Load fluctuation type steam heat preservation pipeline based on phase change heat storage and method thereof

Abstract

The invention discloses a load fluctuation type steam heat preservation pipeline based on phase change heat storage and a method thereof. According to the heat preservation pipeline, a phase change heat storage heat preservation layer, a multi-layer heat preservation layer and an outer protection layer are sequentially and coaxially laid on the outer wall of a working pipe; the phase-change heat-storage heat-preservation layer is assembled on the outer wall of the working pipe through phase-change heat-preservation heat-storage units in a tongue-and-groove splicing mode, and the phase-change temperature of the phase-change material filled in each phase-change heat-preservation heat-storage unit is located between the steam saturation temperature and the working temperature under the stable working condition. By means of the thermal resistance self-adaption characteristic of the phase change material, the thermal resistance effect is dynamically enhanced in the phase change process, and a dual-heat-preservation mechanism of heat dissipation blocking and delaying between a high-temperature medium in the working pipe and the environment is achieved. And meanwhile, circulating heat storage and release of the phase change heat storage heat preservation layer are achieved through a heat source of the pipeline, and a zero-energy-consumption self-operation mode is formed. The method can be widely applied to various high-temperature steam pipe networks, is particularly suitable for industrial scenes with load fluctuation, and can reduce heat loss and improve the operation stability of the pipe networks.

Description

Technical Field

[0001] The present invention relates to the field of phase change heat storage and insulation, and particularly to a load-fluctuation type steam insulation pipeline based on phase change heat storage and its method. Background Art

[0002] The heat insulation performance of traditional insulation materials is greatly affected by external factors, and it cannot effectively block the heat dissipation between the high-temperature steam inside the thermal steam pipeline and the environment. Phase change heat storage materials have the characteristics of constant-temperature heat absorption and release, high energy storage density, and poor thermal conductivity. The adiabatic insulation structure based on phase change heat storage materials has broad application prospects in heat energy transmission systems such as high-temperature steam pipelines.

[0003] Chinese Patent 201720615264.7 proposes a heating pipeline using phase change heat storage for insulation, which uses an external heat source such as solar energy to charge the phase change heat storage insulation layer. Its application effect is seriously affected by external environmental factors, and the phase change temperature and latent heat value of the phase change material are limited, which is not suitable for high-temperature steam transmission systems. Chinese Patent 202410657762.2 proposes a composite energy storage skin tracing system. A cable is arranged inside the tracing pipeline to form a skin effect tracing pipeline, and a phase change heat storage insulation layer is laid outside. The heat dissipation loss is reduced through a cascade structure design. However, this system is mainly aimed at oil transportation pipelines, and its applicability to high-temperature steam pipelines needs to be further verified. Moreover, it relies on an external solar power supply system for energy supply, the system structure is complex, and the installation and maintenance costs are relatively high. Chinese Patent 202310144659.3 proposes a phase change microcapsule-based thermal insulation system for power plant pipelines. The insulation layer includes a phase change thermal insulation matrix and phase change microcapsules, and the charging and discharging processes of the phase change heat storage material are realized by adjusting the distance between the insulation sleeve and the pipeline. However, the control system and structural composition in this solution are complex, additional energy consumption is required, and the preparation of phase change microcapsules is cumbersome, which limits its application in long-distance pipelines.

[0004] Therefore, for high-temperature steam pipelines, it is of great practical significance to further research and develop a phase change heat storage insulation structure with good heat insulation performance, not relying on external energy, simple structure, and low cost. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above problems and provide a load-fluctuation type steam insulation pipeline based on phase change heat storage and its working method. The phase change material is used to block the heat dissipation between the high-temperature steam and the environment, improve the heat insulation effect, and realize the charging and discharging of the phase change material through the self-power supply of the steam pipeline, without relying on external energy.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a load fluctuation type steam heat preservation pipeline based on phase change heat storage, which includes a working pipe, a phase change heat storage insulation layer, a multi-layer insulation layer, and an outer protective layer; the inside of the working pipe is used for conveying a working fluid, and the outer wall of the working pipe is coaxially provided with a phase change heat storage insulation layer, a multi-layer insulation layer, and an outer protective layer in sequence; the phase change heat storage insulation layer is assembled by a series of phase change heat preservation and heat storage units in a tongue-and-groove splicing manner, and is circumferentially attached around the outer wall of the working pipe. The phase change temperature of the phase change material filled in each phase change heat preservation and heat storage unit is between the steam saturation temperature and the working temperature under stable working conditions.

