Modeling of Direct Contact Condensation in the Water-Saturated Zone of the Soil Exposed to Steam Injection

In this research, the phenomenon of direct-contact condensation in porous media has been investigated based on the computational fluid dynamic technique, CFD, for hydraulic and thermal phenomena assessment. This phenomenon occurs in soil remediation by steam injection. The main contribution of this research is developing a new combined model for considering steam condensation in the saturated porous media systems using the direct contact condensation model, DCC, and Navier-Stockes equations rather than solely using Darcy's law-based model. For the first time, a two-resistance DCC model for porous media application has been included, predicting the propagation of steam front and condensation. The corresponding source and sink terms are due to the calculated condensation rate is added to each phase continuity equation and enthalpy equation of the liquid phase by user-defined functions, UDFs. Pressure drop due to flowing fluids in the porous structure was considered by lumped approach model using viscous and inertial loss terms added to momentum equations of the model. Heat loss from the sandbox is considered a sink term based on the calculated overall heat transfer coefficient and local temperature differences. The model results meet acceptable predictions for steam saturation content and temperature distributions over time and the predictions are qualitatively similar to the experimental and simulation results of the previous literature. The quantitative values of the sandbox-covered thermal areas were extracted from propagated saturated temperature fronts over processing time for both DCC simulation results and available experimental measurements, then the values were compared together. After elapsing 12 and 18 minutes from the beginning of the process, the simulation values of covered thermal areas are 0.049 m(2) and 0.082 m(2). The corresponding experimental values are 0.059 m(2) and 0.098 m(2), respectively. Evaluated absolute values of the relative change percent of covered thermal areas are 16.3% and 16.9% over processing times of 12 and 18 minutes.

Automated summary

This research investigates the phenomenon of direct-contact condensation in porous media using computational fluid dynamics. A new combined model is developed to consider steam condensation in saturated porous media systems, using the direct contact condensation model and Navier-Stokes equations. The model results are in good agreement with experimental and simulation results, predicting steam saturation content and temperature distributions over time.