Phase-change material internal packaging type air cooling tube bundle and assembling and operating method of phase-change material internal packaging type air cooling tube bundle

Abstract

The invention discloses a phase-change material internal packaging type air cooling tube bundle and an assembling and operating method thereof, and belongs to the technical field of energy conservation and consumption reduction of coal-fired units. The air cooling tube bundle comprises a phase change material filling assembly and a hollow tubular base tube, wherein the phase change material filling assembly is coaxially arranged in the base tube; the phase-change material filling assembly comprises a sealing sleeve and a composite phase-change material, the sealing sleeve is filled with the composite phase-change material, a gap exists between the inner wall of the base pipe and the outer wall of the sealing sleeve, and the gap is a steam channel. The tube bundle temperature is kept stable through the heat storage and release characteristics of the phase-change material, fan energy consumption is reduced, and the service life of equipment is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of energy conservation and consumption reduction technology for coal-fired power units, specifically relating to an internally encapsulated air-cooled tube bundle of phase change material and its assembly and operation method. Background Technology

[0002] In the critical industrial cooling system of air-cooled islands, the air-cooled tube bundle, as the core component for steam condensation and heat exchange, plays a decisive role in the system's operating efficiency and stability. Currently, most air-cooled tube bundles widely used in the market adopt a single metal tube structure, which mainly relies on the thermal conductivity of the metal tube wall itself to achieve heat exchange between steam and the external environment.

[0003] However, in actual industrial operation, this type of air-cooled tube bundle with a single metal tube structure faces many severe challenges. Among them, the problem of rapid changes in the tube bundle wall temperature due to fluctuations in the steam temperature flowing into the tube bundle is particularly prominent. Taking a thermal power system as an example, the power load fluctuates due to user demand, grid dispatch, and other factors, leading to frequent fluctuations in steam parameters, especially steam temperature. When the steam temperature rises, the metal tube bundle rapidly absorbs heat from the steam, causing the tube bundle wall temperature to rise sharply in a short period of time. To maintain the condensation process of the steam inside the tube bundle and ensure the normal operation of the system, the fans equipped in the air-cooled island must immediately increase their speed to enhance airflow, accelerate heat dissipation, and prevent the tube bundle from being damaged due to excessive temperature. Conversely, when the steam temperature decreases, the tube bundle wall temperature also drops rapidly. If the fans continue to operate at a high speed at this time, it will cause over-cooling of the tube bundle. Over-cooling not only wastes a lot of electrical energy but also generates excessive temperature stress on the tube bundle surface, exacerbating the metal fatigue of the tube bundle. Furthermore, the fan speed needs to be frequently adjusted based on changes in steam temperature. Since steam temperature fluctuations are frequent and unpredictable, the fan must constantly switch between high and low speeds, resulting in consistently high fan energy consumption and significantly increasing the operating costs of the air-cooled island system. The impact of frequent temperature fluctuations on tube bundle metal fatigue should not be underestimated. In addition, the tube bundle temperature changes and fan speed adjustments caused by steam temperature fluctuations negatively affect the stability of the entire cooling process. An unstable cooling process leads to uneven steam condensation, reducing the heat exchange efficiency of the air-cooled island system and making it difficult for the system to achieve the expected cooling effect. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide an internally encapsulated air-cooled tube bundle of phase change material and its assembly and operation method. By utilizing the heat storage and release characteristics of phase change material, the tube bundle temperature is kept stable, the fan energy consumption is reduced, the equipment life is extended, and the problems of high fan energy consumption, short equipment life and poor cooling stability caused by temperature fluctuations in existing air-cooled tube bundles are solved.

[0005] To achieve the above objectives, the present invention employs the following technical solution: The present invention provides an internally encapsulated air-cooled tube bundle of phase change material, including a phase change material filling component and a hollow tubular base tube. The phase change material filling component is coaxially disposed inside the base tube. The phase change material filling component includes a sealing sleeve and a composite phase change material. The composite phase change material is filled inside the sealing sleeve. There is a gap between the inner wall of the base tube and the outer wall of the sealing sleeve, and the gap is a steam channel.

[0006] In one embodiment, the composite phase change material is a composite phase change material composed of paraffin and graphite, wherein paraffin accounts for 70-85 wt% of the composite phase change material and graphite accounts for 15-30 wt% of the composite phase change material.

[0007] In one embodiment, the sealing sleeve is a metal sleeve closed at both ends, and the sealing sleeve is disposed inside the base tube and coaxial with the base tube.

[0008] In one embodiment, the sealing sleeve is made of 304 stainless steel or copper alloy.

