A. James Clark School of Engineering
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item PERFORMANCE OF A MICROCHANNEL-THERMOELECTRIC POWER GENERATOR WITH ALUMINA-IN-WATER NANOFLUIDS AS COOLANTS(2010) Ahuja, Herwin Singh; Yang, Bao; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In the past two decades, the rapid advancement of military aircraft in terms of performance and power consumption in order to accomplish evermore demanding missions has introduced new challenges, namely, having to conserve of non-renewable petroleum, minimize carbon emissions, and accomplish more mission per unit energy. This thesis describes the work done to evaluate the performance of a renewable-energy device termed the microchannel-thermoelectric power generator (MC-TEPG), which uses alumina-in-water nanofluids as coolants, that is intended to replace or supplement current non-renewable power supplies such as battery packs in order to contribute to overcoming the abovementioned challenges. The MC-TEPG recovers waste heat internally generated by motors of military aircraft and converts it to usable electric power via the Seebeck effect. This thesis studies nanofluid flow and heat transfer in the MC-TEPG microchannels, and thermoelectric power generation under varying conditions. Current results show MC-TEPG feasibility and suggest future promise.Item Construction of Test Facility to Measure and Visualize Refrigerant Maldistribution in Multiport Evaporator Headers(2005-07-18) Linde, John Eric; Radermacher, Reinhard; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In a refrigeration cycle, condensed liquid refrigerant is expanded to a two-phase fluid entering the evaporator. In many applications, the evaporator paths are divided into a number of parallel sections to keep the pressure drop across the evaporator within a reasonable range and to maximize overall heat exchanger performance. Since the state of the refrigerant entering the evaporator is two-phase and its quality changes depending upon the operating conditions, the proper refrigerant distribution to individual sections is not an easy task. Nonuniform distribution, or maldistribution, will cause dry out at sections of lesser mass flow by superheating the refrigerant gas. This can result in nonuniform heat exchanger surface temperature distribution. Single-phase heat transfer coefficients (HTCs) are much lower than those of two-phase HTCs. When dryout occurs, both refrigerant-side HTCs and air-side HTCs are lower than those of wet surfaces. In addition to this, the temperature difference between the air and