RF and Thermal Oven Heating with Impedance-Based Time Estimation
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Solution Overview
Problem
Conventional food heating systems either lack efficiency in cooking time, even heating, or fail to produce desirable Maillard reactions for browning and crisping, highlighting the need for a more effective heating method that combines speed and browning capabilities.
Innovation Solution
A heating system that integrates a radio frequency (RF) heating system with a thermal heating system, utilizing a solid-state RF signal source and a variable impedance matching network to dynamically control the heating process, allowing for simultaneous operation of RF and thermal heating sources to achieve deeper penetration and more even heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional microwave heating is used, then cooking speed is improved, but browning and crisping capability deteriorates
Solution Approach 1:
The patent combines RF heating and convection heating systems into a single oven cavity, allowing both heating modes to operate simultaneously or sequentially. The RF system provides rapid bulk heating while the convection system enables browning and crisping, thus merging the advantages of both systems to resolve the contradiction between cooking speed and browning capability.
2Object-generated harmful factors
If convection heating is used, then browning capability is improved, but cooking time increases
Solution Approach 1:
The patent merges RF heating and convection heating systems to allow simultaneous operation. The RF system rapidly heats the bulk of the food while the convection system browns the surface, thus achieving both speed and browning capability, resolving the contradiction between cooking time and browning capability.
3Device complexity
If conventional oven heating is used, then construction simplicity is improved, but cooking speed deteriorates
Solution Approach 1:
The patent combines RF heating elements and convection heating elements within a single oven cavity, creating a multi-functional system that achieves fast cooking speeds through RF heating while maintaining a relatively simple integrated structure, thus resolving the contradiction between construction simplicity and cooking speed.
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 combined RF and thermal heating system achieves faster and more even cooking, with the RF energy penetrating deeper into food loads, enabling browning and crisping not typically achieved by conventional microwave ovens, while maintaining control over cooking time and energy distribution.
Implementation Method 1
The cavity magnetron produces electromagnetic energy that is directed into the oven cavity through the waveguide. The electromagnetic energy (or microwave radiation) impinges on the food load to heat the outer layer of the food.
Implementation Method 2
Electric current is passed through the heating element(s), and the element resistance causes each element and ambient air around the element to heat up.
Implementation Method 3
the fan assembly is used to circulate air warmed by the heating element throughout the oven cavity, resulting in a more even temperature distribution throughout the cavity
Data Source
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AI summary
An embodiment of a heating system includes a cavity configured to contain a load, a thermal heating system, and an RF heating system. The RF heating system includes a system controller, an RF signal source, one or more electrodes that receive an RF signal from the RF signal source and radiate resultant electromagnetic energy into the cavity, and a variable impedance matching network coupled between the RF signal source and the one or more electrodes. The system controller may monitor an impedance state of the variable impedance matching network to identify the occurrence of a change point. The system controller may estimate the mass of the load and a time and/or energy requirement for cooking the load based on the change point. The system controller may take action by turning off the RF heating system and/or thermal heating system when the time or energy requirement has been met.