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1
Golden, James Hollis. "Ammonia - water desorption in flooded columns." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44884.
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Refrigeration systems employing the NH3-H2O absorption cycle provide cooling using a thermal energy input. This cycle relies on the zeotropic nature of the refrigerant - absorbent pair: because of the difference in boiling temperatures between NH3 and H2O, they can be separated through selective boiling in the desorber. Desorbers with counter-current flow of the solution and generated vapor enable efficient heat and mass transfer between the two phases, reducing the absorbent content in the generated vapor.
Flow visualization experiments at temperatures, concentrations and pressures representative of operating conditions are necessary to understand the heat and mass transfer processes and flow regime characteristics within the component. In this study, a Flooded Column desorber, which accomplishes desorption of the refrigerant vapor through a combination of falling-film and pool boiling, was fabricated and tested. Refrigerant-rich solution enters the top of the component and fills a column, which is heated by an adjacent heated microchannel array. The vapor generated within the component is removed from the top of the component, while the dilute solution drains from the bottom.
Flow visualization experiments showed that the Flooded Column desorber operated most stably in a partially flooded condition, with a pool-boiling region below a falling-film region. It was found that the liquid column level was dependent on operating conditions, and that the pool-boiling region exhibits aggressive mixing between the vapor and solution phases.
Heat transfer coefficients were calculated from the data for the pool-boiling region, and were compared with the predictions of several mixture pool-boiling correlations from the literature. The correlations from the literature were in general unable to predict the data from this study adequately. It was found that the Flooded Column desorber yielded higher heat transfer coefficients within the pool-boiling region than those predicted by these correlations. Therefore, modifications to existing mixture boiling correlations are suggested based on the findings of this study. The resulting modified correlation predicts 33 of the 35 data points from this study within ±40%, with an average absolute error of 19%.
2
Bittner, Andrew (Andrew Benjamin) 1974. "Nepal drinking water quality assessment : nitrates and ammonia." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/80930.
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Griffiths, Gareth Ivor Goulbourn. "First-principles studies of the ammonia-water system." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610671.
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4
Thorin, Eva. "Power cycles with ammonia-water mixtures as working fluid." Doctoral thesis, KTH, Chemical Engineering and Technology, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2976.
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It is of great interest to improve the efficiency of powergenerating processes, i.e. to convert more of the energy in theheat source to power. This is favorable from an environmentalpoint of view and can also be an economic advantage. To use anammonia-water mixture instead of water as working fluid is apossible way to improve the efficiency of steam turbineprocesses.
This thesis includes studies of power cycles withammonia-water mixtures as working fluid utilizing differentkinds of heat sources for power and heat generation. Thethermophysical properties of the mixture are also studied. Theyplay an important role in the calculations of the processperformance and for the design of its components, such as heatexchangers. The studies concern thermodynamic simula-tions ofprocesses in applications suitable for Swedish conditions.Available correla-tions for the thermophysical properties arecompared and their influence on simula-tions and heat exchangerarea predictions is investigated. Measurements of ammonia-watermixture viscosities using a vibrating wire viscometer are alsodescribed.
The studies performed show that power cycles withammonia-water mixtures as the working fluid are well suited forutilization of waste heat from industry and from gas engines.The ammonia-water power cycles can give up to 32 % more powerin the industrial waste heat application and up to 54 % morepower in the gas engine bottoming cycle application compared toa conventional Rankine steam cycle. However, ammonia-waterpower cycles in small direct-fired biomass-fueled cogene-rationplants do not show better performance than a conventionalRankine steam cycle.
When different correlations for the thermodynamic propertiesare used in simulations of a simple ammonia-water power cyclethe difference in efficiency is not larger than 4 %,corresponding to about 1.3 percentage points. The differencesin saturation properties between the correlations are, however,considerable at high pressures, high temperatures and high massfractions of ammonia. The use of different correlations for thethermodynamic and transport properties causes a noticeabledifference in the predicted heat exchanger areas required fordifferent processes.
Keywords:ammonia-water mixture, cogeneration,correlation, direct-fired power cycle, gas engine, Kalinacycle, power cycle, thermophysical properties, waste heat
5
Viswanathan, Vinodh Kumar. "Dynamic model for small-capacity ammonia-water absorption chiller." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/48939.
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Optimization of the performance of absorption systems during transient operations such as start-up and shut-down is particularly important for small-capacity chillers and heat pumps to minimize lifecycle costs. Dynamic models in the literature have been used to study responses to step changes in a single parameter, but more complex processes such as system start-up have not been studied in detail. A robust system-level model for simulating the transient behavior of an absorption chiller is developed here.
Individual heat and mass exchangers are modeled using detailed segmental models. The UA-values and thermal masses of heat exchangers used in the model are representative of a practical operational chiller. Thermal masses of the heat exchangers and energy storage in the heat exchanging fluids are accounted for to achieve realistic transient simulation of the heat transfer processes in the chiller. The pressure drop due to fluid flow across the heat exchangers is considered negligible in comparison to the pressure difference between the high- and low-side components (~ 1.5 MPa). In components with significant mass transfer effects, reduced-order models are employed to decrease computational costs while also maintaining accurate system response.
Mass and species storage in the cycle are modeled using storage devices. The storage devices account for expansion and contraction of the refrigerant and solution in the cycle as the system goes through start-up, shut-down, and other transient events. A counterflow falling film desorber model is employed to account for the heat and mass transfer interactions between the liquid and vapor phases, inside the desorber. The liquid film flows down counter to the rising vapor, thereby exchanging heat with the counterflowing heated coupling fluid. A segmented model is used to account for these processes, and a solver is developed for performing rapid iteration and quick estimation of unknown vapor and liquid states at the outlet of each segment of the desorber. Other components such as the rectifier, expansion valves and solution pump are modeled as quasi-steady devices.
System start-up is simulated from ambient conditions, and the coupling fluid temperatures are assumed to start up to their steady-state values within the first 90 s of simulation. It is observed that the system attains steady-state in approximately 550 s. The evaporator cooling duty and COP of the chiller during steady-state are observed to be 3.41 kW and 0.60, respectively. Steady-state parameters such as flow rates, heat transfer rates and concentrations are found to match closely with results from simulations using corresponding steady-state models. Several control responses are investigated using this dynamic simulation model. System responses to step changes in the desorber coupling fluid temperature and flow rate, solution pumping rate, and valve setting are used to study the effects of several control strategies on system behavior. Results from this analysis can be used to optimize start-up and steady state performances. The model can also be used for devising and testing control strategies in commercial applications.
6
Molyneaux, Glenn Arthur. "Resorption cycle heat pump with ammonia-water working fluid." Thesis, University of Ulster, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326335.
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7
Michalsky, Ronald. "Thermochemical production of ammonia using sunlight, air, water and biomass." Diss., Kansas State University, 2012. http://hdl.handle.net/2097/13823.
Full textAbstract:
Doctor of PhilosophyDepartment of Chemical Engineering
Peter H. Pfromm
Approximately 45% of the global hydrogen production (from fossil fuels such as natural gas or coal totaling 2% of the global energy generation) is absorbed as feedstock in the synthesis of over 130 million metric tons ammonia (NH[subscript]3) annually. To achieve food security for a growing world population and to allow for additional uses of the nitrogen-fertilizer for production of bio-energy feedstock or as combustion fuel or H[subscript]2 carrier - demand for NH[subscript]3 is projected to increase. This work pursues the synthesis of ammonia at atmospheric pressure and without fossil fuel. Conceptually, concentrated solar radiation is utilized to transfer electrons from the lattice oxygen of a transition metal oxide to the metal ion. This yields a metallic reactant that provides the reducing power for the subsequent six-electron reductive cleavage of N[subscript]2 forming a transition metal nitride. In a second reaction, the generated lattice nitrogen is hydrogenated with hydrogen from H[subscript]2O to NH[subscript]3. This furnishes the transition metal oxide for perpetuated NH[subscript]3 synthesis. Theory and experimentation identified manganese nitride as a promising reactant with fast diffusion characteristics (8 ± 4 x 10[superscript]-9 cm[superscript]2 s [superscript]-1 apparent nitrogen diffusion constant at 750 degree C) and efficient liberation of 89 ± 1 mol% nitrogen via hydrolysis at 500 degree C. Opposed to only 2.9 ± 0.2 mol% NH[subscript]3 from manganese nitride, 60 ± 8 mol% of the nitrogen liberated from molybdenum nitride could be recovered as NH[subscript]3. Process simulation of a Mo-based NH[subscript]3 synthesis at 500-1200 degree C estimates economically attractive production under fairly conservative process and market conditions. To aid the prospective design of a Mn or Mo-based reactant, correlating the diffusion constants for the hydrolysis of seven nitrides with the average lattice nitrogen charge (9.96-68.83%, relative to an ideal ionic solid) indicates the utility of first-principle calculations for developing an atomic-scale understanding of the reaction mechanism in the future.
8
Mizak, Constance Anne. "Ammonia flux at the air/water interface of Tampa Bay." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000273.
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9
Berdasco, Ruiz Miguel Ángel. "Study of the ammonia absorption process into ammonia/water solutions using polymeric membranes for absorption-resorption refrigeration systems." Doctoral thesis, Universitat Rovira i Virgili, 2018. http://hdl.handle.net/10803/586260.
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En aquesta tesi s’estudia el procés d’absorció d’amoníac en dissolucions d’amoníac/aigua utilitzant membranes polimèriques com a contactors per a la seva integració en els sistemes de refrigeració per absorció-resorció. L’elevada relació superfície/volum proporcionada per les membranes permet reduir la mida dels absorbidors i així poder dissenyar equips de refrigeració més compactes i lleugers. Es proposa utilitzar sistemes de refrigeració per absorció-resorció d’amoníac/aigua ja que permeten reduir l’elevada pressió de treball dels sistemes d’absorció convencionals, fent viable l’ús de materials polimèrics.
