Evaluation of the efficiency of the air heater of the heat-recovery system based on exergetic analysis methods
DOI:
https://doi.org/10.31548/energiya2019.02.005Abstract
Abstract. Ukraine has high potential for the implementation of efficient heat recovery technologies, therefore the problem of their development is relevant for the energy sector of the country. In order to successfully solve this problem in the study of efficiency and optimization of heat recovery installations, it is necessary to use modern complex methods based on the application of exergy analysis methods in combination with other modern research methods. A well-grounded selection of techniques increases the effectiveness of research, which increases the efficiency of the heat recovery device. This is due to the fact that when designing a heat recovery device, it becomes possible to use parameters that are as close to optimal as possible. The efficiency of the elements of the heat recovery equipment of boiler plants is determined by the level of exergy losses. The indicated losses are related to the nonequilibrium heat exchange in the system, the processes of thermal conductivity, the hydrodynamic resistance in the movement of heat carriers. To calculate the exergy losses in the heater of the heat recovery system of the boiler plant, a complex method based on the calculation of dissipation of exergy is used. The technique allowed to divide the exergy losses in accordance with the causes of their occurrence. Exergy losses were calculated using the appropriate formulas for the calculation of exergy dissipators, and the influence of the basic thermophysical parameters of the heater was analyzed on them. The greatest exergy losses in the heater are associated with the heat transfer processes in the system. As the boiler's heat output decreases, the exergy losses determined by the heat transfer are significantly reduced, with a decrease in the losses associated with the thermal conductivity and the heat transfer media movement. The regularities of the change of dissipation of exergy with changes in heat transfer coefficients are analyzed. The increase in the coefficients of heat transfer leads to an increase in the loss of exergy power, which is more pronounced for the heat transfer from the air. With increasing heat transfer coefficients above 0.040 kW/m2·К, these losses begin to increase significantly. The area of the main characteristics of the heater is determined, within which a minimum level of exergy power loss is ensured.
Key words: boiler plants; exergy losses; dissipation of exergy
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