[0008] As a preference of the above first aspect, the phase change heat preservation and heat storage unit includes a sealed protective shell, a phase change material, a support body, and a connection structure. The phase change material is filled in the sealed inner cavity of the sealed protective shell. The support body, as a structural reinforcement member, is radially supported in the sealed inner cavity of the sealed protective shell along the pipeline. A connection structure for tongue-and-groove splicing with other sealed protective shells is provided at the splicing position on the outer side wall of the sealed protective shell.

[0009] As a preference of the above first aspect, the phase change heat storage insulation layer adopts an assembled structure formed by splicing phase change heat preservation and heat storage units along the axis and circumferentially. Each single phase change heat preservation and heat storage unit is in a fan-shaped ring shape. The extending direction of the connection structure on the phase change heat preservation and heat storage unit is along the pipeline axis. The outside of each section of the working pipe is formed into a complete annular pipeline-shaped phase change heat storage insulation layer by splicing multiple phase change heat preservation and heat storage units around the circumference.

[0010] As a preference of the above first aspect, the phase change heat storage insulation layer adopts an assembled structure formed by spiral winding and splicing of phase change heat preservation and heat storage units. Each single phase change heat preservation and heat storage unit is in a spiral shape wound around the outer wall of the working pipe. The connection structure on the phase change heat preservation and heat storage unit is also spirally arranged. The outside of each section of the working pipe is formed into a complete annular pipeline-shaped phase change heat storage insulation layer by splicing two phase change heat preservation and heat storage units.

[0011] As a preference of the above first aspect, the filling rate of the phase change material in the sealed inner cavity of the sealed protective shell is higher than 95%.

[0012] As a preference of the above first aspect, the phase change temperature range of the phase change material is [T1 + ΔT, T2 - ΔT], where T1 is the steam saturation temperature in the steam heat preservation pipeline under stable working conditions, T2 is the working temperature of the steam heat preservation pipeline under stable working conditions, and ΔT = 5 - 10°C.

[0013] As a preference of the above first aspect, the solid-liquid phase change latent heat of the phase change material is higher than 100 MJ / kg. The types of the phase change material include but are not limited to molten salt materials, sugar alcohol materials, and their mixtures.

[0014] Preferably, in the first aspect described above, the thermal conductivity of the phase change material is lower than 1.0 W / (m·K).

[0015] Preferably, in the first aspect described above, the multi-layer thermal insulation layer adopts a combination of at least two of a vacuum insulation layer, a thermal insulation material filling layer, and a multi-layer reflective layer; the thermal insulation materials in the thermal insulation material filling layer include one or more combinations of glass fiber, aerogel, rock wool, hard calcium silicate, foamed glass, rare earth thermal insulation materials, foamed calcium silicate, and polyurethane.

[0016] In a second aspect, the present invention provides a method for improving the thermal insulation performance of a load-fluctuating steam insulation pipeline based on phase change heat storage according to any one of the first aspects described above. The specific method is as follows:

[0017] First, the load-fluctuating steam insulation pipeline is used as the steam transmission pipeline of the heat network in a new construction or renovation manner. Among the load-fluctuating steam insulation pipelines in different sections of the heat network, the phase change material in the phase change heat storage insulation layer needs to be selected according to the steam temperature and pressure characteristics of the section where it is located, so that the phase change temperature of the phase change material is between the steam saturation temperature and the working temperature under stable conditions in the section where it is located;