[0009] In one embodiment, the filling rate of the composite phase change material inside the sealing sleeve is 90-95%.

[0010] This invention also provides a method for assembling an internally encapsulated air-cooled tube bundle of phase change material, comprising the following steps: Paraffin wax is heated to a molten state, and graphite is added and stirred evenly to form a composite phase change material; wherein, paraffin wax accounts for 70-85 wt% of the phase change material by mass, and graphite accounts for 15-30 wt% of the phase change material by mass; After injecting the composite phase change material into the interior of the sealing sleeve, the two ends of the sealing sleeve are welded and sealed to form a phase change material filling assembly. The phase change material filling component is coaxially embedded inside the base tube, and a gap is left between the inner wall of the base tube and the outer wall of the sealing sleeve to form a vapor channel, thus completing the assembly of the internal encapsulated air-cooled tube bundle of the phase change material.

[0011] In one embodiment, the filling rate of the composite phase change material inside the sealing sleeve is 90-95%.

[0012] In one embodiment, the heating temperature is 10-20°C higher than the phase transition temperature of paraffin, the stirring rate is 300-500 r / min, and the stirring time is 20-30 min.

[0013] This invention also provides a method for operating an internally encapsulated air-cooled tube bundle of phase change material, comprising the following steps: When the temperature of the steam introduced into the base tube of the encapsulated air-cooled tube bundle inside the phase change material is higher than the phase change temperature of the composite phase change material, the heat of the steam in the steam channel is transferred to the composite phase change material through the sealed sleeve. The composite phase change material absorbs the heat and undergoes a solid-liquid phase change to store energy. When the temperature of the steam introduced into the base tube of the encapsulated air-cooled tube bundle inside the phase change material is lower than the phase change temperature of the composite phase change material, the energy stored in the composite phase change material is released and transferred to the steam channel through the sealed sleeve to maintain the temperature of the encapsulated air-cooled tube bundle inside the phase change material.

[0014] In one embodiment, the phase transition temperature of the composite phase change material is 50-120°C.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention provides an air-cooled tube bundle with internally encapsulated phase change material (PCM) filling components. By coaxially arranging the PCM filling components inside the base tube and leaving gaps as steam channels, it ensures smooth steam flow and increases the heat exchange area between the PCM and steam, thereby improving heat transfer efficiency. Specifically, the coaxial arrangement of the PCM filling components inside the base tube ensures maximum contact area between the PCM and steam, improving heat exchange efficiency. The heat storage and release characteristics of the PCM effectively buffer the impact of steam temperature fluctuations on the tube bundle temperature, reducing metal fatigue caused by frequent temperature fluctuations. This invention improves heat exchange efficiency, reduces fan energy consumption, and enhances the system's thermal stability and operational reliability by optimizing the structural design and material selection of the air-cooled tube bundle. These improvements collectively meet the demands of high efficiency and energy saving in industry, providing strong support for the optimized operation of air-cooled island systems.

[0016] Furthermore, a composite phase change material composed of paraffin wax and graphite is used, wherein paraffin wax accounts for 70-85 wt% and graphite accounts for 15-30 wt%. The above ratio can utilize the high energy storage density of paraffin wax and improve the thermal conductivity through graphite, effectively solving the problem of poor thermal conductivity of paraffin wax.

[0017] Furthermore, the sealing sleeve is closed at both ends and coaxially arranged inside the base tube, forming an independent heat exchange unit, which enhances the heat exchange efficiency between the phase change material and the base tube, while preventing leakage of the phase change material.

[0018] Furthermore, 304 stainless steel or copper alloy is selected as the material for the sealing sleeve. These two materials have good thermal conductivity and sealing properties, ensuring efficient heat exchange and extending the service life of the equipment.

[0019] Furthermore, the composite phase change material has a filling rate of 90-95%, which reserves space for phase change expansion, preventing equipment damage caused by volume changes during the phase change process, while ensuring sufficient energy storage capacity.

[0020] This invention also provides an assembly method for an internally encapsulated air-cooled tube bundle of phase change material. The method involves heating paraffin to a molten state, adding graphite and stirring evenly to form a composite phase change material, then injecting it into a sealing sleeve and welding it for sealing. Finally, the phase change material filling component is coaxially embedded inside the base tube. This assembly method ensures efficient filling and sealing of the phase change material, improving production efficiency and product quality.

