Twisted-Baffle Heat Transfer Tube for Low-Pressure Cracking Furnaces
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Solution Overview
Problem
Cracking furnaces in the petrochemical industry face inefficiencies in heat transfer due to the formation of coke on inner surfaces, which reduces the effectiveness of ribs and fins used to thin the boundary layer, leading to decreased heat transfer coefficients and increased thermal resistance.
Innovation Solution
A heat transfer tube with a twisted baffle arranged spirally along its inner wall, featuring a non-through gap extending along the axial direction, which converts fluid flow into a rotating flow, destroying the boundary layer and reducing fluid resistance, while the baffle's design and holes enhance turbulence and stability, preventing coke formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ribs or fins are provided on the inner surface of the furnace pipe to reduce boundary layer thickness, then heat transfer efficiency is improved, but coke deposition on the inner surface weakens the effectiveness of these structures over time
Solution Approach 1:
Instead of adding complex internal structures (ribs/fins) that get covered by coke, the invention uses a smooth inner surface tube combined with external spiral ribs. This inverts the approach by placing the heat transfer enhancement structure on the outer surface where it remains exposed to hot gases rather than being covered by internal coke deposition, thereby maintaining effectiveness throughout service life.
Solution Approach 2:
The invention transitions the heat transfer enhancement from the internal dimension (where coke blocks access to ribs/fins) to the external dimension by adding spiral ribs on the outer surface of the tube. This dimensional shift allows the enhancement structure to remain accessible to hot gases while the inner surface stays smooth and coke-resistant.
2Stability of the object's composition
If a twisted baffle is provided without gaps to maximize structural stability, then baffle stability is improved, but fluid resistance and pressure loss increase
Solution Approach 1:
The twisted baffle is segmented by introducing gaps that divide it into multiple sections along its length. These gaps allow fluid to pass through, reducing resistance and pressure loss while the baffle segments maintain stability through their connection to the tube wall and mutual support.
Solution Approach 2:
The baffle has non-uniform local properties with gaps strategically positioned to optimize fluid flow paths. The gaps create local openings that reduce resistance while the solid portions maintain structural stability, achieving a balance between these conflicting requirements through spatially varying structure.
3Reliability
If the twist angle of the twisted baffle is increased to enhance rotating flow and heat transfer, then heat transfer efficiency is improved, but pressure drop of the fluid increases
Solution Approach 1:
The gaps in the twisted baffle allow partial fluid passage, meaning not all fluid is forced into the high-rotation path. This partial action reduces the energy penalty while still achieving sufficient turbulence and heat transfer enhancement for the majority of the fluid flow.
Solution Approach 2:
The gap geometry (size, position, distribution) is optimized to change the flow parameters, allowing a higher twist angle to be used for heat transfer enhancement while the gaps compensate by providing lower-resistance flow paths, thus balancing heat transfer improvement against pressure drop increase.
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 twisted baffle design improves heat transfer efficiency by increasing tangential fluid speed, reducing pressure loss, and minimizing coke deposition, achieving a better heat transfer effect while maintaining stable operation and reducing fluid resistance.
Implementation Method 1
A tangential speed of the fluid destroys the boundary layer so as to achieve the purpose of enhancing heat transfer
Implementation Method 2
the arrangement of the gap reduces the resistance of fluid in the heat transfer tube
Implementation Method 3
the heat transferred per unit area q/A is to improve the value of the heat transfer coefficient k
Implementation Method 4
fluid can flow along the twisted baffle and turns into a rotating flow
Data Source
AI summary
A heat transfer tube includes a twisted baffle arranged in an inner wall of the tube. The twisted baffle extends spirally along an axial direction of the heat transfer tube. The twisted baffle is provided with a non-through gap extending along an axial direction of the heat transfer tube from an end to the other end of the twisted baffle. A cracking furnace uses the heat transfer tube. The heat transfer tube and cracking furnace have good heat transfer effects and small pressure loss.