A combined heat pipe flat plate solar collector

Abstract

The application discloses a combined heat pipe flat-plate solar collector in the technical field of solar heat utilization, which comprises a glass cover plate, a heat-absorbing body, a bottom plate, a frame and thermal insulation material, the heat-absorbing body is a plurality of heat-absorbing fins provided with a solar selective coating layer, a combined heat pipe is arranged below the heat-absorbing fins, the combined heat pipe comprises an upper metal horizontal pipe, a lower metal horizontal pipe and a plurality of metal vertical pipes, the metal vertical pipes are welded and communicated between the upper metal horizontal pipe and the lower metal horizontal pipe, the sun-facing side of a part of the metal vertical pipes is welded to the non-sun-facing side of the heat-absorbing fins, and at least one metal vertical pipe which is not connected with the fins is welded and connected between the upper metal horizontal pipe and the lower metal horizontal pipe; the combined heat pipe is filled with heat pipe medium; and a heat exchange structure part which can exchange heat with the heat pipe medium is arranged in the pipe or outside the pipe of the upper metal horizontal pipe. The combined heat pipe flat-plate solar collector has the advantages of anti-freezing performance, high heat efficiency and low cost.

Description

Technical Field

[0001] This invention relates to a flat-plate solar collector, belonging to the field of solar thermal utilization technology. Background Technology

[0002] Flat-plate solar collectors are currently the most widely used solar thermal utilization products both domestically and internationally. They have won favor with users due to their aesthetically pleasing appearance, reliable performance, and low failure rate. In Europe and North America, flat-plate solar collectors are almost exclusively used, and they account for over 60% of solar collectors in my country. However, existing flat-plate solar collectors have drawbacks such as low thermal efficiency and poor freeze resistance in cold regions. Although some remedial measures have been implemented, such as nighttime venting and filling with antifreeze or heat transfer oil, these measures have improved freeze resistance but have still increased the failure rate, reduced reliability, and have not improved thermal efficiency. Summary of the Invention

[0003] The purpose of this invention is to provide a combined heat pipe flat plate solar collector, which enables the flat plate solar collector to have antifreeze properties on its own, so that it can be used with confidence in cold or even frigid areas without the need for remedial measures, and the thermal efficiency (heat gain) is greatly improved and the cost is reduced.

[0004] To address this, the present invention provides a combined heat pipe flat-plate solar collector, comprising a glass cover, a heat absorber, a base plate, a frame, and insulation material. The heat absorber consists of several heat-absorbing fins with a solar selective coating layer. A combined heat pipe is disposed below the heat-absorbing fins. The combined heat pipe includes an upper metal horizontal pipe, a lower metal horizontal pipe, and several metal vertical pipes. The metal vertical pipes are welded between the upper and lower metal horizontal pipes. A portion of the metal vertical pipes are welded to the shaded side of the heat-absorbing fins on their sun-facing side. At least one of the metal vertical pipes not connected to the fins is welded between the upper and lower metal horizontal pipes. The upper metal horizontal pipe, lower metal horizontal pipe, metal vertical pipes connected to the fins, and metal vertical pipes not connected to the fins form a closed internal space, which is then evacuated and filled with heat pipe medium. A heat exchange structure is provided inside or outside the upper metal horizontal pipe for heat exchange with the heat pipe medium. Preferably, the heat pipe medium fills 75%-100% of the height of the metal vertical pipes.

[0005] The heat exchange structure transfers solar thermal energy from the heat-absorbing fins to the external hot water storage tank or to the pipeline for circulating heat exchange to a certain water tank.

[0006] Existing heat pipes consist of a shell, a wick, and a cap, with the inside of the pipe evacuated to 1.3X (10) -1 -10 -4After filling with a suitable amount of working fluid, the capillary porous material of the wick, which is tightly attached to the inner wall of the tube, is filled with working fluid and then sealed. When the tube wall comes into contact with a heat source, the liquid inside the tube immediately evaporates into gas and flows upward to the upper end of the tube. After dissipating heat through the upper tube wall, the gas immediately condenses into liquid and flows back to the lower end of the tube by the capillary force of the wick, completing the circulation of the medium. Heat pipe heat transfer utilizes the physical principles of two phase change heat transfer methods, evaporation and condensation, which are characterized by fast heat transfer speed (phase change occurs instantaneously) and huge heat transfer capacity (the heat of phase change is enormous).

[0007] Since existing heat pipe technologies cannot be directly used in flat-plate solar collectors, this invention proposes an innovative heat pipe structure for use in flat-plate solar collectors to better adapt to applications in frigid regions and further improve performance indicators such as thermal efficiency (heat gain).

