the seawater eduction tube to be less than the water temperature in the condensation tube, thereby ensuring normal circulation. The condensing speed is controlled to be greater than or equal to the evaporating speed so as to maintain the pressure in the cavity.

Further, the self-siphon condenser in the flask-type evacuated collector tube is replaced by an external spherical condenser, and the position of the fresh water collector is changed.

Furthermore, the groove type Fresnel lens liquid-filled flexible condenser is replaced by a convex lens type liquid-filled flexible condenser.

Furthermore, the liquid-filled flexible condenser is designed into a lens shape with the upper surface being approximately step-shaped after liquid filling.

Has the advantages that:

(1) the invention is beneficial to relieving land pressure, makes full use of ocean area and eliminates the influence of sand blown by the wind on the light condensation effect. Meanwhile, a new idea is provided for how to utilize the undersea solar energy.

(2) The invention can converge the solar beam with low energy flow density into the focal spot with high energy flow density, and the focal spot is arranged below the light gathering device, thereby realizing refraction type forward focusing, so that the heat receiver can be arranged below the light gathering device to be beneficial to the receiver to receive and convert the sunlight, thereby realizing high-temperature energy gathering, and bringing convenience to the design, installation, debugging and maintenance of the receiving device.

(3) The invention has simple and compact structure and can be used in scale. All parts of the whole device comprise a liquid-filled flexible condenser, a flask type vacuum heat collecting pipe, a condenser pipe and the like which are regularly arranged in one area, so that the whole system has a very compact structure, is easy to process and produce in a standardized way and has low manufacturing cost. The device can form a large-scale seawater desalination system by arrangement and combination, thereby realizing the large-scale and low-cost popularization and application of the undersea solar seawater desalination system.

(4) The invention breaks through the inertial thinking of the conventional hard condenser, provides a novel concept of the liquid-filled flexible condenser, and provides a new thought and direction for the design of the condenser in the future.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic diagram of the operation of the optical path of the present invention;

FIG. 3 is a schematic diagram of the operation of the present invention;

FIG. 4 shows an embodiment of the condensing unit of the present invention as a spherical condenser;

FIG. 5 is an embodiment of the liquid-filled flexible concentrator of the present invention designed to be convex lens shaped;

fig. 6 shows that the liquid-filled flexible condenser of the present invention has a lens shape with an approximately step-shaped upper surface after liquid filling.

Wherein 1, the liquid-filled flexible condenser; 2-a transparent film; 3-a transparent plate; 4-self-siphoning condenser; 5-flask type vacuum heat collecting tube; 6-high temperature inner tube; 7, a heat insulation layer; 8, water-proof and air-permeable films; 9-pulling the rope; 10-fresh water collector; 11-a one-way valve; 12-a fixed ring; 13-a perforated support; 14-fresh water draft tube; 15-a selective absorption membrane; 16-opening; 17-the liquid filled; 18-transparent support 19-liquid level balance tube; 20-incident light; 21-normal light; 22-condenser focal point; 23-refracting light; 24-circulating the seawater; 25-free liquid level; 26-raw seawater; 27-fresh water; 28-condensate film; 29-coalesce the droplets.

The specific implementation mode is as follows:

the invention is described in detail below by way of example with reference to the accompanying drawings.

The invention provides an underwater solar seawater desalination system based on a liquid-filled condenser. The device mainly comprises: the device comprises a liquid-filled flexible condenser 1, a self-siphon condenser 4, a flask-type vacuum heat collecting pipe 5, a high-temperature inner pipe 6, a heat insulating layer 7, a water-proof and air-permeable film 8, a fresh water collector 10, a one-way valve 11, a fresh water draft tube 14, a selective absorption film 15 and a liquid level balance pipe 19.

The liquid-filled flexible condenser 1 is arranged at the uppermost part of the whole device, and a pulling rope 9 connected with a fixed ring 12 on a fresh water collector 10 is connected on the liquid-filled flexible condenser to fix the position of the liquid-filled flexible condenser. The lower end opening of the flask type vacuum heat collecting pipe 5 and the focal plane are positioned on the same horizontal plane and fixed by an open pore bracket 13 connected with a fresh water collector 10. The self-siphon condenser 4 is arranged in the flask type vacuum heat collecting tube 5 in an inverted mode, the seawater inlet section at the lower end passes through the fresh water guide pipe 14 and is led out from the opening at the lower half part of the fresh water guide pipe, the other side is attached with the heat insulation layer 7 and is led out from the lower part of the flask type vacuum heat collecting tube 5, and the water inlet and the water outlet are kept flush. The condensed liquid drops drop onto the concave water-proof and breathable film 8 and flow into the fresh water draft tube 14, and finally enter the lower fresh water collector 10. The liquid level balance tube 19 extends from the free liquid level 25 through the interior of the flask type vacuum heat collecting tube 5 and finally through an opening at the upper sealed end.

