A waste heat utilization device

Abstract

This invention provides a waste heat utilization device, relating to the field of waste heat recovery and utilization technology. It includes a first heat exchanger, a second heat exchanger, a collection device, and a switching device. The first and second heat exchangers are connected in parallel and then connected to a heat source. The switching device is used to switch the connection mode of the first and second heat exchangers, so that the first and second heat exchangers are connected in series and then connected to the heat source. When the heat source air temperature is ≥140℃, the first and second heat exchangers are in series mode; when the heat source air temperature is <100℃, the first and second heat exchangers are in parallel mode; when the heat source air temperature is between 100℃ and 140℃, the first and second heat exchangers operate in a mixed state of series or parallel connection. This invention enables adaptive system adjustment based on the heat source temperature, thereby improving heat source utilization efficiency.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery and utilization technology, and more specifically, to a waste heat utilization device. Background Technology

[0002] Waste heat recovery technology is widely used in numerous fields such as industrial boilers, kilns, gas turbines, internal combustion engines, drying equipment, chemical reactors, and air conditioning and refrigeration systems. It recovers heat from flue gas or exhaust to preheat combustion air, heat feedwater, or provide heating, making it an important means of improving energy efficiency and reducing carbon emissions. In waste heat recovery systems requiring multi-stage heat exchangers, the connection between each stage directly determines the system's heat recovery efficiency and operating energy consumption. However, the connection method of multi-stage heat exchangers is usually fixed during the design phase. A common practice is to guide the heat transfer fluid through each stage of heat exchanger from inlet to outlet, thus gradually reducing the fluid temperature. This connection method allows the fluid to achieve a large total temperature drop, thereby fully recovering heat. However, when the heat source temperature is already low, the fluid temperature has already dropped significantly after passing through the first few stages of heat exchange. When it enters subsequent heat exchangers, the temperature difference becomes smaller, resulting in insufficient heat exchange driving force and a significant reduction in the efficiency of downstream heat exchangers.

[0003] Another common approach is to split the heat transfer fluid, allowing it to flow into separate heat exchangers, each operating independently. This connection method results in lower flow resistance in each branch, and each heat exchanger can be operated and maintained independently. However, when the heat source temperature is high, the heat recovery rate is relatively insufficient because the fluid is not cooled in stages, preventing full heat recovery. Summary of the Invention

[0004] The purpose of this invention is to provide a waste heat utilization device that can adaptively adjust the system according to the heat source temperature, thereby improving the heat source utilization effect.

[0005] This invention is achieved through the following technical solution: A waste heat recovery device, comprising: First heat exchanger, second heat exchanger, collection device and switching device; The first heat exchanger and the second heat exchanger are connected in parallel and then connected to a heat source. The switching device is used to switch the connection mode of the first heat exchanger and the second heat exchanger, so that the first heat exchanger and the second heat exchanger are connected in series and then connected to the heat source. In parallel mode, the heat source air enters the first heat exchanger and the second heat exchanger respectively and is collected in the collection device, while the fresh air enters the first heat exchanger and the second heat exchanger respectively and is connected to the heat source. In series mode, the hot source air is cooled by the second heat exchanger and the first heat exchanger and then collected in the collection device, which is used to collect the cooled flue gas. When the temperature of the heat source air is ≥140℃, the first heat exchanger and the second heat exchanger are connected in series. When the temperature of the heat source air is <100℃, the first heat exchanger and the second heat exchanger are connected in parallel. When the temperature of the heat source air is between 100℃ and 140℃, the first heat exchanger and the second heat exchanger operate in a mixed state of series or parallel connection.

[0006] Optionally, it also includes a first pipe, a second pipe, a third pipe, a fourth pipe, and a fifth pipe. The first pipe is used to connect to the fresh air equipment. The middle part of the second pipe is connected to the first pipe and then connected to the fresh air inlet of the first heat exchanger and the second heat exchanger, respectively. The third pipe is connected to the fresh air outlet of the first heat exchanger and the second heat exchanger. The two ends of the fourth pipe are connected to the third pipe, respectively. The fifth pipe is used to connect to the middle part of the fourth pipe and then to the heat source. It also includes a sixth pipe and a seventh pipe. The sixth pipe and the seventh pipe are connected to the heat source and the heat source inlet of the first heat exchanger and the second heat exchanger, respectively. The collecting device is used to connect to the heat source outlet of the first heat exchanger and the second heat exchanger.

