Pipeline passive zero energy consumption freeze-proofing device based on PCM

An antifreeze device and zero energy consumption technology, which is applied in pipeline anticorrosion/rust protection, pipeline protection, pipeline heating/cooling, etc., to achieve the effects of enhancing stability, strengthening heat transfer, and prolonging antifreeze time

Pending Publication Date: 2020-06-23
BEIJING GENERAL MUNICIPAL ENG DESIGN & RES INST
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AI-Extracted Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to provide a passive zero-energy antifreeze device for pipelines based on PCM to solve the antifreeze technical problems of pipelines without powe...
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Method used

[0034] The PCM mentioned in the present invention, that is, phase change material (phase change material), refers to a class of materials that can absorb or release a large amount of energy (ie phase change enthalpy) when a substance undergoes a phase change. Phase change materials u...
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Abstract

The invention discloses a pipeline passive zero energy consumption freeze-proofing device based on PCM. The pipeline passive zero energy consumption freeze-proofing device based on PCM comprises a work pipe, an erosion resistant coating, a PCM layer, an embedded support, a case pipe and a heat insulation layer. The work pipe (1) is located on the innermost side; the erosion resistant coating is located on the outer side of the work pipe (1); the PCM layer (3) is located in a cavity structure between the erosion resistant layer (2) and the case pipe (5); the embedded support (4) is also locatedbetween the erosion resistant layer (2) and the case pipe (5); and the heat insulation layer (6) is attached to the outer side of the case pipe (5) and serves as the outermost layer structure. The PCM layer (3) is filled with a phase-change medium which is liquid at the room temperature; the embedded support (4) used for fixing the cavity structure between the erosion resistant coating (2) and the case pipe (5) are of a branch-shaped structure; and the case pipe (5) and the erosion resistant coating (2) provide a containing cavity for the PCM layer (3) together. The pipeline passive zero energy consumption freeze-proofing device based on PCM can achieve the technical purposes that no power facility or energy consumption is needed, the structure is simple, implementation is easy, operationand maintenance are convenient, and the requirements for energy conservation and environment protection are met.

Application Domain

Thermal insulationPipe heating/cooling +4

Technology Topic

Composite materialEngineering +3

Image

  • Pipeline passive zero energy consumption freeze-proofing device based on PCM
  • Pipeline passive zero energy consumption freeze-proofing device based on PCM

Examples

  • Experimental program(1)

