Mycotic Aortic Aneurysms

Various studies have evaluated the possibilities of surgical repair of mycotic aortic aneurysms (MAAs). Open surgical repair has usually been accepted as the gold standard treatment of MAAs. The main concern is that it carries a significant mortality risk, varying from 20 to 40% in different studies, and a 5-year survival rate of 30–50%. The largest study of open surgical treatment of mycotic aortic aneurysms (MAA) was published in 2018, and consisted of 187 patients of whom open repairs were performed in 107 patients (57%). Most of the endovascular series conclude that endovascular treatment of MAA is feasible and an acceptable alternative treatment to open repair. Although endovascular repair might be a durable option for some patients, late infection-associated complications frequently occur and are often lethal. An overall analysis of this rare pathology, its different diagnostic modalities, treatment options, and prognosis are presented and discussed in this chapter

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)

Analysis of the air-water droplet motion through cooling tower drift eliminators, including comparative efficiency evaluations of several types of devices, by numerical investigation

Mist eliminators (also called droplet eliminators, droplet separators or demisters) are devices that can remove liquid droplets from a gas flow. The gas flow laden with droplets is forced to pass through different channels, changing direction in a repetitive manner. Wave-plate (or vane type) eliminator are widely employed in chemical and industrial processes involving gas and vapour flows where mist removal is necessary for several reasons. For instance, one of the most important objectives is to restrict pollutant emission into the environment, as in cooling towers applications. Wave-plate mist eliminators can operate in vertical and horizontal situations, but in both cases, the removal of liquid droplets occurs mainly by inertial impaction. In cooling towers, spraying water is distributed over a heat transfer surface across or through which a stream of air is passing. Thus, water droplets can be captured by the stream of air and they will be carried out of the system. This phenomenon is known as drift. In countries with warm climate, inside the cooling towers the conditions of high temperature and humidity can strongly induce the spreading of pathogens agents, especially the Legionella pneumophila. The main disadvantage of installing mist (i.e., drift) eliminators is an increased pressure loss of the airflow. High-pressure loss contributes to lower flow rate of air or higher engine power of the ventilators. This fact leads to obtain lower overall efficiency values for the air-conditioning systems. Since a lack of systematic studies on comparative evaluation of morphologically similar separators has been detected, the behaviour of four wave-type eliminators having a similar geometry is studied. Both droplet collection efficiency and the pressure drop coefficient are calculated. Special emphasis is made on the validation of the numerical model with results taken from the literature, the study of the effects of relevant parameters, and the achievement of a procedure to evaluate the overall efficiency of each regarded type of eliminator. The obtained results may contribute to improve the passive droplets restraint systems in mechanical cooling towers, increasing the overall operation of the cooling tower on one side, and lowering their environmental impact on the other

Energy optimization of air conditioning system using hydrosolar roof as heat sink

An environmentally friendly alternative device, called Hydrosolar Roof, designed for heat dissipation in buildings has been necessary to include all the elements in a global model. Then, three main subsystems have been considered: Cooling Machine, Hydraulic Network and Hydrosolar Roof. A description of the three subsystem is done and the mathematical model is presented.The Cooling machine thermodynamic model has been carried out using EES (Engineering Equation Solver). The Hydraulic network model has piping, pump and nozzle information. The Hydrosolar Roof direct contact heat and mass transfer simulation has been development with a CFD code. Special attention has been paid on the cooling efficiency. The global model has been applied to a real prototype facility experimentally tested. All the energy consumptions have been calculated for different pumping heads. A global coefficient of performance (COP) has been defined and the optimum value obtained.The authors wish to acknowledge the collaboration in the calculations of A. Navarro, as well as José María Galán, Energy, Comfort and Enviroment S.L. Manager, as the proporser of the original idea

Prediction of the lifetime of droplets emitted from mechanical cooling towers by numerical investigation

A numerical modelling capable to simulate the drift and the evaporation of water droplets emitted by a mechanical cooling tower in an urban area is presented. The model is based on a real mechanical draft cooling tower situated in the surroundings of the Miguel Hernández University (Elche, Spain). An experimental study of the deposition of droplets from the cooling tower is done in order to validate the numerical modelling. This study is performed by means of the water sensitive papers technique. A biharmonic interpolation is used for obtaining the total deposition on the floor. A total of 14 cases, everyone with different atmospheric conditions, have been simulated and experimentally validated. An analytical model for the droplets lifetime prediction is validated with the results obtained from the numerical modelling. The present study shows the influence of the atmospheric and droplets conditions in the droplets lifetime, providing useful information to analyse the spread of contaminants or bacteria inside the droplets released from the cooling tower.This research is sponsored by the Spanish Government, through the Projects No. ENE2013-48696-C2-2-R and ENE2013-48696-C2-1-R, including FEDER (European Union

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

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

Modelización numérica del proceso de transferencia de calor, del flujo convectivo inducido y de la potencia generada en una central eólico solar. Póster

La chimenea eólico solar tiene por objeto producir energía eléctrica a partir de la energía del sol. La radiación solar incide sobre el colector que, a modo de invernadero, calienta el aire que hay en su interior. El aire caliente asciende por flotación a través de la chimenea, accionando y haciendo girar mediante este movimiento ascendente la turbina que se encuentra en la base de la chimenea. Esta turbina se conecta a un generador eléctrico que produce la corriente. El sistema está formado por un colector con forma cónica de radio de base 122 m, y altura en el centro y los extremos 6 y 2 m respectivamente, una chimenea en el centro del colector de 194,6 m de altura y 5 m de radio, y una turbina de 4 álabes y 5 m de radio girando a 100 rpm. En este trabajo se ha desarrollado un modelo numérico de los flujos convectivos inducidos por flotación dentro de la chimenea solar

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

On the influence of psychrometric ambient conditions on cooling tower drift deposition

Water drift emitted from cooling towers is objectionable for several reasons, mainly due to human health reasons. A numerical model to study the influence of sychrometric ambient conditions on cooling tower drift deposition was developed. The mathematical model presented, consisting of two coupled sets of conservation equations for the continuous and discrete phases, was incorporated in the general purpose CFD code Fluent. Both experimental plume performance and drift deposition were employed to validate the numerical results. This study shows the influence of variables like ambient dry bulb temperature, ambient absolute humidity and droplet exit temperature from cooling tower on the drift evaporation (and therefore deposition) and on the zone affected by the cooling tower. The stronger effect detected corresponds to the ambient dry bulb temperature. When a higher ambient temperature was present, deposition was lower (evaporation was therefore higher) and the zone affected by the cooling tower was smaller. The influence of the other two variables included in the study was weaker than the one corresponding to the dry bulb ambient temperature. A high level of ambient absolute humidity increased drift deposition and also the size of the zone affected by the cooling tower. Finally, a high level of droplet exit temperature decreased deposition and increased the zone affected by the cooling tower