Flow Field Synergy Principle Based Optimization Performance Of Natural Draft Dry Cooling System

With the increasing scarcity of water resources worldwide,improving the utilisation of water has become the dominant factor of the times.In the water-poor and coal-rich northern regions of China,indirect air cooling is gradually becoming the best choice for the cold end of power stations in water-scarce areas.The working principle of natural ventilation indirect cooling towers is to use the pressure difference between the air before and after the heat exchanger with different densities to drive the cold air flow through the finned tubes and take away the heat from the cooling water.In the ambient wind,the cooling tower is broken due to the pressure field around the broken ring driving the uniformity of the flow field in the tower eventually causing a significant decrease in heat exchange,the plant back pressure of the unit with the coal consumption subsequently increases,the unit economy decreases.In order to reduce the adverse effects of the ambient wind field on the performance of the cooling tower,relevant experts have proposed a variety of optimisation schemes,but the lack of theoretical support,Engineering is generally done using field and data experience to obtain the final solution through repeated tests.Based on this problem,this paper uses the field synergy principle of flow process optimisation as the theoretical basis,and uses mathematical methods to calculate the variational N-S equation and get the drag reduction equation under minimum momentum product dissipation,and adds the corresponding source term expressions to the N-S momentum source term to obtain the optimised flow equation.A three-dimensional model of the indirect air-cooled tower is established using the CFD pre-processing software Gambit,and the thermal numerical simulation is carried out by FLUENT to analyse the performance characteristics of the indirect air-cooling under the wind field,and the simplified model is used to carry out numerical simulation of the optimised minimum resistance field.The velocity distribution of the resistance flow field provides guidance for the installation of the deflector plate,and the addition of the deflector plate reduces the pressure difference between the inlet and outlet of the cooling tower by 12.72%-76.91%at different wind fields.Under the guidance of the optimal flow field,a three-dimensional model of an air-cooled tower with suitable sized and shaped baffles at the corresponding positions in the tower is planned and imported into FLUENT for thermal calculations.The calculation results show that the total drag coefficient of the air-cooled tower with internal deflectors is significantly reduced,the distribution of the flow field in the field tends to become more uniform,the air mass flow rate of some side fan sections is increased and the total heat dissipation of the new air-cooled tower is increased by The total heat dissipation of the new air-cooled tower is increased by 1.14%-11%compared to that of the empty tower.The optimization method guided by the theory of flow field synergy can scientifically install the air deflector in the tower,improve the heat transfer flow characteristics of the indirect natural ventilation air-cooling system under complex ambient wind,improve the economy of the power station,and provide theoretical support for the optimization method of the indirect dry cooling unit under ambient wind.