999 resultados para Thermodynamic Cycles


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Even though it has been proved that a fully thermally coupled distillation (TCD) system minimizes the energy used by a sequence of columns, it is well-known that vapor/liquid transfers between different sections produce an unavoidable excess of vapor (liquid) in some of them, increasing both the investment and operating costs. It is proposed here to take advantage of this situation by extracting the extra vapor/liquid and subjecting it to a direct/reverse vapor compression cycle. This new arrangement restores the optimal operating conditions of some of the affected sections with energy savings of around 20–30% compared with conventional TCD columns. Various examples, including the direct and reverse vapor recompression cycles, are presented. Furthermore, in each example, all possible modes of distillation (direct, indirect and Petlyuk distillation) with and without vapor recompression cycles (VRC) are compared to ensure that this approach delivers the best results.

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The thermodynamic consistency of almost 90 VLE data series, including isothermal and isobaric conditions for systems of both total and partial miscibility in the liquid phase, has been examined by means of the area and point-to-point tests. In addition, the Gibbs energy of mixing function calculated from these experimental data has been inspected, with some rather surprising results: certain data sets exhibiting high dispersion or leading to Gibbs energy of mixing curves inconsistent with the total or partial miscibility of the liquid phase, surprisingly, pass the tests. Several possible inconsistencies in the tests themselves or in their application are discussed. Related to this is a very interesting and ambitious initiative that arose within the NIST organization: the development of an algorithm to assess the quality of experimental VLE data. The present paper questions the applicability of two of the five tests that are combined in the algorithm. It further shows that the deviation of the experimental VLE data from the correlation obtained by a given model, the basis of some point-to-point tests, should not be used to evaluate the quality of these data.

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Thermodynamics Conference 2013 (Statistical Mechanics and Thermodynamics Group of the Royal Society of Chemistry), The University of Manchester, 3-6 September 2013.

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The knowledge of thermophysical properties of liquid Co-Si alloys is a key requirement for manufacturing of composite materials by infiltration method. Despite this need, the experimental and predicted property data of the Co-Si system are scarce and often inconsistent between the various sources. In the present work the mixing behaviour of Co-Si melts has been analysed through the study of the concentration dependence of various thermodynamic, surface (surface tension and surface composition) and structural properties (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) in the framework of the Compound Formation Model (CFM) and Quasi Chemical Approximation for regular solutions (QCA). In addition, the surface tension of the Co22·5Si77.5 (in at%) eutectic alloy, that is proposed to be used as the infiltrant, has been measured by the pendant drop method at temperatures ranging from 1593 to 1773 K. The results obtained were discussed with respect to both, temperature and concentration, and subsequently compared with the model predictions and literature data.

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Recent research has highlighted that in the last few years the evolution of regional disparities in many European states has become pro-cyclical. This represents a change with respect to the predominantly anti-cyclical pattern of the 1960s and 1970s. This paper addresses the question of whether and when this change has taken place in the southern periphery of Europe, before analyzing the factors that may have played a role in such a change. The analysis relies on a regional database that includes the evolution of the GDP per capita of NUTS II regions in five European countries (France, Greece, Italy, Portugal, and Spain) between 1980 and 2000. The results of the analysis support the hypothesis of a change towards a pro-cyclical evolution of regional disparities in the cases of Italy, Portugal, and Spain, but not in those of Greece and France. A relationship between these pro-cyclical patters and the emergence of less dynamic sheltered economies is also detected in peripheral regions. This lack of dynamism is related to the fact that numerous peripheral areas in southern Europe have become increasingly dependent on factors such as transfers or public investment and employment, and therefore are less exposed to changes in market conditions.

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The emergence of widespread offshoring of information-intensive services is arguably one of the more impactful phenomena to transform business in the last ten years. A growing body of research has examined the firm-level drivers andlocation factors (i.e., the why's and where's) of services offshoring. However, little empirical research has examined the maturation sequencing (or when's) of services offshoring. Adopting industry life cycle theory as a framework, the key research questions examined in the paper are: when do different categories of offshoring services provision change from being emergent sectors to more mature ones, and how does the timing of this sequence relate to the type of service offshored. Using a database of 1420 offshore services FDI projects, we find that the value-add as well as the information sensitivity of the service category are related to when the service categories progress through the industry life cycle. Implications for future waves of service offshoring are discussed.

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Optimal currency area theory suggests that business cycle comovement is a sufficient condition for monetary union, particularly if there are low levels of labour mobility between potential members of the monetary union. Previous studies of co-movement of business cycle variables (mainly authored by Artis and Zhang in the late 1990s) found that there was a core of member states in the EU that could be grouped together as having similar business cycle comovements, but these studies always used Germany as the country against which to compare. In this study, the analysis of Artis and Zhang is extended and updated but correlating against both German and euro area macroeconomic aggregates and using more recent techniques in cluster analysis, namely model-based clustering techniques.

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• Before the financial and economic crisis, monetary policy unification and interest rate convergence resulted in the divergence of euroarea countries’ financial cycles. This divergence is deeply rooted in the financial integration spurred by currency union and strongly correlated with intra-euro area capital flows. Macro-prudential policy will need to deal with potentially divergent financial cycles, while catering for potential cross-border spillovers from domestic policies, which domestic authorities have little incentive to internalise. • The current framework is unfit to deal effectively with these challenges. The European Central Bank should be responsible for consistent and coherent application of macro-prudential policy, with appropriate divergences catering for national differences in financial conditions. The close link between domestic financial cycles and intra-euro area capital flows raises the question of whether macro-prudential policy in the euro area can be compatible with free flows of capital. Financial cycle divergence had its counterpart in the build-up of macroeconomic imbalances, so effective implementation of the Macroeconomic Imbalance Procedure would support and strengthen macro-prudential policy.