absorptivity

(thermodynamics) The fraction of radiation absorbed by a surface to the total radiation incident on the surface.


quality

en-noun

quality (countable and uncountable, plural qualities)

US, father-bother merger, weak vowel merger

From Middle English qualite, from Old French qualité, from Latin quālitās, quālitātem, from quālis (“of what kind”), from Proto-Indo-European *kʷo- (“who, how”). Cicero coined qualitas as a calque to translate the Ancient Greek word ποιότης (poiótēs, “quality”), coined by Plato from ποῖος (poîos, “of what nature, of what kind”).

(thermodynamics) In a two-phase liquid–vapor mixture, the ratio of the mass of vapor present to the total mass of the mixture.

höyrypitoisuus

ratio of the mass of vapor present to the total mass of a two-phase liquid–vapor mixture


temperature

temperature (countable and uncountable, plural temperatures)

/ˈtɛm.pəɹ.əˌt͡ʃɚ/

/ˈtɛm.pəɹˌt͡ʃɚ/

/ˈtɛm.pɹəˌt͡ʃɚ/

[ˈtʰɛm.pʰəɹˌt͡ʃɚ]

[ˈtʰɛm.pʰɹəˌt͡ʃɚ]

Borrowed from Latin temperātūra (cf. also French température), from the past participle stem of tempero (“I temper”).

ջերմաստիճան

the temperature of the immediate environment

In consequence, macroscopic amounts of matter in thermal contact with one another tend to be at the same temperature, a fact of sufficient fundamental importance to merit belated designation as the Zeroth Law of Thermodynamics.

2000 September, Clinton D. Stoner, “Inquiries into the Nature of Free Energy and Entropy in Respect to Biochemical Thermodynamics”, in Entropy, volume 2, number 3, →DOI, →ISSN, pages 106–141:

(thermodynamics) A property of macroscopic amounts of matter that serves to gauge the average intensity of the random actual motions of the individually mobile particulate constituents.


entropy

entropy (countable and uncountable, plural entropies)

First attested in 1867, as the translation of German Entropie, coined in 1865 by Rudolph Clausius in analogy to Energie (“energy”), replacing the root of Ancient Greek ἔργον (érgon, “work”) by Ancient Greek τροπή (tropḗ, “transformation”)).

der

(thermodynamics, countable) A measure of the amount of energy in a physical system that cannot be used to do work.


irreversible

(thermodynamics) Incapable of being reversed to the original state without consumption of free energy and increase of entropy.


isopleth

From iso- + Ancient Greek πλῆθος (plêthos, “a great number”).

(thermodynamics) A line in a phase diagram indicating the same mole fraction.


isobar

From Ancient Greek ἴσος (ísos, “equal”) + βάρος (báros, “weight”), equivalent to iso- + bar-.

(thermodynamics) A set of points or conditions at constant pressure.

isobare

(thermodynamics) set of points at constant pressure


adiabatic

19th-century coinage (introduced by W. J. M. Rankine in the 1860s) based on Ancient Greek ἀδιάβατος (adiábatos, “impassable”), used of terrain (rivers, forests) by Xenophon, from ἀ- (a-, “not”) + διά (diá, “through”) + βατός (batós, “passable”), from βαίνω (baínō, “to go”).

The line drawn on the indicator diagram in the latter case has been named by Professor Rankine an Adiabatic line, because it is defined by the condition that heat is not allowed to pass through (διαβαίνειν) the vessel which confines the substance.

1871, James Clerk Maxwell, Theory of Heat, page 129:

Talk of dynamic compression and adiabatic gradients didn't carry as much weight as the certainty of its conscious intent.

2006, Thomas Pynchon, Against the Day, Vintage 2007, page 737:

(physics, thermodynamics, of a process) That occurs without gain or loss of heat (and thus with no change in entropy, in the quasistatic approximation).


enthalpy

en-noun

enthalpy (countable and uncountable, plural enthalpies)

From Ancient Greek ἐν- (en-, “in”) + θάλπω (thálpō, “to warm”). Coined by Dutch physicist Heike Kamerlingh Onnes, but first used in print by J. P. Dalton in 1909 in a paper titled "Researches on the Joule-Kelvin-effect, especially at low temperatures".

coin

H=U+pV, where H is enthalpy, U is internal energy, p is pressure, and V is volume.