Inicialment es presenta un estudi del cicle de refrigeració per absorció-resorció d’amoníac/aigua mitjançant models termodinàmics, així com l’anàlisi del funcionament d’una planta de refrigeració per absorció-resorció de 25 kW. Per a l’estudi experimental del procés d’absorció adiabàtic d’amoníac en dissolucions d’amoníac/aigua es va construir un banc d’assajos en què es van provar dos mòduls diferents: membrana plana i fibres buides. En tots dos casos es van desenvolupar models teòrics que van ser validats amb els resultats experimentals. Fruit de l’estudi de la membrana plana es van determinar les característiques requerides per una membrana polimèrica per al seu ús en el procés d’absorció de l’amoníac. Aquestes característiques es van tenir en compte a l’hora de seleccionar el mòdul comercial de fibres buides. Finalment es va desenvolupar un model teòric d’un absorbidor de membranes de fibra buida amb intercanviador de calor integrat. Aquest model es va utilitzar per dissenyar un absorbidor i un resorbidor per al sistema de refrigeració per absorció-resorció de 25 kW. Els resultats obtinguts confirmen el potencial de reducció de mida que ofereixen les membranes, ja que es van obtenir relacions de càrrega tèrmica/volum de fins a 10000 kW/m3, molt superiors a les proporcionades pels absorbidors de plaques (2000 kW/m3) o de carcassa i tubs (300 kW/m3).En esta tesis se estudia el proceso de absorción de amoniaco en disoluciones de amoniaco/agua utilizando membranas poliméricas como contactores para su integración en los sistemas de refrigeración por absorción-resorción. La elevada relación superficie/volumen proporcionada por las membranas permite reducir el tamaño de los absorbedores y así poder diseñar equipos de refrigeración más compactos y ligeros. Se propone utilizar sistemas de refrigeración por absorción-resorción de amoniaco/agua debido a que permiten reducir la elevada presión de trabajo de los sistemas de absorción convencionales, haciendo viable la utilización de materiales poliméricos. Inicialmente se presenta un estudio del ciclo de refrigeración por absorción-resorción de amoniaco/agua mediante modelos termodinámicos, así como el análisis del funcionamiento de una planta de refrigeración por absorción-resorción de 25 kW. Para el estudio experimental del proceso de absorción adiabático de amoniaco en disoluciones de amoniaco/agua se construyó un banco de ensayos en el que se probaron dos módulos diferentes: membrana plana y fibras huecas. En ambos casos se desarrollaron modelos teóricos que fueron validados con los resultados experimentales. Fruto del estudio con la membrana plana se determinaron las características requeridas por una membrana polimérica para su utilización en el proceso de absorción de amoniaco. Dichas características se tuvieron en cuenta a la hora de seleccionar el módulo comercial de fibras huecas. Finalmente, se desarrolló un modelo teórico de un absorbedor de membranas de fibra hueca con intercambiador de calor integrado. Este modelo se utilizó para diseñar un absorbedor y un resorbedor para el sistema de refrigeración por absorción-resorción de 25 kW. Los resultados obtenidos confirman el potencial de reducción de tamaño que ofrecen las membranas ya que se obtuvieron relaciones de carga térmica/volumen de hasta 10000 kW/m3, muy superiores a las proporcionadas por los absorbedores de placas (2000 kW/m3) o los de carcasa y tubos (300 kW/m3).
This thesis studies the ammonia absorption process into ammonia/water solutions using polymeric membranes as contactors in order to be used in the absorption-resorption refrigeration systems. The high surface/volume ratio provided by the membranes enable to reduce the size of the absorbers and, therefore, more compact and lighter designs can be made. The use of absorption-resorption refrigeration systems is proposed because they allow to reduce the typically high working pressure of the conventional absorption systems, making feasible the use of polymeric materials. Initially, the thesis presents a study of the ammonia/water absorption-resorption refrigeration cycle by means of thermodynamic models, as well as the analysis of the performance of a 25-kW absorption-resorption refrigeration plant. A test bench was designed and built for the experimental study of the adiabatic ammonia absorption process into ammonia/water solutions. Two different membrane modules were tested: a flat-sheet and a hollow fibre membrane module. In both cases, theoretical models were developed and validated with the experimental results. As a result of the study with the flat-sheet membrane, the characteristics required by a polymeric membrane to be used in the ammonia absorption process were determined. These characteristics were considered for the selection of the commercial hollow fibre membrane module. Finally, a theoretical model of a hollow fibre membrane absorber with heat exchanger integrated was developed. This model was used to design an absorber and a resorber for the 25-kW absorption-resorption refrigeration system. The results obtained confirm the potential in terms of size reduction provided by the membrane modules because heat duties/volume ratio up to 10000 kW/m3 were obtained, much higher than those provided by the plate absorbers (2000 kW/m3) or the shell and tube absorbers (300 kW/m3).
10
Yang, Xin. "DBP formation from chlorination of water containing ammonia, bromide and organic nitrogen /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202004%20YANG.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 100-118). Also available in electronic version. Access restricted to campus users.
11
Determan, Matthew D. "Experimental and Analytical Investigation of Ammonia-Water Desorption in Microchannel Geometries." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7149.
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An experimental and analytical study of a microchannel ammonia-water desorber was conducted in this study. The desorber consists of 5 passes of 16 tube rows each with 27, 1.575 mm outside diameter x 140 mm long tubes per row for a total of 2160 tubes. The desorber is an extremely compact 178 mm x 178 mm x 0.508 m tall component, and is capable of transferring the required heat load (~17.5 kW) for a representative residential heat pump system. Experimental results indicate that the heat duty ranged from 5.37 kW to 17.46 kW and the overall heat transfer coefficient ranges from 388 to 617 W/m2-K. The analytical model predicts temperature, concentration and mass flow rate profiles through the desorber, as well as the effective wetted area of the heat transfer surface. Heat and mass transfer correlations as well as locally measured variations in the heating fluid temperature are used to predict the effective wetted area. The average wetted area of the heat and mass exchanger ranged from 0.25 to 0.69 over the range of conditions tested in this study. Local mass transfer results indicate that water vapor is absorbed into the solution in the upper stages of the desorber leading to higher concentration ammonia vapor and therefore reducing the rectifier cooling capacity required. These experimentally validated results indicate that the microchannel geometry is well suited for use as a desorber. Previous experimental and analytical research has demonstrated the performance of this microchannel geometry as an absorber. Together, these studies show that this compact geometry is suitable for all components in an absorption heat pump, which would enable the increased use of absorption technology in the small capacity heat pump market.
12
Gormican, Stephen Joseph. "Water circulation, dissolved oxygen, and ammonia concentrations in fish-net cages." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27458.
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Fish farming in the protected waters of British Columbia is relatively new, but has undergone a phenomenal growth in the last ten years. Little investigation has been reported with respect to conditions within the net-cages employed in growing salmon at fish farms. In particular, the role of water quality and water exchange has not been examined in relation to local mariculture husbandry practices and hydrography.
The first part of this study compared water quality and water flow in two locations, one in Jervis Inlet with a deep entrance sill and the- other in Sechelt Inlet which has a shallow entrance sill. Marked variations in hydrography occurred between the two sites as a result of the differences in sill depth. An internal wave generated at the Sechelt Inlet sill caused daily fluctuations in stratification and hence water properties within the net-cages. No such variations were observed at the Jervis Inlet site.
In the second part of this study, water quality and water flow was_ measured in various locations in and near a raft of 24 net-cages. Generally, it was found that within the raft, water flow was diminished in those cages located downstream of the predominate flow direction. However, local topography was thought to have caused marked variation in water quality and water exchange patterns in two of the cages.
Ammonia concentrations were not observed to exceed reported sublethal concentrations at any time, over a 25 h period, at any of the depths sampled, within the net-cages. Dissolved oxygen concentrations did, at some depths and times, approach values at which some stress may be felt due to low oxygen.
Linear regressions between water quality and water speed were not found to be significant in most cases. The coefficient of determinations were low, indicating that current speed accounted for less than 27% of the variation in water quality.Science, Faculty of
Zoology, Department of
Graduate
13
Fortes, Andrew. "Computational and experimental studies of solids in the ammonia-water system." Thesis, University College London (University of London), 2004. http://discovery.ucl.ac.uk/83315/.
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This thesis reports the results of first-principles computational studies of thirteen crystalline structures in the H2O-NH3 system. This includes eight low- and highpressure polymorphs of pure water ice, two polymorphs of solid ammonia, and three low-pressure stoichiometric ammonia hydrates. These simulations have been used to determine the athermal equation of state (EoS) of each phase. Where empirical data was lacking, experiments have been undertaken. Hence, this thesis also reports the results of time-of-flight neutron scattering studies of deuterated ammonia dihydrate powders down to 4 K, and up to a maximum pressure of 8.6 GPa. In addition, I have developed a flexible and accurate planetary model that can be used to calculate the triaxial shape and gravitational field of any object, regardless of size or composition, given an assumed mineralogical constitution and provided the EoS of said minerals are known. The EoS parameters found in this work have therefore been used to model the structure and thermal evolution of icy moons orbiting Saturn in anticipation of the Cassini spacecraft arriving at Saturn in mid-2004. Models of Rhea, Saturn’s second largest moon, suggest that its volatile component is likely to contain > 3 weight percent ammonia, but that one is unlikely to be able to constrain the bulk chemistry of the ice mantle from Cassini flyby data.
14
Fneer, Mohamed K. "Development of fibre optic based ammonia sensor for water quality management." Thesis, City University London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363350.
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SPRIGGS, LAURA S. "EXAMINATION OF THE AMMONIA - SULFUR DIOXIDE - WATER SYSTEM USING FTIR SPECTROSCOPY." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1022590722.
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Rieth, Adam J. (Adam Joseph). "Metal-triazolate frameworks for the capture of water vapor and ammonia." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122855.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 93-108).
Metal-organic frameworks (MOFs) are emerging materials for applications in gas sorption and separations, however, they are widely believed to be unstable towards coordinating vapors such as water and ammonia due to often-rapid hydrolysis or substitution at the metal-ligand bond. Here, we describe a series of micro- and mesoporous MOFs constructed from robust metal-triazolate bonds, which, together with a high density of open metal sites, enable these frameworks to exhibit record water uptake as well as record static and dynamic ammonia capacities. Optimization of the pore diameter has led to materials which adsorb large volumes of water with complete reversibility, portending application in the production of potable water in desert regions as well as for heat transfer and storage. Further studies illuminate the mechanism of initial water clustering at and around the metal-centered open coordination sites. For ammonia, systematic variation of the pore size and metal ion lead to materials with a greater affinity and more than twice the capacity for ammonia than activated carbon, the industry standard for protection and mitigation from this toxic and corrosive gas. Structure-function relationships and kinetic analyses of NH₃ and H₂0 uptake in isostructural micro- and mesoporous materials made from Mn, Co, Ni, and Cu reveal stability trends that are in line with the water self-substitution rates in simple metal-aquo complexes. Altogether, these results provide clear, intuitive descriptors that govern the static and dynamic uptake, kinetics, and stability of MOF sorbents for strongly interacting gases.
by Adam J. Rieth.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Chemistry
17
Govindaraju, Sirisha D. "Analysis of absorber operations for the 5 kw ammonia/water combined cycle." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010828.