[0018] Secondly, during the operation of the heat network, according to the operating conditions inside the pipeline, the cyclic heat storage and heat release capacity of the phase change material inside the phase change heat storage insulation layer is adaptively used to reduce the heat loss of the pipeline. Among them:

[0019] When the temperature of the steam in the working pipe of the heat network is higher than the temperature of the phase change material, at this time, the phase change heat storage insulation layer is heated by the slow heat release of the steam, so that the phase change material gradually melts and does not cause condensation of the steam in the heat network, thereby storing part of the heat through the phase change material in the phase change heat storage insulation layer while ensuring the safety and stability of the heat network;

[0020] When the temperature of the steam in the working pipe of the heat network is lower than the temperature of the phase change material, the phase change material in the phase change heat storage insulation layer maintains the temperature of the phase change heat storage insulation layer constant through the constant-temperature solidification heat release process, thereby ensuring that the temperature difference between the steam in the working pipe and the phase change heat storage insulation layer remains unchanged and is higher than the phase change temperature of the phase change material, thereby avoiding the phenomenon of rapid temperature drop and condensation loss caused by direct heat dissipation of the steam to the outside and reducing the heat loss of the pipeline.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) Through the thermal resistance self-adaptive characteristic of the phase change material, the present invention dynamically enhances the thermal resistance effect during the phase change process, realizing a dual thermal insulation mechanism of heat dissipation blocking and delay between the high-temperature medium in the working pipe and the environment.

[0023] (2) The present invention utilizes the heat source of the pipeline itself to achieve the cyclic heat storage and heat release of the phase change heat storage insulation layer, forming a zero - energy self - operating mode without additional energy consumption.

[0024] (3) The present invention combines economy and convenience, is easy to disassemble, repair and replace; has a wide applicability and can be used in various high - temperature steam pipe networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a cross - section of a load - fluctuating steam insulation pipeline based on phase change heat storage;

[0026] Figure 2 is the phase change heat storage insulation layer of the splicing structure of the phase change insulation heat storage unit;

[0027] Figure 3 is the phase change heat storage insulation layer of the overall spiral winding structure;

[0028] Figure 4 is the diagram of the steam temperature inside the pipe of the load - fluctuating steam insulation pipeline based on phase change heat storage under the periodic heating condition;

[0029] In the figure: working fluid 1, working pipe 2, phase change heat storage insulation layer 3, multi - layer insulation layer 4, outer protective layer 5, phase change heat storage unit 6, sealed protective shell 7, phase change material 8, support body 9, connection structure 10. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] In order to make the above - mentioned objects, features and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given in conjunction with the accompanying drawings. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0031] As Figure 1 shown, the present invention provides a load - fluctuating steam insulation pipeline based on phase change heat storage, including a working pipe 2, a phase change heat storage insulation layer 3, a multi - layer insulation layer 4 and an outer protective layer 5; the inside of the working pipe 2 is used for transporting the working fluid 1, and the outer wall of the working pipe 2 is coaxially provided with a phase change heat storage insulation layer 3, a multi - layer insulation layer 4 and an outer protective layer 5 in sequence. The above - mentioned phase change heat storage insulation layer 3 is assembled by a series of phase change insulation heat storage units 6 in a rabbet - splicing manner to form a laminated structure that fits around the outer wall of the working pipe 2, and the phase change temperature of the phase change material 8 filled in each phase change insulation heat storage unit 6 is between the steam saturation temperature and the working temperature under stable conditions.

[0032] The working pipe 2 in the present invention is a pipe for transporting the working fluid 1. In the embodiment of the present invention, the working fluid 1 transported inside the working pipe 2 is high-temperature steam. It should be noted that the working pipe 2 can be a new pipe or an existing pipe in the heat network. That is to say, the load-fluctuating steam heat-insulating pipe of the present invention can be a newly formed heat-insulating pipe by integral processing or a heat-insulating pipe formed by reforming the existing pipe, and there is no limit to this.

