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.

This report documents ten developmentalassessmentproblems which were " used to test the multidimensionalcomponent in RELAP5/MOD2.5,Version 3w. The problems chosen were a rigid body rotation problem, a pure radial symmetric flow problem, an r-0 symmetric flow problem, a fall problem, a rest problem, a basic one-dimensionalflow test problem, a gravity wave problem, a tank draining problem, a flow through the center problem, and coverage analysis using PIXIE. The multidimensionalcode calculationsare compared to analytical solutions and one-dimensionalcode calculations. The discussion section of each problem contains informationrelative to the code's ability to simulate these problems. iii Idaho, Inc., managers during the development and assessment of this capabilitywho provided coordination,direction,and resources.

process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to an)' specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

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