[0007] Optionally, the collection device includes a three-way pipe and a collection tank. Two ports of the three-way pipe are respectively connected to the heat source outlet of the first heat exchanger and the second heat exchanger, and the other port of the three-way pipe is connected to the collection tank. The heat source air enters the first heat exchanger and the second heat exchanger through the sixth pipe and the seventh pipe respectively for heat exchange, and then enters the collection tank through the three-way pipe.

[0008] Optionally, the switching device includes a first solenoid valve, an eighth pipeline, a second solenoid valve, a third solenoid valve, a fourth solenoid valve, a ninth pipeline, a fifth solenoid valve, and a sixth solenoid valve. The eighth pipeline is used to connect the fresh air end of the second heat exchanger and the heat source, and the ninth pipeline is used to collect the air at the heat source outlet of the second heat exchanger. The first solenoid valve is located between the second pipeline and the second heat exchanger, the second solenoid valve is located on the eighth pipeline, the third solenoid valve is located on the seventh pipeline, the fourth solenoid valve is located between the tee pipe and the collection tank, the fifth solenoid valve is located on the ninth pipeline, and the sixth solenoid valve is located on the fifth pipeline. In series mode, the first, third, fourth, fifth and sixth solenoid valves are all closed, and the second solenoid valve is open. Fresh air enters the heat source after passing through the first pipe, the upper part of the second pipe, the first heat exchanger, the third pipe, the fourth pipe, the ninth pipe, the second heat exchanger, and the eighth pipe. The hot air enters the collection tank after passing through the sixth pipe, the first heat exchanger, the tee pipe, the second heat exchanger, the fifth pipe, and the tee pipe. In parallel mode, the second and fifth solenoid valves are closed, while the first, third, fourth, and sixth solenoid valves are open. Fresh air passes through the first pipe, the second pipe, the first heat exchanger, the second heat exchanger, the third pipe, the fourth pipe, and the fifth pipe before being connected to the heat source; The hot air enters the collection tank after passing through the sixth pipe, the first heat exchanger, the tee pipe, the seventh pipe, the second heat exchanger, and the tee pipe.

[0009] Optionally, in mixed mode: The first and second heat exchangers switch back and forth between series and parallel modes.

[0010] Optionally, the ports of the fifth and eighth pipelines connected to the heat source are equipped with gas distribution plates.

[0011] Optionally, the switching device further includes a temperature detection element and a controller. The temperature detection element is disposed inside the heat source, and the controller is disposed outside the heat source. The controller is communicatively connected to the temperature detection element and the first solenoid valve, the second solenoid valve, the third solenoid valve, the fourth solenoid valve, the fifth solenoid valve, and the sixth solenoid valve, respectively. The controller is configured as follows: When the temperature of the heat source air is ≥140℃, the switching device is controlled to switch the first heat exchanger and the second heat exchanger to series mode; When the temperature of the heat source air is <100℃, the switching device is controlled to switch the first heat exchanger and the second heat exchanger to parallel mode; When the temperature of the heat source air is between 100℃ and 140℃, the switching device is controlled to make the first heat exchanger and the second heat exchanger work in a mixed operating state.

[0012] Optionally, both the first heat exchanger and the second heat exchanger are tubular heat exchangers.

[0013] Optionally, the collection device further includes a negative pressure generator, which is disposed between the three-way pipe and the collection tank to generate negative pressure in the three-way pipe and the ninth pipeline, thereby causing the heat source air to flow along the pipeline.

[0014] Optionally, the heat source is at least one of hot stamping machine drying room, industrial kiln, boiler, gas turbine or drying equipment.

[0015] The technical solution of the present invention has at least the following advantages and beneficial effects: The switching device enables flexible switching between series and parallel operation of the first and second heat exchangers, automatically adapting the optimal connection method based on the heat source temperature. In high-temperature conditions, the series mode cools the heat source air step-by-step, ensuring thorough heat recovery and a large overall temperature drop, avoiding the insufficient heat recovery rate in parallel mode at high temperatures. In low-temperature conditions, the parallel mode splits the heat source air into two separate heat exchangers, maintaining a high temperature difference and driving force in each exchanger, thus avoiding the significant efficiency reduction caused by the smaller temperature difference in the downstream heat exchangers in series mode. This adaptive adjustment capability ensures high heat recovery efficiency across the entire temperature range.

