Development of Microwave Slow-Wave Comb Applicators for Soil Treatment at Frequencies 2.45 and 0.922 GHz (Theory, Design, and Experimental Study)

In agriculture and industry, it is often necessary to heat surface layers of material like soil, timber, concrete, and so on, with microwave (MW) energy. Traditional MW irradiators (antennas) cannot restrain their heating to the surface, with the energy penetrating deeply into the material. Slow-wave comb applicators can provide the required energy distribution in the surface layer. Theoretical analyses of the comb applicators used for heating were carried out and on this basis, three comb applicators were designed and made for soil treatment: two applicators Comb 1 and Comb 2 for frequency 2.45 GHz and Comb 3 for frequency 0.922 GHz. An experimental study of applicators was carried out using two MW plants: 30 kW (2.45 GHz) and 60 kW (0.922 GHz) for heating soil with moisture content in the range from 32% to 173% and density 460 to 1290 kg m−3. The study showed that comb applicators provide the following advantages: reduction in energy dissipation in material depth and release of the significant part of applied MW energy in layers close to the applicator surface. Comb applicators can provide the required soil top layer treatment (sterilization) with reasonable efficiency and can be recommended for practical use in shallow soil treatment for weed seed and pathogen control in agricultural applications. Comb applicators can also be used for effective heating and MW treatment of the surface layers of wood, concrete, bricks, plastics, and other dielectric materials.

Health-Improved Textiles Obtained by Heat Surface Ecodyeing Treatments

The central idea of the present research aims at achieving textile substrates through an efficient inclusion of a wild black cherry extract into the grafting agent-monochlorotriazinyl-β-cyclodextrin (MCT-β-CD). The methodology consists in a permanent/irreversible entrapment onto the fibres surface of the natural extract through inclusion mechanism. Exhaustion and sonication dyeing procedures were used alternatively. The obtained materials were characterized, by FT-IR and BET analysis. The experimental results reveal good adsorptive feature of the samples, due to a higher specific surface created by the inclusion complex (MCT-β-CD-dye pigment). An efficient blocking of the natural dye pigment molecules into the grafting agent’s cavity (MCT-β-CD), assumed both a stable dyeing and antimicrobial potential. The results obtained by this ecologic surface grafting method will contribute to novel key points in producing healthy natural textiles, as alternatives for single use textiles. The results provided by this research will be used as starting point for a future study targeting the obtaining of textile supports with antimicrobial performance. Other investigations like washing, rubbing and colour fastness, highlighted that dyeing treatment by sonication is extremely efficient and could be successfully applied to such items, in boosting developments.

Waste Heat Recovery From Porous LPG Gas Burner Used for Cooking

Generally in cooking devices three modes of heat transfer takes place (conduction, convection and radiation). Heat is transferred to the utensils mainly due to conduction and convection. A considerable amount of heat in the form of radiation is dissipated to the surroundings. The purpose of this project is to recover this waste heat. Surface radiation without participating media is considered in this study. Hence, copper coil is used to absorb the radiant heat and transfer it to water which run through the coil. This low temperature recovery water can be used for cooking or to keep the food hot packed or other similar low grade heat applications.