Letteratura scientifica selezionata sul tema "Multiple cooling towers"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Consulta la lista di attuali articoli, libri, tesi, atti di convegni e altre fonti scientifiche attinenti al tema "Multiple cooling towers".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Articoli di riviste sul tema "Multiple cooling towers"
1
Rubio-Castro, Eusiel, Medardo Serna-González, José María Ponce-Ortega e Mahmoud M. El-Halwagi. "Synthesis of cooling water systems with multiple cooling towers". Applied Thermal Engineering 50, n. 1 (gennaio 2013): 957–74. http://dx.doi.org/10.1016/j.applthermaleng.2012.06.015.
Testo completo
2
CHENG, X. X., L. ZHAO e Y. J. GE. "MULTIPLE LOADING EFFECTS ON WIND-INDUCED STATIC PERFORMANCE OF SUPER-LARGE COOLING TOWERS". International Journal of Structural Stability and Dynamics 13, n. 08 (21 ottobre 2013): 1350039. http://dx.doi.org/10.1142/s0219455413500399.
Testo completoAbstract (sommario):
Currently, four grouped 177 m super-large cooling towers, i.e. column-supported hyperboloidal shells, are to be constructed in a typical electric power plant in Southeast China. To this end, simultaneous pressure measurements on 1:200 rigid tower models are carried out in an atmospheric boundary layer (ABL) wind tunnel, aimed at accurately obtaining the external/internal cladding wind loads on these shells. The wind-induced static behavior of the cooling towers is analyzed by applying the wind loads acquired via the pressure model tests, using both linear elastic and nonlinear elastic finite element (FE) analyses. The corresponding responses (structural deformation, internal force and local buckling state) are compared with those obtained by the traditional design approach, focused on the effects of internal suction and external pressure distribution. Besides, the tower group interference effects are studied by comparing the results computed of a freestanding tower, with those of the tower groups during two different construction stages. The main findings about the loading effects on the static performance of the super-large cooling towers are helpful for improving the current Chinese Codes that govern the design of super-large cooling towers.
3
Guo, Yong, e Zhi Yong Liu. "Study on the Cooling Water Systems with Multiple Cooling Water Supplies". Advanced Materials Research 610-613 (dicembre 2012): 2497–500. http://dx.doi.org/10.4028/www.scientific.net/amr.610-613.2497.
Testo completoAbstract (sommario):
Water pinch technology is a process integration technology used for enterprises water system optimization, in order to improve the water reuse rate. Application of water pinch point technology to the whole system analysis and design, to establish a feasible performance index, and then determine the detailed process of design and transformation to achieve the predetermined target performance. This paper presents a technique for simultaneous targeting and design in cooling water systems comprising of at least two cooling towers and several cooling water using operations. Through comprehensive analysis on the cooling water systems with multiple cooling water supplies, determine the corresponding heat transfer process to the cooling tower, obtained better results than literature.
4
Gololo, Khunedi Vincent, e Thokozani Majozi. "On Synthesis and Optimization of Cooling Water Systems with Multiple Cooling Towers". Industrial & Engineering Chemistry Research 50, n. 7 (6 aprile 2011): 3775–87. http://dx.doi.org/10.1021/ie101395v.
Testo completo
5
Barrette, Isabelle. "Comparison of Legiolert and a Conventional Culture Method for Detection of Legionella pneumophila from Cooling Towers in Québec". Journal of AOAC INTERNATIONAL 102, n. 4 (1 luglio 2019): 1235–40. http://dx.doi.org/10.5740/jaoacint.18-0245.