[0016] During the switching between the series and parallel operation of the first and second heat exchangers, driven by fresh or hot air, residual gases, condensate, or accumulated impurities inside the pipes are forcibly expelled, preventing a decrease in heat exchange efficiency or pipe corrosion caused by residues. Furthermore, in the hybrid operation mode, the repeated switching between series and parallel connections ensures that both the fresh air and heat source pipes undergo periodic and repetitive purging and flushing, further improving the cleanliness of the piping system, reducing the frequency of manual maintenance, and extending the service life of the pipes and heat exchangers. Attached Figure Description

[0017] Figure 1 This is a plan view of a waste heat utilization device according to the present invention.

[0018] Figure label: 1. First heat exchanger; 2. Second heat exchanger; 3. Collection device; 31. T-pipe; 32. Collection tank; 33. Negative pressure generator; 4. Switching device; 41. First solenoid valve; 42. Eighth pipeline; 43. Second solenoid valve; 44. Third solenoid valve; 45. Fourth solenoid valve; 46. Ninth pipeline; 47. Fifth solenoid valve; 48. Sixth solenoid valve; 5. Heat source; 6. Fresh air equipment; 7. First pipeline; 8. Second pipeline; 9. Third pipeline; 10. Fourth pipeline; 11. Fifth pipeline; 12. Sixth pipeline; 13. Seventh pipeline; 14. Gas distribution plate. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0021] The following is for reference Figure 1 As shown in the illustration, and further illustrated with specific embodiments, this embodiment provides a waste heat utilization device, including: First heat exchanger 1, second heat exchanger 2, collection device 3 and switching device 4; The first heat exchanger 1 and the second heat exchanger 2 are connected in parallel and then connected to the heat source 5; The switching device 4 is used to switch the connection mode of the first heat exchanger 1 and the second heat exchanger 2, so that the first heat exchanger 1 and the second heat exchanger 2 are connected in series and then connected to the heat source 5. In parallel mode, the air from heat source 5 enters the first heat exchanger 1 and the second heat exchanger 2 respectively and is collected in the collection device 3, while fresh air enters the first heat exchanger 1 and the second heat exchanger 2 respectively and is connected to heat source 5. In series mode, the air from heat source 5 is cooled by the second heat exchanger 2 and the first heat exchanger 1 and then collected in the collection device 3. The collection device 3 is used to collect the cooled flue gas. When the air temperature of heat source 5 is ≥140℃, the first heat exchanger 1 and the second heat exchanger 2 are connected in series. When the air temperature of heat source 5 is <100℃, the first heat exchanger 1 and the second heat exchanger 2 are connected in parallel. When the air temperature of the heat source 5 is between 100℃ and 140℃, the first heat exchanger 1 and the second heat exchanger 2 are in a mixed working state of being connected in series or in parallel.

[0022] After the waste heat recovery equipment is started, the temperature detection element monitors the temperature of the air in heat source 5 in real time. When the air temperature in heat source 5 is ≥140℃, the switching device 4 switches the first heat exchanger 1 and the second heat exchanger 2 to series mode. The air in heat source 5 is cooled in two stages by passing through the second heat exchanger 2 and the first heat exchanger 1 in sequence. Fresh air is preheated in two stages by passing through the first heat exchanger 1 and the second heat exchanger 2 in sequence before being sent to heat source 5. When the air temperature in heat source 5 is <100℃, the switching device 4 switches the first heat exchanger 1 and the second heat exchanger 2 to parallel mode. The air in heat source 5 is split and enters the first heat exchanger 1 and the second heat exchanger 2 for heat exchange. Fresh air is split and enters the first heat exchanger 1 and the second heat exchanger 2 for preheating before being combined and sent to heat source 5. When the air temperature in heat source 5 is between 100℃ and 140℃, the switching device 4 keeps the first heat exchanger 1 and the second heat exchanger 2 in a mixed working state of switching between series mode and parallel mode.

[0023] In series mode, fresh air passes through two heat exchangers sequentially for two-stage heating. The heat from the high-temperature section of the exhaust gas is first recovered by the first heat exchanger 1, heating the fresh air from ambient temperature to 60-80°C. Then, the exhaust gas enters the second heat exchanger 2, further heating the fresh air to 100-120°C. This relay heating method allows the fresh air to achieve a greater total temperature rise. Furthermore, in the series arrangement, the fluid flows through multiple channels sequentially, resulting in a long flow path, stable and increased flow velocity, and high turbulence intensity, which enhances heat exchange between the fluid and the wall. Additionally, the long flow path and high velocity in series mode enable a greater total temperature rise, making it suitable for applications requiring significant temperature increases for fresh air.

