Efficiency of combined heat-utilization systems of boiler installations (part 2)

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DOI:

https://doi.org/10.31548/energiya2018.03.034

Abstract

The combined heat recovery system of the boiler installation, which is intended for heating the water and heating and humidifying the blowing air, is considered in the work. The results of the analysis of efficiency and optimization of the heat utilization system are presented. The analysis is based on the developed techniques. The first method is based on a combination of elements of exergy analysis with structural-variant methods, the second - on the combination of elements of the exergy analysis with methods of multi-level optimization. In the framework of the first method, a structural scheme of a heat recovery system was developed, in which all exergent flows between elements of a simple structure were identified. The thermal and exergy calculations were made, which allowed to distinguish two main elements - a surface condensing water heater and a contact heat heater and humidifier. In these elements, the change in exergy losses most significantly affects the change in the efficiency of the entire system. The optimization of some operational and structural parameters for these elements was carried out. These elements with optimal parameters are introduced into the heat recovery system. For the heat utilization system, the value of the efficiency criteria is calculated. Within the framework of the multilevel optimization method, the heat utilization system is divided into optimization levels. The block diagram and the scheme of recursive traversal of optimization levels are developed. This allows for the solution of a complex multicriterial and multi-parameter optimization problem to reconcile the solutions of local optimization problems of each level. On the basis of the developed methodology, which includes methods of multilevel optimization, the optimal values of regime and structural parameters for the specified heat recovery system are obtained. When applying these techniques, the corresponding values of the efficiency criteria of the heat recovery system are calculated. A comparative analysis of these techniques showed that the efficiency of the heat recovery system obtained by using the second method is approximately 2% lower than the efficiency criterion obtained with the use of the first method. The obtained results testify that, when applying the methodology, which includes methods of multilevel optimization, the regime and structural parameters of the heat utilization system are as close as possible to the optimal ones. Thus, the efficiency of the heat utilization system is higher when using a methodology that includes multi-level optimization methods.

Key words: heat utilization system, optimization methods, efficiency criteria.

References

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Published

2018-07-12

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