Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 84-85). Also available via the Internet.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Graham, Sam; Committee Member: Joshi, Yogendra; Committee Member: Kalaitzidou, Kyriaki. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph. D.)--University of Florida, 1982. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 140-143).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 352-356).

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 182-186). Also available on the Internet.

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D.Ing. / Many studies have been conducted in order to establish the respective influence of geometric parameters such as fins number, fin shape (apex angle), spiral angle, fin height, fin pitch etc. on the condensation heat transfer performance of the spiralled micro-fin tubes. However, the effect of the spiral angle could not be clearly established in those investigations, because other geometric parameters affecting the heat transfer performance such as fin height, fin thickness, apex angle were also varied. The influence of the spiral angle on the heat transfer performance during condensation inside spiralled micro-fin tubes having all other geometric parameters the same was experimentally investigated in this study. A new experimental-based predictive correlation was developed for practical design of this specific class of micro-fin tubes. Tests were conducted for condensation of R22, R134a and R407c inside a smooth and three micro-fin tubes having spiral angles of 10, 18 and 37 degrees. Experimental results indicated a heat transfer augmentation due to heat transfer area increase. As the spiral angle was increased, the heat transfer area increased causing a substantial heat transfer augmentation. Condensation inside the 10° spiralled micro-fins produced a heat transfer augmentation of about 170% for a heat transfer area increase of 1.87 when compared to condensation in ~he correspondent smooth tube while the 18° spiralled " micro-fins produced an augmentation of 180% for a heat transfer area increase of 1.94. The 37° spiralled micro-fins produced the highest enhancement of 220% for a heat transfer area increase of 2.13. Additional heat transfer augmentation was produced by: (a) the turbulence in the condensate film due to the presence of spiralled micro-fins (stronger effect at lower mass velocities and vapor qualities) and (b) the effect of surface tension forces (at higher vapor qualities). The proposed new correlation predicted the majority of experimental results of the present study within a deviation zone of ± 20 percent.

Driven by the importance of optimizing energy systems and technologies, the field of exergy analysis was developed to better illuminate process inefficiencies and evaluate performance. Exergy analysis provides important information and understanding that cannot be obtained from energy analysis. The field of exergy analysis is well formulated and understood except for thermal radiation (TR) heat transfer. The exergy flux, or maximum work obtainable, from TR has not been unambiguously determined. Moreover, many thermodynamic textbooks are misleading by incorrectly implying that the entropy and exergy transport with TR is calculated by using the same expressions that apply to heat conduction. Research on the exergy of TR was carried out by Petela. However, many researchers have considered Petela's analysis of the exergy of TR to be irrelevant to the conversion of TR fluxes. Petela's thermodynamic approach is considered irrelevant because, others argue, that it neglects fundamental issues that are specific to the conversion of fluxes, issues that are unusual in the context of exergy analysis. The purpose of the research in this thesis is to determine, using fundamental thermodynamic principles, the exergy flux of TR with an arbitrary spectrum and its relevance to solar radiation (SR) conversion. In this thesis it is shown that Petela's result can be used for the exergy flux of blackbody radiation (BR) and represents the upper limit to the conversion of SR approximated as BR. The thesis shows this by resolving a number of fundamental issues: (1) Inherent Irreversibility; (2) Definition of the Environment; (3) Inherent Emission; (4) Threshold Behaviour; (5) Effect of Concentrating TR. This thesis also provides a new expression, based on inherent irreversibility, for the exergy flux of TR with an arbitrary spectrum. Previous analysis by Karlsson assumes that reversible conversion of non-blackbody radiation (NBR) is theoretically possible, whereas this thesis presents evidence that NBR conversion is inherently irreversible. In addition the following conclusions and contributions are made in the thesis: (1) Re-stated the general entropy and exergy balance equations for thermodynamic systems so that they correctly apply to TR heat transfer. (2) Provided second-law efficiencies for common solar energy conversion processes such as single-cell Photovoltaics. (3) Showed that Omnicolor (infinite cell) conversion, the widely held ideal conversion process for SR, is not ideal by explaining its non-ideal behaviour in terms of exergy destruction and exergy losses. (4) Presented an ideal (reversible) infinite stage thermal conversion process for BR fluxes and presented two-stage thermal conversion as a practical alternative. (5) Showed that Prigogine's minimum entropy production principle cannot be used as a governing principle in atmospheric modeling, and that in general, it may have little significance. (6) Presented a graybody model of the planet that may prove useful in understanding the thermodynamics of the Earth system. (7) Showed that the expression derived from the Clausius equality for reversible processes is applicable, whereas the statement for irreversible processes is not applicable, when there is significant heat transfer by TR. (8) Showed that the 4/3 coefficient in the BR entropy expression can be obtained by simply using the concept of equilibrium and the experimentally observable relationship for BR energy (energy x T⁴). / Graduate

M.Ing. / This study involves the mathematical modeling and experimental verification of a heat exchanger accumulator. The study was initiated with a literature survey which, according to the author, revealed that there was no published material that described how heat exchanger accumulators are designed to ensure that they are correctly sized according to the operating system and conditions. The heat exchange process that takes place within the heat accumulator was studied and a mathematical model of a heat exchanger accumulator developed. This model was used to develop a universal design procedure that correctly sized the heat exchanger accumulator according to various requirements identified by the author. The model was then verified by conducting experimental tests and it was concluded that the model could be used to design heat exchanger accumulators.