Header Tube Tab Geometry for Airtight Brazed Heat Exchangers
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Solution Overview
Problem
The existing header tubes in air conditioners suffer from leakage issues due to expanded gaps between tab members and the second member, which affects the airtightness of the brazed joint.
Innovation Solution
A header tube design where tab members of one member are bent over the other member to fix it in place, followed by brazing, ensuring airtightness by concentrating brazing material at the joint tips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If tab members are bent to come into contact with the second member, then the first member and second member are fixed relative to each other, but gaps between the tab members and second member are expanded at the tips due to springback behaviors
Solution Approach 1:
The tab members are preliminarily bent at an angle greater than 90 degrees (specifically 95-110 degrees) to pre-compensate for the springback behavior that occurs during brazing. This preliminary anti-action ensures that after springback reduces the angle, the tab members still maintain sufficient contact pressure with the second member without creating excessive gaps at the tips.
Solution Approach 2:
The bending angle of the tab members is changed from the conventional 90 degrees to a range of 95-110 degrees. This parameter change accounts for the springback behavior and ensures that the final gap dimensions after brazing remain within acceptable tolerances for airtightness.
2Ease of manufacture
If tab members are bent to come into contact with the second member, then the structure is simplified compared to full brazing, but droplets of molten brazing material may run downward and fail to be sufficiently distributed across the joint
Solution Approach 1:
The tab members are preliminarily bent at an angle greater than 90 degrees to create a geometry that prevents molten brazing material droplets from running downward and away from the joint. The bent shape acts as a barrier that redirects the molten material back toward the joint area, ensuring sufficient distribution for airtightness.
Solution Approach 2:
The bent tab members serve as an intermediary structure that both mechanically holds the first and second members together and guides the molten brazing material to the joint area. The tab members mediate between the simplified assembly structure and the requirement for reliable brazing distribution.
3Manufacturing precision
If the bending angle of tab members is increased to compensate for springback, then gap expansion is reduced, but the tab members may exert excessive force on the second member
Solution Approach 1:
The bending angle is optimized to a specific range (95-110 degrees) rather than simply increasing it indefinitely. This parameter optimization balances the need to compensate for springback while limiting the contact stress exerted on the second member, preventing damage or deformation of the bonded components.
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 design achieves airtightness by ensuring sufficient distribution of brazing material across the joint, preventing cracks and leakage during the manufacturing process.
Implementation Method 1
The tab members are bent relative to the lateral plate so as to face the second member
Implementation Method 2
bonded to the first member by brazing
Data Source
AI summary
An upper header tube according to the present disclosure is connectable to heat transfer tubes arranged in parallel to each other, and is capable of constituting a heat exchanger together with the heat transfer tubes. The upper header tube includes a first member including a bottom plate and a pair of lateral plates standing at opposed edges of the bottom plate, a second member disposed apart from the bottom plate, held between the pair of lateral plates, and bonded to the first member by brazing, and tab members disposed at the edges of the pair of lateral plates of the first member. The tab members are bent relative to the lateral plate so as to face the second member. Each of the tab members is tapered toward the tip in plan view.