Transientfilm condensation ona vertical surface in a thin porous medium with large anisotropic permeability

The present study deals with the problem of transient film condensation on a vertical surface embedded in a thin porous medium with anisotropic permeability filled with pure saturated vapour. The principal axes of anisotropic permeability are oriented in a direction that non-coincident with the gravity force. On the basis of the flow permeability tensor due to the anisotropic properties and the Darcy-Brinkman’sflow model adopted by considering negligible macroscopic and microscopic inertialterms and boundary-layer approximations in the porousliquid film momentumequation, the energyequationissolvedanalyticallyusing the method of characteristics. The previous analysies have been extended to take into account the influence of the time variable which is involved only in the energy equation.Thus, the analytical solution of the governing equations of the problem is obtained and shown that the expressions of the dimensionless thickness of the liquid film and the Nusselt number didn’t depend on anisotropic parameters in the transient regime, but the increasing of the anisotropic parameters improved the characteristic limit time of the transition from transient to steady state.