Snakelike heat exchange tube with composite enhanced heat transfer structure and photovoltaic / photo-thermal system

Abstract

The invention relates to a snakelike heat exchange tube with a composite enhanced heat transfer structure and a photovoltaic / photo-thermal system.The two opposite sides in the heat exchange tube are provided with a first corrugated base face and a second corrugated base face respectively in the axial direction, and the first corrugated base face and the second corrugated base face are the same in structure and are symmetrically distributed; the first corrugated base surface and the second corrugated base surface are sequentially and alternately connected to form contraction section flow channels with reduced cross section areas and expansion section flow channels with increased cross section areas, first in-pipe fins are arranged on the first corrugated base surface, second in-pipe fins are arranged on the second corrugated base surface, and the first in-pipe fins and the second in-pipe fins are the same in structure and are symmetrically distributed at intervals; and the end surfaces of the first in-tube fins are higher than the troughs of the first corrugated base surface. Compared with the prior art, the problem that heat transfer and resistance of a traditional single strengthening structure are difficult to balance is solved, and the comprehensive heat efficiency of the system is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of heat exchanger technology, and in particular to a serpentine heat exchange tube with a composite enhanced heat transfer structure and a photovoltaic / photothermal system. Background Technology

[0002] Photovoltaic / thermal (PV / T) technology can simultaneously generate electricity and heat, significantly overcoming the problem of decreased power generation efficiency caused by temperature rise in traditional photovoltaic modules. It is a key approach to achieving efficient utilization of the full spectrum of solar energy. In a PV / T system, the serpentine heat exchange tube, as the core component of the absorber plate, directly determines the cooling effect of the photovoltaic cells and the quality of heat recovery due to the heat exchange capacity of the fluid inside it.

[0003] Photovoltaic / solar thermal (PV / T) systems, as a core technology for comprehensive solar energy utilization, must balance photovoltaic power generation and solar thermal conversion efficiency. For example, invention publication CN110553408A discloses a PVT collector, comprising an aluminum alloy frame, tempered glass, EVA, photovoltaic cells, ultra-thin EVA, a core, an insulation layer, and a backplate arranged from top to bottom within the aluminum alloy frame. The tempered glass, EVA, photovoltaic cells, ultra-thin EVA, and core are thermally laminated together. The upper surface of the core is coated with a selective absorption coating. A heat circulation device is also provided between the core and the backplate, with the heat circulation device closely attached to the back of the core, and the insulation layer filling the area around the heat circulation device.

[0004] Traditional PV / T systems often employ a single enhanced heat transfer structure, including individual photovoltaic tubes, simple fins, or corrugated pipes. For example, utility model publication CN215982806U discloses a method that combines heat pipe-type photovoltaic / photothermal modules with a floor, utilizing a combination of heat pipes and phase change materials to solve the temperature unevenness problem caused by glass curtain wall designs in large buildings. This achieves uniform heat distribution and energy savings, extending the heat supply duration. Furthermore, invention application CN111219887A discloses a heat exchange system using upward and downward corrugated pipes to form a circulating air layer and microchannel heat absorbers in a photovoltaic-photothermal composite device. This system supplies heat to the outside via a heat transfer fluid, improving solar energy utilization and saving conventional energy consumption.

[0005] However, the heat exchange tubes disclosed in the aforementioned systems suffer from problems such as difficulty in balancing heat transfer efficiency and flow resistance, and complex multi-parameter coupling. In existing technologies, while corrugated flow channels can enhance turbulence, their local fit is insufficient; while finned structures can expand the heat transfer area, they easily lead to a sharp increase in flow resistance. Furthermore, optimization of a single structure lacks systematicity and makes it difficult to achieve global optimization.

[0006] Therefore, there is an urgent need for a composite heat transfer enhancement structure that combines corrugated flow channels and fins, and to break through the existing technical bottlenecks through multi-parameter collaborative optimization. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art, such as insufficient local fit of the corrugated flow channel and the fin structure that easily leads to a sharp increase in flow resistance, and to provide a serpentine heat exchange tube and photovoltaic / photothermal system with a composite enhanced heat transfer structure.

