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The modern gas turbines need to run at very high inlet temperature to promote their power output. Thus, improvements in cooling technologies play a significant role for enhancing the gas turbine blade life. In this paper, thermohydraulic performance (THP) of a two-pass square channel with inclined ribs at 45° was scrutinized employing the k – ε realizable model with enhanced wall treatment in ANSYS Fluent. The calculations were performed for the rib pitch to height ratio (p / e) of 5-10, rib height to hydraulic diameter ratio (e / D h ) of 0.1-0.2, and Reynolds number (Re) of 20,000-40,000. Detailed analysis of the flow structure in a double passage square duct was carried out to understand the interaction of the rib and bend-induced secondary flows and its contribution to heat transfer enhancement for the rib configurations with distinct p / e and e / D h , which was not available in any other existing numerical or experimental investigations. The results revealed that the ribs with higher e / D h generated the stronger stream-wise secondary flows which led to the augmentation of the cooling performance with the disadvantage of pressure loss increment. The maximum THP of 26.55% was achieved with the ribbed configuration having p / e = 5 and e / D h = 0.1 at Re = 20,000. The new correlations were developed from the computational data to predict the normalized Nusselt number and friction factor (Nu / N u 0 and f / f 0 , where 0 is the correlation), taking the e / D h and flow Re into consideration. [ABSTRACT FROM AUTHOR]

The sun is an abundantly available and clean renewable energy source. Therefore, solar energy offers significant potential for mitigating climate change and reducing emissions from burning fossil fuels in the future. Solar chimney power plants (SCPPs) have a technical capability for meeting the massive sustainable power production. Basic parts of SCPP system are the chimney, turbine, and collector. The geometric dimensions of the components are the crucial factors for improving the solar chimney efficiency. The goal of this work is to analyse the influences of the inclination angle (θ) at chimney inlet on performance characteristics of the system by employing RNG k − ε turbulence model coupled with discrete ordinate (DO) solar ray tracing method via ANSYS Fluent CFD software. The model is built by taking into consideration geometric parameters of Manzanares plant and verified with its measurements. The innovative chimney entrance configurations are produced by altering the chimney entrance slope (θ = 50 °–80°) with the geometrical dimensions of the chimney, collector, and fillet keeping constant. The computational results display that the new chimney configurations improve the maximum velocity, system power output, and turbine pressure drop. The peak velocity of 18.1 m/s is gained for the configuration with θ = 80 ° compared to that of 14.3 m/s obtained for the base model having θ = 45 ° at 1000 W/m2. Besides, this configuration enhances power output to 61.5 kW with a rise of 24.5% compared to the base model with a power output of 49.1 kW at 1000 W/m2. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate the effects of different mixture ratios of sorghum (S) and cluster bean (CB) on fermentation parameters, nutritional composition, and gas-methane production of mixture silages. Five different mixture ratios (100%S, 75%S+25%CB, 50%S+50CB, 25%S+75%CB and 100%CB) were used in this study. Effects of mixture ratios on entire parameters were highly significant (p ≤ 0.01). Decreasing ADF and NDF ratios and increasing crude protein, ash and oil contents and condensed tannin levels were observed with increasing cluster bean ratios of the mixtures. However, cluster beans reduced WSC and lactic acid and increased pH, butyric acid and ethanol contents. The lowest Fleig score was obtained from cluster bean silage (100%CB). The lowest gas-methane production was obtained from cluster bean silage and the greatest ME and NEL values were obtained from sorghum silage (100%S). The best OMD values were obtained from sorghum silage and 75%S +25%CB mixture silage. The present findings revealed that a 50%S+50%CB mixture yielded high nutritional composition and good fermentation parameters. [ABSTRACT FROM AUTHOR]

The use of fossil fuels for generating power has leaded to the reduction of fossil fuel resources and many adverse influences involving climate change and environmental pollution. Solar energy has a potential to provide eco-friendly energy with a great energy supply for producing heat and electricity. Basic parts of the system are the collector, chimney and turbine. The collector is a vital component of the system and its geometrical features noticeably influence the power plant efficiency. In the current work, a three dimensional computational fluid dynamics (CFD) simulation of a SCPP based on the Manzanares prototype is performed to scrutinize the impact of collector entrance height (He) ranging from 0.75 m to 2 m on the solar chimney power output. Computational model is developed by employing RNG k-ε turbulence and discrete ordinates (DO) coupled with solar ray tracing models through ANSYS Fluent software. The model is validated using measured data published in the literature. The numerical results reveal that reducing He improves maximum velocity (Vmax), power output and pressure difference in the turbine at the expense of decreasing air mass flow rate. The highest velocity of 19.45 m/s is achieved with He = 0.75 m and Vmax enhances by 36.20% compared to base model with He = 1.85 m at 1000 W/m2. Besides this configuration provides the maximum power output of 66.51 kW and augments power output to 31.74% compared to the base case at 1000 W/m2. [ABSTRACT FROM AUTHOR]

