.FCSys.Characteristics.BaseClasses.Characteristic.tauprime

Phase change interval (τ′) as a function of temperature and specific volume

Information

This function is based on the kinetic theory of gases under the following assumptions [Present1958]:

  1. The particles are smooth and rigid but elastic spheres with identical radii. This is the "billiard-ball" assumption, and it implies that the collisions are instantaneous and conserve kinetic energy.
  2. Between collisions, particles have no influence on one another.
  3. The mean free path, or average distance a particle travels between collisions, is much larger than the diameter of a particle.
  4. The properties carried by a particle depend only on those of the last particle with which it collided.
  5. The speeds of the particles follow the Maxwell-Boltzmann distribution.

Also, it is assumed that the Einstein relation applies.

Please see [Davies2013, Ch. 3] for a derivation of the rate of phase change from kinetic theory.

Although specific volume is an input to this function, the result is independent of specific volume.

Interface

function tauprime
  extends Modelica.Icons.Function;
  input Q.TemperatureAbsolute T = 298.15*U.K "Temperature" annotation(
    Dialog(__Dymola_label = "<html><i>T</i></html>"));
  input Q.VolumeSpecific v = 298.15*U.K/p0 "Specific volume" annotation(
    Dialog(__Dymola_label = "<html><i>v</i></html>"));
  output Q.TimeAbsolute tauprime "Phase change interval" annotation(
    Dialog(__Dymola_label = "<html>&tau;&prime;</html>"));
end tauprime;
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