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)

Potencial de sistemas desecantes basado en el clima y en el tipo de edificio

gestión de las cargas térmicas o a la posibilidad de incorporar fuentes de energías renovables o calor residual. Sin embargo, diversas fuentes apuntan la necesidad de dedicar esfuerzos en I+D para el desarrollo de estos sistemas. En la bibliografía se encuentran diversos estudios sobre el impacto de las condiciones climatológicas en el funcionamiento de este tipo de sistemas. Además son diversos los estudios que enmarcan el análisis de estos sistemas en climas cálidos y húmedos. Por otro lado, también se pueden encontrar diversos artículos que estudian las distintas configuraciones posibles o el efecto de la variación de distintos parámetros de control sobre el rendimiento de la instalación. Sin embargo, son escasos los estudios comparativos sobre el comportamiento de los sistemas desecantes cuando se centra la atención en la interacción con el uso y tipología del edificio que se pretende climatizar. En el presente trabajo se estudia el funcionamiento de un sistema de climatización híbrido que incorpora una rueda desecante para el tratamiento de la carga latente. Se simulará el comportamiento del sistema unido a distintas tipologías de edificio en los que el nivel de carga latente es elevado. Además, se han introducido las condiciones climáticas de distintas localizaciones españolas con el fin de cubrir las distintas zonas climáticas referenciadas en el CTE DB HE1.Este trabajo se enmarca dentro del proyecto de plan nacional “Estudio para la mejora de instalaciones de energía solar térmica y enfriamiento evaporativo en edificios y centrales termosolares” (ENE2013- 48696-C2-1-R.

Medida del arrastre en torres de refrigeración

El interés por desarrollar una técnica de medida del arrastre en equipos de enfriamiento evaporativo radica en la necesidad de determinar la emisión de aerosoles en las torres de refrigeración, y predecir sus posibles efectos medioambientales. La técnica del papel hidrosensible se utiliza para registrar las gotas arrastradas que atraviesan una superficie, durante un tiempo de muestreo. El análisis de la imagen con el software Image-Pro Plus proporciona el tamaño y distribución de las gotas que constituyen el arrastre, y permite cuantificar el gasto másico del mismo.Los autores desean mostrar su agradecimiento a la Consejería de Ciencia, Tecnología, Industria y Comercio de la Región de Murcia, por la financiación del proyecto “Evaluación de la sustitución de torres de refrigeración por techos hídrico-solares. Aspectos energéticos y de emisión de aerosoles”. El trabajo descrito en este artículo es una parte de dicho proyecto

Evaluación de riesgo por legionelosis de los aerorefrigeradores con preenfriamiento adiabático. Póster

Numerosas investigaciones epidemiológicas han demostrado que las torres de refrigeración y los condensadores evaporativos son fuentes de infección por Legionella. La alternativa comercial convencional para la sustitución de las torres de refrigeración son los condesadores por aire. Si desde un enfoque sanitario los condensadores por aire cobran una clara ventaja por no ser instalaciones de riesgo, desde un punto de vista energético su consumo es mayor. Además de las soluciones clásicas de condensación como son las torres de refrigeración, los condensadores evaporativos y los aerocondensadores, comercialmente están apareciendo dispositivos híbridos que buscan un compromiso entre su impacto ambiental y el consumo energético

About using the minimum energy dissipation to find the steady-state flow distribution in networks

[EN] The incorrect analysis of the flow distribution through HVACduct-networks has an economical and environmental impact.The existence ofnegativehead loss coefficients at branched junc-tions poses a difficulty. However the dissipated energy is inher-ently positive and simplifies the solution. The paper exploresthe use of a variational method based on the minimization of thedissipated mechanical energy to find the actual steady-state flowdistribution through a network. To our knowledge, Robert Nivenwas the first to propose/explore this idea but unfortunately dis-carded the method. The paper begins with a short explanation,afterwards extends previous outcomes [1] and ends with an ex-ampleSoto Francés, VM.; Pinazo Ojer, JM.; Sarabia Escrivà, EJ.; Martínez-Beltrán, P. (2019). About using the minimum energy dissipation to find the steady-state flow distribution in networks. Taylor Francis. 1-6. http://hdl.handle.net/10251/1905161

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

Numerical study of the behavior of an air pre-cooler

Introducing an air pre-cooler step before an air cooler system have been proved to improve the global efficiency of a cooling setup. Several authors have studied the mass and the heat exchanges of an air stream and the water sprayed inside an adiabatic cooling pad. However, these previous studies present their results and correlations as functions of experimental dependent parameters. Therefore, the aim of this study is to develop a numerical modeling capable of characterizing the behavior of an air pre-cooling stage without the need of previous experimental tests, allowing an accurate initial study when designing an air cooler installation. Several numerical models and simulation tests have been developed by our researching group in order to get a proper approximation of the problem, and the employment of previous experimental data allowed the model validation in terms of pressure drop and air cooling efficiency. As a result, a numerical model is defined, validated, and compared with existing empirical correlations models as a first step to determine the best possible cooling pad configuration in every air cooling setup as a function of the pad geometry, air and water flow rates, with an only numerical simulation.The authors acknowledge the financial support received from the Spanish Government, through Projects ENE2013-48696-C2-1-R and C2-2-R as well as by the FEDER (FondoEuropeo de Desarrollo Regional

The dry and adiabatic fluid cooler as an alternative to cooling towers: an experimental view.

