A solar collector coated with a heat absorbing film

Abstract

The application provides a solar heat collector coated with heat-absorbing film, which comprises a heat-absorbing plate, a shell, a transparent cover plate and heat-insulating material, the transparent cover plate is arranged on the top of the shell, the heat-absorbing plate is arranged in the shell, and the heat-insulating material is arranged inside the inner side of the shell so as to form a heat-insulating space in the shell, characterized in that the heat-absorbing plate comprises three layers, and the first plate, the second plate and the third plate are sequentially arranged from top to bottom, the first plate is coated with heat-absorbing film, and the heat-absorbing capacity of the heat-absorbing film gradually increases along the fluid flow direction in the heat collector. The application can keep the temperature difference relatively stable in the whole heat exchange process by continuously increasing the heat-absorbing capacity, so that the technical effect similar to counterflow heat exchange is formed, and the constant temperature difference can exceed the counterflow heat exchange effect and reach the best heat exchange efficiency under the condition that the number of reflectors remains unchanged.

Description

Technical Field

[0001] This invention relates to a solar collector technology, and more particularly to a flat-plate solar collector. Background Technology

[0002] With the rapid development of modern society and economy, human demand for energy is increasing. However, the reserves of traditional energy sources such as coal, oil, and natural gas are constantly decreasing and becoming increasingly scarce, leading to continuous price increases. At the same time, the environmental pollution caused by conventional fossil fuels is becoming increasingly serious, all of which greatly restrict social development and the improvement of human quality of life. Energy issues have become one of the most prominent problems in the contemporary world. Therefore, the search for new energy sources, especially pollution-free clean energy, has become a hot research topic.

[0003] Solar energy is a clean, inexhaustible energy source with enormous reserves; the total amount of solar radiation received by the Earth's surface each year is 1 × 10⁻⁶. 18 Solar energy, with a capacity of kW·h, is more than ten thousand times the world's total annual energy consumption. Countries worldwide have made solar energy utilization a key aspect of new energy development. However, the low energy density of solar radiation reaching the Earth (approximately one kilowatt per square meter) and its discontinuous nature pose challenges to large-scale development and utilization. Therefore, to widely utilize solar energy, not only are technical issues to be resolved, but it must also be economically competitive with conventional energy sources.

[0004] Solar energy utilization devices convert sunlight into heat energy, which is then used to heat fluids from low to high temperatures to meet people's needs for hot fluids in daily life and production. Utilizing solar energy, a clean energy source, helps reduce the use of non-renewable energy and lower carbon emissions.

[0005] Research and engineering applications have shown that both flat-plate solar collectors and heat pipes possess excellent heat collection performance. Furthermore, phase change materials, due to their stable temperature during heat absorption and release processes, enable the entire system to achieve a uniform temperature, thus finding widespread application in the field of solar energy collection.

[0006] This invention provides a novel flat-plate solar collector. Through the cooperation between the capillary force at the bottom and the support column at the top, and by cooperating with the upper part of the flat tube, the heat pipe and the flat-plate solar collector are fully combined to achieve efficient, balanced, and precise heat collection.

[0007] Currently available heat-absorbing films all have a uniform thickness and arrangement, resulting in a relatively constant heat absorption efficiency. This leads to variations in overall heat exchange efficiency and increases the cost of the heat-absorbing film, without any targeted modifications.

[0008] To address the aforementioned shortcomings, this invention improves upon existing solar collectors by providing a novel plate-type solar collector. Through the continuous increase in the heat absorption capacity of the heat-absorbing film, the temperature difference remains relatively stable throughout the heat exchange process, thus achieving a technical effect similar to counter-current heat exchange. Moreover, while maintaining a constant number of reflectors, maintaining a constant temperature difference surpasses the effect of counter-current heat exchange, achieving optimal heat exchange efficiency. Summary of the Invention

[0009] This invention aims to provide a novel type of flat-plate solar collector. By continuously increasing the heat absorption capacity of the heat-absorbing film, the temperature difference remains relatively stable throughout the heat exchange process, thus forming a technical effect similar to countercurrent heat exchange. Moreover, with the number of reflectors remaining constant, maintaining a constant temperature difference can exceed the effect of countercurrent heat exchange, achieving optimal heat exchange efficiency.