[0008] This invention innovatively employs a novel and complex heat pipe structure. Several vertical metal tubes connect between the upper and lower horizontal metal tubes, creating a unique combination where some tubes are in contact with the heat source while others are not. This combination forms a new type of heat pipe, hence the name "combined heat pipe." The metal tubes in contact with the heat source become dedicated channels for the upward unidirectional flow of the liquid heat pipe medium as it evaporates into a gaseous state, while the metal tubes not in contact with the heat source, remaining in a cold state, become dedicated channels for the downward unidirectional flow of the condensed liquid heat pipe medium. This eliminates the need for a wick, allowing for a smaller tube diameter. Theoretically, the metal tubes in this combined heat pipe are also suitable for long, thin tubes with a high aspect ratio, significantly reducing costs. Furthermore, making all metal tubes unidirectional flows results in faster and smoother flow. In this invention, some metal tubes are welded to the solar absorber fins to be in contact with the heat source, while others are not. In fact, the reverse flow of the liquid heat pipe medium in the wick is generated by capillary force, and the flow rate in the wick is obviously very slow. However, the present invention makes the reverse flow of the liquid heat pipe medium much faster.

[0009] The working principle of this invention is as follows: When sunlight shines on the heat-absorbing fins, the generated heat is transferred to the liquid heat pipe medium in the metal vertical tube welded to the heat-absorbing fins. Upon heating, the liquid heat pipe medium instantly evaporates into a gaseous state. The heat transfer rate of evaporation is tens of times greater than the heat transfer rate through temperature difference. The gaseous heat pipe medium rapidly rises into the upper metal horizontal tube. Through the heat exchange structure corresponding to the upper metal horizontal tube, the gaseous heat pipe medium exchanges heat with the externally located hot water storage tank or heat exchange pipeline. This allows the gaseous heat pipe medium in the upper metal horizontal tube to instantly condense into a liquid heat pipe medium. The condensation instantly releases a large amount of heat to the externally located hot water storage tank or heat exchange pipeline. The resulting liquid heat pipe... The medium can only flow downwards in one direction along the metal vertical tubes that are not connected to the heat-absorbing fins. Because the metal vertical tubes that are not connected to the heat-absorbing fins are not heated and are in a cold state, the liquid heat pipe medium cannot overcome the huge resistance of the upward airflow in the heated metal vertical tubes and can only flow downwards without resistance into the lower metal horizontal tubes. Then, the space of 75%-100% of the height of the metal vertical tubes is refilled with liquid heat pipe medium, completing the circulation of the heat pipe medium. In this way, the medium continuously evaporates after being heated, condenses after heat transfer, and continuously flows and circulates in one direction, so that the solar heat energy received by the heat-absorbing fins is continuously transferred to the external hot water storage tank or the external heat exchange pipes through the heat exchange structure.

[0010] The heat pipe medium of this invention uses a mixture of several existing antifreeze media liquids. It has a low start-up temperature, evaporating into a gaseous state at around 30°C. This invention allows the collector to instantly and rapidly transfer a large amount of heat to the heat exchange structure and then to the external water tank or external pipes at around 30°C. Therefore, the air temperature under the glass cover of the combined heat pipe flat-plate solar collector of this invention is much lower than that under the glass cover of the existing flat-plate solar collectors. The heat loss through the glass cover is greatly reduced, which is the theoretical basis for the improved thermal efficiency (heat gain) of the product of this invention.

[0011] The beneficial effects of this invention are as follows: the solar collector itself has excellent anti-freeze performance (the heat pipe medium is anti-freeze), extremely high reliability, extremely low failure rate (the heat pipe medium is in a welded and sealed space, eliminating the possibility of leakage), reduced cost (eliminating the need for a liquid absorber core and reducing the pipe diameter), and significantly improved thermal efficiency. It can be used to manufacture rooftop solar water heaters, balcony railing solar water heaters, and collector arrays for large-area projects.

[0012] Furthermore, the heat-absorbing fins are integrated into one piece, which simplifies the manufacturing process and reduces costs. Commonly used fin materials include copper plates and aluminum plates, with copper tubes being the optimal metal tube. The optimal welding method is laser welding, which can weld copper tubes to copper plates or to aluminum plates. This automated welding process offers high quality and efficiency. Brazing and other welding methods can also be used.

