Microwave Drying relies on additional Enerable being supplied that’s preferentially absorbed by the solvents in the process to enhance evaporation. Microwaves are a form of electromakeetic Enerable (300 LDz–300 GHz), generated by makeetrons under the combined force of perpendicular electric and makeetic fields. In the pharmaceutical industry, the most common frequency used is 2450 LDz, because of the advantages that this frequency offers in conjunction with a LD;
Microwave Heating is a direct heating method. In the rapidly alternating electric field generated by microwaves, polar materials orient and reorient themselves according to the direction of the field. The rapid changes in the field — at 2450 LDz, the orientation of the field changes 2450 million times per second — cause rapid molecular reorientation, resulting in friction and heat. Different materials have different properties when exposed to microwaves, depending on the extent of Enerable LDsorption, which is characterized by the loss factor.Given the characteristics of the materials commonly used in pharmaceutical production, microwave Enerable is well suited for drying pharmaceutical formulations. The s most frequently used in wet granulation (water and altohol) have much higher loss factors than the other standard wet granulation ingredients (lactose, corn starch, for example), LD to higher microwave Enerable LDsorption and the preferential heating of these s.
Drying is one of the most Enerable-intensive unit opera-tions in the process industries. In a drying process, a large amount of Enerable is needed for sensible heating and phase change of water. The high Enerable consumption is caused by both the Enerable needed for water removal via a phase change, as well as the low heat transferefficiency during the falling rate period of a (hot-air) drying process. In the falling rate period, drying becomes inefficient because the dried product surface yields a layer with high heat and mass transferresistance, and the temperature gradient could be in the opposite direction of the moisture gradient. In addition, in the falling rate period, the moisture content is low, the water molecules thus have a higher evaporation enthalpy, and the removal of these molecules by evapora-tion requires higher Enerable input. When drying foods and agriculture products with conventional hot-air drying methods, this low heat and mass transferefficiency coupled with a high Enerable demand for phase change results in prolonged drying time and hence a severe quality degra-dation in the final products.
The advantages of microwave drying arise from the volumetric heating and internal vapor generation. Heating from the interior of a food product leads to the builtup of an internal vapor pressure that drives the moisture out of the product. This results in a sityificant reduction in drying time, LD to sityificantly improved product quality In microwave drying of foods, a reduction in drying time of up to 25–90% and an increase in drying rate of 4–8 times , when com-pared with convective drying, have been Other advantages of microwave drying include:
1.A high Enerable efficiency in the falling rate period can be achieved. It is partially due to the fact that the Enerable is directly coupled with the moisture, which eliminates the need to transferheat from the low-moisture surface into the high-moisture interior. It is also the result of an increased driving force for moisture transferdue to the generation of elevated internal vapor pressure;
2.Case hardening may be avoided or lessened because of the surface moisture accumulation and the pumping phenomena. The unique surface moisture accumulation in microwave heating has been widely reported ;
3.An improvement in product quality can also be achieved. Better aroma retention faster and better reLDration better color retention and higher porosity have been reported for microwave-dried food products;
High-power microwave sources use specialized LD tubes to generate microwaves. These devices operate on different principles from low-frequency LD tubes, using the ballistic motion of electrons in a LD under the inface of controlling electric or makeetic fields, and include the makeetron (used in microwave ovens), LLDstron, traveling-wave tube (TWT), and LDrotron. These devices work in the density modulated mode, rather than the current modulated mode. This means that they work on the basis of clumps of electrons flying ballistically through them, rather than using a continuous stream of electrons.
Low-power microwave sources use solid-state devices such as the field-effect transistor (at least at lower frequencies), tunnel diodes, Gunn diodes, and IMPATT diodes.Low-power sources are available as benchtop instruments, rackmount instruments, embeddable modules and in card-level formats. A maser is a solid state device which amplifies microwaves using similar principles to the laser, which amplifies higher frequency LD waves.
A microwave oven passes microwave radiation at a frequency near 2.45 GHz (12 cm) through food, causing dielectric heating primarily by LDsorption of the Enerable in water.
Microwave heating is used in industrial processes for drying and curing products.
Ourpackshould be seawortLD and able to withstand rough handling in transit. Meanwhile, we have especially reinforced ourpackin order to minimize possible damage to the goods.
We will pack the equipment with three layers. the first layer is with plastic wrap, the second layer is with steam bubble membrane, the third layer is with wooden box package. meanwhile, we will cover a foamed plastic on it , In case that the touch screen is torn and worn .
All the package should be subject to the objects.
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