Dielectric Heating Applications Research Articles

Plus-Shape of Mushroom-Like EBG with Square Microstrip Emitter to Expand the Working Space in Dielectric Heating Applications

Plus-Shape of Mushroom-Like EBG with Square Microstrip Emitter to Expand the Working Space in Dielectric Heating Applications

Synthesis of Medicinally Privileged Heterocycles through Dielectric Heating.

Heterocyclic compounds are intriguing part of modern drug discovery research. Ecofriendly syntheses of heterocycles, following green techniques, are privileged routes to protect Mother nature. Microwave-assisted synthesis of chemical compounds is considered as a major greener pathway, both in academia and industry. A total of 106 publications (including a few authentic web links) have been reviewed mainly to discuss (i) mechanism of microwave irradiation, (ii) abundance of commercial heterocyclic drugs, (iii) various synthetic procedures, and (iv) medicinal activity of the synthesized molecules. This review summarizes the potential application of microwave irradiation (dielectric heating) to synthesize biologically important heterocyclic small molecules in the recent past. A huge number of heterocyclic compounds are present in various natural sources like plant, marine microbe or other organisms and many of them possess unique biological activity. In addition to nature-derived heterocyclic compounds, a large number of synthetic heterocycles are being used as medicines. This review describes the relevant recent examples of microwave irradiation to accomplish various chemical transformations accelerated by a variety of catalysts which include, but not limited to, Lewis acids, other metal containing catalysts, organocatalysts, heterogeneous catalysts, phase-transfer catalysts, solid-supported catalysts, inorganic catalysts (bases, acids and salts) and so on. Although there are an increasing number of reports on application of dielectric heating in various other fields, this review is focused on a large number of new and novel strategies related to synthetic organic chemistry. The discussion is mostly organized by the disease type although some reactions/molecules can certainly be placed in multiple sections. Since green chemistry is an extremely emerging and comparatively new field of research, attempts to stimulate more activities on green medicinal chemistry are provided. Discussion related to the concurrent effect of microwaves, catalysts and/or solvents, supports to constitute expeditious and general route for the syntheses of medicinally important heterocyclic compounds and pharmacophores has also been included. The dielectric heating procedure to produce novel medicinally privileged heterocyclic scaffolds/ compounds is extremely promising and challenging. As a result, this green technique has been gaining increasing interest from the pharmaceutical world. A recent update has been presented. While every effort has been made to include all pertinent reports in this field, any omission is unintentional.

Electrical Properties of Sunflower Achenes

Abstract This work contains the results of measuring the electrical properties of sunflower achenes. The interest in electrical properties of biological materials resulted in engineering research in this field. The results of measurements are used for determining the moisture content, the surface level of liquid and grainy materials, for controlling the presence of pests in grain storage, for the quantitative determination of mechanical damage, in the application of dielectric heating, and in many other areas. Electrical measurements of these materials are of fundamental importance in relation to the analysis of quantity of absorbed water and dielectric heating characteristics. It is a well-known fact that electrical properties of materials, namely dielectric constant and conductivity, are affected by the moisture content of material. This fact is important for the design of many commercial moisturetesting instruments for agricultural products. The knowledge of dielectric properties of materials is necessary for the application of dielectric heating. The aim of this work was to measure conductivity, dielectric constant and loss tangent on samples of sunflower achenes, the electrical properties of which had not been sufficiently measured. Measurements were performed under variable moisture content and the frequency of electric field ranging from 1 MHz to 16 MHz, using a Q meter with coaxial probe. It was concluded that conductivity, dielectric constant and loss tangent increased with increasing moisture content, and dielectric constant and loss tangent decreased as the frequency of electric field increased.

