This Diploma thesis describes design of the computational model of Uehara power cycle, with ammonia-water mixture used as working fluid. First part is dedicated to issue of determination working mixture thermodynamic properties, which are essential for computational model design. The second part of this thesis describes the methodology of computing power cycle by system matrix solving method. For purposes of methodology testing, model of Kalina power cycle was also created. Computational models of Uehara and Kalina cycles are designed in Excel and are an integral part of this thesis. Text part also includes a description of their user interface, calculation algorithm and detailed description of the design methodology.