Segmented Heaters for Honeycomb Substrate Thermal Management
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Solution Overview
Problem
Existing honeycomb heating devices for exhaust gas purification face challenges in maintaining temperature consistency and durability due to slight cracks from vibrations, and require high shape precision for efficient heat transfer, which is difficult to achieve, especially in curved structures.
Innovation Solution
A honeycomb type heating device with a pillar-shaped substrate and multiple resistance heating heaters disposed adjacently on the outer circumferential face, ensuring a wide face-contact area for efficient heat transfer, and designed to withstand slight cracks and thermal stress, with heaters connected in series or parallel to handle high voltage and featuring an insulating function to prevent short-circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single tubular resistance heating heater is disposed to surround the circumferential wall of the honeycomb structure, then heat transfer efficiency is improved, but the heater is easily broken by thermal stress and requires extremely high shape precision
Solution Approach 1:
The single tubular heater is divided into multiple segment heaters arranged adjacently around the honeycomb structure. Each segment heater is independently supported by the holder, allowing thermal expansion and contraction without generating excessive stress. This segmentation maintains heat transfer efficiency while improving reliability by preventing heater breakage.
Solution Approach 2:
A holder is introduced as an intermediary component between the segment heaters and the honeycomb structure. The holder supports the segment heaters at multiple positions and provides a buffer for thermal stress, enabling efficient heat transfer to the honeycomb structure while protecting the heaters from breaking due to thermal expansion and contraction.
2Loss of energy
If the inner circumferential face of the tubular resistance heating heater comes into face-contact with the outer circumferential face of the honeycomb structure, then heat transfer efficiency is improved, but extremely high shape precision is demanded making production difficult
Solution Approach 1:
The continuous tubular heater is segmented into multiple discrete segment heaters. These segments can be manufactured with standard precision and then assembled around the honeycomb structure. The gaps between segments do not significantly impact heat transfer efficiency while eliminating the need for extremely high shape precision in manufacturing.
Solution Approach 2:
The holder structure allows the segment heaters to be positioned and secured in place without requiring precise pre-manufacturing of the entire assembly. The modular design enables flexible adjustment and assembly, reducing manufacturing precision requirements while maintaining effective thermal contact with the honeycomb structure.
3Temperature
If current is supplied through the honeycomb structure to radiate heat, then the honeycomb structure can be heated, but the temperature is degraded or temperature distribution is changed by slight cracks from vibration
Solution Approach 1:
The holder acts as an intermediary support structure that positions the segment heaters around the honeycomb structure without requiring electrical connection through the honeycomb. This eliminates the problem of temperature degradation and distribution changes caused by cracks in the honeycomb structure, while still achieving effective heating through radiative heat transfer from the segment heaters.
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 device efficiently increases the temperature of the honeycomb substrate to the catalyst activating temperature, ensuring effective exhaust gas purification even when part of the heaters are broken, and prevents thermal stress damage, allowing for high-precision assembly and efficient heat transfer without requiring extreme shape precision.
Implementation Method 1
each heater is a resistance heating heater which radiates heat by a current supplied thereto
Data Source
AI summary
The honeycomb type heating device includes: a pillar-shaped honeycomb substrate which includes a porous partition wall defining a plurality of cells extending from one end face to the other end face and a circumferential wall surrounding the partition wall; and a plurality of heaters which are disposed adjacently in a circumferential direction of an outer circumferential face that is an outer surface of the circumferential wall, on the outer circumferential face. Each heater is a resistance heating heater which radiates heat by a current supplied thereto, each heater comes into face-contact with the outer circumferential face, and a ratio of a total area of a portion covered by the heaters of the outer circumferential face with respect to the entire area of the outer circumferential face is 50 to 100%.