[0008] The objective of this invention can be achieved through the following technical solutions: On the one hand, this solution provides a serpentine heat exchanger tube with a composite enhanced heat transfer structure. The serpentine heat exchanger tube has a first corrugated base surface and a second corrugated base surface on opposite sides along the axial direction. The first corrugated base surface and the second corrugated base surface have the same structure and are symmetrically distributed, forming a contraction section flow channel with a decreasing cross-sectional area and an expansion section flow channel with an increasing cross-sectional area that are connected alternately in sequence. The first corrugated base surface has a first tube fin, and the second corrugated base surface has a second tube fin. The first tube fin and the second tube fin have the same structure and are symmetrically spaced. The end face of the first tube fin is higher than the trough of the first corrugated base surface.

[0009] Preferably, the first tube fin is disposed on the center line of the first corrugated base surface, and the second tube fin is disposed on the center line of the second corrugated base surface.

[0010] Preferably, there are multiple fins inside the first tube, and each fin inside the first tube is parallel to each other and evenly distributed along the width direction of the first corrugated base surface.

[0011] Preferably, the width of the first tube inner fin is 0.2-0.8 mm, and the height of the first tube inner fin is 2.0-3.5 mm.

[0012] Preferably, the corrugation height of the first corrugated base surface is 1-3mm, and the corrugation spacing of the first corrugated base surface is 75-300mm.

[0013] Preferably, the outer surface of the serpentine heat exchange tube is roughened to enhance its heat absorption capacity.

[0014] On the other hand, this solution also provides a photovoltaic / photothermal system, including a serpentine heat exchange tube with a composite enhanced heat transfer structure. The system also includes a photovoltaic thermal plate, a heat-absorbing aluminum back plate, and a heat-insulating sponge stacked from top to bottom. The serpentine heat exchange tube is arranged in an S-shaped curve between the heat-absorbing aluminum back plate and the heat-insulating sponge.

[0015] Preferably, the system further includes a photovoltaic thermal panel comprising a glass cover plate, an air interlayer, and a solar cell photovoltaic module stacked from top to bottom, wherein the solar cell photovoltaic module is attached to the side of the heat-absorbing aluminum backing away from the heat-insulating sponge.

[0016] Preferably, the solar cell photovoltaic module is encapsulated by bonding two layers of EVA film.

[0017] Preferably, there are multiple photovoltaic thermal panels, which are connected in series and then in parallel.

[0018] Compared with the prior art, the present invention has the following advantages: (1) This scheme incorporates a composite structure of periodically expanding and contracting corrugated channels and longitudinal fins symmetrically distributed vertically within the serpentine heat exchange tube. When the fluid flows through the throat of the corrugated channel, it accelerates the scouring of the fin surface, and when it flows through the expansion section, it generates separation vortices and enhances fluid mixing. This structure effectively disrupts the fluid boundary layer, enhances the convective heat transfer coefficient of the tube wall and fin surface, and solves the problem of insufficient heat transfer capacity of traditional single structures at low flow rates. Compared with fully filled porous media or complex twisted band structures, the corrugated channels in this scheme adopt a periodic stepped corrugated design, and the fins are located on the symmetrical plane of the center of the channel, without completely blocking the main flow channel. This can significantly improve the heat transfer capacity while effectively suppressing the excessive increase in flow resistance.

