A 3-D numerical study is carried out to investigate the laminar flow and heat transfer performance of the rectangular mini-channel where the discrete double-inclined ribs are worked as the longitudinal vortex generators. The effects of the Reynolds number, the height of the ribs and the number of double-inclined ribs along the mainstream on the heat transfer and flow performance of the mini-channel are examined and analyzed from the field synergy perspective and the entropy generation. The results show that the heat transfer performance is enhanced effectively by the double-inclined ribs which cause the generation of the longitudinal vortexes in the mini-channel. The heat transfer performance increase with the increasing height or number of the double-inclined ribs, but the flow resistance will increase at the same time. In order to obtain the best overall performance of the mini-channel, the height of the ribs should be reduced with the increase of the Reynolds, and the overall performance would be improved with the increase of the ribs number in the mini-channel. The heat transfer performance has a direct relation to the field synergy characteristic of the mini-channel. The entropy generation rate dues to heat transfer irreversibility and fluid frictional irreversibility can be used for the evaluation of the heat transfer and the flow performance of the mini-channel well respectively, while the total entropy generation rate cannot be used as a criterion for the overall performance. (C) 2014 Elsevier Ltd. All rights reserved.