(thermodynamics, physical chemistry) A measure of the heat content of a chemical or physical system.


thermodynamics

From thermo- + dynamics. First attested in the 1850s.

(physics) The science of the conversions between heat and other forms of energy.


thermodynamic equilibrium

en-noun

thermodynamic equilibrium (countable and uncountable, plural thermodynamic equilibria)

(physics) The state of a system in which its energy distribution is such that all parts of the system have the same temperature and no heat flows.


psychrometry

psychrometry (usually uncountable, plural psychrometries)

From psychro- (prefix meaning ‘cold’) + -metry (suffix forming nouns relating to measures and measurement), modelled after psychrometer.

confix

(meteorology, thermodynamics) Synonym of psychrometrics (“the measurement or study of the physical and thermodynamic properties of the atmosphere and its water vapour”)

psicrometria

synonym of psychrometrics — see also psychrometrics


transformity

en-noun

transformity (countable and uncountable, plural transformities)

Transformity increases with the increase in temperature between cold and hot reservoirs.

2001, Emerging Technologies in Airconditioning and Refrigeration, page 46:

Boggess (1994), studying the circulation of phosphorus in a Florida watershed, showed how the transformity zone of money circulation and market prices overlapped only the higher transformities of the circulation of phosphorus.

2004, Christina Howells, French Women Philosophers: A Contemporary Reader:

When an ecological network is expressed as a series of energy flows and transformation steps where the transformation steps are represented as Lindeman efficiencies, the resulting transformities represent trophic convergence and a measure of the amount of solar energy required to produce each level in the hierarchy.

2016, Sven E. Jørgensen, Handbook of Ecological Indicators for Assessment of Ecosystem Health, page 100:

(ecology, thermodynamics) The ratio of emergy to available energy.


reversible

/ɹəˈvɜː(ɹ)sɪbəl/

Probably from Middle French, equivalent to reverse + -ible.

(thermodynamics) Capable of returning to the original state without consumption of free energy and increase of entropy.


resistivity

resistivity (countable and uncountable, plural resistivities)

electrical resistivity
thermal resistance

LL-Q1860 (eng)-Flame, not lame-resistivity.wav

thermal conductivity
thermal conductivity#English

(thermodynamics) The reciprocal of thermal conductivity, having SI unit: m K W⁻¹


critical point

(thermodynamics) The temperature and pressure at which the vapour density of the gas and liquid phases of a fluid are equal, at which point there is no difference between gas and liquid.


specific heat

specific heat (countable and uncountable, plural specific heats)

specific heat capacity
specific heat capacity

(thermodynamics) An obsolete term for specific heat capacity.


diabatic

(physics, thermodynamics, of a process) That involves the gain or loss of heat (and thus a change in entropy).


isentropic

(thermodynamics, of process) Having a constant entropy


isentropic flow

isentropic flow (plural isentropic flows)

(thermodynamics) An idealised fluid flow in which entropy remains constant throughout the flow, or along a particular streamline.


isobaric

en-adj

isobaric (comparative more isobaric, superlative most isobaric)

more isobaric (comparative)
most isobaric (superlative)

(thermodynamics) (of a process) having a constant pressure throughout


chemical energy

en-noun

chemical energy (countable and uncountable, plural chemical energies)

(physical chemistry) The net potential energy liberated or absorbed during the course of a chemical reaction


heat engine

(thermodynamics) Any device which converts heat energy into mechanical work, by moving heat from a source to a sink.


combustion chamber

combustion chamber (plural combustion chambers)

An enclosed space, within a heat engine, in which the fuel is mixed and reacted with air or other oxidizing agent in a controlled manner.


psychrometrics

(meteorology, thermodynamics) The measurement or study of the physical and thermodynamic properties of the atmosphere and its water vapour.


incalescent

en-adj

incalescent (comparative more incalescent, superlative most incalescent)

more incalescent (comparative)
most incalescent (superlative)

From Latin incalescent-, stem of incalescens, present participle of incalescere, from in + calescere (“to grow warm”).

From some undreamed-of reservoir my body summoned up a gravity tank of incalescent libido.

