LNG intermediate medium gasifier and heat exchange tube thereof

Abstract

The utility model provides a LNG intermediate medium gasifier and heat exchange pipe thereof, heat exchange pipe includes pipeline main part, fin component and composite coating, pipeline main part has a plurality of periodic arrangement's variable cross section flow channel unit, and variable cross section flow channel unit includes contraction section and expansion section, fin component has along the axial interval arrangement many groups, and each group fin component includes a plurality of circumferential uniform distribution's fin unit, and each fin unit includes along the radial extension's main rib and the one level branch rib of outwardly inclined extension of symmetric setting in main rib both sides, composite coating is located in the inner wall of pipeline main part, and it includes titanium nitride base layer and graphene nanometer layer, the utility model discloses the combination design through variable cross section flow channel unit and fin component, forms the collaborative heat transfer system of'pipe inside turbulence intensification + pipe outside film condensation optimization', effectively improves the heat exchange efficiency of gasifier, gas -liquid separation effect and dynamic condition's adaptability, through setting up composite coating in the inner wall of pipe, prolongs the service life of pipe material.

Description

Technical Field

[0001] This utility model belongs to the field of vaporizer technology, specifically relating to an LNG intermediate medium vaporizer and its heat exchange tube. Background Technology

[0002] In recent years, green and low-carbon LNG (liquefied natural gas) cold energy utilization technology has received widespread attention. LNG cold energy power generation, as an important way to efficiently recover cryogenic energy, has become a key technological development direction in the LNG industry chain. Improving the heat transfer efficiency of LNG gasification equipment and optimizing the thermal efficiency of cold energy power generation systems are core issues for improving the utilization rate of LNG cold energy.

[0003] Intermediate medium vaporizers (IFVs), due to their unique heat transfer and structural advantages, can effectively avoid problems such as seawater freezing and ensure stable operation of the equipment under extreme low-temperature conditions, making them a key core piece of equipment in LNG receiving terminals. The performance of the IFV directly affects the efficiency of LNG cold energy utilization, and the condenser (LNG vaporization section), as the core heat exchange component of the IFV, undertakes the dual functions of LNG cryogenic vaporization and intermediate medium condensation and reflux. Its heat transfer efficiency, gas-liquid separation capability, and structural reliability directly determine the overall performance of the system.

[0004] However, existing IFV condensers have the following problems: First, the heat exchange tubes are mostly straight tubes or smooth tube bundles. Due to the simple flow channel structure, it is difficult to effectively induce gas-liquid two-phase turbulence, resulting in a low heat transfer coefficient. In addition, the fixed cross-section flow channel is prone to uneven velocity distribution during phase change, causing a surge in local pressure drop and further deteriorating the heat exchange efficiency. Second, the high liquid content of the gasified natural gas not only increases the load on the temperature regulation section but also poses a safety hazard of liquid slugging. Third, the existing pipe materials have insufficient resistance to embrittlement under cryogenic conditions of -196℃, resulting in a generally shorter equipment lifespan of less than 10 years and high maintenance costs. Furthermore, the traditional structure has weak dynamic response capability to LNG flow fluctuations and composition changes, leading to decreased operating efficiency and insufficient system stability.

[0005] The above background information is provided only to aid in understanding the concept and technical solution of this application. It does not necessarily belong to the prior art of this application, nor does it necessarily provide technical guidance. In the absence of clear evidence that the above information was disclosed before the filing date of this application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Utility Model Content

[0006] The purpose of this invention is to provide a novel LNG intermediate medium vaporizer and its heat exchange tube. The heat exchange tube adopts a combination design of variable cross-section flow channel unit and fin assembly to form a synergistic heat transfer system of "in-tube turbulence enhancement + external tube film condensation optimization". Furthermore, a composite coating is sprayed on the inner wall of the tube, which effectively improves the heat exchange efficiency of the vaporizer, enhances the gas-liquid separation effect, the service life of the tube, and the adaptability to dynamic operating conditions.

[0007] To achieve the above objectives, the technical solution adopted by this utility model is as follows: This utility model provides a heat exchange tube for an LNG intermediate medium vaporizer, comprising: The main body of the pipe has multiple periodically arranged variable cross-section flow channel units, which are connected sequentially along the fluid flow direction. Each variable cross-section flow channel unit includes a contraction section and an expansion section. The inner diameter of the contraction section gradually decreases along the fluid flow direction, and the inner diameter of the expansion section gradually increases along the fluid flow direction. A rib assembly having multiple sets spaced apart along the axial direction of the pipe body, each set of rib assemblies including multiple rib units evenly arranged circumferentially around the pipe body, each rib unit including a main rib extending radially along the pipe body and primary branch ribs symmetrically arranged on both sides of the main rib and extending outwardly, the primary branch ribs having multiple spaced-apart ribs arranged on the main rib; and, A composite coating is disposed on the inner wall of the pipe body, the composite coating comprising a titanium nitride substrate layer and a graphene nanolayer.