[0024] In parallel mode, the parallel arrangement allows fluid to flow into multiple parallel channels, resulting in shorter flow paths, larger flow cross-sectional areas, lower flow velocities, and significantly reduced pressure loss. This leads to lower fan energy consumption and more economical system operation. The total processing capacity in parallel mode is the sum of the processing capacities of each heat exchanger, and can be flexibly expanded according to demand. Parallel mode is more advantageous for large-volume exhaust gas treatment scenarios. In parallel mode, each heat exchanger can operate independently; if one heat exchanger fails or requires maintenance, the others can continue to operate, resulting in higher system reliability. The large flow cross-sectional area and low flow velocity in parallel mode are suitable for applications requiring gentle heating of large volumes of fresh air.

[0025] In this embodiment, the system further includes a first pipe 7, a second pipe 8, a third pipe 9, a fourth pipe 10, and a fifth pipe 11. The first pipe 7 is used to connect to the fresh air device 6. The middle part of the second pipe 8 is connected to the first pipe 7 and then connected to the fresh air inlet of the first heat exchanger 1 and the second heat exchanger 2 respectively. The third pipe 9 is connected to the fresh air outlet of the first heat exchanger 1 and the second heat exchanger 2. The two ends of the fourth pipe 10 are connected to the third pipe 9 respectively. The fifth pipe 11 is used to connect to the middle part of the fourth pipe 10 and then to the heat source 5. The system also includes a sixth pipe 12 and a seventh pipe 13. The sixth pipe 12 and the seventh pipe 13 are connected to the heat source 5 and the heat source 5 inlet of the first heat exchanger 1 and the second heat exchanger 2 respectively. The collecting device 3 is used to connect to the heat source 5 outlet of the first heat exchanger 1 and the second heat exchanger 2.

[0026] On the fresh air side, the first pipe 7 connects to the fresh air equipment 6 to introduce outdoor fresh air. After being split by the second pipe 8, the fresh air enters the fresh air inlet of the first heat exchanger 1 and the second heat exchanger 2 respectively. After being heated by heat exchange, it exits from the third pipe 9, enters the fifth pipe 11 through the fourth pipe 10, and is then sent to the heat source 5. On the heat source 5 side, the air from the heat source 5 enters the heat source 5 inlet of the first heat exchanger 1 and the second heat exchanger 2 through the sixth pipe 12 and the seventh pipe 13 respectively. After being cooled by heat exchange, it is connected to the collection device 3.

[0027] Through the systematic arrangement of the first to seventh pipelines 13, independent and non-interfering fluid channels are constructed on the fresh air side and the heat source 5 side, enabling the first heat exchanger 1 and the second heat exchanger 2 to switch between parallel or series connections on both the fresh air side and the heat source 5 side. The pipeline layout is clear and compact, providing a standardized fluid interface for the connection of the switching device 4, facilitating the installation of the solenoid valve and the standardized production of the pipelines.

[0028] In this embodiment, the collection device 3 includes a three-way pipe 31 and a collection tank 32. Two ports of the three-way pipe 31 are connected to the air outlets of the heat source 5 of the first heat exchanger 1 and the second heat exchanger 2, respectively. The other port of the three-way pipe 31 is connected to the collection tank 32. The air from the heat source 5 enters the first heat exchanger 1 and the second heat exchanger 2 through the sixth pipe 12 and the seventh pipe 13 for heat exchange and cooling. Then, the air from the heat source 5 enters the collection tank 32 through the three-way pipe 31. After the two streams of air from the heat source 5 enter the first heat exchanger 1 and the second heat exchanger 2 through the sixth pipe 12 and the seventh pipe 13 for heat exchange and cooling, the two streams of air from the heat source 5 converge in the three-way pipe 31 and are collected in the collection tank 32.

[0029] The three-way pipe 31 connects the air outlets of the two heat sources 5 to the collection tank 32, resulting in a simple pipe structure and small footprint. In parallel mode, the three-way pipe 31 serves as the confluence of the air from the two heat sources 5; in series mode, the three-way pipe 31, in conjunction with the on / off state of the solenoid valve, enables the series switching of the air from the first heat exchanger 1 to the second heat exchanger 2. The versatility of the three-way pipe 31 makes it a key hub connecting the two heat exchangers and the collection device 3, reducing pipe complexity and manufacturing costs.

