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Integrated analysis of cooling water systems: Modeling and experimental validation

CORTINOVIS, Giorgia F.; RIBEIRO, Marcelo T.; PAIVA, Jose L.; SONG, Tah W.; PINTO, Jose M.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
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Cooling towers are widely used in many industrial and utility plants as a cooling medium, whose thermal performance is of vital importance. Despite the wide interest in cooling tower design, rating and its importance in energy conservation, there are few investigations concerning the integrated analysis of cooling systems. This work presents an approach for the systemic performance analysis of a cooling water system. The approach combines experimental design with mathematical modeling. An experimental investigation was carried out to characterize the mass transfer in the packing of the cooling tower as a function of the liquid and gas flow rates, whose results were within the range of the measurement accuracy. Then, an integrated model was developed that relies on the mass and heat transfer of the cooling tower, as well as on the hydraulic and thermal interactions with a heat exchanger network. The integrated model for the cooling water system was simulated and the temperature results agree with the experimental data of the real operation of the pilot plant. A case study illustrates the interaction in the system and the need for a systemic analysis of cooling water system. The proposed mathematical and experimental analysis should be useful for performance analysis of real-world cooling water systems. (C) 2009 Elsevier Ltd. All rights reserved.; FAPESP[00/15097-0]

A systemic approach for optimal cooling tower operation

CORTINOVIS, Giorgia F.; PAVIA, Jose L.; SONG, Tah W.; PINTO, Jose M.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
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The thermal performance of a cooling tower and its cooling water system is critical for industrial plants, and small deviations from the design conditions may cause severe instability in the operation and economics of the process. External disturbances such as variation in the thermal demand of the process or oscillations in atmospheric conditions may be suppressed in multiple ways. Nevertheless, such alternatives are hardly ever implemented in the industrial operation due to the poor coordination between the utility and process sectors. The complexity of the operation increases because of the strong interaction among the process variables. In the present work, an integrated model for the minimization of the operating costs of a cooling water system is developed. The system is composed of a cooling tower as well as a network of heat exchangers. After the model is verified, several cases are studied with the objective of determining the optimal operation. It is observed that the most important operational resources to mitigate disturbances in the thermal demand of the process are, in this order: the increase in recycle water flow rate, the increase in air flow rate and finally the forced removal of a portion of the water flow rate that enters the cooling tower with the corresponding make-up flow rate. (C) 2009 Elsevier Ltd. All rights reserved.; FAPESP[00/15097-0]

Influência de variáveis de processo do desempenho de torre de resfriamento.; Influence of process variables on the cooling tower performance.

Mello, Lilian Cardoso de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 29/08/2008 PT
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Com base em um modelo fenomenológico e a partir de dados experimentais obtidos numa planta piloto, foi obtida uma correlação entre o desempenho de uma torre de resfriamento em função das principais variáveis de processo: fluxos mássicos do gás e da água pela torre, e temperatura de entrada da água. Os resultados apresentaram boa consistência, comparados com os da literatura. A metodologia desenvolvida pode, com relativa facilidade, ser aplicada para torres de resfriamento industriais, pois se baseia em medidas de variáveis, factíveis em termos práticos. Efetuou-se também um estudo paralelo com base em modelagem e simulações matemáticas do comportamento de uma torre de resfriamento de água em condições severas, com temperatura da água de alimentação superior a 50°C. Constatou-se que o coeficiente de transporte de massa na torre de resfriamento aparentemente não é afetado.; Cooling towers are widely used in many industrial and utility plants and its thermal performance is of vital importance. In the present work, using a phenomenological model and by experiments carried on over a pilot installation, the mass transfer coefficient dependence of air and water flow rates and inlet cooling water temperature is determined. The approach proposed may be useful in addition for characterization of industrial cooling towers since it depends on temperature and flow rate measurement usually available in typical plants. A parallel study concerning high mass transfer rate theory is accomplished. Through mathematical modeling and simulations based on this study no influence is detected on the mass transfer coefficient in the cooling tower...