The Effect of Electric Field Distributions on Grains and Insect for Dielectric Heating Applications

The Effect of Electric Field Distributions on Grains and Insect for Dielectric Heating Applications

The Effect of Electric Field Distributions on Grains and Insect for Dielectric Heating Applications

The Effect of Electric Field Distributions on Grains and Insect for Dielectric Heating Applications

The Effect of Electric Field Distributions on Grains and Insect for Dielectric Heating Applications

The Effect of Electric Field Distributions on Grains and Insect for Dielectric Heating Applications

The Effect of Electric Field Distributions on Grains and Insect for Dielectric Heating Applications

The Effect of Electric Field Distributions on Grains and Insect for Dielectric Heating Applications

The Effect of Electric Field Distributions on Grains and Insect for Dielectric Heating Applications

The Effect of Electric Field Distributions on Grains and Insect for Dielectric Heating Applications

The Effect of Electric Field Distributions on Grains and Insect for Dielectric Heating Applications

The Effect of Electric Field Distributions on Grains and Insect for Dielectric Heating Applications

The Effect of Electric Field Distributions on Grains and Insect for Dielectric Heating Applications

The Effect of Electric Field Distributions on Grains and Insect for Dielectric Heating Applications

Electrical Prope Rties of Popcorn Grains

Abstract This work contains the results of measuring the electrical properties of popcorn grains. Interest in electrical properties of biological materials resulted in engineering research in this field. The results of measurements are used for determining the moisture content, the surface level of liquid and grainy materials, for controlling the presence of pests in grain storage, for a quantitative determination of mechanical damage, in applications of dielectric heating, and in many other cases. Electrical measurements on these materials are of fundamental importance in relation to the analysis of quantity of absorbed water and dielectric heating characteristics. It is a well-known fact that electrical properties of materials, namely dielectric constant and conductivity, are affected by the moisture content of material. This fact is important for the design of many commercial moisture-testing instruments for agricultural products. The knowledge of dielectric properties of materials is necessary for the application of dielectric heating. The aim of this work was to perform the measurements of conductivity, dielectric constant and loss tangent on samples of popcorn grains, the electrical properties of which had not been sufficiently measured. Measurements were performed under variable moisture content and the frequency of electric field in the range from 1 MHz to 16 MHz, using a Q meter with a coaxial probe. It was concluded that conductivity, dielectric constant and loss tangent increased with increase of moisture content, and dielectric constant and loss factor decreased as the frequency of electric field increased.

Frequency, moisture and temperature-dependent dielectric properties of chickpea flour

Knowledge of dielectric properties of agricultural commodities is essential to develop thermal treatments using radio frequency and microwave energy. Dielectric properties (the dielectric constant and loss factor) of compressed chickpea flour samples were determined using an open-ended coaxial-line probe with an impedance analyzer over the frequency range from 10 to 1800 MHz, moisture contents from 7.9% to 20.9% w.b., and temperatures from 20 to 90 °C. Both dielectric constant and loss factor of chickpea samples decreased monotonically with increases in frequency at all temperatures and moisture levels. Ionic conduction was the dominant factor influencing the dielectric loss at lower frequencies in relatively high moisture samples. Dielectric constant and loss factor increased with increases in temperature and moisture content. The rate of increase was greater at higher temperature and moisture levels than at lower temperature and moisture levels. A linear relationship was obtained between the dielectric constant and loss factor when divided by the sample density. Knowledge of the frequency, moisture, and temperature-dependent behaviours of chickpea samples should be helpful in dielectric heating applications and developing new dielectric property based moisture meters.

Agricultural applications of dielectric measurements

A brief historical perspective on dielectric properties of agricultural products is presented, including their use for rapid measurement of moisture content in grain and in considering potential dielectric heating applications. General principles are discussed as they relate to dielectric properties of materials and energy absorption from radio-frequency and microwave electric fields. Measurement principles and techniques for determining the dielectric properties of agricultural materials are described, and appropriate references are cited for detailed information. Dielectric properties data for some grain, insects, fruits, and vegetables are presented that relate to applications for selective heating of insects in grain and potential maturity and quality sensing in fresh fruits and vegetables. Principles are discussed for the use of microwave dielectric properties for sensing moisture content in grain, and relationships between dielectric properties of granular and powdered materials and their bulk densities are described

