Bead-Formed Heat Exchanger Header Plate for Thermal Stress Reduction
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Solution Overview
Problem
Heat exchangers with flattened tubes experience thermal cycle stress due to temperature differences, leading to potential fracture and leakage at joints between tubes and header plates.
Innovation Solution
A header plate design featuring a generally planar surface with beads that locally deform away from the internal volume, extending into the side flanges, and tube receiving openings that pass through these beads, providing a secure and stress-reduced interface with the tubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard header plate design is used, then manufacturing cost is low, but thermal cycle life is limited due to stress fracture at joints
Solution Approach 1:
The header plate incorporates beads at specific locations where tubes connect to the plate. These beads create localized deformations that concentrate stress away from the tube-header joint, preventing fracture at these critical points while maintaining the overall simplicity of the header plate structure and manufacturing process.
Solution Approach 2:
The beads form curved, three-dimensional protrusions on the header plate surface. These curved structures provide a different stress distribution pattern compared to flat surfaces, allowing the header plate to withstand thermal cycling without fracturing at the tube connection points while still being manufacturable using conventional forming processes.
2Strength
If beads are formed into the planar surface, then thermal stresses are reduced, but manufacturing complexity increases
Solution Approach 1:
The beads modify the geometric parameters of the header plate surface by creating controlled deformations with specific dimensions and profiles. These parameter changes in the plate's surface geometry enable stress reduction during thermal cycling while the deformation can be achieved through standard manufacturing techniques, balancing strength improvement with manufacturing simplicity.
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 bead-formed header plate design reduces thermal stresses, allowing for higher-temperature applications and increasing the thermal cycle life of the heat exchanger by up to four times compared to standard designs, while maintaining low manufacturing costs.
Implementation Method 1
Some heat exchangers commonly experience thermal cycle stress due to fluids of different temperatures passing through the flattened tubes. In particular, different temperature fluids may cause expansion and/or contraction of the flattened tubes, creating stresses at joints between the tubes and the header plates.
Implementation Method 2
The beads allow the header plate and the tubes to be used in relatively higher-temperature applications, such as at inlet temperatures greater than 275 Celsius. The beads provide a 20 percent reduction in stress
Data Source
AI summary
A header plate for a heat exchanger includes a first side flange, a second side flange spaced apart from and opposing the first flange, and a generally planar surface located between and connecting the first and second flanges. The generally planar surface and the first and second side flanges together at least partially define an internal volume of the heat exchanger. The header plate also includes a bead formed into the generally planar surface to locally deform the surface in a direction away from the internal volume, the bead extending to and blending into the first side flange. The header plate also includes a tube receiving opening extending through the generally planar surface into the internal volume, the tube receiving opening extending through the bead.