1973, Kyril Bonfiglioli, Mordecais' Endgame (Don't Point That Thing at Me), page 119:


compressibility

en-noun

compressibility (countable and uncountable, plural compressibilities)

(thermodynamics) The product of pressure and molar volume divided by the product of the gas constant and the absolute temperature.


thermochemistry

(physical chemistry, thermodynamics) The study of the thermodynamics of chemical reactions.

termoquímica

the study of the thermodynamics of chemical reactions


Helmholtz free energy

For Hermann von Helmholtz, German physicist.

A=U-TS where A is Helmholtz free energy, U is internal energy, T is temperature, and S is entropy.

absolute temperature
absolute temperature

(physics, thermodynamics) A measure of the useful work obtainable from a constant temperature, constant volume thermodynamic system; more precisely, the difference between internal energy (of a system) and the product of its absolute temperature and entropy.

Helmholtz free energy
Hermann von Helmholtz

亥姆霍茲自由能 /亥姆霍兹自由能

measure of the useful work from a constant temperature system etc.


heat death of the universe

the heat death of the universe (canonical)

thermodynamic equilibrium
thermodynamic equilibrium

(cosmology, thermodynamics) A theoretical future state of the universe in which the universe attains thermodynamic equilibrium and a further increase of entropy is no longer possible.


isothermal

(thermodynamics) Of or pertaining to a process that takes place at constant temperature

isoterminen

of or pertaining to a process that takes place at constant temperature


specific heat capacity

specific heat capacity (plural specific heat capacities)

(thermodynamics) The heat capacity per unit mass.


free energy

Helmholtz free energy
Helmholtz free energy

(physical chemistry) The energy available in a particular chemical system to do useful work. In more detail:

Helmholtz free energy, A: the internal energy of a system minus the product of its entropy and absolute temperature.

Gibbs free energy, G: the enthalpy of a system minus the product of its entropy and absolute temperature.


Gibbs free energy

For Josiah Willard Gibbs, American physicist.

ΔG=ΔH-TΔS and G=H-TS where G is Gibbs free energy, H is enthalpy, T is temperature, and S is entropy.

(physics, physical chemistry, thermodynamics) The difference between the enthalpy of a system and the product of its entropy and absolute temperature: a measure of the useful work obtainable from a thermodynamic system at constant temperature and pressure.

energia lliure de Gibbs

difference between the enthalpy of a system and the product of its entropy etc.


heat sink

(thermodynamics) An object, system or environment that absorbs and dissipates heat from objects in thermal contact (either direct or radiant) with it.

(thermodynamics) A place toward which the heat moves in a system.

(thermodynamics) A material capable of absorbing heat.


diffuser

(thermodynamics) A mechanical device that is designed to control the characteristics of a fluid at the entrance to a thermodynamic open system.


anisothermal

anisothermal plasma

(thermodynamics) Of or pertaining to a system that is not in thermal equilibrium, that does not have a single fixed temperature.


closed system

(thermodynamics) A system that can exchange heat and work, but not matter, with its surroundings.


negentropy

negentropy (countable and uncountable, plural negentropies)

/ˌnɛɡˈɛntɹɒpi/

/ˌnɛɡˈɛntɹəpi/

Erwin Schrödinger
Léon Brillouin
What is Life?

From nega- + entropy.
A blend of negative + entropy, coined by the French physicist Léon Brillouin (1889–1969). The term negative entropy was introduced by the Austrian physicist Erwin Schrödinger (1887–1961) in his book What is Life? (1944, based on lectures delivered in February 1943).

An isolated system contains negentropy if it reveals a possibility for doing mechanical or electrical work: […] A tank of compressed gas in a room at atmospheric pressure, a vacuum tank in a similar room, a charged battery, any device that can produce high grade energy (mechanical work) or be degraded by some irreversible process (thermal conduction, electrical resistivity, friction, viscosity) is a source of negentropy. […] If a living organism needs food, it is only for the negentropy it can get from it, and which is needed to make up for the losses due to mechanical work done, or simple degradation processes in the living system. Energy contained in food does not really matter, since energy is conserved and never gets lost, but negentropy is the important factor.

