Nowadays environmental and technological goals for aero engines, as well as gas turbines for power generation demand a high thermal efficiency of the gas turbines. Therefore, a method to analyze losses in gas turbines to understand the optimization potential is crucial. A common approach to consider losses in technical applications is to use the first law of thermodynamics. The focus of this thesis is to use the second law of thermodynamics to analyze losses in turbomachines. In the first part, an analysis of thermodynamic cycles is performed. In many studies thermodynamic cycles are analyzed and judged mostly solely by thermal efficiency and specific power output. Another way to describe the efficiency of a cycle and to identify its potential is the analysis of the entropy production of the system. In the second part, a more detailed analysis of internal entropy production mechanisms is performed. For this reason, the generation of losses in a turbulent flow around a turbine vane is investigated for different Mach number regimes, different thermal boundary conditions at the vane, as well as a configuration with film cooling. Local entropy production rates can be calculated in the complete flow field by using the entropy transport equation. This method identifies the exact locations of entropy production in the flow field and the sources of losses.weiterlesen