A spiral eddy current anti-bending and explosion-proof trough type solar heat collecting tube and method

Abstract

The present invention discloses a spiral vortex anti-bending and explosion-proof trough type solar heat collecting tube and method, comprising: a vacuum glass outer tube, which is sleeved on the outermost periphery of the solar heat collecting tube; a stainless steel inner tube, which is embedded in the interior of the vacuum glass outer tube through an expansion joint at the end, and a vacuum area is formed between the stainless steel inner tube and the vacuum glass outer tube; a heat absorbing coating, which is coated on the outer wall of the stainless steel inner tube; and a spiral mixer, which is penetrated into the interior of the stainless steel inner tube to form a vortex. The spiral vortex anti-bending and explosion-proof trough type solar heat collecting tube and its anti-bending and explosion-proof method of the present invention have significant advantages in improving thermal efficiency, solving the problem of bending and explosion of tubes, and improving safety, and are helpful to improve the performance and operation stability of heat collecting tubes in trough type solar mirror fields.

Description

Technical Field

[0001] The invention relates to a solar heat collecting tube, in particular to a spiral eddy current anti-bending and explosion-proof trough type solar heat collecting tube and method. Background Art

[0002] Trough-type solar collector tubes are one of the most important components in the heat collection system. During the operation of the collector tubes, local temperature changes will affect them, resulting in upper and lower temperature difference layers of the heat transfer oil in the collector tubes. The formation of this temperature difference layer may lead to differences in the expansion of the collector pipelines, thereby causing bending. Bending will affect the collector tube's interception effect on the reflector light spot, thereby reducing the heat collection efficiency. Severe bending may even cause the outer high-boron glass tube to burst, making the collector tube unusable, thereby affecting the normal operation of the entire system.

[0003] Especially in the case of dual-axis trough solar collectors, the initial tilt angle in the morning is too large, the bending rate can be as high as 100% during startup, and the risk of tube burst is as high as more than 70%. Therefore, the bending problem has always been a global problem that has plagued the trough solar industry, and no effective solution has been found so far. Summary of the invention

[0004] In order to solve the deficiencies of the above-mentioned technologies, the present invention provides a spiral vortex anti-bending and explosion-proof trough type solar energy collector tube and method.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a spiral vortex anti-bending and explosion-proof trough type solar collector tube, comprising:

[0006] The vacuum glass outer tube is placed on the outermost periphery of the solar heat collecting tube;

[0007] The stainless steel inner tube is embedded in the vacuum glass outer tube through an expansion joint at the end, and a vacuum zone is formed between the stainless steel inner tube and the vacuum glass outer tube;

[0008] A heat absorbing coating is applied to the outer wall of the stainless steel inner tube;

[0009] The spiral mixer is installed inside the stainless steel inner tube to form a vortex.

[0010] Furthermore, the spiral mixer includes continuous spiral blades, and the ratio coefficient between the interval area of ​​the spiral blades and the diameter area of ​​the stainless steel inner tube is:

[0011] K = A_spacing / A_pipe;

[0012] Among them, K is the proportional coefficient, A_spacing is the spacing area of ​​the spiral blades, and A_pipe is the diameter area of ​​the stainless steel inner pipe.

[0013] Furthermore, the calculation formula of the helix angle of the spiral blade is:

[0014] tan(α)=V_tan / V_axial;

[0015] Among them, tan(α) is the helix angle, V_tan is the tangential velocity, and V_axial is the axial velocity.

[0016] Furthermore, the calculation formula of the pitch of the spiral blade is:

[0017] P = tan(α)*D;

[0018] Among them, P is the pitch and D is the diameter of the stainless steel inner tube.

[0019] Furthermore, the calculation formula for the number of blade heads of the spiral blade is:

[0020] N = f*Reynolds_number;

[0021] Among them, N is the number of blades, f is the adjustment parameter, and Reynolds_number is the Reynolds number.

