Design of Plate-Fin Tube Dehumidifiers for Humidification-Dehumidification Desalination Systems

A two-dimensional numerical model of a plate-fin tube heat exchanger for use as a dehumidifier in a humidification-dehumidification (HDH) desalination systems is developed, because typical heating, ventilating, and air conditioning (HVAC) dehumidifier models and plate-fin tube dehumidifier geometries are not intended for the considerably higher temperature and humidity ratio differences which drive heat and mass transfer in HDH desalination applications. The experimentally validated model is used to investigate the influence of various heat exchanger design parameters. Potential improvements on common plate-fin tube dehumidifier designs are identified by examining various methods of optimizing tube diameter, and longitudinal and transverse tube spacing to achieve maximum heat flow for a given quantity of fin material at a typical HDH operating point. Thicker fins are recommended than for HVAC geometries, as the thermal conductive resistance of HVAC fins restricts dehumidifier performance under HDH operating conditions.Elisabeth Meurer FoundationKarl H. Ditze FoundationGerman Academic Exchange ServiceCenter for Clean Water and Clean Energy at MIT and KFUP

Design of Flat-Plate Dehumidifiers for Humidification–Dehumidification Desalination Systems

Flat-plate heat exchangers are examined for use as dehumidifiers in humidification–dehumidification (HDH) desalination systems. The temperature and humidity ratio differences that drive mass transfer are considerably higher than in air-conditioning systems, making current air-conditioning dehumidifier designs and design software ill-suited to HDH desalination applications. In this work a numerical dehumidifier model is developed and validated against experimental data. The model uses a logarithmic mass transfer driving force and an accurate Lewis number. The heat exchanger is subdivided into many cells for high accuracy. The Ackermann correction takes into account the effect of noncondensable gases on heat transfer during condensation. The influence of various heat exchanger design parameters is thoroughly investigated and suitable geometries are identified. Among others, the relationship between heat flow, pressure drop, and heat transfer area is shown. The thermal resistance of the condensate layer is negligible for the investigated geometries and operating point. A particle-embedded polymer as a flat-plate heat exchanger material for seawater operation substantially improves the heat flux relative to pure polymers and approaches the performance of titanium alloys. Thus, the use of particle-embedded polymers is recommended. The dehumidifier model can be applied in design and optimization of HDH desalination systems.Center for Clean Water and Clean Energy at MIT and KFUP

El pensamiento humano y sus materializaciones

El presente artículo intenta una mirada distante de aquellas tradiciones que estudian la oralidad y de las sociedades que no conocen la escritura privilegiando la producción-recepción de discursos verbales. El punto de partida es que ese tipo de sociedades disponen, si nos referimos a su tecnología comunicativa, no de uno, sino de dos sistemas de comunicación verbal: el oral (o vocal) y el gestual. El sistema gestual, como el moderno lenguaje gestual destinado a los sordos, traduce, como la escritura, un discurso verbal; es por lo tanto —igual que los subtítulos en el cine—, una especie de escritura efímera. El uso de uno o de otro de los dos sistemas depende del contexto: la escritura gestual se usa en público y la oralidad vocal en la esfera íntima. En términos de la durabilidad de los dos sistemas, se sitúa la mirada hermenéutico-exegética en la dimensión κίνημα (cine, movimiento), recorriendo y recurriendo a poemas orales, mitos y mitografías, pinturas primordiales y lienzos precolombinos, además del diálogo con especialistas en la materia

O cinema e as lutas populares: Eizenštein, Strand, Glauber Rocha, Hirszman, Coutinho

