The air flow field of air cooling unit in direct air cooling systems has dramatic spiral trend and is centrosymmetric distributed

resulting in a very uneven distribution of cooling air volume in finned tube bundles

a really low utilization efficiency of the heating surface of finned tubes and quite poor flow and heat transfer performance of air cooled condenser. Thus

the CFD software was applied to investigate the dynamic characteristics of air flow field inside the direct air cooling unit. It finds that due to sudden change of flow area at the fan outlet

flow dead zone and vortexes form at the air cooling unit bottom and serious reflux occurs in the unit center

causing an increase in flow resistance

which impedes the cooling air to flow from the fan outlet toward the finned tube bundles. Therefore

four flow guidance schemes were put forward and thermal performance of the air cooling unit in these four schemes were analyzed. The results show that

after guidance of the cooling air inside the air cooling unit

the air flow field is optimized

the bundles' surface flow and temperature field are more uniform and the flow and heat transfer property of the air cooling unit are significantly improved.