Testo completoAbstract (sommario):
Abstract Background: Legionnaires’ disease is a potentially lethal pneumonia contracted through inhalation of aerosolized water contaminated with Legionella bacteria. Detection and control of L. pneumophila, the primary species responsible for the disease, is critical to public health. In Québec, cooling towers and evaporative condensers are required to follow a maintenance and testing program to ensure L. pneumophila concentrations remain at acceptable levels. Objective: This study compared a new culture method based on the most probable number approach, Legiolert®, with the formal culture method used at EnvironeX for regulatory compliance testing to quantify L. pneumophila from cooling tower waters in Québec. Methods: A split-sample analysis was performed in which 401 samples from cooling towers in Québec were tested with both methods. Results: Results with 74 positive samples showed that Legiolert provided a significant increase in sensitivity for L. pneumophila compared with the agar plate method. Cooling tower samples often contain non-Legionella flora that necessitate multiple treatment and plating conditions to prevent interference with the test. Legiolert showed little to no impact from non-Legionella organisms in this study. Conclusions: Overall, Legiolert showed several advantages over the agar plate method, including increased sensitivity, reduced interference, a simplified test procedure, and an easy-to-read positive signal.
6
KOOL, J. L., U. BUCHHOLZ, C. PETERSON, E. W. BROWN, R. F. BENSON, J. M. PRUCKLER, B. S. FIELDS et al. "Strengths and limitations of molecular subtyping in a community outbreak of Legionnaires' disease". Epidemiology and Infection 125, n. 3 (dicembre 2000): 599–608. http://dx.doi.org/10.1017/s095026880000474x.
Testo completoAbstract (sommario):
An epidemiological and microbiological investigation of a cluster of eight cases of Legionnaires' disease in Los Angeles County in November 1997 yielded conflicting results. The epidemiological part of the investigation implicated one of several mobile cooling towers used by a film studio in the centre of the outbreak area. However, water sampled from these cooling towers contained L. pneumophila serogroup 1 of another subtype than the strain that was recovered from case-patients in the outbreak. Samples from two cooling towers located downwind from all of the case-patients contained a Legionella strain that was indistinguishable from the outbreak strain by four subtyping techniques (AP-PCR, PFGE, MAb, and MLEE). It is unlikely that these cooling towers were the source of infection for all the case-patients, and they were not associated with risk of disease in the case-control study. The outbreak strain also was not distinguishable, by three subtyping techniques (AP-PCR, PFGE, and MAb), from a L. pneumophila strain that had caused an outbreak in Providence, RI, in 1993. Laboratory cross-contamination was unlikely because the initial subtyping was done in different laboratories.In this investigation, microbiology was helpful for distinguishing the outbreak cluster from unrelated cases of Legionnaires' disease occurring elsewhere. However, multiple subtyping techniques failed to distinguish environmental sources that were probably not associated with the outbreak. Persons investigating Legionnaires' disease outbreaks should be aware that microbiological subtyping does not always identify a source with absolute certainty.
7
Hunt, D. A., K. A. V. Cartwright, M. C. Smith, J. Middleton, C. L. R. Bartlett, J. V. Lee, P. J. Dennis e D. Harper. "An outbreak of Legionnaires' disease in Gloucester". Epidemiology and Infection 107, n. 1 (agosto 1991): 133–41. http://dx.doi.org/10.1017/s0950268800048767.
Testo completoAbstract (sommario):
SUMMARYFourteen people living in or near the city of Gloucester fell ill with Legionnaires' disease caused by Legionella pneumophila serogroup (SG) 1 between 27 August and 27 October 1986. Another patient had fallen ill on 30 May. Nine of the 15 were diagnosed retrospectively during a case finding exercise. There were three deaths. Three cases of Pontiac fever were also diagnosed.The source was probably one or more wet cooling towers. Nineteen premises in the city with such towers were identified, and three just outside Gloucester. Samples from 11 of the 22 premises grew Legionella spp.; from nine of these L. pneumophila SG 1 (Pontiac) was isolated. The efficacy of regular addition of biocide in addition to hypochlorite added at the time of disinfection in inhibiting the growth of Legionella spp. was demonstrated.A survey of patients' movements during their likely incubation period showed that there was no single building that all patients had visited, but there were two areas of the city which nearly all had visited or passed through by car. A case-control study demonstrated an association with one of these areas.Cooling towers near both areas may have been sources but the evidence is insufficient to incriminate any single one. The unexpected finding of L. pneumophila SG 1 (Pontiac) in nine towers supports the hypothesis that there may have been multiple sources. Cooling towers may have been contaminated by mains water or by drift from other towers.