[0013] Furthermore, the metal risers not connected to the fins are located in the space on the shaded side of the metal risers connected to the fins, and the metal risers not connected to the fins are arranged at uniform intervals. In this way, the metal risers not connected to the fins do not receive solar heat energy and remain in a cold state, while the metal risers connected to the fins receive solar heat energy, and the liquid heat pipe medium therein evaporates into a gaseous heat pipe medium, rushing upwards into the upper metal horizontal tube. After heat exchange with the external water tank or external pipes through the heat exchange structure, it condenses back into a liquid heat pipe medium. This liquid heat pipe medium faces significant upward airflow resistance in the metal risers connected to the fins and can only flow downwards without resistance along the cold metal risers not connected to the fins. The metal vertical tubes, not connected to the fins, are arranged at uniform intervals, allowing the liquid heat pipe medium to circulate locally and uniformly. This ensures seamless and uniform circulation across all areas, maximizing the overall circulation speed. The medium flows back into the lower metal horizontal tubes, filling 75%-100% of the height of all the metal vertical tubes. This is a dynamic and continuous circulation process of the heat pipe medium. This design optimizes this dynamic circulation, minimizing flow resistance, pipe diameter (lowest cost), circulation speed, heat transfer, and air temperature below the collector glass cover, thus minimizing heat loss through the glass cover and maximizing the collector's thermal efficiency. This is the theoretical basis for the highest thermal efficiency achieved by the combined heat pipe flat-plate solar collector of this invention among flat-plate solar collector products.

[0014] The combined heat pipe structure of this invention, regardless of the length of the upper metal horizontal tube (e.g., 4.5 meters, with the collector used as a balcony railing), allows the gaseous heat pipe medium flowing upwards into the upper metal horizontal tube to exchange heat with the heat exchange tube (e.g., 4.5 meters long) along the entire length of the upper metal horizontal tube, and then circulate and exchange heat with the external water tank. The medium in the upper metal horizontal tube and the medium in the heat exchange tube are only separated by the metal tube wall (copper tubes are preferred for faster heat transfer), resulting in almost zero heat transfer distance. It is entirely local heat exchange, and the heat transfer is carried out through phase change (condensation) (occurring instantaneously). The heat exchange of the upper metal horizontal tube to the outside is uniform and rapid, which is obviously the most optimized approach.

[0015] Furthermore, the metal vertical tubes connected to the fins and those not connected to the fins are located in the same layer; the metal vertical tubes not connected to the fins are welded together at one or both ends of the upper and lower metal horizontal tubes, and are located within the space of the frame on both sides. For combined heat pipe flat-plate solar collectors with a small width, fewer return channels are needed. This arrangement utilizes the space of the frame on both sides of the flat-plate solar collector. The metal vertical tubes not connected to the fins are neither in contact with the heat source nor exposed to sunlight in this space, remaining in a cold state, providing an ideal dedicated channel for the return of liquid heat pipe medium. This also allows for a thinner collector, which is beneficial for cost savings.

[0016] Furthermore, the heat exchange structure is a heat exchange tube that axially passes through the upper metal horizontal tube. Alternatively, the heat exchange structure can be an outer sleeve axially fitted over the upper metal horizontal tube. Both ends of the heat exchange tube or the outer sleeve can be connected to a domestic hot water storage tank via insulated pipes to form natural convection heat exchange, or a water pump can be added to form forced circulation heat exchange. Both ends of the heat exchange tube can also be connected in parallel with two main circulation pipes via insulated pipes to form a collector group for a large-area heat collection project. The outer sleeve can be directly used as a circulation heat exchange pipe when several collectors are connected in series; simply connect the outer sleeves of each collector in series using connecting pipes.

[0017] Furthermore, the heat exchange structure is a heat exchange tube connected side-by-side with the upper metal horizontal tube. The optimal side-by-side connection is welding, but clamps can also be used for this connection.

[0018] Furthermore, the heat exchange structure is an arc-shaped heat transfer plate welded to the upper metal horizontal pipe, and the arc-shaped heat transfer plate is tightly connected to a separately provided circular water tank liner or circular pipe. The arc-shaped heat transfer plate allows heat to be directly and quickly transferred to the water in the arc-shaped water tank or the arc-shaped pipe, minimizing or even eliminating the heat transfer distance. This direct transfer helps reduce heat loss.

[0019] Furthermore, the heat exchange structure is an arc-shaped heat transfer plate welded to the upper metal horizontal tube. The arc-shaped heat transfer plate is tightly connected to the inner liner of a separately installed circular water tank via an extended and widened arc-shaped heat transfer plate. This extended and widened arc-shaped heat transfer plate is tightly attached to the arc-shaped heat transfer plate, and the connection between the extended and widened arc-shaped heat transfer plate and the inner liner of the circular water tank is secured with a clamp. This design facilitates the installation, packaging, and transportation of the extended and widened arc-shaped heat transfer plate along with the circular water tank, while the non-extended arc-shaped heat transfer plate is welded, packaged, and transported along with the solar collector.

