One reason it is challenging to predict oil recovery rates from solvent-based heavy oil recovery methods is that the interplay of the mass transfer and convective flow mechanisms is not well understood. An apparatus was designed and commissioned to investigate these mechanisms in a controllable flow geometry. The apparatus consisted of a Hele-Shaw cell (parallel glass plates) that was partially filled with bitumen and rotated to set a target initial slope of the bitumen layer. Toluene was fed at the top of the bitumen at a constant volumetric flow rate. The flow rate, composition, and properties of the drained liquid were measured over time, and photographs of the bitumen profile were taken periodically. The measurements were performed at ambient conditions at injection flow rates from 0.1 to 2 cm(3)/min, gap widths of 0.5 and 1 mm, and initial angles of inclination between 30 and 45 degrees. The data were modeled with a two-dimensional numerical model in which the fluid was divided into columns, each with a solvent (drainage) layer and a bitumen layer. The following recovery mechanisms were identified: (1) diffusion of bitumen into the drainage layer represented with Fick's Law, (2) open duct flow of the drainage layer represented as a falling film, and (3) flow of the bitumen phase settling under its own weight. The model with a single fixed tuning parameter matched all of the bitumen production rates with an average deviation of 7.4%.