[0021] This invention provides an operating method for an internally encapsulated air-cooled tube bundle made of phase change material (PCM). When the steam temperature is higher than the PCM temperature, the PCM absorbs heat and undergoes a solid-liquid phase change to store energy. This process effectively slows down the rate of temperature rise of the tube bundle wall, preventing the fan from increasing its speed due to a sudden rise in tube bundle temperature, thereby reducing fan energy consumption. When the steam temperature is lower than the PCM temperature, the PCM releases energy to maintain a stable tube bundle temperature. This process effectively prevents a sharp drop in tube bundle wall temperature, preventing the fan from reducing its speed due to a sudden drop in tube bundle temperature, thereby improving the stability of the cooling process. This method effectively buffers the impact of steam temperature fluctuations on the tube bundle temperature, improving the system's thermal stability and operating efficiency. Specifically, the tube bundle has a coaxial sleeve structure. The sleeve contains a phase change material, while steam flows externally. When the steam temperature entering the base tube is high (above the phase change temperature of the phase change material), the steam heat is transferred to the composite phase change material through the base tube wall and the sealing sleeve. The paraffin absorbs the heat and undergoes a solid-liquid phase change, storing the energy in the phase change material. When the steam temperature decreases (below the phase change temperature of the phase change material), the paraffin in the phase change material releases the stored energy, which is transferred to the steam side through the base tube wall, slowing down the rate of temperature drop in the base tube wall and maintaining the overall temperature of the tube bundle within a stable range (fluctuation range controlled within ±5℃). During this process, the fan does not need to frequently adjust its speed due to small fluctuations in steam temperature; it only needs to maintain operation within a relatively stable speed range, effectively improving the thermal stability of the air-cooled tube bundle and reducing fan energy consumption. This invention is applicable to air-cooled systems in industries such as thermal power generation and chemical processing where steam flow rates are high and internal thermal buffering needs to be strengthened. It aims to solve the problems of large temperature fluctuations in the tube bundle and high fan energy consumption under high flow rate conditions. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the internally encapsulated air-cooled tube bundle of a phase change material provided by the present invention. Wherein: 1-Air-cooled tube bundle assembly; 2-Base tube; 3-Composite phase change material; 4-Sealing sleeve. Detailed Implementation

[0023] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0024] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0025] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0026] To address the following problems in existing technologies: When steam is introduced into an air-cooled tube bundle with a single metal tube structure and the temperature fluctuates, the tube bundle wall temperature changes rapidly. Specifically, when the steam temperature rises, the tube bundle temperature rises sharply, requiring the fan to increase its speed to enhance heat dissipation; conversely, when the steam temperature drops, the tube bundle temperature drops sharply, requiring the fan to reduce its speed to avoid overcooling. This frequent fan speed adjustment not only leads to high fan energy consumption but also exacerbates tube bundle metal fatigue due to frequent temperature fluctuations, shortening the overall service life of the air-cooled island equipment. It also affects the stability of the cooling process, making it difficult to meet the demands of high efficiency and energy saving in industry. This embodiment provides an air-cooled tube bundle internally encapsulated with phase change material. The following detailed description of this embodiment, in conjunction with the accompanying drawings, is as follows: Figure 1 As shown, the phase change material internal encapsulated air-cooled tube bundle includes a phase change material filling component and a hollow tubular base tube 2. The phase change material filling component is coaxially disposed inside the base tube 2. The phase change material filling component includes a sealing sleeve 4 and a composite phase change material 3 filled inside the sealing sleeve. There is a gap between the inner wall of the base tube 2 and the outer wall of the sealing sleeve 4, and the gap is a steam channel.

[0027] Appendix Figure 1 This is a schematic diagram of the internal encapsulated air-cooled tube bundle of the phase change material in this embodiment. Figure 1 Further details.

[0028] The overall structural design of the internally encapsulated air-cooled tube bundle of phase change material mainly includes a base tube 2 and a phase change material filling assembly within the air-cooled tube bundle assembly. The base tube 2 is a hollow tubular structure used to introduce the steam to be cooled and the built-in phase change material filling assembly. The phase change material filling assembly is located inside the base tube and is a coaxial sleeve structure with the base tube. There is a gap between the inner wall of the base tube 2 and the outer wall of the phase change material filling assembly, which serves as a steam passage and does not obstruct the flow of steam within the base tube. The phase change material filling assembly includes a composite phase change material 3 and a sealing sleeve 4, with the composite phase change material 3 filling the interior of the sealing sleeve 4.

