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In continuum mechanics and thermodynamics, a control volume (CV) is a mathematical abstraction employed in the process of creating mathematical models of physical processes. In an inertial frame of reference , it is a fictitious region of a given volume fixed in space or moving with constant flow velocity through which the continuuum (a ...
Examples are internal energy, enthalpy, Helmholtz free energy, Gibbs free energy, thermodynamic temperature, and entropy. For a given body, of a given chemical constitution, when its thermodynamic state has been fully defined by its pressure and volume, then its temperature is uniquely determined.
Therefore, gas volume may alternatively be expressed excluding the humidity content: V d (volume dry). This fraction more accurately follows the ideal gas law. On the contrary, V s (volume saturated) is the volume a gas mixture would have if humidity was added to it until saturation (or 100% relative humidity).
= , where k B is the Boltzmann constant, and Ω denotes the volume of macrostate in the phase space or otherwise called thermodynamic probability. d S = δ Q T {\displaystyle dS={\frac {\delta Q}{T}}} , for reversible processes only
Non-equilibrium thermodynamics is a branch of thermodynamics that deals with systems that are not in thermodynamic equilibrium. Most systems found in nature are not in thermodynamic equilibrium because they are not in stationary states, and are continuously and discontinuously subject to flux of matter and energy to and from other systems.
Consider a gas in cylinder with a free floating piston resting on top of a volume of gas V 1 at a temperature T 1. If the gas is heated so that the temperature of the gas goes up to T 2 while the piston is allowed to rise to V 2 as in Figure 1, then the pressure is kept the same in this process due to the free floating piston being allowed to ...
A thermodynamic cycle consists of linked sequences of thermodynamic processes that involve transfer of heat and work into and out of the system, while varying pressure, temperature, and other state variables within the system, and that eventually returns the system to its initial state. [1]
For thermodynamics, a natural process is a transfer between systems that increases the sum of their entropies, and is irreversible. [2] Natural processes may occur spontaneously upon the removal of a constraint, or upon some other thermodynamic operation , or may be triggered in a metastable or unstable system, as for example in the ...