The following thesis addresses the evaluation of heat exchanger networks. It is divided into two sections, the presentation of methods to evaluate heat exchanger networks and the implementation of this evaluation in a process simulation software. The main focus is on the concept of this evaluation. Therefore, three methods to evaluate heat exchanger networks using nonlinear optimization are presented. The evaluation of the heat exchanger networks is made due to the annual costs for building and operation of the heat exchanger network as well as costs for potentially dissenting target temperatures. Furthermore, the influence of different heat exchanger types on the heat exchanger network's behaviour is discussed, and it is pointed out how the developed methods can be implemented in a process simulation software.