CFRP oil delivery pipe inner wall temperature field homogenization graphite film laying method for deep sea heavy oil recovery and application

Abstract

The invention relates to a carbon fiber reinforced plastic (CFRP) oil delivery pipe inner wall temperature field homogenization graphite film laying method for deep sea thickened oil recovery and application. According to the method, the characteristics of high in-plane heat conduction and low thickness heat conduction of the graphite film are utilized, the graphite film serves as a heat diffusion bridge between beams, heat is directionally guided to flow along a cold area between the beams, the temperature field of the inner wall is more uniform, and meanwhile heat loss in the seawater direction is restrained. A heating beam-graphite film-heating beam is taken as a basic unit, and a parameter combination enabling the distribution of an inner wall temperature field to be most uniform is sought as an optimal solution by determining key parameters, including an included angle between the graphite film and the carbon fiber heating beam, the width of the graphite film, an effective heat transfer distance along the film and the like, of the size of the unit. After optimal parameters are obtained, array expansion is carried out in the circumferential direction and the axial direction of the pipeline, and overall uniform heat distribution is achieved. For different pipe sections, a differential laying strategy can be adopted according to the difference between water depth and external heat exchange conditions, so that the temperature fields of the inner walls of the pipe sections tend to be consistent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of deep-sea heavy oil recovery, in particular, especially relates to a CFRP oil pipeline inner wall temperature field homogenization graphite film laying method for deep-sea heavy oil recovery and application. BACKGROUND

[0002] Deep-sea heavy oil recovery and transportation often occur in low-temperature and high-pressure environments (such as water depths of thousands of meters, and seawater temperatures of about several degrees Celsius), and the viscosity of leaked or stranded heavy oil increases sharply, is prone to wax precipitation and coagulation, and the oil exhibits near-solid rheological properties. Therefore, effective viscosity reduction measures must be taken to reduce the shear resistance and increase the flowability of the oil to restore its transportability.

[0003] Existing projects mainly adopt two types of schemes: one is seawater replacement, which implements forward or reverse replacement of the submarine pipeline through a platform pump group; and the other is electric heating lifting, which uses electric cables arranged inside and outside the pipeline to heat the oil in the pipeline. The former requires a larger process system to be added to the surface platform, and the operation is complex and costly. The latter is more commonly used, but the traditional method relies on thick-walled metal pipes and an outer insulation structure in combination with electric heating cables. The overall weight is large, and it is difficult to lay and recover. In addition, there is a risk of corrosion and leakage of the metal in the submerged state in seawater, and the long-term maintenance cost is high. Driven by the strong temperature difference between the inner heat and the outer cold, the heat of the deep-sea oil pipeline will continue to dissipate along the thickness direction to the seawater side, resulting in large heat loss along the way and high energy consumption. To meet the temperature maintenance requirements, existing schemes often compensate by increasing power or increasing the density of heat sources, but this leads to problems such as local overheating, material aging, and energy efficiency decline.

[0004] In recent years, in order to reduce the weight and corrosion risk, composite heating pipelines have appeared, which use carbon fiber reinforced composite materials (CFRP) to replace metal-based pipes, and use continuous carbon fiber filaments as self-resistance heating elements. This type of structure is light in weight, corrosion-resistant, and has high axial thermal conductivity and high efficiency of electric heating conversion, which is conducive to heating and lifting in deep-sea environments. However, due to the discrete distribution of linear heat sources, the circumferential temperature of the pipe wall is still prone to form a "cold zone" with a temperature lag between adjacent heating beams. The uneven temperature of the pipe wall reduces the heating efficiency and makes the energy utilization worse. Simply increasing the power or increasing the heating beam density can raise the temperature, but the cost is high and it is easy to cause local overheating below the beam, exceeding the temperature resistance limit of the material and coating.

[0005] Therefore, there is an urgent need for a CFRP oil pipeline inner wall temperature field homogenization method for deep-sea heavy oil recovery, which can raise the cold zone between the beams and improve the uniformity of the inner wall temperature without significantly increasing the power, so that the inner wall temperature field of the pipe section under different water depths and external heat exchange conditions is uniformly distributed. SUMMARY

[0006] The application discloses a CFRP oil pipeline inner wall temperature field homogenization graphite film laying method and application for deep-sea thick oil recovery.