[0019] (2) The comprehensive heat transfer factor of the serpentine pipe structure in this scheme can reach 1.65-2.35, which is significantly better than the 1.2-1.4 of the traditional single-strength structure, achieving the best balance between heat transfer enhancement and pump power consumption. Moreover, through Taguchi orthogonal experiments and numerical simulations, multi-parameter synergistic optimization of corrugation depth, corrugation period and fin size was carried out, and the system achieved efficient heat capture in a limited space. Experiments show that the comprehensive primary energy efficiency of this photovoltaic-thermal system can reach 1.15-1.28, which is particularly suitable for high power density heat dissipation and high-grade heat recovery application scenarios. Attached Figure Description

[0020] Figure 1 This is an exploded structural diagram of the photovoltaic / photothermal system provided by the present invention; Figure 2 An axial cross-sectional view of the serpentine heat exchange tube provided by the present invention along the plane containing the fins inside the tube; Figure 3 A cross-sectional view of the serpentine heat exchange tube provided by the present invention along the plane containing the fins inside the tube. Figure 4 This is a schematic diagram of the serpentine heat exchange tube provided by the present invention; Figure 5 A schematic diagram of the axial structure of the inner corrugations of the serpentine heat exchanger provided by the present invention; In the diagram: 1. Photovoltaic thermal panel; 2. Glass cover plate; 3. Air interlayer; 4. Solar cell photovoltaic module; 5. EVA film; 6. Heat-absorbing aluminum backplate; 7. Serpentine heat exchange tube; 8. Insulating sponge; 9. Aluminum outer frame; 10. Inner tube fins; 11. Inner tube corrugations; 101. First inner tube fins; 102. Second inner tube fins; 111. First corrugated base surface; 112. Second corrugated base surface; 113. Contraction section flow channel; 114. Expansion section flow channel. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0023] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0024] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed during use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0025] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0026] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0027] Example 1 like Figure 4 and Figure 5 As shown, this embodiment provides a serpentine heat exchanger tube with a composite enhanced heat transfer structure. A first corrugated base surface 111 and a second corrugated base surface 112 are respectively provided on opposite sides along the axial direction inside the serpentine heat exchanger tube. The first corrugated base surface 111 and the second corrugated base surface 112 have the same structure and are symmetrically distributed, forming a contraction section flow channel 113 with a decreasing cross-sectional area and an expansion section flow channel 114 with an increasing cross-sectional area, connected alternately in sequence. A first tube fin 101 is provided on the first corrugated base surface 111, and a second tube fin 102 is provided on the second corrugated base surface 112. The first tube fin 101 and the second tube fin 102 have the same structure and are symmetrically spaced. The end face of the first tube fin 101 is higher than the trough of the first corrugated base surface 111.

[0028] In a preferred embodiment, the outer diameter of the serpentine heat exchange tube 7 is 10-12 mm, and the cross-sectional shape of the serpentine heat exchange tube 7 can be circular or other polygonal shapes. The first inner tube fin 101 is disposed on the center line of the first corrugated base surface 111, and the second inner tube fin 102 is disposed on the center line of the second corrugated base surface 112. The width of the first inner tube fin 101 is 0.2-0.8 mm, and the height of the first inner tube fin 101 is 2.0-3.5 mm. The corrugation height of the first corrugated base surface 111 is 1-3 mm, and the corrugation spacing of the first corrugated base surface 111 is 75-300 mm.

[0029] In this embodiment, as Figure 2 and Figure 3 As shown, to obtain the best overall heat transfer performance, Taguchi orthogonal experiments were conducted: using the Nusselt number (Nu), the reciprocal of the friction factor (1 / f), the comprehensive heat transfer factor (PEC), and the thermal efficiency (η) as evaluation indicators, the optimal parameter combination was determined by the signal-to-noise ratio (S / N); combined with numerical simulation: multiphysics coupling simulation was performed using ANSYS Fluent, with a total mesh size of 9-11 million, and the synergistic effect of the fluid and temperature fields was optimized using field synergy theory to determine the optimal dimensions. The following optimized dimensions were adopted: the width of the fins inside the tube is W=0.8mm, the height is H=3.5mm, with one fin at the top and one at the bottom; the corrugated flow channel adopts a stepped design, with a corrugation height h=3mm and a corrugation spacing s=75mm. Under these parameters, the fluid is accelerated and scours the fins when flowing through the corrugated contraction section, which greatly improves the convective heat transfer coefficient, and because the center of the flow channel remains connected, the pressure loss is controlled within a reasonable range.

