Heat Exchanger With Interleaved Flat Tubes And Conductive Sheets
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Solution Overview
Problem
Heat exchangers used for cooling exhaust gases face premature structural failure due to harsh mechanical stresses caused by cyclic thermal expansions and contractions, resulting from differences in thermal expansion between the cool casing and hot fluid conveying tubes.
Innovation Solution
A heat exchanger design featuring headers with interleaved flat tubes and plate assemblies, where thermally conductive structures, such as corrugated sheets, are placed in gaps between the tubes and plate assemblies to facilitate heat transfer while minimizing mechanical stresses through sacrificial fatigue locations, eliminating the need for a casing and reducing thermal gradient-induced stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional heat exchanger design with a casing and fluid conveying tubes is used, then heat transfer function is achieved, but harsh mechanical stresses cause premature structural failure due to cyclic thermal expansions and contractions
Solution Approach 1:
The patent removes the casing component from the traditional heat exchanger design. Instead of using a rigid casing to contain the tubes, the invention uses the tubes themselves as structural elements that are directly supported by the headers and mounted on the plate assemblies. This extraction of the casing eliminates the source of differential thermal expansion stresses between the casing and tubes.
Solution Approach 2:
The patent divides the heat exchanger into modular components: headers, plate assemblies with channels, and tubes. These segmented components can independently expand and contract during thermal cycles without imposing harsh stresses on each other. The plate assemblies act as flexible supports that accommodate thermal movements of individual tubes.
2Strength
If the second flow conduit is spaced away from the headers, then thermal gradient-induced stresses are reduced, but the structural complexity increases
Solution Approach 1:
The patent creates a dynamic structural arrangement where the tubes are freely mounted on the plate assemblies rather than being rigidly fixed. This allows the tubes to dynamically adjust their position and expansion in response to thermal gradients, reducing stress concentration at the header connections while maintaining functional integrity.
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 design enhances the structural integrity and longevity of the heat exchanger by relieving thermal stresses and preventing cross-leaks between fluids, thereby reducing the likelihood of fatigue cracking and extending the device's operational life.
Implementation Method 1
A thermally conductive structure is arranged in the gap and is joined to the two wall sections so that heat can be transferred between them
Implementation Method 2
The heat exchanger is designed to transfer heat between a first and a second fluid
Data Source
AI summary
A heat exchanger that includes first and second headers, a first flow conduit fluidly connecting the first and second headers to allow for a flow of a first fluid through the heat exchanger, the first flow conduit being bounded by a first generally planar wall section extending between the first and second headers, a second flow conduit to allow for a flow of the second fluid through the heat exchanger, the second flow conduit being bounded by a second generally planar wall section spaced apart from the first generally planar wall section to define a gap therebetween, and a thermally conductive structure arranged within the gap and joined to the first and second generally planar wall sections to transfer heat therebetween. The thermally conductive structure is isolated from the first fluid by the first generally planar wall section and from the second fluid by the second generally planar wall section.