[0010] To achieve the above objectives, the technical solution of the present invention is as follows:

[0011] A solar collector coated with a heat-absorbing film includes a heat-absorbing plate, a shell, a transparent cover plate, and insulation material. The transparent cover plate is disposed on the top of the shell, the heat-absorbing plate is disposed inside the shell, and the insulation material is disposed inside the inner side of the shell to form an insulation space inside the shell. The heat-absorbing plate comprises three layers, arranged sequentially from top to bottom as a first plate, a second plate, and a third plate. The first plate is coated with a heat-absorbing film, and the heat absorption capacity of the heat-absorbing film gradually increases along the fluid flow direction inside the collector.

[0012] As an improvement, the heat absorption capacity of the heat-absorbing film gradually increases with the direction of fluid flow within the collector.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] 1) This invention continuously increases the heat absorption capacity, maintaining a relatively stable temperature difference throughout the heat exchange process, thus achieving a technical effect similar to countercurrent heat exchange. Moreover, while keeping the number of reflectors constant, maintaining a constant temperature difference surpasses the effect of countercurrent heat exchange, achieving optimal heat exchange efficiency. Simultaneously, because the heat absorption efficiency varies at different locations, it avoids the increased cost associated with a uniform heat absorption film, potentially saving costs.

[0015] 2) This invention employs porous capillary modules in the plate solar collector and utilizes 3D printing technology to achieve a variable porosity structure. The pore diameter at the fluid inlet is larger than that at the fluid outlet, improving working efficiency and making the pore diameter variation more accurate. The use of 3D printing technology in the porous capillary modules allows for a gradual distribution of variable porosity density along the fluid flow, improving the manufacturing process and enabling precise computer-generated regular changes. Compared to existing manufacturing processes, the processing results are more accurate. The precise structural amplitude changes achieved through computer programming significantly improve processing precision, thereby enhancing heat exchange efficiency.

[0016] 3) The present invention improves the overall temperature uniformity and convective heat transfer capacity by using a larger orifice diameter at the fluid inlet than at the fluid outlet, resulting in different convective heat transfer capabilities at different orifice diameters.

[0017] 4) This invention improves the overall temperature uniformity and convective heat transfer capacity of the collector by gradually varying the pore density along the fluid flow. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the plate-type heat collection system of the present invention.

[0019] Figure 2 This is a schematic diagram of the disassembled structure of the solar collector of the present invention;

[0020] Figure 3 This is a structural diagram of the second plate of the solar collector of the present invention;

[0021] Figure 4 This is a schematic diagram of fluid flow in the solar collector of the present invention. Detailed Implementation

[0022] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In this specification, "top" refers to the side facing upwards during installation, and "bottom" refers to the side facing downwards.

[0023] Figure 1-4 A flat-plate solar collector is disclosed. For example... Figure 1 As shown, a flat-plate solar collector includes a heat-absorbing plate 1, a shell 2, a transparent cover plate 3, and insulation material. The transparent cover plate 3 is disposed on the top of the shell 2, the heat-absorbing plate 1 is disposed inside the shell 2, and the insulation material is disposed on the inner side of the shell 2 to form an insulation space inside the shell 2. Preferably, a lens is disposed on the transparent cover plate 3 to facilitate heat collection.

[0024] like Figure 2The heat absorber plate 1 shown has a third plate 11, a second plate 12, and a first plate 13 arranged sequentially from bottom to top. The three-layer structure is combined to form a complete heat absorber plate 1. The third plate 13 of the heat absorber plate is connected to the inlet pipe 4 and the outlet pipe 5.

[0025] As an improvement, a reflector 6 is placed between the heat-absorbing plate 1 and the transparent cover plate 3, such as... Figure 1 As shown. The reflector connects the heat-absorbing plate and the edge of the transparent cover plate 3. By setting the reflector 6, the heat from sunlight that shines into the collector but does not reach the heat-absorbing plate is also reflected back to the first plate of the heat-absorbing plate, further enhancing heat collection.

[0026] Preferably, the reflector has an arc-shaped structure, and the arc bends toward the shell.

