ЕФЕКТИВНІСТЬ ПЛАСТИНЧАТИХ ТЕПЛОУТИЛІЗАТОРІВ ТЕПЛОУТИЛІЗАЦІЙНИХ СИСТЕМ

The development and application of modern integrated methods for studying the efficiency of heat recovery systems and their individual elements enables ensuring their maximum efficiency. These methods are based on a combination of methods of exergic analysis with statistical methods of experiment planning, methods of the theory of linear systems, thermodynamics of irreversible processes, etc. A method is developed for calculating the losses of exergic power in heat conduction processes for a gas-air plate heat exchanger. Losses of exergic power occur when heat is transferred through the cross-section of the heat recovery plate. The methodology is based on a complex approach combining exergy methods with methods of thermodynamics of irreversible processes. The mathematical model of the investigated processes includes the exergy equation, the balance equation of exergy and entropy, the equation of continuity, the equation of phase motion, the energy equation, the balance equation for enthalpies, the Gibbs equation and the heat equation for boundary conditions of the third kind for an unbounded plate. A plate of a gas-air plate heat exchanger was modelled as an unlimited plate thickness. When obtaining formulas for calculating the losses of exergic power, the local differential equation of the exergy balance obtained earlier was used. In this equation, one of the terms determines the losses of exergy power, which are caused by the irreversibility of the processes. Such losses are related to thermal conductivity, phase viscosity, phase-to-phase heat transfer and friction between phases. On the basis of this equation and the solution of the heat equation under boundary conditions of the third kind, formulas are obtained for calculating the losses of exergy power. Calculations of total losses of exergic power in a gas-air plate heat exchanger and losses of exergic power in heat conduction processes under various operating conditions of the boiler are performed. It is established that losses of exergic power in heat conduction processes in a gas-air plate heat exchanger make up 8.6-11.6 % of the total losses of exergy power and depend on the operating mode of the boiler. Changing in the necessary direction the thermophysical characteristics of the gas-air plate heat exchanger, it is possible to reduce the loss of exergy power.