Header Plateless Heat Exchanger Flat Tube Brazing Gap
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Solution Overview
Problem
Header plateless heat exchangers face issues with gaps at the joining portions between flat tubes and header tanks, leading to potential losses in brazing and compromised air-tightness and liquid-tightness.
Innovation Solution
The solution involves forming flat tubes by joining plates with bent side walls and tab parts that extend and fold back to create a secure, gap-free interface, with features like cut-out portions, recessed areas, and protruding elements to ensure tight contact and fill gaps during brazing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If flat tubes are formed by joining plates with stepped portions, then manufacturing is simplified, but gaps are generated at the joining portion leading to brazing loss
Solution Approach 1:
The tab part is folded back in advance during the forming process to create a preliminary structure that eliminates gaps before brazing. This preliminary action of folding back the tab part ensures that when the second plate is joined to the first plate, the surfaces match perfectly without requiring gap-filling operations later.
Solution Approach 2:
The flat tube is divided into multiple components: the first plate, the second plate, and the tab part that folds back. This segmentation allows each component to be optimized independently - the tab part can be folded back to create precise alignment, while the main plates retain their structural integrity, ultimately achieving gap-free joining.
2Ease of manufacture
If corner portions are made round for ease of forming, then manufacturing is easier, but gaps are generated at the joining portion between flat tube and header tank
Solution Approach 1:
The tab part is folded back in advance to create a preliminary structure that eliminates gaps before brazing. This preliminary action of folding back the tab part ensures that when the second plate is joined to the first plate, the surfaces match perfectly without requiring gap-filling operations later.
Solution Approach 2:
The tab part acts as an intermediary element between the first plate and the second plate. By folding back the tab part, it creates a mediator structure that bridges the gap between the two plates and the header tank, ensuring tight contact and eliminating the need for additional gap-filling operations.
3Ease of operation
If gaps are left at the joining portion for assembly tolerance, then assembly is easier, but brazing is lost and air-tightness/liquid-tightness deteriorate
Solution Approach 1:
The tab part is folded back in advance during the forming process to create a preliminary structure that eliminates gaps before brazing. This preliminary action of folding back the tab part ensures that when the second plate is joined to the first plate, the surfaces match perfectly without requiring gap-filling operations later.
Solution Approach 2:
The solution moves from a two-dimensional plate joining problem to a three-dimensional structure by folding back the tab part. This dimensional change creates a multi-layered structure where the tab part extends in the width direction and folds back to contact the outer surface, adding a third dimension that eliminates gaps in the joining portion.
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
This configuration ensures tight contact between the flat tubes and header tanks, reducing brazing losses and enhancing air-tightness and liquid-tightness by eliminating gaps, thereby improving the overall performance of the heat exchanger.
Implementation Method 1
a first plate (1) and a second plate (2) each bent and formed into a groove shape by press forming
Implementation Method 2
tab parts (9) located at the bulging portion (4) and disposed so as to extend from the side walls (1a) of the first plate (1) are folded back to lie over outer surfaces of the side walls (1a) of the first plate (1)
Implementation Method 3
lower end surfaces of the side walls (2a) of the second plate (2) sit on upper end surfaces (9a) of the tab parts (9)
Implementation Method 4
a recessed portion (12) or a claw (13) is provided by striking in a thickness direction, located on a lower end edge of the tab part (9) to partially fill, with the recessed portion (12) or the claw (13), a gap between the outer surface of the side wall (1a) of the first plate (1) and an inner surface of the tab part (9)
Implementation Method 5
a protruding portion (14) is provided downward on the lower end surfaces (9c) of the tab part (9) to partially fill a gap between the tab part (9) and a member located below the first plate (1)
Implementation Method 6
heat exchange is performed between the gas and the cooling water
Data Source
AI summary
With respect to a header plateless heat exchanger having as a component a flat tube formed by joining a pair of grooved plates together, air-tightness and liquid-tightness are improved between the portion of the flat tube where the plates are joined together and a header tank. A flat tube is formed by folding tab parts extending from side walls of a first plate back outwards to lie over the outer surfaces of those side walls of the first plate, and placing seating portions of side walls of a second plate on the upper end surfaces of the tab parts, after which a header tank is fitted on each longitudinal end of the flat tube.