In this paper, is presented a mathematical deduction of a new improved model for heat transfer calculations during fluid flow in single-phase inside tubes. The proposal model was verified by comparison with available experimental data of 35 different fluids, including water, air, gases and organic substances. The proposal model is valid for a range of Reynolds number for single-phase from 2.4 • 10 3 to 8.2 • 10 6 , Prandtl number for single-phase from 0.65 to 4.71 • 10 4 , dimensionless length in the interval 2 ≤ ⁄ ≤ 450 and values of Petukhov's correction in the interval 0.006 ≤ ⁄ ≤ 177. In 3096 data analyzed, for < 1 • 10 4 , the mean deviation found was 13.91% in the 80.32% of the experimental data, while for 1 • 10 4 ≤ , the mean deviation found was 13.96% in 80.94% of experimental data.