Numerical Simulation Of Irregular Pipe Used In Direct Air-cooling System

The problem of"Rich coal ,but lack of water"in North China was solved effectively after the technology of air-cooling was introduced . The core components of air condenser play an important role in the whole air-cooling system, therefore , the study on their flow and heat transfer characteristics appears very important . Such work has been done for the core components of air condenser as follows .Numercial caculations have been performed to annalyze the characteristics of air flow and heat transfer inside the fin channels of air cooler condenser used in power plants. The influencing parameters, including environmental temperature, air head velocity, the shape of the tube, fin pitch, fin thickness and fin height, which would affect the air-side flow and heat transfer performance, were optimized with system analysis. Numerical simulation results showed that environmental temperature could neither affect the local heat transfer coefficients nor the pressure drop. Both heat transfer coefficient and pressure drop increased with the increase of air head wind velocity. The shape of the tube had little effect on the heat transfer coefficient, but had a significant effect on the pressure drop inside the fined channels. The fin pitch had little effect on the heat transfer coefficient, but had a significant effect on the pressure drop and the total amount of heat transfer inside the fined channels. The heat transfer coefficient and the pressure drop increased with the increase of the fin thickness. In addition, the heat transfer coefficient and the pressure drop decreased with the increase of the fin height.The local heat transfer coefficients distributions on the surface of fins with and without interrupted holes were discussed. At the same time, the influencing parameters including the dimension of the interrupted holes, the number of interrupted holes and the position of the interrupted holes, were optimized with system analysis. Numerical simulation results showed that the heat transfer coefficient and the pressure drop increased with the increase of the dimension of the interrupted holes, however, the total heat exchange decreased. The heat transfer coefficient and the pressure drop increased with the increase of the number of the interrupted holes within a certain range, and the total heat exchange increased, too. Relatively, the position of the interrupted holes could impact the heat transfer coefficient and the pressure drop less than the the number and the dimension of the interrupted holes.Numerical analysis on the flow and heat transfer performances of two-row bundles with different fin pitch was carried out. The effects of fin pitch on air-side heat transfer coefficient and pressure drop were discussed , and formula that could describe the relation of heat transfer coefficient and pressure drop with the head wind velocity was fitted for engineering application .Numercial caculations were performed to annalyze the characteristics of air flow and heat transfer inside the rectangular-fin droplet-shaped tube and serpentine tube, and the results were compared with the results of the the rectangular-fin elliptic-tube, It turned out that the rectangular-fin elliptic-tube was better in view of the heat transfer coefficient and the pressure drop.