This paper describes a simultaneous MINLP optimization model for the retrofit of heat exchanger networks (HEN), comprising different exchanger types. This model is based on the stage-wise superstrucutre of HEN [Comput. Chem. Eng. 14 (1990) 1165], extended for retrofit and different exchanger types. Each potential match in the superstructure is now replaced by a match superstructure comprising: double pipe (DP), shell and tube (U tubes, ST), and plate and frame exchangers (PF). The operability constraints for the different exchanger types are modeled by the convex hull formulation of disfunctions, nonlinear terms are modeled only within the objective function and additional constraints are included to obtain feasible temperature distribution. Several examples are presented to illustrate the efficiency and advantages of the proposed multi-type model. (C) 2003 Elsevier Ltd. All rights reserved.