Microchannel Heat Exchanger Braze Joint for Corrosion Resistance
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Solution Overview
Problem
Aluminum alloy heat exchangers in microchannel heat exchangers are susceptible to corrosion at the joint between fins and tubes due to corrosive condensates, leading to leaks and failures, particularly in residential and commercial cooling applications.
Innovation Solution
A braze joint with a length less than 650 micrometers is used to affix a fin to an aluminum alloy tube, utilizing the fin's core material as the brazing filler and minimizing silicon content to reduce galvanic corrosion, while maintaining a protective zinc coating on the tube surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a traditional braze joint is used to affix fin to aluminum alloy tube, then the joint strength is sufficient, but the corrosion resistance deteriorates due to galvanic corrosion at the joint
Solution Approach 1:
The patent changes the chemical composition parameters of the brazing filler material, specifically limiting silicon content to 0-5 wt% and adjusting aluminum content to 85-95 wt%, to reduce galvanic corrosion while maintaining joint strength. This parameter optimization resolves the contradiction between strength and corrosion resistance.
Solution Approach 2:
The patent applies different material compositions to different parts of the joint: the brazing filler material has a specific composition optimized for corrosion resistance, while the base metals (fin and tube) maintain their original properties. This local differentiation allows the joint to have both strength and corrosion resistance.
2Ease of manufacture
If silicon-containing brazing filler material is used, then the brazing process is easier, but galvanic corrosion increases at the joint
Solution Approach 1:
The patent optimizes the silicon content parameter within a specific range (0-5 wt%) to balance brazing processability and corrosion resistance. This controlled parameter change allows the brazing process to remain feasible while minimizing galvanic corrosion effects.
Solution Approach 2:
The brazing filler material is designed as a composite alloy with controlled proportions of aluminum, silicon, and other elements. This composite composition provides both the ease of brazing (from appropriate silicon content) and corrosion resistance (from limited silicon and protective aluminum matrix).
3Ease of manufacture
If the zinc coating on the tube is removed during brazing, then the braze joint formation is improved, but corrosion resistance deteriorates
Solution Approach 1:
The patent applies preliminary protective measures by selecting a brazing filler material composition that is less aggressive toward zinc coating, and controlling brazing parameters to minimize zinc removal. This preliminary protection allows successful joint formation while preserving corrosion resistance.
Solution Approach 2:
The brazing filler material acts as an intermediary that facilitates joint formation without completely removing the zinc coating. The specific composition (85-95% Al, 0-5% Si, with Mn, Mg, Si additions) enables the filler to bond the joint while leaving the protective zinc layer substantially intact.
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 enhances corrosion resistance at the joint, reducing leaks and failures by minimizing galvanic corrosion and preserving the zinc coating as a protective barrier.
Implementation Method 1
A portion of the fin is affixed to an adjacent surface of the at least one heat exchange tube segment via a braze joint. The braze joint is formed by a brazing filler material connecting the fin and the adjacent surface of the at least one heat exchange tube segment
Implementation Method 2
Heat from one of the fluids is transferred to the other fluid by conduction through the tube walls
Implementation Method 3
minimizing silicon content to reduce galvanic corrosion, while maintaining a protective zinc coating on the tube surface
Data Source
AI summary
A heat exchanger includes a first manifold, aa second manifold, at least one heat exchange tube segment extending between and fluidly coupling the first manifold and the second manifold, and a fin having a non-linear configuration. A portion of the fin is affixed to an adjacent surface of the at least one heat exchange tube segment via a braze joint. The braze joint has a length, measured parallel to a length of the at least one heat exchange tube segment, less than or equal to 650 micrometers.