Modelagem fenomenológica do desempenho de torres de resfriamento de água acopladas e estudo de casos.; Phenomenological modeling of performance of coupled water cooling towers and case studies.

Lima Junior, Rafael Candido de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 03/06/2011 PT
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Neste trabalho foi realizada a modelagem fenomenológica do desempenho de uma torre de resfriamento de água e de um sistema de duas torres de resfriamento em série, com temperatura de água de entrada de até 65 ºC. Verificou-se a validade do modelo através de comparação dos resultados previstos com os obtidos em ensaios em uma unidade piloto. Em seguida, através de simulação matemática, a partir do modelo desenvolvido, foi feito o estudo de diversos casos de aplicação. Estudou-se a influência das principais variáveis de operação (vazão de ar, vazão de água e temperatura de bulbo úmido) no desempenho de torres de resfriamento acopladas (em série e em paralelo) e no custo operacional. Verifica-se que a variável de maior influência é a vazão de água que circula pela torre.; This is a study about the phenomenological modeling of the performance of a water cooling tower and a system of two cooling towers in series, with water temperature input up to 65°C. The validity of model was verified by comparing the expected results with those obtained in tests on a pilot plant. After this, through a mathematical simulation, based on the model developed, several cases of application were analyzed. It was studied the influence of main operating variables (air flow...

Proposta e comparação de um modelo fenomenológico com base em alto transporte de massa e supersaturação para torre de resfriamento de água.; Presentation and comparison of a model based in high mass transfer and supersaturation in a cooling water tower.

Fernandes, Mariana
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 20/12/2011 PT
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Torres de resfriamento são equipamentos muito utilizados na indústria e que muitas vezes operam sob condições adversas, particularmente, temperatura de água acima dos 50°C na entrada da torre. Nesta condição, tem-se alta taxa de evaporação e eventualmente condição de alto transporte de massa, normalmente não considerado no equacionamento de torres de resfriamento. Apresenta-se assim uma análise comparativa de diferentes métodos de cálculo de torres de resfriamento: Merkel, Poppe e o modelo proposto. No modelo proposto neste estudo, consideram-se os balanços diferenciais de massa e energia e os mecanismos de transporte simultâneo de calor e massa, na condição de alto transporte de massa e de supersaturação do ar, caso o vapor de água condense na forma de névoa. Para os casos em que há saturação do ar, os balanços diferenciais de massa e energia passam a contemplar este fenômeno a partir do momento em que ocorre a saturação. O modelo matemático desenvolvido consiste de equações diferenciais ordinárias e equações auxiliares, e foi implementado em uma interface Matlab. Os principais parâmetros investigados foram: as vazões de água e ar, a temperatura de bulbo úmido do ar, a temperatura da água na entrada da coluna e a altura da torre. A partir das simulações matemáticas...

Avaliação de um sistema industrial de resfriamento de água.; Evaluation of an industrial system of cooling water.

Oikawa, Eduardo Hiroshi
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 19/03/2012 PT
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Neste trabalho, foi estudado o desempenho de um sistema constituído de torres de resfriamento e a sua integração em uma planta industrial de hidrogenação de butadieno. Caracterizou-se o desempenho das torres de resfriamento com base em um modelo fenomenológico, cujos parâmetros foram obtidos a partir da medição de variáveis operacionais reais. O processo de hidrogenação foi configurado em um simulador de processos, sendo o caso base estabelecido nas condições de projeto. Elaborou-se um módulo específico referente às torres de resfriamento, que foi integrado ao processo configurado no simulador. Em seguida, analisaram-se as interações das condições operacionais da torre de resfriamento no desempenho do processo industrial.; In the present work, the performance of a system composed of a cooling tower integrated in butadiene hydrogenation plant was studied. An experimental investigation was made to characterize the cooling towers based on a phenomenological model and in real process conditions. The hydrogenation process was configured on a process simulator and design specifications were considered as base case. A cooling tower module was developed and integrated to the process simulator. The interaction of the cooling tower system and the plant operation was investigated.