[0007] The technical means adopted by the application are as follows: The CFRP oil pipeline inner wall temperature field homogenization graphite film laying method for deep-sea thick oil recovery comprises the following steps: The graphite film is pasted between adjacent carbon fiber heating beams of the CFRP pipeline, the graphite film is used as a heat transfer medium between the beams, heat is directionally guided to the low-temperature area between the beams, and radial heat loss is inhibited; The "heating beam-graphite film-heating beam" is used as a minimum repeating unit, the parameter combination is determined according to the relative angle between the graphite film and the heating beam, the graphite film width and the effective heat transfer length along the film, the parameter combination is determined by quantifying the heat convergence effect and the heat loss inhibition degree, and the heat is uniformly distributed in the unit; The pipeline is divided into different zones based on the external heat exchange conditions of different sections of the pipeline, the parameter combination is matched for each zone, independent energy supply control is implemented for each zone, the heating power is adjusted to adapt to the heat exchange requirement of the zone, and the heat exchange requirement of the zone is adjusted; The difference between the temperature at the center line of the minimum repeating unit and the average temperature of the projection of the two sides of the heating beam is used as the center temperature difference, the center temperature difference is normalized to evaluate the temperature field uniformity, and it is ensured that the temperature field of the oil pipeline inner wall meets the preset uniformity requirement.

[0008] Further, the relative angle between the graphite film and the heating beam comprises an oblique intersection and an approximate orthogonal intersection, the oblique intersection angle is set to preferentially improve the temperature of the low-temperature area between the beams, and the approximate orthogonal angle is set to preferentially diffuse the local high temperature near the heating beam and prevent the material from overheating.

[0009] Further, the graphite film width and the effective heat transfer length along the film are determined according to the heating beam spacing, so that the graphite film and the carbon fiber heating beam have sufficient contact area to obtain heat, while excessive heat diffusion to non-target areas is avoided, and the temperature field homogenization effect and the overall energy consumption are balanced.

[0010] Further, the normalized center temperature difference refers to taking the ratio of the center temperature difference to the average temperature of the projection of the two sides of the heating beam as an evaluation index, the influence of the absolute temperature difference on the uniformity judgment is eliminated through the index, and the uniformity of the temperature field under different working conditions is uniformly evaluated.

[0011] Further, the pipeline partition is based on water depth, combined with the heat transfer intensity difference of different water depths to divide the partition, and adapt to the external heat transfer conditions of each partition.

[0012] Further, the independent energy supply control refers to matching the differentiated heating power adjustment strategy based on the parameter combination of each partition, compensating for the partition heat transfer difference by adjusting the heating power, and further optimizing the temperature field uniformity of each partition.

[0013] Further, the minimum repeating unit is arrayed along the circumferential and axial directions of the CFRP oil conveying pipe to form a continuous in-plane heat conduction network, so that the heat can be compensated between adjacent repeating units, and local temperature imbalance is avoided.

[0014] Further, the in-plane high thermal conductivity of the graphite film is used to guide heat to the inter-beam low-temperature area, and the low thermal conductivity in the thickness direction is used to reduce heat loss to the outside of the oil conveying pipe, and the temperature field uniformity and heat loss suppression are realized by the cooperation of the two characteristics.

[0015] Further, it also includes a verification step of the temperature field uniformity of the inner wall of the CFRP oil conveying pipe: monitoring the circumferential temperature distribution of the inner wall of the oil conveying pipe, calculating the maximum circumferential temperature difference, and ensuring that the maximum circumferential temperature difference and the normalized central temperature difference both meet the preset threshold to determine whether the temperature field uniformity meets the standard.

[0016] The application also discloses a deep-sea heavy oil recovery CFRP oil conveying pipe based on the above method, which comprises a high-thermal-conductivity anti-seepage coating, carbon fiber heating beams, a graphite film and a carbon fiber winding pressure-resistant layer arranged in sequence; the graphite film is attached between adjacent carbon fiber heating beams to form a repeating structure of "heating beam-graphite film-heating beam", and the pipeline is provided with a segmented independent power supply circuit along the axial direction to adapt to the energy supply control requirement of the partition.

