16th International Conference
on Microwave and High Frequency Heating

18-21 September 2017, Delft, The Netherlands
14:30   Process intensification with electromagnetic energy (2)
Chair: Georgios Stefanidis
14:30
15 mins
ALCOHOLIC FERMENTATION IN THE PRESENCE OF MICROWAVES
Ioan Calinescu, Alexandru Vlaicu, Petre Chipurici, Daniel Ighigeanu
Abstract: Bio-ethanol is the main biofuel, obtained by glucose fermentation. To increase the productivity, microwaves (MWs) irradiation of yeasts gains interest as intensification technique. In food and beverage industry, microwaves are mainly used to destroy microorganisms, i.e. sterilization at low temperatures1,2. Only few information related to the intensification of biological process due to MWs have been published 3,4,5. The fermentation of glucose in the presence of Saccharomyces cerevisiae under continuous MWs irradiation was studied. A multimode MW applicator was used, the MW energy was fed from a solid-state MW generator using a coaxial antenna. Such a constructive solution makes possible the irradiation of fermentation broth with small, perfectly controlled radiation doses. MWs irradiation was performed simultaneously with cooling and mixing of fermentation broth, to guarantee an isothermal regime. The temperature distribution in the fermentation vessel was modeled in Comsol Multiphysics®, the results matching the obtained experimental ones. The experiments proved that MWs irradiation increases the rate of fermentation, stimulating yeast cells’ activity during fermentation, irrespective of the concentrations of glucose and yeast. Under optimal conditions of irradiation (SAR=25 W/kg), the rate of fermentation is up to 40% higher than the rate obtained in conventional fermentation, for the same operating conditions.
14:45
15 mins
HIGH POWER MODE TRANSDUCER
Joel Mclean, David Mclean
Abstract: A High Power Microwave Mode Transducer has been developed. It transforms the TE10 mode (electric field transverse to the direction of propagation) of a rectangular wave guide to a TM01 mode (magnetic field transverse to direction of propagation) in a cylindrical wave guide. The development involved a systematic approach including extensive simulation studies, design, fabrication and both low and high power testing. High spectral mode purity with a power transfer efficiency of 89.7 % (based on simulations) was achieved and verified for the fabricated model using thermal mapping techniques. The mode transducer is analysed in terms of its voltage break down limits, wall losses, load coupling and reflection coefficient and exceeds all the project specifications goals.
15:00
15 mins
COMPLEXITY AND CHALLENGES IN NON-CONTACT HIGH-TEMPERATURE MEASUREMENTS IN MICROWAVE-ASSISTED CATALYTIC REACTORS
Lalit Gangrude, Guido Sturm, Andrzej Stankiewicz, Georgios Stefanidis
Abstract: The history of microwave (MW) technology confirms its rapid development after the thermal effects of microwave heating were discovered in the 1940s[1]. Since then, microwave heating has been used for various industrial and research applications. However, accurate temperature measurement in microwave heated reactors is complex and may become a significant hurdle in the development of optimized microwave heated reactors[2]. In this work, the challenges in non-contact temperature measurements (specifically in the 300-1000°C temperature range) in microwave-heated catalytic reactors are presented for the exemplary case of methane dry reforming on Pt-on-C catalyst. A custom-designed microwave cavity (Figure 1) is used to focus the microwave field on the catalyst and monitor its temperature distribution in a 2D fashion. A methodology to study temperature distribution in the catalytic bed using a properly calibrated thermal camera in combination with a thermocouple is demonstrated.
15:15
15 mins
PROCESSING AND CHARACTERIZATION OF FUNCTIONALLY GRADED COMPOSITE CLADDING ON AUSTENITIC STAINLESS STEEL SUBSTRATE THROUGH MICROWAVE HEATING
Sarbjeet Kaushal, Dheeraj Gupta, Hiralal Bhowmick
Abstract: In the present investigation microwave assisted functionally graded clads (FGCs) of Ni-Cr3C2 materials were produced using 2.45 GHz and variable microwave power level from 180-900 W. The processing time was optimized at a power level of 900 W and it was from 300 s to 360 s for different clad layers. The processed FGCs were characterized using various techniques like SEM/EDS, XRD and Vickers microhardness. Microstructural analysis of the developed FGC reveals that the Cr3C2 particles are uniformly distributed and embedded inside Ni matrix. The presence of NiSi, FeNi3, and Cr23C6 were confirmed from XRD study, which resulted in an increase in the microhardness of the clad layers. The maximum FGC microhardness of 550 ± 40 HV was achieved in the top FGC layer.