Montagem e avaliação de uma torre de resfriamento para uso em atividades de ensino de graduação; Assembly and evaluation of a cooling tower for use in teaching undergraduate activities

Renata Waki
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 29/10/2009 PT
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Esta dissertação descreve a montagem de um sistema de resfriamento deságua e as avaliações nele realizadas visando sua utilização para o ensino de sistemas de processos para alunos de graduação. O ensino de sistemas de processos restringe-se, normalmente, à modelagem e simulação computacional, sendo poucas as vezes que o aluno tem um contato com o processo real. Buscando contribuir para uma melhorar aprendizagem nesta área e aplicar conceitos teóricos na prática, estruturou-se o referido sistema. Este sistema foi construído em escala de planta-piloto e é formado pelos subsistemas trocador de calor e torre de resfriamento. Para medição das variáveis de processo, foi feita uma instrumentação industrial padrão nos subsistemas com sensores de temperatura, umidade, vazão e pressão diferencial. Estes instrumentos foram conectados a um módulo de aquisição e registro de variáveis (datalogger) que possui comunicação serial RS485 com protocolo MODBUS. O uso deste aparelho possibilita o envio dos parâmetros do processo a terminais de computadores para acompanhamento on-line ou para armazenamento e posteriores análises. Para melhor visualização do processo, foram feitas telas supervisórias utilizando-se para isso o software Indusoft Web Studio v6.1. Por fim...

Otimização do consumo de químicos aplicados nas torres de arrefecimento da central termoelétrica de Lares; Optimizing the consumption of chemicals applied in the cooling tower of Lares combine cycle power plant

Pimenta, João Pedro Rodrigues
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Trabalho de Conclusão de Curso
Publicado em //2014 POR
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Dissertação de mestrado integrado em Engenharia Biológica (área de especialização em Tecnologia do Ambiente); A Central Termoelétrica de Lares, da EDP Produção, no seu processo de produção de energia elétrica possui um circuito de arrefecimento, em que a água utilizada é submetida a um tratamento químico. A presente dissertação teve como objetivo o estudo e a otimização do tratamento químico aplicado nas torres de arrefecimento, tendo em consideração a função e eficiência dos produtos químicos utilizados. Um dos principais equipamentos deste sistema é a torre de arrefecimento em que a água para compensação de perdas por evaporação é captada do rio Mondego. Os produtos químicos usados no tratamento da água de arrefecimento são: anti-incrustante, biodispersante, hipoclorito de sódio e ácido clorídrico. O estudo do doseamento do anti-incrustante foi realizado através da determinação do Índice de Saturação de Langelier e de Stiff & Davis. Relativamente ao biodispersante e ao hipoclorito de sódio utilizado como desinfetante, o estudo consistiu em análises microbiológicas e determinações de cloro livre residual. Verificou-se que o valor máximo do Índice de Saturação atingido pela água de compensação foi de 0...

Role of bacterial adhesion in the microbial ecology of biofilms in cooling tower systems

Liu, Yang; Zhang, Wei; Sileika, Tadas; Warta, Richard; Cianciotto, Nicholas P.; Packman, Aaron
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
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The fate of the three heterotrophic biofilm forming bacteria, Pseudomonas aeruginosa, Klebsiella pneumoniae and Flavobacterium sp. in pilot scale cooling towers was evaluated both by observing the persistence of each species in the recirculating water and the formation of biofilms on steel coupons placed in each cooling tower water reservoir. Two different cooling tower experiments were performed: a short-term study (6 days) to observe the initial bacterial colonization of the cooling tower, and a long-term study (3 months) to observe the ecological dynamics with repeated introduction of the test strains. An additional set of batch experiments (6 days) was carried out to evaluate the adhesion of each strain to steel surfaces under similar conditions to those found in the cooling tower experiments. Substantial differences were observed in the microbial communities that developed in the batch systems and cooling towers. P. aeruginosa showed a low degree of adherence to steel surfaces both in batch and in the cooling towers, but grew much faster than K. pneumoniae and Flavobacterium in mixed-species biofilms and ultimately became the dominant organism in the closed batch systems. However, the low degree of adherence caused P. aeruginosa to be rapidly washed out of the open cooling tower systems...

