A Photovoltaic-Thermal Air Collector for Enhanced Heat Transfer

Abstract

The present invention discloses a photovoltaic-thermal air-type collector for enhancing heat transfer, which comprises a housing, a photovoltaic cell, a substrate and fins. The photovoltaic cell is attached to the bottom surface of a light-transmitting plate on the top of the housing, and the bottom of the photovoltaic cell is attached to the top surface of the substrate. A plurality of rows of fins are assembled transversely in the inner cavity of the housing, and a plurality of rows of fins are assembled longitudinally in the inner cavity of the housing. The light-transmitting plate on the top of the housing is composed of two layers of velvet-textured tempered glass plates, and a vacuum is provided between the two layers of velvet-textured tempered glass plates. The substrate is a three-layer structure, wherein the top layer of the substrate is a transparent PET plate, and the photovoltaic cell is bonded to the PET plate through EVA glue. The middle layer of the substrate is an absorption film. Beneficial effects: The theoretical reliability of the present invention is high, the heat transfer enhancement effect is obvious, the heat collection efficiency of the collector is greatly improved, the photovoltaic conversion efficiency is synergistically improved, and the utilization rate of solar energy is maximized.

Description

Technical Field

[0001] The present invention relates to an air-type collector, and particularly to a photovoltaic-thermal air-type collector with enhanced heat transfer. Background Art

[0002] At present, only a small part of the solar energy received by the photovoltaic cell module of the traditional solar air collector can be converted into electric energy, while most of it is converted into heat energy. In the cooling system of the collector, due to the problems of low thermal conductivity of air and small convective heat transfer coefficient, the heat collection efficiency of the photovoltaic module and the photovoltaic conversion efficiency are low. Therefore, adding enhanced heat transfer measures in the collector cooling system can not only reduce the temperature of the photovoltaic cell module and improve the photovoltaic conversion efficiency, but also improve the air heat collection quality and the heat collection efficiency of the collector, effectively solving the contradiction between the two. Therefore, in view of the above problems, the present invention has invented a photovoltaic-thermal air-type collector with enhanced heat transfer through structural innovation and optimization. Summary of the Invention

[0003] The object of the present invention is to provide a photovoltaic-thermal air-type collector with enhanced heat transfer, which improves the problems of low thermal conductivity of air and small convective heat transfer coefficient existing in the cooling system of the photovoltaic-thermal air collector through structural innovation and optimization, thereby synergistically improving the solar photovoltaic and photothermal conversion rates and maximizing the utilization rate of solar energy.

[0004] The photovoltaic-thermal air-type collector with enhanced heat transfer provided by the present invention includes a housing, a photovoltaic cell, a substrate and fins. The photovoltaic cell is attached to the bottom surface of the light-transmitting plate on the top of the housing, the bottom of the photovoltaic cell is attached to the top surface of the substrate, several rows of fins are assembled transversely in the inner cavity of the housing, and several rows of fins are assembled longitudinally in the inner cavity of the housing.

[0005] The light-transmitting plate on the top of the housing is composed of two layers of matte tempered glass plates, and a vacuum is provided between the two layers of matte tempered glass plates.

[0006] The substrate is a three-layer structure. The top layer of the substrate is a transparent PET plate, the photovoltaic cell is bonded to the PET plate through EVA glue, the middle layer of the substrate is an absorption film, and the bottom layer of the substrate is a metal layer with high thermal conductivity. The absorption film in the middle layer of the substrate is a selective absorption film, the material of the absorption film is reduced graphene oxide, the solar light absorption rate of the absorption film is 0.92, and the thermal emissivity is 4%. The matte tempered glass plate at the bottom layer of the substrate and the transparent PET plate are bonded through EVA glue.