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Bohra, Lalit Kumar. "Analysis of Binary Fluid Heat and Mass Transfer in Ammonia-Water Absorption." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19780.
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An investigation of binary fluid heat and mass transfer in ammonia-water absorption was conducted. Experiments were conducted on a horizontal-tube falling-film absorber consisting of four columns of six 9.5 mm (3/8 in) nominal OD, 0.292 m (11.5 in) long tubes, installed in an absorption heat pump. Measurements were recorded at both system and local levels within the absorber for a wide range of operating conditions (nominally, desorber solution outlet concentrations of 5 - 40% for three nominal absorber pressures of 150, 345 and 500 kPa, for solution flow rates of 0.019 - 0.034 kg/s.). Local measurements were supplemented by high-speed, high-resolution visualization of the flow over the tube banks. Using the measurements and observations from videos, heat and mass transfer rates, heat and vapor mass transfer coefficients for each test condition were determined at the component and local levels.
For the range of experiments conducted, the overall film heat transfer coefficient varied from 923 to 2857 W/m2-K while the vapor and liquid mass transfer coefficients varied from 0.0026 to 0.25 m/s and from 5.51×10-6 to 3.31×10-5 m/s, respectively. Local measurements and insights from the video frames were used to obtain the contributions of falling-film and droplet modes to the total absorption rates. The local heat transfer coefficients varied from 78 to 6116 W/m2-K, while the local vapor and liquid mass transfer coefficients varied from -0.04 to 2.8 m/s and from -3.59×10-5 (indicating local desorption in some cases) to 8.96×10-5 m/s, respectively. The heat transfer coefficient was found to increase with solution Reynolds number, while the mass transfer coefficient was found to be primarily determined by the vapor and solution properties. Based on the observed trends, correlations were developed to predict heat and mass transfer coefficients valid for the range of experimental conditions tested. These correlations can be used to design horizontal tube falling-film absorbers for ammonia-water absorption systems.
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Delahanty, Jared Carpenter. "Desorption of ammonia-water mixtures in microscale geometries for miniaturized absorption systems." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54389.
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A study of ammonia-water desorption in compact counter-flow geometries was conducted. Two novel vapor generation units, comprising integrated desorber, analyzer, and rectifier segments that use microchannel geometries, were conceptualized. The branched-tray concept features a desorber segment that uses predominantly pool-boiling mechanisms for desorption, while the vertical column desorber relies on falling-film evaporation and boiling mechanisms. Both concepts rely on falling-film heat and mass transfer mechanisms in the analyzer and rectifier sections. Segmented heat and mass transfer models, based on available correlations and modeling methodologies, were developed and used for the design of branched tray and vertical column test sections. An experimental facility was designed and constructed to evaluate desorption and rectification heat and mass transfer processes within these components, under realistic operating conditions. Data were analyzed to determine the boiling/evaporation (desorber) and condensation (rectifier) heat transfer coefficients, and to determine values of the desorber liquid and vapor mass transfer coefficients. Additionally, high-speed video and images were used to gain insights into the hydrodynamic phenomena and heat transfer mechanisms in these vapor generation units. Results of the heat and mass transfer analysis were compared with the predictions of correlations and modeling methods in the literature. The vapor generation unit (VGU) test sections were evaluated across a range of concentrated solution mass fractions (0.400 – 0.550), desorber coupling-fluid inlet temperatures (170 – 190ᵒC), and concentrated solution flow rates (0.70 – 1.3 g s-1). Flow rates in this range correspond to desorber liquid Reynolds numbers of approximately 175 to 410 for the branched tray design, and desorber film Reynolds numbers of approximately 90 to 215 for the vertical column. Pressures observed within the VGU test sections ranged from approximately 1620 to 2840 kPa during testing. The novel VGUs were shown to achieve ideal cooling capacities as high as 432 and 323 W for the branched tray and vertical column, respectively. This parameter indicates the cooling capacity that would be achieved by an idealized cooling system using the refrigerant stream produced by the experimental VGU. Ideal COPs of 0.561 and 0.496 were demonstrated for the branched tray and vertical column, respectively. Experimental heat transfer coefficients were found to range from approximately 1860 to 11690 W m-2 K-1 for the pool-boiling desorption of the branched tray VGU. A new correlation was proposed and shown to provide good agreement with the data, achieving average and average absolute deviation of -5.2 and 16.1%, respectively, across the range of conditions tested. Falling-film evaporation/boiling heat transfer coefficients, determined for the desorption process in the vertical column VGU, were found to range from approximately 1290 to 4310 W m-2 K-1. Rectifier condensation heat transfer coefficients ranging from approximately 160 to 250 W m-2 K-1 were observed. Mass transfer coefficients for the desorbers of both concepts were also quantified. These results were used to develop revised heat and mass transfer models of the VGU concepts. The revised models were demonstrated to predict component-level performance with reasonable accuracy, and may be used in the design of future compact VGUs with similar geometries and operating conditions.
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Al-Ameeri, A.-A. "Protein intake, ammonia excretion and growth of Oreochromis spilurus in sea water." Thesis, University of Stirling, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233795.
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Vanfleteren, Thomas. "HIGH-RESOLUTION NEAR-INFRARED LASER SPECTROSCOPY OF AMMONIA- AND WATER-CONTAINING MOLECULAR COMPLEXES." Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/258689.
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La caractérisation des complexes de van der Waals est déterminante pour la compréhension et la modélisation des atmosphères planétaires et du milieu interstellaire. Cependant, ces agrégats moléculaires sont assez peu étudiés, particulièrement dans l’infrarouge proche. Cette thèse a pour but d’enrichir les connaissances sur les complexes d’eau et d’ammoniac dans cette région spectrale. Pour cela, nous avons utilisé un montage expérimental appellé FANTASIO+, couplant une expansion su- personique à un spectromètre à temps de déclin (CRDS). Plusieurs complexes de van der Waals ont pu être observés et analysés, à savoir 14/15NH3−Ar/Kr, (H2O)2, H2O−Ar/Kr et HDO−N2O.Ces complexes peuvent être décrits par deux régimes selon la hauteur de la barrière du potentiel intermoléculaire. Les complexes caractérisés par un potentiel inter- moléculaire élevé peuvent être traités par le régime semi-rigide, à savoir comme une molécule à part entière avec des constantes rotationelles bien définies [(H2O)2 et HDO−N2O]. Dans le régime du rotateur libre, au contraire, le monomère du complexe est soumis à une faible barrière de potentiel, et donc sa rotation est pra- tiquement libre (tous les complexes 14/15NH3− et H2O−gaz rare).Le déplacement et la séparation des niveaux d’énergie robivrationels du monomère dépend de l’effet de l’anisotropie du potentiel intermoléculaire par rapport au lien intermoléculaire. Les transitions entre ces sous-états sont appelées des sous-bandes.Les spectres observés dans ce travail de thèse correspondent à l’excitation vibra- tionnelle de 14/15NH3, H2O ou HDO. L’analyse rotationelle des sous-bandes a pu être réalisée pour toutes les espèces (y compris les 4 isotopes principaux du krypton dans H2O−Kr), excepté pour 15NH3−Kr car la sous-bande observée était à peine visible. Nous avons pu caractériser la structure rotationnelle de 1 (15NH3−Ar) à 14 (H2O−Ar) sous-états vibrationnellement excités et de l’état fondamental pour toutes les espèces sauf 14NH3−Kr, 15NH3−Ar/Kr et (H2O)2. Notre travail sur ce dernier, basé sur des calculs théoriques et sur une étude similaire en matrice de néon, est la première analyse rotationelle de ce complexe dans cette région spectrale. Les analyses des spectres de H2O−Ar et HDO−N2O s’appuient sur des calculs ab initio. Pour HDO−N2O, nous avons pu déterminer que le lien OD se trouve plus proche de N2O que le lien OH. Les spectres de 14/15NH3−Ar/Kr présentent des sous-bandes appartenant à des complexes de taille plus importante. Un séjour à l’Université d’Alberta a été organisé afin d’identifier la nature de ces complexes.Quand l’analyse rotationelle a pu être réalisée, nous avons déterminé les temps de vie de prédissociation des sous-états excités (sauf pour HDO−N2O car le signal-sur- bruit était trop faible). Ils sont de 20 ps pour (H2O)2 à 4 ns pour H2O−Ar. Nous avons observé que les temps de vie déterminés étaient inversement proportionnels à l’énergie de dissociation des complexes. Le déplacement observé entre l’origine des sous-bandes par rapport à la bande correspondante du monomère suit égale- ment la même tendance que l’énergie de dissociation du complexe. Nous avons pu déterminer les températures rotationnelles pour toutes les espèces dans le jet super- sonique. Celles-ci sont différentes uniquement dans le cas de 14NH3−Ar.Des spectres des monomères 14NH3 et 15NH3 ont également été enregistrés, notamment en utilisant un spectromètre à transformée de Fourier, enrichissant ainsi les données spectroscopiques de ces molécules dans l’infrarouge proche.Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Rees, D. G. "Activity and thermostability of L-phenylalanine ammonia-lyase in water and organic solvents." Thesis, Swansea University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638629.
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L-phenylalanine ammonia-lyase (EC:4,3,1,5), (PAL), catalyses the non-oxidative deamination of L-phenylalanine to trans-cinnamic acid and ammonia. PAL from the red basidiomycetous yeast Rhodosporidium toruloides NCYC 819 was studied with the ultimate aim of examining enzyme properties in water immiscible organic solvents. This is the first demonstration of stability and activity of an ammonia-lyase in organic solvents. Reversal of this reaction has received attention as a possible enzymatic route to the commercially important amino acid L-phenylalanine (which is itself a precursor to the artificial sweetener Aspartame). The growth and induction of PAL by R.toruloides in media containing various nutrient combinations was examined especially in relation to the influence of nitrogen sources on PAL induction. PAL is not appreciably induced except under conditions where L-phenylalanine provides the only or best available source of carbon and/or nitrogen. It was found, in contrast to some previous reports that if L-phenylalanine is present in addition to D-glucose and ammonium ions then the enzyme is induced but at a lower level. The enzyme was partially purified from R.toruloides cell extracts using protamine sulphate, ammonium sulphate fractionation, and DEAE-Sephacel column chromatography steps. This resulted in a PAL preparation 10-fold purified over the crude extract with over 35% yield and an estimated purity of at least 60%. This preparation had a pH optimum between 7.9 and 8.5 (typical for this enzyme) and exhibited biphasic kinetics (i.e. a nonlinear Eadie-Hofstee plot) with the resulting Michaelis constants determined as Kmhigh = 1121 μM and K_m^low = 248 μM. The stability to heating of the partially purified PAL preparations in water was examined and half lives of 95 hours at 30oC, 21 hours at 50oC and 1.4 min at 70oC were obtained. The rate of inactivation at 60oC was found to depend markedly on the pH of the PAL solution with stability falling sharply either side of the range 5.5 to 7.0.
