Simulations were performed to examine the effects of a coiled tube after a T-junction on the mixing and flow characteristics. A coiled tube was found to have two effects: inducing a radial flow and flattening the axial velocity distribution, which enhances and weakens the mixing, respectively. In the straight tube section connecting the T-junction and coiled tube, the latter may dominate and cause the mixing to deteriorate. An experiment was performed with the Villermaux/Dushman method to verify the simulation results. Based on a mixing performance simulation with various fluid and geometric structure parameters, a dimensionless correlation was obtained that can be used to determine the mixing intensity along the coiled tube with a deviation of less than 1.5%. These results provide guidance for designing a coiled tube or optimizing the operating conditions to meet the mixing requirements of specific chemical processes. (C) 2018 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.