EXERGY ANALYSIS OF A COGENERATION SYSTEM FOR UTILIZATION OF WASTE HEAT OF INDUSTRIAL ENTERPRISES

The object of research is the energy processes occurring in the cogeneration system for the utilization of waste heat of industrial enterprises, consisting of a steam turbine plant and an absorption heat pump. One of the most problematic places during the development and design of such systems is that the thermal calculation of absorption heat pumps as a whole is a rather difficult task. This is due to the presence of several interconnected heat exchangers and the complexity of the thermodynamic and mass transfer processes occurring in them. During the research, modern methods of analysis of thermodynamic systems were used, based on the application of the theoretical apparatus of technical thermodynamics and the theory of heat and mass transfer. On the basis of mathematical modeling of heat and mass transfer processes for the cogeneration system under consideration, a software package for calculating its thermodynamic and exergy characteristics is built with the aim of conducting numerical studies of its energy efficiency indicators. A database is obtained for calculating the thermophysical properties of a water-ammonia solution taking into account changes in its concentration to identify the solution state parameters at the nodal points of the cycles. Based on a numerical experiment, the energy and exergy parameters of the system are analyzed with a variation of 4 factors: 1) condensation temperature of the spent water steam in a steam turbine plant; 2) heating process water temperature at the inlet to the steam generator of the steam turbine plant; 3) reverse delivery water temperature at the inlet to the heat pump; 4) mass flow rate of delivery water. A generalized regression equation of the functional relationship of the exergy efficiency of the elements of the cogeneration system and the entire system as a whole is obtained. The impact coefficients of exergy efficiency of elements on the thermodynamic perfection of the entire system are analyzed. Thanks to the method of exergy analysis used in the research, it is possible to identify the nature of external and internal losses both in cycles in general and in individual elements of the cogeneration system under consideration. And also the ways to improve its scheme and design are outline