Pipe-in-Pipe Electrical Heating With Coated Shells for Lower Heat Loss
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Solution Overview
Problem
Existing Direct Electrical Heating (DEH) solutions for subsea pipelines suffer from low performance, typically ranging from 50% to 60%, due to significant heat loss in the environment as the outer shell is in direct contact with seawater.
Innovation Solution
The method involves mechanically connecting the inner and outer shells of the Pipe-In-Pipe pipeline at intervals, establishing electrical and thermal insulation between them, and applying an alternating electric current between the outer surface of the inner shell and the inner surface of the outer shell. Additionally, a conductive and non-magnetic jacket is placed on the inner surface of the outer shell, and/or a resistive and ferromagnetic layer is applied to the outer surface of the inner shell to enhance power transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct electrical heating is applied to the inner shell using the outer shell as return conductor, then the heating simplicity and design ease are improved, but the heating efficiency deteriorates due to heat loss in seawater
Solution Approach 1:
A conductive non-magnetic jacket (aluminum, copper, or their alloys) is introduced as an intermediary layer on the outer shell's inner surface. This jacket serves as a mediator to concentrate and redirect electromagnetic energy toward the inner shell, improving heating efficiency from 50-60% to over 90% by reducing energy loss to seawater while maintaining the simplicity of the direct electrical heating configuration
2Productivity
If alternating electric current is applied directly between inner and outer shells, then the heating performance is improved compared to cable-based heating, but energy loss to the environment worsens due to outer shell contact with seawater
Solution Approach 1:
The electrical and magnetic parameters of the outer shell are modified by coating it with a conductive non-magnetic material. This changes the electromagnetic field distribution and energy penetration characteristics, allowing the alternating current to heat the inner shell more effectively while reducing the proportion of energy lost to the surrounding seawater environment
3Strength
If the outer shell is made of steel for structural integrity, then the mechanical strength is improved, but the electrical heating efficiency deteriorates due to magnetic properties causing energy loss
Solution Approach 1:
The outer shell is transformed into a composite structure by coating the steel substrate with a conductive non-magnetic layer (aluminum, copper, or their alloys). This composite configuration retains the mechanical strength of steel while eliminating the detrimental magnetic properties that cause energy loss during electrical heating, enabling efficient direct electrical heating
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
This approach significantly improves the efficiency of electric power transmission to the inner shell, achieving performance levels of at least 85% to 98%, thereby overcoming the limitations of existing DEH solutions.
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; much of the heat produced is transmitted to the fluids in the inner shell
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.