Methodology for cooling water systems design = : Metodologia para projeto de sistemas de água de resfriamento; Metodologia para projeto de sistemas de água de resfriamento

Igor Maciel de Oliveira e Silva
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/08/2014 PT
Relevância na Pesquisa
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Sistemas de água de resfriamento são o método mais comum de rejeição de calor na indústria. Sistemas convencionais de água de resfriamento recirculante possuem uma rede de trocadores de calor em uma configuração paralela, demandando grande quantidade de circulação de água e torres de resfriamento. Embora a reutilização de água de resfriamento reduza a quantidade de água que é necessária no sistema e aumente o desempenho e capacidade da torre de resfriamento, a queda de pressão na rede de trocadores de calor pode aumentar devido ao seu arranjo em série-paralelo. Este estudo introduz uma metodologia para projetar diferentes sistemas de água de resfriamento e para analisar os impactos da reutilização de água sobre a queda de pressão na rede de trocadores de calor e sobre a torre de resfriamento. A partir de um modelo de super-estrutura, utiliza-se um algoritmo combinatorial com o auxílio da ferramenta de otimização Solver do Microsoft Excel para resolver um problema não-linear (NLP) de cada estrutura de rede de trocadores de calor. A queda de pressão em redes de trocadores de calor é avaliada por uma metodologia baseada na Teoria dos Grafos e utiliza os algoritmos de ordenação por topologia e de caminho crítico. Utiliza-se o método de Merkel para modelar a altura de uma torre de resfriamento e poder avaliar o volume necessário de uma torre de resfriamento para cada rede de trocadores de calor. Um estudo de caso é utilizado para ilustrar cada passo a medida que a metodologia é desenvolvida...

Computer optimization of dry and wet/dry cooling tower systems for large fossil and nuclear power plants

Choi, Michael; Glicksman, Leon R.
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 11159992 bytes; application/pdf
EN_US
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There is a projected shortage of water supply for evaporative cooling in electric power industry by the end of this century, Thus, dry and wet/dry cooling tower systems are going to be the solution for this problem. This study has determined the cost of dry cooling compared to the conventional cooling methods. Also, the savings by using wet/dry instead of all-dry cooling has been determined. A total optimization has been performed for power plants with dry cooling tower systems using metal-finned-tube heat exchangers and surface condensers. The optimization minimizes the power production cost. The program does not use pre-designed heat exchanger modules. Rather, it optimizes the heat exchanger and its air and water flow rates. In the base case study, the-method of replacing lost capacity assumes the use of gas turbines. As a result of using dry cooling towers in an 800 MWe fossil plant, the incremental costs with the use of high back pressure turbine and conventional turbine over all-wet cooling are 11% and 15%, respectively. For a 1200 MWe nuclear plant, these are 22% and 25%, respectively. Since the method of making up lost capacity depends on the situation of a utility, considerable effort has been placed on testing the effects of using different methods of replacing lost capacity at high ambient temperatures by purchased energy. The results indicate that the optimization is very sensitive to the method of making up lost capacity. It is...