[0030] In this embodiment, the outer surface of the serpentine heat exchange tube is roughened to enhance its heat absorption capacity.

[0031] Optionally, there may be multiple fins 101 inside the first tube. Each fin 101 inside the first tube is parallel to each other and is evenly distributed along the width direction of the first corrugated base surface 111. By increasing the number of fins inside the tube, the contact area with the coolant is increased.

[0032] Example 2 like Figure 1 As shown, this embodiment provides a photovoltaic / photothermal system, employing the serpentine heat exchanger tube with a composite enhanced heat transfer structure as described in Embodiment 1. The system includes a glass cover plate for convective heat exchange with the environment and radiative heat exchange with the sky; an air jacket for convective heat exchange with the lower surface of the glass cover plate and the upper surface of the PV panel; a photovoltaic solar cell module that absorbs a portion of solar radiation and converts it into electrical energy, while the remainder is converted into thermal energy through convective heat exchange with the air jacket and absorbed by the heat-absorbing plate via thermal conductivity; an EVA film, a thermosetting adhesive film attached to the upper and lower surfaces of the solar cell; a heat-absorbing aluminum backplate that extracts heat accumulated in the PV panel through a heat conduction process to heat the serpentine heat exchanger tube; the serpentine heat exchanger tube, typically made of aluminum, which heats the cooling water after a temperature rise due to thermal conductivity; an insulating sponge that reduces heat dissipation to the outside environment and facilitates convective heat exchange with the surrounding environment; an aluminum outer frame, a key protective structure in the photovoltaic module; internal fins, structures inside the tube that enhance heat exchange; and internal corrugations, structures inside the tube that enhance heat exchange. Compared with the prior art, the present invention provides a serpentine heat exchange tube composite enhanced heat transfer structure for photovoltaic / photothermal PV / T systems, which maximizes the enhancement of heat transfer.

[0033] In this embodiment, the photovoltaic / thermal (PV / T) system exchanges heat convectively with the environment through the glass cover plate 2 and radiatively with the sky. A portion of solar radiation passes through the glass cover plate 2, while the remainder is absorbed. Convective heat exchange occurs between the air gap 3 and the lower surface of the glass cover plate 2, as well as the upper surface of the PV panel. A portion of the solar radiation passing through the glass cover plate 2 is absorbed by the photovoltaic modules 4 and converted into electrical energy; the remainder is converted into heat through convective heat exchange with the air gap 3 and absorbed by the heat-absorbing aluminum backplate 6 via thermal conduction. The heat-absorbing aluminum backplate 6 extracts the heat accumulated in the PV panel through a thermal conduction process, heating the serpentine heat exchange tubes 7 to heat the cooling water, thereby converting the heat in the tubes into its internal energy. The insulating sponge 8 reduces the system's heat dissipation to the outside world and facilitates convective heat exchange with the surrounding environment. The aluminum outer frame 9 provides structural support and weather protection.

[0034] In this embodiment, the photovoltaic module 4 of the solar cell has an EVA film 5 bonded to both the top and bottom sides to ensure its firmness and sealing. The serpentine heat exchange tube 7 is equipped with internal fins 10 and internal corrugations 11 to enhance heat transfer.

[0035] like Figures 2 to 5 As shown, the core of this embodiment lies in the internal structure design of the serpentine heat exchange tube 7. This heat exchange tube no longer has a smooth inner wall, but instead integrates internal fins 10 and internal corrugations 11. Specifically, pairs of internal fins 10 are provided at the upper and lower center positions of the tube cross-section, as shown... Figure 3 The cross-sectional view on the left is shown. The fins extend directly into the main fluid flow zone, with a fin width W of 0.2-0.8 mm and a height H of 2.0-3.5 mm. Simultaneously, the corrugations 11 inside the pipe exhibit periodic undulations along the fluid flow direction, as shown... Figure 3 As shown on the right, a flow channel with alternating contraction and expansion sections is formed, with a corrugation height h of 1-3 mm and a period s of 75-300 mm. This design forces the fluid to continuously change its velocity and direction, inducing the generation of secondary flow.

