SiC Ceramic Heat Exchanger Element Thermal Stress Management
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Solution Overview
Problem
Heat exchangers with ceramic passage walls face breakage due to thermal stress, which impairs their functionality and reduces temperature efficiency, despite efforts to enhance corrosion resistance.
Innovation Solution
A heat exchanger element with a cylindrical outer peripheral wall and partition walls made of ceramic containing SiC, designed to maintain temperature efficiency while inhibiting breakage through specific thickness and density ratios, and a covering member to separate fluids, ensuring effective heat exchange.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ceramic passage walls are used to enhance corrosion resistance, then corrosion resistance is improved, but thermal stress causes breakage
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness parameters of the outer peripheral wall (T) and partition walls (t) relative to the equivalent circle diameter (D). Specifically, it defines ranges for T/D ratio (0.01-0.15) and t/D ratio (0.005-0.08), and their ratio relationship (0.05-0.5). These parameter optimizations allow the ceramic structure to withstand thermal stress while maintaining corrosion resistance, resolving the contradiction between durability and strength.
Solution Approach 2:
The patent uses composite material structure combining ceramic materials (containing SiC as main component) for both the outer peripheral wall and partition walls. This composite ceramic construction provides both corrosion resistance and improved thermal stress resistance, allowing the passage walls to maintain both properties simultaneously without one compromising the other.
2Productivity
If passage wall area is widened to improve heat exchange efficiency, then temperature efficiency is improved, but thermal stress increases causing breakage
Solution Approach 1:
The patent optimizes the geometric parameters including the equivalent circle diameter D and thickness T to achieve the optimal balance between heat exchange area and thermal stress resistance. By controlling T/D ratio within 0.01-0.15, the design achieves sufficient heat exchange efficiency while the optimized geometry distributes thermal stress to prevent breakage.
Solution Approach 2:
The patent divides the internal space into multiple cells using partition walls, creating multiple smaller passages instead of a single large passage. This segmentation increases the total heat exchange area while reducing the thermal stress in each individual passage wall, as the stress is distributed across multiple smaller walls rather than concentrated in one large wall.
3Strength
If partition walls are made thinner to reduce thermal stress, then breakage resistance is improved, but structural stability decreases
Solution Approach 1:
The patent optimizes the partition wall thickness t relative to the equivalent circle diameter D, defining t/D ratio within 0.005-0.08. This optimized thinness reduces thermal stress concentration while the overall structural configuration (with multiple partition walls forming cells) maintains sufficient structural stability. The outer peripheral wall thickness T is also optimized (T/D ratio 0.01-0.15) to provide additional structural support.
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 solution effectively inhibits breakage due to thermal stress while maintaining temperature efficiency and corrosion resistance, ensuring reliable operation and durability of the heat exchanger.
Implementation Method 1
a high-temperature fluid and a low temperature fluid is separated from each other by a passage wall having thermal conductivity, and heat is transferred to the passage wall, thereby conducting heat exchange between both the fluids
Implementation Method 2
there has been proposed a technique of enhancing corrosion resistance by the use of ceramic passage walls
Implementation Method 3
contraction or expansion is caused (thermal stress is generated) when ceramic passage walls receive heat
Data Source
Figure 1~2
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AI summary
The present invention aims at providing a technique for inhibiting the breakage due to thermal stress while maintaining temperature efficiency and corrosion resistance. There is provided a heat exchanger element 1 having a cylindrical outer peripheral wall 3 and partition walls 7 which are made of ceramic containing SiC as a main component and separate and form a plurality of cells 5 functioning as passages for a first fluid inside the outer peripheral wall 3. More specifically, in the heat exchanger element 1, the outer peripheral wall 3 and the partition walls 7 mediate heat exchange between the first fluid and the second fluid, and the thickness T of the outer peripheral wall 3, the equivalent circle diameter D calculated from the area of the portion inside the outer peripheral wall 3 in a cross section perpendicular to an axial direction of the outer peripheral wall 3, and thickness t of the partition walls 7 satisfy the following formulae (1) to (3): Formula (1): 0.3 mm ≤ T ≤ 4.0 mm, Formula (2): 15 mm ≤ D ≤ 120 mm, and Formula (3): 0.04 × T ≤ t ≤ 0.6 mm.