U-Shaped Connection for Double-Pipe Heat Exchanger Thermal Stress
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Solution Overview
Problem
The connection between cooled and uncooled pipes in double-pipe heat exchangers faces issues with thermal stress, coke formation, and efficiency due to complex designs and irregularities, leading to mechanical integrity and performance problems at high temperatures.
Innovation Solution
A U-shaped connection with a transverse bottom wall and a metallized weld, avoiding the use of transition cones, maintains low material temperatures, prevents coke formation, and ensures efficient fluid flow by maintaining a constant cross-sectional duct, using materials within elastic limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a forked connection with transition cone is used to reduce thermal stress, then the connection durability is improved, but the device complexity increases
Solution Approach 1:
The invention removes the transition cone and refractory ring components from the system. By using a U-shaped connection where the shanks are directly welded to the pipes, the complex supplementary structures are extracted and eliminated, simplifying the design while maintaining thermal stress resistance through the U-shape geometry itself
Solution Approach 2:
Instead of adding complex components (cone, refractory ring) to protect the fork connection, the invention inverts the approach by making the connection itself U-shaped. This geometric inversion allows the connection to naturally accommodate thermal expansion and stress without requiring additional protective structures
2Temperature
If transition cone and refractory ring are inserted to distribute temperature, then the connection thermal stress is reduced, but the gas flow regularity deteriorates
Solution Approach 1:
The invention extracts and removes the transition cone and refractory ring components that were causing flow irregularities. By eliminating these protruding structures from the gas flow path, the duct maintains constant cross-section throughout, preventing coke formation while the U-shaped connection still provides adequate thermal stress management
Solution Approach 2:
The U-shaped connection concentrates the thermal management function locally at the connection point through its geometry, rather than requiring extended transition zones. The shanks welded to the pipes create a localized solution that doesn't interfere with the overall gas flow regularity in the duct
3Difficulty of detecting and measuring
If floating sleeve is added to absorb differential dilation, then the thermal expansion is compensated, but the mechanical integrity deteriorates due to coke obstruction
Solution Approach 1:
The invention removes the floating sleeve component entirely. The U-shaped connection with welded shanks provides a rigid, coke-resistant structure that eliminates the need for the sleeve's differential expansion compensation mechanism, avoiding the mechanical integrity problems caused by coke obstruction
Solution Approach 2:
The U-shape geometry provides inherent flexibility to accommodate thermal expansion through its curved form, replacing the need for the floating sleeve's mechanical expansion compensation. The curvature allows the structure to flex with thermal changes without creating narrow spaces where coke can accumulate and cause failure
4Temperature
If extended geometry with transition cone is used, then the thermal stress is distributed, but the gas residence time increases reducing efficiency
Solution Approach 1:
The invention extracts and eliminates the transition cone that extended the geometry. By removing this unnecessary component, the gas residence time in the exchanger is reduced, improving productivity while the U-shaped connection maintains adequate thermal stress distribution through its compact welded structure
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 a durable, efficient, and cost-effective connection that minimizes thermal stress, prevents coke formation, and maintains high exchanger efficiency by keeping all materials within their elastic limits, allowing for adaptation of existing designs.
Implementation Method 1
the double-wall pipe comprises an internal pipe traveled by the fluid to be cooled (for example, cracking gas coming out of an oven) and an external pipe delimiting with the internal one the airspace traveled by the cooling fluid
Data Source
Figure 1
AI summary
A union connection between uncooled pipe and cooled double-wall pipe in a heat exchanger comprising a double-wall pipe (12) comprising in turn an internal pipe (15) traveled by a fluid to be cooled and an external pipe (14) defining with the internal pipe an air space (19) traveled by a cooling fluid with one end of the double-wall pipe (12) being connected to an inlet duct (30) of the fluid to be cooled through a connection part (16) also forming a bottom wall (18) of the air space virtually transversal to the double-wall pipe extension and characterized in that the connection part (16) has an annular form with U cross section to define two annular shanks (20, 21) extending longitudinally to the pipe (12) with each shank being welded to one end of one of the two pipes (14, 15) of the double-wall pipe (12) and in that the end (22) of the inlet duct (30) is welded to the connection part at said bottom wall (18) of the air space.