[0036] To achieve optimal overall heat transfer performance, the following preferred dimensions are adopted in this embodiment: fin width W = 0.8 mm, height H = 3.5 mm, and number N = 2 (one at the top and one at the bottom); the corrugated flow channel adopts a stepped design with a corrugation height h = 3 mm and a corrugation spacing s = 75 mm. Under these parameters, the fluid is accelerated and scours the fins when flowing through the corrugated contraction section, greatly improving the convective heat transfer coefficient. Furthermore, because the center of the flow channel remains connected, the pressure loss is controlled within a reasonable range.

[0037] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A serpentine heat exchanger tube with a composite enhanced heat transfer structure, characterized in that, The serpentine heat exchange tube has a first corrugated base surface (111) and a second corrugated base surface (112) on opposite sides along the axial direction. The first corrugated base surface (111) and the second corrugated base surface (112) have the same structure and are symmetrically distributed. They form a shrinking section flow channel (113) with a smaller cross-sectional area and an expanding section flow channel (114) with a larger cross-sectional area, which are connected alternately in sequence. The first corrugated base surface (111) has a first tube fin (101) and the second corrugated base surface (112) has a second tube fin (102). The first tube fin (101) and the second tube fin (102) have the same structure and are symmetrically spaced. The end face of the first tube fin (101) is higher than the trough of the first corrugated base surface (111).

2. A serpentine heat exchanger tube with a composite enhanced heat transfer structure according to claim 1, characterized in that, The first tube fin (101) is disposed on the center line of the first corrugated base surface (111), and the second tube fin (102) is disposed on the center line of the second corrugated base surface (112).

3. A serpentine heat exchanger tube with a composite enhanced heat transfer structure according to claim 1, characterized in that, The number of the first tube fins (101) is multiple, and each first tube fin (101) is parallel to each other and uniformly distributed along the width direction of the first corrugated base surface (111).

4. A serpentine heat exchanger tube with a composite enhanced heat transfer structure according to claim 1, characterized in that, The width of the first tube inner fin (101) is 0.2-0.8 mm, and the height of the first tube inner fin (101) is 2.0-3.5 mm.

5. A serpentine heat exchanger tube with a composite enhanced heat transfer structure according to claim 1, characterized in that, The corrugation height of the first corrugated base surface (111) is 1-3mm, and the corrugation spacing of the first corrugated base surface (111) is 75-300mm.

6. A serpentine heat exchanger tube with a composite enhanced heat transfer structure according to claim 1, characterized in that, The outer surface of the serpentine heat exchange tube is roughened to enhance its heat absorption capacity.

7. A photovoltaic / photothermal system, characterized in that, The system includes a serpentine heat exchange tube with a composite enhanced heat transfer structure as described in any one of claims 1-6. The system also includes a photovoltaic thermal plate (1), a heat-absorbing aluminum back plate (6), and a heat-insulating sponge (8) stacked from top to bottom. The serpentine heat exchange tube is arranged in an S-shaped curve between the heat-absorbing aluminum back plate (6) and the heat-insulating sponge (8).

8. A photovoltaic / photothermal system according to claim 7, characterized in that, The system also includes a photovoltaic thermal panel (1) comprising a glass cover plate (2), an air interlayer (3), and a solar cell photovoltaic module (4) stacked from top to bottom, wherein the solar cell photovoltaic module (4) is attached to the side of the heat-absorbing aluminum back plate (6) away from the heat-insulating sponge (8).

9. A photovoltaic / photothermal system according to claim 8, characterized in that, The solar cell photovoltaic module (4) is encapsulated by two layers of EVA film (5).

10. A photovoltaic / photothermal system according to claim 7, characterized in that, The number of photovoltaic thermal panels (1) is multiple, and each photovoltaic thermal panel (1) is connected in series and then in parallel.

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