[0020] Furthermore, the heat exchange structure is a blind tube inserted into the upper metal horizontal tube from one end. The blind tube is sealed and welded to one end of the upper metal horizontal tube, and the open end of the blind tube faces outward. The open end of the blind tube serves as the insertion port for a heat transfer connector. The open end of the blind tube can also be an insertion port for a heat transfer pipe, and the heat dissipation end of the heat transfer pipe can be inserted into the lower part of a domestic hot water storage tank. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention.

[0022] Figure 2 This is a schematic diagram of the structure of the present invention after the aluminum alloy frame, glass cover and insulation material have been removed.

[0023] Figure 3 for Figure 2 A magnified view of part A in the image.

[0024] Figure 4 To and Figure 3 The corresponding improved structure of the present invention.

[0025] Figure 5 This is a schematic diagram of the structure of the present invention corresponding to Example 2.

[0026] Figure 6 A schematic diagram of the structure of the present invention corresponding to Example 5.

[0027] Figure 7 A schematic diagram of the structure of the present invention corresponding to Example 4.

[0028] Figure 8 A schematic diagram of the structure of the present invention corresponding to Example 6.

[0029] In the diagram, 1 is a water tank, 2 is an arc-shaped heat transfer fin, 3 is an upper metal horizontal tube, 4 is a metal vertical tube connected to the fins, 5 is a glass cover, 6 is a metal vertical tube not connected to the fins, 7 is insulation material, 8 is a base plate, 9 is a lower metal horizontal tube, 10 is a heat-absorbing fin, 11 is a heat exchange tube, 12 is an outer jacket, and 13 is an extended and widened arc-shaped heat transfer fin. Detailed Implementation Example 1

[0030] like Figure 1-4As shown, this is a household combined heat pipe flat-plate solar water heater. Its structure mainly includes a glass cover plate 5, a heat absorber, a base plate 8, a frame, and insulation material 7. The heat absorber consists of several heat-absorbing fins 10 with a solar selective coating layer. The heat-absorbing fins 10 are connected as one unit (or can be separate units). A combined heat pipe is located below the heat-absorbing fins 10. The combined heat pipe includes an upper metal horizontal pipe 3, a lower metal horizontal pipe 9, and several metal vertical pipes. The metal vertical pipes are welded and connected between the upper metal horizontal pipe 3 and the lower metal horizontal pipe 9. A portion of the metal vertical pipes 4... The sun-facing side of the heat-absorbing fin 10 is welded to the shaded side. At least one metal vertical tube 6, which is not connected to the fin, is welded between the upper metal horizontal tube 3 and the lower metal horizontal tube 9. The upper metal horizontal tube 3, the lower metal horizontal tube 9, the metal vertical tube 4 connected to the fin, and the metal vertical tube 6 not connected to the fin are welded to form a closed internal space. After being evacuated, the space is filled with heat pipe medium, which fills 75%-100% of the height of the metal vertical tube. The upper metal horizontal tube 3 is provided with heat exchange structure components that can exchange heat with the heat pipe medium inside or outside the tube.

[0031] The metal risers 6 not connected to the fins are located in the space on the shaded side of the metal risers 4 connected to the fins, and the metal risers 6 not connected to the fins are arranged at uniform intervals. In this way, the metal risers 6 not connected to the fins do not receive solar heat energy and are in a cold state, while the metal risers 4 connected to the fins receive solar heat energy, and the liquid heat pipe medium in them evaporates into a gaseous heat pipe medium, which rushes upward into the upper metal horizontal pipe 3. After heat exchange with the external water tank or external pipe through the heat exchange structure, it condenses into a liquid heat pipe medium. These liquid heat pipe media will encounter huge resistance to the upward airflow in the metal risers 4 connected to the fins, and can only flow downward without resistance along the cold metal risers 6 not connected to the fins. The metal vertical tubes 6, not connected to the fins, are arranged at uniform intervals, allowing the liquid heat pipe medium to circulate locally and nearby. This ensures uniform and consistent circulation across all areas, maximizing the overall circulation speed. The medium flows back into the lower metal horizontal tube 9, filling 75%-100% of the height of all the metal vertical tubes. This is a dynamic and continuous circulation process of the heat pipe medium. This design optimizes this dynamic circulation, minimizing flow resistance, pipe diameter (lowest cost), circulation speed, heat transfer, and air temperature below the collector glass cover, thus minimizing heat loss through the glass cover and maximizing the collector's thermal efficiency. This is the theoretical basis for the highest thermal efficiency of the combined heat pipe solar flat plate collector of this invention.

[0032] like Figure 3 As shown, the heat exchange structure is an arc-shaped heat transfer plate 2 welded to the upper metal horizontal tube 3. The arc-shaped heat transfer plate 2 is tightly connected to the inner liner of the separately provided circular water tank 1.

