Numerical Study On Flow And Heat Transfer Characteristics For Rectangular Finned Elliptical Tube

With the development of modern industry and population growth, the phenomenon of the energy shortage is becoming more and more serious, especially reflected on the water resources. As a major water user, the thermal power generation enterprises take unavoidable responsibility for water-saving. With the development of direct air-cooling technology becoming mature and metal materials processing and manufacturing ability improvement, direct air cooling technology for its energy-saving, environmental capabilities and thermal performance has been promoted and development in the north of the "rich coal shortage" area. Finned tube is used as the core of the radiating element of air-cooling condenser, the flow and heat transfer characteristic of which is not only related to the economic benefits of hydropower station, but also play a great influence on safe running of air-cooling system.By using FLUENT software, this thesis makes numerical simulation of heat transfer and flow characteristics of Rectangular Finned Elliptical Tube air side in direct air-cooled condenser. By analyzing the fin parameters (fin length, fin width, fin thickness, fin pitch, fin aspect ratio), elliptic base tube arrangement, size, ambient temperature and by analyzing heat transfer, fin efficiency, comprehensive performance parameters (j/f) under different condition, we can seek a way of enhanced heat transfer and flow resistance. The simulation results show that:the effect of fin length on average Nu of rectangular finned elliptical tube is not very obvious, with the increase of fin length, the drag coefficient and the fin efficiency decrease, the heat transfer and the performance parameters of j/f increase. The fin width has little effect on Nu of the air outside the tube side, with the increase of fin width, the drag coefficient and the fin efficiency decrease and the heat transfer and j/f increase. In the low inlet velocity, the effect of fin thickness on Nu is not very obvious, Nu increase with the increase of inlet velocity and fin thickness, the drag coefficient, fin efficiency and heat transfer increase, j/f decrease. The effect of fin pitch on the heat dissipation capability, flow resistance, fin efficiency and heat transfer is significant. The effect of fin aspect ratio on the drag coefficient is not very obvious, with the increase of fin aspect ratio, Nu and the heat transfer decrease, the fin efficiency first increase and then decrease. Ambient temperature has little effect on Nu, drag coefficient and fin efficiency, with the increase of ambient temperature, the heat transfer decrease and the performance parameters of j/f increase. The drag coefficient, fin efficiency and Nu decrease with the increase of the ratio between the long axis and short axis of the elliptic tube, but the heat transfer and j/f increase. The drag coefficient, fin efficiency and Nu decrease with the elliptic tube forward along the main direction of the offset distance increase and the heat transfer increase.We make three-dimensional numerical simulation research of flow and heat transfer characteristics in the different arrangement of double rectangular finned elliptical tube bundles, and make research and analysis of the surface temperature of front row fins and back row fins, sectional pressure between fin channels, velocity distribution by using visualization technique, then by making a comparative research between transfer capacity, flow resistance and heat dissipation in two kinds of fin, we can provide theoretical and data basis for practical engineering application.