Helical Heating Resistor Thermal Expansion Management
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Solution Overview
Problem
Conventional heat-processing furnaces face durability issues due to the accumulation of creep strain and thermal expansion in helical heating resistors, leading to potential short circuits and reduced lifespan, especially in vertical furnaces where thermal expansion causes the heating line to deform and break.
Innovation Solution
The implementation of a heat-processing furnace design featuring a helical heating resistor supported by axial support members with terminal and fixing plates that are attached using a shared attachment structure, allowing for thermal expansion and contraction while embedding fixing plates within the heat insulating member to prevent stress concentration and joint overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a helical heating resistor is used in a vertical heat-processing furnace, then the furnace can heat the processing vessel at high temperature, but the heating resistor accumulates creep strain and thermal expansion leading to deformation and potential short circuits
Solution Approach 1:
The heating resistor is divided into multiple sections with support members positioned at regular intervals along its length. This segmentation provides multiple anchoring points that prevent cumulative thermal expansion and creep deformation, maintaining the resistor's geometric integrity at high temperatures while improving reliability
Solution Approach 2:
Support members are pre-installed at predetermined positions along the heating resistor before operation. These support members proactively counteract thermal expansion and creep strain before they can cause deformation or short circuits, preventing reliability issues rather than addressing them after they occur
2Stress or pressure
If the heating resistor is allowed to thermally expand and contract freely, then thermal stress is reduced, but the resistor may deform or break due to accumulated elongation
Solution Approach 1:
The heating resistor is segmented into multiple sections by support members that provide intermediate anchoring points. This segmentation allows each section to expand and contract independently with reduced thermal stress, while the overall geometric integrity is maintained by preventing cumulative elongation across the entire resistor length
3Reliability
If a rod-like fixing member is used to prevent elongation accumulation, then durability is improved, but the fixing member is easily escaped from the heat insulating member resulting in inferior sustainability
Solution Approach 1:
The support members are formed with a curved or bent configuration rather than straight rod-like shapes. This curvature allows the support members to flex with thermal expansion and contraction while maintaining their anchoring function, preventing both elongation accumulation and escape from the heat insulating member, thereby improving both durability and sustainability
4Reliability
If the heating resistor is supported at multiple points, then thermal expansion is accommodated, but the structure becomes more complex
Solution Approach 1:
The heating resistor structure is segmented into standardized sections with support members at regular intervals. This systematic segmentation accommodates thermal expansion through multiple support points while maintaining manufacturing simplicity and structural regularity, balancing reliability improvement with acceptable structural 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
This design enhances the durability of the heating resistor by preventing elongation accumulation and reducing the risk of short circuits, maintaining the fixing performance and extending the lifespan of the furnace by distributing stress and maintaining low joint temperatures.
Implementation Method 1
a heating resistor disposed along an inner circumferential surface of the heat insulating member
Implementation Method 2
a heat quantity taken away as a radiant heat and a conductive heat can be reduced
Implementation Method 3
a heat quantity taken away as a radiant heat and a conductive heat can be reduced
Implementation Method 4
the heater line thermally expands upon heating
Implementation Method 5
the heater line thermally expands upon heating
Implementation Method 6
use of the heating line under a high temperature invites a creep strain, so that a length of the heating line is gradually increased
Data Source
AI summary
A heat-processing furnace comprises: a processing vessel for housing an object to be processed to thermally heat the object to be processed; a cylindrical heat insulating member surrounding the processing vessel; a helical heating resistor disposed along an inner circumferential surface of the heat insulating member; and support members axially disposed on the inner circumferential surface of the heat insulating member, for supporting the heating resistor at predetermined pitches. A plurality of terminal plates are disposed outside the heating resistor at suitable intervals therebetween and attached to the heating resistor, the terminal plates radially passing through the heat insulating member to be extended outside. A plurality of fixing plates are disposed outside the heating resistor at suitable intervals therebetween and attached to the heating resistor, the fixing plates being fixed in the heat insulating member. The fixing plates are attached to the heating resistor by the same attachment structure as the attachment structure of the terminal plates to the heating resistor.