[0033] The working principle of this invention is as follows: When sunlight shines on the heat-absorbing fins 10, a large amount of heat is generated and transferred to the liquid heat pipe medium in the metal vertical tube 4 welded to the heat-absorbing fins 10. Upon heating, the liquid heat pipe medium rapidly evaporates into a gaseous state and quickly rises into the upper metal horizontal tube 3. The gaseous heat pipe medium exchanges heat with the externally installed heat exchange pipes or the hot water storage tank 1 through the heat exchange structure corresponding to the upper metal horizontal tube 3. This allows the gaseous heat pipe medium in the upper metal horizontal tube 3 to immediately condense into a liquid heat pipe medium. Unable to overcome the enormous resistance of the rising hot airflow in the heated metal vertical pipe, the medium can only flow downwards without resistance along the cold metal vertical pipe 6, which is not connected to the heat-absorbing fins. The liquid heat pipe medium flows directly downwards into the lower metal horizontal pipe 9, allowing the space at a certain height at the bottom of the metal vertical pipe to be refilled with liquid heat pipe medium, thus completing the circulation of the heat pipe medium. In this way, through continuous heating and evaporation, heat transfer and condensation, and continuous circulation of the medium, the solar thermal energy received by the heat-absorbing fins 10 is continuously transferred directly to the hot water storage tank 1 through the heat exchange structure.

[0034] Its further improvements include Figure 4 As shown, the heat exchange structure consists of an arc-shaped heat transfer plate 2 welded to the upper metal horizontal tube 3. The arc-shaped heat transfer plate 2 is tightly connected to the inner liner of the separately installed circular water tank 1 via an extended and widened arc-shaped heat transfer plate 13. The extended and widened arc-shaped heat transfer plate 13 is tightly connected to the arc-shaped heat transfer plate 2 and to the inner liner of the circular water tank 1, and is tightened with a clamp. The heat exchange structure here is composed of the arc-shaped heat transfer plate 2 and the extended and widened arc-shaped heat transfer plate 13. The arc-shaped heat transfer plate 2 is small in size and is welded to the upper metal horizontal tube 3, so it can be packaged and transported with the collector. The extended and widened arc-shaped heat transfer plate 13 is large in size, making it more reasonable to install, package, and transport it with the hot water storage tank 1. During on-site installation, the arc-shaped heat transfer plate 2 and the extended and widened arc-shaped heat transfer plate 13 are installed in close contact. Bolts can be pre-welded onto the extended and widened arc-shaped heat transfer plate 13, and the two are tightened with nuts. The extended and widened arc-shaped heat transfer plate 13 increases the heat transfer area, which is beneficial to enhancing the heat transfer effect.

[0035] The heat pipe medium in this invention's combined heat pipe is a liquid formulated with easily evaporable (evaporating at around 30°C, instantly absorbing large amounts of solar heat energy from the fins) and cold-resistant materials. It is resistant to temperatures down to -50°C or even lower without freezing, thus making the collector itself cold-resistant and freeze-proof. The heat pipe medium in this invention's combined heat pipe is housed in a welded, sealed copper tube, eliminating concerns about leakage, resulting in an extremely low failure rate and extremely high reliability.

[0036] Like all flat-plate solar collectors, this invention features insulation material 7 on all four sides and five directions below the collector. Heat loss primarily occurs through the glass cover 5, with the greater the temperature difference between the upper and lower sides of the glass cover 5, the greater the heat loss. Existing flat-plate solar collectors have a slow heat transfer rate due to the limited flow rate of the water medium. If antifreeze or heat transfer oil is used, its heat capacity is even lower than water, resulting in an even slower heat transfer rate and an inability to quickly dissipate the acquired heat. Consequently, the temperature below the glass cover 5 is relatively high. In contrast, the combined heat pipe of this invention provides extremely fast heat transfer, utilizing evaporation and condensation for instantaneous and rapid large-volume heat transfer. The air temperature below the glass cover 5 is significantly lower than that of existing collectors, significantly reducing heat loss through the glass cover 5. Furthermore, this embodiment theoretically brings the heat transfer distance between the collector and the hot water storage tank 1 to near zero, minimizing heat loss during the heat transfer process. Therefore, the overall thermal efficiency (or heat gain) of this combined heat pipe flat-plate solar water heater is significantly improved.

[0037] Because of the innovative and ingenious design of the combined heat pipe of this invention, the liquid wick in the pipe is eliminated, which greatly reduces the pipe diameter. The metal vertical tube of the combined heat pipe of this invention is theoretically suitable for using long and thin tubes with a large length-to-diameter ratio, which can greatly reduce the cost. This is because the medium in all metal vertical tubes can achieve unidirectional flow, some flowing upward and some flowing downward, and the flow rate is faster and smoother. Compared with the existing flat plate solar collectors, the amount of copper used is reduced by half, thus reducing the cost.

