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.

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.

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.

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 properties of zinc sulfide concentrate during the roasting at microwave frequencies

2017 ◽  
Author(s):  
Guangjun He ◽  
Shiwei Li ◽  
Kun Yang ◽  
Jian Liu ◽  
Peng Liu ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Zinc Sulfide ◽  
Apparent Density ◽  
Loss Tangent ◽  
Loss Factor ◽  
Microwave Energy ◽  
Dielectric Loss Factor ◽  
Sulfide Concentrate

Microwave technology has a potential application in the extraction of zinc from sulphide ores, knowledge of the dielectric properties of these ores plays a major role in the microwave design and simulation for any process. The dielectric properties of zinc sulfide concentrate for two different apparent densities—1.54 and 1.63 g/cm3—have been measured by using the resonance cavity perturbation technique at 915 and 2450 MHz during the roasting process for the temperature ranging from room temperature to 850 °C. The variations of dielectric constant, the dielectric loss factor, the dielectric loss tangent and the penetration depth with the temperature, frequency and apparent density have been investigated numerically. The results indicate that the dielectric constant increases as the temperature increases and temperature has a pivotal effect on the dielectric constant, while the dielectric loss factor has a complicated change and all of the temperature, frequency and apparent density have a significant impact to dielectric loss factor. Zinc sulfide concentrate is high loss material from 450 to 800 °C on the basis of theoretical analyses of dielectric loss tangent and penetration depth, its ability of absorbing microwave energy would be enhanced by increasing the apparent density as well. The experimental results also have proved that zinc sulfide concentrate is easy to be heated by microwave energy from 450 to 800 °C. In addition, the experimental date of dielectric constant and loss factor can be fitted perfectly by Boltzmann model and Gauss model, respectively.

Effect of thermal plasma heating on the dielectric properties of Al-Zr composites

2002 ◽  
Vol 216 (2) ◽  
pp. 127-132
Author(s):  
D R Sahu ◽  
B K Roul ◽  
S K Singh ◽  
R N P Chaudhury
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Thermal Plasma ◽  
Loss Factor ◽  
Gas Flow ◽  
Plasma Heating ◽  
Sintered Sample ◽  
Dielectric Measurement ◽  
Sintering Time ◽  
Tan Δ

A low-cost extended arc thermal plasma heating (EATPH) source has been used for the sintering of Al-Zr high-temperature ceramic oxides, and their dielectric properties have been studied. Pellets of Al-Zr composites were sintered using optimum sintering parameters such as sintering time, plasma power and plasmagen gas flow rate in an EATPH reactor. Samples of similar composites were also sintered using a conventional resistive heating furnace at 1500°C for 20 h, and their dielectric properties were studied and compared with the plasma sintered sample. Sintered pellets were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and dielectric measurement, carried out as a function of frequency and temperature. Highly dense sintered products were obtained by the plasma heating route within a very short sintering time compared with the conventional sintering schedule. Dielectric measurements (both dielectric constant and loss factor) showed a significant reduction in the dielectric constant, K, at room temperature under different test frequencies and also as a function of temperature. However, the change in dielectric loss factor, tan Δ, was not as pronounced as the change in K. The behaviour of the K and tan Δ curves changes drastically compared with the conventional sintered material. The reduction in K and the crossover behaviour of tan Δ in the plasma sintered specimen may be due to the action of non-reactive Ar plasmagen gas during plasma sintering, which favours mobile oxygen for the polarization network under the influence of frequency and temperature.

scholarly journals Detection of biodegradation degree of sludge using dielectric measurement

2018 ◽  
Vol 6 (1-2) ◽  
pp. 108-112
Author(s):  
Sándor Beszédes ◽  
Katalin Papp-Sziládi ◽  
Gábor Keszthelyi-Szabó ◽  
Cecília Hodúr
Keyword(s):  
Dielectric Constant ◽  
Organic Matter ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Loss Factor ◽  
Dielectric Loss Factor ◽  
Dielectric Measurement ◽  
Energetic Efficiency ◽  
Dielectric Parameters ◽  
Polymeric Structure

