Fixed radial anode drum dryer
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Solution Overview
Problem
Existing dielectric heating technologies for drying clothes, particularly at higher frequencies like microwave frequencies, are less efficient compared to lower RF frequencies due to factors such as ion rotation mechanisms and parasitic capacitance issues.
Innovation Solution
A clothes dryer apparatus utilizing a rotating conductive drum as a cathode with spatially fixed, non-rotating radial anodes that create an electric field for dielectric heating, minimizing parasitic capacitance and allowing for efficient RF capacitive coupling at lower RF frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If higher frequency electromagnetic fields (microwave frequencies) are used for dielectric heating, then the heating mechanism works through dipole rotation, but the heating efficiency decreases compared to lower RF frequencies
Solution Approach 1:
The patent changes the operating frequency parameter from microwave frequencies (>800 MHz) to lower RF frequencies (1 MHz to 50 MHz). This parameter change shifts the dominant heating mechanism from dipole rotation to ion drag, which is more efficient for heating conductive liquids and moist materials like clothes. The lower frequency allows ions to be dragged more slowly back and forth, striking liquid molecules and transferring kinetic energy more effectively into thermal energy.
2Loss of energy
If conventional microwave heating is used, then electromagnetic waves form in a resonant cavity, but parasitic capacitance issues reduce heating efficiency
Solution Approach 1:
The patent extracts the heating elements (anodes) from a complex resonant cavity structure and positions them directly against the clothes load. By using a simplified drum-shaped capacitor structure without a traditional microwave cavity, the patent eliminates parasitic capacitance issues associated with cavity walls and achieves more direct energy transfer to the load.
3Reliability
If rotary RF heating capacitive structures are used, then specialized connections to anodes inside the drum are required, but this increases device complexity
Solution Approach 1:
Instead of having the anodes rotate with the drum (which would require complex rotary connections), the patent inverts the approach by keeping the anodes stationary and fixed to the drum exterior. The drum rotates while the anodes remain stationary, eliminating the need for complex rotary electrical connections while maintaining effective capacitive coupling between the anodes and the clothes load.
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 solution achieves efficient and uniform dielectric heating of clothes by minimizing parasitic capacitance and optimizing RF energy transfer, leading to improved drying performance compared to conventional methods.
Implementation Method 1
Dielectric heating involves the heating of materials by dielectric loss. A changing electric field across the dielectric material (in this case, a load of clothes) causes energy to be dissipated as the molecules attempt to line up with the continuously changing electric field, creating friction.
Implementation Method 2
In conductive liquids such as salt water, 'ion drag' from using lower RF frequencies causes heating, as charged ions are 'dragged' more slowly back and forth in the liquid under influence of the electric field, striking liquid molecules in the process and transferring kinetic energy to them, which is eventually translated into molecular vibrations, and thus into thermal energy.
Data Source
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AI summary
The invention provides a clothes dryer apparatus comprising an electrically conductive, grounded, generally cylindrical rotatable drum (13) having a hollow interior adapted to contain a load (15) of wet clothes to be dried; characterized in that said drum (13) has a partially indented exterior surface in which at least one generally ring-shaped insulated notch (10) has been formed; positioned within each notch, an electrically conductive anode (11), coupled to each anode, a source of RF power,a plurality of air holes (30) formed in the at least one insulated notch (10), whereby water evaporated from the load (15) by the RF power is removed from the interior of the drum (13) due to the resulting air flow.