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
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Item NUMERICAL MODELING AND EXPERIMENTAL STUDY OF A NOVEL METAL-POLYMER COMPOSITE HEAT EXCHANGER FOR SENSIBLE AND LATENT THERMAL ENERGY STORAGE APPLICATIONS(2022) KAILKHURA, GARGI; Ohadi, Michael; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Compact, lightweight, and low-cost heat exchangers (HXs) have the potential to improve efficiencies and save power and carbon foot print in a wide array of applications. The present study investigates an entirely additively-manufactured novel metal-polymer composite heat exchanger, enabled by an innovative and patented cross-media thermal exchange approach, which yields an effective thermal conductivity of 130 W/m-K for the heat exchanger. This record-high thermal conductivity is more than an order of magnitude higher that the previously reported thermal conductivity for polymer and polymer composite HXs. Drawing on the concept of external flow over the tube banks, the proposed HX features a staggered arrangement of fins. This class of HXs are often used for gas-to-liquid sensible cooling applications. However, they can also be designed for latent thermal energy storage applications by employing low-cost and high energy-storage-density phase change materials (PCMs) such as salt-hydrates and alike in either the hot or cold side of the HX, depending on the application. An extensive literature survey on tube banks shows that, though numerous correlations exist in the literature for flow over tube banks, these correlations usually fall outside the range for the current HX design for low-Reynolds number applications (Re<100). Furthermore, the PCM models present in the literature are either very challenging to solve analytically or are computationally expensive. Thus, the dissertation emphasizes developing computationally-efficient and robust numerical models for sensible and latent cooling applications.The numerical models compute the overall thermal and pressure-drop performance metrics based on segment-level modeling, and they integrate the performance parameters such as Euler, Nusselt numbers, or latent thermal energy with the entire HX analytically, thus significantly reducing the computational cost. For steady-state sensible thermal energy storage applications, a realistic 3D CFD-based modeling approach is used, based on the actual dimensions of the printed HXs rather than a traditional 2D CFD-based model. It also resolves the issues due to the 3D velocity field which aren’t captured in the 2D CFD models, and are particularly important for HXs utilizing narrow/micro channels. This modeling approach is used to obtain optimized HXs for case examples of 5-40 kW air-conditioning applications and 250-W electronic cooling applications for nominal operating and flow conditions. The 250-W unit is further validated experimentally and is observed to be within 17% for waterside pressure drop, 11% for airside pressure drop, and within 8% for thermal resistance when compared against experimental measurements. For transient latent thermal storage applications, an analytical-based 1D reduced order model (ROM) for segment-level modeling is developed based on 1D radial conduction inside the PCM. It is numerically validated with commercial CFD tools to within 10% except for cases where axial conduction in PCM is possible due to the high resistance of wire embedded in the PCM. The 1D ROM is used in optimizing a 1.44-MJ TES unit for peak-load building cooling applications and a 19.2-kJ HX for pulsed-power cooling applications. The 1.44-MJ unit is experimentally tested and observed to be within 17% for the melting time of complete PCM and about 8% for the freezing time of the complete PCM. Lastly, another novel and hybrid thermal energy storage design is formulated, which utilizes two different PCMs: shape memory alloys (SMAs) instead of metal wires and salt-hydrates contained inside polymer channels similar to the reference designs. Besides the thermal energy storage design, a novel methodology on Wilson plot for finned surfaces on both fluid-sides is introduced, which is first of its kind in the literature. Ongoing and future work in both these areas is also recommended in the final chapter of the thesis.Item The Waterpark(2014) Kipp, Katherine; Casey, Maud; Creative Writing; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In The Waterpark, the Mississippi river offers the promise of escape while also freezing the fictionalized version of Cape Girardeau, Missouri, forever bound to that body of water. The novel begins with Helen detailing her father's desire to create a waterpark in the middle of Midwestern fields. In her mid-20s in the main storyline, Helen begins to learn that family responsibility and the desire to please one's parents never stops, even after death. As she takes control of her father's waterpark, she is conflicted by contrasting memories of the waterpark of her childhood and the realization that the park will ask for more of her than she is prepared to give. Furthermore, Helen realizes the consequences of her self-created loneliness