Efficiency of combined heat-utilization systems of boiler installations (part 1)

Authors

  • N. Fialko Institute of Engineering Thermophysics of NAS of Ukraine ,
  • А. Stepanovа Institute of Engineering Thermophysics of NAS of Ukraine ,
  • R. Navrodskaya Institute of Engineering Thermophysics of NAS of Ukraine ,

DOI:

https://doi.org/10.31548/energiya2018.01.078

Abstract

The aim of the work is to increase the efficiency of the installation, which consists of a boiler and a combined heat recovery system for heating water and blast air. For this purpose, the analysis of losses of exergic power in the installation under different operating conditions of the boiler was carried out. The analysis of efficiency and optimization of such facilities should be based on modern integrated approaches. These approaches include statistical methods of experiment planning, methods of exergic analysis, methods of the theory of linear systems, structural, structural-variant methods, methods of multilevel optimization, etc. The development and application of techniques that are based on a combination of these methods make it possible to maximize the effectiveness of such installations. For the installation under investigation, the efficiency analysis was carried out on the basis of the developed technique, which included elements of exergic analysis and the RP-representation of thermodynamic balances in matrix form. The developed technique was applied to an estimation of efficiency of installation at various operating modes of a boiler. To implement the methodology, a structural diagram of the installation has been developed, in which thermodynamic flows between individual discrete elements of a simple structure are indicated. The block diagram serves to determine the characteristics of the streams and elements of the input matrix. To build a complete input matrix, mass, energy and exergy balances in matrix form were also recorded. The least losses of exergy power for all boiler power values occur in the air-heating heat recovery unit and in the gas heater. The relative contribution of the hot-water heat recovery unit to the total irreversibility of the processes in the heat recovery unit increases with increasing boiler output. The total contribution of the pumping system and the piping system to the total irreversibility of the heat recovery unit is quite significant for all boiler output values. It decreases with increasing boiler output. The graphs that illustrate the loss of exergy power in the heat recovery system and in the hot water heat recovery boiler have two distinct sections. In the first section there is an insignificant increase in the losses of exergy power in the heat recovery system. Here, the main losses of exergy power are attributable to the pumping system and to the pipeline system. In the second section, the loss of exergy power in the heat recovery system begins to increase sharply. Here, the main losses of exergy power are attributable to the water heat recovery. It is more expedient to regulate losses of exergic power in the pumping system and piping system than in heat recovery units. This made it possible to establish that the optimal operation of the installation takes place at a boiler capacity that is 50 ... 60% of its installed capacity.

 Key words: heat recovery system, exergy analysis, thermodynamic balances, matrix.

References

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Fialko, N. M., Stepanova, A. I., Navrodskaya, R. A. еt al. (2015). Analiz effektivnosti teplo-utilizatsionnoy ustanovki dlya nagrevaniya i uvlazhneniya du-t'yevogo vozdukha kotloagregata [Analysis of the efficiency of the heat recovery unit for heating and humidifying the blast air of the boiler unit]. Promyshlennaya teplotekhnika, 37(4), 71-79.

Published

2018-04-23

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