Microwave Liquid-Bath Heating for Uniform Temperature Control
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Solution Overview
Problem
Existing microwave heating systems face challenges in efficiently and safely applying microwave energy on a commercial scale for rapid thermal processing of thermally sensitive articles, limiting their application in pasteurization and sterilization processes.
Innovation Solution
A heating system that uses a combination of microwave energy and a liquid medium bath, with fluid distribution and temperature control systems, and sequential processing sections to maintain temperature profiles and pressure conditions for efficient heating and cooling of articles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If microwave energy is used for rapid heating, then heating speed is improved, but temperature uniformity deteriorates
Solution Approach 1:
The system introduces localized cooling zones with nozzles positioned at specific locations (inlet, outlet, and intermediate positions) within the heating chamber. Each nozzle provides targeted cooling to specific areas experiencing excessive temperature, creating non-uniform cooling distribution that compensates for non-uniform heating and achieves overall temperature uniformity
Solution Approach 2:
A liquid cooling medium is introduced as an intermediary substance between the microwave energy source and the article being heated. The liquid absorbs excess microwave energy and heat, then dissipates it through the nozzle system, acting as a buffer that mediates between rapid microwave heating and temperature control requirements
2Temperature
If liquid cooling medium is added to control temperature, then temperature control is improved, but system complexity increases
Solution Approach 1:
The liquid cooling system serves multiple functions simultaneously: it cools overheated areas, removes excess microwave energy from the chamber, prevents arcing and overheating of components, and maintains safe operating temperatures. This multi-functionality reduces the need for separate cooling systems and simplifies the overall design despite the added temperature control capability
Solution Approach 2:
The system uses the article being heated as part of the cooling mechanism. The article is positioned to be partially submerged in or exposed to the liquid cooling medium, allowing it to self-regulate its own temperature by direct contact with the cooling liquid, reducing the need for complex external cooling apparatus
3Manufacturing precision
If articles are submerged in liquid bath, then heating uniformity is improved, but processing time increases
Solution Approach 1:
The system implements periodic or intermittent cooling through the nozzle system rather than continuous submersion. The nozzles can be activated in pulses or at specific intervals during the microwave heating process, providing cooling only when and where needed, thus maintaining heating uniformity while minimizing the time articles spend in a cooled state
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 system enables uniform and predictable heating of articles, ensuring consistent temperature control and safety, suitable for pasteurization and sterilization of packaged foodstuffs and pharmaceuticals, while minimizing thermal variability and equipment limitations.
Implementation Method 1
heating the article in the carrier, wherein the article is at least partially submerged in the liquid bath during the heating, and wherein at least a portion of the heating is performed using microwave energy
Implementation Method 2
adding fluid into and removing fluid from at least one location in the heating chamber to maintain a temperature profile across the heating chamber
Implementation Method 3
at least one heat transfer device for one or more of heating and cooling the fluid
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A process for heating articles in a heating system includes passing an article in a carrier through a heating chamber that is at least partially filled with a liquid medium to form a liquid bath. The process further includes heating the article in the carrier by at least partially submerging the article into the liquid bath during heating, the heating being performed, at least in part, using microwave energy. The process further includes one or more of adding fluid into and removing fluid from at least one location in the heating chamber to maintain a temperature profile across the heating chamber. In one implementation, the temperature of the liquid bath at an inlet area of the heating chamber is at least 10°C cooler than a temperature of the liquid bath at an outlet area of the heating chamber.