Profiled Closure Bars for Plate-Fin Heat Exchanger Thermal Fatigue

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Solution Overview

Problem

Conventional plate-fin heat exchanger cores experience uneven thermal expansion and bending distortion due to concentrated hot fluid entry, leading to fatigue and damage at the core's center, necessitating premature replacement.

Innovation Solution

The closure bars in the heat exchanger core are profiled with a rectangular main body and a wider end portion, featuring a radius transition, and stacked to form a curved inner profile, reducing thermal loading and eliminating the need for additional corner angles, thus preventing damage from thermal stresses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional rectangular closure bars with solid corner angles are used, then the core provides structural strength and seals the layers, but the concentrated heating causes uneven thermal expansion leading to bending distortion and fatigue damage at the center

Engineering Contradiction:

Improvestructural strength of coreVSAvoidresistance to thermal fatigue

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The closure bars are given a non-uniform cross-sectional profile with different dimensions at the center versus the ends. The central portion has reduced dimensions compared to the end portions, creating local variation in thermal mass and expansion characteristics. This local quality change allows the center to expand more freely under concentrated heating while maintaining overall structural integrity through the stronger end portions.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The closure bar profile is made asymmetric along its length, with the central portion having different dimensions than the end portions. This asymmetry in geometry creates corresponding asymmetry in thermal response, allowing the center to accommodate thermal expansion differently from the ends, thereby reducing bending distortion and fatigue stresses.

Inventive Principle:

Principle #4Asymmetry

2Stability of the object's composition

If solid corner angles are brazed to provide complete block units, then the core achieves structural completeness, but the design requires additional manufacturing steps and potential failure points from brazing

Engineering Contradiction:

Improvecompleteness of block structureVSAvoidnumber of assembly steps

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The invention merges the functions of the closure bar and the corner angle into a single integrated component. The closure bar itself is designed with extended end portions that overlap adjacent closure bars to form solid corners, eliminating the need for separate corner angle components and their associated brazing operations. This merging reduces manufacturing complexity while maintaining structural completeness.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The separate corner angle components are extracted from the design, and their function is instead provided by the extended end portions of the closure bars themselves. This eliminates the need for additional brazing steps to attach corner angles, simplifying the manufacturing process while achieving the same structural effect.

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of manufacture

If the closure bars have uniform rectangular cross-section, then the manufacturing is simple, but the thermal expansion under concentrated heating causes bending distortion

Engineering Contradiction:

Improvesimplicity of closure bar fabricationVSAvoiddistortion of closure bar

Core Design Contradiction:

Ease of manufactureVSShape

Solution Approach 1:

The closure bar is given a non-uniform cross-sectional profile where the central portion has different dimensions than the end portions. This local variation in geometry is designed to match the local thermal loading pattern, with the reduced central section allowing for greater thermal expansion flexibility while the fuller end portions maintain structural shape and position.

Inventive Principle:

Principle #3Local quality

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 redesigned closure bars mitigate thermal fatigue and eliminate the need for brazing, enhancing durability and reducing weight while maintaining performance.

Implementation Method 1

This results in a localised heating resulting in uneven thermal expansion in the core in some conditions

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS12529522B2Heat exchanger construction

Publication Date: 2026.01.20 HS MARSTON AEROSPACE

AI summary

A closure bar for a plate-fin heat exchanger core, the closure bar having a substantially rectangular main body portion defined by a first edge and a second edge and an end portion having a first end portion edge, and opposite second end portion edge and an end edge extending between the first end portion edge and the second end portion edge, wherein the first edge of the main body portion and the first end portion edge form a continuous substantially straight first closure bar edge and wherein the second end portion edge is spaced from the first end portion edge by a distance (d1) greater than the distance (d2) between the first edge and second edges of the main body portion, and wherein the second edge of the main body portion and the second end portion edge joined by a radius portion define a second edge of the closure bar.