1956 April, Brillouin, Léon, “Summary of Thermodynamics”, in Science and Information Theory, New York, N.Y.: Academic Press, →OCLC, section 2 (The Two Principles of Thermodynamics; Entropy and Negentropy), pages 116–117:

The same magnitude, but with a minus sign, i.e., the measure of macroscopic ordering, the measure of non-uniformity in the distribution of heat, the measure of the differences in temperature—temperature gradients—is called negentropy.

1977, Boris G. Kuznetsov, Philosophy of Optimism, Moscow: Progress Publishers, page 35:

Negentropy is the difference between the entropy of a system and the entropy of the same system at equilibrium (i.e., when it has its maximum possible entropy). Since entropy measures the amount of disorder, negentropy measures order.

2013, John E. Mayfield, “The Evolution of Complexity”, in The Engine of Complexity: Evolution as Computation, New York, N.Y.: Columbia University Press, →ISBN, page 277:

(thermodynamics) The difference between the entropy of a system and the maximum possible entropy of the same system.


thermal contact

When objects are brought into thermal contact, the macroscopic properties may initially change but after some time no further changes will occur.

2004, Bruno Linder, chapter 2, in Thermodynamics and Introductory Statistical Mechanics, →ISBN, page 13:

(thermodynamics) A state in which two or more systems can exchange thermal energy.


isoenthalpic

(thermodynamics, of a process) Having constant enthalpy


heat dump

(thermodynamics) A structure or environment into which waste heat can be transferred


disgregation

disgregation (countable and uncountable, plural disgregations)

Rudolf Clausius
disgregation
second law of thermodynamics

Borrowed from Latin disgregātiō, from dis- (“apart”) + grex (“flock”).
The thermodynamics sense was introduced in 1862 by German physicist Rudolf Clausius in his formulation of what is now called the second law of thermodynamics.

1868, R. Clausius, On the Second Fundamental Theorem of the Mechanical Theory of Heat, [1867, Lecture to the German Scientific Association], The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, page 408,
The disgregation of a body is consequently, among the three states of aggregation, least in the solid state, greater in the liquid state, and greatest of all in the gaseous state. In the last condition it can still be increased by the molecules separating further from each other—that is, by the gas expanding to a larger volume. In like manner, the decomposition of a chemically compound body into its elements is in general accompanied by an increase of disgregation.
By help of this conception the effect of heat can be simply expressed by saying that heat tends to increase the disgregation of bodies.

The gas, however, may experience the same changes of volume and disgregation in another manner.

1880, Robert Röntgen, The Principles of Thermodynamics: With Special Applications to Hot-air, Gas and Steam Engines, J. Wiley, page 95:

Since the increase of disgregation is the action by means of which heat performs work, it follows that the quantity of work must bear a definite ratio to the quantity by which the disgregation is increased; we will therefore fix the still arbitrary determination of the magnitude of disgregation so that, at any given temperature, the increase of disgregation shall be proportional to the work which the heat can thereby perform.

2016, Kerry Kuehn, A Student's Guide Through the Great Physics Texts, Volume IV: Heat, Atoms and Quanta, Springer, page 84:

(thermodynamics, obsolete or historical) A measure of the separation of the particles of a system; an early formulation of entropy.


Dühring's rule

(thermodynamics) An empirical rule stating that a linear relationship exists between the temperatures at which two solutions exert the same vapor pressure.


combined cycle

(thermodynamics) using multiple thermodynamic cycles so that the overall effect is greater than the sum of the parts


antientropic

en-adj

antientropic (comparative more antientropic, superlative most antientropic)

more antientropic (comparative)
most antientropic (superlative)


athermic

athermic (comparative more athermic, superlative most athermic)

more athermic (comparative)
most athermic (superlative)

/ˌeɪˈθɜɹmɪk/

resistant to heat passing through; heat-resistant, heatproof

(medicine) without an increase in temperature

(physical chemistry, of a chemical reaction) involving no enthalpy exchange


mesostate

From meso- + state. Sense 4 possibly purely in analogy with anastate and catastate.

If the manipulation is slow enough, and the driving connects different mesostates, then jumps between states in the same mesostate satisfy the detailed balance condition.

2021, Luca Peliti, Simone Pigolotti, Stochastic Thermodynamics: An Introduction, page 42:

Even though we said the mesostates x are relatively stable, after a very long time they will also eventually thermalize (unless we additionally protect them).

