Applications Which Can Benefit By Utilizing Macrowave™ Heating
Conventional heating relies on conduction to transfer heat to the center of the material which can be a slow process and cause undesireable surface effects. By contrast, RF heating occurs simultaneously throughout the thickness of the material providing fast and uniform heating.
Some of the many applications which employ Macrowave™ heating are listed below:
- Deinfestation of meal, flour, grains, seeds, beans, etc.
- Drying hydrophilic foams
- Drying of textile yarns, fabrics, and garments
- Post-baking drying and moisture control of biscuits & crackers and other food products
- Drying of ceramic greenware prior to firing
- Drying of water-based coatings, inks and adhesives on webs in paper manufacturing and converting
- Heat treating, deinfestation and pasteurization of bagged materials
- Drying and moisture leveling of webs, sheets, & boards
- Drying and moisture leveling of bulk materials
- Preheating of thermoset sheet molding compounds prior to molding
- Drying of fiberglass yarn and chopped strand
- Drying water-based inks
- Sterilization of medical wastes
- Drying filter cake
- Pasteurization of food products
Following are the advantages of Macrowave™ heating.
Speed and Uniformity:
Heating occurs instantly and uniformly throughout the mass of a homogeneous material. No temperature differential is required to force heat via conduction from the surface to the center as in convection or infrared heating processes.
Heating will occur selectively in those areas where heat is needed because water, unpolymerized synthetic resins and uncured latices are much more responsive to RF energy than most other dielectric materials.
Because wetter areas absorb more RF power than dryer areas, more water is automatically removed from wet areas resulting in a more uniform moisture distribution.
The applicator, or electrode section, is slightly wider than the load itself. Length will be a small fraction of the length of the convection dryer required to do the same work. Special applicator designs may be used, multi-pass, multi-zone, arched, inclined, or vertical.
The load may be supported by electrodes or conveyed under or between them. Self-supporting webs or strands need not touch anything, thus avoiding surface marking and contamination.
Power is consumed primarily in the work load. There are no losses from heating masses of cast iron or huge volumes of hot air -- no long warm up or cooling times are required. Power is consumed only when the load is present and only in proportion to the load.
Power control is accurately metered and may be recorded. A meter constantly displays the amount of power being applied to heat the product.
The full range of power control from minimum to maximum is traversed in seconds. Adjustments take effect immediately. Thermal lag time is zero. Automatic changes in power level due to physical properties or size of load are instantaneous.
When a dielectric material is polymerized, dried, or cured, its loss factor is lowered, reducing its response to RF energy. RF heating is, therefore, automatically limited to the level required to complete the process.
The RF heater is actually a very sensitive moisture meter. Its power output is a measure of the average moisture content of the load. Changes in power output, as indicated by the plate current meter, can be used to trigger alarms or provide feedback signals for process control.
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