The operation principle and distribution of the device are explained as follows, as shown in figures 1 and 3:

the parallel incident light 20 is incident along the vertical direction, most of the light is refracted twice through the liquid-filled flexible condenser 1 and the liquid 17 filled in the condenser, and the light is incident on the flask-type evacuated collector tube 5, wherein most of the light is incident on the spherical area of the flask-type evacuated collector tube 5. The light rays are refracted for the third time on the surface of the outer tube of the flask type vacuum heat collecting tube, are incident on the outer wall surface of the high-temperature inner tube 6, and are absorbed by the selective absorption film 15 on the wall surface. Therefore, the temperature of the high-temperature inner pipe 6 is gradually increased, the raw seawater 26 in the inner cavity is heated, the temperature of the raw seawater 26 is gradually increased, and the free liquid level 25 begins to generate steam and increase continuously. The high-temperature steam goes upward to pass through the waterproof breathable film 8, is condensed on the surface of the spiral condensation pipe of the self-siphon condenser 4 to form condensed liquid drops 29, and forms a condensed liquid film 28 through the fresh water draft tube 14 under the action of gravity, and then flows into the fresh water collector 10 to collect fresh water 27. And finally may be led out by the non-return valve 11.

Fig. 2 is a schematic diagram of the optical path of the present invention. It was further analyzed using optical principles. The incident light ray 20 first reaches the upper surface of the liquid-filled flexible concentrator 1, refracted at an angle of refraction less than the angle of incidence due to the liquid 17 having a refractive index greater than that of seawater, and then reaches the lower surface of the concentrator, refracted at an angle of refraction greater than the angle of incidence also due to the liquid 17 having a refractive index greater than that of seawater. Incident light rays refracted twice are received by the outer surface of the flask-type vacuum heat collecting tube 5, and most of the incident light rays form effective light spots in a spherical area. Because the surface of the spherical area is arc-shaped, compared with the conventional vacuum heat collecting tube, the solar vacuum heat collecting tube reduces the incident angle, thereby effectively avoiding the total reflection of light. Allowing more light to be absorbed by the selectively absorbing film 15 on the outer wall of the high temperature inner tube 6. The incident light undergoes a third refraction and is finally absorbed by the selective absorption film 15.

In one embodiment as shown in fig. 4, the self-siphon condenser 4 is replaced by an external spherical condenser 4, and the water vapor evaporated by heating rises into a steam channel wrapped by the heat-insulating layer under the action of pressure difference so as to smoothly enter the spherical condenser. The water vapor is condensed in the condenser and enters the fresh water collector along the fresh water draft tube. The replacement and installation are more convenient.

In one embodiment shown in fig. 5, the liquid-filled flexible condenser 1 is designed as a convex lens type condenser, so that the whole condenser is flexible and does not need a support, and the manufacturing process requirement is lower.

In one embodiment shown in fig. 6, the liquid-filled flexible condenser is deformed into a lens shape with an approximately step-shaped upper surface after being filled with liquid, and the transparent thin plates which can be fixed by mutual hinges support the thin film, so that the liquid-filled flexible condenser has a better light-collecting effect on obliquely incident light.

In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A liquid-filled flexible light-gathering underwater solar seawater desalination device is characterized by comprising a liquid-filled flexible light gathering device 1, a self-siphon condenser 4, a flask-type vacuum heat collecting tube 5, a water-proof and breathable film 8, a fresh water collector 10, a fresh water diversion tube 14 and a liquid level balance tube 19;

wherein the liquid-filled flexible condenser 1 is arranged at the uppermost part of the whole device, and is connected with a traction rope 9 connected with a fixed ring 12 on a fresh water collector 10 so as to fix the position of the liquid-filled flexible condenser; the lower end opening of the flask type vacuum heat collecting pipe 5 and the focal plane are positioned on the same horizontal plane and fixed by an open pore bracket 13 connected with a fresh water collector 10; the self-siphon condenser 4 is arranged in the flask type vacuum heat collecting tube 5 in an inverted mode, the seawater inlet section at the lower end passes through the fresh water guide pipe 14 and is led out from the opening at the lower half part of the fresh water guide pipe, the other side is attached with the heat insulating layer 7 and is led out from the lower part of the flask type vacuum heat collecting tube 5, and the water inlet and the water outlet are kept flush; the condensed liquid drops drop onto the concave water-proof and breathable film 8 and flow into the fresh water draft tube 14, and finally enter the lower fresh water collector 10; the liquid level balance tube 19 extends from the free liquid level 25 through the interior of the flask type vacuum heat collecting tube 5 and finally through an opening at the upper sealed end.

2. The liquid-filled flexible light-concentrating underwater solar seawater desalination device of claim 1, wherein the upper surface of the liquid-filled flexible light concentrator 1 is a transparent flexible film 2, the bottom surface is a transparent plate 3, and the vertical side and the horizontal side of the bottom surface are hinged to enable the bottom surface to be folded; a transparent porous support 18 hinged with the inward convex hinged part of the lower surface is arranged in the condenser, and the upper end of the transparent porous support is bonded with the transparent flexible film 2, so that the shape of the condenser after liquid filling is similar to that of a dish Fresnel lens; the liquid with refractive index larger than that of sea water is filled in the container.

3. The liquid-filled flexible concentrating underwater solar seawater desalination device of claim 1, wherein the self-siphon condenser 4 is similar to a U-shaped tube and comprises a seawater introduction section, a spiral condensation section and a seawater discharge section with a heat insulation layer 7; the seawater guide section is connected with the seawater guide section and positioned at one side, and the part above a water-proof outlet of a seawater guide pipe at the other side is wrapped by a heat insulation layer 7 so as to control the water temperature in the seawater guide pipe to be lower than that in the condensation section, thereby ensuring the normal circulation of the seawater in the pipe; the inlet and outlet of the lower part of the self-siphon condenser 4 are on the same horizontal line.