[0017] In summary, the application uses carbon fiber beam electric heating to rapidly heat, guides heat to flow along the inter-beam cold area through the graphite film, directly reduces the temperature difference between the inter-beam and the heat source area, and makes the inner wall temperature field more uniform, so that the flowability of the oil in the long-distance pipeline is maintained without increasing too much energy consumption. The application takes "heating beam-graphite film-heating beam" as the minimum unit, optimizes the relative angle of the graphite film and the heating beam, the width of the graphite film and the effective heat transfer length along the film, ensures that the heat is uniformly distributed in the unit, and then arrayed along the circumferential and axial directions to form a continuous heat conduction network of the whole pipeline. This composite heating pipeline does not need traditional metal pipes and large thickness insulation layers, the overall weight is reduced, the corrosion resistance is improved, and the problem of insufficient heat coverage of pure electric heating is overcome, thereby providing a new solution for efficient mining and conveying of deep-sea heavy oil, wax oil and other low-temperature high-viscosity media. BRIEF DESCRIPTION OF DRAWINGS

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the carbon fiber heated oil pipeline structure for deep-sea heavy oil recovery according to the present invention.

[0020] Figure 2 This is a schematic diagram of the smallest repeating unit in the plane of "carbon fiber heating bundle - graphite film - carbon fiber heating bundle".

[0021] Figure 3 This is a schematic diagram showing the tiling of the cells along the circumference and axis.

[0022] Figure 4 This is a schematic diagram of the test results when the current is 0.71A.

[0023] Figure 5 The graph shows the test results when the current is 0.71A.

[0024] In the figure: 1. High thermal conductivity and anti-seepage coating; 2. Graphite film; 3. Carbon fiber heating bundle; 4. Carbon fiber wound pressure-resistant layer.

[0025] In the figure: a, b, and c represent the temperatures at each measurement point when the heat transfer distance is 2cm, 1cm, and 0.5cm, respectively; d, e, and f represent the temperatures at each measurement point when the heat transfer distance is 1cm and the width is 2cm, 1cm, and 0.5cm, respectively; g, h, and i represent the temperatures at each measurement point when the heat transfer distance is 1cm, the width is 1cm, and the angle is 0 degrees, 30 degrees, and 60 degrees, respectively. Detailed Implementation

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] 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 following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] It is also important to note that the term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. The description is intended to include all possible combinations of elements and features, whether specific or implicit, that are described herein. The terms "comprises," "comprising," "includes," "including," "contains," "containing," "has," "having," "may," "might," "must," "must not," "need," "needs," "not," "or," "shall," "shalls," "should," "should not," "such as," "very," "will," "will not," and the like are to be understood as open-ended terms that are to be interpreted in the context of this patent document. They are not to be limited to the literal language. Rather, they are to be interpreted in the context of the specification as a whole. Such terms are to be interpreted to mean "including but not limited to." Such terms are to be interpreted as meaning "comprising." Such terms are to be interpreted as meaning "including." Such terms are to be interpreted as meaning "consisting of." Such terms are to be interpreted as meaning "consisting essentially of." Such terms are to be interpreted as meaning "comprising." Such terms are to be interpreted as meaning "including." Such terms are to be interpreted as meaning "consisting of." Such terms are to be interpreted as meaning "consisting essentially of."

[0029] The recitation of elements in a list is not to be construed as an implied elimination of any remaining elements not specifically recited. The relative arrangement of components and steps, the numerical expressions, and numerical values set forth in the examples provided herein are not intended to limit the scope of the application. The various aspects of the application can be further understood in light of the following examples.

[0030] In the description of the present application, it is to be understood that the specific location or position relationships indicated by the orientation words such as "front, back, upper, lower, left, right", "horizontal, vertical, perpendicular, horizontal" and "top, bottom" and the like are generally based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Without the opposite indication, these orientation words do not indicate and imply that the indicated device or element must have a specific orientation or be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the scope of protection of the present application: the orientation words "inner, outer" refer to the inner and outer relative to the contour of the components themselves.