[0033] In addition, the phase-change heat storage heat-insulating layer 3 of the present invention is assembled by a series of phase-change heat-insulating and heat-storing units 6 in a rabbet-splicing manner, and its specific structural form can be adjusted according to the actual situation. In the present invention, two preferred assembly structures are provided, namely the axial and circumferential splicing structure and the spiral winding structure.

[0034] As Figure 2 shown, the first axial and circumferential splicing structure is shown. Among them, the phase-change heat storage heat-insulating layer 3 sleeved outside the working pipe 2 adopts an assembly structure in which the phase-change heat-insulating and heat-storing units 6 are spliced along the axis and circumferentially. Each single-phase change heat-insulating and heat-storing unit 6 is in a sector-annular shape. The structure of each phase-change heat-insulating and heat-storing unit 6 is the same, including a sealed protective shell 7 with a sector-annular cross-section as a whole, a phase-change material 8, a support 9, and a connection structure 10. The sealed protective shell 7 is made of a heat-conducting metal material and has a sealed inner cavity inside. The phase-change material 8 is filled in the sealed inner cavity of the sealed protective shell 7. Since the pipe needs to have a certain ability to bear the radial load, a plurality of supports 9 are arranged as structural strengthening members in the sealed inner cavity of the sealed protective shell 7. The supports 9 are radially supported in the sealed inner cavity along the pipe axis and are respectively fixed on the inner arc plate and the outer arc plate of the sealed protective shell 7 at both ends. The support 9 and the sealed protective shell 7 can be integrally processed or separately processed and then assembled. In addition, a connection structure 10 for rabbet splicing with other sealed protective shells 7 is provided at the splicing position of the two outer side walls of the sealed protective shell 7 along the pipe circumference. The extending direction of the connection structure 10 on the phase-change heat-insulating and heat-storing unit 6 is along the pipe axis. The outside of each section of the working pipe 2 is spliced by a plurality of phase-change heat-insulating and heat-storing units 6 around the circumference to form a complete annular pipe-shaped phase-change heat storage heat-insulating layer 3. Moreover, in order to ensure that the phase-change heat-insulating and heat-storing units 6 can be overlapped by rabbet, the shapes of the connection structures 10 on both sides of a single-phase change heat-insulating and heat-storing unit 6 should be different to ensure that the rabbet overlap can be realized. In the embodiment of the present invention, the connection structure 10 on one side of the phase-change heat-insulating and heat-storing unit 6 adopts a cylindrical protrusion, and the other side adopts a cylindrical groove, so that the two phase-change heat-insulating and heat-storing units 6 can be detachably self-locked and fixed after assembly and will not separate from each other during use.

[0035] As Figure 3As shown, the second spiral winding structure is presented, in which the phase change heat storage and insulation layer 3 sleeved outside the working pipe 2 adopts an assembled structure formed by spiral winding and splicing of phase change heat storage and insulation units 6. Each single phase change heat storage and insulation unit 6 is in a spiral shape wound around the outer wall of the working pipe 2. Similarly, each phase change heat storage and insulation unit 6 also includes a sealed protective shell 7, a phase change material 8, a support body 9, and a connection structure 10. The sealed protective shell 7 is also made of a heat-conducting metal material and has a sealed inner cavity inside. However, in this structure, the sealed protective shell 7 is no longer a standard fan-shaped ring, but a spiral-shaped plate body. The phase change material 8 is filled in the sealed inner cavity of the sealed protective shell 7. A support body 9 is also arranged in the sealed inner cavity of the sealed protective shell 7 as a structural reinforcement member, and the support body 9 also supports radially along the pipe in the sealed inner cavity. A connection structure 10 for tongue-and-groove splicing with other sealed protective shells 7 is provided at the splicing position of the two outer side walls of the sealed protective shell 7 along the pipe axis. In the embodiment of the present invention, the connection structures 10 on both sides of the sealed protective shell 7 can adopt stepped tongue-and-grooves that can be tightly assembled with each other. In this structure, the connection structures 10 on the phase change heat storage and insulation unit 6 also need to be arranged spirally. The pitch of the spiral-shaped sealed protective shell 7 can be set to be the same as the width of the sealed protective shell 7 itself. Thus, the outside of each section of the working pipe 2 can be spliced by two phase change heat storage and insulation units 6 to form a complete annular pipe-shaped phase change heat storage and insulation layer 3.

