Heat transfer and pressure drop in helically coiled tube with spherical corrugation are investigated. by a three-dimensional numerical simulation. Different geometrical parameters of spherical corrugation in helically coiled-tube heat exchangers are studied to improve the heat transfer rate. Calculated results have been compared to experimental tests and existing empirical formulas to study the validity of the numerical results. The simulation results indicate that the secondary flow induced by the centrifugal force has significant ability to enhance the heat transfer rate, the eddy caused by the corrugation structure destroys the flow boundary layer and increases the turbulence intensity of the flow and strengthens the heat transfer process. With the increase of the corrugation height (H), the augmentation on heat transfer performance is about 1.05-1.7 times as compared to the smooth helically coiled tube, while friction factor sharply increases 1.01-1.24 times. With the increase of the corrugation pitch (P), the enhancement on heat transfer is in the range of 1.37-1.66 times and the friction factor increases 1.18-1.28 times compared to the smooth helically coiled tube. The overall heat transfer performance of helically coiled tube with corrugation is better than that of smooth helical tube under the same condition. The value of performance evaluation criterion (PEC) could be up to 1.56. (C) 2017 Elsevier Ltd. All rights reserved.