Drying with dielectric energy

Subsequent to freeze stabilization, wet books can be thawed and air dried with or without interleaving or they can be vacuum dried in heated chambers (5). The moisture in frozen books can be sublimed by freeze drying (10) or removed by a vacuum/thaw/outgassing process (8), with microwave energy (6, 14), with dielectric energy (6), or by solvent extraction with or without vacuum assistance (5). 

The successful application of either microwave or dielectric energy for drying requires that water, as it is evaporated, be removed from the paper and book. Air with low relative humidity is forced through the chamber to facilitate water vapor removal from the object. Since interaction of the water molecules at different locations in the chamber may not be uniform, each frozen flood-damaged item was inverted and partially rotated between each burst of energy. Radiation leakage from both types of equipment is possible therefore, special precautions for com-... 

There are three ways in which microwave and dielectric energy may be combined with conventional drying methods, as illustrated in Figure 13.4. 

Product cannot be produced by any other way. Again, the careful control of temperature combined with the unique manner in which microwave and dielectric energy couple into materials allows the drying of extremely thermolabile materials with no damage to the product. Occasionally, a unique beneficial effect may be obtained, such as the slight puffing of the pasta noodles when they are microwave dried. This allows them to be cooked more quickly. 

Drying processes, means of energy supply (convection, contact, radiation, high frequency (dielectric), microwave, and freeze dryers, or dryers with eombined energy usage, etc.)... 

Heating and drying with microwave and dielectric energy is distinctly different from conventional... 

Dielectric and microwave energy of the appropriate frequency can transfer energy directly via radiation (2,3,4) without an intermediate transfer medium. This energy transfer and application can raise the temperature of an object more uniformly than the conduction and convection methods. More specifically, use of either dielectric (5) or micro-wave (6) radiation to interact directly with water molecules had the potential to accelerate the thawing and drying of our frozen, flood-damaged library and archival materials. 

By applying microwave energy to pharmaceutical systems to be dried, dielectric materials such as water and solvents with dissolved salts absorb the energy thereby increasing molecular vibration. This movement is in turn converted to friction resulting from interactions with neighboring molecules, solvent temperature increases and ultimately vaporizes, and drying is affected. ... 

The activation energy for the a-relaxation decreases from 46 kcal/mole in the dry polymer to 18 kcal/ mole at 8.7% water with most of the decrease coming below 0.88% water. (12) The increase in the dielectric constant associated with the a-relaxation is greater when water is present. This Indicates that water molecules are bonded to the amide groups and participate in the motion of chain segments. 

---