CRITERION METHOD FOR MODELLING THERMODYNAMIC INSTABILITY IN MIXING HEATERS OF TURBO INSTALLATIONS

Abstract

The relevance of the issue of modelling the conditions and consequences of thermodynamic instability in mixing heaters is confirmed by the analysis of the experience of operating turbo installations and the problem of hydrodynamic shocks and their impact on the functioning of the equipment. A thermodynamic mathematical model of heat and mass transfer processes in the volume of mixing heaters has been developed, which, unlike known approaches, takes into account the influence of fluctuating deviations of thermodynamic parameters from the equilibrium state on the conditions of thermodynamic instability. The analysis of the obtained criteria and conditions of thermodynamic instability and hydrodynamic shocks was carried out. Based on the developed model, an original method of determining the conditions and consequences of thermodynamic instability in the volume of mixing heaters is presented. The criterion of thermodynamic instability in the developed method defines the conditions of simultaneous change of pressure and mass in the two-phase volume of the mixing heater. The conditions for the occurrence of thermodynamic instability in mixing heaters are determined, which significantly depend on the ratio of steam and condensate flow rates. The results obtained in the work can be applied for: development of systems for diagnosing the state of mixing heaters based on the regularly controlled parameters of the turbo installation, substantiating technical solutions for preventing thermodynamic instability and hydrodynamic “shocks” on the design of heaters, substantiating technical solutions for modernization of turbo installation systems. These issues determine the need for further analysis of the feasibility of modernizing thermodynamic instability modelling methods in mixing heaters of NPP turbo-installations. Keywords: thermodynamic instability, mixing heaters of turbo installations