The novel natural draft direct air cooling system combines the advantages of conventional direct air cooling and indirect air cooling

and has become one of the important choices for the cold end system of power stations. However

at present

the research on flow and heat transfer performance of the novel direct dry cooling system by domestic and foreign scholars is insufficient

especially the study on flow characteristics of the steam distribution pipe. Numerical simulation method was applied to establish the mathematical and physical model of a 660 MW natural draft direct air cooling system

including the air-side model of the novel direct air cooling system and the steam-side model of the tree-shape steam distribution pipes. The coupling calculation procedure of the airside and steam-side simulations of the novel direct dry cooling system was developed

and the interaction laws between the cooling performance of the double-layer cooling deltas and the flow resistance characteristics of the steam distribution pipes under different ambient conditions were studied

and the variation law of the air-side flow heat transfer

the steam flow distribution and the steam distribution pipe resistance characteristics of the natural draft direct air cooling system was obtained. The results show that

the flow heat transfer performance of the finned bundles at different sides of the cooling delta is not the same under windy conditions

which leads to the deviation of the steam flow distribution curve and the resistance characteristic curve to the crosswind sector. Under windless conditions

the distribution of steam-side pressure drop through the tree-type steam distribution pipe is uniform

which reflects reasonable structural design of the steam distribution pipe. The research results can provide reference for design and operation of natural draft direct air cooling systems.