Dimensional analysis and experimental study of pressure drop and heat transfer for Na-Cl ice slurry in pipes

Over the last few years, many works have been developed to study the influence of some factors like the mass flow, pipe diameter or ice contents on the pressure drop characteristics and heat transfer process when using ice slurry as liquid secondary refrigerant. Nevertheless, most of these works present results of great scientific interest, but hardly applicable to different situations to those of test conditions and therefore they have a limited interest when approaching the design of practical ice slurry installations. Based on the dimensional analysis, the work reported in this paper try to determine which are the variables that explain the thermal and hydraulic behaviour of ice slurry, to fix the influence of these variables and to present the results so that they can be used as a tool of design for ice slurry applications. Experimental studies were performed to clarify the thermal and hydraulic characteristics of ice slurry with a 3% sodium chloride-water solution flowing in circular pipes. A number of experiments have been carried out to investigate the characteristics of flowing ice slurry for various pipes diameter, ice mass fraction, flow velocity and ice crystal size, and the non-dimensional values have been obtained from the pressure drop (via Fanning factor) and the heat transfer (via Nusselt number). Experimental data on friction factor are plotted on a Moody diagram. Experimental values of Nusselt number are plotted also versus Reynolds number and others parameters. Both data collection has been compared with other researcher’s results, showing the most cases a good level of agreement

El Museo de Informática como dinamizador de la asignatura Estructura de Computadores

En este trabajo mostramos cómo el Museo de Informática de la Universitat Politècnica de València (UPV) se puede convertir en un instrumento didáctico adicional tanto para motivar a nuestros alumnos en el estudio de la asignatura Estructura de Computadores como para cumplir con la importante misión de difundir la cultura e historia de la informática entre los estudiantes de grado de ingeniería informática. La experiencia se ha llevado a cabo al inicio del curso 2013/14 con los alumnos de segundo año del mencionado grado en el ámbito de las tareas académicas de la asignatura. El artículo explica los detalles de la articulación de la visita para una asignatura de más de 400 alumnos organizados en 7 grupos de aula. La visita se ha llevado a cabo tanto dirigida directamente por el profesorado como de forma auto-guiada mediante un cuestionario. Por último, este trabajo muestra la manera en que se ha evaluado la experiencia y las conclusiones extraídas de la misma a fin de poder planificarla en los próximos cursos.SUMMARY -- This paper shows how the Museo de Informática of the Universitat Politècnica de València (UPV) can be useful to motivate our students in the study of the subject of Computer Organization and, in general, for spreading the culture and history of Computers among the students of the Computer Engineering Degree. The experiment has been carried out during the academic year 2013/14 as a new activity of the above mentioned subject. This work explains how we organized this visit for more than 400 students corresponding to 7 different class groups. The visit has been carried out either directly by teachers or selfguided in an interactive way. Finally, we show how we have evaluated the experience, the lessons learned from it and also the plan for future years

Improving scope sensitivity in contingent valuation: joint and separate evaluation of health states

We present data of a contingent valuation survey, testing the effect of evaluation mode on the monetary valuation of preventing road accidents. Half of the interviewees was asked to state their willingness to pay (WTP) to reduce the risk of having only 1 type of injury (separate evaluation, SE), and the other half of the sample was asked to state their WTP for 4 types of injuries evaluated simultaneously (joint evaluation, JE). In the SE group, we observed lack of sensitivity to scope while in the JE group WTP increased with the severity of the injury prevented. However, WTP values in this group were subject to context effects. Our results suggest that the traditional explanation of the disparity between SE and JE, namely, the so-called “evaluability,” does not apply here. The paper presents new explanations based on the role of preference imprecision