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Helling, Richard K. "Oxidation kinetics of simple compounds in supercritical water : carbon monoxide, ammonia and ethanol." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/14882.
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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE
Vita.
Includes bibliographies.
by Richard K. Helling.
Sc.D.
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Ploeger, Jason M. "Co-oxidation in supercritical water : methylphosphonic acid-ethanol and ammonia-ethanol model systems." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35518.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references.
Supercritical water (SCW) is an effective solvent for the destruction of organic compounds by oxidation. Because both organics and oxygen have high solubility in water above its critical point (To = 374 °C (647 K), Pc = 221 bar), they can be reacted together in a single phase which avoids mass transfer limitations. At typical operating conditions (T= 450 to 650 °C, P = 240 to 300 bar) for supercritical water oxidation (SCWO), H-C-N compounds are rapidly and completely oxidized to water, carbon dioxide, nitrogen, and nitrous oxide. The destruction of organic compounds in SCWO takes place primarily through free radical pathways rather than the ionic pathways that dominate in liquid water. This is because SCW acts as a nonpolar solvent with a dielectric constant ranging from 1.2 at T= 650 °C and P = 250 bar to 2.5 at T= 450 °C and P = 250 bar as compared to ambient water which has a dielectric constant equal to 80. The ion product of water, K, similarly drops to between 10-8 and 102° over this temperature range as compared to the ambient value of 10-14. Typically, SCWO has been studied by the analysis of either the oxidation of single model compounds to determine detailed kinetic mechanisms or by the oxidation of complex simulated waste streams to measure DRE levels.
(cont.) While kinetic rates and mechanisms are accurately determined by the analysis of pure compounds, this approach fails to characterize the co-oxidation effect: a phenomenon observed in mixed waste streams where refractory compounds oxidize more rapidly in the presence of labile compounds. The purpose of this research is to provide a quantitative mechanistic understanding of co-oxidation rate enhancement in supercritical water. This understanding is vital for the application of predictive elementary reaction rate models developed for individual model compounds to the analysis of mixed waste streams. By combining the two well-characterized, validated SCWO models for ethanol and MPA, mechanistic insight into the interaction of the two compounds in SCW is possible. This insight into the mechanism of co-oxidation could then be used to assist in the development and validation of an elementary reaction rate mechanism for ammonia.
(cont.) The co-oxidative effect of ethanol on methylphosphonic acid (MPA, or PO(OH)2CH3) was characterized for a range of MPA concentrations (0.1 to 1.0 mM) and ethanol concentrations (0 to 2.4 mM) for temperatures of 473 °C and 528 °C, a pressure of 245 bar, and stoichiometric oxygen for the complete combustion of both organic compounds. Low concentrations of ethanol (0.1 and 0.3 mM) were found to have no statistically significant effect on MPA conversion for an initial MPA concentration of 1.0 mM, but higher concentrations of ethanol caused an increase in the conversion of MPA at T= 473 °C, P = 245 bar, and r = 9 s from 14±2% without ethanol present to 29-2% with 1.0 mM ethanol and 39±2% with 2.4 mM ethanol. The increase in MPA conversion was more pronounced at shorter residence times. Decreasing the initial concentration of MPA at a constant initial ethanol concentration of 1.0 mM, T= 473 C, P = 245 bar, and = 9 s resulted in an increase in MPA conversion from 29±2% at 1.0 mM MPA to 41±2% at 0.1 mM MPA. At T = 528 C and P = 245 bar, the initial concentration of MPA had a much greater effect on MPA conversion than the initial concentration of ethanol.
(cont.) A supercritical water co-oxidation elementary reaction rate mechanism was constructed from submechanisms for MPA and ethanol with updated kinetic rate parameters for H202 and HOCO' chemistry. The co-oxidation mechanism accurately reproduces the experimentally observed conversion trend of the refractory MPA component as a function of initial concentration of the labile ethanol component. The increase in MPA conversion with increasing ethanol concentration is predicted to be caused by the increased concentration of hydroperoxy radicals (HO2') produced by ethanol oxidation. An analysis of the major organophosphorus reaction fluxes indicated that the co-oxidative effect would increase the conversion of MPA but not change the rate of formation of methane. An experiment using a model formaldehyde/methanol mixture as a co-oxidant was conducted to confirm this prediction.
(cont.) The co-oxidative effect of ethanol on ammonia oxidation in supercritical water was studied for a range of temperatures (655-705 C), initial ammonia (1 to 3 mM), ethanol (0 to 1.0 mM), and oxygen concentrations (0.7 to 5.0 mM), corresponding to fuel equivalence ratios ranging from 0.9 to 2.2. With a stoichiometric amount of oxygen available for complete oxidation, the addition of ethanol on an equivalent molar basis was found to increase ammonia conversion from 20% to 65% at initial concentrations of 1 mM for each reactant, T= 700C, P 246 bar, and X = 2.5 s. Nitrous oxide was produced in much larger quantities for ammonia-ethanol co-oxidation than for ammonia oxidation. Based on fractional yields of nitrogen product, this amounted to 40 to 75% for co-oxidation with ethanol versus 4 to 13% without ethanol present. A co-oxidation model was constructed from submechanisms for ammonia combustion at atmospheric pressure conditions and ethanol oxidation in supercritical water. The initial mechanism poorly reproduced experimental ammonia conversion data and was not able to consistently match nitrous oxide production as a function of temperature over a range from 655 to 700 C. In order to improve model predictions, the low-pressure NH2+NOx submechanism was replaced with a submechanism that included the H2NNOx adduct species that are expected to be stabilized in the high-pressure supercritical water environment. Thermochemical and kinetic parameters for the adduct species were estimated with quantum chemical calculations using Gaussian 98 with the CBS-Q method. The explicit treatment of the H2NNOx adducts resulted in nitrous oxide yield predictions that correctly reproduced experimental trends.
(cont.) In order to improve model predictions, the low-pressure NH2+NOx submechanism was replaced with a submechanism that included the H2NNOx adduct species that are expected to be stabilized in the high-pressure supercritical water environment. Thermochemical and kinetic parameters for the adduct species were estimated with quantum chemical calculations using Gaussian 98 with the CBS-Q method. The explicit treatment of the H2NNOx adducts resulted in nitrous oxide yield predictions that correctly reproduced experimental trends.
by Jason M. Ploeger.
Ph.D.
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Shamblin, Michael D. "Evaluating runoff water quality and ammonia volatilization in three turkey litter application methods." Morgantown, W. Va. : [West Virginia University Libraries], 2002. http://etd.wvu.edu/templates/showETD.cfm?recnum=2668.
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Thesis (M.S.)--West Virginia University, 2002.Title from document title page. Document formatted into pages; contains vii, 59 p. : ill. Includes abstract. Includes bibliographical references (p. 43-45).
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Li, Tianling. "Field-based Sensing Techniques for Real-time Monitoring Wastewater Quality and Free Ammonia." Thesis, Griffith University, 2016. http://hdl.handle.net/10072/367900.
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Recent years, global “water crisis” i.e. freshwater shortage and water pollution has seriously hindered the development of economy and human society, and subsequently aroused the environmental and public health concerns. This work attempts to address these issues by the development of two types of field-based sensing techniques, including on-line monitoring of wastewater quality and in-situ real-time sensing of free ammonia.
On the one hand, in order to alleviate the global freshwater shortage, the purified recycled water (PRW), a product regenerated from recycled water, has been considered as an effective alternative water source. In this PRW production process, wastewater is considered as the source water, the effective and reliable wastewater source management tool is therefore required to mitigate potential health risks and safeguard PRW operation. For this purpose, a wastewater quality monitoring system (WQMS) is developed. It employs a wall-jet flow cell embedded with three pairs of specially configured temperature, conductivity and turbidity sensors and a U-shaped flow cell with a pair of incorporated pH sensors.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Kwok, Wing-hin Kevin Patrick. "On the derivation of Water and Sediment Quality Guidelines : some pressing issues and their resolutions /." Click to view the E-thesis via HKUTO Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B2181963.
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Erdogan, Rezan. "A Quantum Chemical Study Of Water And Ammonia Adsorption Mechanisms On Titanium Dioxide Surfaces." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611522/index.pdf.
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Theoretical methods can be used to describe surface chemical reactions in detail and with sufficient accuracy. Advances, especially in density functional theory (DFT) method, enable to compare computational results with experiments.
Quantum chemical calculations employing ONIOM DFT/B3LYP/6-31G**-MM/UFF cluster method provided in Gaussian 03 are conducted to investigate water adsorption on rutile (110), and water and ammonia adsorption on anatase (001) surfaces of titanium dioxide. Water and ammonia adsorption on anatase (001) surface is studied by also performing PW:DFT-GGA-PW91 periodic DFT method by using VASP code and the results are compared with the results of ONIOM method.
The results obtained by means of ONIOM method indicate that dissociative water adsorption on rutile (110) surface is not favorable due to high activation barrier, whereas on anatase (001) surface, it is favorable since molecular and dissociative water adsorption energies are calculated to be -23.9 kcal/mol and -58.12 kcal/mol. Moreover, on anatase (001) surface, dissociative ammonia adsorption is found energetically more favorable than molecular one (-37.17 kcal/mol vs. -23.28 kcal/mol). Thermodynamic functions at specific experimental temperatures for water and ammonia adsorption reactions on anatase (001) surface are also evaluated.
The results obtained using periodic DFT method concerning water adsorption on anatase (001) surface indicate that dissociative adsorption is more favorable than molecular one (-32.28 kcal/mol vs. -14.62 kcal/mol) as in ONIOM method. On the same surface molecular ammonia adsorption energy is computed as -25.44 kcal/mol.