[0031] For purposes of the description hereinafter, spatially relative terms, such as "above", "below", "up", "down", "between", "within", "left", "right", "front", "back", "upper", "lower", "horizontal", "vertical", "above", "below", "up", "down", "top", "bottom", "side", "end", etc., can be used to describe the relative position of one element to another as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. For example, if a device in the figures is inverted, elements described as "above" or "up" other elements or structures can be oriented "below" or "down" the other elements or structures. Thus, the exemplary term "above" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. For example, if a device in the figures is inverted, elements described as "above" or "up" other elements or structures can be oriented "below" or "down" the other elements or structures. Thus, the exemplary term "above" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0032] In addition, it should be noted that the use of "first", "second", etc. words to define parts, only for the convenience of distinguishing the corresponding parts, as there is no declaration, the above words have no special meaning, therefore, cannot be understood as a limitation on the scope of protection of the present application.

[0033] The embodiment of the present application discloses a CFRP oil pipeline inner wall temperature field uniformization graphite film laying method for deep-sea thick oil recovery, graphite film is pasted between adjacent carbon fiber heating beams of the CFRP pipeline, the graphite film has the characteristics of high in-plane thermal conductivity and low thickness direction thermal conductivity, as a heat transfer medium between beams, it is used to guide heat flow to the low temperature area between beams and inhibit radial heat loss; based on the external heat exchange conditions of different sections of the pipeline axis, the pipeline is divided into zones, and the matching graphite film laying parameter combination is determined for each zone, the parameter combination includes the relative angle of the graphite film and the heating beam, the graphite film width and the effective heat transfer length along the film, the parameter combination is determined by quantifying the heat convergence effect and heat loss inhibition degree, and the heat is uniformly distributed in the unit; independent energy supply control is implemented for each zone to adjust the heating power respectively; meanwhile, electrodes are arranged at both ends of the CFRP pipeline wound by continuous carbon fiber filaments and connected with a working power supply, so that the carbon fiber filaments act as a self-resistance heating body to supply heat to the pipeline wall; the method further includes a temperature field uniformity evaluation step: taking the difference between the temperature at the center line of the minimum repeating unit and the average temperature at the projection of the two heating beams as the center temperature difference, evaluating the temperature field uniformity by normalizing the center temperature difference (taking the ratio of the center temperature difference to the average temperature at the projection of the two heating beams as the evaluation index), and ensuring that the temperature field of the oil pipeline inner wall meets the preset uniformity requirement.

[0034] The graphite film adopts an array expansion mode with "heating beam-graphite film-heating beam" as the minimum repeating unit, so that the heat from adjacent heating beams converges in the inter-beam region; the array expansion is laid out along the circumferential and axial directions of the CFRP oil pipeline to form a continuous in-plane heat conduction network, so that the heat between adjacent repeating units can be mutually compensated to avoid local temperature imbalance; and the array expansion is implemented based on a preferred parameter combination at the unit level, which is determined by experimental numerical analysis and can raise the inter-beam low temperature and make the inner wall temperature field uniformly distributed under the premise of equal energy supply.

[0035] The relative angle between the graphite film and the heating beam is oblique or approximately orthogonal; when the graphite film is arranged obliquely, its in-plane heat conduction path is directed to the inter-beam low temperature area to preferentially raise the temperature in this area; when the graphite film is arranged approximately orthogonally, its heat conduction path mainly spans the heat source concentration area formed by the direct contact between the heating beam and the inner surface of the pipeline wall, aiming to preferentially diffuse and suppress the local temperature peaks caused by the direct action of the heat source, prevent overheating of the material at this point, and optimize the distribution of heat to the circumferential direction.

[0036] The width of the graphite film and the effective heat transfer length along the film are determined according to the heating beam spacing matching principle to ensure that the graphite film and the carbon fiber heating beam have sufficient contact area to obtain heat, while avoiding excessive heat diffusion to non-target areas due to excessive contact area, thereby balancing between temperature field uniformization and overall energy consumption.