2022, Philipp Strasberg, Quantum Stochastic Thermodynamics, page 51:

For systems with metastable conformations, a trajectory initiated in one mesostate spends a (potentially) long time sampling microstates in that mesostate before overcoming the energy barrier to sample the other mesostate, and due to the timescale separateion between the simulation timestep and reaction transitions, it becomes impractical to compute free energies via a brute-force approach.

2023, Miranda Louwerse, Efficient Control and Spontaneous Transitions, page 31:

(thermodynamics) A composite state of a physical system that is determined by the overall configuration of many microstates; e.g. the heat of a substance (mesostate), which is made up of the aggregate of motions of many molecules (microstate).


autothermic

(physical chemistry, of a reaction) exothermic to an extent that the generated heat sustains the reaction


closed feedwater heater

en-noun

closed feedwater heater (plural closed feedwater heaters)

(engineering, thermodynamics) A feedwater heater in which the two fluid streams do not mix.


open feedwater heater

open feedwater heater (plural open feedwater heaters)

(engineering, thermodynamics) A feedwater heater in which the two fluid streams mix together.


ectropy

ectropy (countable and uncountable, plural ectropies)

“This term was suggested by W. V. Quine in discussions following this symposium: Entropy, he pointed out, is Greek for turning in; the opposite term should therefore be the Greek for turning out, namely ectropy. Since the coaction cardioid literally turns in and out of the circle of reference, his short, elegant term is used throughout.”

(thermodynamics) The overall increase in the organization of a system


effusivity

thermal conductivity
thermal conductivity

(thermodynamics) A measure of a material's ability to exchange thermal energy with its surroundings; the square root of the product of its thermal conductivity and its volumetric heat capacity.


information engine

information engine (plural information engines)

(thermodynamics) A theoretical engine that converts information into energy for use in work, decreasing heat entropy in the process.


Joule's cycle

(thermodynamics) The cycle for the air engine proposed by Joule. In it air is taken by a pump from a cold chamber and compressed adiabatically until its pressure is equal to that of the air in a hot chamber, into which it is then delivered, thereby displacing an equal amount of hot air into the engine cylinder. Here it expands adiabatically to the temperature of the cold chamber into which it is finally exhausted. This cycle, reversed, is used in refrigeration.


Carnot's cycle

(thermodynamics) An ideal heat-engine cycle in which the working fluid goes through four successive operations: (1) isothermal expansion to a desired point; (2) adiabatic expansion to a desired point; (3) isothermal compression to such a point that (4) adiabatic compression brings it back to its initial state.

कार्नो चक्र

an ideal heat-engine cycle in which the working fluid goes through four successive operations


pseudoreduced

LL-Q1860 (eng)-Flame, not lame-pseudoreduced.wav

(thermodynamics) simplified by using pseudocritical parameters


monobaric

(thermodynamics) Having constant external pressure


anentropy

anentropy (countable and uncountable, plural anentropies)

Treivus has pointed out that the anentropy, apart from a constant factor (the universal gas constant) is equal to the chemical affinity for one componenent in a themodynamic system.

2001, Automatic Documentation and Mathematical Linguistics, page 15:

(physical chemistry, thermodynamics, countable and uncountable) A measure of the purity or chemical affinity in a thermodynamic system.


subextensive

According to Tsallis (1988), the entropy was extensive for T = 1, superextensive for t < 1 and subextensive for t > 1.

2000, Roman Teisseyre, Eugeniusz Majewski, Earthquake Thermodynamics and Phase Transformation in the Earth's Interior, →ISBN:

(thermodynamics) Having a combined system entropy that is less than the sum of the entropies of the independent systems.


Joule-Thomson effect

Joule-Thomson effect (plural Joule-Thomson effects)

Named after James Prescott Joule and William Thomson, 1st Baron Kelvin, who discovered it in 1852.

(thermodynamics) The temperature change of a real gas or liquid (as differentiated from an ideal gas) when it is forced through a valve or porous plug while kept insulated so that no heat is exchanged with the environment.


ergonal

en-adj

ergonal (comparative more ergonal, superlative most ergonal)

more ergonal (comparative)
most ergonal (superlative)

From ergon (“work”) + -al (“pertaining to”), in analogy to thermal (“pertaining to heat”), coined by John Tyndall as "thermal and ergonal content" (1867, p. 357) in the translation of Rudolf Clausius' phrase Wärme- und Werkinhalt (1865).