The vibration frequencies are also computed for optimized geometries of adsorbed molecules. Finally, computed adsorption energy and vibration frequency values are found comparable with the values reported in literature.
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Casey, Lee S. "Kinetic rate constants for the formation of trihalomethanes in chlorinated ammonia containing ground water." FIU Digital Commons, 1985. http://digitalcommons.fiu.edu/etd/2026.
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It is well established that trihalomethanes, in drinking water are byproducts of chlorine disinfection. A method to predict the distribution and concentration of trihalornethanes is important because of health risks associated with chronic exposure to these compounds. A literature review has provided information on the chemistry of water chlorination and a data base developed in the laboratory has provided data on trihalomethane formation under various conditions. These data were used to generate rate constants for the formation of trihalomethanes.
Trihalornethane formation kinetics appeared to be influenced primarily by the presence of ammonia. The influence of pH is not as profound as indicated in literature. The rate of formation is low at and before breakpoint, whereas it increases after breakpoint.
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van, den Akker Ben, and ben vandenakker@flinders edu au. "Removal of ammonia from drinking water by biological nitrification in a fixed film reactor." Flinders University. Medicine, 2008. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20090623.160149.
Full textAbstract:
The absence of water catchment protection often results in contamination of drinking water supplies. Waters in South East Asia have been exploited to support extensive agriculture, industry, power generation, public water supply, fisheries and recreation use. Ammonia has been identified as a significant contaminant of drinking water because of its ability to affect the disinfection efficiency of chlorine. The interference of ammonia with chlorination is a prevalent and expensive problem faced by many water treatment plants (WTPs) located throughout South East Asia. The conventional approach for ammonia removal was to pre-chlorinate using high concentrations of chlorine, which has a number of disadvantages including the formation of disinfection by-products and high chlorine consumption.
This thesis investigated the application of high rate nitrifying trickling filters (NTFs) as a means of ammonia removal from a polluted lowland water source as an alternative to pre-chlorination. NTFs are widely used for the biological remediation of ammonia rich wastewater, however their performance when required to operate under low ammonia concentrations for potable water applications was unknown.
A NTF pilot facility consisting of one large-scale, and three small-scale NTFs were constructed at Hope Valley WTP in South Australia. The NTFs were operated to simulate the raw water quality of a polluted catchment identified in Indonesia (Buaran WTP), including variations in ammonia, biological oxygen demand (BOD5), and turbidity. Results confirmed that plastic-packed NTFs were able to operate equally successfully under low ammonia-N concentrations, some 10- to 50-fold lower that that of conventional wastewater applications, where complete conversion of ammonia to nitrate was consistently observed under these markedly reduced loadings. Results also showed that when operated under mass loads equivalent to typical ammonia loading criteria for wastewater NTFs, by increasing hydraulic flow¬, comparable apparent nitrification rates were achieved. These results confirmed that mass transport limitations posed by low ammonia-N concentrations on overall filter performance were insignificant.
This thesis also investigated the impact of organic carbon quantity and biodegradability on the nitrification behaviour of the pilot NTF. Results demonstrated that organic carbon loading, rather than the C:N ratio, was an important regulator of filter nitrification capacity, where a linear decline in nitrification performance correlated well with sucrose and methanol augmented carbon loads. Extensive monitoring of inorganic nitrogen species down the NTF, to profile nitrification behaviour, showed sucrose-induced carbon loads greater than 870 mg sBOD5 m2 d1 severely suppressed nitrification throughout the entire filter bed. This study also confirmed that critical carbon loads for nitrification varied among carbon sources. In contrast to sucrose, when a more native-like carbon source was dosed (organic fertiliser), no significant decline in nitrification capacity was observed. This could be attributed to differences in carbon biodegradability.
This research has provided new insights into the microbial ecology of a potable water NTF. The combination of fluorescent in situ hybridisation (FISH) and scanning electron microscopy (SEM) for in situ analysis of biofilms was successful in identifying the spatial distribution of ammonia oxidising bacteria (AOB), nitrite oxidising bacteria (NOB) and heterotrophs. When the NTF was operated under low organic loads, clusters of AOB and NOB were abundant, and were located in close proximity to each other. Uniquely, the study identified not only Nitrospira spp but also the less common Nitrobacter spp within the NTF biofilm. Biofilm analysis showed that the type of carbon source also strongly influenced the biofilms characteristics in terms of biomass ecology, morphology, and polysaccharide composition, which was correlated with NTF performance. Results showed that an increase in sBOD5 via the addition of sucrose promoted the rapid growth of filamentous heterotrophic bacteria and production of large amounts of polysaccharide. Stratification of nitrifiers and heterotrophs, and high biofilm polysaccharide concentrations were observed at all filter bed depths, which coincided with the impediment of nitrification throughout the entire filter column. High biofilm polysaccharide concentrations also coincided with a significant increase (40 %) in filter hydraulic retention time, as determined by hydraulic tracer experiments. In contrast to sucrose-fed biofilms, organic fertiliser-fed biofilms had a more uniform and dense ultra-structure dominated by many rod shaped bacteria, and was significantly lower in polysaccharide composition. This observation was coupled with superior nitrification performance.
This study confirmed that a well functioning NTF is a viable, low cost alternative for ammonia removal from source water abstracted from poorly protected catchments found in many developing countries. Pre-treatment using NTFs has the potential to reduce the chlorine dose required for pre-chlorination. Thereby improving water quality by minimising the formation of disinfection by-products, and improving the control of chlorination. NTFs could also find ready application in other situations where ammonia interferes with chlorine disinfection.
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Staß, Ingeborg [Verfasser]. "Atomic-scale structure and surface reactions of water and ammonia on ruthenium / Ingeborg Staß." Berlin : Freie Universität Berlin, 2010. http://d-nb.info/1024866343/34.
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Miladinovic, Natalija D. "Biological interactions during ion exchange removal of ammonia from terrestrial and marine waste water." Thesis, University of Canterbury. Chemical and Process Engineering, 2005. http://hdl.handle.net/10092/7514.
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Wastewater containing ammonia is a product of oil refineries, coal gasification plants, slaughterhouses, dairy plants, distilleries, fertilizer plants and pharmaceutical operations; ammonia is also found in municipal wastewater. The ammonia is toxic to living organisms and it is desirable that it be removed. The foremost aim of this research was to use biologically activated ion exchange materials for ammonia removal from wastewater.
In the past sand, plastic media and activated carbon as well as some ion exchange materials, e.g., clinoptilolite, have been used like a solid surface for bacteria growth. In this work some other materials were used for a combined biological and ion exchange process. The materials used were mordenite and Macronet MN 500 for terrestrial water, and modified zeolites for selective uptake of ammonia from marine waters. Clinoptilolite was used for comparison, as an ion exchanger which previously has been biologically activated.
The ammonia adsorption characteristics of the materials in saline and non-saline synthetic wastewater were determined and compared with literature data. The data was fitted using Langmuir and Freundlich isotherms. The effect of the individual presence of potassium, calcium and magnesium ion upon ammonium ion uptake onto each material was also investigated.
Bench scale ion-exchange stirred cell experiments were conducted to assess the uptake kinetics of ammonium ion. Process parameters include: initial ammonia concentration, the agitation rate, material particle size and mass of the material. The suitability of the ion exchange materials as a support for the growth of nitrifying bacteria was determined by observing the nitrification process in the flasks containing different materials, for the fresh and saline media. The ion exchangers were tested in continuous columns initially without bacterial growth and later with. To overcome the problem of low oxygen levels in the column and to avoid over aeration of the system, a novel design of columns was introduced, where aeration through the column was achieved by the air permeable silicon tubing.
The synthetic material MN 500 exhibited the highest uptake capacity but the natural zeolites had the highest preference for ammonium ions in the presence of interfering cations. The ion exchange materials removed ammonia from saline water. A product of zeolitic nature, ZZ, exhibited the highest uptake capacity for ammonia removal from saline water. Natural zeolites were shown to be better media for bacterial growth in non-saline water. MN 500 exhibited better ammonia removal performance for the combined process in sea water compared to modified zeolite, ZZ. Both the clinoptilolite and mordenite used in non-saline medium, exhibited higher uptake capacity during the column experiments than for batch experiments.
By introducing bacteria into the column, the uptake capacity was increased from the value of 0.15 to the value of 0.22meq/g for clinoptilolite. The improvement for the biologically active mordenite was from the value of 0.30meq/g without bacteria to the value of 0.4 meq/g with bacteria. The aeration of 2.88dm³/h, achieved by the tubing, provided better condition for the nitrification within the column, compared to the commonly used tank pre-aeration at the rate of 180dm³/h. The biologically active ion exchange column was not efficient in removing ammonia from saline water. High salt concentrations and slower nitrification in saline medium interfered the process significantly.
It could be concluded that biologically active ion exchange is acceptable method for ammonia removal from non-saline wastewater. The possible way to improve the efficiency of the process in saline water would be to apply it in wastewaters in with nitrifying bacteria are already established. Mordenite proved to be more adequate for biological activation compared to commonly used clinoptilolite, which indicates that more ion exchange materials should be tested for combined process. The new aeration system within the columns proved to be more efficient compared to the commonly used tank pre-aeration.
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Mwale, Monica. "Ammonia removal from water by ion exchange using South African and Zambian zeolite samples." Thesis, Rhodes University, 2000. http://hdl.handle.net/10962/d1005058.
