Abstract
Crosswind has an adverse impact on the performance of an indirect dry cooling system. In order to mitigate the adverse influence, this study redistributed the circulating cooling water among air-cooled heat exchanger sectors so that the performance of the indirect dry cooling system could be improved. An evolution strategies algorithm combined with numerical effectiveness-based heat exchanger model was established to minimize the operation costs of the whole system. Based on a 660 MW practical power plant, optimal circulating cooling water operation strategies under varied crosswind speeds and ambient temperatures were calculated to show its application. According to the calculated results, the performance of the indirect dry cooling system could be enhanced by optimizing circulating cooling water distribution under any crosswind speed, especially under high ambient wind speeds. There is a slight promotion of the coal savings with a rise in ambient temperature: improvements of about 5%. The standard coal consumption rate could save as much as 2.50 g/kWh under crosswind speed of 10 m s−1 and ambient temperature of 32 °C, compared to the 0.1 g/kWh under crosswind speed of 2 m s−1 and ambient temperature of 32 °C.
Highlights
In arid regions, many thermal power plants adapt the indirect dry cooling system to cool the exhausted steam of a steam turbine, because this kind of cooling system has outstanding water saving ability [1]
The optimal circulating cooling water distributions which lead to the minimum standard coal consumption rates under different ambient temperatures and crosswind speeds were calculated
(2) For the optimal circulating cooling water distribution, the difference of water mass flow rates among sectors becomes bigger with the increase in crosswind speed
Summary
Many thermal power plants adapt the indirect dry cooling system to cool the exhausted steam of a steam turbine, because this kind of cooling system has outstanding water saving ability [1]. The main idea of this approach is to re-distribute the circulating cooling water among air-cooled heat exchangers, so that the performance of NDDCT under crosswind condition could be improved. This approach was firstly proposed by Li et al [28], their distribution method was that for one heat exchanger, the proportion of water mass flow rate to the total was equal to the proportion of air mass flow rate to the total. In order to obtain the standard coal consumption rate, Pw, which means the power required to pump circulating cooling water through air-cooled heat exchangers, is calculated as,. Where Dms and Dreh are the mass flow rate of main steam and reheat steam, hms and hreh are the specific enthalpy of main steam and reheat steam, Qsc is calorific value of standard coal, ηb and ηp, which are regarded as constant, represent the effectiveness of boiler and pipeline, respectively
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