A luta de classes, como afirmou Marx depois de vários outros, é o motor da história. No capitalismo, sempre segundo o autor do Capital, essa luta se desenvolve básicamente entre os donos dos meios de produção e os trabalhadores desprovistos deles. A luta de classes é uma temática importante no cinema europeo, especialmente entre a época das vanguardas (em particular soviéticas) e a do neo-realismo. Na América hispánica e no Brasil, com excepções como a ficção quasi neo-realista mexicana Redesde Paul Strand, Fred Zinnemann e outros (1933-1936), o cinema demora um certo tempo para começar a focalizar momentos importantes da luta de classes, mas o faz a partir de concepções teóricas e estéticas mais "novas", inspiradas, direta ou indiretamente, na nouvelle vague francesa. Este breve ensaio, partindo de um filme agit-prop como Ста́чка(Statchka, 'A greve', 1925) do cineasta soviético S. M. Eizenštein, passa em revista alguns filmes brasileiros do meio século 1960-2010 que trabalham episódios da luta de classes de maneira propriamente inédita ou "extraordinária". Um exemplo maior desse cinema de vanguarda Cabra marcado para morrerde Eduardo Coutinho (1962-1984).La lucha de clases, como afirmó Marx después de varios otros, es el motor de la historia. En el capitalismo, siempre según el autor de El Capital, esta lucha se desarrolla básicamente entre los dueños de los medios de producción y los trabajadores privados de ellos. La lucha de clases es un tema importante en el cine europeo, especialmente entre la época de las vanguardias (en particular las soviéticas) y la del neorrealismo. En Hispanoamérica y Brasil, con excepciones como la ficción mexicana casi neorrealista Redes de Paul Strand, Fred Zinnemann y otros (1933-1936), el cine tarda un poco en empezar a centrarse en momentos importantes de la lucha de clases, pero lo hace a partir de concepciones teóricas y estéticas "más nuevas", inspiradas, directa o indirectamente, por la nouvelle vague francesa. Este breve ensayo, basado en una película agitprop como Ста́чка (Statchka, 'La huelga', 1925) del cineasta soviético S. M. Eizenštein, repasa algunas películas brasileñas de mediados de siglo, entre 1960 y 2010, que trabajan episodios de lucha de clases de manera propiamente inédita o "extraordinaria". Un ejemplo mayor de este cine de vanguardia es Cabra marcado para morrer(Cabra, marcado para morir) de Eduardo Coutinho (1962-1984).La lluita de classes, com va afirmar Marx després de diversos altres, és el motor de la història. En el capitalisme, sempre segons l'autor El Capital, aquesta lluita es desenvolupa bàsicament entre els amos dels mitjans de producció i els treballadors privats. La lluita de classes és un tema important al cinema europeu, especialment entre l'època de les avantguardes (en particular les soviètiques) i la del neorrealisme. A Hispanoamèrica i Brasil, amb excepcions com la ficció mexicana gairebé neorealista Redes de Paul Strand, Fred Zinnemann i altres (1933-1936), el cinema triga una mica a començar a centrar-se en moments importants de la lluita de classes, però ho fa a partir de concepcions teòriques i estètiques "més noves", inspirades, directament o indirectament, per la nouvelle vague francesa. Aquest breu assaig, basat en una pel·lícula agitprop com Ста́чка (Statchka, 'La vaga', 1925) del cineasta soviètic S. M. Eizenštein, repassa algunes pel·lícules brasileres de mitjans de segle, entre 1960 i 2010, que treballen episodis de lluita de classes de manera pròpiament inèdita o "extraordinària". Un exemple més gran d'aquest cinema d'avantguarda és Cabra marcado para a morrer (Cabra, marcat per a morir) d'Eduardo Coutinho (1962-1984).The class struggle, as Marx claimed after several others, is the engine of history. In capitalism, always according to the author of Capital, this struggle takes place basically between the owners of the means of production and the workers deprived of them. The class struggle is an important theme in European cinema, especially between the times of the avant-gardes (particularly the Soviet ones) and that of neorealism. In Latin America and Brazil, with exceptions such as the almost neorealist Mexican fiction Redes by Paul Strand, Fred Zinnemann and others (1933-1936), it takes a while for the cinema to begin to focus on important moments of the class struggle, but it does so by starting from "newer" theoretical and aesthetic conceptions, inspired, directly or indirectly, by the French nouvelle vague. This short essay, based on an agitprop film such as Ста́чка (Statchka, 'The strike', 1925) by the Soviet filmmaker S. M. Eizenštein, reviews some mid-century Brazilian films from 1960-2010 that work on episodes of class struggle in a truly unknown or "extraordinary" way. A major example of this avant-garde cinema is Cabra marcado para morrer (A Man Marked for Death) by Eduardo Coutinho (1962-1984)

Procedures and criteria for evaluating academic legal publications: Results of a survey in Switzerland

As in other European countries, there has been a growing pressure on assessing academic research in Switzerland. This also applies to the field of academic legal research. This article, which is based on a survey in Switzerland, aims to explore the assessment procedures and criteria that are used to evaluate academic legal publications and to judge their suitability. In doing so, two important principles have to be respected: first, the suitability of assessment procedures and quality criteria depends on the context and the purpose of the assessment. Additionally, peculiarities of research (and publication) behaviour in academic legal research have to be taken into account. Second, researchers of a certain field need to be involved into the process of defining how to evaluate research (bottom-up approach). On the basis of literature analysis, the actual use and suitability of assessment procedures and criteria were explored in a survey among editors of law journals, law professors, and practitioners (lawyers). Results show that academic legal publications in Switzerland are mainly being assessed by means of (simple) peer review, whereby double-blind peer review procedures are rarely used. There appears to be some common ground among stakeholders concerning appropriate criteria, but the substance of criteria remains unclear. Bibliometric methods and indicators are rarely being used and generally do not yield meaningful results

ULTRAPERMEABLE MEMBRANES FOR BATCH DESALINATION: MAXIMUM DESALINATION ENERGY EFFICIENCY, AND COST ANALYSIS

Reducing the energy consumption of membrane desalination is critical to reducing its cost of water and minimizing desalination’s CO₂ emissions. Hybrids of reverse osmosis (RO) with ul trapermeable membranes promise to address the efficiency, rejection, and fouling issues. In a batch reverse osmosis (BRO) process, salinity is varied over time so that the applied pressure better matches osmotic pressure, increasing efficiency. In this paper, the impact of ultrapermeable membranes in BRO are modelled, and a cost analysis is performed. The results show energetic advantages for the BRO over the best continuous RO configurations. Batch RO systems offer significant cost savings, and saves more energy than the use of ultrapermeable membranes in continuous RO systems. The two combined, BRO and ultrapermeable membranes, has the potential for the most efficient desalination systems yet proposed. However, low membrane cost is needed for ultrapermeable membranes to be viable