The temperature differential of chilled water is an important factor used for evaluating the performance of a chilled water system. A low delta-T may increase the pumping energy consumption and increase the chiller energy consumption. The system studied in this thesis is the chilled water system at the Dallas/Fort Worth International Airport (DFW Airport). This system has the problem of low delta-T under low cooling loads. When the chilled water flow is much lower than the design conditions at low cooling loads, it may lead to the laminar flow of the chilled water in the cooling coils. The main objective of this thesis is to explain the heat transfer performance of the cooling coils under low cooling loads. The water side and air side heat transfer coefficients at different water and air flow rates are calculated. The coefficients are used to analyze the heat transfer performance of the cooling coils at conditions ranging from very low loads to design conditions. The effectiveness-number of transfer units (NTU) method is utilized to analyze the cooling coil performance under different flow conditions, which also helps to obtain the cooling coil chilled water temperature differential under full load and partial load conditions. When the water flow rate drops to 1ft/s, laminar flow occurs; this further decreases the heat transfer rate on the water side. However, the cooling coil effectiveness increases with the drop of water flow rate, which compensates for the influence of the heat transfer performance under laminar flow conditions. Consequently, the delta-T in the cooling coil decreases in the transitional flow regime but increases in the laminar flow regime. Results of this thesis show that the laminar flow for the chilled water at low flow rate is not the main cause of the low delta-T syndrome in the chilled water system. Possible causes for the piping strategy of the low delta-T syndrome existing in the chilled water system under low flow conditions are studied in this thesis: (1) use of two way control valves; and (2) improper tertiary pump piping strategy.

It has been generally recognized that the surface phenomena of the solid particles such as shrinking and swelling, water- holding capacity, water' movement, and cation exchange are important in understanding the physical properties of the soil. Clay is the most prevalent material in the colloidal fraction of many soils. Because of the complex nature of the surface of clays and the small size of the particles, the direct study of surface phenomena is difficult. Thermodynamic functions change in accordance with changes and organization within the system. Thus, an examination of the thermodynamics of surface phenomena provides some understanding of the reactions.

This research is aimed to study the system performance for a large solar hot water system constructed by connecting a series of small domestic natural circulation systems. There are few studies on this type of large solar hot water system available. The major concern is that when circulation pump is on, there forms a short flow between inlet and outlet of each storage tank of natural circulation solar hot water unit. Therefore, water does not have chance to flow though the collector by thermosyphon and system performance can be lowered down drastically. This thesis presents the numerical simulation study for the control and system operating parameters effects on the system performance to provide important information both for users and system designers.

Education is touted as one of the most effective and inexpensive measures for reducing water consumption for major cities. Coupled with additional water reducing strategies this education can have a significant impact. While, this is a generally accepted principle in the water resources community it has been difficult to accurately quantify the savings. Studies attempting to quantify reductions from these programs have been limited to small samples of neighborhoods. San Antonio is recognized as one of the leading conservation programs in the country at reducing the consumption of its customers. This study focused on over 3,000 customers in San Antonio who were classified as high-end users. The average monthly consumption for this group in June of 2006 exceeded 60,000 gallons per month. Each customer was sent an educational packet by mail with information to conduct an audit of the water use indoors and outdoors. Many of the customers used a free service allowing a trained professional of the San Antonio Water System to conduct their audit at no charge. Three groups were identified (1) those who received a educational packet, (2) those who conducted a home audit and reported they had conducted an audit, (3) those who had a free audit conducted by a trained technician. The water consumption for six months was tracked and compared to the previous year's consumption. Each of the three groups showed savings with those in the third group showing the greatest savings. Lastly, a cost analysis was conducted showing the effectiveness of the program in reducing consumption by cost.

An improved understanding of the costs of diseases is obtained by conducting a case study of the costs associated with end stage renal disease (ESRD). In estimating the costs of ESRD, the costs incurred by both patients and their primary unpaid caregivers are calculated. Most economic studies of the costs of diseases ignore either the patients’ or unpaid caregiver side, focusing on one or the other. From a theoretical standpoint, it is shown unpaid caregiving lowers the costs of diseases to society. Unpaid caregiver lowers the cost, because for unpaid caregiving to occur, the net benefits of unpaid caregiving must be lower than the net benefits of hiring a paid caregiver. Using patients and their primary caregivers at the Gambro Dialysis Center in College Station, Texas as a case study, estimated total ESRD costs range from $84,000 to $121,000 / year / case. The distribution of these costs is positively skewed. Of the total costs, approximately 2% to 25% can be attributed to unpaid caregiving. Excluding direct medical costs in total ESRD costs, unpaid caregiving is 14% to 65% of total ESRD costs. Consideration of unpaid caregiving costs is, therefore, an important component of the costs of diseases. These estimates are conservative as the costs associated with lifestyle changes and health effects are noted, but no monetary value is placed on them. Results also indicate the patients’ and caregivers’ perception of the quantity of caregiving varies. An alternative water supply system to improve the efficiency of water supply systems taking into account water pricing, marketing, and treatment costs is proposed. This system treats and supplies water differently depending on the source of the water and if the end-use of the water is a potable or non-potable use, then may reduce treatment costs. Decreased treatment costs may make more stringent water standards more affordable. More stringent water standards may cause a decrease in the risk of water-related diseases including ESRD induced by water-borne toxins. Reducing the risk of ESRD will reduce society’s costs associated with chronic illnesses. Possible benefits and costs of the proposed system are discussed, but not calculated.