[0008] In some embodiments, the angle between the primary branch rib and the main rib is 45° to 60°, such as 45°, 50°, 55°, 60° or any value within the above range.

[0009] In some embodiments, the primary branch ribs extend radially from the inside out in a gradually expanding manner, and their length increases with the increase of the radial distance.

[0010] In some implementations, the distance between two adjacent primary branch ribs gradually increases radially from the inside out.

[0011] In some embodiments, the outermost primary branch rib is connected to a secondary branch rib, which has two symmetrically arranged secondary branch ribs that extend obliquely outward. Preferably, the angle between the secondary branch rib and the primary branch rib is 30° to 60°, and more preferably 45° to 60°.

[0012] In some embodiments, the cone angle of the contraction section is greater than the cone angle of the expansion section. Further, the cone angle of the contraction section is 15° to 25°, and the cone angle of the expansion section is 8° to 12°.

[0013] In some embodiments, the length of the contraction section is less than the length of the expansion section. Further, the length of the contraction section is defined as L1, and the nominal diameter of the heat exchange tube is defined as D, satisfying the following relationship: L1 = 5D ~ 10D. The length of the expansion section is defined as L2, and the nominal diameter of the heat exchange tube is defined as D, satisfying the following relationship: L2 = 8D ~ 12D.

[0014] In some embodiments, the variable cross-section flow channel unit further includes a straight section disposed between the contraction section and the expansion section.

[0015] In some implementations, the cone angles of the contraction or expansion sections of different variable cross-section flow channel units may be the same or different, and their lengths may be equal or unequal.

[0016] In some embodiments, the heat exchange tube is a U-shaped tube.

[0017] This utility model also provides an LNG intermediate medium vaporizer, wherein the heat exchange tube of the condensation section (condenser, i.e., LNG vaporization section) of the LNG intermediate medium vaporizer is the heat exchange tube as described above.

[0018] Due to the application of the above technical solution, this utility model has the following advantages compared with the prior art: This invention enhances fluid turbulence and improves gas-liquid separation through a variable cross-section flow channel design. The variable cross-section flow channel employs a contraction-expansion structure. When LNG flows through this structure, the flow velocity increases in the contraction section, while a backflow vortex is formed in the expansion section. This design strengthens the turbulence effect of the gas and liquid phases, improving heat exchange efficiency. As the flow channel cross-section changes, lighter gases are rapidly discharged upwards due to the velocity difference, while heavier liquids are effectively guided downwards, thereby improving gas-liquid separation efficiency. Furthermore, this design effectively reduces the load in the temperature control zone and the risk of liquid slugging, minimizes flow dead zones or bubble retention areas that may form in traditional fixed cross-section flow channels, and avoids material fatigue or weld cracking caused by excessive temperature differences.

[0019] This invention also enhances heat transfer and improves adaptability to dynamic operating conditions by employing a specially structured fin assembly. Specifically, the hierarchical distribution design of main fins and branch fins significantly increases the heat exchange area compared to traditional straight fins, adjusting local heat transfer intensity during flow fluctuations and avoiding efficiency imbalances in a single structure at high and low flow velocities. Furthermore, the hierarchical branching structure of the fin assembly induces multi-stage disturbances of "flow splitting-impact-vortex," disrupting the condensate film boundary layer and further improving heat transfer efficiency. The inclined design of the branch fins guides condensate to drip rapidly along the ends of the branch fins, effectively reducing liquid accumulation outside the pipe and preventing frost buildup, thereby maintaining efficient heat transfer and improving the long-term stability and safety of the system.

[0020] In addition, this utility model extends the service life of pipe fittings by setting a composite coating inside the pipe. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the LNG intermediate medium vaporizer provided in Example 1; Figure 2 This is a schematic diagram of the rib assembly provided in Example 1; Figure 3 This is a schematic diagram of the structure of the variable cross-section flow channel unit provided in Example 1; Among them, 1. Pipe body; 11. Variable cross-section flow channel unit; 111. Contraction section; 112. Straight section; 113. Expansion section; 12. Rib assembly; 121. Main rib; 122. Primary branch rib; 123. Secondary branch rib; 2. First heat exchange shell; 21. Intermediate medium evaporation zone; 211. Heating material inlet; 212. Intermediate medium evaporation tube bundle; 22. LNG vaporization zone; 221. LNG inlet; 222. LNG pipeline; 3. Second heat exchange shell; 31. Baffle plate; 32. Temperature regulating tube bundle; 33. NG outlet; 34. Heating substance inlet; 35. First tube sheet; 36. Second tube sheet. Detailed Implementation

