This paper presents the results of the continuity of the research process carried out in the center of environmental and energy studies that belonged to the Technical Sciences Faculty of the University of Matanzas related to obtaining nondimensional models for the determination of the average coefficient of heat transfer in turbulent flows inside smooth and straight tubes. The research consists of a regression analysis performed between the Reynolds number, the Prandtl number and the friction factor, using for this purpose experimental data reported by different authors, establishing a comparison with the equations of Petukhov and Gnielinsky, exact and referenced in the known literature, obtaining that there are no significant differences, due to the high similarity between the results obtained from these models in the studied range of the work parameters, although the divergence between the experimental values and those obtained by the proposed model is slightly smaller.

This paper presents the results of the continuity of the research process carried out at the Center for Energy Studies, belonging to the Faculty of Technical Sciences of the University of Matanzas, related to the production of dimensionless models for the determination of the mean coefficient of heat transfer by condensation in Air Cooled Condenser systems (ACC), inside straight and inclined tubes. The research consists in analytically obtaining the solution of the differential equation of the velocity profile, considering that the condensation is of the film type, finally the Roshenow empirical condition is combined with the theoretical solution, to generate a numerical expression that allows obtaining with A 15, 2 % deviation in 692 tests, a mean value of the heat transfer coefficient by condensation very similar to that obtained with the use of the most referenced model in the literature known and consulted, Chato's empirical model.

In this paper, a modification to the dominant flow criteria is presented for the study of heat transfer by confined condensation in Air Cooled Condenser (ACC) systems. The new methodology combines in one single procedure the analysis, which with the current methods requires tedious grouping processes. A new proposal reduces the average error by computing 22% in 88.7% of the available samples and includes the shear stress produced by the steam drag when it flows at speeds greater than 40 m/s. New method is also valid for a vapor quality located between 0.9 and steam flows between 3 and 590 kg/(m2/s-1), values for the Reynolds number for the liquid portion between 660 and 58 540 and the Reynolds number for the vapor portion located between 1 320 and 333 120, internal equivalent diameters of the tubes comprised between 7.4 to 49 mm.