Saturated Critical Heat Flux in a Multi-Microchannel Heat Sink Fed by a Split Flow System

An extensive experimental campaign has been carried out for the measurement of saturated critical heat flux in a multi-microchannel copper heat sink. The heat sink was formed by 29 parallel channels that were 199 μm wide and 756 μm deep. In order to increase the critical heat flux and reduce the two-phase pressure drop, a split flow system was implemented with one central inlet at the middle of the channels and two outlets at either end. The base critical heat flux was measured using three HFC Refrigerants (R134a, R236fa and R245fa) for mass fluxes ranging from 250 to 1500 kg/m2 s, inlet subcoolings from −25 to −5 K and saturation temperatures from 20 to 50 °C. The parametric effects of mass velocity, saturation temperature and inlet subcooling were investigated. The analysis showed that significantly higher CHF was obtainable with the split flow system (one inlet–two outlets) compared to the single inlet–single outlet system, providing also a much lower pressure drop. Notably several existing predictive methods matched the experimental data quite well and quantitatively predicted the benefit of higher CHF of the split flow

Pendenza della condizione. Aspettativa di diritto. Atti di disposizione

La situazione giuridica di aspettativa sia caratterizzata da due elementi essenziali: uno, sostanziale, rappresentato dalla necessaria presenza di un interesse alla conservazione, in vista della sua realizzazione, del contenuto negoziale; e uno formale, consistente nell'insieme di poteri, di natura conservativa e strumentale, posti a garanzia del raggiungimento del risultato avuto di mira. Il problema di fondo è quello di verificare se e in che misura sia possibile configurare una situazione di aspettativa tutte le volte in cui si riscontri la esistenza di una pendenza giuridicamente tutelata. La presenza di effetti preliminari e conservativi non sempre assurge a situazione giuridica di aspettativa. La situazione giuridica di aspettativa non è ricostruibile come categoria unitaria, né come diritto soggettivo autonomo; l’esigenza di conservazione gode di una protezione diversamente modulata a seconda della fattispecie a cui è correlata e, soprattutto, della particolare natura degli interessi in gioco che determinano la pendenza.The legal situation of expectation is characterized by two essential elements: one, substantial, represented by the necessary presence of an interest in the preservation to its realization of the negotiating content ;and a formal one, consisting of a set of powers of a conservative and instrumental nature, designed to guarantee the achievement of the interest pursued. The problem is to verify if and to what extent it is possible to configure an expectation situation every time that there is evidence of the existence of a legally protected slope.The presence of preliminary and conservative effects does not always lead to a legal situation of expectation. The legal situation of expectation can not be reconstructed as a unitary category, nor as an autonomous subjective right; the need for conservation enjoys a differently modulated protection depending on the case to which it is related and, above all, on the particular nature of the interests involved that determine the slope

EXPERIMENTS DURING FLOW BOILING OF A R22 DROP-IN: R422D ADIABATIC PRESSURE GRADIENTS

R22, the HCFC most widely used in refrigeration and air-conditioning systems in the last years, is phasing-out. R422D, a zero ozone-depleting mixture of R125, R134a and R600a (65.1%/31.5%/3.4% by weight, respectively), has been recently proposed as a drop-in substitute. For energy consumption calculations and temperature control, it is of primary importance to estimate operating conditions after substitution. To determine pressure drop in the evaporator and piping line to the compressor, in this paper the experimental adiabatic pressure gradients during flow boiling of R422D are reported for a circular smooth horizontal tube (3.00 mm inner radius) in a range of operating conditions of interest for dry-expansion evaporators. The data are used to establish the best predictive method for calculations and its accuracy: the Moreno-Quibèn and Thome method provided the best predictions for the whole database and also for the segregated data in the annular flow regime. Finally, the experimental data have been compared with the adiabatic pressure gradients of both R22 and its much used alternative R407C available in the literature

Carbon Dioxide Heat Transfer Coefficients And Pressure Drops During Flow Boiling: Assessment Of Predictive Methods

Among the alternatives to the HCFCs and HFCs, carbon dioxide emerged as one of the most promising environmentally friendly refrigerants. In past years many works were carried out about CO2 flow boiling and very different two-phase flow characteristics from conventional fluids were found. In order to assess the best predictive methods for the evaluation of CO2 heat transfer coefficients and pressure gradients in macro-channels, in the current article a literature survey of works and a collection of the results of statistical comparisons available in literature are furnished. In addition the experimental data from University of Naples are used to run a deeper analysis. Both a statistical and a direct comparison against some of the most quoted predictive methods are carried out. Methods implemented both for low–medium pressure refrigerants and specifically developed for R744 are used in the comparison. Some general indications about the choice of the predictive methods dependently on the operating conditions are given

