FLOW STRUCTURE DEFINITION IN THE BUNDLES OF FLAT-OVAL TUBES WITH INCOMPLETE FINNING UNDER CONDITIONS OF NATURAL DRAFT

The expediency of using "dry" cooling systems for technological products is considered. The expediency of using flat-oval tubes with incomplete finning as heat exchange surfaces of air coolers is shown. The transfer of the operating mode of air coolers to the operating mode with the fans turned off during a certain time of the year is substantiated. Installation of an additional exhaust tower can lead to energy savings for the fan drive up to 55 %. The technique of numerical modeling and experimental study of the flow structure in a package of flat-oval tubes with incomplete finning under natural draft conditions is presented. Experimental studies and computational fluid dynamics (CFD) – modeling of the flow structure and averaged velocity fields in a package of flat-oval tubes with incomplete finning under natural draft conditions are carried out. The obtained numerical and experimental distributions of velocities and temperatures near the surface of the tubes and in the wake behind them give an idea of the features of the flow around the tubes and the effect of the flow structure on the intensity of their heat transfer. It was found that the hydrodynamic flow pattern in a stack of flat-oval tubes according to the results of CFD modeling corresponds to the classical concepts of hydrodynamics. The absence of a part of the finning in the aft part of flat-oval tubes with incomplete finning, where the formation of the aft circulation zone is observed, is substantiated. The verification of the CFD-modeling data and the data of the experimental study on the determination of the average velocities and temperatures in the flow behind the pack of flat-oval tubes with incomplete finning is carried out. The verification results indicate that the average numerical simulation error does not exceed 18 %. It is shown that to determine the optimal, from the point of view of heat transfer, geometric parameters of a number of flat-oval tubes under natural draft conditions, it is advisable to use CFD modelin