Graduate Thesis Or Dissertation
 

Optimization of staged rankine energy conversion cycles for high efficiency

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/2j62s825j

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  • Because of the fuel crisis and problems associated with thermal pollution there is new impetus and urgency for developing more efficient energy conversion systems for power generation. A preliminary analysis was undertaken to determine the potential of staged Rankine cycle systems for substantially higher efficiency. It was necessary to optimize the cycles to determine maximum potential efficiency, and the Sequential Unconstrained Minimization Technique of nonlinear programming was implemented on the Oregon State University CDC 3300 computer for this purpose. Binary, ternary, and quaternary Rankine cycle configurations were optimized for maximum efficiency under a set of realistic constraints. Liquid metal working fluids were used for the higher temperature stages with water for the low temperature stage fluid. Maximum efficiencies are presented for the best cycle configurations with peak temperatures from 900°F to 3000°F. Sensitivity of the results to certain critical assumptions is also included. The potential efficiency gains at current peak cycle temperatures are small, but, if high temperature expanders such as high temperature turbines, graphite helical rotor expanders, or MHD vapor expanders prove to be feasible, staged Rankine cycles can clearly provide high efficiencies with much lower temperature requirements than magnetohydrodynamic Brayton systems. In order to determine ultimate potential of the staged cycles, conventional Rankine cycle improvements were considered for each stage also. Only extraction/regeneration was found to give any significant improvement and results are presented for a binary configuration with one to five extractions on each stage. Organic working fluids were considered as a replacement for mercury, and ammonia was considered as a low temperature stage working fluid for a stage below the steam cycle. Neither organic fluids nor ammonia proved to have any outstanding advantages for use in staged cycles. Staged cycles with a metal working fluid topping a steam cycle are probably best overall.
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  • File scanned at 300 ppi (Monochrome) using Capture Perfect 3.0.82 on a Canon DR-9080C in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
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