[0038] The beneficial effects of this invention are as follows: Because the heat pipe medium in this combined heat pipe flat-plate solar water heater is resistant to freezing, and heat transfer is achieved through direct, zero-distance contact, there are no weak points in its anti-freezing performance. Its excellent anti-freezing performance is ensured by the heat pipe medium being contained within a welded, sealed space, eliminating the possibility of leakage. This results in extremely high reliability, a very low failure rate, significantly improved thermal efficiency, and reduced costs. In extremely cold regions, if double-layered vacuum-tempered glass is used for the cover glass, the thermal efficiency (heat gain) of this embodiment can be further improved. Example 2

[0039] Adopting such Figure 5 The heat exchange tube 11 shown differs from that in Embodiment 1 in that the heat exchange structure is a heat exchange tube 11 connected side-by-side with the upper metal horizontal tube 3. A welded connection is preferred.

[0040] Alternatively, it can be used Figure 7 The heat exchange tube 11 shown operates on the same principle and has the same effect.

[0041] A solar water heating system that can be used as a balcony railing mainly includes a glass cover plate 5, a heat absorber 10, a base plate 8, a frame, and insulation material 7. The heat absorber consists of several heat-absorbing fins 10 with a solar selective coating layer, which are connected as a single unit (or can be separate units). A combined heat pipe is installed below the heat-absorbing fins 10. The combined heat pipe includes an upper metal horizontal pipe 3, a lower metal horizontal pipe 9, and several metal vertical pipes. The metal vertical pipes are welded and connected between the upper metal horizontal pipe 3 and the lower metal horizontal pipe 9. A portion of the metal vertical pipes 4... The sun-facing side of the heat-absorbing fin 10 is welded to the shaded side. At least one metal vertical tube 6, which is not connected to the fin, is welded between the upper metal horizontal tube 3 and the lower metal horizontal tube 9. The upper metal horizontal tube 3, the lower metal horizontal tube 9, the metal vertical tube 4 connected to the fin, and the metal vertical tube 6 not connected to the fin are welded to form a closed internal space. After being evacuated, the space is filled with heat pipe medium, which fills 75%-100% of the height of the metal vertical tube. The upper metal horizontal tube 3 is provided with heat exchange structure components that can exchange heat with the heat pipe medium inside or outside the tube.

[0042] The heat-absorbing fins 10 are connected as one unit. The metal vertical tubes not connected to the fins are located in the space on the shaded side of the metal vertical tube 4 connected to the fins. The metal vertical tubes 6 not connected to the fins are arranged at uniform intervals.

[0043] The solar water heating system used as a balcony railing employs a vertical, jacketed, pressurized water tank 1, which can also be a non-jacketed pressurized water tank, mounted on the inner wall of the balcony. The collector backplate is made of thicker galvanized sheet, and a long, channel-shaped guardrail connecting to the left and right walls is installed close to the top of the collector for safety. The collector can be designed to be 3.5-4.5 meters long horizontally, with its vertical dimensions matching the height of the balcony railing. The solar collector is perpendicular to the balcony floor, serving as the balcony railing. Due to the large horizontal dimension of the collector, 5-7 metal vertical pipes 6, not connected to the fins, are welded between the upper metal horizontal pipe 3 and the lower metal horizontal pipe 9. These non-finned metal vertical pipes 6 are located in the space on the shaded side of the metal vertical pipes 4 connected to the fins, and are evenly spaced.

[0044] The left and right ends of the heat exchange tube 11 are connected to the two interfaces of the pressurized water tank jacket via two insulated heat exchange pipes. To prevent the pipe connections from being too messy, a portion of one of the two external circulation pipes can be placed inside the insulation material 7 of the upper frame of the collector, so that the insulated heat exchange pipe can start from one end of the collector and connect to the interface of the vertical pressurized water tank. The heat exchange circulation adopts natural circulation, but forced circulation by a water pump can also be used. Since the back of the collector is located in an enclosed balcony, the environmental conditions of the heat exchange tube 11 connected in parallel with the upper metal horizontal pipe 3 and the external insulated heat exchange pipe are not as harsh as the outdoor ambient temperature. As long as antifreeze measures such as using a heating tape (which can reach a constant temperature of 40°C when powered) are adopted, the combined flat plate solar collector of this invention is undoubtedly antifreeze (the heat pipe medium can be configured to be used safely under low temperature and severe cold conditions).