[0007] The fins are made of metal plates with high thermal conductivity. The fins include Venturi fins and curved flow guiding fins. Among them, several columns of transverse Venturi fins are arranged in the inner cavity of the shell, and several rows of longitudinal Venturi fins are arranged in the inner cavity of the shell. The front and rear rows of Venturi fins are staggered. The curved flow guiding fins are assembled at the lower part of each air mixing interval gap between adjacent rows of Venturi fins. Several rows of curved flow guiding fins are also assembled. The curved flow guiding fins are arranged transversely through the inner cavity of the shell. The two ends of the curved flow guiding fins are fixedly connected to the inner walls on both sides of the inner cavity of the shell. A set gap is reserved between the bottom edge of the first row of curved flow guiding fins and the bottom surface of the inner cavity of the shell. The set gap between the bottom edge of the curved flow guiding fins and the bottom surface of the inner cavity of the shell gradually becomes smaller from the front row to the rear row. The bottom edge of the last row of curved flow guiding fins is fixedly connected to the bottom surface of the inner cavity of the shell.

[0008] The cross-section of the Venturi fin is U-shaped, and the Venturi fin is integrally formed. Among them, wing plates are respectively extended from the top ends of the side plates on both sides of the Venturi fin. The side plates on both sides of the Venturi fin are perpendicular to the bottom plate. The wing plates are perpendicular to the top ends of the side plates. The top surface of the wing plate is attached to the bottom surface of the substrate on the top surface of the shell. The bottom plate of the Venturi fin is a curved plate that gradually extends upward from front to back. The distance between the bottom plate and the top end of the side plate at the opening of the Venturi fin is greater than the distance between the bottom plate and the top end of the side plate at the outlet of the Venturi fin. The air flow channel formed in the inner cavity of the Venturi fin gradually shrinks from front to back.

[0009] The two side plates and the bottom plate of the shell are filled with heat insulation materials.

[0010] The working principle of the present invention:

[0011] When the photovoltaic-thermal air type collector for enhanced heat transfer provided by the present invention is in use, part of the sunlight irradiates on the photovoltaic cell panel, and the photovoltaic cell panel generates electric energy. Part of the sunlight irradiates on the absorption film in the middle layer of the substrate through the transparent PET plate on the top layer of the substrate. Due to the low emissivity of the absorption film to the environment and the high absorption ratio to the solar spectrum, this part of the sunlight is efficiently converted into heat energy, and the radiative heat transfer of the absorption film to the environment is extremely low. The heat absorbed by the absorption film heats the substrate, and this part of the heat energy is efficiently absorbed by the air and the Venturi fins inside the flow channel. At the same time, the temperature of the photovoltaic cell panel is greatly reduced, and the photoelectric conversion efficiency is improved.

[0012] According to two different heat transfer mechanisms, the heat of the substrate can be divided into two parts and efficiently absorbed by the air. There is a part of the substrate that fits the wing plate at the top end of the Venturi fin. The heat of this part of the substrate is efficiently absorbed by the wing plate and transferred to the side plate and the bottom plate of the Venturi fin through heat conduction; the part that does not fit the wing plate, the heat of this part is efficiently absorbed by the air through heat convection.

[0013] When air flows through the Venturi fins, the boundary layer will be regenerated on the staggered side plate wall and the bottom plate will be washed. Since the air flow channel formed in the inner cavity of the Venturi fin gradually shrinks from front to back, according to the Bernoulli equation, the air velocity increases and the pressure decreases after contraction. Therefore, the air at the outlet of the Venturi fin will thin the boundary layer in the local range of the substrate due to the increase in velocity, and will produce an induced effect on the air on the lower side of the Venturi fin outlet due to the decrease in pressure. In addition, after the air passes through the staggered scaling of the front and rear rows of Venturi fins, multiple longitudinal vortices can be induced in the mixing zone between the front and rear rows of Venturi fins, increasing the turbulence and forming multiple longitudinal vortex flows, thinning the boundary layer on the upper side of the mixing zone that is not attached to the wing plate substrate, enhancing the mixing of the upper air hot flow and the lower air cold flow, having a strong enhanced heat exchange effect, thereby improving the heat collection efficiency of the collector and synergistically improving the photoelectric conversion rate.

[0014] When air flows through the curved guide fins arranged in the mixing zone between the front and rear rows of Venturi fins, on the one hand, the curved design of the curved guide fins reduces the air flow resistance, and on the other hand, the gap set between the bottom edge of the curved guide fins and the bottom surface of the shell cavity gradually becomes smaller from the front row to the back row. The curved guide fins divide the air circulation space inside the flow channel near the bottom attachment of the shell into multiple layers, and guide it to the mixing zone layer by layer in the axial direction until the last curved guide fin against the bottom of the shell guides all the remaining air to the mixing zone, completely changing the entire flow direction of the air flowing through the curved fins, further increasing the turbulence in the mixing zone, promoting the mixing of cold and hot air flows, and thereby enhancing heat exchange and increasing the air temperature at the collector outlet.