Multiscale Geometric Methods for Data Sets II: Geometric Multi-Resolution Analysis

Data sets are often modeled as point clouds in $R^D$, for $D$ large. It is often assumed that the data has some interesting low-dimensional structure, for example that of a $d$-dimensional manifold $M$, with $d$ much smaller than $D$. When $M$ is simply a linear subspace, one may exploit this assumption for encoding efficiently the data by projecting onto a dictionary of $d$ vectors in $R^D$ (for example found by SVD), at a cost $(n+D)d$ for $n$ data points. When $M$ is nonlinear, there are no "explicit" constructions of dictionaries that achieve a similar efficiency: typically one uses either random dictionaries, or dictionaries obtained by black-box optimization. In this paper we construct data-dependent multi-scale dictionaries that aim at efficient encoding and manipulating of the data. Their construction is fast, and so are the algorithms that map data points to dictionary coefficients and vice versa. In addition, data points are guaranteed to have a sparse representation in terms of the dictionary. We think of dictionaries as the analogue of wavelets, but for approximating point clouds rather than functions.Comment: Re-formatted using AMS styl

Upper limits to surface force disturbances on LISA proof masses and the possibility of observing galactic binaries

We report on the measurement of parasitic surface force noise on a hollow replica of a LISA (Laser Interferometer Space Antenna for the observation of gravitational waves) proof mass surrounded by a faithful representation of its in flight surroundings, namely the capacitive sensor used to detect proof-mass motion. Parasitic forces are detected through the corresponding torque exerted on the proof mass and measured with a torsion pendulum in the frequency range 0.1 30 mHz. The sensor electrodes, electrode housing and associated readout electronics have the same nominal design as for the flight hardware, including 4 mm gaps around the proof mass along the sensitive laser interferometry axis. We show that the measured upper limit for surface forces would allow detection of a number of galactic binaries signals with signal to noise ratio up to approximately 40 for 1 year integration. We also discuss how the flight test under development, LISA Pathfinder, will substantially improve this limit, approaching the performance required for LISA.Comment: 3 Figures. Submitted to Physical Review Letter

Fundamentos conceituais para abordagens de gestão da inovação em bibliotecas

The objective of this study is to highlight the key concepts and approaches to innovation. Identifying characteristics and relevant theoretical frameworks to future studies on innovation in libraries as organization predominantly public and non-profit. The main justification by the recognition of the importance of innovation in libraries and need to theoretical basis for the issue of development in the innovation management occurs predominantly in the manufacturing industry and related products. This is a theoretical essay, qualitative, conceptual and analytical nature. It is hoped the results of this study can contribute to the theoretical basis for the development of future studies on innovation in libraries.El objetivo del estudio es evidenciar los principales conceptos y abordajes sobre innovación para identificar las características y encuadramientos teóricos pertinentes para los estudios sobre innovación en bibliotecas como organizaciones predominantemente públicas y sin fines de lucro. El estudio se justifica por el reconocimiento de la importancia de la innovación en las bibliotecas y por la necesidad de fundamentación teórica para el desarrollo del tema en el ámbito de la gestión de la innovación cuya concentración se da predominantemente en la industria de manufactura y vinculada a los productos. Se trata de un ensayo teórico, de naturaleza cualitativa, conceptual y analítica. Se espera que los resultados de este estudio puedan contribuir en la fundamentação teórica para el desarrollo de estudios futuros sobre la innovación en bibliotecas.O objetivo do estudo é evidenciar os principais conceitos e abordagens sobre inovação para identificar as características e enquadramentos teóricos pertinentes aos estudos sobre inovação em Bibliotecas como organizações predominantemente públicas e sem fins lucrativos. Justifica-se pelo reconhecimento da importância da inovação nas Bibliotecas e pela necessidade de fundamentação teórica para o desenvolvimento do tema no âmbito da gestão da inovação cuja concentração se dá predominantemente na indústria de manufatura e relacionada a produtos. Trata-se de um ensaio teórico, de natureza qualitativa, conceitual e analítica. Espera-se com os resultados deste estudo possam contribuir na fundamentação teórica para o desenvolvimento de estudos futuros sobre a inovação em Bibliotecas