[0030] In this embodiment, the switching device 4 includes a first solenoid valve 41, an eighth pipeline 42, a second solenoid valve 43, a third solenoid valve 44, a fourth solenoid valve 45, a ninth pipeline 46, a fifth solenoid valve 47, and a sixth solenoid valve 48. The eighth pipe 42 is used to connect the fresh air end of the second heat exchanger 2 and the heat source 5, and the ninth pipe 46 is used to collect the air at the outlet of the heat source 5 of the second heat exchanger 2 in the collection tank 32. The first solenoid valve 41 is located between the second pipeline 8 and the second heat exchanger 2; the second solenoid valve 43 is located on the eighth pipeline 42; the third solenoid valve 44 is located on the seventh pipeline 13; the fourth solenoid valve 45 is located between the three-way pipe 31 and the collection tank 32; the fifth solenoid valve 47 is located on the ninth pipeline 46; and the sixth solenoid valve 48 is located on the fifth pipeline 11. In series mode, the first solenoid valve 41, the third solenoid valve 44, the fourth solenoid valve 45, the fifth solenoid valve 47 and the sixth solenoid valve 48 are all in the closed state, and the second solenoid valve 43 is in the open state. Fresh air enters heat source 5 after passing through the first pipe 7, the upper part of the second pipe 8, the first heat exchanger 1, the third pipe 9, the fourth pipe 10, the ninth pipe 46, the second heat exchanger 2, and the eighth pipe 42. The air from heat source 5 enters the collection tank 32 after passing through the sixth pipe 12, the first heat exchanger 1, the three-way pipe 31, the second heat exchanger 2, the fifth pipe 11, and the three-way pipe 31. In parallel mode, the second solenoid valve 43 and the fifth solenoid valve 47 are closed, while the first solenoid valve 41, the third solenoid valve 44, the fourth solenoid valve 45 and the sixth solenoid valve 48 are open. Fresh air passes through the first pipe 7, the second pipe 8, the first heat exchanger 1, the second heat exchanger 2, the third pipe 9, the fourth pipe 10, and the fifth pipe 11 before being connected to the heat source 5; The air from heat source 5 enters the collection tank 32 after passing through the sixth pipe 12, the first heat exchanger 1, the three-way pipe 31, the seventh pipe 13, the second heat exchanger 2, and the three-way pipe 31.

[0031] By controlling the solenoid valves through a combination of on / off states, one-button switching between series and parallel modes is achieved. The solenoid valves offer fast response and high control precision, completing the mode switch within seconds. The on / off state combinations of the solenoid valves are clear and unambiguous, and the control logic is simple and reliable, reducing the complexity and failure rate of the control system. In both modes, the flow paths of the fresh air and the heat source air do not interfere with each other, ensuring the stability and reliability of the heat exchange process.

[0032] In this embodiment, under mixed mode, the first heat exchanger 1 and the second heat exchanger 2 alternately switch between series and parallel modes. When the air temperature of the heat source 5 is in the transition temperature range between 100℃ and 140℃, the controller controls the switching device 4 to switch the first heat exchanger 1 and the second heat exchanger 2 between series and parallel modes at set time intervals. For example, the controller can control the equipment to operate in series mode for a certain period of time and then switch to parallel mode for the same or different periods of time, thus repeating the cycle.

[0033] Within the transition temperature range of 100℃-140℃, neither simple series nor simple parallel connection is optimal. In series mode, the downstream heat exchanger temperature difference is insufficient, while in parallel mode, the heat recovery rate is low at high temperatures. The hybrid mode, through repeated switching between series and parallel connections, allows the first heat exchanger 1 and the second heat exchanger 2 to operate in series and parallel modes respectively at different time periods. This is equivalent to achieving a weighted average of the two modes in the time dimension, enabling a smooth transition of the system's heat recovery performance within the transition temperature range and avoiding abrupt performance changes during mode switching.