Energy and environmental implications of a refrigeration cycle are largely conditioned by the choice of condensing system. Conventional solutions transfer heat to water, and recirculated through cooling towers or to atmospheric air through a dry condenser. While the use of cooling towers means less energy consumption due to lower pressure in the condenser, a number of environmental implications are questioning their installation. Mainly, it represents an emission of chemicals or microorganisms to the atmosphere as Legionella. The dry and adiabatic fluid cooler works as a standard fluid dry cooler enhancing the dry cooler’s capacity with adiabatic pre-cooling of the air intake. The ambient dry bulb temperature is reduced as the air passes through an evaporative pad especially designed to humidify and cool the air (Figure.1). The main objective of this study is to experimentally investigate the thermal performance of a dry and adiabatic fluid cooler. With the experimental data, a thermal model will be developed in order to compare the energy implications arising from the replacement of traditional systems (dry condenser and cooling towers) by condensing air coolers with adiabatic pre-cooling.The construction of the prototype has been sponsored by the Regional Government of the Comunidad Valenciana, through the Project GV/2011/072. The instrumentation used to conduct experimental work has been funded through the Project “Estudio energético de un sistema alternativo para la condensación en ciclos de refrigeración: el aero-refrigerador con preenfriamiento adiabático” from Convocatoria 2009 de Proyectos Bancaja-UMH para grupos precompetitivo

Experimental study on the performance of a mechanical cooling tower fitted with different types of water distribution systems and drift eliminators.

Cooling towers are evaporative heat transfer devices in which atmospheric air cools warm water, with direct contact between the water and the air by evaporating part of the water. The principle of operation of cooling towers requires spraying or distributing water over a heat transfer surface (packing) across or through which a stream of air is passing. As a result, water droplets are incorporated in the air stream and,depending on the velocity of the air, will be taken away from the unit. This is known as drift. Although cooling tower drift is objectionable for several reasons, the most hazardous problem concerning human health is the emission of chemicals or microorganisms into the atmosphere. Undoubtedly, regarding microorganisms, the most well-known pathogens are the multiple species of bacteria collectively known as legionella. The binomial water distribution system-drift eliminator is identified to be that mainly responsible for cooling tower drift. While water distribution systems affect the mechanics of setting up the drops, drift eliminators work by changing the direction of the airflow and separating droplets from the airstream through inertial impact. The drift eliminator’s performance can be quantified mainly by two factors: droplet collection efficiency and the pressure drop across the eliminator. In contrast, water distribution systems are characterized by the pressure drop across itself and the achieved size of the particle spread. Alongside drift, the binomial water distribution system-drift eliminator affects the cooling tower performance. From the reviewed bibliography, some studies assessing the effect of the drift eliminator on cooling tower performance have been found. Nevertheless, no studies regarding the influence of the water distribution system on the cooling tower’s performance have been detected. In this sense, this paper studies the thermal performance of a forced draft counter-flow wet cooling tower fitted with two water distribution systems (the pressure water distribution system (PWDS) and gravity water distribution system (GWDS)) for six drift eliminators for a wide range of air and water mass flow rates. The data registered in the experimental set-up were employed to obtain correlations of the tower characteristic, which defines the cooling tower’s thermal performance. The outlet water temperature predicted by these correlations was compared with the experimentally registered values, obtaining a maximum averaged difference of ±0.95%.The authors wish to acknowledge the collaboration of the Ministerio de Educación y Ciencia (Spanish Education and Science Ministry) for their support of project PN I+D+I 2008-2011 ENE2010-21679-C02- 02

Anurans, the Group of Terrestrial Vertebrates Most Vulnerable to Climate Change: A Case Study with Acoustic Monitoring in the Iberian Peninsula

We report preliminary analyses from an ongoing sound monitoring project that involves five species of anurans: two species of tree frogs in the genus Hyla (Hylidae) and three species of midwife toads in the genus Alytes (Discoglossidae) in the Iberian Peninsula. Each station was monitored with an automated recording system based on solid state recorders, coupled with programmable temperature and relative humidity probes. We present comparative data of vocal activity of two populations of Alytes cisternasii from thermal extremes of the species range using human detection and commercial automated sound recognition software. Parameters such as duration of reproductive season, preferred temperatures for calling activity and relation with relative humidity are discussed. We compare the performance of analysing the recordings between an automated system of detecting the presence of Alytes cisternasii calls and listening of the recordings by non-expert personnel.Ministerio de Educación y Ciencia de España. Proyecto "Tempura