A presente dissertação aborda a modelagem física de sistemas marinho profundo em escala reduzida, uma metodologia que vem contribuindo no entendimento dos processos sedimentares atuantes neste ambiente, principalmente as correntes de turbidez, fluxo gravitacional subaquoso responsável pela formação dos turbiditos, importantes reservatórios de hidrocarbonetos da costa brasileira. A modelagem física 3D empregada neste trabalho aborda a influência da autogênese no comportamento espacial e evolutivo de depósitos análogos gerados por simulações de correntes de turbidez em duas séries de 10 experimentos com parâmetros de controle constantes (vazão, concentração volumétrica de sedimentos, tipo e granulometria das partículas sedimentares), onde em cada série foi utilizada uma concentração de sedimentos diferente: uma com maior concentração – HDTC (high-density turbidity currents) e outra com menor concentração – LDTC (low-density turbidity currents) onde se buscou observar o efeito desta propriedade na construção dos depósitos. Para caracterizar o comportamento geométrico dos depósitos, uma nova abordagem estatística é utilizada a partir de uma análise de variância. Os resultados obtidos apontam que processos autogênicos locais puderam alterar a configuração global dos depósitos. A concentração de sedimentos teve influência direta nas características morfológicas e evolutivas dos depósitos, sendo os experimentos de HDTC os que apresentam uma evolução mais complexa, onde ocorreu um processo de auto-confinamento das correntes, gerando uma morfologia mais diversa. / Autogenic / allogenic controls have been discussed widely because they represent an important parameter in the constructive and evolutionary process of a sedimentary system. To evaluate these controls in submarine fans and analyse its capacity of selforganizing and creating depositional patterns, this work performed fully controlled 3D physical simulations of turbidity currents under ideal autogenic controls (no external influence) with detailed data for the generated deposits. Two series of 10 experiments of high-density turbidity currents (HDTC) and low-density turbidity currents (LDTC) were run, keeping all other input parameters (discharge, volumetric concentration, type and grain size) constant. From statistical and qualitative approach were characterised the geometric elements and morphodynamic behaviour of the deposits (centroid, Length/Width ratio, morphodynamic evolution). The results indicate local autogenic processes change the global setting of the flow evolution and deposits of submarine fans. A morphodynamic evolution generated by HDTC showed complex stages of filling and stacking caused by two types of flow self-channelling. Type I is characterised by flow channelling due to the elevation of levees without lateral avulsion and more efficient sediment transport (longer deposits, with terminal lobes well developed), and Type II is characterised by flow channelling but allows lateral avulsions and involves less efficient sediment transport (shorter deposits with terminal lobes undeveloped). The HDTC deposits showed random behaviour for the length/width ratio and for the centroid of sedimentary bodies and distinct morphological elements (elongated central deposit, fringes and distal lobes). By contrast, the LDTC morphodynamics were simplified without any self-confining process or distinct morphological elements. Finally, the statistical approach showed that the HDTC deposits had a greater variance of geometrical elements in relation to LDTC deposits. The experiments provided evidence that high rates of sediment supply decisively influenced the geometry and morphodynamic of the deposits, as well as they self-organizing capacity.

