In this paper, a simple algorithm is developed for the design and economic optimization of multiple-pass 1-2 shell-and-tube heat exchangers in series. The design model is formulated using the FT design method and inequality constraints that ensure feasible and practical heat exchangers. Simple expressions are obtained for the minimum real (non-integer) number of 1-2 shells in series. A graphical method is also presented to develop some insight into the nature of the optimization problem. The proposed algorithm enables engineers to design optimum multipass heat exchangers quickly and easily. It is also shown how the method can be applied for optimal design of multipass process utility exchangers. (c) 2007 Published by Elsevier B.V.