[0027] Preferably, the reflector is a two-piece planar mirror bent structure, which bends towards the shell.

[0028] Preferably, the reflector is a multi-piece bent plane mirror structure.

[0029] Preferably, the interior of the housing 2 is filled with an inert gas.

[0030] like Figure 1 As shown, a heat absorption plate 1 includes a third plate 13, a second plate 14, and a first plate 15 arranged sequentially from top to bottom. A fluid inlet and an outlet are provided at the upper part of the third plate.

[0031] like Figure 2 As shown, the third plate 5 includes a fluid inlet 131 and a fluid outlet 132 disposed at both ends below the first plate. The second plate 14 includes an inlet collecting channel 141, an outlet collecting channel 142, an inlet branch 143, an outlet branch 144, an inlet flow channel 145, and an outlet flow channel 146 disposed below the second plate. The upstream of the inlet collecting channel 141 and the downstream of the outlet collecting channel 142 are respectively connected to the fluid inlet 131 and the fluid outlet 132 of the third plate. The inlet collecting channel 141 and the outlet collecting channel 142 are respectively connected to the inlet branch 143 and the outlet branch 144. The second plate 14 includes multiple bent plate-like structures. An inlet branch 143 is formed on one side of the structure, and an outlet branch 144 is formed on the other side. The inlet branch 143 and the outlet branch 144 are not directly connected. Through holes are provided in the inlet branch 143 and the outlet branch 144 to pass through the second plate, thereby forming an inlet flow channel 145 and an outlet flow channel 146. The first plate 15 includes a porous capillary module 151 located below, which is connected to the inlet flow channel 145 and the outlet flow channel 146. The porous capillary module 151 is made using 3D printing technology, so that the porous capillary module 151 has a variable porosity structure, with the pore diameter at the fluid inlet of the inlet flow channel being larger than the pore diameter at the fluid outlet of the outlet flow channel.

[0032] This invention employs porous capillary modules and manufactures them using 3D printing technology. The first plate forms a more compact microchannel by adding a porous capillary module structure to the bottom, which reduces the processing difficulty compared to finned channels, increases the fluid flow space and convective heat transfer area, and can also improve the temperature uniformity of the bottom surface by changing the pore size at the inlet and outlet of the porous capillary module.

[0033] Compared to traditional manufacturing techniques, 3D printing technology can accurately determine the size of the pores, improving work efficiency and making the changes in pore size more precise.

[0034] This invention improves the overall temperature uniformity and convective heat transfer capacity of the solar collector by using a porous medium with a larger inlet aperture than the outlet aperture. The fluid exhibits varying convective heat transfer capabilities at different aperture sizes. In a uniform aperture flow heat transfer process, the fluid temperature at the inlet is lower, resulting in a larger temperature difference with the cold plate and thus a more intense heat transfer process. However, as the fluid flows to the outlet, its temperature rises due to continuous heat absorption from the heat source during its previous flow, leading to a decrease in the temperature difference between the fluid and the outlet cold plate and a significant reduction in heat transfer capacity compared to the inlet. This results in more heat being carried away by the fluid at the inlet aperture and less at the outlet aperture, leading to poor temperature uniformity of the bottom plate. In a variable aperture flow heat transfer process, the larger inlet aperture increases thermal resistance, reducing the heat absorbed by the fluid at this point and enhancing the heat-carrying capacity of the fluid at the outlet. Simultaneously, the smaller outlet aperture strengthens turbulence and enhances heat transfer. However, the inlet and outlet orifice diameters should not differ too much. The preferred ratio of inlet and outlet orifice diameters is between 1.5 and 2.5. Otherwise, the heat exchange process at the outlet will be too intense, which will also lead to poor temperature uniformity of the bottom plate.

[0035] This invention utilizes 3D printing technology to manufacture the porous medium. First, a 3D model of the porous medium is created in SpaceCaim software. This model is then imported into the printing preparation software PreForm, where the model's orientation, support material, component material, and wall thickness are determined. The porous medium is made of AlSi10Mg aluminum alloy. After these preparations are completed, the Formlabs 3D printer is used for printing. After printing, the build platform is directly inserted into the Form Wash for efficient and uniform automatic cleaning of the model. Following cleaning, a rapid peeling technique is used to remove the porous medium from the printed surface; the support structure can be removed in just a few seconds. Finally, the porous medium is transferred to Form Cure for curing to maximize material properties and ensure dimensional accuracy.