[0022] Furthermore, the expansion joint is made of a flexible material or a rigid material, and the end of the stainless steel inner tube is inserted into the interior of the vacuum glass outer tube through the expansion joint.

[0023] Furthermore, the spiral outer edge of the spiral blade or a part of the spiral blade is connected to the inner wall of the stainless steel inner tube so that the spiral mixer is penetrated inside the stainless steel inner tube.

[0024] Furthermore, an external thread or an internal thread hole is provided on the expansion joint at the front end of the stainless steel inner tube, and an internal thread hole matching the external thread or an external thread matching the internal thread hole is provided on the expansion joint at the rear end of the stainless steel inner tube to achieve a threaded connection between two different sections of solar collector tubes.

[0025] The invention discloses a method for preventing bending and explosion of a spiral eddy current anti-bending and explosion-proof trough type solar collector tube. The method adopts a spiral eddy current state to replace a direct current laminar flow state to eliminate the radial upper and lower temperature difference of the solar collector tube to solve the problem of tube bending and explosion.

[0026] Furthermore, the spiral vortex state replaces the direct current laminar flow state by utilizing a spiral mixer to form a vortex state in the stainless steel inner tube, so as to replace the direct current laminar flow state to eliminate the radial upper and lower temperature difference of the solar energy collector tube. The heat-absorbing coating is applied on the outer wall of the stainless steel inner tube to absorb heat energy in the spiral vortex state, and a vacuum zone is formed between the vacuum glass outer tube and the stainless steel inner tube, thereby improving the thermal efficiency of the collector tube and reducing the risk of pipeline explosion.

[0027] The present invention discloses a spiral vortex anti-bending and explosion-proof trough type solar heat collecting tube and method, which has the following advantages:

[0028] 1. Solve the problem of bending and bursting of pipes: The spiral mixer is used to form a vortex state in the heat collecting pipe, replacing the direct current laminar flow state, eliminating the temperature difference between the upper and lower parts of the heat collecting pipe, thereby avoiding the bending, deformation and bursting of the heat collecting pipe and ensuring the stable operation of the heat collecting pipe.

[0029] 2. Improve thermal efficiency: The design and optimization of the heat-absorbing coating can effectively absorb sunlight and convert it into thermal energy. Combined with the formation of a spiral vortex state, it improves the thermal efficiency of the collector tube and increases the conversion rate of thermal energy.

[0030] 3. Stable structural design: The application of expansion joints effectively handles the problem of thermal expansion and contraction, ensuring that the collector tube will not be damaged when the temperature changes, and maintaining structural stability.

[0031] 4. Improved explosion-proof performance: A vacuum zone is formed between the vacuum glass outer tube and the stainless steel inner tube to reduce the risk of pipeline explosion and improve the safety of the collector tube.

[0032] 5. Customized design: According to the specific application and design requirements, the parameters such as spiral blade spacing area, spiral angle, pitch and number of blades can be adjusted to make the collector more adaptable to different working conditions and have certain flexibility and customizability. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of the present invention.

[0034] Figure 2 It is a schematic diagram of the three-dimensional structure of the present invention.

[0035] Figure 3 It is a schematic diagram of the operating status of the solar heat collecting tube in the prior art.

[0036] Figure 4 It is a schematic diagram of the operating state of the solar heat collecting tube of the present invention.