8
Young, Charlotte, Duncan Smith, Tim Wafer e Brian Crook. "Rapid Testing and Interventions to Control Legionella Proliferation following a Legionnaires’ Disease Outbreak Associated with Cooling Towers". Microorganisms 9, n. 3 (17 marzo 2021): 615. http://dx.doi.org/10.3390/microorganisms9030615.
Testo completoAbstract (sommario):
Most literature to date on the use of rapid Legionella tests have compared different sampling and analytical techniques, with few studies on real-world experiences using such methods. Rapid tests offer a significantly shorter feedback loop on the effectiveness of the controls. This study involved a complex of five factories, three of which had a history of Legionella contamination in their cooling water distribution system. Multiple sampling locations were utilised to take monthly water samples over 39 months to analyse for Legionella by both culture and quantitative polymerase chain reaction (qPCR). Routine monitoring gave no positive Legionella results by culture (n = 330); however, samples were frequently (68%) positive by qPCR for Legionella spp. (n = 1564). Legionella spp. qPCR assay was thus found to be a good indicator of cooling tower system health and suitable as a routine monitoring tool. An in-house qPCR limit of 5000 genomic units (GU)/L Legionella spp. was established to trigger investigation and remedial action. This approach facilitated swift remedial action to prevent Legionella proliferation to levels that may represent a public health risk. Cooling tower operators may have to set their own action levels for their own systems; however, in this study, 5000 GU/L was deemed appropriate and pragmatic.
9
Thornley, C., D. Harte, R. Weir, L. Allen e P. Wood. "Mixed species legionellosis outbreak linked to industrial cooling towers contaminated with multiple Legionella species, New Zealand, August-November 2015". International Journal of Infectious Diseases 53 (dicembre 2016): 138–39. http://dx.doi.org/10.1016/j.ijid.2016.11.341.
Testo completo
10
Sobral, D., P. Le Cann, A. Gerard, S. Jarraud, B. Lebeau, F. Loisy-Hamon, G. Vergnaud e C. Pourcel. "High-Throughput Typing Method To Identify a Non-Outbreak-Involved Legionella pneumophila Strain Colonizing the Entire Water Supply System in the Town of Rennes, France". Applied and Environmental Microbiology 77, n. 19 (5 agosto 2011): 6899–907. http://dx.doi.org/10.1128/aem.05556-11.
Testo completoAbstract (sommario):
ABSTRACTTwo legionellosis outbreaks occurred in the city of Rennes, France, during the past decade, requiring in-depth monitoring ofLegionella pneumophilain the water network and the cooling towers in the city. In order to characterize the resulting large collection of isolates, an automated low-cost typing method was developed. The multiplex capillary-based variable-number tandem repeat (VNTR) (multiple-locus VNTR analysis [MLVA]) assay requiring only one PCR amplification per isolate ensures a high level of discrimination and reduces hands-on and time requirements. In less than 2 days and using one 4-capillary apparatus, 217 environmental isolates collected between 2000 and 2009 and 5 clinical isolates obtained during outbreaks in 2000 and 2006 in Rennes were analyzed, and 15 different genotypes were identified. A large cluster of isolates with closely related genotypes and representing 77% of the population was composed exclusively of environmental isolates extracted from hot water supply systems. It was not responsible for the known Rennes epidemic cases, although strains showing a similar MLVA profile have regularly been involved in European outbreaks. The clinical isolates in Rennes had the same genotype as isolates contaminating a mall's cooling tower. This study further demonstrates that unknown environmental or genetic factors contribute to the pathogenicity of some strains. This work illustrates the potential of the high-throughput MLVA typing method to investigate the origin of legionellosis cases by allowing the systematic typing of any new isolate and inclusion of data in shared databases.
