Enzo Zanchini

Rigorous and General Definition of Thermodynamic Entropy

The physical foundations of a variety of emerging technologies --- ranging from the applications of quantum entanglement in quantum information to the applications of nonequilibrium bulk and interface phenomena in microfluidics, biology, materials science, energy engineering, etc. --- require understanding thermodynamic entropy beyond the equilibrium realm of its traditional definition. This paper presents a rigorous logical scheme that provides a generalized definition of entropy free of the usual unnecessary assumptions which constrain the theory to the equilibrium domain. The scheme is based on carefully worded operative definitions for all the fundamental concepts employed, including those of system, property, state, isolated system, environment, process, separable system, system uncorrelated from its environment, and parameters of a system. The treatment considers also systems with movable internal walls and/or semipermeable walls, with chemical reactions and/or external force fields, and with small numbers of particles. The definition of reversible process is revised by introducing the new concept of scenario. The definition of entropy involves neither the concept of heat nor that of quasistatic process; it applies to both equilibrium and nonequilibrium states. The role of correlations on the domain of definition and on the additivity of energy and entropy is discussed: it is proved that energy is defined and additive for all separable systems, while entropy is defined and additive only for separable systems uncorrelated from their environment; decorrelation entropy is defined. The definitions of energy and entropy are extended rigorously to open systems. Finally, to complete the discussion, the existence of the fundamental relation for stable equilibrium states is proved, in our context, for both closed and open systems.

Transient Heat Transfer from an Offshore Buried Pipeline during Start-up Working Conditions

The 2D heat transfer from offshore, completely buried pipelines is studied with reference to transient working conditions. In particular, the start-up case is considered (i.e., the case of a pipeline initially at equilibrium with the surrounding soil). Two different start-up cases are investigated: the step-rising case and the smooth-rising case. (In the latter, the steady-state wall temperature is reached in a finite time.) The energy balance equation is written in a dimensionless form and solved numerically by means of a finite element method. The dimensionless temperature field in the soil and the thermal power exchanged per unit length by the pipeline with the soil are determined. A comparison with a simpler one-dimensional model of the phenomenon (“extra-soil layer” approximation) is performed.

Correct interpretation of two experiments on the transverse Doppler shift

Consider a light source S, an observer O at rest with respect to S and an observer O′ in motion with respect to O. Suppose that, at a given instant of time, O and O′ are in the same position and a light signal produced by S strikes both of them. Two important special cases may occur: either the motion of the source is orthogonal to the straight line that interconnects source and observers, or the motion of the source is orthogonal to the direction of the light signal, as judged by O′. In the first case, the Doppler shift perceived by O′ is blue; in the second it is red. In the literature, the first condition is often confused with the second; this confusion caused the misinterpretation of two important experiments (Hay et al 1960 Phys. Rev. Lett. 4 165–6; Kundig 1963 Phys. Rev. 129 2371–5), where the first configuration occurs, but the results were interpreted as evidence of a red shift. In this paper, it is proved that the Doppler shift occurring in these experiments is blue, and that only a blue shift is compatible with the outcomes of the experiment performed by Kundig.

Design of a Nearly Zero Energy One-Family House in North-Centre Italy

The thermal design of a nearly zero energy one-family house, in North-Centre Italy, is described. The house has a timber frame, a wood-fiber thermal insulation for the roof and a wood-fiber plus YTONG blocks thermal insulation for the lateral walls. Forced ventilation with high efficiency heat recovery is employed. Heating and cooling is provided by an air-to-water heat pump connected to floor radiant panels. Domestic Hot Water is supplied by a thermal solar collector and a heat pump for DHW. The electric energy for the heat pumps and for the forced ventilation system is supplied by PV collectors, which provide also most of the electric energy for lighting and appliances. The thermal design is based on dynamic simulations performed through the code TRNSYS 16.

Rigorous Axiomatic Definition of Entropy Valid Also for Non‐Equilibrium States

We present a rigorous logical scheme for the definition of entropy, based on operative definitions of all the concepts employed, with all assumptions declared explicitly. Our treatment is an equivalent variation of the general definition of entropy given in E.P. Gyftopoulos and G.P. Beretta, Thermodynamics. Foundations and Applications, Dover, Mineola, 2005. However, here we outline the minimal set of definitions and assumptions required to construct the same definition by the most direct and essential sequence of logical steps.