Browsing by Autor "Oscar Cruz Fonticiella"

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Abstract of heat transfer coefficient modelation in single-phase systems inside pipes
(International Information and Engineering Association, 2017) Yanán Camaraza-Medina; Nislan Khandy; Oscar Cruz Fonticiella; Osvaldo Fidel García Morales
It is a widespread practice and recommended in a large part of the literature on the subject to perform the calculation of the average heat transfer coefficients in single phase media using the expressions of Or the improved version of Sieder -Tate This procedure is a necessity for many project calculations or evaluation of industrial facilities. However, these expressions have a high dispersion value of the obtained results to the real values of the systems analyzed, being in the literature consulted errors of the order of % 25 . In the 1960s, [1], at the Moscow Institute of Energy, an equation was obtained, which was derived basically from experimental point adjustments, which were later implemented at the Analogy of Prandtl. The equation obtained is known in the specialized literature as Petukhov equation, in recognition of the leader of the research group that developed this important research for the science of the term convective transference. This equation reduces the absolute mean error as a function of the number of Prandtl, so that: % 10 200 Pr %
Optimización de Intercambiadores de Calor de tubo y coraza teniendo en cuenta las restricciones mecánicas
(2015) Maida Bárbara Reyes Rodríguez; Jorge Laureano Moya Rodríguez; Oscar Cruz Fonticiella; Eduardo Migeu Fírvida Donéstevez
Normally when the optimization of a heat exchanger is realized looks for to diminish the cost, being used for the thermal and hydraulic calculation some of the methods established in Literature, preferably the method of Kern or the one of Bell Delaware. After realized the optimization, the interchanger according to the procedure is designed mechanically established by the different norms, mainly norms ASME and TEMA. Nevertheless the mechanical calculation, as much of the resistance of the tube and shell, like the calculation to the vibrations, can produce the modification of the values of the used variables of design in the process of thermal and hydraulic optimization. In the present work a procedure for the mechanical optimization of the heat exchangers of tube and shell, that not only consider the objectives functions own of the thermal and hydraulic design of the interchangers, but also restrictions is offered, in such a way that the resistance of the optimized interchanger is guaranteed. All the procedure was implemented using MATLAB.
Simplified model for the calculation of degrees-day with variable time scale
(2021) Ovidio Rodríguez Santos; Oscar Cruz Fonticiella; Alfredo Leyva Céspedes
In this paper, the authors propose a simplified model for the calculation of degree days for different time scales and variable base temperature. It is summarized in six expressions that result in a simple, compact and easy to program model in any spreadsheet. Its main advantage lies in the integrated calculation of degree days for daily, monthly and annual time scales, which makes it attractive for its application in strategic sectors of the economy such as the electro-energy, construction and agriculture sectors. It is applicable to regions for which the values of the regression coefficients necessary for the determination of the equivalent temperature (parameter defined by the authors, valid for a given geographical region) have been previously fixed. These coefficients have been determined for the areas surrounding the Yabú meteorological station, belonging to the province of Villa Clara, for the territory covered by this province and for the whole territory of the Cuban archipelago. Two versions of the model are presented, a base version and an extended one; the first one uses as input variables the mean temperature, the mean minimum temperature and the mean maximum temperature, according to the time scale to be considered, the second one allows its application by introducing the mean temperature as the only input variable. The difference in accuracy between these versions is not significant, so both are recommended