Double-Walled Pipe Heating With Insulated Shells and Ferromagnetic Layer
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Solution Overview
Problem
Direct Electrical Heating (DEH) solutions for subsea pipelines suffer from low performance due to significant heat loss in sea water, with only 50% to 60% of heat being transmitted to the fluids, as the outer shell is in direct contact with seawater.
Innovation Solution
Mechanical connection of the inner and outer shells with electrical and thermal insulation, and application of a conductive non-magnetic jacket on the outer shell and a resistive ferromagnetic layer on the inner shell to increase the ratio of electric power transmitted to the inner shell, achieving efficiencies of up to 98% by optimizing electromagnetic characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If Direct Electrical Heating is applied to the subsea pipeline with the outer shell in direct contact with seawater, then the heating mechanism is simple, but the heat loss to the environment is significant resulting in low efficiency
Solution Approach 1:
The patent introduces an intermediate insulating layer between the outer shell and the seawater environment. This intermediary barrier prevents direct thermal contact between the heated pipeline and the cooling seawater, thereby reducing heat loss while maintaining the simplicity of the direct electrical heating mechanism.
Solution Approach 2:
The patent employs composite material structures combining different thermal properties - typically an inner conductive layer for heat generation, an intermediate insulating layer for heat retention, and an outer protective layer for environmental resistance. This composite structure optimizes both thermal efficiency and structural integrity.
2Device complexity
If the outer shell is in direct contact with seawater for structural simplicity, then the device structure is simple, but the thermal insulation performance is poor leading to energy loss
Solution Approach 1:
The patent divides the outer shell structure into multiple segmented layers, each with specific functions - structural support, thermal insulation, and environmental protection. This segmentation allows the system to achieve reliable thermal insulation without significantly increasing overall structural complexity.
Solution Approach 2:
The patent applies different material properties to different regions or layers of the outer shell - the inner layer near the fluid has different thermal characteristics than the outer layer contacting seawater. This local differentiation optimizes thermal insulation performance where most needed while maintaining structural simplicity elsewhere.
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 improves the efficiency of heat transfer to the fluids, achieving performance levels of 90% to 95% or more by utilizing conductive non-magnetic materials and resistive ferromagnetic materials, reducing heat loss and enhancing the Joule effect heating mechanism.
Implementation Method 1
The alternating electric current traveling through the inner shell thus allows heating the latter by Joule effect. More specifically, the heating of the inner shell is produced by Joule effect by the current passing therethrough
Implementation Method 2
placing on the inner surface of the outer shell over the entire length of the pipeline a jacket made of conductive and non-magnetic material and/or placing on the outer surface of the inner shell over the entire length of the pipeline at least one layer made of resistive and ferromagnetic material so as to increase the ratio of electric power transmitted to the inner shell
Data Source
AI summary
A method and system for Direct Electrical Heating of a Pipe-In-Pipe pipeline for transporting fluids includes mechanically connecting the steel inner shell to the steel outer shell at different intervals of the pipeline, establishing an electrical and thermal insulation between the inner shell and the outer shell, applying an alternating electric current between an outer surface of the inner shell and an inner surface of the outer shell over the entire length of the pipeline so as to heat the inner shell of the pipeline by Joule effect, and placing on the outer surface of the inner shell at least one layer made of resistive and ferromagnetic material so as to increase the ratio of electric power transmitted to the inner shell.