[0037] In the figure: 1. Vacuum glass outer tube; 2. Stainless steel inner tube; 3. Heat-absorbing coating; 4. Spiral mixer; 5. Expansion joint. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0039] Spiral vortex anti-bending and explosion-proof trough solar collector tube is used in trough solar mirror field, such as Figure 3The following problems exist in the use of solar heat collecting tubes in the prior art shown as follows: The trough solar mirror field is mainly composed of parabolic reflectors and solar heat collecting tubes. The parabolic reflectors focus the solar reflected beams of sunlight on the heat collecting tubes. When in use, a light spot band is generated at the lower part of the heat collecting tube, which forms a 20-40mm reflector heat collecting light spot after focusing. According to the different openings of the reflectors, the temperature of the light spot band is 300-800℃. The circulating medium (water, heat transfer oil, molten salt, etc.) inside the heat collecting tube takes out the heat and sends it to the working condition for use. During use, the lower spot of the collector tube is heated unilaterally. Although the medium in the tube flows in a direct current state and takes away a certain amount of heat, the flowing medium is in a laminar flow state. The lower part of the medium in the tube is hot to form a hot flow layer, while the upper part is cool to form a cold flow layer. A temperature difference is formed between the upper and lower parts, resulting in uneven heating of the stainless steel tube radially upward and downward, and inconsistent linear expansion, which causes the collector tube to bend and deform. Especially in the initial operation, the oil temperature difference is large and the deformation is large. The bending of the steel tube will break the outer glass tube, causing the tube to burst, which seriously affects the normal operation of the collector.

[0040] like Figure 1 and Figure 2 As shown, the present invention discloses a spiral vortex anti-bending and explosion-proof trough type solar heat collecting tube, comprising:

[0041] The vacuum glass outer tube 1 is sleeved on the outermost periphery of the solar heat collecting tube;

[0042] The stainless steel inner tube 2 is embedded in the vacuum glass outer tube 1 through an expansion joint 5 at the end, and a vacuum zone is formed between the stainless steel inner tube 2 and the vacuum glass outer tube 1;

[0043] A heat absorbing coating 3 is applied on the outer wall of the stainless steel inner tube 2;

[0044] The spiral mixer 4 is arranged inside the stainless steel inner tube 2 to form a vortex.

[0045] The spiral outer edge of the spiral blade or a part of the spiral blade is connected to the inner wall of the stainless steel inner tube 2 to realize that the spiral mixer 4 is penetrated inside the stainless steel inner tube 2. The expansion joint 5 at the front end of the stainless steel inner tube 2 is provided with an external thread or an internal thread hole, and the expansion joint 5 at the rear end of the stainless steel inner tube 2 is provided with an internal thread hole matched with the external thread or an external thread matched with the internal thread hole, so as to realize the threaded connection between two different sections of solar collector tubes.

[0046] The composition of the heat-absorbing coating may vary according to the specific application and design requirements. Different types of heat-absorbing coatings may use different material combinations. In this embodiment, the absorbing material is the main component of the heat-absorbing coating, which is used to absorb sunlight and convert it into heat energy. Heat-absorbing materials with high absorptivity and thermal conductivity, such as black dyes, oxides, and metal particles, are used. At the same time, the base material is used as the supporting material of the heat-absorbing coating to provide structural support and fixation of the coating. The base material uses a metal substrate, a glass substrate, a ceramic substrate, etc., which have certain high temperature resistance and mechanical strength. In addition, some auxiliary components can be used to improve the performance and stability of the coating, such as adding anti-corrosion agents and additives to enhance adhesion.

[0047] The composition of the heat-absorbing coating is designed to improve sunlight absorption, thermal conductivity and stability to achieve efficient solar heat conversion.

[0048] When the diameter of the stainless steel inner tube is 1 square meter, the area between the spiral blades is between 2-5 square meters; the spiral blade helix angle is between 20° and 45°; the pitch will interact with the spiral blade helix angle, which is between 0.2 meters and 0.5 meters; the specific setting of the number of blade heads needs to consider factors such as fluid properties and flow rate, and in this embodiment, it is between 3 and 8.

[0049] The ratio of the spiral blade spacing area (A_spacing) to the stainless steel inner pipe diameter area (A_pipe):

[0050] A_spacing = k*A_pipe;

[0051] Among them, k is the proportionality coefficient, which is between 2 and 5.

