Natural convection of a layered fluid system composed of two immiscible liquids, silicone oil on top of water, is studied numerically. The Bow in the two layers is viscously and thermally coupled. Two counter-rotating natural convection roll cells of opposite vorticity develop when one side wall temperature in the density inversion fluid is above and the other below the density inversion temperature. In contrast, only one roll cell develops in a liquid layer with Boussinesq properties. The viscous coupling between both immiscible layers strengthens the roll cell with opposite vorticity in the density inversion layer. At large Rayleigh number the Row pattern in the density inversion layer becomes very complex. The largest heat transport occurs in the upper Boussinesq layer. The two-roll cell pattern in the density inversion layer is impeding the total horizontal heat transfer. A vertical heat transport exists across the interface from the density inversion layer into the encapsulating upper layer. The moving interface between the immiscible liquids improves the heat transfer in each layer when compared to the cavity cases.