A novel combined single shell-pass shell-and-tube heat exchanger with two-layer continuous helical baffles (CSSP-STHX) has been proposed in the present study as an alternative solution of overcoming the drawbacks of the shell-and-tube heat exchanger with continuous helical baffles (CH-STHX). The shell-side baffles of CSSP-STHX are consisting of inner layer and outer layer continuous helical baffles, which are not on the same helical surface. There is no sleeve tube between inner and outer layers, thus complex flow field can be formed in the shell side which means inner layer fluid can rush out to the outer layer under the centrifugal force. Numerical simulations are carried out to compare thermo hydraulic performances of the three heat exchangers which are shell-and-tube heat exchanger with segmental baffles (SG-STHX), CH-STHX and CSSP-STHX. The results show that the CSSP-STHX has a higher heat transfer performance while maintaining a lower pressure drop. The CSSP-STHX might be an ideal choice to replace the SG-STHX and CH-STHX in industrial applications. (C) 2014 Elsevier Ltd. All rights reserved.