[0052] The selection of the helical blade helix angle (α) takes into account the flow of the fluid on the blade, and the formula is:

[0053] tan(α)=V_tan / V_axial;

[0054] Among them, V_tan is the tangential velocity and V_axial is the axial velocity.

[0055] The pitch (P) is affected by the helix angle of the spiral blade and is calculated based on the flow characteristics of the fluid and the geometry of the blade:

[0056] P = tan(α)*D;

[0057] Wherein, D is the diameter of the stainless steel inner tube.

[0058] The selection of the number of blade heads (N) will take into account the balance between heat transfer effect and fluid mixing effect, and will be adjusted according to specific needs and fluid properties to ensure that the selection of the number of blade heads can achieve a balance between heat transfer effect and mixing effect:

[0059] N = f*Reynolds_number;

[0060] Where f is the adjustment parameter and Reynolds_number is the Reynolds number. In the selection of the number of blade heads (N), the adjustment parameter f is used to adjust the number of blade heads according to specific needs and fluid properties to achieve a balance between heat transfer effect and fluid mixing effect. The adjustment parameter f is an indefinite value. Refer to the following parameters to make corresponding adjustments in combination with specific heat exchange equipment, application requirements and fluid properties:

[0061] Geometric parameters: The geometric parameters such as the shape and inclination of the blades will affect the flow state and mixing effect of the fluid around the blades. Blade spacing: The spacing between the blades also affects the flow, turbulence and mixing effect of the fluid.

[0062] Fluid property parameters: The viscosity of the fluid will directly affect the flow characteristics and force of the fluid, thus affecting the stirring and mixing effect of the blades on the fluid. The density of the fluid will also affect the flow performance and heat transfer characteristics of the fluid, thus affecting the selection of the number of blades.

[0063] Operating parameters: The flow rate of the fluid will affect the flow state, turbulence and convective heat transfer effect, which in turn affects the number of blades. The fluid temperature also has a certain impact on the heat exchange effect, heat transfer rate, etc., so it needs to be considered when selecting the number of blades.

[0064] In the present invention, the expansion joint is used to deal with the problem of thermal expansion and contraction to ensure that the solar collector tube will not be damaged when the temperature changes. The expansion joint will be embedded in the inside of the vacuum glass outer tube to form a vacuum area between the vacuum glass outer tube and fix the stainless steel inner tube at the same time.

[0065] The expansion joint can be made of flexible materials, such as rubber, polyurethane, metal bellows, polytetrafluoroethylene (PTFE), silicone, but not limited to the above materials. The expansion joint plays a buffering role when the temperature changes. The expansion joint embedded in the vacuum glass outer tube will form a certain gap with the inner wall of the outer tube, so that the expansion joint can expand and contract freely while maintaining the sealing state of the vacuum zone.

[0066] During the installation process, the stainless steel inner tube will be inserted into the vacuum glass outer tube through the expansion joint at the end, and ensure that there is enough gap between the expansion joint and the inner wall of the outer tube to form a stable structure. This design can effectively prevent the collector tube from bending or bursting when the temperature changes, while ensuring the normal operation and thermal efficiency of the collector tube.

[0067] The expansion joint can also be made of rigid materials, such as stainless steel, carbon steel, alloy steel or aluminum alloy. Because the design of the solar collector tube is to make it anti-bending, the expansion joint has a basis for using rigid materials. The problem of bursting needs to be solved by using a vacuum glass outer tube with good explosion-proof performance.

[0068] like Figure 4 As shown, a spiral mixer device is welded inside the stainless steel tube, that is, the medium enters the heat collecting tube, and the original flow of the medium is changed to a linear state, and the spiral flow along the tube wall is changed to a turbulent state through the spiral mixer, forcing the upper and lower different media of the original laminar flow to mix and flow together to form a cold and hot mixed flow medium, and the light spot heating part formed by the reflected light beam from the sun is transferred to the surrounding wall of the heat collecting tube. The temperature of the entire upper and lower tube walls is uniform, the linear expansion is consistent, there is no local heating, and no bending occurs, thereby completely solving the problem of bent tubes and bursting tubes.

