As heat exchangers are used extensively in many engineering fields the increase of their heat transfer rate, while reducing their flow resistance has become one the most challenging aspects in heat transfer. In this study, heat transfer and flow resistance of alternating elliptical axis tubes is investigated both experimentally and numerically. The working fluid is heat transfer oil, and the flow's Reynolds number ranges from 300 to 2000. The grid and numerical models are generated using Gambit 2.4.6 and Fluent 6.3, which are verified by the experimental results. The numerical results show that decreasing the aspect ratio and pitch length, increases heat transfer and flow resistance. However, in order to compare the heat transfer and flow resistance simultaneously, the non-dimensional heat transfer enhancement ratio is defined. The comparison of this ratio shows that alternating elliptical axis tubes perform better than the flattened or circular ones. It is observed that this ratio increases with the increase in Reynolds number. (C) 2014 Elsevier Ltd. All rights reserved.