[0045] Regarding balcony-mounted solar water heating systems, in cold regions of the Northern Hemisphere at latitudes of 45°-60°, the corresponding solar altitude angle at noon on the winter solstice is 21.57°-6.57°, with Cos21.57°=0.93 and Cos6.57°=0.9934. For the collectors installed perpendicular to the ground, as advocated in this invention, the effective heat collection area ratio at noon on the winter solstice is between 93% and 99.34%. The higher the latitude, the higher the effective heat collection area ratio, approaching 100%. Outside of noon, the solar altitude angle is lower, and the effective heat collection area ratio is naturally even closer to 100%, far exceeding the effective heat collection area ratio in low-latitude southern regions. In southern regions, collectors need a certain tilt angle for optimal performance; in high-latitude regions, tilting is not necessary, and perpendicular installation actually yields better results in winter. The effective light-receiving area per household can reach over 4 square meters in winter, with some units even approaching 5 square meters. Therefore, when used as a balcony railing, it provides ample hot water, making it the best choice for high-latitude regions.

[0046] The desired effect is that it can be installed perpendicular to the ground and used directly as a balcony railing, which is beautiful, sturdy and reliable. The effective heat collection area ratio is particularly high in winter, and it provides more abundant domestic hot water during the cold season when hot water is most needed.

[0047] When used in extremely cold regions, if the cover glass is made of double-layered vacuum-tempered glass (which is a material in existing technology), the hot water system in this embodiment can further improve the thermal efficiency (heat gain) index. Example 3

[0048] A combined heat pipe rooftop flat-plate solar water heater is almost identical to Embodiment 2, except that the water tank 1 is horizontal and the heat exchange circulation pipes are shorter. This water heater, composed of a combined heat pipe flat-plate solar collector, can be installed and used on flat or pitched roofs. The only difference is that the hot water storage tank 1 is a horizontal, jacketed, pressurized tank. The two ends of the heat exchange pipe 11 are connected to the two ends of the jacket of the water tank 1 via two short metal corrugated pipes. The area between the hot water storage tank 1 and the collector is filled with insulation material 7, and a removable outer shell is provided for easy maintenance. When the pressurized tank 1 is full, it always retains residual heat. The heat exchange pipe 11 and the metal corrugated pipes are all within the residual heat insulation material 7, providing favorable conditions for freeze protection. Adding a heating cable provides a second layer of protection against freeze. Alternatively, antifreeze can be used as the heat exchange circulation medium for freeze protection.

[0049] The heat exchange cycle uses natural circulation, but forced circulation using a water pump can also be used.

[0050] The collector in this embodiment is self-freezing, the system is reliable, the failure rate is low, the thermal efficiency (heat gain) is high, and the cost is reduced. Theoretically and practically, it is unmatched by various existing flat-plate solar collectors. Example 4

[0051] like Figure 7 As shown, the heat exchange structure is a heat exchange tube 11 connected side-by-side with the upper metal horizontal tube 3. The optimal side-by-side connection method is welding, but clamps can also be used for side-by-side connection. The difference from embodiment 3 is that the heat exchange tube 11 has a partially concave arc-shaped surface, which fits tightly with the upper metal horizontal tube 3. The side-by-side connection between the two can be welding or clamps.

[0052] This embodiment is applicable to balcony-type solar water heaters and rooftop solar water heaters, and is also suitable for forming large-area collector groups. Example 5

[0053] like Figure 6 As shown, the difference from Embodiment 1 is that the metal vertical pipe 4 connected to the fins and the metal vertical pipe 6 not connected to the fins are located in the same layer; the metal vertical pipe 6 not connected to the fins is welded to one or both ends of the upper metal horizontal pipe 3 and the lower metal horizontal pipe 9, and the metal vertical pipe 6 not connected to the fins is located in the space of the frame itself on both sides. The heat exchange structure is a heat exchange tube 11 that passes axially through the upper metal horizontal pipe 3. This embodiment is applicable to small rooftop solar water heaters.

[0054] Heat exchange structural components can also be adopted as follows Figure 5 or Figure 7 Replace the heat exchange tube 11 shown. Example 6

[0055] like Figure 8 As shown, the difference from Embodiment 1 is that the heat exchange structure can also be an outer sleeve 12 axially fitted outside the upper metal horizontal tube 3. The upper metal horizontal tube 3 is directly disposed in the outer sleeve 12 and is a metal tube thicker than the upper metal horizontal tube 3, such as a stainless steel tube or a galvanized tube. The outer sleeve 12 then becomes part of the heat exchange circulation pipeline, suitable for situations where several collectors are connected in series to form a large-area collector group, simply by connecting the outer sleeves 12 of each collector in series with connecting pipes.