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One problem of intensive fish culture systems is the progressive build-up of toxic wastes such as ammonia. The possibility of improving aquaculture water quality using two kinds of zeolite is discussed. Zeolites are alumino-silicates whose framework allows them to exchange cations. Ion exchange has been demonstrated to be competitive with other methods of ammonia removal due to the high selectivity for ammonia exhibited by zeolite materials. In this study an unknown Zambian zeolite (identified as laumontite by X-ray diffraction techniques) and Pratley clinoptilolite (a South African zeolite) were tested under laboratory conditions and in a fresh water recirculating system. Ammonia cation exchange capacities (CEC) and suitable application rates for efficient water treatment were determined using the batch and column ion exchange procedures. Estimated ammonia uptake, the most important criterion used to assess performance of zeolite filters was strongly influenced by zeolite type, particle size, pre-treatment, regeneration and ion exchange method used. Statistical analysis showed significant differences in average ammonia CEC values between clinoptilolite (14.94 mg g⁻¹) and laumontite (2.77 mg g⁻¹), with the former displaying a higher Na⁺ ® NH₄⁺ exchange rate especially in the early reaction stages. This difference accords with the higher purity of clinoptilolite, 47% as opposed to 4.7% for laumontite, which makes it a better zeolite for ammonium removal. CEC increased linearly as particle size of the clinoptilolite was reduced resulting in a linear regression model (y = 18.29 – 3.704 x; r² = 74%). Pre-treatment of clinoptilolite using 1N NaCl significantly improved the ammonia CEC of clinoptilolite. Overall performance of both the batch and column methods achieved after regeneration (18.3 mg g⁻¹) was 25% higher than the estimated CEC values (13.0 mg g⁻¹) for the unregenerated samples of clinoptilolite. Comparison of CEC estimates using Pratley clinoptilolite, showed that average batch CEC estimates were significantly lower than the column method estimates. The average ammonia CEC values estimated in a fresh water recirculating system (5.80 mg g⁻¹ and 4.12 mg g⁻¹ for the 0.7-1.0 and 1.0-1.4 mm particle sizes, respectively) were significantly lower than the column and batch estimates for the same particle sizes (P < 0.05). Some nitrite (NO₂) and nitrate (NO3) build up was experienced probably due to the growth of autotrophs in the filters. Mass balance of nitrogen (N) for the three treatments of the fish trial (0.7-1.0 mm, 1.0-1.4 mm and the control treatment that had no zeolite in the filter) indicated that less that 10% of the N was retained for growth. It was found that 60% of the NH₄-N present associated with the soluble N was available for absorption by the zeolite filter or biological nitrification and that a total of approximately 22% of NH₄-N available was absorbed by clinoptilolite. The results indicate that the rate of nitrification can be deductively estimated by allowing a zeolite filter to become a biological filter. It is concluded that water treatment by ion exchange using natural zeolites, provides a reliable and efficient method for ammonia removal and appears to be a viable supplementary water treatment method for fresh water systems.
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Cavazzoni, Carlo. "Large Scale First-Principles Simulations of Water and Ammonia at High Pressure and Temperature." Doctoral thesis, SISSA, 1998. http://hdl.handle.net/20.500.11767/3948.
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Talbot, Krystle. "Zebrafish (Danio rerio) Aquaporin 1a as a Multi-functional Transporter of Water, CO2, and Ammonia." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31076.
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Previous in vitro studies have demonstrated that AQP1, traditionally viewed as a water channel, also facilitates the passage of CO2 and ammonia across cell membranes. This thesis summarizes the first in vivo studies confirming a physiologically-relevant role for AQP1 in acid-base balance and nitrogenous waste excretion. Zebrafish embryos were microinjected with a translation-blocking morpholino oligonucleotide targeted to the zebrafish AQP1 paralog, AQP1a. Closed-system respirometry, total CO2 analysis, tritiated water fluxes and measurement of ammonia excretion were performed on larvae at 4 days post-fertilization (dpf). Knockdown of AQP1a significantly reduced rates of water, CO2 and ammonia excretion. Use of phenylhydrazine, a haemolytic agent, provided evidence that the yolk sac epithelium AQP1a (and not erythrocyte AQP1a) is the major site of CO2 and ammonia movements. Further, the hypothesis that AQP1a and the Rh glycoprotein Rhcg1, another multi-functional gas channel, act in concert to regulate CO2 and ammonia excretion was explored. Exposure to conditions impairing ammonia excretion (such as high external ammonia (HEA) or alkaline water) modulated AQP1a protein expression in 4 dpf zebrafish larvae experiencing knockdown of Rhcg1. Chronic HEA exposure triggered a significant compensatory increase in AQP1a protein abundance in Rhcg1 morphants. Exposure of Rhcg1 morphants to pH 10 water, however, caused a significant decrease in AQP1a protein expression. Interestingly, when AQP1a mRNA and protein levels were examined in Rhcg1 morphants and vice versa, no changes were observed. Overall, zebrafish AQP1a was found to be a multi-functional transporter of water, CO2 and ammonia, though the exact relationship it holds with other such gas channels bears further exploration.
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Siddiqui, Shariq. "Optimization of Ammonia-Peroxide Water Mixture (APM) for High Volume Manufacturing through Surface Chemical Investigations." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/201511.
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Ammonia-peroxide mixture (APM) is a widely used wet chemical system for particle removal from silicon surfaces. The conventional APM solution in a volume ratio of 1:1:5 (NH4OH:H2O2:H2O) is employed at elevated temperatures of 70-80 °C. At these temperatures, APM solution etches silicon at a rate of ~3 Å/min, which is unacceptable for current technology node. Additionally, APM solutions are unstable due to the decomposition of hydrogen peroxide and evaporative loss of ammonium hydroxide resulting in the change in APM solution composition. This has generated interest in the use of dilute APM solutions. However, dilution ratios are chosen without any established fundamental relationship between particle-wafer interactions and APM solutions.Atomic force microscopy has been used to measure interaction forces between H-terminated Si surface and Si tip in APM solutions of different compositions. The approach force curves results show attractive forces in DI-water, NH4OH:H2O (1:100) and H2O2:H2O (1:100) solutions at separation distances of less than 10 nm for all immersion times (2, 10 and 60 min) investigated. In the case of dilute APM solutions, the forces are purely repulsive within 2 min of immersion time. During retraction, the adhesion force between Si surface and Si tip was in the range of 0.8 nN to 10.0 nN. In dilute APM solutions, no adhesion force is measured between Si surfaces and repulsive forces dominated at all distances. These results show that even in very dilute APM solutions, repulsive forces exist between Si surface and particle re-deposition can be prevented.The stability of APM solutions has been investigated as a function of temperature (24 - 65 °C), dilution ratio (1:1:5 - 1:2:100), solution pH (8.0 - 9.7) and Fe2+ concentration (0 - 10 ppb) using an optical concentration monitor. The results show that the rate of H2O2 decomposition increased with an increase in temperature, solution pH and Fe2+ concentration. The kinetic analysis showed that the H2O2 decomposition follows a first order kinetics with respect to both H2O2 and OH- concentrations. In the presence of Fe2+, hydrogen peroxide decomposition follows a first order reaction kinetics with respect to H2O2 concentration.
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Ammari, Ali. "Experimental Investigation ofTwo-phase Flow in Microchannels“Co-current Absorption of Ammonia in Water to Design an Innovative Bubble Plate Absorber” : “Co-current Absorption of Ammonia in Water to Design an Innovative Bubble Plate Absorber”." Thesis, KTH, Tillämpad termodynamik och kylteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-116779.
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For ammonia-water absorption refrigeration technology it is suggested to use bubble type absorbers because the higher contact surface area provides a higher mass transfer rate. Furthermore, dispersion of bubbles in the bulk of liquid phase also exhibits better heat transfer characteristics that facilitate the recovery of dissipated heat of the exothermic absorption.In this context, plate heat exchangers are believed to be an option to be employed as absorber in some applications. Commercial plate heat exchangers have only one inlet and outlet for a working fluid and as a result, gas and liquid should be mixed before supplied to a gap between the two adjacent plates. The consequence is the high risk of bubble mergence to form a bigger bubble and to follow the shortest flow paths in vertical direction so that not all the heat transfer surface can be effectively used. Furthermore this feature makes plate heat exchangers sensitive to the angle of plate relative to the vertical which would be worst when it is laid to its side on a horizontal plane.Austrian Institute of Technology (AIT) develops an efficient Bubble Plate Absorber for applications in high-pressure absorption systems and this work tries to investigate design possibility of this Bubble Plate Absorber based on a plate heat exchanger equipped with microchannels between plates.Two sets of seven parallel microchannels same in shape and dimension were tested. The first set had a continuous wall which means fluids could flow independently along the microchannels; whereas, the other set was benefiting from some linkages between channels that fluids could cross from one microchannel to another one. Ammonia vapour was injected via one and two-holed distributors.It was found that microchannels with continuous wall deliver higher concentration and less unabsorbed bubbles at the microchannels outlet. In visual analysis by high-speed camera, changing the vapour distributors from single-hole to double-hole had no significant effect on the bubble distribution quality in lower flowrates; however, double-hole vapour distributor showed better performance in higher vapours flowrates.
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Nordtvedt, Stein Rune. "Experimental and theoretical study of a compression/absorption heat pump with ammonia/water as working fluid." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-5493.
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Nagavarapu, Ananda Krishna. "Binary fluid heat and mass exchange at the microscale in internal and external ammonia-water absorption." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45777.
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Absorption space-conditioning systems are environmentally benign alternatives to vapor compression systems and have the capability of being driven by waste heat. However, a lack of practically feasible and economically viable compact heat and mass exchangers is a major limitation in the success of this technology. The viability of the absorption cycle depends upon the performance of the absorber, which experiences large heat and mass transfer resistances due to adverse temperature and concentration gradients during the phase change of the binary mixture working fluid, resulting in large overall component sizes. Understanding of the coupled heat and mass transfer during binary fluid mixture absorption at the microscales is critical for the miniaturization of these components, which will enable broad implementation of this technology.
The proposed study aims to achieve this by investigating ammonia-water absorption for two distinct flow configurations: external falling films and internal convective flows. For the falling-film absorption case, ammonia-water solution flows around an array of small diameter coolant tubes while absorbing vapor. This absorber is installed in a test facility comprising all components of a single-effect absorption chiller to provide realistic operating conditions at the absorber. Local temperature, pressure, and flow measurements will be taken over a wide range of operating conditions and analyzed to develop a heat and mass transfer model for falling-film ammonia-water absorption. A microscale convective flow absorber will also be investigated. This absorber consists of an array of parallel, aligned alternating shims with integral microscale features, enclosed between cover plates. These microscale features facilitate flow of various fluid streams and the associated heat and mass transfer. The use of microchannels induces high heat and mass transfer rates without any active or passive surface enhancement. The microscale absorber for small-scale applications will be evaluated over a wide range of operating conditions on a single-effect absorption heat pump breadboard test facility. The study will conclude with a comparison of the two flow configurations for absorption, with recommendations for their application in future miniaturization efforts
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Ilchenko, A. O. "Technology development of obtaining high concentration ammonia water and liquid multiple-nutrient fertilizers on its basis." Thesis, Sumy State University, 2017. http://essuir.sumdu.edu.ua/handle/123456789/63230.
