Fluid-Mixing Pipe Reducer Layout to Prevent Weld Thermal Fatigue
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Solution Overview
Problem
Piping systems in nuclear and thermal power plants experience thermal fatigue due to variations in temperature interfaces when mixing high-temperature and low-temperature fluids, leading to potential weld failure and reduced lifespan.
Innovation Solution
The design incorporates an inner pipe with a downstream end that extends beyond the weld, ensuring the outer fluid does not backflow and cause temperature fluctuations at the weld, along with features like swirling vanes and a wide portion to enhance mixing and reduce velocity differences, and includes an inner cylinder to split the flow for efficient mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the inner pipe end portion is welded to connect the end portion and downstream portion together, then the structural integrity is improved, but thermal fatigue occurs at the weld due to temperature fluctuations from outer fluid backflow
Solution Approach 1:
The patent applies preliminary action by designing the inner pipe to extend sufficiently beyond the weld location before the fluid mixing region. This pre-positioning ensures that the weld is always protected from direct exposure to temperature fluctuations caused by outer fluid backflow, preventing thermal fatigue before it can occur.
Solution Approach 2:
The extended inner pipe end portion acts as an intermediary protective element between the weld and the temperature fluctuating outer fluid. This intermediate structure shields the weld from direct thermal exposure while still allowing the welding connection to provide structural integrity.
2Productivity
If the inner pipe end portion is positioned closer to the fluid mixing region to enable quicker mixing, then mixing efficiency is improved, but thermal fatigue accelerates due to increased temperature interface variations
Solution Approach 1:
The patent segments the inner pipe into distinct functional zones: a welding connection portion that remains protected from thermal fluctuations, and an extended end portion that reaches into the fluid mixing region to promote efficient mixing. This segmentation allows each zone to fulfill its specific function without compromising the other.
Solution Approach 2:
Different portions of the inner pipe are given different characteristics - the portion near the weld maintains structural integrity while the extended end portion facilitates mixing. The local quality of each segment is optimized for its specific function, with the extended end positioned to maximize mixing efficiency while the weld portion remains protected.
3Reliability
If the inner pipe is made longer to extend beyond the weld, then thermal fatigue is prevented at the weld, but device complexity increases
Solution Approach 1:
The extended inner pipe structure serves multiple functions simultaneously: it provides the welding connection for structural integrity, extends into the fluid mixing region to promote efficient mixing, and protects the weld from thermal fatigue. This multi-functionality eliminates the need for separate protective components.
Solution Approach 2:
The patent merges the protective function against thermal fatigue with the structural welding connection and the mixing promotion function into a single integrated inner pipe structure. This consolidation simplifies the overall design compared to using separate components for each function.
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
This configuration effectively prevents thermal fatigue at welds and bent portions, enhances fluid mixing, and reduces confluence resistance, thereby extending the lifespan and reliability of piping systems.
Implementation Method 1
the outer fluid flows back into the inner pipe
Implementation Method 2
The inner and outer fluids are mixed in the fluid-mixing region downstream of the inner pipe
Implementation Method 3
high-temperature water and low-temperature water must be quickly mixed
Data Source
AI summary
An object is to prevent thermal fatigue, resulting from variations in temperature interfaces, of piping having a fluid-mixing region where fluids of different temperatures are mixed. Piping 1 having a fluid-mixing region M includes a reducer 5 including an end portion 5e disposed substantially on a central axis of a main pipe 2. Low-temperature water flows through the reducer 5 at a lower velocity than high-temperature water flowing outside the end portion 5e. The low-temperature water and the high-temperature water have different temperatures. The low-temperature water and the high-temperature water are mixed in the fluid-mixing region M downstream of the reducer 5. The reducer 5 has a weld line 5f formed to connect the end portion 5e and an elbow portion 5d together. The distance between the weld line 5f and a downstream end 5a is equal to or larger than the inner diameter D of the main pipe 2.