A presente dissertação aborda a modelagem física de sistemas marinho profundo em escala reduzida, uma metodologia que vem contribuindo no entendimento dos processos sedimentares atuantes neste ambiente, principalmente as correntes de turbidez, fluxo gravitacional subaquoso responsável pela formação dos turbiditos, importantes reservatórios de hidrocarbonetos da costa brasileira. A modelagem física 3D empregada neste trabalho aborda a influência da autogênese no comportamento espacial e evolutivo de depósitos análogos gerados por simulações de correntes de turbidez em duas séries de 10 experimentos com parâmetros de controle constantes (vazão, concentração volumétrica de sedimentos, tipo e granulometria das partículas sedimentares), onde em cada série foi utilizada uma concentração de sedimentos diferente: uma com maior concentração – HDTC (high-density turbidity currents) e outra com menor concentração – LDTC (low-density turbidity currents) onde se buscou observar o efeito desta propriedade na construção dos depósitos. Para caracterizar o comportamento geométrico dos depósitos, uma nova abordagem estatística é utilizada a partir de uma análise de variância. Os resultados obtidos apontam que processos autogênicos locais puderam alterar a configuração global dos depósitos. A concentração de sedimentos teve influência direta nas características morfológicas e evolutivas dos depósitos, sendo os experimentos de HDTC os que apresentam uma evolução mais complexa, onde ocorreu um processo de auto-confinamento das correntes, gerando uma morfologia mais diversa. / Autogenic / allogenic controls have been discussed widely because they represent an important parameter in the constructive and evolutionary process of a sedimentary system. To evaluate these controls in submarine fans and analyse its capacity of selforganizing and creating depositional patterns, this work performed fully controlled 3D physical simulations of turbidity currents under ideal autogenic controls (no external influence) with detailed data for the generated deposits. Two series of 10 experiments of high-density turbidity currents (HDTC) and low-density turbidity currents (LDTC) were run, keeping all other input parameters (discharge, volumetric concentration, type and grain size) constant. From statistical and qualitative approach were characterised the geometric elements and morphodynamic behaviour of the deposits (centroid, Length/Width ratio, morphodynamic evolution). The results indicate local autogenic processes change the global setting of the flow evolution and deposits of submarine fans. A morphodynamic evolution generated by HDTC showed complex stages of filling and stacking caused by two types of flow self-channelling. Type I is characterised by flow channelling due to the elevation of levees without lateral avulsion and more efficient sediment transport (longer deposits, with terminal lobes well developed), and Type II is characterised by flow channelling but allows lateral avulsions and involves less efficient sediment transport (shorter deposits with terminal lobes undeveloped). The HDTC deposits showed random behaviour for the length/width ratio and for the centroid of sedimentary bodies and distinct morphological elements (elongated central deposit, fringes and distal lobes). By contrast, the LDTC morphodynamics were simplified without any self-confining process or distinct morphological elements. Finally, the statistical approach showed that the HDTC deposits had a greater variance of geometrical elements in relation to LDTC deposits. The experiments provided evidence that high rates of sediment supply decisively influenced the geometry and morphodynamic of the deposits, as well as they self-organizing capacity.

A presente dissertação aborda a modelagem física de sistemas marinho profundo em escala reduzida, uma metodologia que vem contribuindo no entendimento dos processos sedimentares atuantes neste ambiente, principalmente as correntes de turbidez, fluxo gravitacional subaquoso responsável pela formação dos turbiditos, importantes reservatórios de hidrocarbonetos da costa brasileira. A modelagem física 3D empregada neste trabalho aborda a influência da autogênese no comportamento espacial e evolutivo de depósitos análogos gerados por simulações de correntes de turbidez em duas séries de 10 experimentos com parâmetros de controle constantes (vazão, concentração volumétrica de sedimentos, tipo e granulometria das partículas sedimentares), onde em cada série foi utilizada uma concentração de sedimentos diferente: uma com maior concentração – HDTC (high-density turbidity currents) e outra com menor concentração – LDTC (low-density turbidity currents) onde se buscou observar o efeito desta propriedade na construção dos depósitos. Para caracterizar o comportamento geométrico dos depósitos, uma nova abordagem estatística é utilizada a partir de uma análise de variância. Os resultados obtidos apontam que processos autogênicos locais puderam alterar a configuração global dos depósitos. A concentração de sedimentos teve influência direta nas características morfológicas e evolutivas dos depósitos, sendo os experimentos de HDTC os que apresentam uma evolução mais complexa, onde ocorreu um processo de auto-confinamento das correntes, gerando uma morfologia mais diversa. / Autogenic / allogenic controls have been discussed widely because they represent an important parameter in the constructive and evolutionary process of a sedimentary system. To evaluate these controls in submarine fans and analyse its capacity of selforganizing and creating depositional patterns, this work performed fully controlled 3D physical simulations of turbidity currents under ideal autogenic controls (no external influence) with detailed data for the generated deposits. Two series of 10 experiments of high-density turbidity currents (HDTC) and low-density turbidity currents (LDTC) were run, keeping all other input parameters (discharge, volumetric concentration, type and grain size) constant. From statistical and qualitative approach were characterised the geometric elements and morphodynamic behaviour of the deposits (centroid, Length/Width ratio, morphodynamic evolution). The results indicate local autogenic processes change the global setting of the flow evolution and deposits of submarine fans. A morphodynamic evolution generated by HDTC showed complex stages of filling and stacking caused by two types of flow self-channelling. Type I is characterised by flow channelling due to the elevation of levees without lateral avulsion and more efficient sediment transport (longer deposits, with terminal lobes well developed), and Type II is characterised by flow channelling but allows lateral avulsions and involves less efficient sediment transport (shorter deposits with terminal lobes undeveloped). The HDTC deposits showed random behaviour for the length/width ratio and for the centroid of sedimentary bodies and distinct morphological elements (elongated central deposit, fringes and distal lobes). By contrast, the LDTC morphodynamics were simplified without any self-confining process or distinct morphological elements. Finally, the statistical approach showed that the HDTC deposits had a greater variance of geometrical elements in relation to LDTC deposits. The experiments provided evidence that high rates of sediment supply decisively influenced the geometry and morphodynamic of the deposits, as well as they self-organizing capacity.