[0036] Preferably, a heat-absorbing film is coated on the first plate. The heat-absorbing film comprises, from bottom to top, an infrared reflective coating, a heat-absorbing coating, an anti-reflective coating, and a protective layer, wherein the thickness ratio of the infrared reflective coating, the heat-absorbing coating, and the anti-reflective coating is 1:(1.2-1.4):(2.1-2.3); the infrared reflective coating is Ag; the heat-absorbing coating comprises at least two materials selected from TiAl, Cr, Nb, and Zr; the anti-reflective coating comprises, from the inside to the outside, AlN, TiO2, Ta2O5, and SiO2 layers, wherein the thickness ratio of the AlN, TiO2, Ta2O5, and SiO2 layers is 1:(0.9-1.1):(1.75-2.25):(1.2-1.8).

[0037] The protective layer is at least one of the metals Al, Si, Ti, Ni, or an alloy formed with N or O.

[0038] Preferably, the total thickness of the heat-absorbing layer is 1.6-2.3 μm.

[0039] The aforementioned size ratios are the optimal results obtained from nearly a hundred different thickness ratios. Through experiments, it was found that by using the composition and thickness of each independent layer in the above-mentioned absorbing coating, the prepared absorbing coating can achieve an absorptivity greater than 0.94 and an emissivity of 0.04.

[0040] The above coating can be prepared using the vacuum magnetron sputtering coating process commonly used in this field.

[0041] As an improvement, the heat absorption capacity of the heat-absorbing film gradually increases along the fluid flow direction within the collector. By continuously increasing the heat absorption capacity, the temperature difference remains relatively stable throughout the heat exchange process, thus creating a technical effect similar to counter-current heat exchange. Moreover, with the number of reflectors remaining constant, maintaining a constant temperature difference can exceed the effect of counter-current heat exchange, achieving optimal heat exchange efficiency.

[0042] Further optimization reveals that the heat absorption capacity of the heat-absorbing film increases progressively along the fluid flow direction within the collector. This optimized design further ensures that the temperature difference remains relatively stable throughout the heat exchange process, achieving a more optimized heat exchange effect.

[0043] Preferably, the first plate has columnar fins extending upwards. These columnar fins enhance heat collection and improve heat absorption capacity.

[0044] As an improvement, the distribution density of the cylindrical fins gradually increases along the fluid flow direction within the collector. This continuous increase in distribution density leads to a continuous increase in heat absorption capacity, maintaining a relatively stable temperature difference throughout the heat exchange process. This achieves a technical effect similar to counter-current heat exchange, and with the number of reflectors remaining constant, maintaining a constant temperature difference surpasses the effect of counter-current heat exchange, achieving optimal heat exchange efficiency.

[0045] Further optimization involves increasing the distribution density of the cylindrical fins along the fluid flow direction within the collector. This optimized design ensures a relatively stable temperature difference throughout the heat exchange process, resulting in a more optimized heat exchange effect.

[0046] Cylindrical ribs are preferred.

[0047] As an improvement, the diameter of the cylindrical fins gradually increases along the fluid flow direction within the collector. By continuously increasing the diameter, the heat absorption capacity continuously increases, allowing the temperature difference to remain relatively stable throughout the heat exchange process. This creates a technical effect similar to counter-current heat exchange, and with the number of reflectors remaining constant, maintaining a constant temperature difference can exceed the effect of counter-current heat exchange, achieving optimal heat exchange efficiency.

[0048] Further optimization involves gradually increasing the diameter of the cylindrical fins along the fluid flow direction within the collector. This optimized design ensures a relatively stable temperature difference throughout the heat exchange process, resulting in a more optimized heat exchange effect.