Efficient and scalable starvation prevention mechanism for token coherence

[EN] Token Coherence is a cache coherence protocol that simultaneously captures the best attributes of the traditional approximations to coherence: direct communication between processors (like snooping-based protocols) and no reliance on bus-like interconnects (like directory-based protocols). This is possible thanks to a class of unordered requests that usually succeed in resolving the cache misses. The problem of the unordered requests is that they can cause protocol races, which prevent some misses from being resolved. To eliminate races and ensure the completion of the unresolved misses, Token Coherence uses a starvation prevention mechanism named persistent requests. This mechanism is extremely inefficient and, besides, it endangers the scalability of Token Coherence since it requires storage structures (at each node) whose size grows proportionally to the system size. While multiprocessors continue including an increasingly number of nodes, both the performance and scalability of cache coherence protocols will continue to be key aspects. In this work, we propose an alternative starvation prevention mechanism, named priority requests, that outperforms the persistent request one. This mechanism is able to reduce the application runtime more than 20 percent (on average) in a 64-processor system. Furthermore, thanks to the flexibility shown by priority requests, it is possible to drastically minimize its storage requirements, thereby improving the whole scalability of Token Coherence. Although this is achieved at the expense of a slight performance degradation, priority requests still outperform persistent requests significantly.This work was partially supported by the Spanish MEC and MICINN, as well as European Commission FEDER funds, under Grants CSD2006-00046 and TIN2009-14475-C04-01. Antonio Robles is taking a sabbatical granted by the Universidad Politecnica de Valencia for updating his teaching and research activities.Cuesta Sáez, BA.; Robles Martínez, A.; Duato Marín, JF. (2011). Efficient and scalable starvation prevention mechanism for token coherence. IEEE Transactions on Parallel and Distributed Systems. 22(10):1610-1623. doi:10.1109/TPDS.2011.30S16101623221

Water drop size numerical optimization for hydrosolar roof

Air-conditioning systems of buildings and other industrial facilities commonly use water as a heat drain to remove heat from refrigerant condensers. Classical solutions to reduce the temperature of this service water are air cooled heat exchangers or mechanical draught cooling towers. The Hydrosolar Roof optimized in this paper, working as a heat focus in the thermodynamic cycle of a heat pump, achieves the same objectives without fan energy consump tion. This system consists of an extended framework on the roof of the building with some thermal plates installed over it. Some of the plates are made of a high reflective material, and the others are made of absorbent material. The Hydrosolar Roof uses the design of the reflective and absorbent parts of the device, made of flat plates, to form a sloping channel. Solar radiation is collected by this channel and, due to local heating in this zone, natural convection through it is produced. The natural induced air flow is irrigated with water sprays, placed below the plates at the inlet of the channel, generating a cross flow between air and water. In this way, water is cooled by direct contact with a reduced amount of vaporization, and most of the water is recovered at a reduced temperature. This work shows the numerical study to obtain an optimum for the sprayed water drop size. The two-dimensional version of the CFD code Fluent was applied to predict both atmospheric air and sprayed water main variables in a real geometry and under different thermodynamic conditions.The authors wish to acknowledge the collaboration in the calculations of A. Navarro, as well as José María Galán, Energy, Comfort and Environment S.L. manager, as proposer of the original idea

Water mass flow optimization for hydrosolar roof

Cooling towers are classical solutions to remove heat from air-conditioning systems and other industrial facilities. This process is possible due to the energy and mass transfer between flowing air and water. The hydrosolar roof optimised in this paper is able to obtain the same effect substituting the fan of the mechanical draught cooling towers for air flow induced by solar radiation and wind. In a previous work, the drop size of the sprayed water and the pumping pressure necessary to obtain it was studied and the optimal operation point was found to a fixed water mass flow. This work describes the design point optimization procedure taking into account the water mass flow as an essential variable to evaporative systems. In particular, air and water mass flow ratio is one of the most important variable to study the cooling capacity in a cooling tower. Therefore, hydrosolar roof results will be showed as cooling tower results are usually showed. The necessary correlations to performance the optimization procedure were obtained by a hydrosolar roof numerical modelization. The numerical simulation takes into account both evaporative and convective effects and two-dimensional version of the CFD code Fluent was used. In this way, weather variables as solar radiation, wind velocity, dry bulb temperature and wet bulb temperature have been taking into account. Numerical results have been validated with the experimental results obtained previously in a hydrosolar roof prototype.The authors wish to acknowledge the collaboration in the calculations of A. Navarro, as well as José María Galán, Energy, Comfort and Environment S.L. manager, as proposer of the original idea

