Electromagnetic heating

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Solution Overview

Problem

Conventional microwave ovens fail to provide uniform heating for irregularly shaped objects, leading to temperature differences and hotspots, which is particularly problematic for heating or defrosting organs and foods of non-spherical shapes.

Innovation Solution

The use of multiple microwave feeds operating at different frequencies, with adjustable power levels and field adjusting elements within the cavity, to ensure uniform energy distribution and absorption across the object, while also considering changes in the object's impedance during heating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional microwave ovens are used for heating, then heating speed is improved, but temperature uniformity deteriorates

Engineering Contradiction:

Improveheating speedVSAvoidtemperature uniformity

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

The microwave heating system is segmented into multiple independent feed sources (at least two feeds) that can be controlled separately. Each feed targets different regions of the object with optimized power levels and frequencies, allowing simultaneous heating of multiple zones while maintaining overall temperature uniformity across the entire object.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the object receive customized microwave energy treatment through the multiple feeds. Each feed is configured with specific power levels, frequencies, and spatial positions to address the unique heating requirements of different object regions, particularly adapting to irregular shapes where uniform heating is challenging.

Inventive Principle:

Principle #3Local quality

2Productivity

If heating power is increased to improve heating speed, then productivity is improved, but thermal runaway and hotspots worsen

Engineering Contradiction:

Improveheating speedVSAvoidthermal runaway

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The microwave heating system dynamically adjusts the power levels of multiple feeds during the heating process. The controller monitors heating progress and modifies the power distribution among feeds in real-time, increasing power to cooler regions and reducing power to warmer regions, thereby maintaining uniform heating while preventing thermal runaway and enabling faster overall heating.

Inventive Principle:

Principle #15Dynamics

3Temperature

If multiple feeds at different frequencies are used to improve temperature uniformity, then device complexity increases

Engineering Contradiction:

Improvetemperature uniformityVSAvoidheating system complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The microwave heating system employs multiple feeds that operate at different frequencies, with each feed capable of performing multiple functions: heating different object regions, penetrating different material depths, and operating at optimized frequencies for specific dielectric properties. This multi-functionality allows a single heating system to handle diverse heating scenarios and irregular object shapes effectively.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Adaptability or versatility

If heating is performed on irregularly shaped objects, then versatility is improved, but temperature uniformity deteriorates

Engineering Contradiction:

Improveobject shape adaptabilityVSAvoidtemperature uniformity

Core Design Contradiction:

Adaptability or versatilityVSTemperature

Solution Approach 1:

The heating system adapts to irregular object shapes by configuring multiple feeds with different power levels, frequencies, and spatial positions tailored to each object's geometry. Each feed targets specific regions of the irregular shape, delivering customized energy distribution that compensates for geometric variations and ensures uniform heating across the entire object surface and volume.

Inventive Principle:

Principle #3Local quality

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 achieves uniform temperature distribution within 50°C across 80-90% of the object's volume, reducing the risk of thermal runaway and improving heating efficiency, as demonstrated by successful defrosting and cooking of irregularly shaped items like a cow liver.

Implementation Method 1

The microwave oven is a ubiquitous feature in modern society... electromagnetic heating... microwave energy is deposited uniformly in the object

Methodology Applied

Scientific EffectDielectric heating: Dielectric Heating

Implementation Method 2

slow absorption of heat... uniform energy distribution and absorption across the object

Methodology Applied

Scientific EffectElectromagnetic radiation absorption: Absorption (EM radiation)

Implementation Method 3

allow the heat deposited in a hot spot to diffuse to surrounding regions and heat them by conduction

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 4

Due to convection from the object, it is not a serious option for cooking or heating much above room temperature

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentUS11523474B2Electromagnetic heating

Publication Date: 2022.12.06 JOLIET 2010 LTD

AI summary

An electromagnetic heater for heating an irregularly shaped object, including:a cavity within which an object is to be placed;at least one feed which feeds UHF or microwave energy into the cavity; anda controller that controls one or more characteristics of the cavity or energy to assure that the UHF or microwave energy is deposited uniformly in the object within ±30% over at least 80% of the volume of the object.