Microwave Heating Sheet With Expandable Insulating Cells
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Solution Overview
Problem
Microwave ovens tend to cook dough-based food items unevenly and fail to achieve a balanced heating with a browned, crisp crust, necessitating improved materials and packages for heating, browning, and crisping.
Innovation Solution
A microwave energy interactive heating sheet comprising at least two plies of microwave energy interactive insulating material, with susceptor films and moisture-containing layers forming expandable insulating cells that inflate upon microwave exposure, enhancing thermal insulation and heat transfer to the food item.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If microwave energy is used to heat dough-based food items, then heating speed is improved, but heating uniformity deteriorates
Solution Approach 1:
The heating sheet is divided into multiple plies (at least two plies of microwave energy interactive insulating material) with different functional layers. Each ply contains susceptor films, moisture-containing layers, and polymer film layers arranged in segments that create expandable insulating cells. This segmentation allows different regions of the sheet to perform different functions: some areas generate heat while others provide insulation, resulting in more uniform heat distribution across the food item.
Solution Approach 2:
Different regions of the heating sheet have different thermal properties. The susceptor films are strategically positioned to create localized heat generation zones, while the expandable insulating cells provide localized insulation. The moisture-containing layers are distributed to control steam generation in specific areas. This local variation in thermal properties enables simultaneous heating and browning in different regions of the food item.
2Ease of operation
If conventional microwave heating is used, then heating convenience is improved, but crust browning and crisping capability deteriorates
Solution Approach 1:
The heating sheet acts as an intermediary between the microwave energy source and the food item. It contains susceptor films that absorb microwave energy and convert it to heat, then transfer this heat to the food. The expandable insulating cells serve as a thermal mediator, retaining heat generated by the susceptors and directing it to the food crust, enabling browning and crisping while maintaining the convenience of microwave operation.
Solution Approach 2:
The heating sheet is a composite material structure combining multiple components: susceptor films (for microwave energy absorption), moisture-containing layers (for steam generation), and polymer film layers (for structural integrity and insulation). This composite structure enables the sheet to simultaneously perform multiple functions: heating, insulating, steam generation, and heat retention, thereby achieving crust browning and crisping in a microwave oven.
3Loss of energy
If expandable insulating cells are added to the heating sheet, then thermal insulation is improved, but device complexity increases
Solution Approach 1:
The heating sheet merges multiple functions into a single integrated structure. The susceptor films, moisture-containing layers, and polymer film layers are combined in at least two plies to form expandable insulating cells. These cells serve dual purposes: they provide thermal insulation to retain heat generated by the susceptors, and they create a lofted structure that elevates the food item for improved heat circulation. This merging of functions reduces the need for separate heating and insulating components.
Solution Approach 2:
The heating sheet utilizes parameter changes in response to microwave energy exposure. The expandable insulating cells transition from a compressed state to an expanded state when exposed to microwave energy and moisture heat. This parameter change (volume expansion) provides thermal insulation without requiring a complex rigid insulating structure. The cells automatically adjust their insulation properties based on the heating conditions.
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 heating sheet provides improved heating, browning, and crisping of dough-based food items by maintaining thermal energy and transferring heat effectively, resulting in a more evenly cooked and crispy crust.
Implementation Method 1
a susceptor film comprising a microwave energy interactive material supported on a first polymer film layer
Implementation Method 2
a moisture-containing layer superposed with the microwave energy interactive material, wherein the expandable insulating cells are operative for inflating when the microwave cooking pouch is exposed to microwave energy by causing air and water vapor trapped in the cells to expand
Data Source
Figure 1A~1C
Figure 1D~1E
Figure 1F~1H
AI summary
A microwave energy interactive heating sheet (400) includes at least two susceptor layers (404, 412) and a plurality of expandable insulating cells (420). At least some of the expandable insulating cells inflate when exposed to microwave energy.