[0029] Specifically, the aforementioned phase change material filling assembly includes a sealing sleeve 4 and a composite phase change material 3. The sealing sleeve 4 is a metal sleeve closed at both ends (the material of the sealing sleeve 4 is 304 stainless steel or copper alloy, which has good thermal conductivity and sealing performance), used to enhance the heat exchange between the composite phase change material 3 and the base tube 2. The composite phase change material 3, which is a composite material of paraffin wax and graphite, is filled inside the sealing sleeve 4. Paraffin wax accounts for 70-85 wt%, and graphite accounts for 15-30 wt%. The phase change temperature of paraffin wax is 50-120℃, which is suitable for the steam temperature range of the air-cooled system. Graphite is used to improve the thermal conductivity of the phase change material and avoid insufficient thermal conductivity during the phase change of paraffin wax. The filling rate of the composite phase change material 3 in the sealing sleeve 4 is 90-95%, leaving space for the phase change expansion of the composite phase change material 3.

[0030] This embodiment also provides a method for assembling an internally encapsulated air-cooled tube bundle of phase change material, including the following steps: Step 1: Prepare composite phase change material 3; Step 2, sleeve encapsulation: After injecting the composite phase change material 3 into the interior of the sealing sleeve 4, the two ends of the sealing sleeve 4 are welded and sealed to form a phase change material filling assembly; Step 3, Component assembly: The phase change material filling component is coaxially embedded inside the base tube 2. A gap is left between the inner wall of the base tube 2 and the outer wall of the sealing sleeve 4 to form a vapor channel. The internal encapsulated air-cooled tube bundle of phase change material is assembled.

[0031] The preparation process of the composite phase change material 3 in step one above is as follows: heat the paraffin to a molten state (temperature 10-20℃ higher than its phase change temperature), add graphite powder, and stir evenly (stirring speed 300-500r / min, stirring time 20-30min) to form the composite phase change material 3.

[0032] The specific process of the above step two sleeve sealing is as follows: Inject the composite phase change material 3 into the sealing sleeve 4 (filling rate 90-95%, reserve space for phase change expansion), and use laser welding or argon arc welding to seal both ends of the sleeve 4 to ensure no leakage; The specific process of assembling the components in step three above is as follows: the sealing sleeve 4 containing the encapsulated phase change material is embedded inside the base tube 2, and a gap is left between the inner wall of the base tube 2 and the outer wall of the sealing sleeve 4 to form a vapor channel, thus completing the assembly of the internal encapsulated air-cooled tube bundle of the phase change material.

[0033] This embodiment provides a method for operating a phase change material internally encapsulated air-cooled tube bundle, which includes the following steps: In one scenario, when the temperature of the steam introduced into the base pipe 2 is high (higher than the phase change temperature of the composite phase change material 3), the heat from the steam is transferred to the composite phase change material 3 through the sealed sleeve 4. The paraffin absorbs the heat and undergoes a solid-liquid phase change, storing the energy in the composite phase change material 3. In another scenario, when the steam temperature decreases (below the phase change temperature of the composite phase change material 3), the paraffin in the composite phase change material 3 releases the stored energy, which is transferred to the steam side through the sealing sleeve 4, slowing down the rate of temperature drop of the pipe wall of the base pipe 2 and maintaining the overall temperature of the tube bundle within a stable range (fluctuation range controlled within ±5℃). In both of these scenarios, the blower does not need to frequently adjust its speed due to small fluctuations in steam temperature, but only needs to maintain operation within a relatively stable speed range.

[0034] In air-cooled island systems, the application of phase change material (PCM)-encapsulated air-cooled tube bundles significantly improves the thermal stability of the air-cooled island operation. PCM, with its unique heat storage and release characteristics, plays a crucial buffering role in the air-cooled tube bundles. When the steam temperature flowing into the air-cooled tube bundles fluctuates, the PCM responds rapidly. When the steam temperature rises, the PCM absorbs excess heat transferred from the steam, gradually changing from a solid to a liquid state, storing the heat as latent heat. This effectively prevents a sudden rise in tube bundle temperature, maintaining the tube bundle temperature within a relatively stable range. Conversely, when the steam temperature decreases, the PCM releases the previously stored heat, changing from a liquid to a solid state, providing additional heat to the tube bundle and preventing a sharp drop in temperature. Through this dynamic balance of heat storage and release, the PCM effectively buffers the direct impact of steam temperature fluctuations on the tube bundle temperature, providing strong support for the stable operation of the air-cooled island system. From the perspective of fan operation, the stabilizing effect of the PCM on the tube bundle temperature greatly reduces the frequency of fan speed adjustments due to temperature fluctuations. In traditional single-tube air-cooled tube bundles, even slight changes in steam temperature can lead to corresponding changes in fan speed, increasing the fan's operating load and causing significant energy waste. However, the application of phase change material (PCM)-encapsulated air-cooled tube bundles allows the fan to operate under relatively stable conditions, eliminating the need for frequent start-ups, shutdowns, or speed adjustments, thus significantly reducing energy consumption and fully meeting the urgent energy-saving needs of current industrial sectors. Regarding equipment lifespan, frequent temperature fluctuations in the tube bundle are a major factor contributing to metal fatigue. During repeated temperature changes, metal materials generate thermal stress, which accumulates with each cycle, eventually leading to fatigue cracks and their propagation, shortening the tube bundle's lifespan. The application of PCM mitigates these frequent temperature fluctuations, reducing the thermal stress level on the metal material and effectively slowing down the occurrence and development of metal fatigue. Furthermore, the compatibility between the base tube and the PCM-encapsulated air-cooled tube bundle is fully considered during its design and manufacturing. By selecting suitable materials and employing advanced encapsulation processes, corrosion problems caused by material incompatibility are avoided, further ensuring the reliability and stability of the air-cooled tube bundle. Considering all these factors, the service life of the air-cooled island equipment can be significantly extended, by an estimated 3-5 years, greatly reducing equipment maintenance costs and replacement frequency.