[0034] In this embodiment, gas distribution plates 14 are installed at the ports where the fifth pipe 11 and the eighth pipe 42 connect to the heat source 5. When fresh air is delivered into the heat source 5 through the fifth pipe 11 or the eighth pipe 42, the airflow is evenly dispersed after passing through the flow equalization holes of the gas distribution plate 14, entering the heat source 5 with a relatively uniform speed and direction. This avoids localized overcooling or overheating caused by concentrated airflow, ensuring the uniformity of the temperature field inside the heat source 5, which is beneficial to the stable operation of the heat source 5 and the consistency of product quality. The gas distribution plate 14 also reduces airflow turbulence and noise, improving the operating environment of the equipment.

[0035] In this embodiment of the application, the switching device 4 further includes a temperature detection element and a controller. The temperature detection element is a temperature sensor and is disposed inside the heat source 5. The controller is disposed outside the heat source 5 and is communicatively connected to the temperature detection element and the first solenoid valve 41, the second solenoid valve 43, the third solenoid valve 44, the fourth solenoid valve 45, the fifth solenoid valve 47 and the sixth solenoid valve 48, respectively. The controller is configured as follows: When the air temperature of heat source 5 is ≥140℃, the control switching device 4 switches the first heat exchanger 1 and the second heat exchanger 2 to series mode. When the air temperature of heat source 5 is <100℃, the control switching device 4 switches the first heat exchanger 1 and the second heat exchanger 2 to parallel mode. When the air temperature of the heat source 5 is between 100℃ and 140℃, the control switching device 4 puts the first heat exchanger 1 and the second heat exchanger 2 into a mixed working state.

[0036] The closed-loop control of the temperature sensing element and the controller enables full automation of the waste heat recovery equipment's operating mode. It can automatically select the optimal heat exchanger connection method based on the temperature changes of heat source 5 without manual intervention. The preset temperature range thresholds (100℃ and 140℃) in the controller have been optimized and matched to cover the main temperature range of industrial waste heat recovery, enabling the equipment to operate in the optimal mode under low temperature, medium temperature, and high temperature heat source 5 conditions.

[0037] In this embodiment, both the first heat exchanger 1 and the second heat exchanger 2 are tubular heat exchangers. Tubular heat exchangers have advantages such as simple structure, strong pressure resistance, good high-temperature resistance, and ease of cleaning and maintenance, making them suitable for high-temperature, dusty flue gas conditions in industrial waste heat recovery. The tube bundles of the tubular heat exchanger can be configured with fins as needed to increase the heat exchange area and improve heat exchange efficiency. Using the same model of tubular heat exchanger for both heat exchangers facilitates unified management and maintenance of spare parts, reducing operating costs. Furthermore, the tubular heat exchanger has a simple structure; when switching between series and parallel modes, the newly entering heat source air 5 and fresh air can purge the air stagnating inside the heat exchanger, reducing the possibility of blockage.

[0038] In this embodiment, the collection device 3 further includes a negative pressure generator 33, which is disposed between the three-way pipe 31 and the collection tank 32. The negative pressure generator 33 creates negative pressure within the three-way pipe 31 and the ninth pipe 46, causing the air from the heat source 5 to flow along the pipes. The negative pressure generator 33 provides active driving force for the flow of the air from the heat source 5 in the pipes, overcoming pipe resistance and heat exchanger resistance, ensuring smooth flow of the air from the heat source 5 in both series and parallel modes. Compared to the positive pressure pushing method, the negative pressure suction method is more suitable for handling high-temperature dusty gases, avoiding scaling and corrosion problems of the high-temperature fan impeller, and improving the reliability of system operation.

[0039] In this embodiment, heat source 5 is at least one of a hot stamping machine drying room, an industrial kiln, a boiler, a gas turbine, or a drying device. Waste heat recovery equipment is connected to heat source 5, which is at least one of a hot stamping machine drying room, an industrial kiln, a boiler, a gas turbine, or a drying device. Based on the exhaust temperature characteristics of the selected heat source 5, the equipment automatically adapts to series, parallel, or mixed operating modes, recovering waste heat from the exhaust of heat source 5 to preheat the fresh air entering heat source 5. It is applicable to various industrial heat source 5 devices, covering a wide temperature range from low temperature (<100℃) to high temperature (≥140℃), exhibiting good versatility and market adaptability. Different heat source 5 devices have different exhaust temperature fluctuation characteristics; the adaptive switching function of this invention allows the equipment to flexibly adjust its operating mode according to the actual temperature of each heat source 5, achieving efficient waste heat recovery and utilization under various heat source 5 conditions.

