An interacting triangular tube bundle model is developed using capillaries of equilateral triangle cross sections. In addition to pressure equilibration among the capillaries, the non-circular tubes allow the wetting phase to reside in the corners and flow continuously in the entire model. An interacting-serial type model is constructed with step changes of tube size along the model, while the total cross-section of the model is kept constant. This model includes trapping of oil which is absent in traditional tube bundle models. Trapping of non-wetting phase in the model in imbibition processes is simulated. The relationship between the residual oil saturation and the complete capillary number CA is investigated. The simulation results obtained by this model are consistent with the results reported in literature of both experimental studies, using actual porous media, and simulations in pore-scale network models. The effects of the tube size, tube size distribution and viscosity ratio on the magnitude of entrapment are also studied using this tube bundle model. (C) 2010 Elsevier Ltd. All rights reserved.