[0036] It should be noted that for the above Figure 2 and Figure 3 two structural forms of the phase change heat storage and insulation unit 6, tongue-and-grooves can also be provided for splicing along the pipe axis, but it is also possible not to set tongue-and-grooves but only to tightly overlap each other. The existence of partial gaps will not substantially affect the pipe insulation effect of the present invention.

[0037] In addition, in the above two structural forms of the phase change heat storage and insulation unit 6 of the present invention, the filling rate of the phase change material 8 in the sealed inner cavity of the sealed protective shell 7 should be as high as possible. It is recommended that its filling rate should be higher than 95%.

[0038] In addition, the phase change temperature range of the phase change material 8 filled inside the sealed protective shell 7 should be reasonably selected according to the steam temperature and pressure characteristics of the heat network steam in different intervals, as well as the relationship between the saturation temperature and the steam superheat degree. The phase change temperature of the phase change material 8 should be between the steam saturation temperature of the pipeline under stable operating conditions and the working temperature of the pipeline. Preferably, the phase change temperature of the phase change material 8 should be in the range of 5-10°C higher than the steam saturation temperature under stable conditions and 5-10°C lower than the stable working temperature, that is: assuming T1 is the steam saturation temperature in the steam heat preservation pipeline under stable conditions, T2 is the working temperature of the steam heat preservation pipeline under stable conditions, and ΔT is the reserved temperature deviation margin, then the preferred phase change temperature range of the phase change material 8 is [T1 + ΔT, T2 - ΔT], where ΔT = 5-10°C.

[0039] In addition, the solid-liquid phase change latent heat of the phase change material 8 should be as high as possible, preferably higher than 100 MJ / kg. The types of the phase change material 8 include but are not limited to molten salt materials, sugar alcohol materials and their mixtures.

[0040] In addition, the thermal conductivity of the phase change material 8 should not be too high to avoid absorbing the steam heat too quickly and causing the condensation phenomenon of the heat network steam. The thermal conductivity of the phase change material 8 is preferably lower than 1.0 W / (m·K).

[0041] The multi-layer heat preservation layer 4 adopted in the present invention can be composed of different heat preservation layer combinations, preferably a combination of at least two of a vacuum insulation layer, a heat preservation material filling layer and a multi-layer reflection layer. The heat preservation materials of the heat preservation material filling layer include but are not limited to one or more combinations of glass fiber, aerogel, rock wool, hard calcium silicate, foamed glass, rare earth heat preservation materials, foamed calcium silicate, polyurethane.

[0042] The outer protective layer 5 adopted in the present invention can be any layer material capable of protecting the pipeline, such as a protective layer made of corrosion-resistant materials such as metal, fiberglass composite material, high-density polyethylene, etc.

[0043] In the present invention, based on the above-mentioned load fluctuation type steam heat preservation pipeline based on phase change heat storage, a method for improving the heat preservation performance is also provided, and the specific method is as follows:

[0044] First, use the load-fluctuating steam heat-insulating pipeline as the steam transmission pipeline of the heat network in the form of new construction or renovation. Among the load-fluctuating steam heat-insulating pipelines in different sections of the heat network, the phase change material 8 in the phase change heat storage heat-insulating layer 3 needs to be selected according to the steam temperature and pressure characteristics of the section where it is located. Since the coverage of the heat network is often large and there are differences between different sections. According to the steam temperature and pressure characteristics of the heat network steam in different sections, as well as the relationship between the saturation temperature and the steam superheat degree, determine the selection range of the phase change temperature of the phase change material 8 in the phase change heat storage heat-insulating layer 3 of the entire heat network pipeline section, and determine the corresponding phase change material 8. When the entire heat network does not meet a single phase change temperature, then select the corresponding phase change material 8 in sections to ensure that the phase change temperature is between the steam saturation temperature and the working temperature under stable operating conditions. Preferably, it is in the range of 5-10°C higher than the steam saturation temperature under stable operating conditions and 5-10°C lower than the stable working temperature, that is, the aforementioned [T1 + ΔT, T2 - ΔT].

