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Editor’s Choice : Influence of Magnetic Frequency on the Thermal Behaviour of Heat Transfer Equipment
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Abstract: This paper presents a description of the mathematical model developed to predict the natural frequency of a particular refrigerant or refrigerant mixture and magnetic field frequency using the one-dimensional fluid flow conservation equations. The results show the dependence of the Nusselt number on the Reynolds number in the presence and absence of magnetic field. However, the results also provide evidence of enhanced heat transfer and heat flux under magnetic field compared to without magnetic field. In addition, the results presented in the paper clearly provide evidence that the heat transmission has been consistently enhanced when magnetic field is applied. It also appears that heat transfer enhancement is greater at higher Nusselt numbers. Keywords: Magnetic field, heat transfer, enhancement, refrigerant mixtures.Download Full Article |
Editor’s Choice : Renewable Energy Sources: Global and Russian Outlook Up to 2040
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Abstract: During the period up to 2040, renewable energy sources (RES) will have the highest growth rates of all forms of energy. Based on the calculations on the world energy model incorporated in the SCANER modelling and information complex (working on the basis of optimization, econometric analysis, and balance approach), key trends in the world consumption of renewable energy sources; the share of OECD and non-OECD countries in the use of the renewable energy sources; consumption of renewable energy sources by type; end use and the impact on the electricity sector during the period up to 2040 were observed. The main finding of the paper is that RES are becoming more competitive and therefore will be used on an increasingly wide scale not only in the OECD countries, but also in the whole world. At the same time, due to the fact that RES start their take-off from a modest basis, they will only have a limited influence on the shares of hydrocarbons in the energy mix. Keywords: Renewable energy sources, energy system, energy markets, optimization model, balance approach.Download Full Article |
Editor’s Choice : Bioaugmented Hydrogen Production from Lignocellulosic Substrates Using Co-Cultures of Shigella flexneri str. G3 and Clostridium acetobutylicum X9
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Abstract: Bioaugmented fermentation of cellulosic substrates to produce biohydrogen via co-culture of isolated strains was investigated. Two mesophilic anaerobic bacterial strains, known for their ability to hydrolyze cellulosic substrates, were taken in consideration: Shigella flexneri str. G3, which shows high cellulolytic activity but cannot ferment oligosaccharides to bioenergy, and Clostridium acetobutylicum X9, able to convert microcrystalline cellulose into hydrogen. The ability of the selected strains to effectively convert different cellulosic substrates to hydrogen was tested on carboxymethyl cellulose (AVICEL), as well as pretreated lignocellulosic material such as Bermuda grass, corn stover, rice straw, and corn cob. Results showed that co-culture of Shigella flexneri str G3 and Clostridium acetobutylicum X9 efficiently improved cellulose hydrolysis and subsequent hydrogen production from carboxymethyl cellulose. Hydrogen production yield was enhanced from 0.65 mol H2 (mol glucose)−1 of the X9 single culture to approximately 1.5 mol H2 (mol glucose)−1 of the co-culture, while the cellulose degradationefficiency increased from 50% to 95%. Co-culture also efficiently improved hydrogen production from natural lignocellulosic materials (which was up to 4-5 times higher than mono-culture with X9), with the highest performance of 24.8 mmol L-1 obtained on Bermuda grass. The results demonstrate that co-culture of S. flexneri G3 and C. acetobutylicum X9 was capable of efficiently enhance cellulose conversion to hydrogen, thus fostering potential biofuel applications under mesophilic conditions. Keywords: Bioaugmentation, co-culture, lignocelluloses, saccharification, biohydrogen.Download Full Article |
Editor’s Choice : Characteristics of Residential Tracker Accuracy in Quantified Direct Beam Irradiance and Global Horizontal Irradiance
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Abstract: An accurate solar tracker matches array angles with solar angles throughout the day. Many studies have used the power produced by a tracked PV array as a proxy to characterize a tracker’s accuracy. However, it is difficult to decouple the effects of tracker performance from other effects on power output. It was not found in the literature reviewed that there are studies that determine the accuracy of solar trackers by directly measuring the tracker angles. This study was an experiment to determine the accuracy of two small commercially available non-algorithm based solar trackers: the Zomeworks UTR-020 passive one axis solar tracker, and the Wattsun AZ-225 active electro-optical two axis solar tracker. Accuracy of the trackers was determined by measuring the tracking angles under varying conditions including direct beam irradiation (DBI) and global horizontal irradiance (GHI), and comparing to calculated sun angles. The results showed that the average azimuth angle accuracy of the Zomeworks UTR-020 is 75%, the average azimuth angle accuracy of the Wattsun AZ-225 is 88%, and the average elevation angle accuracy of the Wattsun is 89%. In addition, the results showed a weak correlation between the azimuth accuracy of the Zomeworks and DBF, a strong correlation between the azimuth accuracy of the Wattsun and DBF, and a moderate correlation between the elevation accuracy of the Wattsun and DBF. Moreover, the azimuth accuracy of the Wattsun was always higher than that of the Zomeworks under all DBF and GHI conditions. Keywords: Solar Tracker, Accuracy, Tracking Error, Non Algorithm Based, Solar Tracking Angles.Download Full Article |
