Embossed Aluminum Strip for Stronger Heat Exchanger Brazed Joints
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Solution Overview
Problem
Heat exchangers face challenges in producing long-lasting components with reduced material thickness under higher operating pressures, where solder availability is critical, and thermal joining is prone to burn-through and material weakening, especially at tube sheet joints with small contact surfaces.
Innovation Solution
A roll-embossed aluminum alloy strip with a direction-independent surface topography is used for heat exchanger components, providing larger contact surfaces and improved forming capabilities through embossing, drawing, or ironing processes, which enhances joint strength and reduces material deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If material thickness is reduced to achieve weight savings, then weight reduction is improved, but joint reliability deteriorates due to reduced solder amount and increased susceptibility to burn-through and material weakening during thermal joining
Solution Approach 1:
The tube sheet is provided with localized recesses at the joining positions where tubes are to be connected. These recesses concentrate the solder in specific areas, creating locally enhanced joint quality without requiring increased overall material thickness. The recesses ensure adequate solder volume and distribution at critical joining points even when the base material is thin.
Solution Approach 2:
The recesses are pre-formed in the tube sheet before the thermal joining process. This preliminary shaping of the joining surface ensures that when solder is applied and heated, it is contained within the recesses and properly distributed, preventing burn-through and ensuring complete joint formation before the solder solidifies.
2Weight of moving object
If material thickness is reduced, then weight savings are achieved, but the amount of solder available for joining is reduced
Solution Approach 1:
By creating localized recesses at joining positions, the design concentrates the available solder volume into specific areas where it is most needed. This allows adequate solder quantity for reliable joints even when the overall material thickness and total solder budget are reduced.
Solution Approach 2:
Instead of increasing solder amount by increasing material thickness (one-dimensional approach), the invention uses recesses to create three-dimensional solder containment zones. This vertical dimensioning of solder placement ensures adequate solder volume without requiring thicker base materials.
3Ease of manufacture
If thermal joining is performed on thin materials, then joining is achieved, but burn-through and material weakening occur
Solution Approach 1:
The recesses act as cushioning chambers that contain and distribute thermal energy during the joining process. By pre-forming these recesses, the design anticipates and mitigates the risk of burn-through, allowing thermal joining to proceed on thin materials without compromising joint strength or causing material damage.
Solution Approach 2:
The recesses create localized zones with enhanced thermal management properties. The geometry of the recesses concentrates and controls heat distribution at the joining point, ensuring adequate heat for solder flow while preventing excessive heat that would cause burn-through or material weakening.
4Device complexity
If tube sheet joints are designed with perpendicular tube and sheet surfaces, then geometric simplicity is maintained, but contact area is reduced leading to defective joints
Solution Approach 1:
The tube sheet surface is segmented into multiple zones: flat areas for structural integrity and localized recesses for joining. This segmentation allows the maintenance of overall geometric simplicity while creating specific localized features that dramatically increase the contact area for soldering without requiring complex overall joint designs.
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 results in more reliable and durable heat exchanger components with improved solderability and reduced risk of joint failure, maintaining process capability while achieving weight savings.
Implementation Method 1
This direction-independent surface topography facilitates the forming process, as it provides lubricant pockets for the forming process.
Implementation Method 2
A further advantage is that the material of the pipes is also supported along the length of the depression by these contact surfaces, thus reducing elastic deformation of the pipes
Implementation Method 3
thermal bonding, such as CAB brazing
Implementation Method 4
thermal bonding, such as CAB brazing
Implementation Method 5
EP 1 202 018 A2 relates to an aluminum sheet with an increased surface area to enable improved heat transfer in a heat exchanger.
Data Source
Figure 1
Figure 2a~2b
Figure 2c~2d
AI summary
The invention relates to the use of a strip (2) made of an aluminum alloy for the manufacture of a heat exchanger component. The objective of providing a use of a strip (2) made of an aluminum alloy that further improves the manufacture of heat exchangers is achieved by using a roll-stamped strip (2) which has at least one region with a substantially direction-independent surface topography and by subjecting the strip (2) to a forming process during the manufacture of the heat exchanger component, wherein at least the region with the substantially direction-independent surface topography is formed. The invention further relates to an aluminum alloy strip (2) for the manufacture of a heat exchanger component by forming, particularly for a use according to the invention.