Microwave and Dielectric Drying

Schiffmann, Robert F.

doi:10.1201/9780429289774-11

Cited by 36 publications

(23 citation statements)

References 1 publication

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“…Therefore, the control of temperature must be taken into account when designing an alternative drying method to sun drying. Microwave drying has great potential in this respect because this technique allows a good control of the process temperature, an increase in energy efficiency and a reduction of its carbon footprint [11], [18], [19].…”

Section: Introductionmentioning

confidence: 99%

Microwave drying of corn seeds: Effect of Temperature on Drying Time, Energy Consuption and Germination Rate

Moreno

Maqueda

Ballesteros

et al. 2019

Proceedings 17th International Conference on Microwave and High Frequency Heating

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Previous studies on the microwave drying of corn seeds have shown that the process parameters employed play a very important role in determining the properties and quality of this grain (Gürsoy et al, 2013). Among these parameters, the drying temperature has a fundamental role (Nair et al, 2011). The main objective of this work is to evaluate the effect of temperature on drying time, energy consumption and germination rate of corn seeds after they have been dried with microwave energy. To achieve the proposed objective, the drying process of these seeds was carried out in a rotating turntable domestic microwave oven (LACOR Model 69330), with a capacity of 30 liters and a total output power of 900 W, fitted with a PID temperature controller Eurotherm 3216 L. In this oven, 100 g of corn seeds, with an initial humidity of approximately 20%, was heated up to 3 drying temperatures (35, 55 and 75 °C). The seeds were weighed every 30 minutes and the drying process was considered completed when a humidity of 12 % was obtained. For each drying temperature studied, the experiments were carried out in duplicate. In each experiment, the electrical energy consumption was measured using a FLUKE 1735 energy analyzer. A sample of the dried seeds was subject to germination tests in a petri dish using filter paper and a volume of distillate water of 20mL to achieve sufficient humidity for them to sprout. Table 1 shows the average values obtained from the variables evaluated for each drying temperature. Table 1. Results of the microwave drying experiments of the corn seeds at different temperatures and their germination tests. Drying temperature (ºC) Drying time to reach a humidity of 12% (min) Energy consumption (Wh) Germination rate (%) 35 345,0 880,3 90,0 55 118,5 330,0 81,3 75 73,5 183,9 12,0 As can be seen in Table 1, the temperature exerts a significant influence on the drying process and the germination rate of the corn seeds. An increase in the drying temperature causes a simultaneous decrease in drying time (∿ 78%) and in energy consumption (∿ 79%), which are very positive aspects. However, there is also an unacceptable decrease (∿ 87%) in the germination rate of the corn seeds. References Gürsoy, S., Choudhary, R., Watson, D.G. Int. J Agric. & Biol. Eng., 2013, 6, 1, 90–99.Nair, G.R., Li, Z., Gariepy, Y., Raghavan, V. Drying Technology, 2011, 29, 11, 1291-1296.

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Section: Introductionmentioning

confidence: 99%

Microwave drying of corn seeds: Effect of Temperature on Drying Time, Energy Consuption and Germination Rate

Moreno

Maqueda

Ballesteros

et al. 2019

Proceedings 17th International Conference on Microwave and High Frequency Heating

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“…In contrast, microwave radiation induced motion of the water dipoles, which resulted in dissipation of energy as heat. This led to volumetric heating, immediate internal steam generation and expansion [ 36 ], demonstrated by the smaller temperature gradient from the edge to the center of the sample when compare to pure convection ( Figure 1 d) and significant longitudinal expansion ( Figure 1 b). The drying mechanism is schematically shown in Figure 1 e, convective heating primarily promoted transport of water (

) from the surface to the surrounding while internal water transport was limited by the conductive heat transfer (

).…”

Section: Resultsmentioning

confidence: 99%

Fabrication of a Novel Protein Sponge with Dual-Scale Porosity and Mixed Wettability Using a Clean and Versatile Microwave-Based Process

et al. 2021

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An open-porous protein sponge with mixed wettability is presented made entirely from whey proteins and with promising applications in biomedicine, pharmaceutical, and food industry. The fabrication relies on an additive-free, clean and scalable process consisting of foaming followed by controlled microwave-convection drying. Volumetric heating throughout the matrix induced by microwaves causes fast expansion and elongation of the foam bubbles, retards crust formation and promotes early protein denaturation. These effects counteract collapse and shrinkage typically encountered in convection drying of foams. The interplay of high protein content, tailored gas incorporation and controlled drying result in a dried structure with dual-scale porosity composed of open macroscopic elongated foam bubbles and microscopic pores in the surrounding solid lamellae induced by water evaporation. Due to the insolubility and mixed wettability of the denatured protein network, polar and non-polar liquids are rapidly absorbed into the interconnected capillary system of the sponge without disintegrating. While non-watery liquids penetrate the pores by capillary suction, water diffuses also into the stiff protein matrix, inducing swelling and softening. Consequently, the water-filled soft sponge can be emptied by compression and re-absorbs any wetting liquid into the free capillary space.

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“…Radiation in this range is mainly use in wireless telecommunication protocols, such as Bluetooth and wi-fi modems [49]. A na row part of the microwave spectrum is used for industrial, domestic, scientific, and me ical purposes (ISM bands) [50]. The industrial and domestic uses of microwaves com from the ability to heat certain materials depending on their dielectric properties [49,51 For instance, the radiation in a domestic microwave oven (2.45 GHz; λ: 12.2 cm) interac with the water contained in the food, heating it swiftly due to the intrinsic dielectric pro erties of the water molecules.…”

Section: Concepts and Mechanisms Of Microwave Heatingmentioning

confidence: 99%

Microwave-Assisted Preparation of Luminescent Inorganic Materials: A Fast Route to Light Conversion and Storage Phosphors

et al. 2021

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Luminescent inorganic materials are used in several technological applications such as light-emitting displays, white LEDs for illumination, bioimaging, and photodynamic therapy. Usually, inorganic phosphors (e.g., complex oxides, silicates) need high temperatures and, in some cases, specific atmospheres to be formed or to obtain a homogeneous composition. Low ionic diffusion and high melting points of the precursors lead to long processing times in these solid-state syntheses with a cost in energy consumption when conventional heating methods are applied. Microwave-assisted synthesis relies on selective, volumetric heating attributed to the electromagnetic radiation interaction with the matter. The microwave heating allows for rapid heating rates and small temperature gradients yielding homogeneous, well-formed materials swiftly. Luminescent inorganic materials can benefit significantly from the microwave-assisted synthesis for high homogeneity, diverse morphology, and rapid screening of different compositions. The rapid screening allows for fast material investigation, whereas the benefits of enhanced homogeneity include improvement in the optical properties such as quantum yields and storage capacity.

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Microwave and Dielectric Drying

Cited by 36 publications

References 1 publication

Microwave drying of corn seeds: Effect of Temperature on Drying Time, Energy Consuption and Germination Rate

Microwave drying of corn seeds: Effect of Temperature on Drying Time, Energy Consuption and Germination Rate

Fabrication of a Novel Protein Sponge with Dual-Scale Porosity and Mixed Wettability Using a Clean and Versatile Microwave-Based Process

Microwave-Assisted Preparation of Luminescent Inorganic Materials: A Fast Route to Light Conversion and Storage Phosphors

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