The technical capability of proton exchange membrane fuel cell (PEMFC) offers an encouraging solution to produce sustainable and clean power. The gas diffusion layer (GDL) is a pivotal part of the PEMFC which plays a critical role in providing a pathway for reactant and product. GDL electrically connects the catalyst layer to the current collector and conducts heat generated in the electrochemical reactions. The thermal conductivity is one of the most important transport properties of the GDL that affects heat transfer across the cell and the overall performance. In the current work, the impact of the isotropic GDL thermal conductivity ranging 1-100 W/mK at 0.4 and 0.6 V on the cell efficiency is studied computationally using ANSYS Fluent PEMFC module. The results indicate that an increase in the isotropic GDL thermal conductivity enhances the fuel cell current density considerably up to 20 W/mK with the more homogeneous temperature distribution and lower temperature across PEMFC at 0.4 and 0.6 V. After this, the impact of the GDL thermal conductivity on the performance diminishes and thus the current density is nearly constant with further increase in isotropic GDL thermal conductivity at both cell voltages. The peak current density of 1.37 A/cm2 is gained at 100 W/mK. The power function provided a good fit with the calculated data. Oxygen consumption and water production augments with higher thermal conductivity, especially the regions above the cathode current collector ribs. [ABSTRACT FROM AUTHOR]

PEM fuel cell (PEMFC) is a potential candidate for future source of power used in different applications such as transportations, stationary and portable power. PEMFC consists of different parts including membrane, bipolar plate, flow channel, gas diffusion and catalyst layers. Membrane is one of the most important components of a PEMFC and its physical and geometrical features significantly affect PEMFC efficiency. In this paper, a three-dimensional, single-phase computational model has been improved to scrutinize membrane thickness effect on the PEM fuel cell performance using the ANSYS PEM Fuel Cell Module. Membrane thicknesses are in the range of 0.0127 to 0.189 mm. The results reveal that a decrease in membrane thickness augments the current density at 0.4 and 0.6 V. The peak current density of 3.12 A/cm2 is achieved with 0.027 mm membrane thickness compared with the model current density of 1.26 A/cm2 obtained by the model with 0.128 mm membrane thickness at 0.4 V. Oxygen consumption. Water production is also enhanced with reducing membrane thickness to 0.4 and 0.6 V. However, the changed thickness of the membrane has a negligible impact on impact pressure drop in the flow channel. It is found that optimization of membrane thickness is necessary for attaining high efficiency. [ABSTRACT FROM AUTHOR]

Background and Objectives: The nutritional value of the sprouts has gained interest in recent years because of supplying to fiber, vitamins, minerals, and bioactive compounds such as antioxidants into the diet. The aim of the present study was to reveal the nutritional characteristics of the different sorghum genotypes exposed to sprouting process. For this purpose, some biochemical characteristics and basic mineral profiles of the sorghum sprouts were investigated. Findings: According to the results, protein content ranged between 12.17% and 32.24% while the lowest total starch content was determined as to be 3.37% and the highest was 32.71%. Besides, dietary fiber content was in the range of 30.27%–46.42%. Total phenolic content and antiradical activity values of the sprouts were determined as in the range of 3.61–8.42 mg GAE/g and 11.63%–19.51%, respectively. Conclusion: The results showed that the sprouting process improved the nutritional quality of sorghum compared to grains and also significant variation was observed among the genotypes in terms of examined properties. Significance and Novelty: The results showed that the nutritional parameters especially phytic acid levels of the sorghum grains could be decreased by sprouting process. [ABSTRACT FROM AUTHOR]

In this study, aerial parts of dandelion were exposed to extraction by different solvents such as water, ethanol, methanol and glycerol and also their aqueous mixtures to compare the effect of extraction solvents on bioactive performance of the dandelion and also to show the effectiveness of hydroglycerolic extraction which is a green extraction process. Total phenolic content (TPC) and total flavonoid content (TFC) of the extracts were determined and also antiradical scavenging activities and antioxidant capacities of the samples were also evaluated. TPC and TFC of the samples ranged between 4.63-21.28 mg GAE/g and 1.16-14.38 mg CE/g, respectively. The highest TPC and TFC values were determined in aqueous extract of glycerol (75% w/w) compared to other solvents. Additionally, ABTS.+ and DPPH radical scavenging activity and ferric reducing capacity and antioxidant capacity values were determined for the extracts and the best solvent was also aqueous glycerol (75% w/w). [ABSTRACT FROM AUTHOR]