Comparative analysis of exergy efficiency of heat recovery systems of various purpose
DOI:
https://doi.org/10.31548/energiya2020.01.038Abstract
To assess the exergy efficiency of heat recovery systems, a complex approach was used, which allows us to evaluate the operation of heat recovery systems simultaneously from several positions: thermodynamic, heat engineering, and technological. In this work, within the framework of this approach, the heat-exergy efficiency criterion and exergy efficiency were used. Four types of heat recovery systems for various purposes for boiler plants were investigated. For the systems under consideration, structural schemes have been developed in which exergy flows between individual discrete elements of a simple structure are identified. The calculation of exergy characteristics was carried out using the balance methods of exergy analysis and a technique combining the methods of exergy analysis with the RP method of representing the thermodynamic balances of the system in matrix form. Based on the calculated exergy characteristics, a comparative analysis of the exergy efficiency of heat recovery systems for various purposes is carried out. According to the research results, one of the possible ways to reduce the total exergy losses in heat recovery systems is to reduce losses in the pump system and piping system. This reduction is achieved by aggregating the maximum number of functional elements of the heat recovery system in one device. It is shown that for a heat recovery scheme in which the three main elements are structurally combined in one housing, the heat-exergy criterion is reduced by 6.7 %, and the exergy efficiency is increased by 4.0 % compared to the non-aggregated heat recovery scheme. Thus, heat recovery systems with complex use of recover heat for heating various heat-transfer agents and with aggregation of the main system elements in one housing are characterized by the best exergetic indicators.
Key words: boiler plants; waste gas heat recovery, exergy losses, complex techniques; efficiency
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