Setting Up Analysis Plots

Create plots to analyse the results of the simulation.

It is also instructive to observe quantities of interest as convergence is approached. You set up plots of Axis Subcooling and Wall Superheat which can be compared directly with data given by Bartolemei (1967) ([971]). An important feature of the model is the automatic partitioning of the applied wall heat flux into three components (liquid convection, evaporation, and vapor convection). This partitioning is presented as a Wall Heat Flux plot. A number of other submodel quantities, such as bubble size, are of interest to researchers in this field.

For convenience, the analysis plots for this tutorial can be set up by running a macro.

To set up the analysis plots:

  1. Select File > Macro > Play Macro.
  2. In the Open dialog, navigate to your working directory and select wb_setupAnalysisPlots.java.
  3. Click Open to run the macro.

Many plots present results on the wall or on the axis against height. However, because of uncertainty in the exact location and conditions at the start of the heated section, a comparison with Bartolemei (1967) ([971]) or Bartolemei (1982) ([972]) is best done by using thermodynamic quality as a non-dimensional scale. Thermodynamic quality is easily related to height from the heat balance.

The definition of thermodynamic quality is:

xth=hhLSAThLV

where h is the mixture enthalpy as calculated by this heat balance:

h=hLIN+4qzGD

For convenience, the thermodynamic quality has been set up as a user field function.

The components of heat flux between the wall and the liquid, between the wall and the vapor, and between the wall and the evaporating interface, are available as standard field functions. These field functions are suffixed with the relevant phase or interaction name:

  • Boundary Heat Flux of Liquid
  • Boundary Heat Flux of Vapor
  • Boundary Heat Flux of Liquid Vapor Interface

Boundary heat fluxes follow the sign convention in that they are positive when directed outwards. This sign convention is corrected for the presentation of the Wall Heat Flux plot.

Wall superheat is defined as the wall temperature excess over the saturation temperature. It is defined here as a user field function. The wall temperature itself is obtained by evaluating the temperature of either phase at the wall.

Liquid subcooling is defined as the saturation temperature less the liquid temperature. To ensure that this value can also be plotted at the wall, the Ignore Boundary Values option is activated when the field function is created. This setting ensures that the liquid temperature in the cell next to the wall is used rather than the wall temperature.