Silicon Carbide Heat Exchanger with Ceramic Retention
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Solution Overview
Problem
Existing exhaust heat recovery systems face issues with heat transmission from high-temperature exhaust pipes to heat exchangers, leading to boiling of the coolant medium when the engine is stopped, especially when a metal band is interposed between a ceramic honeycomb structure and a case, as it facilitates heat transfer and increases the risk of coolant boiling.
Innovation Solution
An exhaust heat recovery unit featuring a heat exchanger made of silicon carbide within an exhaust pipe, with a retention member formed of a ceramic sheet or expandable graphite sheet sandwiched between the heat exchanger and the exhaust pipe, reducing heat transfer and preventing coolant boiling by acting as a thermal barrier and seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal band is interposed between a ceramic honeycomb structure and a case to retain the heat exchanger, then the heat exchanger is securely retained in the exhaust pipe, but heat is easily transmitted from the exhaust pipe to the heat exchanger, causing the coolant to boil
Solution Approach 1:
The patent introduces a retention member made of ceramic or graphite material as an intermediary between the exhaust pipe and the heat exchanger. This retention member has both mechanical strength to retain the heat exchanger and low thermal conductivity to prevent heat transmission, thereby resolving the contradiction between retention strength and temperature control
Solution Approach 2:
The patent uses composite material structure where the retention member is made of ceramic or graphite materials that combine mechanical strength with thermal insulation properties. This composite approach allows the retention member to provide both structural support and thermal barrier functions simultaneously
2Reliability
If the engine is stopped after high-load travel, then the exhaust pipe reaches high temperature, but the coolant flow stops, making the coolant susceptible to boiling when heat is transmitted
Solution Approach 1:
The patent applies beforehand cushioning by installing the low-thermal-conductivity retention member in advance between the exhaust pipe and heat exchanger. This retention member acts as a thermal buffer that prevents heat transmission before the coolant can boil, even when the engine is stopped after high-load travel and coolant flow ceases
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 suppresses coolant boiling and enhances heat exchange efficiency by minimizing heat transfer from the exhaust pipe to the heat exchanger, even during high-load conditions, and ensures the heat exchanger is securely retained within the exhaust pipe.
Implementation Method 1
a retention member that is provided at the periphery of the heat exchanger, is formed of a ceramic sheet or an expandable graphite sheet, and is sandwiched between the exhaust pipe and the heat exchanger
Implementation Method 2
a heat exchanger that is provided inside an exhaust pipe through which exhaust gas flows, the heat exchange being formed from silicon carbide, and the heat exchanger performing heat exchange between the exhaust gas and a heat medium
Data Source
AI summary
An exhaust heat recovery unit, includes: a heat exchanger that is provided inside an exhaust pipe through which exhaust gas flows, the heat exchange being formed from silicon carbide, and the heat exchanger performing heat exchange between the exhaust gas and a heat medium; and a retention member that is provided at the periphery of the heat exchanger, is formed of a ceramic sheet or an expandable graphite sheet, and is sandwiched between the exhaust pipe and the heat exchanger, thereby retaining the heat exchanger in the exhaust pipe.