[0056] Placing the metal horizontal tube 3 in the outer tube 12 is a bit complicated. The best approach is to first drill holes in a semi-circular stainless steel tube so that several metal vertical tubes 4 of the semi-finished combined heat pipe can pass through the drilled holes. Then, weld another semi-circular stainless steel tube to the drilled semi-circular stainless steel tube to form the outer tube 12. Finally, complete the welding of other parts. Example 7

[0057] The difference from Embodiment 2 (Balcony-type Hot Water System) is that the heat exchange structure is a blind pipe inserted into the upper metal horizontal pipe 3 from one end. The blind pipe is sealed and welded to one end of the upper metal horizontal pipe 3, with the open end of the blind pipe facing outwards. The open end of the blind pipe serves as the insertion port for the external heat transfer connector. The open end of the blind pipe can also be an insertion port for a heat transfer pipe, whose heat dissipation end can be inserted into the lower part of the domestic hot water storage tank 1. A connecting pipe is welded to the lower part of the tank 1, extending out of the tank 1. A sufficiently large gap is left between the inner wall of the connecting pipe and the heat pipe radiator head to facilitate easy removal of the heat pipe radiator head when scale accumulates in the tank 1 and needs cleaning. The connecting pipe has external threads. After the heat pipe radiator head is inserted into the tank 1 through the connecting pipe, a pressure-bearing sealing connection is achieved using a nut and a silicone gasket. This embodiment is applicable to small balcony-type solar water heaters.

[0058] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A combined heat pipe flat-plate solar collector, comprising a glass cover, a heat absorber, a base plate, a frame, and insulation material, characterized in that: The heat absorber consists of several heat-absorbing fins with a solar selective coating. A combined heat pipe is located below the heat-absorbing fins. The combined heat pipe includes an upper metal horizontal tube, a lower metal horizontal tube, and several metal vertical tubes. The metal vertical tubes are welded between the upper and lower metal horizontal tubes. The sun-facing side of a portion of the metal vertical tubes is welded to the shaded side of the heat-absorbing fins. At least one of the other metal vertical tubes, which are not connected to the fins, is welded between the upper and lower metal horizontal tubes. The upper metal horizontal tube, the lower metal horizontal tube, the metal vertical tubes connected to the fins, and the metal vertical tubes not connected to the fins are welded together to form a closed internal space, which is then evacuated and filled with heat pipe medium. The upper metal horizontal tube has heat exchange structures inside or outside that can exchange heat with the heat pipe medium.

2. The combined heat pipe flat-plate solar collector according to claim 1, characterized in that, The heat-absorbing fins are connected as one piece.

3. A combined heat pipe flat-plate solar collector according to claim 1 or 2, characterized in that, The metal vertical tubes not connected to the fins are located in the space on the shaded side of the metal vertical tubes connected to the fins, and the metal vertical tubes not connected to the fins are arranged at uniform intervals.

4. A combined heat pipe flat-plate solar collector according to claim 1 or 2, characterized in that, The metal vertical tubes connected to the fins and the metal vertical tubes not connected to the fins are located in the same layer; the metal vertical tubes not connected to the fins are welded to each other at one or both ends of the upper metal horizontal tube and the lower metal horizontal tube, and the metal vertical tubes not connected to the fins are set in the space of the frame itself on both sides.

5. A combined heat pipe flat-plate solar collector according to claim 1 or 2, characterized in that, The heat exchange structure is a heat exchange tube that passes axially through the upper metal horizontal tube.

6. A combined heat pipe flat-plate solar collector according to claim 1 or 2, characterized in that, The heat exchange structure is an outer sleeve axially fitted outside the upper metal horizontal tube.

7. A combined heat pipe flat-plate solar collector according to claim 1 or 2, characterized in that, The heat exchange structure is a heat exchange tube connected in parallel with the upper metal horizontal tube.

8. A combined heat pipe flat-plate solar collector according to claim 1 or 2, characterized in that, The heat exchange structure is an arc-shaped heat transfer plate welded to the upper metal horizontal pipe. The arc-shaped heat transfer plate is tightly connected to the inner liner of a separate circular water tank or a circular pipe.

9. A combined heat pipe flat-plate solar collector according to claim 1 or 2, characterized in that, The heat exchange structure is an arc-shaped heat transfer plate welded to the upper metal horizontal tube. The arc-shaped heat transfer plate is tightly connected to the inner liner of the circular water tank by an extended and widened arc-shaped heat transfer plate. The extended and widened arc-shaped heat transfer plate is tightly connected to the arc-shaped heat transfer plate, and the extended and widened arc-shaped heat transfer plate is tightly connected to the inner liner of the circular water tank and is tightened by a clamp.

10. A combined heat pipe flat-plate solar collector according to claim 1 or 2, characterized in that, The heat exchange structure is a blind tube inserted into the upper metal horizontal tube from one end. The blind tube is sealed and welded to one end of the upper metal horizontal tube. The open end of the blind tube faces outward and serves as the insertion port for the plug-in component for external heat transfer.

Images