Mechanically Jointed Heat Exchanger Header for Thermal Expansion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Heat exchangers in automotive applications face challenges such as thermal stress-induced failures due to uneven thermal expansion, reduced heat transfer efficiency, and mechanical robustness issues, particularly in brazed headers, which can lead to premature failure and increased size requirements for mechanically jointed heat exchangers to maintain efficiency.
Innovation Solution
An all-metal bonded heat exchanger design featuring a matrix of parallel metallic tubes and fins with compliant members at the tube-header joints, allowing for relative movement due to thermal expansion, combined with metal-to-metal bonding for enhanced thermal conductivity and mechanical robustness, while avoiding costly brazing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If brazing process is used to bond matrix and header, then thermal conductivity and mechanical strength are improved, but manufacturing cost and process complexity increase
Solution Approach 1:
The patent replaces the thermal bonding process (brazing) with a mechanical bonding system. Specifically, it uses a mechanically jointed header with integrated sealing elements and mechanical fasteners to connect the matrix to the header, eliminating the need for brazing furnaces and complex thermal processing while achieving equivalent or superior joint reliability.
Solution Approach 2:
The patent introduces intermediary components such as sealing rings, gaskets, and mechanical fasteners that mediate the connection between the matrix and header. These intermediaries provide both sealing functionality and mechanical attachment, replacing the direct metal-to-metal brazed joint with a multi-component mechanical assembly that is easier and cheaper to manufacture.
2Strength
If brazed headers are used, then thermal conductivity is improved, but thermal stress-induced failures occur due to uneven thermal expansion
Solution Approach 1:
The patent employs dynamic, flexible connection elements such as compliant sealing rings and elastic mounting structures that allow for differential thermal expansion between the matrix and header. These dynamic elements can deform and adjust during thermal cycling, preventing the buildup of thermal stresses that would otherwise lead to joint failure in rigid brazed constructions.
Solution Approach 2:
The patent uses flexible sealing elements and thin-film mounting structures between the matrix and header that can accommodate thermal expansion differences. These flexible components act as shock absorbers during thermal cycling, maintaining the integrity of the connection while allowing for dimensional changes in the metal components.
3Ease of manufacture
If mechanically jointed header is used to avoid brazing, then manufacturing cost is reduced, but heat transfer efficiency decreases
Solution Approach 1:
The patent applies local quality by providing enhanced thermal contact only at the critical heat transfer interfaces. The mechanical jointing system incorporates high-conductivity thermal interface materials and pressure-tight sealing elements specifically at the matrix-header connection points, ensuring that heat transfer efficiency is maintained in the most critical thermal pathways while using simpler, lower-cost mechanical fastening methods elsewhere in the assembly.
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 solution provides improved durability against thermal cycling, maintains high heat transfer efficiency, and reduces the risk of mechanical stress, enabling a compact and robust heat exchanger design that minimizes the need for larger sizes while ensuring reliable operation across varying temperatures.
Implementation Method 1
said compliant member extending around said first end portion to provide a seal with said first end portion for coolant held within the heat exchanger and permitting relative movement between said mechanically joined tube and the first header owing to thermal expansion and contraction of said matrix
Implementation Method 2
an all-metal bonded matrix including a plurality of substantially parallel metallic tubes and a plurality of metallic fins... configured to transfer heat between an external medium and a coolant conveyed between said headers by said tubes
Implementation Method 3
expanding the wall in the first end portion of the tube relative to the wall in the heat transfer portion of the tube such that the sealing portion of the compliant member is compressed in contact with the expanded wall in the end portion of the tube
Data Source
AI summary
A heat exchanger and methods of manufacturing and assembling a heat exchanger, and more particularly to an air-flow heat exchanger having a mechanically assembled header for use in a motor vehicle. The heat exchanger comprises an all-metal bonded matrix including a plurality of substantially parallel metallic tubes and a plurality of metallic fins. The tubes have a heat transfer portion that is elongate in cross-sectional shape, and which comprises two opposing, longer sides, and two opposing shorter sides. At least one of the tubes is mechanically joined at a first end portion thereof to a first header of the heat exchanger by at least one compliant member. The compliant member extends around the first end portion of the tube to provide a seal and to permit relative movement between the mechanically joined tube and the first header due to thermal expansion and contraction of the matrix.