Strain reduction clamshell heat exchanger design
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Solution Overview
Problem
Conventional gas furnaces experience cracking issues due to high plastic strain in clamshell heat exchangers, particularly at cold crack regions, which are not effectively addressed by existing solutions designed for hot crack regions, leading to premature failure and the need for more expensive materials or reduced operational life.
Innovation Solution
The clamshell heat exchanger design incorporates a truncated corner at the cold crack region, formed at an angle of less than 90 degrees or bent, to reduce plastic deformation and strain, allowing for the use of less costly materials like EDDS without sacrificing operational reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional clamshell heat exchanger panels are used with standard corner designs, then manufacturing is simpler and cheaper, but plastic strain and cold cracking occur at high operating temperatures
Solution Approach 1:
The patent applies local quality by modifying only the corner regions of the clamshell panels while maintaining the standard design for the majority of the panel surface. The corner regions are truncated or bent at specific angles (45-60 degrees) to reduce plastic strain concentration, while the rest of the panel retains its conventional geometry for manufacturing simplicity and cost-effectiveness.
2Reliability
If expensive DQHT sheet metal materials are used, then hot crack resistance is improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the geometric parameters of the panel corners (truncation angle, bend angle, corner radius) to alter the stress distribution and plastic strain characteristics. This allows the use of standard, less expensive sheet metal materials while achieving the same crack resistance that would otherwise require expensive DQHT materials.
3Ease of manufacture
If standard corner designs are used in clamshell panels, then manufacturing is easier, but plastic strain causes cold cracking at lower temperatures
Solution Approach 1:
The patent applies preliminary action by pre-modifying the corner geometry during the manufacturing process itself (through truncation or bending operations) to eliminate the conditions that lead to cold cracking. This preliminary geometric modification prevents plastic strain accumulation during subsequent thermal cycling, eliminating cold cracks without requiring additional protective measures or material upgrades.
Data Source
AI summary
One aspect of this disclosure provides a heating chamber for a gas furnace that comprises opposing halves joined together. The joined opposing halves form a clamshell panel having at least one truncated corner located adjacent a curve located at a back end of a chamber path of the one or more clamshell heating chambers.