Example Embodiment

[0033] For the specific structure of the present invention, see figure 1 , 2 , It is a composite layered tube structure including working tube, anti-corrosion layer, PCM layer, embedded bracket, casing and heat insulation layer.
[0034] The PCM mentioned in the present invention, or phase change material, refers to a type of material that can absorb or release a large amount of energy (ie, phase change enthalpy) when a substance undergoes a phase change. Phase change materials use latent heat to store and release heat. They have the characteristics of high heat storage density, compact structure of the heat storage device, basically constant temperature during the phase change process, and easy management. They have great potential for engineering applications.
[0035] The working tube 1 is located at the innermost side and is used to transmit the working medium; the PCM layer 3 is located in the cavity structure between the anti-corrosion layer 2 and the sleeve 4, and the inside is filled with PCM that is liquid at room temperature. The solid-liquid phase transition temperature is 5.5°C, and the solid-state thermal conductivity is about 0.15W/(m·°C), which is lower than that of most thermal insulation materials; the embedded bracket 4 is located between the anti-corrosion layer 2 and the The sleeves 5 are used for fixing and supporting to form a cavity structure; the thermal insulation layer 6 is attached to the outer side of the sleeve 5 and is the outermost structure.
[0036] The core of the device is to infuse the PCM layer 3 with a liquid phase change medium at room temperature. The solid-liquid phase change temperature of this medium is close to and higher than the antifreeze temperature (non-freezing temperature) of the working medium. When the ambient temperature is lower than the antifreeze temperature, the PCM material gradually releases the latent heat of phase change until all becomes solid, after which the medium becomes an insulation layer (the solid thermal conductivity is lower than that of most thermal insulation materials), and continues to protect The working medium reaches the end of the antifreeze period. In practical applications, different PCM materials are selected according to the working medium and antifreeze time.
[0037] The built-in bracket 4 is used to keep the cavity between the anti-corrosion layer 2 and the sleeve 5 fixed and to accommodate PCM. The built-in bracket 4 has a branch-like structure, which is convenient for both sides of the built-in bracket 4 Liquid PCM flows with each other, which is conducive to PCM perfusion.
[0038] The sleeve 5 and the anti-corrosion layer 2 provide a containing cavity for the PCM layer 3 together. The insulation layer 6 provides support and fixation.
[0039] The thermal insulation layer 6 is attached to the outside of the sleeve 5 and is the outermost structure. The thermal insulation layer 6 reduces the heat release rate of the PCM layer 3 and maintains the phase change latent heat of the PCM layer 3 to gradually and controllably release.
[0040] When the ambient temperature is higher than the freezing point of the PCM, it is in a non-freezing state. At this time, the PCM is in a liquid state and is in a heat storage state, and together with the heat insulation layer 5 plays a role of heat preservation and heat insulation.
[0041] When the ambient temperature is lower than the freezing point of the PCM, it enters the antifreeze state. The PCM in the PCM layer 3 begins to release latent heat and gradually changes from liquid to solid. The heat release process has the following characteristics:
[0042] A. Since the temperature difference is the driving force for heat transfer, and the temperature of the medium in the working tube 1 is always not lower than the temperature of the PCM layer 3, the heat transfer is unidirectional and always transfers towards the direction of the insulation layer.
[0043] B. Due to the protection of the thermal insulation layer 6, the heat release rate of the PCM layer 3 is slow. Generally, in the design, after the insulation layer is provided, the heat release rate of the pipeline is about 50W/(㎡·℃). In comparison, the PCM phase change latent heat is huge. Therefore, the PCM in the PCM layer 3 needs to be quite long Time to complete the phase change process.
[0044] C. The PCM layer 3 has temperature stability during the phase change process. Due to the B feature, the pipeline is in the process of solid-liquid conversion for a long time, and the substance is approximately a constant temperature process during the phase change process, so the PCM layer 3 will remain at the freezing point and the temperature will not change for a long period of time. This feature is conducive to the stable operation of the working pipeline.
[0045] D. Due to the existence of the PCM layer 3, the working tube 1 has a heat release vacuum period. The characteristic of this property is that if the temperature of the medium in the working tube is higher than the temperature of the PCM layer, the heat will continue to pass through the PCM layer to the insulation layer, thereby prolonging the curing time of the PCM layer; when the temperature of the working medium is the same as the temperature of the PCM layer, it will no longer The reason is that the two temperatures are the same and there is no heat transfer power. Therefore, during the liquid-solid conversion of the PCM layer, the working medium will be in a vacuum state of heat release for a long time and will not release heat to the outside world. This state is of great significance to the antifreeze of the pipeline.
[0046] E. After the PCM layer is completely transformed into a solid phase, it evolves into an insulating material. Since the thermal conductivity of the selected PCM material in solid phase is lower than that of conventional thermal insulation materials, after the PCM layer is completely transformed into a solid phase, the PCM layer 3 completely evolves into a thermal insulation layer. The significance of this feature is that the freezing point of the PCM is close to and higher than the antifreeze temperature of the pipeline medium of the working pipe 1, and is much higher than the freezing temperature of the pipeline medium of the working pipe 1. When extreme weather occurs, even if the PCM layer 3 is completely transformed into a solid state, it can still be used as a good thermal insulation material. Together with the thermal insulation layer 6, a new superimposed thermal insulation layer is formed, which reduces the heat release rate and slows down the The transition of the medium in the working tube from the antifreeze temperature to the freezing temperature in the working tube 1 can effectively extend the freezing time of the medium in the working tube 1.
[0047] In summary, the present invention has the characteristics of large amount of heat storage during the non-freezing period, high-efficiency anti-freezing and insulation during the anti-freezing period, slow heat release rate, long anti-freezing time, safety and stability, etc., and is an efficient, safe and environmentally friendly anti-freezing method.

PUM

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