This paper proposes an optimization model for heat exchanger network synthesis that includes a detailed design for each heat exchanger of the network. The model takes into account the optimization of the exchanger units and their geometric and operational constraints from the synthesis stage. The approach is based on the use of genetic algorithms to determine the heat exchanger network that minimizes the total annualized cost, which accounts for the capital costs of heat exchangers and pumps, and the energy costs for utilities and pumping duties. Several case studies are used to show the. application of the proposed method.