Elias P. Gyftopoulos

Thermionic energy conversion

Thermionic conversion is a method for converting heat directly into electrical energy. Unlike the conventional indirect methods for generating electricity from heat sources, no intermediate form of energy is required, and no working fluid--except the flow of the electrical charges themselves--are involved in the process. And unlike other direct conversion methods, there is no need for access to natural light (as required for photocells) or special chemicals (as required for fuel cells)--there are many available sources of thermal energy that can be utilized.The phenomenon of thermionic emission has been known since the late nineteenth century, but for many decades only sporadic and disconnected efforts were made to harness it for useful work. In the past few years, however, its potential for practical application has been recognized, and much research has now been done that supports the prospect that thermionic energy conversion will find increasing utility over the coming years. The purpose of this volume--the first of two--is to summarize what is known about the process for the benefit of a wide audience of technical readers who are not familiar with its potentials as well as to serve as a reference for those already in the field. (The second volume, now in preparation, will develop the more advanced scientific aspects of the process, describe the experience with actual hardware now operational, and estimate the limits of parameters that are unlikely to be exceeded in the near future.)Volume One opens with an introductory chapter that classifies thermionic converters by type and specifies their performance characteristics. The second chapter investigates the devices on a theoretical level by analyzing the ideal performance of the simplest configuration, which consists of a heated electrode and a collector electrode connected to a heat sink, the two separated and enclosed in an evacuated or vapor-filled space, and connected externally through an electrical load.The final two chapters take up, respectively, vacuum and vapor converters. The vacuum devices considered are diode, magnetic triode, and electrostatic triode converters; the vapor devices taken up include such converter configurations as cesium diodes, low- and high-pressure diodes, cesium diodes with additives, supplemented vapor diodes, ion emission triodes, and arc triodes.

Work Function Variation of Metals Coated by Metallic Films

A theoretical correlation is derived to account for the variation of the work function of refractory metals coated by metallic films for all degrees of coverage. This correlation is based on an extension of the concept of electronegativity to composite surfaces and use of Paulings rule about electronegativity and dipole moment of complex molecules. A series of theoretical curves is given for different crystallographically ideal surfaces of refractory metals such as W, Mo, and Ta coated by Cs, Sr, Ba, and Th.The derived correlation is compared with available experimental data for which the experimenters specify the exact conditions under which the experiment is performed and excellent agreement between theory and experiment is established.It is shown for the first time that the maximum work function variation does not necessarily always occur either when a full monolayer is reached or at a definite fractional coverage. The exact position of the maximum variation is a function of the adsorbate and substrat...

A Unified Quantum Theory of Mechanics and Thermodynamics. Part I. Postulates

A unified axiomatic theory that embraces both mechanics and thermodynamics is presented in three parts. It is based on four postulates; three are taken from quantum mechanics, and the fourth is the new disclosure of the existence of quantum states that are stable (Part I). For nonequilibrium and equilibrium states, the theory provides general original results, such as the relation between irreducible density operators and the maximum work that can be extracted adiabatically (Part IIa). For stable equilibrium states, it shows for the first time that the canonical and grand canonical distributions are the only stable distributions (Part IIb). The theory discloses the incompleteness of the equation of motion of quantum mechanics not only for irreversible processes but, more significantly, for reversible processes (Part IIb). It establishes the operational meaning of an irreducible density operator and irreducible dispersions associated with any state, and reveals the relationship between such dispersions and the second law (Part III).

Markov Processes for Reliability Analyses of Large Systems

This paper presents a methodology for calculating the time-dependent reliability of a large system consisting of s-dependent components. A Markov-chain model is used and the numerical difficulties associated with large transition-probability matrices are reduced by a systematic ordering of the system states. A technique is also presented for the systematic merging of processes corresponding to systems exhibiting symmetries.

Fundamentals of analyses of processes

A number of popular restrictions on the range of validity of thermodynamics are reviewed and found to be invalid, and the separation into first law and second law analyses of a process is discussed and shown to be unjustifiable and misleading. As a result of these reviews and discussions, we conclude that: (i) we should stop claiming that we can perform first and second law analyses separately; (ii) in every process, we should use at least both the energy and entropy balances simultaneously; and (iii) we should recognize the dynamic character of thermodynamics and the need to include in our analyses states that are not thermodynamic equilibrium.

Markovian Reliability Analysis Under Uncertainty with an Application on the Shutdown System of the Clinch River Breeder Reactor

A methodology for the assessment of the uncertainties about the reliability of nuclear reactor systems described by Markov models is developed, and the uncertainties about the probability of loss of coolable core geometry (LCG) of the Clinch River Breeder Reactor (CRBR) due to shutdown system failures, are assessed. Uncertainties are expressed by assuming the failure rates, the repair rates and all other input variables of reliability analysis as random variables, distributed according to known probability density functions (pdf). The pdf of the reliability is then calculated by the moment matching technique. Two methods have been employed for the determination of the moments of the reliability: the Monte Carlo simulation; and the Taylor-series expansion. These methods are adopted to Markovian problems and compared for accuracy and efficiency.

A unified quantum theory of mechanics and thermodynamics. Part IIb. Stable equilibrium states

Part IIb presents some of the most important theorems for stable equilibrium states that can be deduced from the four postulates of the unified theory presented in Part I. It is shown for the first time that the canonical and grand canonical distributions are the only distributions that are stable. Moreover, it is shown that reversible adiabatic processes exist which cannot be described by the dynamical equation of quantum mechanics. A number of conditions are discussed that must be satisfied by the general equation of motion which is yet to be discovered.

A unified quantum theory of mechanics and thermodynamics. Part IIa. Available energy

AbstractPart II of this three-part paper presents some of the most important theorems that can be deduced from the four postulates of the unified theory discussed in Part I. In Part IIa, it is shown that the maximum energy that can be extracted adiabatically from any system in any state is solely a function of the density operator

An Ionization Process in a Low‐Energy Cesium Plasma

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