[0049] Preferably, the pore size of the porous capillary module gradually increases along the flow direction of the fluid in the inlet collecting channel 141. This distribution results in a gradual increase in capillary force and a decrease in flow resistance along the direction from the inlet of the collecting channel. This makes it more difficult for fluid with high resistance to flow in compared to fluid with low resistance, thus resulting in a more uniform fluid distribution along the flow direction and avoiding uneven heat transfer and localized excessively high or low temperatures caused by uneven fluid distribution.

[0050] Preferably, along the flow direction of the fluid within the inlet collecting channel 142, the pore size of the porous capillary module gradually increases in magnitude. This design of the magnitude of change, optimized through extensive experiments and numerical simulations, further achieves the technical effect of uniform fluid distribution, better meeting the needs of this invention.

[0051] Preferably, the pore size of the porous capillary module varies according to the following rule:

[0052] The total length of the inlet collection channel is L, and the diameter of the lowest outlet of the inlet collection channel is D. 末 The aperture D at a distance l from the inlet of the inlet collection channel follows the following pattern: D2 =f×(D 末 ) 2 +g×(D 末 ) 2 ×(l / L) e Where e, f, and g are coefficients, satisfying the following requirements:

[0053] 1.083 <e<1.104,0.995<f+g<1.011,0.499<f<0.625。

[0054] As a preferred option, e gradually increases with increasing l / L.

[0055] As a preferred value, 0.095 <e<1.100,f+g=1,0.565<f<0.578。

[0056] The above settings make the fluid distribution more uniform. The optimized formula was obtained through a large number of experiments and numerical simulations. It can achieve the technical effect of uniform fluid distribution in the best possible way, which better meets the needs of this invention.

[0057] Preferably, the pore density of the porous capillary module gradually increases along the flow direction of the fluid within the inlet collecting channel 141. This distribution results in a gradual increase in capillary force and a decrease in flow resistance along the direction from the inlet collecting channel. This makes it more difficult for fluid with high resistance to flow in compared to fluid with low resistance, thus resulting in a more uniform fluid distribution along the flow direction and avoiding uneven heat transfer and localized excessively high or low temperatures caused by uneven fluid distribution.

[0058] Preferably, along the flow direction of the fluid within the inlet collecting channel 142, the pore density of the porous capillary module gradually increases at a progressively larger rate. This design of the aforementioned variation rate, optimized through extensive experiments and numerical simulations, further achieves the technical effect of uniform fluid distribution, better meeting the needs of this invention.

[0059] Preferably, the pore density of the porous capillary module varies according to the following rule:

[0060] The total length of the inlet collection channel is L, and the density at the downstream end of the inlet collection channel is M. 入 The density M at a distance l from the inlet of the inlet collection channel follows the following pattern: M = b × M 入 +c×M 入 ×(l / L) a Where a, b, and c are coefficients, satisfying the following requirements:

[0061] 1.082 <a<1.105,0.994<b+c<1.012,0.498<b<0.629。

[0062] Preferably, a gradually increases as l / L increases.

[0063] As a preferred value, 0.095 <a<1.100,b+c=1,0.565<b<0.578。

[0064] The above settings make the fluid distribution more uniform. The optimized formula was obtained through a large number of experiments and numerical simulations. It can achieve the technical effect of uniform fluid distribution in the best possible way, which better meets the needs of this invention.

[0065] Preferably, each inlet and outlet branch is provided with multiple through holes penetrating the second plate. The density of these through holes gradually increases along the flow direction of the fluid within the inlet collecting channel 141. This distribution ensures that the flow resistance decreases as the flow area changes along the direction from the inlet of the collecting channel, making it more difficult for fluid with high resistance to flow in compared to fluid with low resistance. This results in a more uniform fluid distribution along the flow direction, avoiding uneven heat transfer and localized excessively high or low temperatures caused by uneven fluid distribution.

[0066] Preferably, the distribution density of the through holes gradually increases along the flow direction of the fluid within the inlet collecting channel 142. This design of the variation range, optimized through extensive experiments and numerical simulations, further achieves the technical effect of uniform fluid distribution, better meeting the needs of this invention.