[0015] The top of the shell is set as a double-layer vacuum structure of velvet tempered glass, which can effectively reduce the heat loss through the surface. The heat-insulating shell of the shell can effectively reduce the heat dissipation loss of the collector.

[0016] Beneficial effects of the present invention:

[0017] The photovoltaic thermal air-type collector with enhanced heat exchange provided by the present invention shows, according to the fluid streamline cloud diagram of the simulated three-dimensional steady-state experiment, that the fluid in the mixing zone between the front and rear rows of Venturi fins has multiple longitudinal vortices, the fluids on the upper and lower sides of the flow channel are violently mixed in the mixing zone, and the boundary layer on the substrate surface at the outlet of the Venturi fins is significantly thinned. This effect strongly proves the theoretical reliability of the present invention, and the enhanced heat transfer effect is obvious, which greatly improves the heat collection efficiency of the collector, synergistically improves the photovoltaic conversion efficiency, and maximizes the utilization of solar energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the air-type collector described in the present invention.

[0019] Figure 2This is a schematic diagram of the fin arrangement in the inner cavity of the air-type collector of the present invention without the top cover.

[0020] Figure 3 It is a schematic diagram of the longitudinal section of the air-type collector described in the present invention.

[0021] Figure 4 This is a top view of the arrangement of fins in the inner cavity of the air-type collector shell according to the present invention.

[0022] Figure 5 It is a schematic diagram of the Venturi fin structure of the present invention.

[0023] The annotations in the above figure are as follows:

[0024] 1. Shell 2. Photovoltaic cell 3. Substrate 4. Transparent plate 5. Venturi fin

[0025] 6. curved guide fins 7, side plates 8, wing plates 9, and bottom plates. DETAILED DESCRIPTION

[0026] See also Figures 1 to 5 As shown:

[0027] The photovoltaic thermal air type collector with enhanced heat exchange provided by the present invention includes a shell 1, a photovoltaic cell 2, a substrate 3 and fins, wherein the photovoltaic cell 2 is attached to the bottom surface of the light-transmitting plate 4 on the top of the shell 1, and the bottom of the photovoltaic cell 2 is attached to the top surface of the substrate 3. Several rows of fins are installed in the transverse direction of the inner cavity of the shell 1, and several rows of fins are installed in the longitudinal direction of the inner cavity of the shell 1.

[0028] The light-transmitting plate 4 on the top of the housing 1 is composed of two layers of velvet tempered glass plates, and a vacuum is set between the two layers of velvet tempered glass plates.

[0029] The substrate 3 is a three-layer structure, wherein the top layer of the substrate 3 is a transparent PET board, the photovoltaic cell 2 is bonded to the PET board by EVA glue, the middle layer of the substrate 3 is an absorption film, the bottom layer of the substrate 3 is a metal layer with high thermal conductivity, the absorption film in the middle layer of the substrate 3 is a selective absorption film, the material of the absorption film is reduced graphene oxide, the absorption film has a solar light absorption rate of 0.92, and a thermal emissivity of 4%, and the bottom layer of the velvet tempered glass plate of the substrate 3 is bonded to the transparent PET plate by EVA glue.

[0030] The fins are made of metal plates with high thermal conductivity. The fins include Venturi fins 5 and curved flow guiding fins 6. Among them, several rows of transverse Venturi fins 5 are arranged in the inner cavity of the housing 1, and several columns of longitudinal Venturi fins 5 are arranged in the inner cavity of the housing 1. The front and rear rows of Venturi fins 5 are staggered. The curved flow guiding fins 6 are assembled at the lower part of each air mixing interval between adjacent rows of Venturi fins 5. Several rows of curved flow guiding fins 6 are also assembled. The curved flow guiding fins 6 are arranged transversely through the inner cavity of the housing 1. The two ends of the curved flow guiding fins 6 are fixedly connected to the inner walls on both sides of the inner cavity of the housing 1. A set gap is reserved between the bottom edge of the first row of curved flow guiding fins 6 and the bottom surface of the inner cavity of the housing 1. The set gap between the bottom edge of the curved flow guiding fins 6 and the bottom surface of the inner cavity of the housing 1 gradually becomes smaller from the front row to the rear row, and the bottom edge of the last row of curved flow guiding fins 6 is fixedly connected to the bottom surface of the inner cavity of the housing 1.

