Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item LOW IMPACT DEVELOPMENT MIXTURE EVALUATION FOR HEAVY METAL REMOVAL(2019) Liang, Liang; Davis, Allen P.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)To address non-point heavy metal pollutant sources to urban stormwater runoff, the LIDMATTM (Low Impact Development MAT) is a stormwater management runoff system designed and manufactured for effective treatment for heavy metals. The LIDMATTM contains approximately 70% sand, 25% manure compost, and 5% steel slag by mass. The LIDMATTM was evaluated based on flow rate, pH, heavy metal removal, and the concentrations of N and P leached; conditions for optimum removal have been quantified. For treating synthetic stormwater runoff, 12 trials were completed using bench-scale and column media testing systems. Average effluent event mean concentrations of all trials were 25 ± 10 μg/L Cu, 21 ± 13 μg/L Pb, and 57 ± 42 μg/L Zn from studies at influent concentrations of 500 μg/L, 300 μg/L, and 100 μg/L, which satisfy Numeric Action Levels (NALs) of Cu, Pb, and Zn by the state of California, USA, Industrial General Permit (IGP). The leaching of nitrogen and phosphorous were also below the NALs.Item Review of Thermal Energy Storage Technologies and Experimental Investigation of Adsorption Thermal Energy Storage for Residential Application(2013) Li, Gang; Hwang, Yunho; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Thermal energy storage (TES) technologies can reduce or eliminate the peak electric power loads in buildings, and utilize benefits of waste heat recovery and renewable energy. This thesis work consists of TES literature review and experimental investigation of adsorption TES. Review work includes cold storage technologies for air conditioning and subzero applications, and heat storage technologies for residential application. Different technologies involving sensible, latent and sorption TES were compared and resolutions of their issues were summarized. In addition, adsorption TES was experimentally investigated and its energy and exergy flows were analyzed to evaluate the effects of different operating parameters, such as temperature and heat transfer fluid mass flow rate for different chambers on the system performance. Finally, a computer model was developed for the adsorption heat TES system integrated with a vapor compression heat pump to assess its performance. Simulation results showed that overall coefficient of performance (COP) and exergy-based COP are approximately 3.11 and 0.20, respectively.Item Development and analysis of micro polygeneration systems and adsorption chillers(2012) Gluesenkamp, Kyle; Radermacher, Reinhard; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)About a fifth of all primary energy in the US is consumed by residential buildings, mostly for cooling, heating and to provide electricity. Furthermore, retrofits are essential to reducing this consumption, since the buildings that exist today will comprise over half of those in use in 2050. Residential combined heat and power (or micro CHP, defined by <5 kW electrical generation capacity) has been identified as a retrofit technology which can reduce energy consumption in existing homes during the heating season by 5-30%. This thesis investigates the addition of a thermally-driven chiller/heat pump to a CHP system (to form a trigeneration system) to additionally provide savings during the cooling season, and enhance heating season savings. Scenarios are identified in which adding thermally-driven equipment to a micro CHP system reduces primary energy consumption, through analytical and experimental investigations. The experimental focus is on adsorption heat pump systems, which are capable of being used with the CHP engines (prime movers) that are already widely deployed. The analytical analysis identifies energy saving potential off-grid for today's prime movers, with potential on-grid for various fuel cell technologies. A novel dynamic test facility was developed to measure real-world residential trigeneration system performance using a prototype adsorption chiller. The chiller was designed and constructed for this thesis and was driven by waste heat from a commercially available natural gas-fueled 4 kW (electric) CHP engine. A control strategy for the chiller was developed, enabling a 5-day experiment to be run using a thermal load profile based on moderate Maryland summer air conditioning loads and typical single-family domestic hot water demand, with experimental results in agreement with models. In this summer mode, depending on electrical loads, the trigeneration system used up to 36% less fuel than off-grid separate generation and up to 29% less fuel than off-grid CHP without thermally driven cooling. However, compared to on-grid separate generation, the experimental facility used 16% more primary energy. Despite high chiller performance relative to its thermodynamic limit, this result is primarily due to the electrical efficiency of the prime mover being lower than the grid. A residential trigeneration system utilizing a high temperature