[0037] The independent energy supply control for each subzone is based on the graphite film laying parameters determined for different subzones to match different segment current powers, power-on timing or pulse width modulation strategies; the energy supply mode of the independent energy supply control is a multi-segment independent loop to cooperate with subsequent subzone temperature control, compensate for the heat exchange differences between subzones by adjusting the heating power, and further optimize the temperature field uniformity of each subzone.

[0038] It also includes a CFRP oil pipeline inner wall temperature field uniformity verification step: monitoring the circumferential temperature distribution of the inner wall of the oil pipeline, calculating the circumferential maximum temperature difference, ensuring that the circumferential maximum temperature difference and the normalized central temperature difference both meet the preset threshold, and determining whether the temperature field uniformization meets the standard.

[0039] The pipeline subzones are divided based on water depth as the core basis and the heat exchange intensity differences of different water depths to adapt to the external heat exchange conditions of each subzone, so that the inner wall temperature field of the pipeline section under different water depths and external heat exchange conditions is uniformly distributed.

[0040] Example 1 The Figure 1This is a schematic diagram of the carbon fiber heated oil pipeline used in deep-sea heavy oil recovery according to the present invention. The diagram clearly shows the core functional layers from the inside out: the carbon fiber heating bundle 3 serves as a self-insulating heat source; the graphite film 2 is laid between adjacent heating bundles to conduct heat and guide current; the carbon fiber wound pressure-resistant layer 4 provides structural support; and the innermost wall is provided with a high thermal conductivity anti-seepage coating 1 for dielectric protection and also for internal wall heat conduction. This overall structure embodies the invention's goal of achieving "heating..." thermal conductivity Pressure resistance Integrated design that integrates "protection".

[0041] The Figure 2 This is a schematic diagram of the smallest repeating unit in a "carbon fiber heating bundle-graphite film-carbon fiber heating bundle" structure. The diagram shows that when the fiber direction is 0° as the reference, the graphite film can be laid at 0° or other tilt angles, and the division of the smallest repeating unit at different angles is marked accordingly, intuitively reflecting the core purpose of guiding the directional transfer of heat by adjusting the orientation of the graphite film.

[0042] The Figure 3 This diagram illustrates the deployment of the smallest repeating unit along a laminate array. It demonstrates how to combine optimal parameters determined by the unit size and array them across the entire laminate, validating the feasibility of the proposed method in engineering applications.

[0043] The Figure 4 The figure shows the steady-state temperature distribution infrared test results under the conditions of 0.71A current and a 60° angle between the graphite film and the carbon fiber bundle. The figure clearly shows the thermal field morphology of the carbon fiber bundle and graphite film regions, directly verifying that the oblique laying method can effectively guide heat transfer to the inter-bundle region, significantly improving the cold zone problem between traditional linear heat sources, and confirming the correctness of the minimum repeating unit model and its array expansion method.

[0044] The Figure 5 The figure shows the experimental results when the current is 0.71A. This set of experimental data verifies that by coordinating key parameters such as "heat transfer distance-width-angle", the temperature field of the inner wall can be actively controlled and homogenized, providing a direct basis for the optimal parameter combination of this invention.

[0045] Where: a, b, and c represent the temperatures at each measurement point when the heat transfer distance is 2cm, 1cm, and 0.5cm, respectively, reflecting the influence of the heat transfer distance on temperature uniformity, with 1cm being the optimal value; Where: d, e, and f represent the temperatures at each measurement point when the heat transfer distance is 1cm and the widths are 2cm, 1cm, and 0.5cm respectively. The heat diffusion effect under different graphite film widths was compared, and 1cm was the best. Where: g, h, i represent the temperature of each measuring point when the heat transfer distance is 1 cm, the width is 1 cm, and the angle is 0 degrees, 30 degrees, and 60 degrees, respectively, showing the key role of the laying angle of the graphite film on the temperature distribution. At 0 degrees, the heat directly crosses the two beams, the temperature difference between the three points is the smallest, the uniformity is the best, but the center temperature is low and there is still a cold area; at 30 degrees, the diagonal convergence is the strongest, the center temperature rises to 82.6°C, and the cold strip is effectively smoothed out, but the peak value at the contact point is too high, which has the risk of overheating. At 60 degrees, the beam bridging is weakened, and the diffusion along the beam is enhanced, the center is higher than 0° and the peak value is lower than 30°.

