BOILING IN A POROUS LAYER HEATED FROM BELOW - EFFECTS OF NATURAL-CONVECTION AND A MOVING LIQUID 2-PHASE INTERFACE

Boiling and natural-convection processes in a horizontal, fluid-satura ted porous layer are investigated. The layer is heated uniformly from below and is cooled from above. Volumetric cooling is also allowed. Th e thermodynamic structure consists of a liquid region overlying a two- phase region. Numerical techniques are used to solve the transient, tw o-dimensional equations in the liquid and two-phase regions, and at th e phase-change interface. A parametric study is carried out in terms o f the liquid-phase Rayleigh number (Ra) and the non-dimensional bottom heat flux (Q(b)). Three solution regimes are observed: conduction-dom inated at low Ra, convection-dominated at intermediate Ra, and oscilla tory convection at high Ra. In the convection-dominated regime, transi tions to multiple cell patterns are observed as Q(b) is increased. Osc illatory convection appears to be triggered by asymmetric disturbances in the system. The effects of initial conditions and the stability of the solutions to perturbations are also investigated. The heat transf er correlations and qualitative flow patterns are in agreement with ex periments.