Voznyuk M. Heat transfer of flat-oval tubes with incomplete finning under conditions of natural convection and natural draft

The dissertation is devoted to solving the urgent problem of developing scientific foundations for creating efficient heat exchange devices based on flat oval tubes with incomplete finning, operating under conditions of natural convection and natural draft. In this work, complex experimental and CFD studies of heat transfer, aerodynamic drag, characteristics and flow structure during the operation of flat oval tubes with incomplete finning under conditions of natural convection and natural thrust have been carried out. Generalized dependences for calculating the intensity of convective heat transfer of single flat-oval tubes with incomplete finning under free convection conditions and for calculating the intensity of convective heat exchange and aerodynamic drag of staggered bundles of flat-oval tubes with incomplete finning at small Reynolds numbers are obtained. Experimental and numerical results of the distributions of the velocity and temperature fields near the surface of flat oval tubes with incomplete finning and in the wake behind them are presented, which made it possible to expand the understanding of the features of the flow around the tubes and the effect of the flow structure on the intensity of their heat transfer under natural draft conditions. The performed variant calculations of the air cooler, in which the air consumption is provided only by the exhaust tower, showed that the variant of the heat exchanger based on flat oval tubes with incomplete finning has the least amount of necessary capital costs for its manufacture.A method of thermal and aerodynamic design calculation of a heat exchanger based on flat oval tubes with incomplete finning, operating under natural draft conditions, is proposed.