A MODELING OF THE LIQUID-VAPOR FLOW IN A SELF-HEATED POROUS MEDIUM - WITH APPLICATION TO THE DRYOUT LIMITS

摘要

Time dependent flow and heat removal behavior up to incipient dryout in a porous medium are investigated numerically. The porous medium composed of coarse particles with volumetric heating is cooled by a countercurrent flow in a two-phase region with evaporation. A separated flow model, based on the two-phase extended Ergun equations with Ergun constants depending on Reynolds number and on the mass conservation, is developed for a local thermodynamic equilibrium between each phase. Owing to the nonlinearity of the coefficients appearing in the governing equations: numerical computations are iteratively made. Numerical predictions are also compared with available data of dryout heat flux in the literature. For the cases of shallow porous media the predicted dryout heat generation rates lie in the experimental ranges. However, the cases of deeper porous media were overpredicted by this calculation. In addition, the transient heat removal process up to dryout is discussed qualitatively by means of the axial liquid volumetric fraction, phase pressure, liquid velocity and vapor velocity distributions. [References: 22]