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Decreasing of the crop productivity and falling-off in agricultural production make farmers in Ukraine look for a solution from the critical situation. The main factor of increasing productivity and effective land use is applying organic and mineral manure. The use of organic fertilizers is complicated by a sharp reduction in the number of livestock, and thus the number of organics as well. Farmers don’t have enough money to stock up with mineral fertilizers. According to the world experience, using liquid fertilizers is the most technologically and economically advantageous. They provide drastic fertilizer loss reduction, full mechanization of handling operations, high uniform soil fertilization and labor costs reduction.
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Lee, Sangsoo. "Development of techniques for in-situ measurement of heat and mass transfer in ammonia-water absorption systems." Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-07082007-221833/.
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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2008.Ghiaasiaan, S. Mostafa, Committee Member ; Sheldon, M. Jeter, Committee Member ; Fuller, Tom, Committee Member ; Teja, Amyn, Committee Member ; Garimella, Srinivas, Committee Chair.
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Vojvodic, Dragana. "A comparison of ammonia filter methods for the survival and wellbeing of Norway lobster, Nephrops Norvegicus, in water live storage." Thesis, Halmstad University, School of Business and Engineering (SET), 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-917.
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Van, der Walt Stefan. "The design and optimisation of a bubble pump for an aqua-ammonia diffusion absorption heat pump / Stefan van der Walt." Thesis, North-West University, 2012. http://hdl.handle.net/10394/9231.
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Energy shortages around the world necessitated research into alternative energy sources especially for domestic applications to reduce the load on conventional energy sources. This resulted in research done on the possibility of integrating solar energy with an aqua-ammonia diffusion absorption cycle specifically for domestic applications.
The bubble pump can be seen as the heart of the diffusion absorption cycle, since it is responsible, in the absence of a mechanical pump, to circulate the fluid and to desorb the refrigerant (ammonia) from the mixture. It is thus of paramount importance to ensure that the bubble pump is designed efficiently.
Various bubble pump simulation models have been developed over the years, but it was found that none of the existing models served as a good basis for application-specific design. Most of the models constrained too many parameters from the outset which made the investigation of the effects of certain parameters on the bubble pump’s performance impossible. According to the research, no bubble pump model investigated the effect of such a wide variety of factors including tube diameter, heat flux, mass flux, generator heat input and system pressure on the bubble pump’s lift height.
A simulation model for a bubble pump for integration with a solar-driven aqua-ammonia diffusion absorption cycle was developed. It serves as a versatile design model to optimise the bubble pump for a large variety of conditions as well as changes in parameters. It was achieved by constraining the bubble pump dimensions and parameters as little as possible. A unique feature of this model was the fact that the bubble pump tube was divided into segments of known quality which made the length of the pipe completely dependent on the flow inside the pipe. It also made the demarcation of the flow development inside the tube easier.
The model attempted to incorporate the most appropriate correlations for pressurised two-phase aqua-ammonia flow. The most appropriate void fraction correlation was found to be Abstract
The design and optimisation of a bubble pump for an aqua-ammonia diffusion absorption heat pump the Rouhani-Axelsson (Rouhani I) correlation. It was mainly due to its exclusive use of thermophysical properties and the vapour quality.
The most appropriate heat transfer coefficient that predicted the most realistic wall temperature, was the correlation from Riviera and Best (1999) which was the only correlation found in the literature developed with aqua-ammonia in mind. It was found that the published correlation could not reproduce their experimental results, and a modification of their correlation was made after which the simulation model’s results correlated well with the experimental values of Riviera and Best (1999).
The main goal of the simulation model was to determine the height that the bubble pump was capable of lifting at the slug to churn flow transition under various conditions. The effect of varying a variety of parameters on the bubble pump lift height was also investigated.
The results from Shelton & White Stewart (2002) were compared to the outputs of the simulation model, and it was found that their constraining of the submergence ratio limited their outputs, and that their heat inputs under different conditions was a bit optimistic. The simulation model’s outputs correlated well at higher tube diameters with the results from Shelton & White Stewart (2002), but at the lower diameters which was used in their study it was impossible to compare data, since their diameters was already in mini flow and micro flow regions. The temperatures also correlated well, all within 2% of the results from Shelton & White Stewart (2002).
It was found that there couldn’t be just one set of optimised conditions and values for the bubble pump, but that each cycle with differing specifications and operating conditions would yield a unique set of optimised parameters. It was for that reason very important not to constrain parameters beforehand without investigating its effect on the bubble pump first.Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013.
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A, Monfared Behzad. "Design and Construction of a Small Ammonia Heat Pump." Thesis, KTH, Tillämpad termodynamik och kylteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-64411.
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In view of the fact that most of the synthetic refrigerants, in case of leakage or release, are harmful to the environment by contributing in global warming or depleting stratospheric ozone layer, many research works have been done recently to find alternative refrigerants posing no or negligible threat to the environment. Among alternative refrigerants, ammonia, a natural refrigerant with zero Global Warming Potential (GWP) and Ozone Depletion Potential (ODP), can be a sensible choice.Although ammonia has been used for many years in large industrial systems, its application in small units is rare. In this project a small heat pump with about 7 kW heating capacity at -5 °C and +40 °C evaporation and condensation temperatures is designed and built to work with ammonia as refrigerant. The heat pump is expected to produce enough heat to keep a single-family house warm in Sweden and to provide tap hot water for the house. After successful completion of this project, it is planned to install the heat pump in a house to test it throughout a heating season to study its performance in real working conditions.Since ammonia is flammable and toxic in high concentrations, the refrigerant charge is tried to be kept low in the heat pump to reduce the risk of fire or poisoning in case of unwanted release of refrigerant to the surroundings. The compact design of the heat pump helps reducing the refrigerant charge. Besides, considering the limited space normally reserved for installation of a heat pump in a house, the compact design of the heat pump is necessary.
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Hanley, Thomas Ryan. "The microwave opacity of ammonia and water vapor: application to remote sensing of the atmosphere of Jupiter." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24673.
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Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Committee Chair: Dr. Paul G. Steffes; Committee Member: Dr. Gregory D. Durgin; Committee Member: Dr. Robert D. Braun; Committee Member: Dr. Thomas K. Gaylord; Committee Member: Dr. Waymond R. Scott
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Kleier, Karen. "The Impact of Monochloramine on Ammonia-Oxidizing Bacteria in Lab-Scale Annular Reactors." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1335550245.
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Ennis, Courtney. "Spectroscopic identification of complex species containing water and ammonia and their importance to icy outer solar system bodies." University of Western Australia. Chemistry Discipline Group, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0110.
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[Truncated abstract] This thesis examines the bonding interactions and chemical processes associated with irradiated water (H2O) and ammonia (NH3) molecules. The experiments conducted in the present study are designed to replicate the surface chemistry of outer Solar System bodies, particularly the icy surfaces of Saturn's inner moons. Infrared (IR) spectroscopy is used to identify the H2ONH3 complex isolated in an argon (Ar) matrix. An electric discharge is then applied to the H2O and NH3 species to produce the hydroxyl-ammonia (OHNH3) complex and the water-amidogen (H2ONH2) complex. Finally, the ammonia-oxygen (NH3O2) complex is formed in an Ar matrix, complementing previous studies performed by the Quickenden research group, which investigated the conversion of OH radicals into molecular O2 on icy planetary surfaces. ... An electric discharge is applied to the NH3 in Ar mixture, producing the NH2 radical subunit of the complex. Two absorption bands are assigned to the H2O subunit vibrational frequencies of the complex; at 1616.1 cm-1 for the ¿2 HOH bending fundamental and at 3532.1 cm-1 for the ¿1 OH bonded stretching fundamental. Two absorption bands are also assigned to the NH2 radical subunit vibrational frequencies of the complex; at 1498.5 cm-1 for the ¿2 HNH bending fundamental and at 3260.8 cm-1 for the ¿3 NH asymmetric stretching fundamental. These assignments are verified by the isotope substitution method, involving the formation of the deuterated D2OND2 complex analogue in an Ar matrix and the measurement of the isotope induced shifts in peak position in the IR region. The isotopic shifts displayed by the IR absorption bands are in good agreement with the theoretically calculated shifts in vibration frequency when going from the H2ONH2 complex fundamentals to the D2OND2 complex fundamentals. The theoretical calculations also derived an interaction energy of 5.2 kcal mol-1 for the HOHNH2 structure of the H2ONH2 complex. This HOHNH2 structure is also confirmed as the preferred structure of the H2ONH2 complex in the IR experiments, by the observation of a large shift in position of the absorption band associated with the H2O subunit ¿1 OH stretching fundamental, away from the position of the H2O monomer ¿1 OH stretching fundamental. This indicates that the H2O subunit donates a hydrogen for the complex bond in the HOHNH2 complex. The NH3O2 complex is identified in solid Ar matrices at 10.5 K by IR analysis. The NH3O2 complex is formed by the co-deposition of gaseous NH3 in Ar mixtures with O2 in Ar gas mixtures. An absorption band is assigned to the ¿1 OO stretching fundamental for the O2 subunit of the NH3O2 complex at 1552.0 cm-1. This assignment is verified by the isotope substitution method, involving the formation of the deuterated ND3O2 complex analogue in an Ar matrix and the measurement of the isotope induced shift in peak position in the IR region. The isotopic shift displayed by the IR absorption band is in good agreement with the theoretically calculated shift in vibration frequency when going from the NH3O2 complex fundamental to the ND3O2 complex fundamental. The theoretical calculations also derived an interaction energy of 0.28 kcal mol-1 for the NH3O2 complex.
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Visagie, Pieter Johannes Jacobus. "The analysis of an ammonia/water hybrid heat pump in the ethanol production process / by Pieter J.J. Visagie." Thesis, North-West University, 2008. http://hdl.handle.net/10394/2529.
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Ethanol is a renewable energy source that could decrease society's dependence on fossil fuels, while reducing greenhouse gas emissions. Producing ethanol on a small scale on South African farms could provide farmers with the capability of increasing their profits by reducing their input cost. Ethanol can be directly used as fuel and could supply alternative products to their market.
This study evaluated the feasibility of using an ammonia/water hybrid heat pump in the ethanol production process. A model for the material and energy balance of a small scale ethanol plant was simulated, to obtain the requirements to which the hybrid heat pump had to adhere.