[0045] Secondly, during the operation of the heat network, according to the operating conditions inside the pipeline, adaptively utilize the cyclic heat storage and heat release capacity of the phase change material 8 inside the phase change heat storage heat-insulating layer 3 to reduce the heat loss of the pipeline, where:

[0046] Under the stable load or high load operating conditions of the heat network, the temperature of the heat network steam in the working pipe 2 is higher than the temperature of the phase change material 8. The heat network steam has a high superheat degree and the thermal conductivity of the phase change material 8 is low. At this time, the phase change heat storage heat-insulating layer 3 is heated by the slow heat release of the steam, causing the phase change material 8 to gradually melt without causing condensation of the heat network steam. Thus, while ensuring the safety and stability of the heat network, part of the heat is stored through the phase change material 8 in the phase change heat storage heat-insulating layer 3.

[0047] When the heat supply of the heat network pipeline drops significantly, resulting in a low load operating condition with a high temperature drop and large heat loss in the heat network pipeline, the temperature of the heat network steam in the working pipe 2 is lower than the temperature of the phase change material 8. The phase change material 8 in the phase change heat storage heat-insulating layer 3 maintains the temperature of the phase change heat storage heat-insulating layer 3 constant through the constant temperature solidification heat release process, so as to ensure that the temperature difference between the steam in the working pipe 2 and the phase change heat storage heat-insulating layer 3 remains unchanged and is higher than the phase change temperature of the phase change material 8, thereby avoiding the phenomenon of rapid temperature drop and condensation loss caused by direct external heat dissipation of the steam, and ensuring the occurrence of heat loss due to heat dissipation under low flow conditions.

[0048] Since the heat network load shows regular or irregular periodic fluctuations, the charging and discharging processes of the phase change material 8 in the phase change heat storage heat-insulating layer 3 are realized, and the surplus heat energy under stable load or high load conditions is used to maintain the heat dissipation under low load conditions, ultimately ensuring the reduction of heat loss in the heat network or local pipeline sections.

[0049] Next, the above-mentioned load-fluctuating steam insulation pipeline based on phase change heat storage and the corresponding method for improving the insulation performance will be applied to a specific embodiment to demonstrate the technical effects that can be achieved.

[0050] Embodiment

[0051] In this embodiment, the above-mentioned load-fluctuating steam insulation pipeline based on phase change heat storage and the corresponding method for improving the insulation performance are as described above and will not be elaborated here. The following mainly shows the corresponding specific parameters and technical effects.

[0052] For a branch steam heating pipeline with a diameter of 500 mm and a length of 100 m, when supplying steam normally, the steam temperature is 220 °C and the pressure is 1.0 MPa. This heating pipeline supplies heat to users periodically, heating for 12 hours during the day and stopping supply for 12 hours at night. The insulation material used is foamed calcium silicate, with a thermal conductivity of 0.088 W / (m·K) at 200 °C and an average surface heat dissipation heat flux of 30 W / m 2 . When the load-fluctuating steam insulation pipeline based on phase change heat storage is not used, the steam in the pipe will drop to the saturation temperature and gradually condense. The change in the steam temperature in the pipe is as shown by the dotted line in Figure 4 . During the period of stopping supply at night, the steam condensation rate in the pipe is 8.034 kg / h, and 96.41 kg of condensed water will be generated during the stopping supply period. When heating resumes the next day, steam is needed to discharge the condensed water in the pipe. According to measurement and calculation, discharging 1 kg of condensed water by the steam trap consumes approximately 0.02 kg of steam, and the steam loss caused by drainage is 1.93 kg, with a direct heat loss of 4074.9 kJ / d, which is equivalent to wasting 0.14 kg of standard coal per such pipeline per day.

