Investigation of Selective Microwave Heating Phenomena in the Reactions of 2-Substituted Pyridines

2017 ◽  
Vol 70 (7) ◽  
pp. 776 ◽  
Author(s):  
Péter Bana ◽  
István Greiner
Keyword(s):  
Microwave Heating ◽  
Boundary Layers ◽  
Vessel Wall ◽  
Reaction Rate ◽  
Macroscopic Scale ◽  
Microwave Effect ◽  
Heating Effects ◽  
Localized Heating ◽  
Substituted Pyridines ◽  
Comparison Technique

Debated selective microwave heating effects were investigated in a rearrangement and a benzylation reaction involving 2-substituted pyridines. An accurate, reproducible comparison technique and simultaneous temperature measurement using both external infrared and internal fibre optic sensors were utilized. The experimental details of the benzylation reaction were thoroughly addressed to resolve the inconsistencies that have been discussed previously in the literature. Hidden inhomogeneities in temperature and concentration were revealed within the reaction mixtures during microwave heating, which could be prevented by the modification of the vessel wall using an inert fluoropolymer liner. Instead of the previously proposed microscopic thermal microwave effect, the enhanced reaction rate could be explained by macroscopic-scale localized heating in the boundary layers close to the vessel surface in the microwave-heated experiment.

Microwave Heating Effects on the Chemical Composition and the Antioxidant Capacity of Tataouine Virgin Olive Oils from Tunisia

2010 ◽  
Vol 73 (10) ◽  
pp. 1891-1901 ◽  
Author(s):  
IMEN OUESLATI ◽  
WAEL TAAMALLI ◽  
FAOUZIA M. HADDADA ◽  
MOKHTAR ZARROUK
Keyword(s):  
Oxidative Stability ◽  
Microwave Heating ◽  
Genetic Factor ◽  
Degradation Rate ◽  
Treatment Time ◽  
Antioxidant Potential ◽  
Virgin Olive Oils ◽  
Olive Oils ◽  
Heating Effects ◽  
Total Fraction

Four Tunisian virgin olive oils (VOOs), derived from varieties (Chemlali Tataouine, Zarrazi Douirat, Fakhari Douirat, and Dhokar Douirat) grown in the harsh pedoclimatic conditions of the region of Tataouine, were evaluated for their responses to microwave heating. Aside from fatty acid composition, all other evaluated parameters were affected by microwave heating, and their variations depend on the genetic factor. Chemlali Tataouine VOO exhibited the slowest biophenol degradation rate and the least diminution in oxidative stability and consequently, its total fraction and both lipidic and methanolic fractions remained unchanged with an exceptional antioxidant potential. In the remaining studied VOOs, the biophenol contents, the oxidative stability, and the antioxidant potential underwent gradual decreases; nevertheless, their levels at the longer treatment time are close to some fresh VOOs. These results should be taken into consideration when Tataouine VOOs are recommended for microwave heating.

Synthesis of Oximes in the Microwave Oven

1992 ◽  
Vol 57 (11) ◽  
pp. 2407-2412 ◽  
Author(s):  
Monika Puciová ◽  
Štefan Toma
Keyword(s):  
Microwave Heating ◽  
Reaction Rate ◽  
Microwave Oven ◽  
Effect Of Solvents

The synthesis of a broad range of oximes has been studied. It was found that the application of microwave heating enhanced dramatically the reaction rate, and practically quantitative yields of oximes were isolated after less than 1-min heating in the most cases. The effect of solvents on the course of the reaction was also studied.

Microwave Nitrudation of Silicon Compacts Utilizing a Temperature Gradient

1992 ◽  
Vol 287 ◽  
Author(s):  
Jeffrey J. Thomas ◽  
Hamlin M. Jennings ◽  
D. Lynn Johnson
Keyword(s):  
Silicon Nitride ◽  
Temperature Gradient ◽  
Microwave Heating ◽  
Reaction Rate ◽  
Nitrogen Depletion

ABSTRACTSilicon compacts nitrided utilizing the temperature gradient inherent to microwave heating were more fully converted to silicon nitride than was possible with similar compacts nitrided isothermally. Although nitrogen depletion prevented the reaction rate in the center from exceeding that at the surface, the temperature gradient partially counteracted the effect of nitrogen depletion. Thus the microwave-heated specimens could be nitrided fully before the reduction in porosity that accompanies the reaction eliminated the diffusion of nitrogen into the compact.

scholarly journals Microwave Heating Characteristics of Emulsified Asphalt Repair Materials Incorporated with Steel Slag

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Yongfeng Wei ◽  
Jinyang Huo ◽  
Zhenjun Wang ◽  
Jiangtao Gao
Keyword(s):  
Microwave Heating ◽  
Steel Slag ◽  
Asphalt Mixture ◽  
Maximum Temperature ◽  
Interface Area ◽  
Heating Effects ◽  
Repair Materials ◽  
Three Stages ◽  
Emulsified Asphalt ◽  
Heating Technology

Emulsified asphalt needs to be cured for a certain age after demulsification to produce strength, which seriously affects the traffic opening time. In this work, microwave heating technology was applied for emulsified asphalt repair materials. Steel slag with high microwave activity was adopted to improve the performance of emulsified asphalt repair materials by microwave heating. Effects of steel slag sizes and contents on the heating rate, temperature distribution, and thermal performance of emulsified asphalt repair materials were analyzed by close microwave heating, open microwave heating, and repair simulation tests. Results show that the temperature of emulsified asphalt repair materials presents three different heating stages under microwave irradiation. The “critical point of phase transition” in the three stages is gradually advanced with the increase in steel slag content. The core temperature and maximum temperature of emulsified asphalt repair materials with different steel slag sizes are basically the same; however, the heat distribution of emulsified asphalt repair materials is significantly different. In contrast to conventional asphalt mixture, there exists a smaller temperature difference. The temperature of repairing materials can reach above 80°C. The interface area can form an embedded interface structure. Incorporation of steel slag and adoption of microwave heating are effective to improve the performance of emulsified asphalt repair materials.