Computer optimization of the MIT advanced wet/dry cooling tower concept for power plants

Choi, Michael; Glicksman, Leon R.
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 3677297 bytes; application/pdf
EN_US
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There is a projected water shortage problem in the electrical power industry by the end of this century. Dry and wet-dry cooling towers are going to be the solution of this problem. Our previous study on the combination of separate dry and wet cooling towers indicated that wet-dry cooling is an economical choice over all-dry cooling when some water is available but the supply is insufficient for an evaporative tower. An advanced wet-dry cooling tower concept was experimentally studied at MIT's Heat Transfer Laboratory and a computer model was developed for predicting the performance of this cooling concept. This study has determined the cost of the cross-flow type of this cooling concept in conjunction with steam electrical power plants. Aluminum is found to be economically preferable to galvanized steel as the cooling plate material. In our base case study using aluminum plates for a 1094 MWe nuclear plant at Middletown, the MIT advanced cooling concept is comparable to conventional wet-dry towers at water makeups larger than 45% and is slightly more economical at makeup larger than 50%. The incremental costs over the power production cost, 32.3 mills/Kwhr, of zero condenser system are 14, 13 and 12 percent for makeups of 45...

Advanced dry cooling tower concept

Curcio, John Lorenzo
Fonte: MIT Energy Lab Publicador: MIT Energy Lab
Tipo: Relatório Formato: 3687517 bytes; application/pdf
EN_US
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The purpose of this year's work has been to develop a new dry cooling tower surface. The new surface utilizes a modification of film type packing in wet cooling towers. It is a concept which may eliminate excessive water loss. Cost of fabrication, and effectiveness of heat transfer surface were among the major design considerations. Based on preliminary water wetting investigations over simple geometric surfaces, a conductive plate was shaped to form a series of V-troughs. It provided open chennelled water flow separated by fin-like dry surfaces, and simultaneously self distributed random spraying water. The design not only channels the water flow, but also provides a convenient means to vary the air-water interfacial area to the water-plate and dry plate contact area. Varying these ratios will become necessary as optimization studies are completed. To investigate the effectiveness of this design and of future advanced wet-dry concepts, a model heat transfer test apparatus was constructed. It provided operating conditions (water temperature, water flow rates and air flow rates) similar to those of existing wet cooling tower packing sections. All of the design requirements have been satisfied: hot water flow recirculation and counter flow air stream. A computer simulation of the proposed surface was made. The simulation modeled heat and mass transfer from the air-water interface as well as heat transfer from the dry surface area. Initial parametric runs were made using the program. They indicate that when the ratio of wet surface area to total surface area is five percent...

Advanced wet-dry cooling tower concept

Snyder, Troxell Kimmel; Bentley, Jeffrey; Giebler, Martin; Glicksman, Leon R.; Rohsenow, Warren M.
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 3110368 bytes; 5615307 bytes; application/pdf; application/pdf
EN_US
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The purpose of this years' work has been to test and analyze the new dry cooling tower surface previously developed. The model heat transfer test apparatus built last year has been instrumented for temperature, humidity and flow measurement and performance has been measured under a variety of operating conditions. Tower Tests showed approximately 40-50% of the total energy transfer as taking place due to evaporation. This can be compared to approximately 80 to 85% for a conventional wet cooling tower. Comparison of the model tower test results with those of a computer simulation has demonstrated the validity of that simulation and its use as a design tool. Computer predictions have been made for a full-size tower system operating at several locations. Experience with this counterflow model tower has suggested that several design problems may be avoided by blowing the cooling air horizontally through the packing section. This crossflow concept was built from the previous counterflow apparatus and included the design and fabrication of new packing plates. Instrumentation and testing of the counterflow model produced data with an average experimental error of 10%. These results were compared to the predictions of a computer model written for the crossflow configuration. In 14 test runs the predicted total heat transfer differed from the measured total heat transfer by no more than 8% with most runs coming well within 5%. With the computer analogy's validity established...

