Stainless Steel Header Tube Joint Leakage Reduction
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Solution Overview
Problem
High-temperature air-to-air after-cooler and exhaust gas recirculation cooler systems experience leakage at the tube/header joint due to differing thermal expansion coefficients of brass/copper tubes and carbon steel headers, leading to increased stress and eventual leaks, which current solutions like brazing or adhesives cannot effectively prevent without adding cost and complexity.
Innovation Solution
Mechanically joining the tubes to a header made of stainless steel, which has similar thermal expansion properties to the tubes, eliminating the need for bonding agents and reducing the gap between the tube/header joint, thereby minimizing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If carbon steel headers are used with brass/copper tubes, then manufacturing cost is reduced, but leakage occurs at the tube/header joint due to differing thermal expansion coefficients
Solution Approach 1:
The patent changes the material parameter of the header from carbon steel to stainless steel, which has a thermal expansion coefficient closer to that of brass/copper tubes. This parameter change resolves the thermal expansion mismatch problem while maintaining mechanical joining feasibility, thereby preventing leakage without significantly increasing manufacturing cost.
Solution Approach 2:
The patent employs a composite material strategy by selecting stainless steel for the header that is compatible with brass/copper tubes. This material selection creates a more harmonious material pair that reduces thermal stress and prevents joint failure under temperature cycling conditions.
2Reliability
If brazing or bonding agents are used to seal leaks, then leakage is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The patent removes the need for brazing or bonding agents by addressing the root cause of leakage through material selection. By using stainless steel headers with compatible thermal expansion properties, the joint remains sealed through proper mechanical joining alone, eliminating additional manufacturing steps and reducing process complexity.
Solution Approach 2:
The patent replaces chemical joining methods (brazing, bonding) with a properly designed mechanical joining system. The mechanical expansion and sealing process alone is sufficient when the correct materials are used, substituting complex chemical processes with a simpler mechanical solution.
3Ease of manufacture
If mechanical expansion is used to join tubes to carbon steel headers, then assembly is simplified, but stress concentration occurs due to thermal expansion differences
Solution Approach 1:
The patent changes the header material parameter to stainless steel, which has thermal expansion properties closer to brass/copper tubes. This reduces thermal stress concentration during mechanical expansion and service conditions, maintaining joint strength while preserving the simplicity of the mechanical assembly process.
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 use of stainless steel headers with similar thermal expansion coefficients to brass/copper tubes significantly reduces stress and leakage at the joint, providing a cost-effective and reliable mechanical bond that withstands high temperatures and increases the heat exchange capability, while also offering corrosion protection.
Implementation Method 1
the first metal and the second metal have similar coefficients of thermal expansions
Data Source
Figure 1~2
Figure 3A~4B
Figure 5A~5B
AI summary
A heat exchanger, such as an air-to-air after-cooler assembly, having reduced and/or eliminated leakage at the tube/header joint is provided. The assembly comprises a series of tubular members formed from a first metal, each of the tubular members including an end portion and a header formed from a second metal, wherein the first metal and the second metal have similar coefficients of thermal expansions. The header includes a plurality of openings extending therethrough and each of the end portions of the tubular members is mechanically secured within corresponding openings within the header to form an after-cooler assembly. A method for forming the air-to-air after-cooler assembly is also provided.