(thermodynamics) pertaining to mechanical work


entransy

en-noun

entransy (countable and uncountable, plural entransies)

Blend of en[ergy] + trans[fer] + [abilit]y, introduced on 26 February 2007 by a research group at Tsinghua University led by Professor Guo as a basis for optimizing heat transfer processes (Guo, Zeng-Yuan; Zhu, Hong-Ye; Liang, Xin-Gang. Entransy—a physical quantity describing heat transfer ability International Journal of Heat and Mass Transfer, no. 50, pp. 2545–56, available online 26 February 2007). A descriptive concept of entransy, but without using the term ‘entransy’, was first proposed by Professor Guo's group in February 2003 as ‘heat transport potential capacity’.

blend

A new physical quantity, E#95;h#61;#92;frac#123;1#125;#123;2#125;Q#95;#123;vh#125;T [where Qᵥₕ = McᵥT is the heat stored in an object; M is the mass; cᵥ is the specific heat capacity at constant volume; T is the temperature], has been identified as a basis for optimizing heat transfer processes in terms of the analogy between heat and electrical conduction. This quantity, which will be referred to as entransy, corresponds to the electric energy stored in a capacitor.

2007, Zeng-Yuan Guo, Hong-Ye Zhu, Xin-Gang Liang, “Entransy—a physical quantity describing heat transfer ability”, in International Journal of Heat and Mass Transfer, number 50, page 2545:

The concept of ‘entransy’, a product of heat and temperature, originally called ‘heat transport potential capacity’, was introduced in 2003, as analogy to product of electrical charge and voltage, as well as other similar quantities. The concept has been extended to entransy property, as integral product of ‘stored heat’ and temperature, #92;frac#123;1#125;#123;2#125;Mc#95;vT² [where M is mass; cᵥ is specific heat capacity at constant volume; T is temperature], thus representing quantity and quality of stored heat, or thermal energy in isochoric processes without work interactions.

2017, Milivoje Kostic, “Entransy concept and controversies: A critical perspective within elusive thermal landscape”, in International Journal of Heat and Mass Transfer, number 115, page 340:

(thermodynamics) Half the product of internal thermal energy and temperature. For a given temperature difference, maximization of the entransy dissipation results in the maximum heat flux and thus corresponds to the optimal heat conduction performance.


thermal mass

en-noun

thermal mass (countable and uncountable, plural thermal masses)

(thermodynamics) Synonym of heat capacity


thermomass

thermomass (countable and uncountable, plural thermomasses)


Clausius-Clapeyron relation

Clausius-Clapeyron relation (plural Clausius-Clapeyron relations)

Named after Rudolf Clausius and Émile Clapeyron.

(thermodynamics) A way of characterizing a discontinuous phase transition between two phases of matter of a single constituent. It gives the slope of the tangents to the "coexistence curve" that separates the two phases on a pressure-temperature diagram.


van der Waals gas

van der Waals gas (plural van der Waals gases)

van der Waals equation
van der Waals equation

(thermodynamics) a gas which follows the van der Waals equation.

van der Waals-Gas

gas following the van der Waals equation


adiathermal

(thermodynamics) adiabatic; not involving transmission of heat


Big Freeze

heat death of the universe
heat death of the universe#English

(cosmology) Synonym of heat death of the universe.


Legendre transformation

Legendre transformation (plural Legendre transformations)

Adrien-Marie Legendre
Legendre transformation

Named after Adrien-Marie Legendre (1752–1852), a French mathematician.

(thermodynamics) A relation between internal energy (expressed in terms of volume and entropy) and enthalpy (replacing volume with pressure), or between internal energy and Helmholtz free energy (replacing entropy with temperature), or between enthalpy and Gibbs free energy (replacing entropy with temperature), or between internal energy and Gibbs free energy (replacing volume with pressure and entropy with temperature), or between Helmholtz free energy and Gibbs free energy (replacing volume with pressure).


ectoentropic

Outside of or defying thermodynamic entropy.

Not in accordance with the laws of thermodynamics.


molar heat capacity

molar heat capacity (plural molar heat capacities)

(thermodynamics) The heat capacity of a given substance divided by its amount, measured in moles.