Chilled water systems constitute a major portion of energy consumption in air conditioning systems of commercial buildings and process cooling of manufacturing plants. These systems do not operate optimally in most of the cases because of the operating parameters set and/or the components used. A Chilled water system analysis tool software (CWSAT) is developed as a primary screening tool for energy evaluation. This tool quantifies the energy usage of the various chilled water systems and typical measures that can be applied to these systems to conserve energy. The tool requires minimum number of inputs to analyze the component-wise energy consumption and incurred overall cost. This thesis also examines various energy conservation measures that are available for chilled water systems. The components, arrangements, and the common energy conservation opportunities for chilled water systems are presented. The new version of the tool is developed in Object Oriented Programming Language Microsoft Visual Basic.Net© to maintain the tool latest with current technology, add and expand capabilities and avoid obsolescence. Many Improvements to the previous tool are made to improve quality and the types of the systems the tool can handle. The development of the new routines and interfaces is also accommodated in the new version to make the tool universal. In order to determine the accuracy of the new version of the tool, a comparison is made between the results from the previous and new version of the tool. The results of the comparisons are presented.

Precipitation of solids in plumbing systems (i.e., scaling) is a major problem in both traditional tank (electric and gas) and tank-less building hot water systems. Scaling can cause energy inefficiencies, flow reduction, pressure loss, and erosion corrosion damage. Consumers are also concerned with unsightly soap scum, cloudy water, discolored glassware, and failing infrastructure including appliances and fixtures. There are many treatments available that claim to ameliorate scaling problems, and several efforts have been made to develop standardized test protocols to verify and quantify their performance. This work critically evaluated previous testing efforts and revealed limitations in terms of reproducibility and a need to measure all key aspects of scale deposition including quantity, location, aesthetic and other issues. A Standardized Scaling Test Protocol (SSTP) was conceived and vetted to address these deficiencies and measure key parameters of calcium carbonate scaling throughout a model premise plumbing system, while using a synthesized test water that could provide reproducible results in any laboratory. This synthetic water and methodology was able to produce significant scaling in a model hot water system within the targeted 5-day experimental time frame. The average amount of scale recovered for the triplicate control tests (with no scale reduction device) was 25.1 grams of calcium carbonate with a 95% confidence interval of 20.3-29.8 grams of calcium carbonate. The approach also worked in recreating scaling in natural waters and was used to verify the performance of a wide array of scale reduction technologies including cation exchange softeners, electrochemical deionization, physical magnets or electric field generators, media induced precipitation, sacrificial media (phosphate), and sacrificial media (citric acid). While calcium carbonate precipitation within a water distribution system is generally undesirable; it was recently discovered that calcium carbonate particles are sometimes naturally clogging leaks in pipes and extending the lifetime of aging infrastructure. Corrosion inhibitors, mainly phosphates, have been increasingly dosed (up to 3.0 mg/L as PO4) into water to inhibit the corrosion of lead and copper pipelines in potable water systems since the advent of the Lead and Copper Rule (LCR) in 1991 by US Environmental Protection Agency (EPA). Phosphate corrosion inhibitors are now used at over 50% of water utilities in the United States and they can affect calcium carbonate scaling kinetics. In bench-scale experiments, the critical concentrations of phosphates that could inhibit leak repair over the short-term in one water tested were: tripolyphosphate (0.05 mg/L as P) < hexametaphosphate (0.1 mg/L) < orthophosphate (0.3 mg/L). The results prove that dosing of phosphates for corrosion control will also affect the kinetics and likelihood of calcium carbonate precipitation, with both beneficial and adverse consequences for pipes and consumers. Specifically, increased use of inhibitors for corrosion control is expected to reduce the likelihood of all calcium carbonate scaling problems while reducing the likelihood of autogenous pipe leak repair. In Providence, RI the dosing of orthophosphate at relatively high pH to control a lead corrosion problem, caused formation of a white precipitate, consumer reports of white water, clogging of aerators and loss of the added soluble phosphate corrosion control inhibitor due to precipitation. The precipitate was identified as a calcium phosphate solid. Field and lab scale tests suggest that at doses below 2 mg/L