Low-Frequency Induction Heating for Coaxial Inner Pipes
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Solution Overview
Problem
Conventional induction heating methods fail to effectively heat the inner pipe of coaxial undersea pipes due to the thick steel outer tube acting as a barrier, preventing the magnetic field from penetrating and efficiently heating the inner tube, especially in offshore oil industry applications where hydrate formation is a significant issue.
Innovation Solution
Using an electromagnetic induction coil surrounding the steel outer pipe and operating at a low frequency of 0.1 Hz to 10 Hz to induce currents in the inner pipe, maximizing Joule effect heating power and ensuring sufficient energy efficiency for maintaining the inner pipe temperature above 20°C to prevent hydrate formation, with a movable induction heater device capable of moving along the pipe to maintain temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional induction heating methods are used with high frequency (higher than 1 kHz), then the Joule effect heating power on the outer wall increases, but the magnetic field cannot penetrate the thick steel outer tube to heat the inner pipe effectively
Solution Approach 1:
The patent changes the frequency parameter from conventional high frequency (>1 kHz) to low frequency (0.1 Hz to 10 Hz). This parameter change allows the magnetic field to penetrate the thick steel outer tube effectively, inducing eddy currents in the inner pipe that generate Joule heating directly within the inner pipe wall, thereby resolving the contradiction between outer wall heating power and inner pipe heating effectiveness
Solution Approach 2:
The patent uses the low frequency electromagnetic field as an intermediary that can penetrate the thick steel outer tube barrier. This intermediary enables energy transfer from the external induction coil through the outer tube to the inner pipe, solving the problem of magnetic field blockage by the thick steel barrier
2Temperature
If the frequency is reduced to enable magnetic field penetration, then the inner pipe can be heated, but the energy efficiency decreases
Solution Approach 1:
The patent optimizes the frequency parameter within the low frequency range (0.1 Hz to 10 Hz) to achieve a balance between magnetic field penetration capability and energy efficiency. This optimized parameter selection ensures sufficient penetration through the thick steel outer tube while maintaining acceptable heating efficiency
Solution Approach 2:
The patent uses low frequency electromagnetic fields that can 'skip through' or penetrate the thick steel outer tube barrier more effectively than high frequency fields. This allows the magnetic field to reach the inner pipe and induce heating directly, bypassing the energy loss that would occur with conventional high frequency methods
3Temperature
If electric cables are wound around the steel pipes for heating, then the pipes can be maintained at critical temperature, but the device complexity and installation requirements increase
Solution Approach 1:
The patent replaces the mechanical cable-based heating system with an electromagnetic induction heating system. Instead of physically winding electric cables around the pipes and supplying power through umbilicals, the system uses an external induction coil to generate electromagnetic fields that induce currents directly in the pipe, eliminating the need for complex cable routing and power supply infrastructure
Solution Approach 2:
The induction heating system enables the pipe to heat itself through induced eddy currents. The electromagnetic field from the external coil induces currents within the pipe material, which generates heat internally without requiring external heating elements or complex control systems, thereby reducing device complexity
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 method effectively heats the inner pipe to maintain temperatures above 20°C, preventing hydrate formation and allowing for the unblocking of pipelines, with heating rates of up to 10 kilometers per day, using electrical power efficiently and maintaining temperatures for extended periods.
Implementation Method 1
the inner pipe is heated by induction using an electromagnetic induction coil surrounding the outer pipe coaxially
Implementation Method 2
induce currents in the inner pipe, maximizing Joule effect heating power
Data Source
AI summary
A method of heating an inner pipe of a set of coaxial pipes, wherein the inner pipe is heated by induction using an electromagnetic induction coil (5) surrounding the outer pipe coaxially, the coil passing electrical power at a frequency lower than 100 Hz optimized for maximum energy efficiency of Joule effect heating of the inner pipe. A device (8) is also provided for induction heating an inner pipe of coaxial pipes, the device has a) an induction heater having at least one electromagnetic induction coil (5) coaxially surrounding the outer pipe of the coaxial pipes, and b) a raising device (9) for raising a portion (1-2) of coaxial pipes (1) above the sea bed (13) together with the induction coil(s) (5) surrounding it.