[0040] The implementation principle of a waste heat utilization device according to an embodiment of the present invention is as follows: After the waste heat recovery equipment is started, the temperature detection element monitors the temperature of the air in heat source 5 in real time. When the air temperature in heat source 5 is ≥140℃, the switching device 4 switches the first heat exchanger 1 and the second heat exchanger 2 to series mode. The air in heat source 5 is cooled in two stages by passing through the second heat exchanger 2 and the first heat exchanger 1 in sequence. Fresh air is preheated in two stages by passing through the first heat exchanger 1 and the second heat exchanger 2 in sequence before being sent to heat source 5. When the air temperature in heat source 5 is <100℃, the switching device 4 switches the first heat exchanger 1 and the second heat exchanger 2 to parallel mode. The air in heat source 5 is split and enters the first heat exchanger 1 and the second heat exchanger 2 for heat exchange. Fresh air is split and enters the first heat exchanger 1 and the second heat exchanger 2 for preheating before being combined and sent to heat source 5. When the air temperature in heat source 5 is between 100℃ and 140℃, the switching device 4 keeps the first heat exchanger 1 and the second heat exchanger 2 in a mixed working state of switching between series mode and parallel mode.

Claims

1. A waste heat recovery device, characterized in that, include: The system comprises a first heat exchanger (1), a second heat exchanger (2), a collection device (3), and a switching device (4); The first heat exchanger (1) and the second heat exchanger (2) are connected in parallel and then connected to the heat source (5); The switching device (4) is used to switch the connection mode of the first heat exchanger (1) and the second heat exchanger (2) so that the first heat exchanger (1) and the second heat exchanger (2) are connected in series and then connected to the heat source (5); In parallel mode, the heat source (5) air enters the first heat exchanger (1) and the second heat exchanger (2) respectively and is collected in the collection device (3), and the fresh air enters the first heat exchanger (1) and the second heat exchanger (2) respectively and is connected to the heat source (5); In series mode, the air from the heat source (5) is cooled by the second heat exchanger (2) and the first heat exchanger (1) and then collected in the collection device (3), which is used to collect the cooled flue gas. When the air temperature of the heat source (5) is ≥140℃, the first heat exchanger (1) and the second heat exchanger (2) are in series. When the air temperature of the heat source (5) is <100℃, the first heat exchanger (1) and the second heat exchanger (2) are connected in parallel. When the air temperature of the heat source (5) is between 100℃ and 140℃, the first heat exchanger (1) and the second heat exchanger (2) are in a mixed working state of being connected in series or in parallel.

2. The waste heat utilization equipment according to claim 1, characterized in that, In parallel mode, it also includes a first pipe (7), a second pipe (8), a third pipe (9), a fourth pipe (10), and a fifth pipe (11). The first pipe (7) is used to connect to the fresh air equipment (6). The middle part of the second pipe (8) is connected to the first pipe (7) and then connected to the fresh air inlet of the first heat exchanger (1) and the second heat exchanger (2). The third pipe (9) is connected to the fresh air outlet of the first heat exchanger (1) and the second heat exchanger (2). The fourth pipe (7) is connected to the first heat exchanger (10), the second pipe (8) is connected to the first heat exchanger (7), the third pipe (9) is connected to the second heat exchanger (2), and the fourth pipe (8) is connected to the first heat exchanger (7). 0) The two ends are respectively connected to the third pipe (9), and the fifth pipe (11) is used to connect to the middle of the fourth pipe (10) and then to the heat source (5); it also includes the sixth pipe (12) and the seventh pipe (13), the sixth pipe (12) and the seventh pipe (13) are respectively connected to the heat source (5) and the heat source (5) inlet of the first heat exchanger (1) and the second heat exchanger (2), and the collection device (3) is used to connect to the heat source (5) outlet of the first heat exchanger (1) and the second heat exchanger (2).

3. The waste heat utilization equipment according to claim 2, characterized in that, The collecting device (3) includes a three-way pipe (31) and a collecting tank (32). Two ports of the three-way pipe (31) are connected to the air outlet of the heat source (5) of the first heat exchanger (1) and the second heat exchanger (2), respectively. The other port of the three-way pipe (31) is connected to the collecting tank (32). The air from the heat source (5) enters the first heat exchanger (1) and the second heat exchanger (2) through the sixth pipe (12) and the seventh pipe (13), respectively, and then enters the collecting tank (32) through the three-way pipe (31).

