An optical interference method was developed for measuring rapidly growing and evaporating liquid condensate films (e.g., $Na_2SO_4. K_2SO_4$) on solid surface exposed to flowing combustion product gases at film thicknesses well below the onset of complications due to run-off.
To develop this optical system, this study investigated the optical parameters (e.g., polarization state, incident angle, target roughness, etc.).
Trends for the $Na_2SO_4$ (1), $K_2SO_4$ (1) deposition rates as a function of target temperature using this optical measuring system agree with the theoretical prediction of the vapor deposition.
This study was able to extend the experimental range for vapor+condensed phase transport and deposition.
While previously unable to measure interferometrically evaporation rates, these rates are estimated from the results of the investigation of polarization state.
From this study we conclude that
1) Interference method holds the considerable promise for application to rapid remote measurement of condensation and evaporation rates in high temperature flow environments at film thicknesses below the onset of complications due to run-off.
2) When temperature of surface and combustion gas are considerably low, vapor transport mechanisms contain the condensed phase transport. This mechanisms are different from vapor transport alone, and no more controlled by surface temperature.
3) Dew point depends upon flow and transport conditions, so that dew point is by no means a purely "thermodynamic" quantity.