[0046] Minimum repeating unit parameter determination: The minimum repeating unit is composed of two adjacent carbon fiber heating beams and the graphite film between them. The key parameters to be determined include: the orientation angle θ of the heating beam and the graphite film, the width W of the graphite film, the heat transfer distance L along the film, etc.

[0047] Laying out of the minimum repeating unit along the circumferential / axial direction: When the laying combination in the unit is determined, it can be laid out along the circumferential and axial directions, forming a continuous in-plane heat conduction channel, so that the heat between adjacent segments can be compensated.

[0048] Axial zoning temperature control: The external heat exchange condition of the deep-sea riser changes significantly with water depth (the deeper the lower the temperature, the stronger the heat dissipation). Therefore, longitudinal zoning is needed, and the pipe segment is divided into several sections according to the service water depth and heat dissipation intensity. Different parameter combinations (laid orientation of graphite film and heating beam, graphite film width, effective heat transfer distance along the film) can be selected for each section, and on-demand temperature control can be achieved through segmented power supply.

[0049] Coordination with CFRP self-resistance heating layer: This method is based on the existing CFRP self-resistance heating pipe, does not change the basic path of "carbon fiber beam power heating-CFRP heat transfer-outer layer insulation", and only adds graphite film with fast in-plane diffusion between heating beams. The graphite film has fast in-plane heat conduction and slow thickness heat conduction, which can effectively suppress heat energy in the inner wall neighborhood with the cooperation of the outer layer insulation, realizing the uniformization of the pipeline temperature field.

[0050] To describe the in-plane heat conduction process of the "carbon fiber heating beam-graphite film-carbon fiber heating beam" unit, the area where the graphite film is located is denoted as Ω, and the local plane coordinates (x, y) are taken, where x is the projection direction of the connecting line of the two heating beams, and y is the vertical direction; if the graphite film and the heating beam form an angle θ, then the arc length along the heating beam direction is s, then the in-plane steady-state heat conduction model in the unit:

[0051] Where,

[0052]

[0053]

[0054] The carbon fiber bundle inputs heat to the graphite film on the overlap edge with the graphite film. The heating bundle direction is denoted by arc length s, and the boundary heat flux density corresponding to different s positions on the same heating bundle is different, which can be written as:

[0055] Wherein,

[0056]

[0057]

[0058]

[0059] Wherein,

[0060] Wherein,

[0061]

[0062]

[0063]

[0064] The graphite film is allowed to be laid at an angle θ relative to the two parallel heating bundles, and at this time the heat propagates obliquely along the main direction of the graphite film. The center distance of the two heating bundles is S, and the equivalent heat bridge span in the "bundle connection direction" is:

[0065] It represents the distance between the projection of one bundle to the projection of the other bundle, which is the distance that the graphite film really plays a role in "lateral temperature equalization".

[0066] The corresponding in-plane heat transfer path length is:

[0067] Therefore, the greater θ is, the longer the path is, and the heat transfer loss also increases accordingly.

[0068] Because of the non-uniformity along the bundle direction, the center temperature difference is calculated by the average temperature along the bundle direction:

[0069] In order to describe "whether the middle of the graphite film is lifted up" and "whether the inter-beam cold zone is flattened", the present application defines the difference between the temperature at the center line of the unit and the average temperature at the projection of the two side heating beams as the center temperature difference ΔT:

[0070] wherein,

[0071]

[0072]

[0073] In order to facilitate comparison of different working conditions, it is written in a normalized form:

[0074] wherein,

[0075] From the above relationship, it can be seen that the center temperature difference ΔT defined by the present application is not determined by a single factor, but is coupled by the graphite width W (determining the effective contact area with the heating beam), the effective heat transfer distance L along the film (determining the geometric length that the heat needs to cross in the plane), and the angle θ between the graphite film and the carbon fiber heating beam (the in-plane thermal conductivity k of the graphite film and the heat flux q''(W, I) are jointly coupled and controlled. By selecting the above variables and substituting them into the typical working condition parameters for solving, the inter-beam low temperature zone can be lifted up and the temperature field of the inner wall of the pipeline can be homogenized without improving the overall energy supply.

