Dielectric Properties of Blackberries as Related to Microwave Drying Control

2017 ◽  
Vol 13 (12) ◽  
Author(s):  
Chunfang Song ◽  
Tian Sang ◽  
Haiying Chen ◽  
Li Zhenfeng ◽  
Li Jing
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Moisture Content ◽  
Penetration Depth ◽  
Loss Factor ◽  
Large Scale ◽  
Coaxial Line ◽  
Dielectric Constants ◽  
Microwave Drying ◽  
Increasing Temperature

AbstractThe dielectric properties of blackberry samples with a 20.0–80.0 % w.b (web basis) moisture content were determined with a network analyzer and an open-ended coaxial-line probe over a frequency range from 5 to 3000 MHz and a temperature range from 20 to 100 °C. The results showed that the dielectric constant decreased with increasing temperature but increased with increasing moisture content; however, the loss factor increased with increasing temperature and moisture content. The dielectric constant and the loss factor decreased with increasing frequency. The penetration depth decreased with increasing temperature, frequency and moisture content. A large penetration depth at 915 MHz may provide practical large-scale dielectric drying for blackberries. The dielectric constants and loss factors for blackberry by combining the above mathematical model and temperature and moisture of the sample in the microwave drying process were used to analyze and control blackberry drying technology.

Dielectric Properties and Microwave Heating Characteristics of Sodium Chloride at 2.45 GHz

2013 ◽  
Vol 32 (6) ◽  
pp. 587-596 ◽  
Author(s):  
Chenhui Liu ◽  
Libo Zhang ◽  
Jinhui Peng ◽  
Wenwen Qu ◽  
Bingguo Liu ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Sodium Chloride ◽  
Moisture Content ◽  
Penetration Depth ◽  
Loss Tangent ◽  
Loss Factor ◽  
Dielectric Measurement ◽  
Linear Functions ◽  
Microwave Drying

AbstractThe effects of moisture content and temperature on the dielectric property of sodium chloride were investigated by using open-ended senor dielectric measurement system at the frequency of 2.45 GHz. Moisture content is a major influencing factor in the variation of dielectric properties. Dielectric constant, loss factor and loss tangent all increase linearly with moisture content increasing. Three predictive models were developed to obtain dielectric constant, loss factor, loss tangent and of sodium chloride as linear functions of moisture content. Temperature between 20 °C and 100 °C has a positive effect on dielectric constant and loss factor. Penetration depth decreased nonlinearly with moisture and temperature increasing. A predictive model was developed to calculate penetration depth for sodium chloride as a fifth function of moisture content. In addition, the measurements indicate that the particles temperature increases linearly with microwaving heating time at different power levels. The knowledge gained from these results is useful in developing more effective applications of microwave drying and designing better sensors for measuring moisture content of sodium chloride.

scholarly journals Dielectric Properties of Switchgrass and Corn Stover in the Radio Frequency Range

2021 ◽  
Vol 64 (1) ◽  
pp. 243-252
Author(s):  
Augusto M. Souza ◽  
Stuart J. Birrell ◽  
Brian L. Steward
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Moisture Content ◽  
Radio Frequency ◽  
Corn Stover ◽  
Loss Factor ◽  
Prediction Models ◽  
Dielectric Constants ◽  
Frequency Range ◽  
Loss Factors

HighlightsDielectric permittivities of switchgrass and corn stover in the radio frequency range were calculated.Prediction models achieved R2 > 0.9, except for the switchgrass loss factor for the material in motion.The loss factors were different when static and in motion, but the dielectric constants were similar.Abstract. The dielectric properties of biological materials are relevant when developing moisture content sensors. However, little is known about the permittivities of switchgrass and corn stover in a wider frequency range. The goal of this research was to determine their dielectric constants and loss factors at different moisture contents across a frequency range of 5 Hz to 13 MHz and with the material static and in motion inside a sample container. The permittivity of these materials was calculated by measuring their admittance in a test fixture using an impedance analyzer at three different moisture levels (9.0% to 30.5%). Overall, the materials’ dielectric properties increased with moisture but decreased with frequency. Prediction models were developed using the data in a frequency range of 10 kHz to 5 MHz. Model coefficients of determination were higher than 0.90 in general, except for the model measuring the loss factor of switchgrass in motion. Additionally, the dielectric constant was not different with the materials static or in motion, but the loss factor values were distinct. This work can be used for the development of electrical moisture content sensors for switchgrass and corn stover. Keywords: Corn stover, Dielectric constant, Loss factor, Moisture content, Permittivity, Switchgrass.