[0067] Preferably, each inlet and outlet branch is provided with multiple through holes penetrating the second plate. The diameter of each through hole gradually increases along the fluid flow direction within the inlet collecting channel 141. This distribution ensures that the flow area gradually increases along the direction from the inlet of the inlet collecting channel. As the flow area changes, the flow resistance decreases, making it more difficult for fluid with high resistance to flow in compared to fluid with low resistance. This results in a more uniform fluid distribution along the flow direction, avoiding uneven heat transfer and localized excessively high or low temperatures caused by uneven fluid distribution.

[0068] Preferably, along the flow direction of the fluid within the inlet collecting channel 142, the distribution density of the pore size of each through hole gradually increases in magnitude. This design of the variation range, optimized through extensive experiments and numerical simulations, further achieves the technical effect of uniform fluid distribution, better meeting the needs of this invention.

[0069] Preferably, the aforementioned porous capillary module is manufactured using 3D printing technology. In existing manufacturing processes, achieving gradual changes in the pore size of porous capillary modules is extremely difficult. This invention utilizes 3D printing technology to achieve a gradual distribution of variable pore density along fluid flow in the capillary structure, improving the processing technology and enabling precise computer-generated regular changes. Compared to existing fabrication processes, with a well-designed gradual printing program, the processing results are more accurate. Achieving precise structural amplitude changes through computer programming significantly improves processing precision, thereby enhancing heat exchange efficiency.

[0070] The collector's fluid inlet 131 is connected to an external fluid source via a pipe. The collector also includes a temperature sensor, a light sensor, a flow meter, a flow processor, and a central processing unit. Two temperature sensors are installed at the fluid inlet 131 and the fluid outlet 132 of the collector, respectively, to measure the temperature of the fluid at the inlet and outlet. The light sensor detects the intensity of sunlight. The flow meter is installed on the connecting pipe between the fluid inlet 131 and the external fluid source to measure the flow rate of the fluid entering the collector. The flow processor is installed on the connecting pipe between the fluid inlet 131 and the external fluid source to control the flow rate of the fluid entering the collector. The temperature sensor, light sensor, flow meter, flow processor, and central processing unit are communicatively connected. The central processing unit includes a control unit that generates adjustment signals to control the flow meter based on the measurements from the temperature sensor and the light sensor, thereby changing the flow rate of the fluid flowing into the corresponding collector, so that the fluid outlet temperature within the collector remains constant.

[0071] The formula for calculating the flow rate of the fluid in the pipe per unit time based on the solar radiation value is: ΔV=(F×M×η) / (ρ×C×(W3-W)), where ΔV is the flow rate of the fluid in the pipe per unit time, F is the solar radiation value, M is the effective heat absorption area of ​​the collector, η is the heat loss coefficient, which ranges from 0.95 to 0.98, ρ is the density of the fluid in the pipe, C is the average specific heat of the fluid in the temperature range of the pipe, W3 is the fluid temperature that the collector needs to reach, and W is the average temperature of the collector, i.e., W=(W1+W2) / 2, where W1 and W2 are the temperatures of the collector outlet 132 and the collector inlet 131, respectively.

[0072] Of course, there are many other ways to measure the average temperature of a solar collector. For example, temperature sensors can be installed at multiple locations on the collector, and the average temperature of the fluid at these locations can be calculated to measure the collector's temperature. If this method is used, it is not necessary to install temperature sensors at the collector's inlet and outlet; instead, temperature sensors need to be installed inside the collector.

[0073] The central processing unit also includes a data storage unit and a logic processor. The data storage unit is used to store the values ​​measured by the temperature sensor, the light sensor, and the flow meter, as well as the formula for the flow rate. The logic processor calculates the flow rate per unit time based on the measured values ​​and the formula for the flow rate, so that the temperature of the output water remains unchanged.

[0074] The collector is equipped with an electric heating device. The electric heating device can work independently when there is no sunlight (e.g., at night or on a cloudy day), or when sunlight cannot meet the normal use of the heat fluid, it can work together with a temperature sensor, a light sensor, a flow meter, and the central processing unit to achieve joint control of the heat fluid temperature under the control of the central processing unit.

[0075] In addition, the central processing unit can independently control the electric heating device to achieve the required fluid temperature of the collector. For example, it can control the electric heating device to heat the fluid based on the average fluid temperature measured at the inlet and outlet of the collector.