Tesi sul tema "Multiple cooling towers"
1
Gololo, Khunedi Vincent. "Analysis, synthesis and optimization of complex cooling water systems". Thesis, 2013. http://hdl.handle.net/2263/32820.
Testo completoAbstract (sommario):
Cooling water systems are used to remove excess heat from a chemical process to the atmosphere. The primary components of these systems are the cooling tower and the heat exchanger network. There is a strong interaction between these individual components, thus their performances are interrelated. Most published research in this area has focused mainly on optimization of the individual components i.e. optimization of heat exchanger network or optimization of the cooling towers. This approach does not optimize the cooling water system as a whole. Previous research work in which a holistic approach was used is limited to cooling water systems with single cooling water source.
This work presents a technique for integrated optimization of complex cooling water systems. The system under consideration consists of multiple cooling towers each supplying a set of heat exchangers. A superstructural approach is employed to explore all possible combinations between the heat exchangers and the cooling towers. The cooling water reuse opportunities within the heat exchanger networks are also explored. A detailed mathematical model consisting of the cooling towers and the heat exchanger networks model is developed. Two practical scenarios are considered and the mathematical formulations for Case I and II yield nonlinear programing (NLP) and mixed integer nonlinear programming (MINLP) structure respectively.
Although the reuse/recycle philosophy offers a good debottlenecking opportunity, the topology of the associated cooling water network is more complex, hence prone to higher pressure drop than the conventional parallel design. This is due to an increased network pressure drop associated with additional reuse/recycle streams. Therefore, it is essential to consider pressure drop during the synthesis of cooling water networks where the reuse/recycle philosophy is employed. The on-going research in this area is only limited to cooling water networks consisting of a single cooling water source. The common technique used is mathematical optimization using either superstructural or non superstructural approach.
This work further presents a mathematical technique for pressure drop optimization in cooling water systems consisting of multiple cooling towers. The proposed technique is based on the Critical Path Algorithm and the superstructural approach. The Critical Path Algorithm is used to select the cooling water network with minimum pressure drop whilst the superstructural approach allows for cooling water reuse. The technique which was previously used in a cooling water network with single source is modified and applied in a cooling water network with multiple sources. The mathematical formulation is developed considering two cases. Both cases yield mixed integer nonlinear programming (MINLP) models. The cooling tower model is also used to predict the exit condition of the cooling tower given the inlet conditions from the cooling water network model.
The results show up to 29% decrease in total circulating cooling water flowrate when the cooling water system is debottlenecked without considering pressure drop. Consequently, the overall cooling towers effectiveness was improved by up to 5%. When considering pressure drop the results showed up to 26% decrease in total circulating water flowrate.Thesis (PhD)--University of Pretoria, 2013.
gm2013
Chemical Engineering
unrestricted
Capitoli di libri sul tema "Multiple cooling towers"
1
Gololo, Khunedi V., e Thokozani Majozi. "Pressure Drop Consideration in Cooling Water Systems with Multiple Cooling Towers". In Computer Aided Chemical Engineering, 690–94. Elsevier, 2012. http://dx.doi.org/10.1016/b978-0-444-59507-2.50130-x.
Testo completoAtti di convegni sul tema "Multiple cooling towers"
1
Langenstein, Magnus, e Jan Hansen-Schmidt. "The Worlds’ First Ever Cooling Tower Acceptance Test Using Process Data Reconciliation". In 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89643.
Testo completoAbstract (sommario):
The cooling capacity of cooling towers is influenced by multiple constructive and atmospheric parameters in a very complex way. This leads to strong variations of the measured cold-water temperature and causes unacceptable unreliability of conventional acceptance tests, which are based on single point measurements. In order to overcome this lack of accuracy a new approach to acceptance test based on process data reconciliation has been developed by BTB Jansky and applied at a nuclear power plant. This approach uses process data reconciliation according to VDI 2048 [1, 2] to evaluate datasets over a long period covering different operating conditions of the cooling tower. Data reconciliation is a statistical method to determine the true process parameters with a statistical probability of 95% by considering closed material-, mass- and energy balances. Datasets which are not suitable for the evaluation due to strong transient gradients are excluded beforehand, according to well-defined criteria. The reconciled cold-water temperature is then compared, within a wet bulb temperature range of 5°C to 20°C to the manufacturer’s guaranteed temperature. Finally, if the average deviation between reconciled and guaranteed value over the evaluated period is below zero, the cooling tower guarantee is fulfilled.