[0031] The cross-section of the Venturi fin 5 is U-shaped, and the Venturi fin 5 is integrally formed. Among them, the top ends of the side plates 7 on both sides of the Venturi fin 5 are respectively extended with wing plates 8. The side plates 7 on both sides of the Venturi fin 5 are perpendicular to the bottom plate 9. The wing plate 8 is perpendicular to the top end of the side plate 7. The top surface of the wing plate 8 is attached to the bottom surface of the substrate 3 on the top surface of the housing 1. The bottom plate 9 of the Venturi fin 5 is a curved plate that gradually extends upward from front to back. The distance between the bottom plate 9 and the top end of the side plate 7 at the opening of the Venturi fin 5 is greater than the distance between the bottom plate 9 and the top end of the side plate 7 at the outlet of the Venturi fin 5. The air flow channel formed in the inner cavity of the Venturi fin 5 gradually shrinks from front to back.

[0032] The two side plates and the bottom plate of the housing 1 are filled with heat insulation materials.

[0033] The working principle of the present invention:

[0034] When the photovoltaic-thermal air type collector for enhanced heat transfer provided by the present invention is in use, a part of the sunlight irradiates on the photovoltaic cell 2, and the photovoltaic cell 2 generates electric energy. A part of the sunlight irradiates on the absorption film in the middle layer of the substrate 3 through the transparent PET plate on the top layer of the substrate 3. Due to the low emissivity of the absorption film to the environment and the high absorption ratio to the solar spectrum, this part of the sunlight is efficiently converted into heat energy, and the radiative heat transfer of the absorption film to the environment is extremely low. The heat absorbed by the absorption film heats the substrate 3, and this part of the heat energy is efficiently absorbed by the air and the Venturi fins 5 inside the flow channel. At the same time, the temperature of the photovoltaic cell 2 is greatly reduced, and the photoelectric conversion efficiency is improved.

[0035] According to two different heat transfer mechanisms, the heat of the substrate 3 can be divided into two parts and efficiently absorbed by the air. There is a part of the substrate 3 that fits the wing plate 8 at the top end of the Venturi fin 5. The heat of this part of the substrate 3 is efficiently absorbed by the wing plate 8 and transferred to the side plate 7 and the bottom plate 9 of the Venturi fin 5 through heat conduction; there is a part that does not fit the wing plate 8, and the heat of this part is efficiently absorbed by the air through heat convection.

[0036] When air flows through the Venturi fin 5, a boundary layer is regenerated on the wall surfaces of the staggered side plates 7, and the bottom plate 9 is washed. Since the air flow passage formed in the inner cavity of the Venturi fin 5 gradually narrows from front to back, according to Bernoulli's equation, it is deduced that the air velocity increases and the pressure decreases after contraction. Therefore, at the position where the Venturi fin 5 exits, the boundary layer in the local range of the substrate 3 is thinned due to the increase in velocity, and an entrainment effect is generated on the air below the exit of the Venturi fin 5 due to the decrease in pressure. In addition, after the air passes through the staggered scaling of the front and rear rows of Venturi fins 5, multiple longitudinal vortices can be induced in the mixing region between the front and rear rows of Venturi fins 5, increasing the turbulence intensity and forming a multi-longitudinal vortex flow, thinning the boundary layer of the substrate 3 of the wing plate 8 that is not attached on the upper side of the mixing region, enhancing the mixing of the upper-side hot air flow and the lower-side cold air flow, having a strong heat transfer enhancement effect, thereby improving the heat collection efficiency of the collector and synergistically improving the photoelectric conversion efficiency.

