Identification and selection of unconstrained controls in power systems propelled by heat and mass transfer

Stanisław Sieniutycz

Abstract

This investigation provides an approach towards identification, selection or construction of certain unconstrained controls called Carnot variables which are particularly suitable for easy determining of power limits in various power systems. Applying these controls we develop a unified analysis of how various transfer phenomena (heat, mass and electric charge transfer) effect power limits in various energy converters, such as thermal, chemical and radiation engines and fuel cells. We present diverse pseudo-Carnot structures for converters’ efficiencies and apply them in estimating irreversible power limits in steady state systems. Power limits are determined for steady thermal systems propelled by differences of temperatures and for steady chemical systems driven by differences of chemical potentials. Radiation engines are treated as systems described by Stefan–Boltzmann equations. We show that both chemical and electrochemical energy generators (fuel cells) satisfy similar principles of modeling and apply similar schemes of power evaluation as thermal machines. Based on a systematic application of Carnot controls (as variables which satisfy identically the internal entropy constraint) we construct, in fact, a methodologically novel, coherent approach to the family of power systems. Such approach has the virtue of reducing the number of controls and is superior to the traditional approach, which works with an enlarged number of traditional constrained controls. We believe that, because of its formal lucidity, the new approach also improves our understanding of the role of various energy transfer phenomena in power systems.
Author Stanisław Sieniutycz ZPR
Stanisław Sieniutycz,,
- Department of Separation Processes
Journal seriesInternational Journal of Heat and Mass Transfer, ISSN 0017-9310
Issue year2011
Vol54
No4
Pages938-948
Publication size in sheets0.5
Keywords in Englishfuel cells, maximum power, reduction of variables, second law, thermal and chemical converters
DOIDOI:10.1016/j.ijheatmasstransfer.2010.10.009
URL http://www.sciencedirect.com/science/article/pii/S0017931010005727
Languageen angielski
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Sieniutycz S. - Identification and selection....pdf 457.5 KB
Score (nominal)40
Publication indicators WoS Impact Factor [Impact Factor WoS]: 2011 = 2.407 (2) - 2011=2.913 (5)
Citation count*7 (2015-02-24)
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