Drying constant microwave power

Three different temperature stages are observed at constant microwave power in most microwave-assisted drying processes (Clary et al., 2005 Feng et al., 1999 Ahme et al., 2007 Duan et al., 2010b) ... 

Variable microwave power means that the microwave energy is emitted in a pulsed mode by turning on-off the microwave power during the drying process, or that the microwave emission is declining continually with time. Compared with the constant power mode, the variable microwave power mode is able to stabilize the temperature of the sample at a value that depends on the microwave power used, the duration of the power-on and power-off periods, and the other operating conditions, which indicates that thermal runaway can be inhibited in the variable microwave power mode. 

P., 2007. Microwave convective drying of plant foods at constant and variable microwave power. Drying Technol. 25 1149-1153. 

Some dryers also provide heat energy to the powder mass by a jacketed vessel, thereby increasing overall heat transfer. Moisture can be removed via vacuum or hot air fluidization depending on the design of the dryer allowing for improved evaporative drying and vapor mass transfer. Fig. 13 shows the relationship between power input (W) and first-order drying rate constant in a microwave fluid-bed processor. ... 

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