In this paper, an efficient design method is presented to implement heat transfer intensification technologies for increasing energy saving in industrial scale heat exchanger networks (HENs). First of all, the detailed models of shell-and-tube heat exchangers are utilized to estimate exchanger performances under normal and intensified conditions, and an optimization method based on simulated annealing is proposed to find appropriate retrofitting options in the existing HENs. Then, a novel retrofit approach based on the exchanger models and optimization method is introduced to retrofit HENs with several possible retrofit strategies, including exchanger relocations, heat transfer intensification, additional area, and stream repiping. Moreover, a new efficient software package (it-HEAT) is developed for the addressed retrofit problems. The interface of int-HEAT is designed to focus on a clear presentation of HEN retrofit procedure, which allows users to easily control all the retrofit stages. An industrial problem of preheat train for crude oil distillation is solved with the use of the new developed software through all the main steps of the proposed retrofit procedure, namely reducing energy consumption, identifying retrofitted exchangers, selecting retrofit strategies, and implementing heat transfer intensification techniques. The case study demonstrates the validity and efficiency of the developed software tool and the proposed approach.