Based on variable cross-section structure, a novel triangular perforated fin was proposed in this paper. 3-D models were established to study convective heat transfer and fluid flow characteristics of the triangular perforated fin for numerical simulation using CFD software. Compared to the related experimental data, the validation of CFD method was verified. The effects of hole opening ratios and hole stagger arrangements on heat transfer and pressure drop characteristics were investigated. Variation in the Colburn factor j and the friction factor f relative to Re were examined. The performance criteria j/f(1/3) were calculated and superior to the serrated fin under the Reynolds number ranges from 200 to 1960. The inherent mechanism of fluid flow and heat transfer enhancement was explained by the field synergy principle. The average field-synergy angle of B-1/2 was the largest and A-1/4 had the smallest one. The values for A-1/2 were in between. The field synergy principle analysis was consistent with the numerical results. It stated that the secondary flows and vortices can improve the synergy between the velocity and temperature gradient, which is the most fundamental reason why the triangle perforated fin can enhance the heat transfer. (C) 2013 Elsevier Ltd. All rights reserved.