Graphite Intermediate Layer for Ceramic-Metal Heat Exchanger Stress
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Solution Overview
Problem
Integrating a ceramic honeycomb structure with a metal base material leads to issues such as thermal expansion causing adhesion deterioration, thermal stress generation, and breakage due to insufficient adhesion and residual stress in heat exchangers, particularly when a cylindrical ceramic body is covered with a metal pipe.
Innovation Solution
A heat exchanger design that incorporates a graphite sheet with a Young's modulus of 1 GPa or less as an intermediate member between the cylindrical ceramic body and the metal pipe, enhancing adhesion and heat conductance while allowing for thermal expansion compensation, thus preventing stress generation and improving durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a cylindrical ceramic body is integrated with a metal pipe by press-fitting, then adhesion between the ceramic and metal is improved, but thermal stress causes breakage of the ceramic body
Solution Approach 1:
A graphite sheet is introduced as an intermediate layer between the cylindrical ceramic body and the metal pipe. This graphite sheet has a Young's modulus of 1 GPa or less in the thickness direction, allowing it to absorb thermal expansion differences and reduce thermal stress while maintaining adhesion. The graphite sheet acts as a stress-absorbing intermediary that prevents direct stress transmission to the ceramic body.
Solution Approach 2:
The Young's modulus of the intermediate material is specifically controlled to be 1 GPa or less in the thickness direction. This parameter change allows the material to be sufficiently compliant to absorb thermal stress while maintaining adequate structural integrity for heat conduction and adhesion purposes.
2Power
If a cylindrical ceramic body is integrated with a metal pipe, then heat conductance is improved, but thermal expansion difference causes adhesion deterioration
Solution Approach 1:
The graphite sheet serves as an intermediary that accommodates thermal expansion differences between the ceramic and metal while maintaining the thermal coupling state. Its low Young's modulus allows it to deform elastically during thermal cycling, preventing adhesion deterioration despite repeated expansion and contraction.
Solution Approach 2:
The heat exchanger employs a composite structure consisting of ceramic, graphite, and metal components. Each material is selected for its specific properties: ceramic for heat resistance, graphite for stress absorption and heat conduction, and metal for structural support. This composite approach allows each material to perform optimally without being constrained by the limitations of the others.
3Temperature
If a cylindrical ceramic body is used for heat exchange, then heat resistance is improved, but liquid leakage occurs requiring shielding
Solution Approach 1:
The metal pipe acts as an external shielding structure that prevents liquid leakage from the ceramic body. The graphite sheet bonded to the ceramic outer surface serves as an intermediate layer that maintains the thermal coupling state while allowing the metal pipe to provide the protective shielding function against liquid leakage.
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 graphite sheet improves heat conductance and reduces stress due to thermal expansion differences, ensuring effective heat transfer and increased durability of the heat exchanger by maintaining a thermal coupling state and preventing breakage.
Implementation Method 1
The graphite sheet improves heat conductance and reduces stress due to thermal expansion differences
Implementation Method 2
reduces stress due to thermal expansion differences
Data Source
Figure 1~2
Figure 3~4
Figure 5~6B
AI summary
There is provided a heat conduction member inhibiting stress generation due to a thermal expansion difference while maintaining a thermally bonded state in a case of covering a cylindrical ceramic body with a metal pipe. A heat conduction member 10 includes: a cylindrical ceramic body 11, a metal pipe 12 on the outer periphery side of the cylindrical ceramic body 11, and an intermediate member 13 held between the cylindrical ceramic body 11 and the metal pipe 12. The cylindrical ceramic body 11 has passages passing through from one end face to the other end face and allowing the first fluid to flow therethrough. The intermediate member 13 is made of material having at least a part having a Young' s modulus of 150 Gpa or less. The first fluid is allowed to flow through the inside of the cylindrical ceramic body 11 while the second fluid having lower temperature than that of the first fluid is allowed to flow on the outer peripheral face 12h side of the metal pipe 12 to perform heat exchange between the first fluid and the second fluid.