Twisted Baffle Heat Transfer Tube for Cracking Furnace
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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 suboptimal heat transfer coefficients.
Innovation Solution
A heat transfer tube with a twisted baffle arranged spirally on its inner wall, featuring holes that alter fluid flow direction and enhance turbulence, along with a casing to support the baffle and improve stability, which transforms fluid flow into a rotating flow to destroy the boundary layer and facilitate coke discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If ribs or fins are provided on the inner surface of the furnace pipe to reduce boundary layer thickness, then heat transfer coefficient is improved, but effectiveness deteriorates as coke accumulates on the inner surface
Solution Approach 1:
The patent employs a twisted baffle that dynamically alters fluid flow patterns rather than relying on static ribs or fins. The baffle creates continuous swirling motion that actively disrupts the boundary layer and prevents coke accumulation, maintaining heat transfer effectiveness over time without degradation from coke buildup.
Solution Approach 2:
The patent converts the harmful effect of coke accumulation into a beneficial outcome by designing the twisted baffle to generate strong swirling flows that not only maintain heat transfer but also actively remove coke deposits. The fluid turbulence created by the baffle prevents coke from adhering to the inner surface, turning the potential harm of coke accumulation into a self-cleaning mechanism.
2Temperature
If a twisted baffle is arranged on the inner wall to transform fluid flow into rotating flow, then heat transfer efficiency is enhanced, but pressure loss increases
Solution Approach 1:
The twisted baffle is strategically positioned and dimensioned to create localized swirling flow only where needed for heat transfer enhancement. The baffle's geometry and placement optimize the balance between generating beneficial turbulence and minimizing excessive pressure drop, applying the swirling effect locally rather than throughout the entire pipe length.
Solution Approach 2:
The patent optimizes parameters such as the baffle's twist angle, width, and spacing to achieve the desired balance between heat transfer enhancement and pressure loss. By carefully adjusting these geometric parameters, the system maximizes boundary layer disruption while minimizing energy consumption, finding the optimal operating point between heat transfer efficiency and pressure drop.
3Temperature
If the boundary layer is thinned to increase heat transfer, then heat transferred per unit area is improved, but fluid flow resistance increases
Solution Approach 1:
The twisted baffle creates dynamic swirling flow that continuously renews the fluid near the wall surface, effectively thinning the boundary layer without creating excessive resistance. The rotational motion prevents the formation of a thick, resistive boundary layer while maintaining manageable pressure drop through optimized baffle geometry.
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 significantly enhances heat transfer efficiency while minimizing pressure loss and coke formation on the inner surfaces, achieving a better balance between heat transfer capacity and pressure drop.
Implementation Method 1
Prandtl's boundary layer theory, when an actual fluid flows along a solid wall, an extremely thin layer of fluid close to the wall surface would be attached to the wall without slippage. That is to say, the speed of the fluid attached to the wall surface, which forms a boundary layer, is zero. Although this boundary layer is very thin, the heat resistance thereof is unusually large.
Implementation Method 2
the twisted baffle is provided with a plurality of holes. Both axial and radial flowing fluids can flow through the holes, i.e., these holes can alter the flow directions of the fluids, so as to enhance turbulence in the heat transfer tube, thus destroying the boundary layer
Implementation Method 3
Fourier's theorem says, wherein q is the heat transferred, A represents the heat transfer area, k stands for the heat transfer coefficient, and dt/dy is the temperature gradient
Data Source
AI summary
The present disclosure relates to a heat transfer tube and a cracking furnace using the heat transfer tube. The heat transfer tube comprises a twisted baffle arranged in an inner wall of the tube, said twisted baffle extending spirally along an axial direction of the heat transfer tube. The twisted baffle defines a closed circle viewed from an end of the heat transfer tube. Along the trajectory of the circle a casing is arranged, which is fixedly connected to a radial inner end of the twisted baffle. The twisted baffle is provided with a plurality of holes. The heat transfer tube according to the present disclosure has a good heat transfer effect and small pressure loss.