Furnace Heating Conductor with Pivotable Bands
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Solution Overview
Problem
Existing electrical heating conductor arrangements for furnaces experience premature failure due to persistent mechanical stress from thermal expansion and contraction, especially when using high-temperature materials like Mo or W, as they are rigidly clamped and subjected to alternating stresses.
Innovation Solution
The heating conductor is designed with arcuate curvature along its width, featuring pivotable bearing elements that allow for self-supporting stability and compensate for temperature-induced length changes, reducing mechanical stress by enabling expansion without rigid clamping, and incorporating features like inclined axes of rotation and symmetric kinks for enhanced stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the heating conductor is rigidly clamped between carrier devices, then the heating conductor is supported and positioned, but mechanical stress accumulates due to thermal expansion and contraction, leading to fracture or premature failure
Solution Approach 1:
The bearing element is designed to be pivotable about an axis, allowing the heating conductor to dynamically adjust its position during thermal expansion and contraction. This dynamic mounting enables the heating conductor to change its effective length and curvature radius in response to temperature changes, preventing stress accumulation while maintaining stable positioning during operation.
2Temperature
If high-temperature materials like Mo or W are used, then maximum furnace temperatures of 1700°C and above can be achieved, but the heating conductor fails rapidly due to persistent mechanical stress from rigid clamping
Solution Approach 1:
The pivotable bearing element allows high-temperature materials like Mo or W to thermally expand and contract freely during temperature cycles. The bearing element accommodates changes in length and curvature radius, preventing stress accumulation that would otherwise cause rapid failure. This enables the use of high-temperature materials while maintaining long service life.
3Area of stationary object
If the heating conductor is supported over long distances, then large-area heating is enabled, but the heating conductor sags or deforms under its own weight and thermal loads
Solution Approach 1:
The pivotable bearing element allows the heating conductor to dynamically adjust its shape and position in response to gravitational and thermal loads. The bearing element acts as a pivot point that maintains the heating conductor's stability over long distances while accommodating thermal expansion and contraction, preventing sagging and deformation.
4Manufacturing precision
If the heating conductor is tightly clamped to prevent movement, then positioning accuracy is improved, but thermal expansion causes stress concentration and material failure
Solution Approach 1:
The pivotable bearing element provides precise positioning while allowing controlled movement for thermal expansion. The bearing element's pivot axis enables the heating conductor to maintain accurate position during operation while accommodating length changes, preventing stress concentration and material failure.
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 design significantly reduces mechanical stress, maintaining inherent stability at high temperatures, allowing the use of materials like molybdenum or tungsten, and preventing sagging or fracture, thus extending the lifespan of the heating conductor.
Implementation Method 1
its curvature increases due to the thermally induced expansion of the heating conductor material and due to its rigid clamping between the carrier devices. During cooling, the heating conductor contracts again and returns to its original curvature
Data Source
AI summary
An electrical heating conductor arrangement for heating a furnace has one or more strip-shaped portions with a generally horizontal sheet-like extent. The strip-shaped portions are formed by individual bands which have along their width an arcuate curvature with respect to a horizontal plane. The individual bands are partially mounted by at least one bearing element pivotably in the longitudinal direction of the respective band.