4. The waste heat utilization equipment according to claim 3, characterized in that, The switching device (4) includes a first solenoid valve (41), an eighth pipeline (42), a second solenoid valve (43), a third solenoid valve (44), a fourth solenoid valve (45), a ninth pipeline (46), a fifth solenoid valve (47), and a sixth solenoid valve (48). The eighth pipe (42) is used to connect the fresh air end of the second heat exchanger (2) and the heat source (5), and the ninth pipe (46) is used to collect the air at the outlet of the heat source (5) of the second heat exchanger (2); The first solenoid valve (41) is located between the second pipeline (8) and the second heat exchanger (2), the second solenoid valve (43) is located on the eighth pipeline (42), the third solenoid valve (44) is located on the seventh pipeline (13), the fourth solenoid valve (45) is located between the three-way pipe (31) and the collection tank (32), the fifth solenoid valve (47) is located on the ninth pipeline (46), and the sixth solenoid valve (48) is located on the fifth pipeline (11). In series mode, the first solenoid valve (41), the third solenoid valve (44), the fourth solenoid valve (45), the fifth solenoid valve (47) and the sixth solenoid valve (48) are all in the closed state, and the second solenoid valve (43) is in the open state. Fresh air enters the heat source (5) after passing through the first pipeline (7), the upper part of the second pipeline (8), the first heat exchanger (1), the third pipeline (9), the fourth pipeline (10), the ninth pipeline (46), the second heat exchanger (2), and the eighth pipeline (42); The heat source (5) air enters the collection tank (32) after passing through the sixth pipe (12), the first heat exchanger (1), the three-way pipe (31), the second heat exchanger (2), the fifth pipe (11), and the three-way pipe (31); In parallel mode, the second solenoid valve (43) and the fifth solenoid valve (47) are closed, while the first solenoid valve (41), the third solenoid valve (44), the fourth solenoid valve (45), and the sixth solenoid valve (48) are open. Fresh air passes through the first pipeline (7), the second pipeline (8), the first heat exchanger (1), the second heat exchanger (2), the third pipeline (9), the fourth pipeline (10), and the fifth pipeline (11) before being connected to the heat source (5); The heat source (5) air enters the collection tank (32) after passing through the sixth pipe (12), the first heat exchanger (1), the three-way pipe (31), the seventh pipe (13), the second heat exchanger (2), and the three-way pipe (31).

5. The waste heat utilization device according to claim 4, characterized in that, In mixed mode: The first heat exchanger (1) and the second heat exchanger (2) switch back and forth between series mode and parallel mode.

6. The waste heat utilization device according to claim 4, characterized in that, The ports of the fifth pipeline (11) and the eighth pipeline (42) connected to the heat source (5) are equipped with gas distribution plates (14).

7. The waste heat utilization equipment according to claim 4, characterized in that, The switching device (4) also includes a temperature detection element and a controller. The temperature detection element is located inside the heat source (5), and the controller is located outside the heat source (5). It is communicatively connected to the temperature detection element and the first solenoid valve (41), the second solenoid valve (43), the third solenoid valve (44), the fourth solenoid valve (45), the fifth solenoid valve (47), and the sixth solenoid valve (48), respectively. The controller is configured as follows: When the air temperature of the heat source (5) is ≥140℃, the switching device (4) is controlled to switch the first heat exchanger (1) and the second heat exchanger (2) to series mode; When the air temperature of the heat source (5) is <100°C, the switching device (4) is controlled to switch the first heat exchanger (1) and the second heat exchanger (2) to parallel mode; When the air temperature of the heat source (5) is between 100°C and 140°C, the switching device (4) is controlled to make the first heat exchanger (1) and the second heat exchanger (2) work in a mixed state.

8. The waste heat utilization equipment according to claim 1, characterized in that, Both the first heat exchanger (1) and the second heat exchanger (2) are tubular heat exchangers.

9. A waste heat utilization device according to claim 3, characterized in that, The collecting device (3) also includes a negative pressure generator (33), which is located between the three-way pipe (31) and the collecting tank (32) to generate negative pressure in the three-way pipe (31) and the ninth pipe (46) so that the heat source (5) air flows along the pipe.

10. A waste heat utilization device according to claim 1, characterized in that, The heat source (5) is at least one of the following: hot stamping machine drying room, industrial kiln, boiler, gas turbine or drying equipment.

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