[0069] At the same time, the present invention discloses a method for preventing bending and explosion of a spiral vortex anti-bending and explosion-proof trough-type solar collector tube. The method for preventing bending and explosion is to replace the direct current laminar flow state with a spiral vortex state to eliminate the radial upper and lower temperature difference of the solar collector tube to solve the problem of tube bending and explosion. The spiral vortex state replaces the direct current laminar flow state by using a spiral mixer 4 to form a vortex state in the stainless steel inner tube 2 to replace the direct current laminar flow state to eliminate the radial upper and lower temperature difference of the solar collector tube. The heat-absorbing coating 3 is applied on the outer wall of the stainless steel inner tube 2 to absorb heat energy in the spiral vortex state. A vacuum zone is formed between the vacuum glass outer tube 1 and the stainless steel inner tube 2 to improve the thermal efficiency of the collector tube and reduce the risk of pipeline explosion.

[0070] The above implementation modes are not limitations of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the scope of the technical solution of the present invention also belong to the protection scope of the present invention.

Claims

1. A spiral vortex anti-bending and explosion-proof trough type solar collector tube, characterized in that: include: A vacuum glass outer tube, which is sleeved on the outermost part of the solar heat collecting tube; A stainless steel inner tube is embedded in the vacuum glass outer tube through an expansion joint at the end thereof, and a vacuum zone is formed between the stainless steel inner tube and the vacuum glass outer tube; A heat-absorbing coating is coated on the outer wall of the stainless steel inner tube; A spiral mixer is arranged inside the stainless steel inner tube to form a vortex; The spiral mixer comprises continuous spiral blades, and the ratio coefficient between the interval area of ​​the spiral blades and the diameter area of ​​the stainless steel inner tube is: K = A_spacing / A_pipe; Among them, K is the proportional coefficient, A_spacing is the spacing area of ​​spiral blades, and A_pipe is the diameter area of ​​the stainless steel inner pipe; The calculation formula of the helix angle of the spiral blade is: tan(α) = V_tan / V_axial; Among them, tan(α) is the helix angle, V_tan is the tangential velocity, and V_axial is the axial velocity; The calculation formula of the pitch of the spiral blade is: P = tan(α) * D; Among them, P is the pitch, and D is the diameter of the stainless steel inner tube; The calculation formula of the number of blades of the spiral blade is: N = f * Reynolds_number; Where N is the number of blades, f is the adjustment parameter, and Reynolds_number is the Reynolds number; The proportional coefficient K is between 2-5. When the diameter of the stainless steel inner tube is 1 square meter, the spacing area of ​​the spiral blades is between 2-5 square meters; the spiral blade helix angle is between 20° and 45°; the pitch will interact with the spiral blade helix angle and is between 0.2 meters and 0.5 meters.

2. The spiral vortex anti-bending and explosion-proof trough type solar collector tube according to claim 1 is characterized in that: The expansion joint is made of a flexible material or a rigid material, and the end of the stainless steel inner tube is inserted into the interior of the vacuum glass outer tube through the expansion joint.

3. The spiral vortex anti-bending and explosion-proof trough type solar collector tube according to claim 2 is characterized in that: The spiral outer edge of the spiral blade or a part of the spiral blade is connected to the inner wall of the stainless steel inner tube so that the spiral mixer is penetrated inside the stainless steel inner tube.

4. The spiral vortex anti-bending and explosion-proof trough type solar collector tube according to claim 1 is characterized in that: The expansion joint at the front end of the stainless steel inner tube is provided with an external thread or an internal thread hole, and the expansion joint at the rear end of the stainless steel inner tube is provided with an internal thread hole matching the external thread or an external thread matching the internal thread hole, so as to realize the threaded connection between the two different sections of the solar collector tubes.

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