- Thermodynamic process
A thermodynamic process may be defined as the energetic evolution of a
thermodynamic systemproceeding from an initial state to a final state. Paths through the space of thermodynamic variables are often specified by holding certain thermodynamic variables constant. It is useful to group these processes into pairs, in which each variable held constant is one member of a conjugate pair.
The pressure-volume conjugate pair is concerned with the transfer of mechanical or dynamic energy as the result of work.
isobaric processoccurs at constant pressure. An example would be to have a movable piston in a cylinder, so that the pressure inside the cylinder is always at atmospheric pressure, although it is isolated from the atmosphere. In other words, the system is dynamically connected, by a movable boundary, to a constant-pressure reservoir.
isochoric processis one in which the volume is held constant, meaning that the work done by the system will be zero. It follows that, for the simple system of two dimensions, any heat energy transferred to the system externally will be absorbed as internal energy. An isochoric process is also known as an isometric process or an isovolumetric process. An example would be to place a closed tin can containing only air into a fire. To a first approximation, the can will not expand, and the only change will be that the gas gains internal energy, as evidenced by its increase in temperature and pressure. Mathematically, . We may say that the system is dynamically insulated, by a rigid boundary, from the environment.
The temperature-entropy conjugate pair is concerned with the transfer of thermal energy as the result of heating.
isothermal processoccurs at a constant temperature. An example would be to have a system immersed in a large constant-temperature bath. Any work energy performed by the system will be lost to the bath, but its temperature will remain constant. In other words, the system is thermally connected, by a thermally conductive boundary to a constant-temperature reservoir.
adiabatic processis a process in which there is no energy added or subtracted from the system by heating or cooling. For a reversible process, this is identical to an isentropic process. We may say that the system is thermally insulated from its environment and that its boundary is a thermal insulator. If a system has an entropy which has not yet reached its maximum equilibrium value, the entropy will increase even though the system is thermally insulated.
isentropic processoccurs at a constant entropy. For a reversible process this is identical to an adiabatic process. If a system has an entropy which has not yet reached its maximum equilibrium value, a process of cooling may be required to maintain that value of entropy.
Any of the
thermodynamic potentials may be held constant during a process. For example:
isenthalpic processintroduces no change in enthalpyin the system.
The above have all implicitly assumed that the boundaries are also impermeable to particles. We may assume boundaries that are both rigid and thermally insulating, but are permeable to one or more types of particle. Similar considerations then hold for the (
chemical potential)-( particle number) conjugate pairs.
Wikimedia Foundation. 2010.
Look at other dictionaries:
thermodynamic process — termodinaminis vyksmas statusas T sritis Standartizacija ir metrologija apibrėžtis Termodinaminių parametrų pokyčio sukeltas sistemos būsenos kitimas. atitikmenys: angl. thermodynamic process vok. thermodynamischer Prozess, m rus.… … Penkiakalbis aiškinamasis metrologijos terminų žodynas
thermodynamic process — termodinaminis procesas statusas T sritis chemija apibrėžtis Termodinaminių parametrų pokyčio sukeltas sistemos būsenos kitimas. atitikmenys: angl. thermodynamic process rus. термодинамический процесс … Chemijos terminų aiškinamasis žodynas
thermodynamic process — termodinaminis vyksmas statusas T sritis fizika atitikmenys: angl. thermodynamic process vok. thermodynamischer Prozeß, m rus. термодинамический процесс, m pranc. processus thermodynamique, m … Fizikos terminų žodynas
thermodynamic process — termodinaminis procesas statusas T sritis Energetika apibrėžtis Makroskopinės sistemos pradinės būsenos virsmas galine būsena, būsenos kitimas dėl sistemos termodinaminių parametrų kitimo. atitikmenys: angl. thermodynamic process vok.… … Aiškinamasis šiluminės ir branduolinės technikos terminų žodynas
thermodynamic process — Смотри термодинамический процесс … Энциклопедический словарь по металлургии
Thermodynamic cycle — Thermodynamics … Wikipedia
Thermodynamic system — A thermodynamic system is a precisely defined macroscopic region of the universe, often called a physical system, that is studied using the principles of thermodynamics. All space in the universe outside the thermodynamic system is known as the… … Wikipedia
Process — A process is a naturally occurring or designed sequence of changes of properties or attributes of an object or system. More precisely, and from the most general systemic perspective, every process is representable as a particular trajectory (or… … Wikipedia
Thermodynamic temperature — is the absolute measure of temperature and is one of the principal parameters of thermodynamics. Thermodynamic temperature is an “absolute” scale because it is the measure of the fundamental property underlying temperature: its null or zero point … Wikipedia
Thermodynamic databases for pure substances — Thermodynamic databases contain information about thermodynamic properties for substances, the most important being enthalpy, entropy, and Gibbs free energy. Numerical values of these thermodynamic properties are collected as tables or are… … Wikipedia