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What is a simple system?
No full textWe discuss relations among properties of systems that consist of any amounts of constituents (including one particle), that have volume as the only parameter, and that are in thermodynamic equilibrium or stable equilibrium states. For large amounts of constituents, we introduce the concept of a simple system, and derive additional relations among properties
What is heat?
No full textWe define heat as a particular kind of nonwork interaction that involves only energy and entropy transfers, and that is entirely distinguishable from work. The existence of heat interaction is a consequence of the first and second laws of thermodynamics. The requirement that heat be entirely distinguishable from work implies strict conditions on the end states of the interacting systems, and guarantees a definite relation between such states and the energy and entropy transfers. We illustrate these conditions by using energy versus entropy graphs. Many experiences can be represented as heat interactions, including the exchanges between two black bodies at temperatures that differ infinitesimally. We discuss the latter point in a companion paper at this conference
What is a chemical equilibrium state?
No full textWe review the chemical equilibrium equations, and conclude that both their derivation and their meaning are problematic. We find that these equations can be established for a suitably defined simple system without chemical reactions
Entropy generation rate in a chemically reacting system
No full textFor a nonchemical-equilibrium state of an isolated system A that has r constituents with initial amounts na and that is subject to τ chemical reaction mechanisms, temperature, pressure, and chemical potentials cannot be defined. As time evolves, the values of the amounts of constituents vary according to stoichiometric relations. For such a state, we approximate the values of all the properties at time t with the corresponding properties of the stable equilibrium state of a surrogate system B consisting of the same constituents as A with amounts equal to Ni(t) but experiencing no chemical reactions. It is noteworthy that, for the first time, the Onsager relations are proven without reference to microscopic reversibility. In our view, if a process is irreversible, microscopic reversibility does not exist
Novel sequence of exposition of engineering thermodynamics
No full textWe present the foundations of thermodynamics in a novel sequence in which all basic concepts are defined in terms of well known mechanical ideas. Many definitions are new. The order of introduction of concepts is: system (constituents and parameters); properties; state; energy (without heat and work) and energy balance; classification of states in terms of time evolution; existence of stable equilibrium states; available energy; entropy (without heat and temperature) of any state (equilibrium or not) and entropy balance; properties of stable equilibrium states; temperature in terms of energy and entropy; chemical potentials; pressure; work; heat; applications of balances. This novel sequence not only generalizes the subject of thermodynamics to all systems (large or small) and all states (equilibrium and not equilibrium) but also avoids both the conceptual and definitional difficulties that have been recognized by so many teachers, and the confusion experienced by so many students
Thermodynamic derivations of conditions for chemical equilibrium and of Onsager reciprocal relations for chemical reactors
Get PDFQuantum thermodynamics. A new equation of motion for a general quantum system
No full textA novel nonlinear equation of motion is proposed for a general quantum system consisting of more than one distinguishable elementary constituent of matter. In the domain of idempotent quantummechanical state operators, it is satisfied by all unitary evolutions generated by the Schrödinger equation. But, in the broader domain of nonidempotent state operators not contemplated by conventional quantum mechanics, it generates a generally nonunitary evolution, it keeps the energy invariant and causes the entropy to increase with time until the system reaches a state of equilibrium or a limit cycle. © 1985 Società Italiana di Fisica
What is diffusion?
No full textIn earlier publications, heat Q← is defined as an interaction that is entirely distinguishable from work W→. The energy exchanged Q← is TQ times the entropy exchanged S←, where TQ is the almost common temperature of the interacting systems. Here, we define diffusion as another interaction that is entirely distinguishable from both work and heat, and that involves exchanges of energy, entropy, and amount of a constituent. It is an interaction between two systems A and B that pass through stable equilibrium states while their respective parameters remain fixed, and that have almost equal temperatures TA≈TB≈TD and almost equal total potentials μA≈μB≈μD of the diffusing constituent. The exchanges of entropy S→, energy E→, and amount of constituent n→ out of one system satisfy the relation S→ = E→-μDn→/TD. In the limit of n→ = 0, a diffusion interaction becomes heat
Quantum thermodynamics. A new equation of motion for a single constituent of matter
No full textA novel nonlinear equation of motion is proposed for quantum systems consisting of a single elementary constituent of matter. It is satisfied by pure states and by a special class of mixed states evolving unitarily. But, in general, it generates a nonunitary evolution of the state operator. It keeps the energy invariant and causes the entropy to increase with time until the system reaches a state of equilibrium or a limit cycle. © 1984 Società Italiana di Fisica
Electromagnetic radiation. A carrier of energy and entropy
No full textStarting from the properties of the electromagnetic radiation field at stable equilibrium, we derive expressions for the flows of energy and entropy between two black bodies at different temperatures, interacting only through electromagnetic radiation. We find that in general the interaction through radiation is nonwork but not heat. It is heat only if the temperature difference between the interacting systems is infinitesimal
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