[0053] If the above-mentioned branch steam heating pipeline adopts the load-fluctuating steam insulation pipeline based on phase change heat storage of the present invention, using a mixture of 40% sodium nitrite (NaNO2) and 60% sodium nitrate (NaNO3) molten salt as the phase change material, with a phase change temperature of 205 °C and a phase change latent heat of about 100 kJ / kg, the thickness of the phase change heat storage insulation layer should not be less than 7 mm. After being fully charged during the day's heating period, the heat released by the phase change material at night is sufficient to keep the steam temperature in the pipe always higher than the saturation temperature, avoiding the generation of condensed water and eliminating the huge heat loss caused by drainage during the next day's heating, achieving a very good insulation effect. The change in the steam temperature in the pipe is as shown by the solid line in Figure 4 .

[0054] It can be seen from the above embodiments that the present invention utilizes the characteristics of constant temperature and high energy storage density of the phase change heat storage insulation layer to achieve heat dissipation blocking between high-temperature steam and the environment, and the adiabatic insulation effect is very prominent. At the same time, the system uses the working medium of the system itself as the heat source, enabling the phase change heat storage insulation layer to operate continuously, stably, and spontaneously in a cycle without additional energy consumption.

[0055] The above-described embodiments are only some preferred implementation solutions of the present invention, but are not intended to limit the present invention. Those of ordinary skill in the relevant technical field can also make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A load-fluctuation type steam heat-insulating pipeline based on phase change heat storage, characterized in that It includes a working pipe (2), a phase change heat storage and insulation layer (3), a multi-layer insulation layer (4), and an outer protective layer (5); the inside of the working pipe (2) is used to transport the working fluid (1), and the outer wall of the working pipe (2) is coaxially provided with a phase change heat storage and insulation layer (3), a multi-layer insulation layer (4), and an outer protective layer (5) in sequence; the phase change heat storage and insulation layer (3) is assembled by a series of phase change insulation and heat storage units (6) in a tongue-and-groove splicing manner, and is circumferentially attached around the outer wall of the working pipe (2). The phase change temperature of the phase change material (8) filled in each phase change insulation and heat storage unit (6) is between the steam saturation temperature and the working temperature under stable operating conditions.

2. The load fluctuation type steam heat preservation pipeline based on phase change heat storage according to claim 1, characterized in that The phase change insulation and heat storage unit (6) includes a sealed protective shell (7), a phase change material (8), a support body (9), and a connection structure (10). The phase change material (8) is filled in the sealed inner cavity of the sealed protective shell (7). The support body (9) is used as a structural reinforcement member and is radially supported in the sealed inner cavity of the sealed protective shell (7) along the pipeline. The connection structure (10) for tongue-and-groove splicing with other sealed protective shells (7) is provided at the splicing position on the outer side wall of the sealed protective shell (7).

3. The load fluctuation type steam heat preservation pipeline based on phase change heat storage according to claim 1, wherein The phase change heat storage and insulation layer (3) adopts an assembled structure in which the phase change insulation and heat storage units (6) are spliced along the axis and circumferentially. A single phase change insulation and heat storage unit (6) is in a sector ring shape. The extension direction of the connection structure (10) on the phase change insulation and heat storage unit (6) is along the axial direction of the pipeline. The outside of each section of the working pipe (2) is spliced by a plurality of phase change insulation and heat storage units (6) around the circumference to form a complete annular pipeline-shaped phase change heat storage and insulation layer (3).