as PO4, precipitation did not occur in water at pH 10.4 even when the water was heated to 48°C. However, if the water was dosed above 2 mg/L as PO4 precipitation occurred within 5 minutes, and once pre-existing particles were formed precipitation tended to continue even at much lower phosphate doses. Virtually all of the phosphate precipitated within 4 hours at the upper range of 60°C that is commonly found in water heaters. Thus, dosing of phosphate can actually increase scaling problems in some circumstances. Prior work has highlighted a need for a simplified bench-scale test that can be used to rapidly screen for qualitative trends in scaling. The SSTP and practical experience showed that the vast majority of scaling occurred in the water heater. Therefore, a simplified bench-scale test consisting of a heating element in a small volume of water could be used to focus on the most sensitive aspect of scaling. A 3-hour bench-scale test was developed to quickly examine scaling with orders of magnitude less volume, time, labor, cost, and space requirements. This approach was used to evaluate aspects of scaling in water heaters for the following illustrative examples: (1) scale impacts of combined phosphate corrosion inhibitor addition and partial water softening at centralized treatment plants, (2) role of silica concentration in scaling propensity and deposit durability, (3) effects of phosphate addition on scaling in a water known to cause erosion corrosion pipe damage. This dissertation reveals the complexity of scaling for consumers and water utilities and provides tools to systematically study and resolve these practical problems. Dosing of phosphate corrosion control inhibitors can increase scaling from calcium phosphate, decrease scaling of calcium carbonate, and in other cases will have little or no effect on scaling. Both calcium carbonate and calcium phosphate can contribute to scaling as controlled by pH, temperature, hardness, phosphate dose, and other circumstances. The standardized bench and pilot scale approaches developed herein, can serve as a basis for building knowledge reproducibly in any modern laboratory. These methods can also be used to verify performance claims for a wide range of scale reduction technologies, test treatments that could be applied at centralized treatment plants, and optimize water heater design dependent on water chemistry. / Doctor of Philosophy / Precipitation of solids in plumbing systems (i.e., scaling) is a major problem in both traditional tank (electric and gas) and tank-less hot water systems. In addition to scale build up within the hot water system, consumers are also concerned with unsightly soap scum, cloudy water, discolored glassware, and failing infrastructure including appliances and fixtures. There are many treatments available that claim to mitigate scaling problems, and several efforts have been made to develop standardized test protocols to verify and quantify their performance. This work evaluated previous testing efforts to determine limitations in their methodology. A Standardized Scaling Test Protocol (SSTP) was developed to address these deficiencies and measure key parameters of calcium carbonate scaling throughout a model home plumbing system, while using a test water that could provide reproducible results in any laboratory. The test water was able to produce significant scaling within a 5-day test period with reproducible results. While calcium carbonate precipitation within a water distribution system is generally undesirable; it was recently discovered that calcium carbonate particles are sometimes naturally repairing leaks in pipes and extending the lifetime of aging plumbing systems. An increasing number of water treatment plants are adding corrosion inhibitors to water to prevent the corrosion of lead and copper pipelines. Small scale lab experiments were run to determine how effective this natural leak repair was when there were corrosion inhibitors in the water. The results showed that most corrosion inhibitors also prevented or delayed calcium carbonate precipitation which reduced the likelihood of pipe repair through clogging leaks. In Providence, RI the addition of a corrosion inhibitor caused a white precipitate to form in the water which led to consumer complaints of white water and clogging of aerators. This was due to the uniquely high pH of the water. The precipitate was identified as a calcium phosphate solid. Field and lab scale tests suggest that there is a critical inhibitor dose, below which no precipitation occurred in the high pH water. However, if the water was dosed above this critical limit, precipitation occurred immediately and continued as time went on. Prior work has highlighted a need for a simplified bench-scale test that can be used to rapidly screen for qualitative trends in scaling. A 3-hour bench-scale test was developed to quickly examine key aspects of scaling with orders of magnitude less volume, time, labor, cost, and space requirements. This dissertation reveals the complexity of scaling for consumers and water utilities and provides tools to systematically study and resolve these practical problems.