Exergy analysis of a heat supply system with a lower temperature of return delivery water

The questions of evaluation of energy efficiency of municipal heating and electric power supply systems based on the combined heat and power supply plant (CHPP) with a reduced temperature of return delivery water are considered in the paper. As a method of reducing the return delivery water temperature, using heat absorption transformers (HAT) at central heat supply stations operating as absorption heat-exchange facility was considered. The exergetic efficiency was chosen as an evaluation criterion, because, given the difference in kinds of energy in the system, it allows to perform both relative and absolute estimates of thermodynamic effectiveness as well as takes into account the losses from non-equilibrium of processes in the system. Results are given of HAT multiparameter analysis that were obtained on the basis of a developed mathematical model, the reliability of which was experimentally tested. During analysis of the heat supply system, one should take into account the influence of return delivery water temperature on consumption of heat-transfer agents and power consumptions on driving the recycling pumps in the heating network and pumps in the consumer network. Additional components are inntroduced into the equation for determining the exergetic efficiency of CHPP. The traditional heat supply system is compared to the central heat supply station and the new system with an absorption transformer AT (central heat supply station) for different temperatures of delivery water in the flow line. The relative correspondence method proposed by V. P. Motulevich was used for the comparative analysis. The results are analyzed by the following lines of the heat supply system: Source-AT (central heat supply station), SourceConsumer. In the Source-Consumer line, a considerable increase is shown of exergetic efficiency in the new system at a rather high temperature of delivery water in the flow line. This is due to variation of power consumption on driving the recycling pumps and the generator unit capacity gains. Turbine-generator set T-100-130TMZ is selected as a source.

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