e-WASTE: Everything an ICT Scientist and Developer Should Know

[EN] Every dazzling announcement of a new smart phone or trendy digital device is the prelude to more tons of electronic waste (e-waste) being produced. This e-waste, or electronic scrap, is often improperly added to common garbage, rather than being separated into suitable containers that facilitate the recovery of toxic materials and valuable metals. We are beginning to become aware of the problems that e-waste can generate to our health and the environment. However, most of us are still not motivated enough to take an active part in reversing the situation. The aim of this article is to contribute to increase this motivation by pointing out the significant problem that e-waste represents and its social and environmental implications. We have chosen this forum in which multidisciplinary researchers in ICT from all countries access on regularly to explain the serious problems we are exposed to when we do not make a responsible and correct use of technology. In this paper, we also survey the composition of contemporary electronic devices and the possibilities and difficulties of recycling the elements they contain. As researchers, our contributions in science enable us to find solutions to current problems and to design more and more powerful intelligent devices. But responsible researchers must be aware of the negative effects that this industry causes us and, consequently, assume their commitment with more sustainable designs and developments. Therefore, the knowledge of e-waste issues is crucial also in the scientific world. Researchers should consider this problem and contribute to minimize it or find new solutions to manage it. These must be the additional challenges in our projects.This work was supported in part by the Spanish Ministry of Economy and Competitiveness under Grant TIN2013-43913-R.Pont Sanjuan, A.; Robles Martínez, A.; Gil, JA. (2019). e-WASTE: Everything an ICT Scientist and Developer Should Know. IEEE Access. 7:169614-169635. https://doi.org/10.1109/ACCESS.2019.2955008S169614169635

The solar roof of Enercom, as an integrated energy solution for thermal conditioning of buildings

Actually and in the near future, due to the necessity of refrigeration, the need of thermal energy dissipation systems will be increased. One of the best element, is the cooling tower, but it has one mean inconvenient, what is the use of a fan. The use of the fan has the following misfortunes: waste of energy, noise, vibration and dissemination of Legionella, if it is present. To overcome these misfortunes, we present a energetic solution, highly efficiently, The Solar Roof of Enercom, because the draught of the air, is by natural driving, this element has the following advantages: No electric energy wasted, no noise, no vibration and dramatic reduction of Legionella dissemination in the air. Integrated in an air conditioning system, the solar roof works in different ways according to the needs of the conditioned building, in summer as a heat sink and in winter as a source of heat.The authors wish to have the acknowledge to the DG XII (Research) of the European Commission for his economical support, under the Cooperative Research project entitle IMPROVEMENT OF ENERGY POWER OF SOLAR ROOF BY VENTILATION WITH A LINEAR STATIC EXHAUSTER

Experimental determination of drift loss from a cooling tower with different drift eliminators using the chemical balance method

The existence of cooling towers arises from the need to evacuate power to the environment from engines, refrigeration equipment and industrial processes. Water drift emitted from cooling towers is objectionable for several reasons, mainly due to human health hazards. It is common practice to fit drift eliminators to cooling towers in order to minimise water loss from the system. The presence of the drift eliminator mainly affects two aspects of cooling towers: their thermal performance and the amount of water drift loss. This paper experimentally studies the drift loss emissions from a cooling tower without drift eliminator and fitted with six different drift eliminators. Chemical Balance is the selected method and Australian Standard methodology is taken as a reference. Some modifications are proposed to reduce uncertainty by increasing the duration of the test and the number of water samples. Installation of a drift eliminator, even in the worst case, reduces the water drift level to less than half of the situation without the eliminator. The water drift losses obtained with the different drift eliminators installed at the pilot plant, from 0.0118% to 0.161%, are within the range generally reflected in the literature. Finally, a criterion for designing drift eliminators in order to optimise both the collection efficiency and the cooling tower's thermal performance is proposed.This research has been partially financed by the project DPI2007-66551-C02-01 grant from the “Dirección General de Industria, M. de Ciencia y Tecnología”, the project 2I05SU0029 grant of the “Secretaría General de la Consejerí de Educación y Cultura de la C.A. de la Región de Murcia” and the HRS Spiratube Company, Murcia (Spain)

Effect of the axial scraping velocity on enhanced heat exchangers

The flow pattern within an enhanced tubular heat exchanger equipped with a reciprocating scraping device is experimentally analysed. The insert device, specially designed to avoid fouling and to enhance heat transfer, has also been used to produce ice slurry. It consists of several circular perforated scraping discs mounted on a coaxial shaft. The whole is moved alternatively along the axial direction by a hydraulic cylinder. The phase-averaged velocity fields of the turbulent flow have been obtained with PIV technique for both scraping semi-cycles. Special attention has been paid to the effect of the non-dimensional scraping velocity and the Reynolds number in the flow field. CFD simulations provide support for the identification of the flow patterns and the parameter assessment extension. The results show how the scraping parameters affect the turbulence level produced in the flow and therefore the desired heat transfer enhancement