4. The load fluctuation type steam heat preservation pipeline based on phase change heat storage according to claim 1, wherein, The phase change heat storage and insulation layer (3) adopts an assembled structure in which the phase change insulation and heat storage units (6) are spirally wound and spliced. A single phase change insulation and heat storage unit (6) is in a spiral shape wound around the outer wall of the working pipe (2). The connection structure (10) on the phase change insulation and heat storage unit (6) is also spirally arranged. The outside of each section of the working pipe (2) is spliced by two phase change insulation and heat storage units (6) to form a complete annular pipeline-shaped phase change heat storage and insulation layer (3).

5. A load fluctuation type steam heat preservation pipeline based on phase change heat storage according to claim 2, characterized in that, The filling rate of the phase change material (8) in the sealed inner cavity of the sealed protective shell (7) is higher than 95%.

6. The load fluctuation type steam heat preservation pipeline based on phase change heat storage according to claim 1, characterized in that The phase change temperature range of the phase change material (8) is [T1 + ΔT, T2 - ΔT], where T1 is the steam saturation temperature in the steam insulation pipeline under stable operating conditions, T2 is the working temperature of the steam insulation pipeline under stable operating conditions, and ΔT = 5 - 10°C.

7. The load fluctuation type steam heat preservation pipeline based on phase change heat storage according to claim 2, wherein, The solid-liquid phase change latent heat of the phase change material (8) is higher than 100 MJ / kg. The types of the phase change material (8) include, but are not limited to, molten salt materials, sugar alcohol materials, and their mixtures.

8. A load fluctuation type steam heat preservation pipeline based on phase change heat storage according to claim 2, characterized in that, The thermal conductivity of the phase change material (8) is lower than 1.0 W / (m·K).

9. The load fluctuation type steam heat preservation pipeline based on phase change heat storage according to claim 1, characterized in that, The multi-layer insulation layer (4) adopts a combination of at least two of a vacuum insulation layer, a heat insulation material filling layer, and a multi-layer reflection layer; the heat insulation materials of the heat insulation material filling layer include one or more combinations of glass fiber, aerogel, rock wool, hard calcium silicate, foamed glass, rare earth heat insulation materials, foamed calcium silicate, and polyurethane.

10. A method for improving the heat insulation performance of a load-fluctuating steam heat-insulating pipeline based on phase change heat storage according to any one of claims 1 to 9, characterized in that: First, the load-fluctuating steam heat-insulating pipeline is used as the steam transmission pipeline of the heat network in the form of new construction or renovation. In the load-fluctuating steam heat-insulating pipelines in different sections of the heat network, the phase change material (8) in the phase change heat storage insulation layer (3) needs to be selected according to the steam temperature and pressure characteristics of the section where it is located, so as to ensure that the phase change temperature of the phase change material (8) is between the steam saturation temperature and the working temperature under stable conditions in the section where it is located; Secondly, during the operation of the heat network, according to the operating conditions inside the pipeline, the cyclic heat storage and heat release capacity of the phase change material (8) inside the phase change heat storage insulation layer (3) is adaptively used to reduce the heat loss of the pipeline, where: When the temperature of the heat network steam in the working pipe (2) is higher than the temperature of the phase change material (8), at this time, the phase change heat storage insulation layer (3) is heated by the slow heat release of the steam, so that the phase change material (8) gradually melts without causing condensation of the heat network steam, so that while ensuring the safety and stability of the heat network, part of the heat is stored through the phase change material (8) in the phase change heat storage insulation layer (3); When the temperature of the heat network steam in the working pipe (2) is lower than the temperature of the phase change material (8), the phase change material (8) in the phase change heat storage insulation layer (3) maintains the temperature of the phase change heat storage insulation layer (3) constant through the isothermal solidification heat release process, so as to ensure that the temperature difference between the steam in the working pipe (2) and the phase change heat storage insulation layer (3) remains unchanged and is higher than the phase change temperature of the phase change material (8), thereby avoiding the phenomenon of rapid temperature drop and condensation loss caused by direct external heat dissipation of the steam and reducing the heat loss of the pipeline.

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