摩爾熱容 /摩尔热容

heat capacity of one mole of the substance


Carnot cycle

One of the virtues of the fuel battery is said to be that, unlike all heat engines, it is not limited in theoretical efficiency by the Carnot cycle and its practical efficiency lies in the 60 to 80 per cent range; a point often forgotten, however, is that if hydrogen has to be made, the Carnot cycle efficiency does apply, because this is a heat process.

1962 February, “Talking of Trains: Fuel battery locomotives?”, in Modern Railways, page 87:


Bekenstein bound

Bekenstein bound (plural Bekenstein bounds)

(thermodynamics) An upper limit on the thermodynamic entropy, or Shannon entropy, that can be contained within a given finite region of space which has a finite amount of energy—or conversely, the maximal amount of information required to perfectly describe a given physical system down to the quantum level.


FPSE

Researchers in ORNL's Engineering Technology Division have developed the linear harmonic analysis (LHA) method, which provides insights into both the thermodynamics and dynamics of free-piston Stirling engines (FPSEs).

1990, Tech Notes, U.S. Department of Commerce, National Technical Information Service, Center for the Utilization of Federal Technology, page 146:

free-piston Stirling engine
w:free-piston Stirling engine

(thermodynamics) Initialism of free-piston Stirling engine.


sand battery

(thermodynamics, industrial planning) A thermal storage battery which uses sand as the storage medium.


acentric factor

acentric factor (plural acentric factors)

(thermodynamics) A conceptual number, denoted by ω, useful in the description of fluids, derived from the reduced saturation vapor pressure and the reduced temperature.


Ehrenfest model

Ehrenfest model (plural Ehrenfest models)

Named after Paul Ehrenfest and Tatiana Ehrenfest-Afanaseva.

(thermodynamics) A model of diffusion used to explain the second law of thermodynamics, considering a number of particles in two containers, which independently change container at a certain rate.

Paul Ehrenfest
Tatiana Ehrenfest-Afanaseva


Trouton's rule

(thermodynamics) A rule stating that the entropy of vaporization is almost the same value, about 85–88 J/(K·mol), for various kinds of liquids at their boiling points.


Gibbs-Helmholtz equation

the Gibbs-Helmholtz equation (canonical)

Named after Hermann von Helmholtz (who introduced it in an 1882 paper) and Josiah Willard Gibbs.

(thermodynamics) An equation for calculating changes in the Gibbs free energy of a system as a function of temperature: ((∂(G/T))/(∂T))ₚ=-H/(T²), where H is the enthalpy, T the absolute temperature and G the Gibbs free energy of the system, all at constant pressure p.


Thomson effect

Named after William Thomson, Lord Kelvin.

(thermodynamics) The phenomenon where, when in the presence of a gradient in the Seebeck coefficient, driving a current through this gradient produces a continuous version of the Peltier effect.


Seebeck coefficient

Seebeck coefficient (plural Seebeck coefficients)


Gibbs-Thomson effect

Gibbs-Thomson effect (plural Gibbs-Thomson effects)

Named after Josiah Willard Gibbs and J. J. Thomson.

(thermodynamics) The variations in vapor pressure or chemical potential across a curved surface or interface.


Gibbs-Thomson equation

Gibbs-Thomson equation (plural Gibbs-Thomson equations)

(thermodynamics) An equation for the structural depression in the freezing point or melting point in a confined geometry, in its compact form: Δ,T_m(x)=(k_GT)/x, where the Gibbs–Thomson coefficient k_GT assumes different values for different liquids and different interfacial geometries (e.g. spherical, cylindrical or planar).


Bejan number

(thermodynamics) A dimensionless number: the ratio of heat transfer irreversibility to total irreversibility due to heat transfer and fluid friction: Be=(̇S'_(gen,,ΔT))/(̇S'_(gen,,ΔT)+̇S'_(gen,,Δp)), where ̇S'_(gen,,ΔT) is the entropy generation contributed by heat transfer and ̇S'_(gen,,Δp) is the entropy generation contributed by fluid friction.


Carnot's law

Carnot's theorem
Carnot's theorem#English

(thermodynamics) Synonym of Carnot's theorem


Carnot's theorem

(thermodynamics) A theorem for the maximum efficiency obtainable from a heat engine.