Differences Between Radio Frequency
and Conventional Heating
Conventional heating (i.e. conduction, convection, radiant) has a heat source on the outside and relies on transferring the heat to the surface of the material and then conducting the heat to the middle of the material. Radio Frequency heating is different; it heats at the molecular level so it heats from within the material and heats the middle as well as the surface.
A conventionally dried product is hot and dry on the outside and cold and wet on the inside. This is not efficient because the dry outer layer acts as an insulating barrier and reduces the conduction heat transfer to the middle of the product. This dry outer layer can cause quality problems, such as surface cracking, a skin on coatings and uneven solids dispersion through wicking of sizing and additives from the middle to the surface.
With Radio Frequency drying, the heating is from within so there is no hot, dry outer layer. The product is heated throughout so the water in the middle will be heated and will move to the surface. In general, because of the heat losses at the surface, Radio Frequency dried products are hot and dry on the inside and cooler and wetter on the outside. The combination of two technologies, using the Radio Frequency heating to heat the inside and move the water to the surface where conventional methods are effective at removing it, offers some great potential benefits.