Comparative evaluation of cooling tower drift eliminator performance

Chan, Joseph Kwok-Kwong; Golay, Michael W.
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 11246576 bytes; application/pdf
EN_US
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The performance of standard industrial evaporative cooling tower drift eliminators is analyzed using experiments and numerical simulations. The experiments measure the droplet size spectra at the inlet and outlet of the eliminator with a laser light scattering technique. From these measured spectra, the collection efficiency is deduced as a function of droplet size. The numerical simulations use the computer code SOLASUR as a subroutine of the computer code DRIFT to calculate the two-dimensional laminar flow velocity field and pressure drop in a drift eliminator. The SOLASUR subroutine sets up either no-slip or freeslip boundary conditions at the rigid eliminator boundaries. This flow field is used by the main program to calculate the eliminator collection efficiency by performing trajectory calculations for droplets of a given size with a fourth-order Runge-Kutta Numerical method. The experimental results are in good agreement with the collection efficiencies calculated with no-slip boundary conditions. The pressure drop data for the eliminators is measured with an electronic manometer. There is good agreement between the measured and calculated pressure losses. The results show that both particle collection efficiency and pressure loss increase as the eliminator geometry becomes more complex...

DRIFT : a numerical simulation solution for cooling tower drift eliminator performance

Chan, Joseph Kwok-Kwong; Golay, Michael Warren
Fonte: MIT Energy Laboratory & Department of Nuclear Engineering Publicador: MIT Energy Laboratory & Department of Nuclear Engineering
Tipo: Relatório Formato: 6089884 bytes; application/pdf
EN_US
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A method for the analysis of the performance of standard industrial evaporative cooling tower drift eliminators using numerical simulation methods is reported. The simulation methods make use of the computer code SOLASUR as a subroutine of the computer code DRIFT to calculate the two dimensional laminar flow velocity field and pressure loss in a drift eliminator geometry. This information is then used in the main program to obtain the eliminator collection efficiency by performing trajectory calculations for droplet's of a given size by a fourth' order Runge-Kutta numerical method.; Topical report for Task #3 of the Waste Heat Management Research Program; New England Electric System & Northeast Utilities Service Co.

Stimulatory effect of cooling tower biocides on amoebae.

Srikanth, S; Berk, S G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1993 EN
Relevância na Pesquisa
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Two species of amoebae were isolated from the cooling tower of an air-conditioning system and examined for effects of exposure to four cooling tower biocides, a thiocarbamate compound, tributyltin neodecanoate mixed with quaternary ammonium compounds, another quaternary ammonium compound alone, and an isothiazolin derivative. The amoebae isolated were Acanthamoeba hatchetti and a Cochliopodium species. Two other amoeba cultures, an A. hatchetti culture and Cochliopodium bilimbosum, were obtained from the American Type Culture Collection (ATCC) and were also tested. The cooling tower isolates were more resistant to most of the biocides than the ATCC isolates were. The isothiazolin derivative was the least inhibitory to all four amoeba isolates, and tributyltin neodecanoate mixed with quaternary ammonium compounds was the most inhibitory to three of the four isolates. After exposure to lower concentrations of the biocides, including for one strain the manufacturer's recommended concentration of one biocide, the cooling tower amoeba populations increased significantly compared with unexposed controls, whereas the ATCC isolates were not stimulated at any of the concentrations tested. In some cases, concentrations which stimulated cooling tower amoebae inhibited the growth of the ATCC isolates. These results suggest that cooling tower amoebae may adapt to biocides...