[0022] The present invention will be further described below with reference to embodiments, but the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0023] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0024] In the description of the embodiments of this utility model, it should be understood that the terms "inner" and "outer," etc., indicate a position or location relationship defined by distance relative to the center of the device or component. "Inner" refers to a position closer to the center of the device or component, and "outer" refers to a position farther from the center of the device or component. These terms are used only for ease of description and simplification of the embodiments of this utility model, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this utility model.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0026] The following disclosure provides many different implementations or examples for different structures of the embodiments of the present invention. To simplify the disclosure of the embodiments of the present invention, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the embodiments of the present invention. Furthermore, reference numerals and / or reference letters may be repeated in different examples of the embodiments of the present invention; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed. Example

[0027] An LNG intermediate medium vaporizer, such as Figure 1 As shown, it includes a first heat exchange shell 2 and a second heat exchange shell 3. The first heat exchange shell 2 forms an LNG vaporization zone 22 (i.e., a condensation section) and an intermediate medium evaporation zone 21, which are located in upper and lower regions and are connected. The intermediate medium evaporation zone 21 is provided with an intermediate medium evaporation tube bundle 212. Its specific structure and connection method with the first heat exchange shell 2 can refer to the prior art and are not specifically limited. The first heat exchange shell 2, where the intermediate medium evaporation zone 21 is located, has an intermediate medium inlet / outlet and a heating substance inlet / outlet (e.g., Figure 1The heating material inlet 211 is shown. The heating material flows through the tubes, the intermediate medium flows through the shell, and the intermediate medium evaporation tube bundle 212 is preferably completely immersed in the liquid intermediate medium. As an example, the intermediate medium can be propane or other intermediate media commonly used in the art, and the heating material can be seawater or other heating materials commonly used in the art. A heat exchange tube is provided within the LNG vaporization zone 22, and an LNG inlet 221 and an outlet are provided on the first heat exchange shell 2 where the LNG vaporization zone 22 is located. LNG flows through the tubes, is heated and vaporized in the heat exchange tubes, and is discharged through the outlet. A temperature-regulating tube bundle 32 is provided within the second heat exchange shell 3, and both ends of the temperature-regulating tube bundle 32 are fixed by a first tube sheet 35 and a second tube sheet 36, respectively. Its specific structure can refer to existing technology in the art and is not specifically limited. An NG inlet and NG outlet 33, and a heating material inlet 34 and an outlet are provided on the second heat exchange shell 3. In this design, the heating material flows through the tubes, while NG flows through the shell. The NG inlet is connected to the outlet of the LNG vaporization zone 22 via NG pipe 222, used to introduce NG into the second heat exchange shell 3. The heating material is as described above and will not be repeated here. Preferably, the second heat exchange shell 3 is also provided with baffles 31 that are staggered vertically along the length of the first heat exchange shell 2 and arranged on the temperature-regulating tube bundle 32. The specific structure of the LNG intermediate medium vaporizer can also adopt conventional technical solutions in the art. The heat exchange tubes in the LNG vaporization zone 22 are described in detail below.

[0028] The heat exchange tubes are preferably U-shaped, and their number can be determined according to actual design requirements; there can be one or multiple tubes. The heat exchange tubes include a tube body 1, a fin assembly 12, and a composite coating (not shown in the figure). The tube body 1 has multiple periodically arranged variable cross-section flow channel units 11, which are connected sequentially along the fluid flow direction. Each variable cross-section flow channel unit 11 includes a contraction section 111 and an expansion section 113. For example... Figure 3 As shown, the inner diameter of the contraction section 111 gradually decreases along the fluid flow direction, and the inner diameter of the expansion section 113 gradually increases along the fluid flow direction. The rib assembly 12 has multiple sets arranged at intervals along the axial direction of the pipe body 1. Each set of rib assemblies 12 includes multiple rib units evenly arranged circumferentially around the pipe body 1, preferably 4 to 8 rib units. Figure 2 As shown, each rib unit includes a main rib 121 extending radially along the pipe body 1 and primary branch ribs 122 symmetrically arranged on both sides of the main rib 121 and extending outward at an angle. The primary branch ribs 122 have multiple spaced-apart ribs, preferably 2 to 5. A composite coating is provided on the inner wall of the pipe body 1, which includes a titanium nitride (TiN) substrate layer and a graphene nanolayer.

