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 new model is presented for design and modelation of piping systems. This work results from recent investigations on pipes friction factor. It provides an empirical solution for the solution of the three basic problems found in the design and evaluation of pipe systems, which in conventional cases require tedious iterative trial and error processes. The proposed solutions are valid in the same interval as the traditional methods used, and in all cases the average error computed never exceeds 2% with respect to traditional iterative methods. The research was done with a regression analysis between kinematic viscosity, relative roughness, flow rate, friction factor, and others factor, using experimental data reported by different authors, establishing comparison with the Swamee-Jain solution for this problems types concluding that between new model and the most universally used there are not signified differences without is lightly better.