Thermo-economic Design and Optimization of Cooling Systems Employed in Cruise Ship

The recovery of the available waste heat from the operating engines of a modern cruise ship plays an important role in the reduction of the environmental impact of these huge means of transport. The cooling load required by the ship passengers can be handled with innovative air-conditioning systems that employ a vapor single-phase ejector and are fed by waste heat. On the contrary, these systems are usually more expensive than vapor compression cycles, representing the conventional technology. In this paper, a thermo-economic-environmental analysis of a combined cooling system for a cruise ship operating in the Baltic Sea is proposed. Two different cooling plants are compared, namely a typical vapor compression cycle and a multiejector hybrid ejector cycle integrated with a cold storage tank aiming to buffer the load variations. The approach is numerical, and the simulations are carried-out with dedicated sub-models for each component. Volumetric machines (pumps, compressor) are modeled through phenomenological equations, calibrated and validated on real data, whereas the heat exchangers are simulated by using specific heat transfer prediction methods and typical geometries. The objective is to size the whole system and optimize the tank size and the control strategy, to minimize the investment cost and maximize the seasonal performance. Also, an economic comparison, concerning the total costs (investments costs plus operating costs) between the solution chosen and the reference one has been carried out considering the fuel cost as a parametric input. Finally, an environmental analysis is performed to assess the reduction in pollutant emissions with the proposed system

Thermo-economic Design and Optimization of Cooling Systems Employed in Cruise Ship

The recovery of the available waste heat from the operating engines of a modern cruise ship plays an important role in the reduction of the environmental impact of these huge means of transport. The cooling load required by the ship passengers can be handled with innovative air-conditioning systems that employ a vapor single-phase ejector and are fed by waste heat. On the contrary, these systems are usually more expensive than vapor compression cycles, representing the conventional technology. In this paper, a thermo-economic-environmental analysis of a combined cooling system for a cruise ship operating in the Baltic Sea is proposed. Two different cooling plants are compared, namely a typical vapor compression cycle and a multiejector hybrid ejector cycle integrated with a cold storage tank aiming to buffer the load variations. The approach is numerical, and the simulations are carried-out with dedicated sub-models for each component. Volumetric machines (pumps, compressor) are modeled through phenomenological equations, calibrated and validated on real data, whereas the heat exchangers are simulated by using specific heat transfer prediction methods and typical geometries. The objective is to size the whole system and optimize the tank size and the control strategy, to minimize the investment cost and maximize the seasonal performance. Also, an economic comparison, concerning the total costs (investments costs plus operating costs) between the solution chosen and the reference one has been carried out considering the fuel cost as a parametric input. Finally, an environmental analysis is performed to assess the reduction in pollutant emissions with the proposed system

Cultura e estresse psicológico

Examining the influence of cultural factors on psychological distress, relative to other (e.g. social and psychological) influences, has been difficult due to the incomplete development of a theory of culture that leads to the reliable and valid measurement of cultural factors in such a way that these can be incorporated into multivariate models. In this paper we present both such a theory and such a methodology, and apply it to the study of the community distribution of psychological distress in an urban area in Brazil. In this theory and method, culture is conceptualized as consisting of shared cultural models that are imperfectly realized in mundane behaviors. The link of cultural model and individual behavior is referred to as "cultural consonance". Here we show that cultural consonance in two different domains is associated with psychological stress, independently from covariates and possible confounding variables. Implications of the results for future research are also discussed.A análise da influência de fatores culturais no estresse psicológico (além dos sociais e psicológicos) tem sido dificultada em função do desenvolvimento incompleto de teorias culturais que resultem em medidas fidedignas e válidas de fatores culturais que possam ser incorporados a modelos multivariados. Neste artigo apresenta-se tanto tal teoria quanto uma metodologia e elas são aplicadas ao estudo da distribuição na comunidade das aflições psicológicas em uma área urbana do Brasil. Nesta teoria e metodologia, cultura é conceituada como modelos culturais compartilhados que são realizados de maneira imperfeita nos comportamentos cotidianos. A ligação do modelo cultural com o comportamento individual é colocada como "consonância cultural". Mostra-se que a consonância cultural em dois domínios diferentes está associada ao estresse psicológico independentemente de covariáveis e de outras variáveis intervenientes. São discutidas também as implicações destes resultados para pesquisas futuras