Steam Generator Tube Helical Wire Insert Heat Transfer
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Solution Overview
Problem
Conventional steam generator tubes face challenges in heat transfer due to boiling crises at subcritical pressures, leading to inadequate cooling and reduced strength, especially with high-temperature steels, and are costly and difficult to manufacture with desired rib profiles, while existing swirl-generating internals cause pressure losses and uneven cooling.
Innovation Solution
A steam generator tube with a twist-generating inner profile formed by helically wound wires, which improves heat transfer by ensuring even wetting of the inner wall without blocking the pipe cross-section, allowing for flexible design and production, and maintaining swirl over long flow paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deformation process (cold drawing) is used to create helically wound ribs, then heat transfer behavior is improved, but manufacturing cost increases and material formability is severely restricted
Solution Approach 1:
The insert is divided into multiple discrete wire elements (typically 3-12 wires) that are wound helically around the tube interior. This segmentation allows each wire to be independently positioned and adjusted, creating the desired swirl effect without requiring deformation of the entire tube. The segmented structure enables use with high-temperature steels that have poor formability, as the wires can be inserted and secured without extensive plastic deformation of the tube material.
Solution Approach 2:
The insert acts as an intermediary element between the tube wall and the flowing medium. Rather than deforming the tube itself to create ribs, the insert provides the swirl-generating surface features. This intermediary approach allows the tube material to remain intact and suitable for high-temperature applications while still achieving improved heat transfer through the insert's helical wire structure.
2Reliability
If twisted tapes are used as swirl-generating internals, then heat transfer is enhanced, but pressure losses increase and flow is excessively deflected
Solution Approach 1:
The helical wires are curved in a smooth, continuous helical pattern that guides the flow along the tube wall without sharp deflections. This curved geometry generates the necessary centrifugal forces to wet the tube wall while maintaining smoother flow paths compared to twisted tapes. The gradual curvature of the helical wires reduces flow separation and minimizes pressure losses while still achieving effective swirl for heat transfer enhancement.
Solution Approach 2:
The helical wires are positioned to contact or closely approach the tube wall at specific locations, creating localized swirl effects where needed. The wires can be spaced and sized to provide appropriate local flow control without excessively deflecting the entire flow. This local quality approach allows for optimized heat transfer at the tube wall while maintaining acceptable pressure losses in the bulk flow.
3Temperature
If high chromium content steels are used for high-temperature applications, then steam generator efficiency is improved, but rib profile production becomes difficult or impossible
Solution Approach 1:
The insert serves as an intermediary that provides the rib profile function without requiring deformation of the high-chromium steel tube. The wires can be made from materials with different formability characteristics, allowing the tube material to be optimized for high-temperature service while the insert provides the necessary flow control features.
Solution Approach 2:
The invention changes the manufacturing approach from plastic deformation (cold drawing) to mechanical assembly (insertion and securing of wires). This parameter change in the manufacturing process allows high-chromium steels to be used, as the insert can be installed using methods such as expansion, friction fitting, or minimal deformation techniques that do not compromise the tube material's high-temperature properties.
4Reliability
If steep flank angles and sharp-edged transitions are required for aerodynamic advantage, then heat transfer is improved, but manufacturing within deformation process becomes difficult
Solution Approach 1:
The insert is segmented into multiple wire elements that can be individually shaped and positioned to create steep flank angles and sharp edges. Each wire can be manufactured with precise geometric features using standard wire drawing and forming processes, then assembled to create the overall helical structure. This segmentation makes it feasible to achieve aerodynamically advantageous profiles that would be difficult to produce through tube deformation.
Solution Approach 2:
Instead of deforming the tube to create ribs, the invention uses separate wire elements that are copied or replicated in a helical pattern around the tube. These wires can be manufactured with precise geometric features (steep flank angles, sharp edges) using standard wire processing techniques, then installed to replicate the desired rib profile effect without deforming the tube itself.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides efficient heat transfer and cooling across various operating conditions with reduced pressure losses and production complexity, enabling flexible design and cost-effective manufacturing, suitable for high-temperature applications.
Implementation Method 1
The shape of the ribs imparts a twist to the medium flowing through the steam generator tube, so that the heavier liquid phase collects on the inner wall of the tube as a result of the centrifugal forces at work and forms a wetting liquid film there.
Implementation Method 2
The insert is designed in such a way that the swirl is maintained over long flow paths
Implementation Method 3
This ensures reliable heat transfer from the inner wall of the tube to the flow medium even with comparatively high heat flow densities and low mass flow densities.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to a steam generator pipe (10) which can be produced in a simple and economical manner and which has particularly good heat transitional behaviour having a large band width with various operational conditions. According to the invention, at least one insert (22) is arranged in the inner chamber of the pipe (18) in order to form a swirl-generating inner profile. The insert (22) comprises a plurality of wires (24) which wind, in a screw-like manner, along on the inner wall of the pipe (26) in the form of a multi-path thread.