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Binary Systems with Geothermal Fluid Pressurization to Avoid Flashing: Energy Evaluation of Down-Hole Pump Cooling Below Geothermal Fluid Temperature
No full textThe pressurization of the liquid geothermal fluid at a
suitable depth in the well, by means of an electric powered
pump, is an established technique to avoid flashing in the
well. However this technique is limited by the maximum
temperature which can be sustained by the windings of the
pump motor. In the present paper, the basic feasibility and
energy cost of cooling the windings are evaluated. The
proposed solution consists of a cooling loop made by an
evaporator fed with water, which removes the heat
generated in the motor windings, a downward water pipe,
which feeds the evaporator, an upward steam pipe which
removes the evaporated steam and brings it at well head and
a condenser which rejects the removed heat into the
ambient; a pump is also needed in order to pressurize the
cooling loop and avoid evaporation in the downward water
pipe. The size of the pipes to be put into the well for the
cooling system is preliminarily dealt with: when feasible,
this technique can broaden the application range of the
binary cycle technology. Concerns about the environmental
impact and reservoir exploitation point out that the adoption
of the binary cycle is particularly advantageous in many
aspects: it is well known that emissions in the atmosphere
of harmful or undesired components (for example: H2S,
CO2) are to be avoided: in binary power plants the all-liquid
geothermal brine can be easily re-injected after use. This
solution therefore gives the chance to treat the
noncondensables gases as dissolved in the liquid brine
instead of as gasified in the vapor phase. Re-injection has
also a beneficial effect on the reservoir exploitation
Geothermal binary plants utilising an innovative non-flammable azeotropic mixture as working fluid
No full text
Comparison of Enhanced Organic Rankine Cycles for Geothermal Power Units
Full text linkBinary cycles have drawn the attention as a technical solution for the geothermal power production. This attention is mainly due to
the huge potential of medium-low temperature geothermal sources, typically exploited by means of a binary cycle, and the
relevance of the environmental concern, which can be conveniently dealt with by means of a closed cycle. The binary cycle has
been therefore the object of an extended research activity, in order to attain higher plant performance. A crucial matter is the
improvement of the heat introduction process. For a given geothermal fluid in liquid state, i.e. for a variable temperature heat
source, in a conventional ORC the working fluid evaporation process is responsible for an important second law loss: removal of
this loss allows greater power and possibly higher cycle efficiency to be attained. Aim of the present paper is to investigate and
compare recently proposed technical solutions based on the current technology, which do not entail considerable operating risk or
relevant investment; they can however lead to an improvement in plant performance and economics. The selected cycle options
were dealt with in the open literature, and try to reduce the heat introduction second law loss: in the first one, the so called OFC,
this loss is strongly reduced, because heat is introduced in the cycle when the working fluid is in liquid phase, but a dissipative
flash process is then required. In the second one, the so called Pinch Point Smoother, this loss is reduced because the working fluid
heating curve is smoothed by means of a flow split, which allows a fraction of the working fluid flow to evaporate at a pressure
lower than the pressure of the main flow, but mechanical recompression is then required to inject the separated flow fraction into
the turbine. The result of comparison may depend both on the temperature level of thermal sources involved and on the working
fluid selected: the present paper will discuss several examples, representative of geothermal applications, and try to assess whether
the adoption of these solutions can be convenient for geothermal exploitation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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