[0037] When air flows through the curved surface guide fin 6 arranged in the mixing region between the front and rear rows of Venturi fins 5, on the one hand, the curved surface design of the curved surface guide fin 6 reduces the air flow resistance. On the other hand, the gap between the bottom edge of the curved surface guide fin 6 and the bottom surface of the inner cavity of the housing 1 gradually becomes smaller from the front row to the rear row. The curved surface guide fin 6 divides the air flow space near the bottom of the housing 1 inside the flow passage into multiple layers and guides it layer by layer in the axial direction to the mixing region until the last curved surface guide fin 6 against the bottom of the housing 1 guides all the remaining air to the mixing region, completely changing the flow direction of all the air flowing through the curved surface fin 6, further increasing the turbulence intensity of the mixing region, promoting the mixing of the hot and cold air flows, and then enhancing heat transfer and increasing the air temperature at the outlet of the collector.

[0038] The top of the housing 1 is set as a double-layer vacuum structure of velvet tempered glass, which can effectively reduce the heat conduction loss through this surface. The heat-insulating outer shell of the housing 1 can effectively reduce the heat dissipation loss of the collector.

Claims

1. A photovoltaic-thermal air type collector for enhanced heat transfer, comprising a housing, a photovoltaic cell, a substrate and fins. The photovoltaic cell is attached to the bottom surface of a transparent plate at the top of the housing, and the bottom of the photovoltaic cell is attached to the top surface of the substrate. A plurality of rows of fins are assembled horizontally and vertically in the inner cavity of the housing. The transparent plate at the top of the housing is composed of two layers of frosted toughened glass plates, and a vacuum is provided between the two layers of frosted toughened glass plates. The substrate is a three-layer structure, wherein the top layer of the substrate is a transparent PET plate, the photovoltaic cell is bonded to the PET plate by EVA glue, the middle layer of the substrate is an absorption film, and the bottom layer of the substrate is a metal layer with high thermal conductivity. The absorption film in the middle layer of the substrate is a selective absorption film, and the material of the absorption film is reduced graphene oxide. The solar absorptance of the absorption film is 0.92, and the thermal emissivity is 4%. The bottom layer of the substrate and the transparent PET plate are bonded by EVA glue in the middle. It is characterized in that: The material of the fins is a metal plate with high thermal conductivity. The fins include Venturi fins and curved surface diversion fins. Among them, several rows of transverse Venturi fins are arranged in the inner cavity of the shell, and several columns of longitudinal Venturi fins are arranged in the inner cavity of the shell. The front and rear rows of Venturi fins are staggered. The curved surface diversion fins are assembled at the lower part of each air mixing interval gap between adjacent rows of Venturi fins. Several rows of curved surface diversion fins are also assembled. The curved surface diversion fins are arranged transversely through the inner cavity of the shell. Both ends of the curved surface diversion fins are fixedly connected to the inner walls on both sides of the inner cavity of the shell. A set gap is reserved between the bottom edge of the first row of curved surface diversion fins and the bottom surface of the inner cavity of the shell. The set gap between the bottom edge of the curved surface diversion fins and the bottom surface of the inner cavity of the shell gradually decreases from the front row to the rear row, and the bottom edge of the last row of curved surface diversion fins is fixedly connected to the bottom surface of the inner cavity of the shell.

2. The photovoltaic-thermal air collector for enhanced heat transfer according to claim 1, wherein: The cross-section of the Venturi fin is U-shaped, and the Venturi fin is integrally formed. Among them, wing plates are respectively extended at the tops of the side plates on both sides of the Venturi fin. The side plates on both sides of the Venturi fin are perpendicular to the bottom plate. The wing plates are perpendicular to the tops of the side plates. The top surface of the wing plate is attached to the bottom surface of the substrate on the top surface of the shell. The bottom plate of the Venturi fin is a curved plate that gradually extends upward from front to back. The distance between the bottom plate at the opening of the Venturi fin and the top of the side plate is greater than the distance between the bottom plate at the outlet of the Venturi fin and the top of the side plate. The air flow channel formed in the inner cavity of the Venturi fin gradually narrows from front to back.

3. The photovoltaic-thermal air type collector for enhanced heat transfer according to claim 1, characterized in that: The two side plates and the bottom plate of the shell are filled with thermal insulation materials.

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