fuel cell is predicted to save up to 42% primary energy relative to the grid.Item Nonlinear Optical Studies of Molecular Adsorption and Solvation at Solid/Liquid and Liquid/Liquid Interfaces(2011) Siler, Antonie Renee; Walker, Robert A; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Interfacial solvation is responsible for promoting biological phenomena in vivo including protein folding, solute transfer across membranes and enzymatic activity. The specific solvation interactions responsible for these and other processes can be both cooperative and complex. Because many cellular processes rely on interfacial effects, understanding how forces at an interface influence a solute will give insight into how molecules behave within these cellular bodies. The studies presented here are focused on isolating how these solvation interactions vary systematically with the identity of the solute and solvent at an interface. The interfaces probed in these experiments varied from weakly to strongly associating interfaces defined as such by the identity of the solvent used to form the silica/liquid interface. Findings from strongly associating interfaces gave rise to surprising results from both the silica/methanol and silica/ethanol interfaces. The silica/ethanol interface forms a very polar interface as probed by the solute p-nitroanisole (pNAs). At the silica/methanol interface, a very nonpolar region was probed by several solutes sensitive to solvent polarity. The findings from the silica/methanol interface, led us to the research completed in the final chapter of this thesis. Data obtained from these measurements described the interfacial solvation and adsorption behavior of two solutes, pNAs and p-nitrophenol (pNP). Several silica/liquid interfaces were used in this study including, water, dimethyl sulfoxide (DMSO), acetonitrile (ACN), n-hexane, decane, cyclohexane, and methyl-cyclohexane. The two solutes are sensitive to solvent polarity and show similar solvatochromic behavior in bulk solvents. The solutes sample different interfacial polarities at the same silica/liquid interfaces according to SHG spectra obtained. pNAs is shown to be more sensitive to solvent identity at an interface than pNP, but less surface active. The sensitivity of pNAs to solvent identity at a silica/liquid interface is attributed to the solute's higher solubility in the solvents than pNP's solubility in the same solvents. On average, pNP has ~10 kJ/mol more adsorption energy at the measured interfaces than pNAs, and this too can be attributed to the inability of pNP to sufficiently solvate in many of the alkane solvents, forcing the solute out of solution and into the interface.Item Adsorption Humidity Effects, Microparticle Rate Behavior, and Thermal Swing Adsorption(2005-12-06) mahle, john; Harris, Michael T.; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Application of adsorption processes for air purification requires an approach, which accounts for the presence of humidity. Four separate but related studies are conducted to examine the adsorption processes. A new pure component adsorption isotherm is developed to describe Type 5 adsorption. The results are used to correlate data of water on activated carbon. This model derives from the concept that capillary condensation accounts for Type 5 behavior and is strongly dependent on the pore size distribution. The new model has the advantage over all other prior models of being invertible in terms of loading and partial pressure. The Henry's law limit and heat of adsorption effects are discussed. A study of coadsorption of water and immiscible organics is also presented. Data for the system chloroethane water on two activated carbons is measured. A new coadsorption model is developed to describe immiscible vapors and water. This model has the advantage of at most one adjustable parameter and can also be solved without iteration. Good agreement is demonstrated between this new model, data measured here and literature data. The use of thermal swing adsorption for air purification is examined in this work. An experimental system is used to perform cycling experiments under dry and humid conditions. A dynamic simulation model is developed to describe several of cycling runs. Using the coadsorption model developed above the good agreement is found between the data and simulation profiles. Optimization of cycle parameters was investigated to show that some moderation of the feed water content is required to obtain high purification of a light vapor challenge at ambient temperature conditions. The internal rate effects of commercial adsorbents have been reported in the literature. There is seldom an attempt to review the many approaches. Data was measured using a gravimetric technique for chloroethane and hexane on BPL activated carbon and 13X molecular sieve. A distributed parameter micropore diffusion model was solved to simulate this data. Regression of the adsorption and desorption data was used to determined micropore diffusion coefficients. These values were shown to compare well with literature values.