Development of complex methods for exergetic losses calculating in heat transfer through wall in air-heater heat utilizers

Abstract

Ensuring high economic indicators of power plants of various purposes, which include waste gas heat utilization systems, is possible with the use of effective heat utilization equipment. One of the criteria for evaluating the thermodynamic perfection of power plants is the amount of exergy losses in the structural elements of the plant. A decrease in exergy losses corresponds to an increase in exergy efficiency. Determination of the structural elements in the heat utilization system, in which the maximum exergy losses are localized, will allow to influence them in a targeted manner in order to increase the exergy efficiency of the installation. The paper presents the results of the development of complex methods for calculating local exergy losses in the processes of heat transfer through flat and cylindrical walls of air-heated heat exchangers, which are included in the heat utilization systems of power plants of various purposes. Complex methods are based on integral equations for calculating exergy losses, as well as differential equations of heat transfer theory when applied to heat utilization systems. The classification of exergy losses for heat utilization systems of power plants has been carried out, and the location and type of local exergy losses have been determined. Three types of local exergy losses are considered: losses during heat transfer from the heat carrier to the wall, heat transfer from the wall to the heat carrier, and exergy losses in heat conduction processes. A system of integrodifferential equations was developed and analytical expressions were obtained for the calculation of local exergy losses in heat transfer processes through the flat and cylindrical walls of air-heating heat exchangers. The introduction of new complex research methods expands the possibilities of using exergy analysis methods to increase the exergy efficiency of heat utilization systems. Research using the specified methods will allow to develop heat utilization systems with high indicators of energy and exergetic efficiency.