2
Werth, David, e Matthew Havice. "A Review of Common Problems Observed in Cooling Water Intakes and the Use of Physical Models to Develop Effective Solutions". In ASME/JSME/KSME 2015 Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ajkfluids2015-33776.
Testo completoAbstract (sommario):
Pump intake structures are a necessary component of the cooling water systems for power plants, process and manufacturing facilities, flood control and water/wastewater applications. Large cooling water systems often use substantial sea / river water intakes or cooling towers to provide the required cooling of the process or circulating water. These structures can be very large and often house multiple pump with capacities ranging in size from a few hundred m3/hr to 60,000 m3/hr or more. With such large flow rates care must be taken to ensure uniform flow to the pump to limit vortex activity, vibration, flow induced cavitation and performance problems. In many cases, a physical hydraulic model study is conducted to evaluate the overall approach flow and the performance of the intake. This paper presents a synopsis of several recent physical model studies and a review of recurring problems associated with common design features. This paper takes a closer look at stop log support walls, an intake design feature common to seawater intakes. This wall is often used to minimize the height of the stop logs. In applications with large variations of water level, such as a seawater intake, there are times when the support walls are submerged significantly, resulting in significant flow disturbances. A feature common to cooling towers is the use of 90-degree suction elbows to supply horizontal pumps. A review of short radius vs. long radius elbow performance is presented. Cooling towers often have another common feature which is a significant difference in depth between the cooling tower basin and the pump sump. This results in typical shallow basins and deeper sumps. A common problem is the utilization of minimum pump submergence to set the water levels without reference to the basin invert elevation. A discussion of choked flow conditions in cooling towers is presented. A final discussion is presented regarding cross-flow and the use of concentrated supply channels in cooling tower applications to facilitate the isolation of individual tower cells. This paper presents a synopsis of several recent physical model studies and a review of recurring problems associated with common intake design features. The results of several model studies are presented to demonstrate the negative impacts that these common intake features have on approach flow conditions. The intent of the paper is to provide the design engineer some additional guidance not offered in industry guidelines or standards with the hope of avoiding common problems which can be costly and difficult to remediate after the intake has been constructed.
3
Van Der Linden, Septimus, e David E. Searles. "Inlet Conditioning Enhances Performance of Modern Combined Cycle Plants for Cost-Effective Power Generation". In ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-gt-298.
Testo completoAbstract (sommario):
This paper will examine the performance enhancement and cost benefits of inlet air conditioning applied to a modern combined cycle plant at high ambients, resulting in lower electricity production costs. Site specific cases are presented to demonstrate a broad range of application and cost benefits. The successful project in today’s aggressive competitive power marketplace is most typically defined as “lowest $/kW”. Traditional combined cycle plants have been driven to higher levels of efficiency by increasing gas turbine heat recovery using large, multiple pressure level heat recovery steam generators and improving heat sink technologies with aggressive cooling towers or air cooled condensers. This methodology rapidly produced less competitive results as the price of new generation was reduced. The driving technology behind this change was the development of high output, high efficiency advanced gas turbines. Improved metallurgy, cooling schemes and blade coating systems permitted each GT manufacturer to offer improved output and efficiencies. These improvements, coupled with industry uncertainty due to the threat of deregulation and consequential reduction in new generation opportunities, has allowed new performance standards to be realized for equal or lower unit prices, leading to an unparalleled reduction of installed cost for new power plants.