Microwave Nondestructive Sensing of Moisture Content and Water Activity of Almonds

2021 ◽  
Vol 64 (4) ◽  
pp. 1373-1379
Author(s):  
Samir Trabelsi
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Moisture Content ◽  
Bulk Density ◽  
Water Activity ◽  
Free Space ◽  
Loss Factor ◽  
Dielectric Loss Factor ◽  
List Type

HighlightsMoisture and water activity were determined nondestructively and in real time from measurement of dielectric properties.Moisture and water activity calibration equations were established in terms of the dielectric properties.Situations in which bulk density was known or unknown were considered.SEC ranged from 0.41% to 0.68% for moisture and from 0.02 to 0.04 for water activity.Abstract. A method for rapid and nondestructive determination of moisture content and water activity of granular and particulate materials was developed. The method relies on measurement of the dielectric constant and dielectric loss factor at a single microwave frequency. For the purpose of illustration, the method was applied to predicting the moisture content and water activity of almond kernels. A free-space transmission technique was used for accurate measurement of the dielectric properties. Samples of Bute Padre almond kernels with moisture content ranging from 4.8% to 16.5%, wet basis (w.b.), and water activity ranging from 0.50 to 0.93 were loaded into a Styrofoam sample holder and placed between two horn-lens antennas connected to a vector network analyzer. The dielectric properties were calculated from measurement of the attenuation and phase shift at 8 GHz and 25°C. The dielectric properties increased linearly with moisture content, while they showed an exponential increase with water activity. Situations in which the bulk density was known and unknown were considered. Linear and exponential growth regressions provided equations correlating the dielectric properties with moisture content and water activity with coefficients of determination (r2) higher than 0.96. Analytical expressions of moisture content and water activity in terms of the dielectric properties measured at 8 GHz and 25°C are provided. The standard error of calibration (SEC) was calculated for each calibration equation. Results show that moisture content can be predicted with SECs ranging from 0.41% to 0.68% (w.b.) and water activity with SECs ranging from 0.02 to 0.04 for almond kernel samples with water activity ranging from 0.5 to 0.9 and moisture contents ranging from 4.8% to 16.5% (w.b.). Keywords: Bulk density, Dielectric constant, Dielectric loss factor, Free-space measurements, Loss tangent, Microwave frequencies, Moisture content, Water activity.

scholarly journals Dielectric and Conductivity Properties of Some Wood Composites

2016 ◽  
Vol 8 ◽  
pp. 51-60
Author(s):  
K.Ch. Varada Rajulu ◽  
B.N. Mohanty
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Low Temperature ◽  
Temperature Region ◽  
Loss Factor ◽  
Wood Composites ◽  
Frequency Range ◽  
Increasing Temperature ◽  
Coaxial Probe

This study presents the dielectric and conductivity properties as function of temperature and frequency of wood based composites. These properties were measured by an open-ended coaxial probe at frequency range between 100 kHz to 100MHz, temperature from 30OC to 200OC which is fully computer interfaced. It has been observed that dielectric constant (ε') and dielectric loss factor (ε") increase with increasing temperature and decrease with increasing frequency. At low temperature region, the conductivity depends significantly on the frequency. However, with the increase in temperature dielectric relaxation takes place and the dependency of the conductivity on frequency get reduced. The patterns of variation were established for the studied specimens and discrepancies were discussed. The study of dielectric properties will help in improving the drying, heating and gluing processes of wood and wood based products.

Comparison of Dielectric Properties of Traditional and High-Oleic Runner-Type Peanuts at Microwave Frequencies

2021 ◽  
Vol 64 (6) ◽  
pp. 1817-1822
Author(s):  
Micah A. Lewis ◽  
Samir Trabelsi
Keyword(s):  
Dielectric Constant ◽  
Oleic Acid ◽  
Linoleic Acid ◽  
Dielectric Properties ◽  
Moisture Content ◽  
Loss Tangent ◽  
Loss Factor ◽  
Microwave Frequencies ◽  
High Oleic ◽  
Transmission Measurements