[0076] When the detected output temperature is below the threshold, the processor controls the electric heater to start heating. When the detected output temperature is above the threshold, the processor controls the electric heater to stop heating.

[0077] The temperature control of the solar collector can be performed in real time or according to a time period. In the case of time-based control, it is necessary to set a time period, measure the average solar irradiance value for each time period; measure the average collector outlet temperature T1 for each time period; measure the average collector outlet temperature T2 for each time period; and calculate the water flow rate of the collector based on the set collector terminal temperature T3 and the measured values.

[0078] The control unit changes the flow rate of the fluid flowing into the corresponding solar collector by adjusting the valve opening. Of course, there are other methods to adjust the flow rate, such as controlling a pump.

[0079] Preferably, the inlet collecting channel 141 and the outlet collecting channel 142 are designed with a conical structure. Along the flow direction of the fluid in the inlet collecting channel, the flow channel area decreases, while along the flow direction of the fluid in the outlet collecting channel 142, the flow channel area increases. This further ensures the uniform distribution of fluid in the flow channels, improving heat exchange efficiency and reducing overall pressure drop.

[0080] Preferably, the second plate 14 includes multiple bent plate-like structures, with an inlet branch 143 formed on one side and an outlet branch 144 formed on the other side. The inlet branch 143 and the outlet branch 144 are not directly connected. The fluid flows from the inlet branch 143 to the outlet branch 144 due to the capillary force of the hot fluid capillary layer.

[0081] Preferably, the bent plate-like structure is a V-shaped or trapezoidal structure. This allows for the design of more heat exchange microchannels within the same width, increasing the heat exchange area and improving the overall heat exchange capacity while reducing the volume.

[0082] As a preferred option, such as Figure 3 As shown, the hole penetrating the second plate can be elongated. This application uses a penetrating hole in the second plate to allow fluid to enter the first plate 15 in a targeted manner. Porous capillary modules can be strategically placed at corresponding positions on the first plate 15; for example, porous capillary modules can be omitted at the location where the hole is formed, while they can be placed at other locations. This setup is achieved through 3D printing, avoiding the manufacturing difficulties of existing technologies.

[0083] Preferably, the fluid inlet 131 and the fluid outlet 132 are positioned diagonally on the third plate 5. This arrangement ensures the fluid heat exchange area and reduces the occurrence of short circuits.

[0084] As an improvement, the amount of heat collected on the first plate gradually increases along the direction of fluid flow within the collector. This continuous increase in heat collection maintains a relatively stable temperature difference throughout the heat exchange process, creating a technical effect similar to counter-current heat exchange. Moreover, while keeping the amount of heat collected constant, maintaining a constant temperature difference surpasses the effect of counter-current heat exchange, achieving optimal heat exchange efficiency.

[0085] Further optimization involves increasing the amount of heat collected on the first plate along the fluid flow direction within the collector. This optimized design ensures a relatively stable temperature difference throughout the heat exchange process, resulting in a more effective heat exchange.

[0086] Preferably, the transparent cover plate 3 is provided with a lens for heat collection. By setting the focusing direction of the lens, the amount of heat collected on the first plate gradually changes.

[0087] Preferably, multiple lenses are arranged on the transparent cover, forming a lens array. The density of the lenses gradually increases along the fluid flow direction within the collector. The rate of increase in lens density along the fluid flow direction becomes increasingly larger. By continuously increasing the number of lenses, the temperature difference remains relatively stable throughout the heat exchange process, thus creating a technical effect similar to counter-current heat exchange. Moreover, while maintaining a constant amount of collected heat, maintaining a constant temperature difference surpasses the effect of counter-current heat exchange, achieving optimal heat exchange efficiency.

[0088] Preferably, multiple lenses are arranged on the transparent cover plate, with the coverage area of ​​each lens gradually increasing along the fluid flow direction within the collector. The rate of increase in the coverage area of ​​each lens on the transparent cover plate becomes increasingly larger along the fluid flow direction within the collector. By continuously increasing the number of lenses, the heat collection capacity remains relatively stable throughout the heat exchange process, thus creating a technical effect similar to counter-current heat exchange. Moreover, while maintaining a constant heat collection capacity, maintaining a constant temperature difference can exceed the effect of counter-current heat exchange, achieving optimal heat exchange efficiency.