[0076] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the above embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A CFRP oil pipeline inner wall temperature field homogenization graphite film laying method for deep-sea thick oil recovery, characterized in that, It comprises the following steps: The graphite film is pasted between adjacent carbon fiber heating beams of the CFRP pipeline to serve as a heat transfer medium between the beams, direct heat flow to the low-temperature area between the beams, and inhibit radial heat loss; The relative angle between the graphite film and the heating beam, the width of the graphite film, and the effective heat transfer length along the film are determined to form a parameter combination, which is determined by quantifying the heat convergence effect and heat loss inhibition degree to ensure uniform heat distribution in the unit; The pipeline is divided into different zones based on the external heat exchange conditions of different sections along the axial direction of the pipeline, and different parameter combinations are matched for each zone. Meanwhile, independent power supply control is implemented for each zone to adjust the heating power to adapt to the heat exchange demand of each zone; The difference between the temperature at the center line of the minimum repeating unit and the average temperature at the projection of the two heating beams is taken as the center temperature difference. The temperature field uniformity is evaluated by normalizing the center temperature difference to ensure that the temperature field of the inner wall of the oil pipeline meets the preset uniformity requirement.

2. The method of claim 1, wherein, The relative angle between the graphite film and the heating beam includes oblique intersection and approximate orthogonality. The oblique intersection angle is set to prioritize improving the temperature of the low-temperature area between the beams, and the approximate orthogonal angle is set to prioritize diffusing the local high temperature near the heating beam and preventing overheating of the material.

3. The method of claim 1, wherein, The width of the graphite film and the effective heat transfer length along the film are determined according to the spacing between the heating beams to ensure that the graphite film and the carbon fiber heating beam have sufficient contact area to obtain heat, while avoiding excessive heat diffusion to non-target areas, balancing the temperature field uniformization effect and overall energy consumption.

4. The method of claim 1, wherein, The normalized center temperature difference refers to taking the ratio of the center temperature difference to the average temperature at the projection of the two heating beams as the evaluation index. This index eliminates the influence of absolute temperature difference on uniformity judgment, achieving unified evaluation of temperature field uniformity under different working conditions.

5. The method of claim 1, wherein, The independent power supply control refers to matching different heating power adjustment strategies based on the parameter combination of each zone to compensate for the heat exchange difference of each zone and further optimize the temperature field uniformity of each zone.

6. The method of claim 1, wherein, The minimum repeating unit is arrayed along the circumferential and axial directions of the CFRP oil pipeline to form a continuous in-plane heat conduction network, allowing adjacent repeating units to compensate for heat, and avoiding local temperature imbalance.

7. The method of claim 1, wherein, The in-plane high thermal conductivity of the graphite film is used to guide heat to the low-temperature area between the beams, and the low thermal conductivity in the thickness direction is used to reduce heat loss to the outside of the oil pipeline, achieving temperature field uniformization and heat loss inhibition through the cooperation of the two characteristics.

8. The method of claim 1, wherein, It also includes a verification step for the uniformity of the temperature field of the inner wall of the CFRP oil pipeline: monitoring the circumferential temperature distribution of the inner wall of the oil pipeline, calculating the maximum circumferential temperature difference, and ensuring that the maximum circumferential temperature difference and the normalized center temperature difference both meet the preset threshold to determine whether the temperature field uniformization meets the standard.

9. Use of the method according to any one of claims 1 to 8, characterized in that The deep-sea heavy oil recovery CFRP oil pipeline based on the above method comprises a high-thermal-conductivity impermeable coating, carbon fiber heating beams, a graphite film, and a carbon fiber winding pressure-resistant layer arranged in sequence; the graphite film is pasted between adjacent carbon fiber heating beams to form a repeating structure of "heating beam-graphite film-heating beam", and the pipeline is provided with a segmented independent power supply circuit along the axial direction to adapt to the power supply control requirements of each zone.

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