A computational tool to design and generate crystal structures R C Ferreira, M B Vieira, S O Dantas et al. Abstract. Small improvement in thermal efficiency of power cycles brings huge cost savings in the production of electricity, for that reason have a tool for simulation of power cycles allows modeling the optimal changes for a best performance. There is also a big boom in research Organic Rankine Cycle (ORC), which aims to get electricity at low power through cogeneration, in which the working fluid is usually a refrigerant. A tool to design the elements of an ORC cycle and the selection of the working fluid would be helpful, because sources of heat from cogeneration are very different and in each case would be a custom design. In this work the development of a multiplatform software for the simulation of power cycles and refrigeration, which was implemented in the C ++ language and includes a graphical interface which was developed using multiplatform environment Qt and runs on operating systems Windows and Linux. The tool allows the design of custom power cycles, selection the type of fluid (thermodynamic properties are calculated through CoolProp library), calculate the plant efficiency, identify the fractions of flow in each branch and finally generates a report very educational in pdf format via the LaTeX tool. IntroductionThis work aims to simulate refrigeration cycles and power cycles, specifically cycles Rankine. A computational tool was developed in the programming language C++ using the Qt crossplatform environment. It is also possible to simulate Organic Rankine Cycles (ORC) using a secondary fluid as the working fluid, Tchanche [1] made a detailed analysis of the different types of architectures for these cycles study. Programming in an object-oriented language has many advantages over a structured programming language, such as the work of Jeon [2] The first part consisted of the design of the models, starting with the modeling of the working fluid for which it was decided to use libraries CoolProp[8], modeling of the devices was based on existing in the literature concerning thermodynamic devices operating at steady flow models and then the cycle model was modeled with graph theory. Then it proceeds to solve algebraic