A two stage hybrid heat pump (TSHHP) was then modelled. It is capable of operating at high temperatures and it has high temperature lift capabilities, which are suitable in the production of ethanol. The results from the model demonstrated that the TSHHP could operate at an average temperature lift of 106°C with a maximum temperature of heat delivery as high as 142°C and cooling as low as 9°C. Simultaneous heating and cooling demand in the ethanol production process can be met with the TSHHP. For the TSHHP model, 120 kW of heating and 65 kW of cooling is supplied while maintaining a COP of 2.1. The model accuracy was also verified against another simulation program.
Implementation of the TSHHP into the ethanol plant was then discussed, as well as methods to optimize production by energy management. When compared to conventional heating and cooling systems, it was found that the TSHHP provides a more cost effective and energy efficient way of producing ethanol. The economic evaluation demonstrated that the installation cost of the TSHHP would only be 63% of the price of a conventional system. The main advantage is that the TSHHP uses only 38% of the energy used in a conventional system.Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2009.
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Hörter, Melanie. "Influence of ammonia and water sorption on the chemical and electrochemical properties of polyacrylic acid and its derivates." [S.l. : s.n.], 2008.
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Kilberg, Brianna. "Aqua Ammonia as Secondary Fluid in Ice Rink Applications." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-281954.
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Refrigerant management is crucial in the attempts to slow climate change. Emissions from the refrigeration sector are primarily due to poor management and unsafe destruction of refrigerants currently in circulation. Safe refrigerant management and improving system operating efficiency can result in a reduction of emissions. Ice rinks are some of the most energy-intensive public buildings, providing both heating and cooling. The major share of energy in an ice rink is the refrigeration system, which consumes about 43%. There are more than 360 ice rinks in Sweden as of 2018 and the most common type of refrigeration system is an indirect system. With the push for natural fluids, aqua ammonia is becoming a more appealing option as a secondary fluid in ice rinks because of its minimal negative impact on the environment and favorable thermophysical properties. The main drawbacks of the fluid are its toxic characteristics and material compatibility. However, since the first use in 2007, there has been an increase to 34 of the total ice rinks in Sweden that have aqua ammonia as a secondary fluid. Thermophysical properties are used to calculate refrigeration design parameters, including secondary fluid concentration and pumping power required. The properties of aqua ammonia have not been experimentally tested within this century to the extent presented in this thesis. Existing data is either derived from measured values taken several decades ago or has been calculated. The novelty of this thesis project stems from the unique and more accurate results measured through laboratory work and from the ability to determine the impact of the newly measured values in ice rink refrigeration design. A total of 11 varying concentrations of aqua ammonia were tested for density, dynamic viscosity, specific heat capacity, thermal conductivity, and corrosion of 7 metal specimens. The solutions tested ranged from 2 wt-% to 30 wt-%, correlating to freezing points from -2C to -84C. The measurements for density resulted in values similar to reference values, ranging in a difference of only 0.3% to 1.7%. Dynamic viscosity results followed nearly the same trend as references with changing temperature and solution concentration, with values varying from 0.8% to 17% different than references. Specific heat capacity measurements proved significantly different than reference values. The trend is opposite of the reference, leading to drastically different values, especially at lower temperatures and higher solution concentrations. The difference in values ranges from 0.1% to 28%. Thermal conductivity results show similar trends, but higher values than expected. The difference between measured values and reference values range from 0.1% to 13%. Corrosion results show that copper and brass have the highest corrosion rates of 16.2 mm/yr and 1.84 mm/yr, respectively. The most compatible specimen was stainless steel, followed by carbon steel, with maximum corrosion rates of 0.041 mm/yr and 0.11 mm/yr, respectively. Brass connections commonly used in industry were also tested and resulted in corrosion rates ranging from 69.6 g/yr to 112 g/yr, which accounts for about 1% and 1.5% of the connections’ total weight lost per year. Compiling the laboratory measurements taken during the completion of this thesis project results in a more complete and accurate list of thermophysical properties for aqua ammonia that has never existed before. These updated thermophysical properties for aqua ammonia, along with measured properties for other secondary fluids, were used to calculate operational parameters in a hypothetical ice rink refrigeration system. The results show that aqua ammonia is favorable with high COP and low pumping power, and therefore low pressure drop. Ammonia is most comparable to CaCl2 and K-formate for most results. The changes in calculated COP between old reference data and new measured data were less than a 1% decrease when plotting versus the temperature of the ice surface and with a set pump control (T) for cooling capacities of 200kW and 300kW. The change in heat transfer coefficients was more significant, with a range of about a 9% to 27% decrease in either the U-pipe under the rink floor or in a plate of the heat exchanger. Even though these heat transfer coefficient values are lower than previously calculated, the required pumping power is also lower using updated properties: 40% lower at a secondary fluid temperature of -10C. Even though the change in heat transfer coefficients is larger with experimental values, the impact on COP is minimal. The takeaway from this project is that aqua ammonia is a favorable secondary fluid compared to calcium chloride and ethylene glycol, the two most commonly used secondary fluids in ice rink refrigeration. A system using aqua ammonia would have a 45% and 47% lower pumping power requirement compared to calcium chloride and ethylene glycol, respectively. The system would also have a 4.7% and 11.6% higher COP when compared to systems with calcium chloride and ethylene glycol, respectively. The significantly lower pumping power will lower total energy demand of the ice rink, thus decreasing operation costs.Köldmediehantering är avgörande i försöken att sakta ner klimatförändringen. Utsläppen från kylsektorn beror främst på dålig hantering och osäker destruktion av köldmedier som för närvarande är i omlopp. Säkrare hantering av köldmedium och förbättrad systemdriftseffektivitet kan leda till ett minskat utsläpp. Ishallar är några av de mest energiintensiva offentliga byggnaderna som ger både uppvärmning och kylning. Den största andelen energi i en ishall är kylsystemet som förbrukar cirka 43%. Det finns mer än 360 isbanor i Sverige från och med 2018 och den vanligaste typen av kylsystem är ett indirekt system. Med trycket på naturliga vätskor blir ammoniakvatten ett mer tilltalande alternativ som en köldbärare i ishallar på grund av dess minimala negativa påverkan på miljön och gynnsamma termofysikaliska egenskaper. Köldbärares främsta nackdelar är dess toxiska karaktär och materialkompatibilitet. Sedan den första användningen 2007 har det dock skett en ökning till 34 av de totala ishallar i Sverige som har ammoniakvatten som köldbärare. Termofysikaliska egenskaper används för att beräkna parametrar för kyldesign, inklusive köldbärares koncentration och pumpeffekten som krävs. Ammoniakvattens egenskaper har inte testats experimentellt under detta sekel i den utsträckning som presenteras i detta exjobb. Befintliga data härleds antingen från uppmätta värden som tagits för flera decennier sedan eller har beräknats. Nyheten härrör i detta exjobbsprojekt från de unika och mer exakta resultat som mätts genom laboratoriearbetet och från förmågan att bestämma effekten av de nyligen uppmätta värdena i kylskåpsdesign. Totalt 11 olika koncentrationer av ammoniakvatten testades med avseende på densitet, dynamisk viskositet, specifik värmekapacitet, värmeledningsförmåga och korrosion av 7 metallprover. De testade lösningarna varierade från 2 vikt-% till 30 vikt-%, korrelerade med fryspunkter från -2 ° C till -84 ° C. Mätningarna för densitet resulterade i värden som liknar referensvärdena, med en skillnad på endast 0,3% till 1,7%. Dynamiska viskositetsresultat följde nästan samma trend som referenser med förändrad temperatur och lösningskoncentration, med värden som varierade från 0,8% till 17% annorlunda än referenser. Specifika värmekapacitetsmätningar visade sig vara väsentligt annorlunda än referensvärden. Trenden är motsatt referensen, vilket leder till drastiskt olika värden, särskilt vid lägre temperaturer och högre koncentrationer. Skillnaden i värden varierar från 0,1% till 28%. Värmeledningsförmåga visar liknande trender, men högre värden än förväntat. Skillnaden mellan uppmätta värden och referensvärden sträcker sig från 0,1% till 13%. Korrosionsresultat visar att koppar och mässing har de högsta korrosionshastigheterna på 16,2 mm / år respektive 1,84 mm / år. Det mest kompatibla exemplet var rostfritt stål, följt av kolstål, med maximala korrosionshastigheter på 0,041 mm / år respektive 0,11 mm / år. Mässinganslutningar som vanligen används i industrin testades också och resulterade i korrosionshastigheter från 69,6 g / år till 112 g / år, vilket motsvarar för cirka 1% och 1,5% av anslutningarnas totala viktförlust per år. Att sammanställa laboratoriemätningarna som gjorts under slutförandet av detta projekt resulterar i en mer fullständig och noggrann lista över termofysikaliska egenskaper för ammoniakvatten som aldrig funnits tidigare. Dessa uppdaterade termofysikaliska egenskaper för ammoniakvatten, tillsammans med uppmätta egenskaper för andra köldbärare, användes för att beräkna driftsparametrar i ett hypotetiskt kylsystem. Resultaten visar att ammoniakvatten är gynnsam med hög COP och en låg pumpeffekt och därmed ett lågt tryckfall. Ammoniakvatten är mest jämförbart med CaCl2 och K-formiat för de flesta resultat. Förändringarna i beräknad COP mellan gamla referensdata och nya uppmätta data var mindre än 1% minskning vid planering jämfört med isytans temperatur och med en inställd pumpkontroll (T ) för kylkapacitet på 200 kW och 300 kW. Förändringen i värmeövergångstal var mer signifikant, med ett intervall på cirka 9% till 27% minskning i antingen U-röret under golvet eller i en platta på värmeväxlaren. Även om dessa värmeövergångstal är lägre än tidigare beräknat, är den erforderliga pumpeffekten också lägre med hjälp av uppdaterade egenskaper: 40% lägre vid en köldbärarestemperatur på -10 ° C. Även om förändringen i värmeövergångstal är större med experimentella värden, är påverkan på COP minimal. Slutsatser från detta projekt är att ammoniakvatten är en lämplig köldbärare jämfört med kalciumklorid och etylenglykol, de två vanligaste köldbärare i ishallskylning. Ett system som använder ammoniakvatten skulle ha ett pumpeffektbehov på 45% respektive 47% jämfört med kalciumklorid respektive etylenglykol. Systemet skulle också ha en 4,7% och 11,6% högre COP jämfört med system med kalciumklorid respektive etylenglykol. Den betydligt lägre pumpeffekten kommer att sänka det totala energibehovet för ishallar, vilket minskar driftskostnaderna.