Background: Nitrate natural convection loop (NNCL) was designed to study the heat transfer behavior and corrosion behavior of direct reactor auxiliary cooling system (DRACS). DRACS is residual heat removal system of Advanced High-Temperature Reactor (AHTR) whilst the air cooling tower is the ultimate heat sink of DRACS. The structure of salt-to-air heat exchanger and the design of cooling tower are important in determining performance. Purpose: The aim is to study the performance on air cooling tower of nitrate natural convection loop

and finalize the optimization design. Methods: Based on the FLUENT software and structure model of the cooling tower

numerical simulations are carried out to study the heat transfer performance of NNCL. Results: The results show that the by-pass flow will reduce the heat transfer ability. The capacity of heat transfer can be enhanced by installing of the by-pass damper

and 3-layer by-pass damper can increase the capacity of heat transfer by as much as 100%. Conclusion: Numerical simulation can provide some basis for optimizing heat transfer performance of the air cooling tower

and increase the by-pass damper design is necessary to effectively avoid the by-pass flow of air heat exchanger.Cited