as she isolates herself continually from the people around her, purposefully or not, and begins to thrive more in the memories of the waterpark than in her current life.Item Ghost Arm(2013) Wyss, Allison; Casey, Maud; Creative Writing; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Ghost Arm is the beginning of a novel-in-progress about a woman who has lost her left arm. She has a phantom limb, but the phantom is an actual ghost who acts on his own and gets into trouble.Item Postcolonial Refashionings: Reading Forms, Reading Novels(2009) Comorau, Nancy Alla; Ray, Sangeeta; English Language and Literature; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation reads the postcolonial novel through a lens of novel theory, examining the ways in which the postcolonial novel writes a new chapter in the history of the novel. I explore how Postcolonial writers deploy--even as they remodel--the form of the British novel, which provides them a unique avenue for expressing national and individual historical positions and for imaginatively renegotiating their relationships to the canon and the Commonwealth, past and present. In doing so, they remake the forms they have inherited into the genre of the postcolonial novel. The novel, due to its connection to modernity, the nation, and the formation of the subject, holds different possibilities for postcolonial writers than other forms. My dissertation answers readings of postcolonial texts, which, while often superb in their interpretation of the political, fail to focus on genre. In a fashion, postcolonial novels are read as anthropological works, providing glimpses into a culture, and in a peculiar way the novel comes to operate as the native informant. Given the proliferation of the Anglophone postcolonial novel, I argue that it is important that we consider how the postcolonial novel renders established genres into new forms. I focus on a set of postcolonial novels that specifically engage with canonical British novels, calling attention to the fact that while they share much with their predecessors, they function differently than the novels that have come before them. Unlike early postcolonial arguments about empire "writing back" to the center, which position postcolonial and "English" writers in an antipodal power struggle, I argue that the Anglophone postcolonial novel is at once a descendent of the British novel and a genre unto itself--forming a new limb from the British novel's branch. In doing so, these novels perform new ways of writing modernity, the nation, and the subject. Working from a Bakhtinian theory of the modern novel as a form that creates newness, I demonstrate how postcolonial writers use the history and tradition of the British novel to write, revise, and refashion the novel in English.Item When the Clothes Do Not Make the Man: Female Masculinity and Nationalism in Eighteenth-Century British Literature(2006-08-01) Jansen, Leslie; Lanser, Susan S; English Language and Literature; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recently, masculinity has garnered much attention from scholars of eighteenth-century literature and history. However, these studies focus almost exclusively on the masculinity performed by men. Likewise, studies of female masculinity tend to examine masculine women only within the context of women. My dissertation lies at the convergence of these two areas of inquiry by examining the implications of female masculinity on normative masculinity and the link between these masculinities and nationalism from the early to late eighteenth century, with particular emphasis at the mid-point of the century. I argue that female masculinity was integral to the development and construction of an idealized masculinity and that both positive and negative responses to female masculinity fostered nationalist propaganda and aided in the development of the British Empire. In the first chapter, I trace the shifting grounds of normative masculinity and argue that what constitutes masculinity narrows as the century progresses and is defined by its resistance to any connection with French culture, particularly within the rising middle class. Chapter two examines three female soldier narratives, some of the only positive representations of female masculinity. I argue that the authors praise female masculinity as a means of creating a heroic masculinity to serve the nation. The third chapter examines the function of female husbands. I argue that these texts employ female husbands as a means of inciting xenophobia and promoting nationalism, through narrative strategies of silence and disclosure. In the final chapter, I discuss the masculine women who populate four domestic novels. I posit that female masculinity functions as a means of authorizing sentimental masculinity, a mode of masculinity popular in mid-to late eighteenth-century novels. Through the examination of texts such as novels, pamphlets, and biographies, my dissertation insists that female masculinity was an integral force in the construction of normative masculinity and was intimately linked to a nationalist agenda in the eighteenth century.