[0029] When a heated substance (such as seawater) flows into the intermediate medium evaporation tube bundle 212 (tube side), it releases heat. At this time, the liquid intermediate medium (such as propane) on the outer wall of the intermediate medium evaporation tube bundle 212 is heated and evaporated, becoming a gaseous intermediate medium, and carrying a large amount of latent heat of vaporization, it rises to the LNG vaporization zone 22.

[0030] Within the LNG vaporization zone 22, cryogenic LNG is introduced into the heat exchange tubes. When the vaporized intermediate medium encounters the cryogenic heat exchange tubes, it undergoes film condensation on the tube surface, turning into a liquid and releasing its latent heat of vaporization. This heats the LNG inside the tubes, promoting its vaporization. During this process, the variable cross-section flow channel unit 11 of the heat exchange tubes enhances the turbulence of the gas-liquid two-phase fluid through a periodic contraction-expansion structure (the contraction section 111 accelerates, and the expansion section 113 forms a reflux vortex), improving heat transfer efficiency, promoting gas-liquid separation, and reducing the risk of liquid hammer in the subsequent temperature control zone. Simultaneously, when the intermediate medium vapor flows through the fin assembly 12 outside the tubes, the branch fins divide the vapor into multiple small channels, breaking the uniform flow pattern and increasing the contact area between the vapor and the fin surface. Under the guidance of the branch fins, the split vapor flow collides with adjacent fins or the main fin 121, preventing liquid film accumulation and the formation of a thermal resistance layer. The arrangement of the branch ribs, combined with the abrupt change in flow direction after impact, induces boundary layer separation, forming local eddies. This enhances the turbulent mixing of vapor and the pipe wall, accelerates heat transfer, and efficiently transfers the latent heat of condensation of the intermediate medium vapor to the LNG. The inclined design of the branch ribs guides the condensed liquid intermediate medium to drip rapidly along the branch ribs, effectively reducing liquid accumulation outside the pipe and preventing liquid buildup and frost blockage. The liquid intermediate medium flows back to the bottom liquid pool, forming an "evaporation-condensation" self-circulating system.

[0031] After being heated and vaporized, LNG enters the second heat exchange shell 3 through NG pipeline 222, and is then guided by baffle 31 to exchange heat with temperature control tube bundle 32, thereby further heating it to the target temperature to meet the pipeline transportation requirements (usually above 0°C to prevent pipeline icing).

[0032] Furthermore, the composite coating on the inner wall of the pipeline body 1 significantly improves the corrosion resistance and service life of the equipment in extreme environments by blocking chloride ion penetration and resisting low-temperature shocks of -196°C. This composite coating also reduces the formation of biofouling and maintains high heat transfer efficiency. As an example, the composite coating can be formed layer by layer on the inner wall of the pipeline body 1 using magnetron sputtering technology. The TiN substrate layer and graphene nanolayer can optionally be one or more layers; when multiple layers are present, they are stacked alternately with the TiN substrate layer and graphene nanolayer. To improve the overall service life of the LNG intermediate medium vaporizer, the inner walls of the first heat exchange shell 2, the second heat exchange shell 3, the intermediate medium evaporation tube bundle 212, and the temperature regulating tube bundle 32 are selectively coated with the composite coating.

[0033] In this embodiment, the angle r between the primary branch rib 122 and the main rib 121 is 45°~60°, which better guides the condensate to drip rapidly along the branch rib, reduces liquid accumulation outside the pipe, prevents liquid buildup and frost blockage, thereby maintaining efficient heat transfer and improving the stability and safety of the system in long-term operation. The primary branch rib 122 extends radially from the inside out, and its length increases with the increase of the radial distance, further increasing the heat exchange area. The distance between two adjacent primary branch ribs 122 gradually increases radially from the inside out. Preferably, the end of the outermost primary branch rib 122 is connected to a secondary branch rib 123. The secondary branch rib 123 has two symmetrically arranged secondary branch ribs that extend obliquely outward, and the angle between them and the primary branch rib 122 is 30°~60°. The design of the secondary branch rib 123 further increases the heat exchange area and promotes the separation of the gas and liquid phases.

