Microwave Drying of Extruded Honeycomb Structures
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Solution Overview
Problem
Microwave drying of extruded honeycomb structures faces inefficiencies due to high reflected microwave power, leading to reduced throughput and potential damage to the microwave radiation source, especially towards the end of the drying process when logs are nearly dry, resulting in underutilization of the applicator.
Innovation Solution
Implementing a cross-flow method where wet and partially dry honeycomb structures are conveyed through the applicator in opposite directions, maintaining an average moisture content between 40% and 60%, ensuring that wet structures are always present to absorb microwave energy and minimize reflected power, thus allowing the applicator to operate closer to its maximum capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If microwave power is reduced towards the end of drying to keep reflected power within acceptable limits, then reflected microwave power is controlled, but applicator utilization decreases and throughput is reduced
Solution Approach 1:
Instead of reducing microwave power to control reflected power, the patent inverts the approach by introducing wet logs into the applicator. These wet logs absorb the excess microwave energy that would otherwise be reflected, thereby controlling reflected power while maintaining high microwave power levels for continuous high-speed drying and high applicator utilization
Solution Approach 2:
The patent converts the harmful reflected microwave power into a beneficial drying mechanism by using wet logs as energy absorbers. The reflected power that would normally cause inefficiency and potential damage is instead absorbed by the wet logs, which use this energy to evaporate moisture, thereby converting a harmful effect into a useful drying function
2Device complexity
If conventional heat-based oven drying is used, then equipment complexity is reduced, but drying rate decreases and process time increases
Solution Approach 1:
The patent replaces the mechanical thermal conduction system of conventional oven drying with an electromagnetic field-based microwave heating system. This substitution enables direct internal heating of the logs through microwave energy absorption by water molecules, achieving much faster drying rates while maintaining relatively simple equipment configuration
Solution Approach 2:
The patent utilizes the phase transition of water from liquid to vapor during microwave heating. The microwave energy directly heats the water within the logs, causing rapid evaporation and moisture removal, which is the fundamental mechanism enabling the high drying rates achieved in the microwave drying process
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
This approach reduces reflected microwave power, enhances drying efficiency, increases throughput by 15%, and optimizes the use of microwave energy, preventing damage to the radiation source while maintaining consistent input power across all applicators.
Implementation Method 1
microwave radiation is used for drying honeycomb structures
Implementation Method 2
the honeycomb structure or 'log' is heated directly through the interaction of the microwave energy with the water in the log
Implementation Method 3
The amount of microwave power dissipation is generally proportional to the water (moisture) content in the log. For example, a wet log (e.g., a newly extruded log) will generally absorb more power than a dry log
Implementation Method 4
The microwave radiation that is not absorbed by the honeycomb structure is either absorbed by other materials in the applicator or reflected back to the generator
Data Source
AI summary
Systems and methods for efficient microwave drying of extruded honeycomb structures are disclosed. The methods include conveying first and second sets of honeycomb structures in opposite directions through multiple applicator cavities. Each honeycomb structure has a moisture content MC, and the honeycomb structures within each cavity define an average moisture content MCA between 40% and 60% therein. The methods include irradiating the first and second sets of honeycomb structures within the cavities with microwave radiation having an amount of input microwave power PI that results in an amount of reflected microwave power PR from the honeycomb structures, where PR<(0.2)PI. This allows for a relatively high microwave power to be maintained in each cavity. Batch microwave drying methods are also disclosed.