[0035] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A phase change material internally encapsulated air-cooled tube bundle, characterized in that, The device includes a phase change material filling component and a hollow tubular base tube (2). The phase change material filling component is coaxially disposed inside the base tube (2). The phase change material filling component includes a sealing sleeve (4) and a composite phase change material (3) filled inside the sealing sleeve (4). There is a gap between the inner wall of the base tube (2) and the outer wall of the sealing sleeve (4), and the gap is a steam channel.

2. The phase change material internally encapsulated air-cooled tube bundle according to claim 1, characterized in that, The composite phase change material (3) is a composite phase change material composed of paraffin and graphite, with paraffin accounting for 70-85 wt% of the composite phase change material and graphite accounting for 15-30 wt% of the composite phase change material.

3. The phase change material internally encapsulated air-cooled tube bundle according to claim 1, characterized in that, The sealing sleeve (4) is a metal sleeve closed at both ends. The sealing sleeve (4) is set inside the base tube (2) and is coaxial with the base tube (2).

4. The phase change material internally encapsulated air-cooled tube bundle according to claim 1, characterized in that, The sealing sleeve (4) is made of 304 stainless steel or copper alloy.

5. The internally encapsulated air-cooled tube bundle of phase change material according to claim 1, characterized in that, The composite phase change material (3) inside the sealing sleeve (4) has a filling rate of 90-95%.

6. A method for assembling an internally encapsulated air-cooled tube bundle of a phase change material, characterized in that, Includes the following steps: Paraffin wax is heated to a molten state, and graphite is added and stirred evenly to form a composite phase change material (3); wherein, paraffin wax accounts for 70-85 wt% of the mass of the phase change material, and graphite accounts for 15-30 wt% of the mass of the phase change material; After the composite phase change material (3) is injected into the interior of the sealing sleeve (4), the two ends of the sealing sleeve (4) are welded and sealed to form a phase change material filling assembly. The phase change material filling component is coaxially embedded inside the base tube (2), and a gap is left between the inner wall of the base tube (2) and the outer wall of the sealing sleeve (4) to form a steam channel, thus completing the assembly of the internal encapsulated air-cooled tube bundle of the phase change material.

7. The assembly method of the internally encapsulated air-cooled tube bundle of phase change material according to claim 6, characterized in that, The composite phase change material (3) inside the sealing sleeve (4) has a filling rate of 90-95%.

8. The assembly method of the internally encapsulated air-cooled tube bundle of phase change material according to claim 6, characterized in that, The heating temperature is 10-20°C higher than the phase transition temperature of paraffin, the stirring rate is 300-500 r / min, and the stirring time is 20-30 min.

9. A method for operating a phase change material internally encapsulated air-cooled tube bundle, characterized in that, Includes the following steps: When the temperature of the steam introduced into the base tube (2) of the encapsulated air-cooled tube bundle inside the phase change material is higher than the phase change temperature of the composite phase change material (3), the heat of the steam in the steam channel is transferred to the composite phase change material (3) through the sealed sleeve (4), and the composite phase change material (3) absorbs heat and undergoes a solid-liquid phase change to store energy. When the temperature of the steam introduced into the base tube (2) of the encapsulated air-cooled tube bundle inside the phase change material is lower than the phase change temperature of the composite phase change material (3), the energy stored in the composite phase change material (3) is released and transferred to the steam channel through the sealed sleeve (4) to maintain the temperature of the encapsulated air-cooled tube bundle inside the phase change material.

10. The method for operating the internally encapsulated air-cooled tube bundle of phase change material according to claim 9, characterized in that, The phase transition temperature of the composite phase change material (3) is 50-120℃.

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