4
Audivet Durán, Cinthia, e Marco E. Sanjuán. "On-Line Early Fault Detection of a Centrifugal Chiller Based on Data Driven Approach". In ASME 2016 10th International Conference on Energy Sustainability collocated with the ASME 2016 Power Conference and the ASME 2016 14th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/es2016-59291.
Testo completoAbstract (sommario):
A district cooling system (DCS) is a system that distributes thermal energy through chilled water from a central source to residential, commercial, or industrial consumers, designated to air conditioning purposes. It is one of the most important part of a heating, ventilation, air conditioning and refrigeration systems (HVAC), because a DCS is composed of: Cooling towers, central chiller plant, water distribution systems and clusters of consumer buildings. This research is focused on the central chiller plant, due to it accounts for a substantial portion of the total energy consume of DCS and HVAC systems. The performance of central chiller plant is often affected by multiple faults which could be caused during installation or developed in routine operation. These non-optimal conditions and faults may cause 20–30% waste of energy consumption of HVAC&R systems. Automated fault detection and diagnosis (AFDD) tools have potential to detect an incipient fault and help to reduce undesirable conditions and energy consumption, and optimize the facility maintenance. We propose an online data driven fault detection strategy for district cooling system. The main objective is to develop an automated fault detection tool based on historical process data, which can be applied in transient operation. The proposed hybrid strategy is based on unsupervised and supervised learning techniques, and multivariate statistic techniques. Its aim is to identify the operating states of the chiller and evaluate the fault occurrence depending of its current operating state. This strategy uses the K-means clustering method, Naive Bayes classifier and Principal Component Analysis (PCA). The developed strategy was evaluated using the performance data of a 90-ton water-cooled centrifugal chiller (ASHRAE RP-1043) and also evaluated using a dynamic model of a chiller (Simscape™.) under similar conditions. The results show the advantages of novel early fault detection technique compared to Conventional PCA method in terms of sensitivity to faults occurrence and reduction of missed detection rate.
5
Li, Wei, Guanqiu Li, Zhengjiang Zhang, Zhiming Xu e Shanrang Yang. "Analysis of Fouling Characteristic in Enhanced Tubes Using Multiple Analogies". In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22529.
Testo completoAbstract (sommario):
This paper provides a comprehensive analysis on cooling tower fouling data taken from seven 15.54 mm I.D. helically ribbed, copper tubes and a plain tube at Re = 16000. A new mathematical model has been developed. The mass transfer coefficient Km is calculated through three analogies, which are Prandtl analogy, Von-Karman analogy, and j factor analogy. Fouling deposition is assumed to be determined by two processes, which are corresponding to heat flux and fluid friction. Von-Karman analogy is proved the best analogy among the three. Series of semi-theoretical fouling correlations as a function of the product of area indexes and efficiency indexes were developed. They were applicable to different internally ribbed geometries. The correlations can be directly used to assess the fouling potential of enhanced tubes in actual cooling tower water situations.
6
Singh, Kuljeet, e Ranjan Das. "Multi Parameter Estimation in an Induced Draft Cooling Tower Using Genetic Algorithm". In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-66864.
