Elementary thermodynamic cycle processes consist of two pairs of identical state changes aimed at obtaining work. They recur and come back to normal. All real processes are irreversible, but for the purpose of comparing work losses, the Carnot process is taken, which has the highest reversibility of all processes. The paper describes the elementary cycle processes: Carnot, Joule, Otto and Lorenz as well as the steam plant cycle processes: Carnot, Clausius-Rankine with saturated steam and Clausius-Rankine with dry saturated steam. For them, work losses due to the irreversibility of the process were calculated. The results of the calculation of work losses were analyzed in order to determine the best process, the process with the lowest work losses in relation to the Carnot cycle process. Based on the analysis of elementary cycle processes, it was determined that the Lorenz process with the polytrope exponent 1,2 has the largest work losses due to the irreversibility of the process. Likewise the Lorenz cycle process has the lowest thermal efficiency and the work obtained. Based on the analysis of the steam plant cycle processes, it was determined that the Clausius-Rankine saturated steam process has the lowest thermal efficiency.