Joule heating effects in MHD generator boundary layers

AIAA Journal ◽  
1983 ◽  
Vol 21 (5) ◽  
pp. 679-686 ◽  
Author(s):  
R. Kent James ◽  
Charles H. Kruger
Keyword(s):  
Boundary Layers ◽  
Joule Heating ◽  
Mhd Generator ◽  
Heating Effects

Enhanced effects of footwarmer by wearing sandals in winter office: A Swedish case study

2020 ◽  
pp. 1420326X2091397 ◽  
Author(s):  
Bin Yang ◽  
Zhe Li ◽  
Bin Zhou ◽  
Thomas Olofsson ◽  
Angui Li
Keyword(s):  
Thermal Comfort ◽  
Thermal Environment ◽  
Heating Temperature ◽  
Whole Body ◽  
Thermal Stimulus ◽  
Body Parts ◽  
Heating Effects ◽  
Localized Heating ◽  
Cooling Devices ◽  
Local Thermal Comfort

Human-centred thermal environment conditioning can guarantee thermal comfort needs of human occupants in their micro-environments by using localized heating/cooling devices. Meanwhile, less intensified thermal conditioning of unoccupied surrounding environments can achieve heating/cooling energy efficiency. The concept was originated from task/ambient conditioning, which was developed for personal comfort systems. Most of the localized heating/cooling devices are workstation based or chair based. Task conditioning would become more closely to targets (human bodies) by using special clothing materials or thermoelectric elements. From thermal physiological viewpoints, thermal stimulus to thermally sensitive body parts may generate better results for not only local thermal comfort but also for whole body thermal comfort. Thermal stimulus to the extremities (feet) has demonstrated good thermal comfort effects. Scandinavians are accustomed to outdoor harsh environments and prefer wearing heavy shoes' outdoors in winter. They have the habit of changing heavy shoes to sandals when entering offices, which give the opportunity to enhance localized heating effects of footwarmers by reducing shoes’ thermal resistance. Climatic chamber tests with 32 Nordic subjects were performed under different indoor ambient heating temperatures with/without the aid of footwarmers. With footwarmers and sandals, indoor heating temperature at 16°C was acceptable, which achieved energy efficient thermal comfort.

Advances in Microwave-Assisted Processing For Electron Microscopy

2001 ◽  
Vol 7 (S2) ◽  
pp. 1192-1193 ◽  
Author(s):  
R. T. Giberson
Keyword(s):  
Microwave Heating ◽  
Sample Processing ◽  
Closed Cavity ◽  
Microwave Assisted ◽  
Heating Effects ◽  
Microwave Component ◽  
Close Proximity ◽  
History Of ◽  
Cavity Design ◽  
Cold Spots

The history of microwave-assisted processing has been dominated by the idea that microwave heating was an integral part of the equation. The separation of a microwave component from the heating effects of the radiation during sample processing has been experimentally difficult. Combined with this difficulty has been the closed cavity design of microwave ovens. This design is typical of laboratory and household ovens and results in the formation of “hot” and “cold” spots within the chamber. These spots produce regions in close proximity to each other which have widely varying heating effects on samples.A second factor to consider with microwave heating is the effect wattage output has on rate and extent of microwave induced heating. Peak wattage outputs of all laboratory and most household microwave ovens are in excess of 650W. As a result the vast majority of all microwave-assisted protocols are based on heating parameters associated with high wattage processing.

scholarly journals Microwave treatment and drying of germinated pea

2011 ◽  
Vol 20 (No. 1) ◽  
pp. 23-30 ◽  
Author(s):  
M. Skulinová ◽  
P. Kadlec ◽  
J. Kaasová ◽  
J. Dostálová ◽  
M. Zátopková ◽  
...  
Keyword(s):  
Microwave Heating ◽  
Nutritive Value ◽  
Microwave Treatment ◽  
Grain Legumes ◽  
Soluble Carbohydrates ◽  
Trypsin Inhibitor Activity ◽  
Preliminary Treatment ◽  
Hot Air Drying ◽  
Hot Air ◽  
Heating Effects

It is possible to use germination of grain legumes as the most effective way of decreasing a high content of a-galactooligosaccharides which undesirably affect the nutritive value and acceptability of legumes. Content of a-galactooligosaccharides was reduced to 38% (Gotik cultivar) and to 45% (Grana cultivar) of the original value after 2 days of germination. The aim of further processing was to dry germinated pea to final moisture content 12–14%. Very interesting results were obtained when microwave heating was used as a preliminary treatment before hot air drying. Microwave treatment reduces the time of drying. The contents of soluble carbohydrates (sucrose, raffinose, stachyose and verbascose), proteins and trypsin inhibitor activity were determined as criteria of microwave heating effects on the chemical composition of germinated pea. Germinated pea was used for the preparation of pea soups and these pea dishes were sensory evaluated.  

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