Testo completoAbstract (sommario):
Considering the need of performance control in engineering systems, this work presents a methodology to predict the controlling variables to control the performance of an induced draft cooling tower. At first, the set of experiments have been conducted with the variation of mass flow rate of water and air under identical ambient conditions. The experimental data for temperatures at different locations has been collected using data acquisition system (by National Instruments) in conjunction with LABVIEW™. Thereafter, relevant 3rd order empirical correlations of range and approach have been developed using the experimental readings. Depending upon the pertinent requirement, it is required to operate the cooling tower at certain combination of mass flow rate of water and air to fulfill the required output. Based upon the user requirement, the correlations are further employed to construct relevant constraint functions using the least square technique. In order to meet a desired performance (say either a given range, approach or optimum operation) of the cooling tower, the retrieval of design variables (water and air flow rates) has been carried out using an inverse optimization methodology to ensure minimum power consumption. The Genetic Algorithm (GA) is used as an optimization algorithm that minimizes the objective function along with given constraint. The optimization algorithm simultaneously predicts the possible combination of mass flow rate of water and air (control or design variables) in order to meet the given requirement. Further, the methodology avoids multiple combinations of controlling variables that satisfies a particular requirement. Therefore, the user can select an optimum combination that results in minimum power consumption. Moreover, if the cost involved in the cooling tower is considered, it is directly proportional to the range (difference between water inlet and outlet temperatures), whereas, at the same time, the cost is inversely proportional to the approach (difference between outlet water temperature and inlet air wet bulb temperature). In many applications like HVAC (heating, ventilating and air conditioning), chillers, cold storage plants and many more, lower cooling water temperature (at system inlet) is preferable in order to enhance the system efficiency. On the other hand, lower water outlet temperature from the cooling tower for a given water inlet temperature (at tower inlet) means either high range of the tower or low approach, consequently increasing the tower operating cost. Therefore, in order to save the cost involved in cooling tower operation, a compromise between the range and the approach has to be maintained to achieve an optimum performance. So, this method can be also used to predict the optimum operating parameters ensuring the possible optimum performance from the cooling tower under a given set of operating conditions.
7
Jonsson, M., D. Charbonnier, P. Ott e J. von Wolfersdorf. "Application of the Transient Heater Foil Technique for Heat Transfer and Film Cooling Effectiveness Measurements on a Turbine Vane Endwall". In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50451.
Testo completoAbstract (sommario):
The paper presents an application of the transient heater foil measurement technique using thermochromic liquid crystals (TLC) to endwall heat transfer and film cooling investigations in a transonic turbine vane cascade. The film cooling configuration consists of an upstream slot, representing the leakage flow area between the interface of the combustor and the turbine, and several rows of cylindrical and fan-shaped holes within the passage. With the transient method chosen, the heat transfer and adiabatic film cooling effectiveness distributions can be obtained simultaneously together with the local heat release within the heater foil. Therefore, the heat release in the foil is not required to be uniform, and the foil can contain discrete holes in the film cooling configuration. Some new developments are presented, which are directed towards improved application of the transient heater foil method for such a complex configuration. This includes tailoring the foil heat-release distribution towards the expected heat transfer patterns, supported by numerical Finite-Element computations and the use of a double-TLC mixture for improved time-wise TLC indications. Additionally, CFD-simulations were used to evaluate the recovery temperature distribution through the vane cascade without film cooling. The experiments were performed in the linear cascade facility at the EPFL-Lausanne. A compressor provides a continuous air flow at near-ambient temperature regulated with heat exchangers. Carbon dioxide is used as coolant in order to achieve engine-representative density ratio between coolant and main flow. Multiple experiments with the same main and coolant flow settings but varying heat flux levels and coolant injection temperatures have been performed and simultaneously analysed using nonlinear regression analysis. The time required between successive experiments to return to homogenous initial conditions, as required by the transient method, has been analysed using an analytical solution for heat-on-heat-off conditions. This permits the model assumption of one-dimensional conduction within a semi-infinite wall with a heat releasing layer on the top. Example results for cases without cooling, with film cooling from rows of discrete holes and the addition of slot film cooling are used to illustrate the benefit of the new approaches for the investigated vane cascade.
8
Sundaram, N., M. D. Barringer e K. A. Thole. "Effects of Deposits on Film Cooling of a Vane Endwall Along the Pressure Side". In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27131.
Testo completoAbstract (sommario):
Film-cooling is influenced by surface roughness and depositions that occur from contaminants present in the hot gas path, whether that film-cooling occurs on the vane itself or on the endwalls associated with the vanes. Secondary flows in the endwall region also affect the film-cooling performance along the endwall. An experimental investigation was conducted to study the effect of surface deposition on film-cooling along the pressure side of a first-stage turbine vane endwall. A large-scale wind tunnel with a turbine vane cascade was used to perform the experiments. The vane endwall was cooled by an array of film-cooling holes along the pressure side of the airfoil. Deposits having a semi-elliptical shape were placed along the pressure side to simulate individual row and multiple row depositions. Results indicated that the deposits lowered the average adiabatic effectiveness levels downstream of the film-cooling rows by deflecting the coolant jets towards the vane endwall junction on the pressure side. Results also indicated that there was a steady decrease in adiabatic effectiveness with a sequential increase in the number of rows with the deposits.