Synthetic image generation of factory stack and water cooling tower plumes

Kuo, S. Didi
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Dissertação
EN_US
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Remote sensing of cooling tower and factory stack plumes may provide unique information on the constituents of the plume. Potential information of the power generated by the plant or the chemical composition of the factory products may be gathered from thermal emission and absorption in the infrared band, or from scattering of light in the visible band. A new model for generating synthetic images of plumes has been developed using DIRSIG, a radiometrically based ray-tracing code. Existing models that determine the characteristics of the plume (constituents, concentration, particulate sizing, and temperature) are used to construct the plume in DIRSIG. The effects of scattered light using Mie theory and radiative transfer, as well as thermal self-emission and absorption from within the plume, are modeled for different regions of the plume. Both single and multiple scattering methods are available. The ray-tracing accounts for radiance from the plume, atmosphere, and background. ' Synthetic generated images of a cooling tower plume, composed of water droplets, and a factory stack plume, composed of methyl chloride, are produced for visible, MWIR, and LWIR bands. Images of the plume from different sensor platforms are also produced. Observations are made on the interaction between the plume and its background and possible effects for remote sensing. Images of gas plumes using a hyperspectral sensor are illustrated. Several sensitivity studies are done to demonstrate the effects of changes in plume characteristics on the resulting image. Inverse algorithms that determine the plume effluent concentration are tested on the plume images. A validation is done on the gas plume model using experimental data collected on a SF6 plume. Results show the integrated plume model to be in good agreement with the actual data from five to one hundred meters from the stack exit. The scattering models are tested against MODTRAN. The validity and limitations of these models are discussed as a result of these tests. Finally two atmospheric scattering phenomena are illustrated to demonstrate qualitatively the scattering models.

Electrocoagulation to Remove Silica from Cooling Towers Water

Villegas-Mendoza,Iván Emmanuel; Martín-Domínguez,Alejandra; Pérez-Castrejón,Sara; Gelover-Santiago,Silvia Lucila
Fonte: Instituto Mexicano de Tecnología del Agua, Coordinación de Comunicación, Participación e Información Publicador: Instituto Mexicano de Tecnología del Agua, Coordinación de Comunicación, Participación e Información
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2014 EN
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This paper presents the results of a study carried out about the effect of water quality on the removal of dissolved silica using an electrocoagulation process with aluminum electrodes. Silica is found in replacement water (RW), usually known as make up water, and in cooling tower blowdown water (CTBW). Tests were conducted on a small pilot scale (~2 lmin-1) with a continuous flow device. The treatment train consisted of electrocoagulation (EC), flocculation, sedimentation and sand filtration. Two distinct RW and two CTBW with different physicochemical characteristics were studied. The response variables analyzed were: efficiency of aluminum to remove silica (ratio mgl-1 of dosed Al3+/mgl-1 SiO2 removed), removal efficiency of dosed Al3+, hydraulic head loss throughout the electrochemical reactor and voltage. The cost of the treatment for the four types of water is discussed. The ratio mgl-1 Al3+ dosed /mgl-1 silica removed ranged from 1.09 ± 0.06 to 1.33 ± 0.05 when treating RW and 0.85 ± 0.1 when treating CTBW. The consumption costs of energy, chemicals and electrodes for RW treatment ranged from US$ 0.52 to 0.74 m-3, and was approximately US$0.53 m-3 for CTBW.

Reduction of microbial biofilm formation using hydrophobic nano-silica coating on cooling tower fill material

Türetgen,Irfan
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2015 EN
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A cooling tower is a heat removal device, which extracts waste heat to the atmosphere through the cooling of a water stream to a lower temperature. Cooling towers are frequently associated with biofilm problems and Legionnaires disease outbreaks. Where biofilms can cause clogging and corrosion, reduction of biofilms is important for operational reasons and public health. Therefore, effective anti-biofilm strategies are needed in practice. The aim of the present study was to reduce biofilm formation using a nano-hydrophobic coating on cooling tower fill materials - polypropylene cooling tower fill material was coated with nano-silica. The effectiveness of the hydrophobic coating was investigated for a 6-month test period in a model cooling tower system, by monthly counting of the surface-associated bacteria using an epifluorescence microscope. A significant reduction (up to 4 log) in surface-associated bacteria was observed on coated test samples in comparison to uncoated control coupons. This study is the first report regarding the use of nano-silica coatings on cooling tower fills. The coating can be easily fabricated and the range of possible applications can be expanded to include a variety of conditions.