HighlightsPermittivity measurements were taken for traditional and high-oleic runner-type peanut pods and kernels at microwave frequencies.The dielectric constant, loss factor, loss tangent, and complex plane were compared between the two cultivars to observe any effect caused by the high-oleic trait.Despite differences in composition, minimal to no differences were observed in permittivity between the two cultivars.Abstract. Different cultivars of peanuts containing higher amounts of oleic acid have been developed to improve oxidative stability and overall peanut quality. Increasing oleic acid levels and decreasing linoleic acid levels in peanuts deter lipid oxidation, preventing the creation of off-flavors and increasing the shelf life. Since their conception, high-oleic peanuts have been tested from chemical and sensory perspectives to observe differences between them and traditional peanuts. Such tests have shown minimal differences, if any. However, tests to observe the effect of changing the levels of oleic and linoleic acid on permittivity, which is often used for nondestructive determination of the moisture content and bulk density of foods and agricultural products, have not been reported. Thus, a vector network analyzer (VNA) was used to take free-space transmission measurements of the complex permittivities of high-oleic and traditional runner-type peanut pods and kernels. Measurements were taken at 23°C between 5 and 9 GHz. Measurements yielded the dielectric constant and loss factor, which are often correlated to moisture content. Analysis was performed to compare the changes in the dielectric constant, loss factor, and loss tangent with moisture content for high-oleic and traditional peanuts. Linear trends were observed for each parameter with increasing moisture content for both cultivars. Results from the complex plane showed coefficient of determination (r2) values greater than 0.9 for pods and kernels. Therefore, at microwave frequencies, changing the levels of oleic and linoleic acid within the peanuts was observed to have minimal to no effect on their permittivity. Thus, moisture calibrations based on correlations between dielectric properties and moisture content for traditional runner-type peanuts can be applied to high-oleic cultivars. Keywords: Dielectric properties, Free-space transmission measurements, Microwave measurements, Oleic acid, Peanut kernels, Peanut pods.

Dielectric Properties of Importance in Operations of Post-harvest of Sorghum

2017 ◽  
Vol 13 (4) ◽  
Author(s):  
Caciano P. Z. Noreña ◽  
Carlos E. Lescano-Anadón
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Electrical Properties ◽  
Dielectric Loss ◽  
Moisture Content ◽  
Loss Factor ◽  
Dissipation Factor ◽  
Post Harvest ◽  
Moisture Contents ◽  
And Storage

Abstract The knowledge of electrical properties and their relationship with moisture content is of great importance in operations of post-harvest and storage in grains. The dielectric properties of sorghum samples were studied at different moisture contents and temperatures (25 at 41 °C), at frequencies of 1 and 10 kHz. In order to measure changes in the capacitance and dissipation factor of the samples, the method of impedance bridge was used. Both the dielectric constant and the dielectric loss factor of the samples increased with increasing moisture content and temperature; however, they decreased with increasing frequency. Models were proposed to relate the dielectric properties to either the moisture (exponential and polynomial) or temperature (linear).

scholarly journals Combined Effect of Temperature and Oil and Salt Contents on the Variation of Dielectric Properties of a Tomato-Based Homogenate

Foods ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 3124
Author(s):  
Andres Abea ◽  
Pere Gou ◽  
Maria Dolors Guardia ◽  
Sancho Bañon ◽  
Israel Muñoz
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Olive Oil ◽  
Loss Factor ◽  
Salt Content ◽  
Effect Of Temperature ◽  
Dielectric Heating ◽  
Know How ◽  
Increasing Temperature ◽  
Added Salt

Tomato-based processed foods are a key component of modern diets, usually combined with salt and olive oil in different ratios. For the design of radiofrequency (RF) and microwave (MW) heating processes of tomato-based products, it is of importance to know how the content of both ingredients will affect their dielectric properties. Three concentrations of olive oil and salt were studied in a tomato homogenate in triplicate. The dielectric properties were measured from 10 to 3000 MHz and from 10 to 90 °C. Interaction effects were studied using a general linear model. At RF frequencies, the dielectric constant decreased with increasing temperature in samples without added salt, but this tendency was reversed in samples with added salt. The addition of salt and oil increased the frequency at which this reversion occurred. At MW frequencies, the dielectric constant decreased with increasing temperature, salt, and oil content. The loss factor increased with increasing salt content and temperature, except in samples without added salt at 2450 MHz. Penetration depth decreased with increasing frequency and loss factor. Salt and oil contents have a significant effect on the dielectric properties of tomato homogenates and must be considered for the design of dielectric heating processes.