9
Ghani, M. Usman, Ovidiu Marin e Martin Theriault. "A One-Dimensional Model for Cooling of Optical Fibers". In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-41921.
Testo completoAbstract (sommario):
This paper presents a one-dimensional model for the cooling of optical fibers. Heat transfer between the fiber, gas and wall, by conduction, convection, and radiation, are taken into account. The model offers advanced features such as multiple inlets and outlets. Six different pure gases or their mixtures may be used to study the effect of gas composition. The forced convection heat transfer coefficient is computed using the correlation for the forced convection in tubes and conduits. This correlation is then corrected to account for the enhanced heat transfer due to the motion of the fiber. This factor is determined from the limited experimental data available in the literature. The mathematical model consists of a system of ordinary differential equations and is solved using the LSODE solver. The model was used to study the effect of various operational parameters. The results show that at the typical conditions used in a commercial draw tower, Helium is the most effective cooling medium. A smaller diameter exchanger is more effective in cooling the fiber. More cooling is achieved if the incoming gas temperature is lower as well as if the cooler wall is kept at a lower temperature. The most critical factor is the fiber draw speed. At higher draw speeds, the residence time is low, which leads to shorter contact time for the fiber and gas to exchange heat. The effect of gas flow rate is not very significant, provided the flow regime is laminar. The turbulence flow regime is, in general, not desirable as it may cause vibrations, which is detrimental to fiber properties such as diameter and strength. Comparisons of the one-dimensional model results with the results of a two-dimensional model as well as simulations using Fluent, a commercial CFD package, are also presented. The results of these simulations may be used for an improved design of an exchanger, providing more efficient cooling of optical fiber. An improved design of exchanger will be the focus of future work in this area.
10
So¨zbir, Nedim, e Shi-Chune Yao. "Experimental Studies of Using Water Mist Cooling for the Tempering of Glass". In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32524.
Testo completoAbstract (sommario):
Very high velocity air jet impingement has been applied during the cooling process of glass tempering. In order to reduce the usage of high-pressure air in the process, it is intended to demonstrate the feasibility of using water mist to enhance the air-cooling. The multiple jet experiments were performed using air jet velocities between 40 and 90 m/sec containing low mass flux of water mist that was varied from 0 up to 0.145 kg/m2sec for each jet. The experiments include different glass thickness. The optimal tempering conditions were explored. The mechanisms of mist cooling are revealed from the experiments of a single water mist jet impinging on hot stainless steel plates. Since the droplets are small, on the order of 20 micron, heat transfer distribution of the water mist has a similar form as the air jet cooling. The total heat transfer coefficient can be viewed as two separable effects: the summation of the heat transfer coefficient of the convective air and of the impinging water flux, respectively. The heat transfer of multiple water mist jets on larger glass is studied. When the liquid flux is too high or when the surface temperature falls below the Leidenfrost temperature, excessive local thermal stress will occur, which leads to cracking of glass. It is possible to reach the optimal tempering with a moderate amount of water applied on the glass surface for a short duration of time. The mist cooling demonstrates a definitive saving on the use of high-pressure air. When using mist cooling, the energy requirements of the system are significantly lowered. The mist cooling creates more refined fracturing in the punching tests of tempered glass. For glass thicker than 3 mm, the particle counts due to water mist improve about 121%. For 2 mm glass, the improvement is about 38%. The mist cooling of the thinnest glass is still not able to give the desired particle counts. But definitive improvement toward this objective is shown. Further studies of other alternatives may give a chance to achieve this goal.