Inhibition of Weed Seed Germination by Microwaves

AbstractIrradiation with radiofrequency energy (RF), which includes microwaves, brings about dielectric heating of moist materials. Some agricultural applications of dielectric heating by RF have included insects control in stored grains and improved germination of seed stocks. The objective of the present research was to evaluate microwave heating of soils as a technique for weed control. Approximately 800‐g masses of soil of variable wetness (10‐280 g H2O/kg soil) containing seeds of oat (Arena sativa L.) and indigenous weeds were heated in a microwave (2.45 GHz) oven for 15 to 240 s. Soil masses were 5 cm deep in flats. Oat seeds were placed 2 cm deep into the soil. Hearing of soils to 80 °C or higher inhibited emergence of oats and weed species. About 120 s of heating were needed to reach 80 °C. Maintaining this temperature for 30 s was needed for strong inhibition. Moisture content in this experiment had little effect on dielectric heating. Time required to heat soil to killing temperatures appears to be a factor limiting application of this technique. The procedure may be applicable to soil sterilization in cases in which other physical processes or chemical means are inconvenient or undesirable.

Computer control of a Class-E amplifier

High frequency electrical power supplies used in many industrial applications have to be able to withstand appreciable variations in load impedance. This paper describes the use of a computer to control a Class-E amplifier power supply which is being developed for high frequency induction and dielectric heating applications.

Economic Assessment of Microwave and Radio-Frequency Materials Processing

ABSTRACTDielectric heating has clearly demonstrated its production benefits in many materials processing applications. It is, however, a relatively expensive technology and its use vis a vis less expensive alternatives must be justified by a thorough economic analysis of all factors relevant to the given application. These include not only direct production costs, but also less easily quantified “implicit” factors such as product quality, reduced impact on the external environment, and improved workplace environment.An economic model which includes both production cost considerations and implicit factors in dielectric heating applications is under development. This paper will focus on the capital and operating costs of dielectric heating equipment and the factors which influence these costs. Capital and operating cost information was obtained from radio-frequency and microwave suppliers and consultants in the United States. Mail-out questionnaires were followed up by extensive telephone discussions to correlate and clarify data. The intent was to identify the major cost components of dielectric heating equipment and to summarize the qualitative and quantitative factors which affect them. Since microwave and radio-frequency equipment are distinctly different in design and application, they are treated separately.

An RF Class C power amplifier for dielectric heating applications

Details are given of a cascade connected, modular, linear power amplifier operating at 27-12 MHz and suitable for dielectric heating applications. The prototype is capable of delivering 300 Watts and employs RF MOSFETs in two cascaded push-pull power amplifiers. Circuit construction is described and recommendations for higher power performance are given..

Optimised class-E amplifier with load variation

High-frequency electrical power supplies used in many industrial applications have to be able to withstand appreciable variations in load impedance. The letter describes the use of a computer to control a class-E amplifier power supply which is being developed for high-frequency induction and dielectric heating applications.

DIELECTRIC PROPERTIES of RICE BRAN

ABSTRACTThe dielectric properties of rice bran have been of interest because of their correlation with moisture content and because to a large extent they determine the absorption of energy in dielectric heating applications. the dielectric properties, namely, dielectric constant, loss tangent, dielectric loss factor and a.c. conductivity of rice bran were measured experimentally at a frequency of 13.56 MHz by a resonance method using a Q‐meter along with a coaxial, cylindrical sample holder. In order to study the effects of various factors, namely, the moisture content, temperature and bulk density of rice bran, the experiments were designed and performed based on Response Surface Methodology. the dielectric constant, dielectric loss factor and a.c. conductivity were found to have positive nonlinear relationships, while the loss tangent had a positive linear relationship within the ranges of factors studied, namely 3.95 to 14.05% (w.b.) moisture content, 26.5 to 53.5°C temperature, and 299.5 to 400.5 kg/m3 bulk density.

The Commercial Application of Dielectric Heating

Journal of the Society of Dyers and ColouristsVolume 98, Issue 7-8 p. 251-253 The Commercial Application of Dielectric Heating P J Hulls, P J Hulls The Electricity Council 30 Millbank London SW1P 4RDSearch for more papers by this author P J Hulls, P J Hulls The Electricity Council 30 Millbank London SW1P 4RDSearch for more papers by this author First published: July 1982 https://doi.org/10.1111/j.1478-4408.1982.tb03639.xCitations: 5AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume98, Issue7-8July 1982Pages 251-253 RelatedInformation