Microwave Mode Mixer for Uniform Heating
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Solution Overview
Problem
Cooking devices face challenges in preventing hotspots during cooking, especially when dealing with food items of varying dielectric properties, leading to uneven cooking and potential drying out, particularly during defrosting processes where the absorption behavior of food changes significantly.
Innovation Solution
A method involving the generation of a fixed spatial electric field distribution using electromagnetic signals, modulation of these signals, and measurement of both forward and backward electromagnetic waves to evaluate changes in absorption behavior, allowing for the determination of excitation parameters that minimize hotspot formation by adjusting the cooking process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If electromagnetic radiation is used to cook food, then cooking speed and efficiency are improved, but hotspots are created leading to uneven cooking and potential drying out
Solution Approach 1:
The patent applies dynamics by making the microwave field distribution changeable through a mode mixer (fan impeller) that swirls the electromagnetic field. This dynamic adjustment allows the system to adapt the field distribution to minimize hotspots while maintaining cooking efficiency, resolving the contradiction between fast cooking and uniform heating.
Solution Approach 2:
The patent changes physical parameters of the electromagnetic field by using a mode mixer to alter the field distribution pattern. By modifying the spatial and temporal characteristics of the microwave field, the system achieves more uniform energy distribution across the food, preventing hotspots while maintaining cooking speed.
2Productivity
If food is defrosted using electromagnetic radiation, then defrosting speed is improved, but thermal outliers occur due to abrupt changes in absorption behavior
Solution Approach 1:
The patent implements feedback by monitoring the dielectric properties of food during defrosting and adjusting the microwave power accordingly. This closed-loop control prevents thermal outliers by responding to changes in absorption behavior, maintaining temperature control stability while achieving fast defrosting.
Solution Approach 2:
The patent uses periodic action by applying microwave radiation in controlled cycles with duty cycles less than 100%. This pulsed approach allows heat distribution to catch up between pulses, preventing thermal outliers during the sensitive defrosting phase while maintaining overall defrosting speed.
3Manufacturing precision
If turntable is used to move food in electromagnetic field, then hotspot formation is reduced, but device complexity increases
Solution Approach 1:
The patent replaces the mechanical turntable system with a mode mixer (fan impeller) that achieves field distribution through electromagnetic means rather than mechanical movement. This substitution reduces mechanical complexity while maintaining the benefit of reduced hotspot formation through field swirling.
4Manufacturing precision
If mode mixer is used to swirl electromagnetic field, then hotspot formation is reduced, but device complexity increases
Solution Approach 1:
The patent applies universality by using the fan impeller (mode mixer) for dual purposes: both for air circulation in conventional cooking and for electromagnetic field swirling in microwave cooking. This multi-functionality reduces overall device complexity while achieving cooking uniformity through field distribution control.
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 effectively prevents hotspots by allowing for precise control of electromagnetic radiation distribution, ensuring even cooking and uniform heating or defrosting, even with foods of different dielectric properties.
Implementation Method 1
a microwave source, such as a magnetron or a solid state microwave generator ('Solid State Cooking'—SSC), via which electromagnetic radiation that is fed into the cooking chamber to thus also cook the food to be cooked is generated
Implementation Method 2
When cooking the food to be cooked using electromagnetic radiation
Implementation Method 3
it is known that a fan impeller which is present anyway acts as a so-called mode mixer to swirl the generated electromagnetic field in the cooking chamber to accordingly reduce or avoid hotspots
Implementation Method 4
so-called thermal outliers may occur, as the absorption behavior of the food to be cooked with regard to electromagnetic radiation changes abruptly/strongly when the food to be cooked is no longer in the frozen state
Implementation Method 5
the absorption behavior of a frozen food to be cooked is negligible compared to a defrosted food to be cooked, but changes strongly, in particular exponentially, in the 0° C. range
Data Source
AI summary
Analyzing the absorption behavior of an object includes: generating at least one electromagnetic signal such that a fixed spatial electric field distribution is produced; modulating the electromagnetic signal with a waveform to generate a modulated signal which is emitted as a forward electromagnetic wave towards the object to be analyzed; measuring at least one wave quantity of the forward electromagnetic wave; receiving a backward electromagnetic wave; measuring at least one wave quantity of the backward electromagnetic wave; and evaluating the measured wave quantity of the backward electromagnetic wave and the measured wave quantity of the forward electromagnetic wave by respectively transforming the measured wave quantities to obtain a spectrum of the respective transformation, wherein the spectrum assigned to the forward electromagnetic wave is compared with the spectrum assigned to the backward electromagnetic wave to determine deviations of the spectra from each other based on which the object is characterized.