ANALYSIS OF A COMBINED BRAYTON/RANKINE CYCLE WITH TWO REGENERATORS IN PARALLEL

This work presents a configuration of two regenerators in parallel for a power generation Brayton/Rankine cycle where the output power is 10 MW. The working fluids considered for the Brayton and Rankine cycles are air and water, respectively. The addition of a regenerator with the previous existing cycle of this kind resulted in the addition of a second-stage turbine in the Rankine cycle of reheat. The objective of this modification is to increase the thermal efficiency of the combined cycle. In order to examine the efficiency of the new configuration, it is performed a thermodynamic modelling and numerical simulations for both cases: a regular Brayton/Rankine cycle and the one with the proposed changes. At the end of the simulations, the two cycles are compared, and it is seen that the new configuration reaches a 0.9% higher efficiency. In addition, the vapor quality at the exit of the higher turbine is higher, reducing the required mass flow rate in 14%

Biosorption of the Copper and Cadmium Ions - a Study through Adsorption Isotherms Analysis

In this work, the biosorption process of copper-cadmium ions binary mixture by using marine algae Sargassum filipendula was investigated. A set of experiments was performed to obtain equilibrium data for the given batch operational conditions - T=30°C, pH=5. The interpretation of equilibrium data was based on the binary adsorption isotherms models in the Langmuir and Freundlich forms. To evaluate the models parameters, nonlinear identification procedure was used based on the Least Square statistical method and SIMPLEX local optimizer. An analysis of the obtained results showed that the marine algae biomass has higher affinity to copper ions than to cadmium ones. The biomass maximum adsorption capacity for the binary system was about 1.16 meq/g

Impact of the \u3cem\u3eBrachiaria\u3c/em\u3e Hybrids on Both Soil Health and Carbon Stock on Livestock Production

Pastures occupy 30% of Earth and 80% of the entire agricultural area of the planet. To ensure food to the world and contribute to the quality of the environment, pasture-based animal production systems will also have to undergo through a more intense evolution. The intensification of tropical grasslands is an important strategy of land utilization in developing countries, contributing to increase production and minimize environmental impact through the best management practices. In this sense, the use of Brachiaria hybrids represents an excellent option, since combining the best traits of different Brachiaria species, with higher nutritive value, forage, and seed yield. Here we have evaluated six Brachiaria hybrids’ effects on both soil health and carbon stock. We observed that in all Brachiaria genotypes the mean carbon stock varied significantly in at least two soil depth categories. In general, carbon stock tends to get smaller as soil depth increases. Enzyme activity analysis showed there were no significant differences in the mean enzyme activity except in hybrid GP 3660 for β-glucosidase enzyme. Therefore, the adoption of Brachiaria hybrids might also help farmers to produce in an environmentally friendly manner, due to the potential benefits of Brachiaria to soil life enzyme activity and carbon mitigation

The Isotropy of Compact Universes

We discuss the problem of the stability of the isotropy of the universe in the space of ever-expanding spatially homogeneous universes with a compact spatial topology. The anisotropic modes which prevent isotropy being asymptotically stable in Bianchi-type $VII_h$ universes with non-compact topologies are excluded by topological compactness. Bianchi type $V$ and type $VII_h$ universes with compact topologies must be exactly isotropic. In the flat case we calculate the dynamical degrees of freedom of Bianchi-type $I$ and $VII_0$ universes with compact 3-spaces and show that type $VII_0$ solutions are more general than type $I$ solutions for systems with perfect fluid, although the type $I$ models are more general than type $VII_0$ in the vacuum case. For particular topologies the 4-velocity of any perfect fluid is required to be non-tilted. Various consequences for the problems of the isotropy, homogeneity, and flatness of the universe are discussed.Comment: 22 pages in LaTeX2e with the amsmath packag

NUMERICAL STUDY OF A TRIANGULAR FIN INSERTED IN A SQUARE CAVITY WITH UPPER SLIDING SURFACE SUBJECTED TO A MIXED CONVECTION EFFECT

This article investigates numerically, using the Constructal Design method, a system that combines a square cavity with upper sliding wall and a triangular fin subjected to the mixed convection effect. The objectives are to evaluate the influence of the fin aspect ratio (H1/L1) on the average Nusselt number on the fin surface and to analyze the effect of the fraction of the area of the triangular fin relative to the square cavity (φ). The proposed problem is assumed two-dimensional, laminar, incompressible and steady flows. For the buoyancy forces it is considered the Boussinesq approximation. In order to generalize the results, the problem is solved in dimensionless form. The fluid flowing through the cavity presents the thermophysical properties defined by the Prandtl number (Pr = 0.71). The buoyancy force in the flow is defined by the Rayleigh number (RaH = 104), while the flow regime is governed by the Reynolds number (ReH = 102). The optimum fin geometry that maximizes the heat transfer between the finned cavity and the surrounding fluid is obtained through the Constructal Design method. The numerical solution of the conservation equations of mass, momentum and energy is calculated with the finite volume method, using the commercial fluid dynamics software FLUENT®. The geometry and mesh computational domain were developed in GAMBIT® package. As results, it was found that the optimal configurations of H1/L1 presented a gain in the thermal performance of up to 15% in relation to the other geometries. In addition, the heat transfer has great dependence on the variation of the fraction of area (φ)

Addition of nitrogen and potassium via fertigation on the quality of Syrah wines produced on the São Francisco Valley, Brazil.

The objective of this study was to evaluate the influence of different nitrogen and potassium doses by fertigation on the quality of Syrah red wines

Updated Three-Stage Model for the Peopling of the Americas

Background: We re-assess support for our three stage model for the peopling of the Americas in light of a recent report that identified nine non-Native American mitochondrial genome sequences that should not have been included in our initial analysis. Removal of these sequences results in the elimination of an early (i.e.,40,000 years ago) expansion signal we had proposed for the proto-Amerind population. Methodology/Findings: Bayesian skyline plot analysis of a new dataset of Native American mitochondrial coding genomes confirms the absence of an early expansion signal for the proto-Amerind population and allows us to reduce the variation around our estimate of the New World founder population size. In addition, genetic variants that define New World founder haplogroups are used to estimate the amount of time required between divergence of proto-Amerinds from the Asian gene pool and expansion into the New World. Conclusions/Significance: The period of population isolation required for the generation of New World mitochondrial founder haplogroup-defining genetic variants makes the existence of three stages of colonization a logical conclusion. Thus, our three stage model remains an important and useful working hypothesis for researchers interested in the peopling of th

Addition of nitrogen and potassium via fertigation on the quality of Syrah wines produced on the São Francisco Valley, Brazil.

The objective of this study was to evaluate the influence of different nitrogen and potassium doses by fertigation on the quality of Syrah red wines

Resgate e Purificação de Arroz do Tipo "Cachinho" em Propriedades Familiares.

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