Cracking Furnace Coil Protuberances for Heat Transfer
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Solution Overview
Problem
Current heat transfer technologies in cracking furnaces are inefficient in capturing radiant and convective heat from flames, combustion gases, and furnace walls, leading to high fuel consumption and greenhouse gas emissions, with existing external and internal fin designs not effectively enhancing radiative heat transfer.
Innovation Solution
The external surface of process coils in the radiant section of cracking furnaces is augmented with protuberances having specific geometrical shapes and dimensions, such as tetrahedrons, pyramids, cones, and sections of spheres or ellipsoids, to increase the surface area for enhanced heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional smooth process coils are used in cracking furnaces, then the manufacturing is simple and device complexity is low, but heat transfer efficiency is insufficient leading to high fuel consumption
Solution Approach 1:
The coil external surface is segmented into numerous small protuberances distributed across the surface. Each protuberance acts as an independent heat transfer enhancement element, collectively increasing the effective heat transfer area and improving radiant and convective heat capture from furnace flames and combustion gases.
Solution Approach 2:
The heat transfer surface is transformed from a two-dimensional smooth plane to a three-dimensional textured surface with protuberances. This dimensional transformation increases the effective surface area exposed to radiant and convective heat sources, enhancing heat capture capability without significantly increasing coil volume.
2Use of energy by moving object
If internal fins are added to the coil to improve convective heat transfer, then heat transfer from coil walls to feed is improved, but pressure drop increases and carbon deposits build up on fins
Solution Approach 1:
Instead of modifying the internal surface of the coil (where carbon deposits and pressure drop issues occur), the invention inverts the approach by modifying the external surface with protuberances. This external modification enhances heat capture from the furnace environment without interfering with the internal feed flow or creating surfaces prone to carbon buildup.
3Use of energy by moving object
If existing external fin designs are used to enhance heat transfer, then surface area is increased, but the fins are not effective in capturing radiant heat from flames and furnace walls
Solution Approach 1:
The invention changes the geometric parameters of surface features from conventional fin structures to small protuberances with specific dimensions (height 3-15% of coil outer diameter, base area 0.1%-10% of coil cross-sectional area). These parameter changes optimize the surface features for capturing radiant heat from flames and furnace walls while maintaining manufacturability.
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 protuberances significantly improve net radiant and convective heat capture, reducing fuel consumption and emissions by increasing the absorption of heat from combustion gases and flames, while maintaining or increasing furnace capacity.
Implementation Method 1
The heat transfer within the furnace, between flame, combustion gases, refractory and the process coils is mostly by radiation
Implementation Method 2
The heat transfer within the furnace, between flame, combustion gases, refractory and the process coils is mostly by radiation, and also by forced convection
Implementation Method 3
improving heat transfer within the coil, i.e. from the coil walls into the feed flowing inside the coil
Data Source
Figure 1
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AI summary
The efficiency of heat transfer to a furnace tube or coil in a furnace for cracking ethane, propane or naphtha feedstocks, or a mixture thereof may be improved by providing protuberances on the surface of the tube or coil having i) a maximum height from 3 to 15 % of the coil outer diameter, ii) a contact surface with a coil, or a base, which area is 0.1%-10% of the coil external cross section area, and iii) a geometrical shape which has a relatively large external surface containing a relatively small volume.