[0089] Viewed from above, the lenses on the transparent cover appear circular or square. Multiple rows are arranged along the direction of fluid flow, with multiple lenses in each row, forming a multi-row, multi-column lens array. It should be noted that each row is perpendicular to the direction of fluid flow, and each column is parallel to the direction of fluid flow.

[0090] Preferably, the spacing between adjacent rows gradually decreases along the fluid flow direction within the collector. Preferably, the rate of decrease in spacing between adjacent rows becomes increasingly larger along the fluid flow direction within the collector.

[0091] Preferably, along the fluid flow direction within the collector, the coverage area of ​​the lenses in different rows on the transparent cover plate gradually increases. Preferably, along the fluid flow direction within the collector, the rate of increase in the coverage area of ​​the lenses in different rows on the transparent cover plate becomes increasingly larger.

[0092] Preferably, the transparent cover is composed of several Fresnel lenses. By selecting the reflection direction of each Fresnel lens, the heat collection at each location can be controlled.

[0093] The collector's working process is as follows: The fluid is driven by the pump to flow from the fluid inlet 131 into the inlet branch 21, then into the multi-inlet converging channel 141, and then split through the inlet branch 143. The fluid is forced to flow downward in the conical branch due to the obstruction at the top, and is received by the inlet channel 145 below the branch. Since both sides of the inlet channel 145 are porous capillary modules 151, the fluid flows in two opposite directions in the porous capillary modules. During this process, it absorbs the heat transferred by the porous capillary modules 151. After the fluid absorbs heat, it flows upward under the force, flows through the outlet channel 146 into the outlet branch 144, flows out through the outlet branch 144, and then flows into the outlet converging channel 142 and finally flows out through the fluid outlet 132. Thus, the entire flow heat exchange process is completed.

[0094] While the present invention has been disclosed above with reference to preferred embodiments, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A solar collector coated with a heat-absorbing film, comprising a heat-absorbing plate, a shell, a transparent cover plate, and a heat-insulating material, wherein the transparent cover plate is disposed on the top of the shell, the heat-absorbing plate is disposed inside the shell, and the heat-insulating material is disposed on the inner side of the shell to form a heat-insulating space inside the shell, characterized in that, The heat absorption plate comprises three layers, arranged sequentially from top to bottom as a first plate, a second plate, and a third plate. The third plate includes a fluid inlet and a fluid outlet located at the bottom. The first plate includes a porous capillary module located at the bottom, which is connected to the inlet channel and the outlet channel. The second plate includes an inlet collecting channel, an outlet collecting channel, an inlet branch, an outlet branch, an inlet channel, and an outlet channel located at the bottom. The upstream of the inlet collecting channel and the downstream of the outlet collecting channel are respectively connected to the fluid inlet and the fluid outlet of the third plate. The inlet collecting channel and the outlet collecting channel are respectively connected to the inlet branch and the outlet branch. Next, the second plate includes multiple bent plate-like structures. One side of each plate-like structure forms an inlet branch, and the other side forms an outlet branch. The inlet and outlet branches are not directly connected. Through holes are provided in the inlet and outlet branches to penetrate the second plate, thereby forming inlet and outlet flow channels. A heat-absorbing film is coated on the top of the first plate. Along the fluid flow direction in the collector, the heat absorption capacity of the heat-absorbing film gradually increases. The porous capillary module is made using 3D printing technology, which makes the porous capillary module a variable porosity structure, with the pore diameter at the fluid inlet of the inlet flow channel being larger than the pore diameter at the fluid outlet of the outlet flow channel.

2. The solar collector as described in claim 1, characterized in that, Along the direction of fluid flow inside the collector, the heat absorption capacity of the heat-absorbing film gradually increases by a larger and larger margin.

3. The solar collector as described in claim 1, characterized in that, The ratio of the inlet diameter of the fluid in the inlet channel to the outlet diameter of the fluid in the outlet channel is between 1.5 and 2.5.

Images