Study on the Dielectric Properties of Biomass Material of Tobacco Stems

2013 ◽  
Vol 634-638 ◽  
pp. 2570-2578 ◽  
Author(s):  
Wen Hua Zi ◽  
Xiao Long Zhang ◽  
Lan Wang ◽  
Jin Hui Peng ◽  
Lin Chen
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Moisture Content ◽  
Loss Factor ◽  
Microwave Frequency ◽  
Dielectric Loss Factor ◽  
Dipolar Relaxation ◽  
Genetic Characteristics ◽  
Position Location

An Agilent E4980A precision the LCR meter was used to estimate the effect of frequency, moisture content, position, location and variety on dielectric properties for biomass material of tobacco stems at microwave frequency of 2MHz. The dielectric properties of tobacco stems were significantly affected by frequency and moisture content. Both dielectric constant and dielectric loss factor rapidly declined first and then slowed with increasing frequency at lower moisture content. Increasing the moisture content, dielectric constant increased with the increasing frequency by orders of magnitude, while dielectric loss factor increased first and then decreased with dielectric relaxation emerging, where the dipolar relaxation frequency and the max of the dielectric loss factor also increased. Dielectric properties of the biomass material of tobacco stem were also affected by position, location and variety to some degree. The dielectric properties variation of K326 and Yun 87 was similar to each other which reflected their same genetic characteristics. At the frequency of 2MHz, dielectric constant and dielectric loss factor were mainly at 50-100 and 0.005-0.020, respectively.

Devitrification and dielectric properties of (Na2O,BaO)–Nb2O5–SiO2 and (K2O,SrO)–Nb2O5–SiO2 glass–ceramics

2007 ◽  
Vol 22 (7) ◽  
pp. 1996-2003 ◽  
Author(s):  
Fei Peng ◽  
Robert F. Speyer ◽  
Wesley Hackenberger
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Alkaline Earth ◽  
Amorphous Matrix ◽  
Glass Ceramics ◽  
Dielectric Constants ◽  
Sio2 Glass ◽  
Increasing Temperature

(Na2O,BaO)–Nb2O5–SiO2 and (K2O,SrO)–Nb2O5–SiO2 glass ribbons with varying proportions of alkali and alkaline earth were formed using roller quenching. (Na2O,BaO)–Nb2O5–SiO2 glasses of compositions devitrified to form Ba2NaNb5O15 (in the form of ∼80 nm crystallites in an amorphous matrix) yielded frequency-stable dielectric constants of ∼250 and losses of ∼0.05. Such low losses and frequency stabilities were also observed from (K2O,SrO)–Nb2O5–SiO2 glasses of compositions forming predominantly KSr2Nb5O6 (∼30 nm crystals), yielding dielectric constants of ∼400. Both optimized compositions showed moderate decreases in dielectric constant with increasing temperature.

scholarly journals Using a Dielectric Capacitance Cell to Determine the Dielectric Properties of Pure Sand Artificially Contaminated with Pb, Cd, Fe, and Zn

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Mohammed Dahim ◽  
Musab Abuaddous ◽  
Rabah Ismail ◽  
Hashem Al-Mattarneh ◽  
Aiman Jaradat
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Loss Factor ◽  
Simple Calculation ◽  
Dielectric Constants ◽  
Pollution Level ◽  
Dielectric Capacitance ◽  
Capacitance Cell

This paper presents a new method of dielectric capacitance cell as a proposed device for measuring the impedance of pure sand artificially contaminated with four heavy metals. Dielectric constant and loss factor of clean and contaminated sand at various levels were calculated from the measured sand impedances. The advantages and benefits of using the proposed dielectric capacitance cell were its low cost, simple calculation, calibration procedures, portable and lightweight, and easy to modify the electrodes to suit testing in the field. Pure sand was saturated with water artificially polluted in the lab with Pb, Cd, Fe, and Zn at heavy metal contents 0, 7.5, 15, 22.5, and 30 mg/kg of sand. The dielectric properties of polluted sand were evaluated at a frequency range from 100 kHz to 1000 kHz. The polluted sand exhibit different dielectric constants and loss factors from the unpolluted sand. The results also indicate that the dielectric constant decreases with increasing pollution level for all heavy metals. This may attribute to the polarization mechanism change with existing heavy metal. The loss factor of sand increases with the increasing pollution level. This may be explained by the increase of ionic conductivity of pore water with heavy metal in the sand. Sand polluted with heavy metal with higher resistivity and density possess a higher dielectric constant and lower loss factor than other polluted metals. Evaluation of the dielectric characteristics of polluted sand could have the potential to monitor heavy metal pollution. Even with promising results obtained with the proposed dielectric device, it is necessary to explore several other factors affecting the measurements such as sand water content, soil texture, and type of soil. Also, testing polluted soil near industrial pollution is needed.

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