[0034] In this embodiment, the cone angle α of the contraction section 111 is greater than the cone angle β of the expansion section 113, and the length L1 of the contraction section 111 is less than the length L2 of the expansion section 113. Furthermore, the cone angles of the contraction section 111 or the expansion section 113 of different variable cross-section flow channel units 11 may be the same or different, and their lengths may be equal or unequal. The design of a larger cone angle and shorter length for the contraction section 111 can accelerate fluid flow. When the fluid passes through the contraction section 111, the flow velocity increases, and the turbulence intensity is significantly enhanced, thereby breaking the laminar boundary layer and increasing the contact area between the fluid and the pipe wall and the heat transfer efficiency. Conversely, the design of a smaller cone angle and longer length for the expansion section 113 can form a stable backflow vortex in the expansion section 113, thereby further enhancing the turbulent mixing of the fluid and making heat transfer more uniform and efficient. Preferably, the cone angle α of the contraction section 111 is 15°~25°, and the cone angle β of the expansion section 113 is 8°~12°. The nominal diameter of the heat exchange tube is defined as D, and the length of the contraction section 111 is defined as L1, which satisfies the following relationship: L1 = 5D ~ 10D. The length of the expansion section 113 is defined as L2, which satisfies the following relationship: L2 = 8D ~ 12D.

[0035] Furthermore, a straight section 112 connects the contraction section 111 and the expansion section 113. The straight section 112 can act as a buffer to prevent the fluid from directly impacting the contraction section 111 and the expansion section 113, thereby reducing flow resistance and structural stress.

[0036] The present utility model has been described in detail above, with the aim of enabling those skilled in the art to understand its contents and implement it. However, this description should not be construed as limiting the scope of protection of the present utility model. All equivalent changes or modifications made in accordance with the spirit and essence of the present utility model should be included within the scope of protection of the present utility model.

Claims

1. A heat exchange tube for an LNG intermediate medium gasifier, characterized in that, include: The main body of the pipe (1) has a plurality of periodically arranged variable cross-section flow channel units (11), which are connected in sequence along the fluid flow direction. Each variable cross-section flow channel unit (11) includes a contraction section (111) and an expansion section (113). The inner diameter of the contraction section (111) gradually decreases along the fluid flow direction, and the inner diameter of the expansion section (113) gradually increases along the fluid flow direction. A rib assembly (12) having multiple sets spaced apart along the axial direction of the pipe body (1), each rib assembly (12) including multiple rib units uniformly arranged circumferentially around the pipe body (1), each rib unit including a main rib (121) extending radially along the pipe body (1) and primary branch ribs (122) symmetrically arranged on both sides of the main rib (121) and extending outwardly, the primary branch ribs (122) having multiple spaced-apart ribs on the main rib (121); and, The composite coating, which is disposed on the inner wall of the pipe body (1), includes a titanium nitride substrate and a graphene nanolayer.

2. The LNG intermediate medium gasifier heat exchange tube of claim 1, wherein, The angle between the primary branch rib (122) and the main rib (121) is 45°~60°.

3. The LNG intermediate medium gasifier heat exchange tube of claim 1, wherein, The primary branch rib (122) extends radially from the inside out in a gradually expanding manner, and its length increases with the increase of the radial distance.

4. The LNG intermediate medium gasifier heat exchange tube of claim 1, wherein, The distance between two adjacent first-order branch ribs (122) gradually increases radially from the inside out.

5. The LNG intermediate medium gasifier heat exchange tube of claim 1, wherein, The end of the primary branch rib (122) located at the outermost end is connected to a secondary branch rib (123), which has two symmetrically arranged secondary branch ribs that extend outward at an inclined angle.

6. The LNG intermediate medium gasifier heat exchange tube of claim 1, wherein, The cone angle of the contraction section (111) is greater than the cone angle of the expansion section (113); And / or, the length of the contraction segment (111) is less than the length of the expansion segment (113).

7. The LNG intermediate medium gasifier heat exchange tube of claim 6, wherein, The cone angle of the contraction section (111) is 15°~25°; And / or, the cone angle of the expansion segment (113) is 8°~12°; And / or, the length of the contraction section (111) is defined as L1, and the nominal diameter of the heat exchange tube is defined as D, and the two satisfy the following relationship: L1 = 5D ~ 10D; And / or, the length of the expansion section (113) is defined as L2, and the nominal diameter of the heat exchange tube is defined as D, and the two satisfy the following relationship: L2 = 8D ~ 12D.

8. The LNG intermediate medium gasifier heat exchange tube of any one of claims 1, 6, 7, wherein, The variable cross-section flow channel unit (11) also includes a straight section (112) located between the contraction section (111) and the expansion section (113).

9. The LNG intermediate medium gasifier heat exchange tube of claim 1, wherein, The heat exchange tube is a U-shaped tube.

10. An LNG intermediate medium vaporizer, characterized in that, The heat exchange tube of the condensation section of the LNG intermediate medium vaporizer is the heat exchange tube as described in any one of claims 1 to 9.

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