UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

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 given thesis/dissertation in DRUM.

More information is available at Theses and Dissertations at University of Maryland Libraries.

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2010 - 20133

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    Energy Efficient Two-Phase Cooling for Concentrated Photovoltaic Arrays
    (2013) Reeser, Alexander; Bar-Cohen, Avram; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Concentrated sunlight focused on the aperture of a photovoltaic solar cell, coupled with high efficiency, triple junction cells can produce much greater power densities than traditional 1 sun photovoltaic cells. However, the large concentration ratios will lead to very high cell temperatures if not efficiently cooled by a thermal management system. Two phase, flow boiling is an attractive cooling option for such CPV arrays. In this work, two phase flow boiling in mini/microchannels and micro pin fin arrays will be explored as a possible CPV cooling technique. The most energy efficient microchannel design is chosen based on a least-material, least-energy analysis. Heat transfer and pressure drop obtained in micro pin fins will be compared to data in the recent literature and new correlations for heat transfer coefficient and pressure drop will be presented. The work concludes with an energy efficiency comparison of micro pin fins with geometrically similar microchannel geometry.
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    Using Radio-Frequency Identification Technology To Measure Asphalt Cooling
    (2010) Pfeiffer, Grant Howard; Schwartz, Charles W; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Realistic prediction of asphalt temperatures as a function of time during paving is essential for optimizing compaction operations. Continued compaction after the asphalt lift has dropped below a critical threshold temperature may result in particle breakage and degradation of the material properties. To address this issue, this study evaluates the feasibility of using Surface Acoustic Wave (SAW) based Radio-Frequency Identification (RFID) technology to measure HMA temperatures via wireless sensors during paving. The survivability and temperature measurement capabilities of the SAW RFID sensors are demonstrated in the field. The measured asphalt cooling curves (temperature versus time) are compared with predictions from previously developed theoretical models for mat cooling. The prediction accuracy of these models is improved via a field calibration procedure using measured temperatures from the SAW RFID sensors. The predictions from the calibrated theoretical model are reasonable and agree well with the measured temperatures in the field.
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    Performance of Residential Heating and Cooling Control Strategies using Distributed Wireless Sensor Networks
    (2010) Siemann, Michael; Kim, Jungho; Chopra, Nikhil; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Previous work has suggested that residential space heating and cooling control strategies that partition the structure into individual zones using wireless sensor networks might result in lower energy consumption compared to systems using a single-sensor thermostat. Questions have been posed as to whether these strategies can achieve the same level of performance in a variety of geographic locations and climates. This study compared four control strategies that utilized a wireless temperature and humidity sensor network to regulate the comfort of a residence in the mid-Atlantic region of the United States during the summer and winter. In particular, the energy consumption and comfort levels of each multi-sensor strategy were compared to a baseline strategy that mimicked a single thermostat. The difference in energy usage measured by each control strategy was found to be statistically insignificant. However, experiments indicated that these strategies may nevertheless result in improvements in thermal comfort.