Pre-treatments applied before biological sludge utilization technologies aim to modify the sludge structure for enhanced disintegration degree and biodegradability. Among the thermal pre-treatments methods, microwave irradiation is suitable to degrade the polymeric structure of sludge, and to increase the solubility of organic matters. Energetic efficiency of microwave heating is mainly determined by the dielectric properties, such as dielectric constant and dielectric loss factor. Dielectric properties are influenced by the frequency, temperature; composition and consistency of irradiated material, state and bond of water etc. Therefore, physicochemical changes of sludge structure; e.g. hydrolysis of macromolecules, degradation of cell wall of microorganisms, aggregation of particles; contribute to the change of dielectric parameters, as well. In our work we investigated the correlation between the dielectric parameters and structural change and biodegradability indicators. In the case of municipal wastewater, the change of organic matter removal efficiency during wastewater purification technology at a wastewater treatment plant can be detected by the change of dielectric constant. Results related to sludge processing show, that change of organic matter solubility and aerobic biodegradability correlate the change of dielectric loss factor and dielectric constant. With the degradation of polymeric structure of sludge matrix and decomposition of macromolecules caused by thermal effects or chemical pre-treatments led to increased mobility of ions and enhanced polarization of molecules. These effects led to increased dielectric constant and loss factor, what make possible to pre-indicate the efficiency of sludge pre-treatment processes by an in line and real time measurement method.

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).

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.

scholarly journals High-Temperature Permittivity and Microwave Pretreatment Characteristics of Nickel-Containing Sludge from Battery Production

Processes ◽  
2019 ◽  
Vol 7 (5) ◽  
pp. 257 ◽  
Author(s):  
Zhanyong Guo ◽  
Ping Guo ◽  
Guang Su ◽  
Demei Zhai ◽  
Fang Cheng ◽  
...  
Keyword(s):  
Particle Size ◽  
Dielectric Constant ◽  
Penetration Depth ◽  
Loss Tangent ◽  
Loss Factor ◽  
Initial Moisture Content ◽  
Conventional Heating ◽  
Heating Curve ◽  
Microwave Pretreatment ◽  
Increasing Temperature

Permittivity is a vitally important parameter for the description of the absorption and heating characteristics of materials under microwave irradiation. In this paper, the permittivity of nickel-containing sludge (NCS), which is created during battery production as a cheap secondary resource, was measured at temperatures from 20 °C to 600 °C at 2.45 GHz using the cavity perturbation method. In addition, the loss tangent (tanδ) and penetration depth (Dp) of microwaves into the material were calculated. The results of the permittivity study show that the dielectric constant (ε′) and dielectric loss factor (ε″) of the NCS increase with increasing temperature. The variations of the loss tangent (tanδ) and penetration depth (Dp) with the temperature can be divided into two parts at 200 °C. The effect of the initial moisture content on the dielectric properties of the material is notably greater than that of the temperature, which was confirmed by the heating curve. After microwave pretreatment, the nickel-containing phase is transformed into NiO, while the weight of NCS is reduced by more than 20%, the particle size is significantly reduced and the leaching time reduce 20 min than that of conventional heating.

scholarly journals Measurement and Analysis of Dielectric Properties of Agricultural By-product Powders in Microwave Frequency Range

2019 ◽  
Vol 78 ◽  
pp. 02012
Author(s):  
Runeng Zhong ◽  
Tai Xiang ◽  
Qinhong Zheng ◽  
Bo Xu
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Moisture Content ◽  
Loss Factor ◽  
Microwave Frequency ◽  
Powder Materials ◽  
Microwave Assisted ◽  
Measurement And Analysis ◽  
By Products

Dielectric properties play an important role in the microwave-assisted application of nonmagnetic agriculture-related media. In this paper, the practical requirements for the lack of quantitative data on the dielectric properties of agricultural media in microwave-assisted applications are obtained. The dielectric properties data of four kinds of agricultural by-products powder (Potato powder, Pseudo -ginseng Powder, Gastrodia elata powder, Dendrobium chrysotoxum Lindl powder) under microwave frequency were measured, and related factors were analyzed. The results show that the uncalibrated coaxial transmission reflection method can be used to measure and analyse the dielectric properties of high frequency bands of powder materials. Dielectric constant (ε ′) and Dielectric loss factor (ε '') of agricultural by-products at room temperature have a relationship between microwave frequency and moisture content. It is a dependent and the mathematical relation is satisfied. The influence of microwave frequency and moisture content on the dielectric properties is as follows: lows: ε′>ε′′>tanδ. Under the conditions of civil microwave frequency (2.45GHz) and moisture content (2% ~ 25%), the dielectric constant and the dielectric loss factor of different kinds of agricultural by-products powder are in the range of 3.5 ~ 9 and 0.1 ~ 3.2 respectively. The results provide data basis for microwave processing and quality monitoring of agricultural by-products powder. The technical method is suitable for the measurement and analysis of the dielectric properties of powder materials.

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