A combined multiple shell-pass shell-and-tube heat exchanger (CMSP-STHX) with continuous helical baffles in outer shell pass has been invented to improve the heat transfer performance and simplify the manufacture process. The CMSP-STHX is compared with the conventional shell-and-tube heat exchanger with segmental baffles (SG-STHX) by means of computational fluid dynamics (CFD) method. The numerical results show that, under the same mass flow rate M and overall heat transfer rate Q(m), the average overall pressure drop Delta(pm). of the CMSP-STHX is lower than that of conventional SG-STHX by 13% on average. Under the same overall pressure drop Delta(pm). in the shell side, the overall heat transfer rate Q of the CMSP-STHX is nearly 5.6% higher than that of SG-STHX and the mass flow rate in the CMSP-STHX is about 6.6% higher than that in the SG-STHX. The CMSP-STHX might be used to replace the 5G-STHX in industrial applications to save energy, reduce cost and prolong the service life. (C) 2008 Elsevier Ltd. All rights reserved.