Authors: R. A. Haffejee, R. Laubscher
Year: 2020
Industry: Fossil Fuel Power Generation
Keywords: Use FSE, Steady state, Validation, Comparison
ABSTRACT
"This paper describes a 1-D thermofluid network modelling methodology for air-cooled condensers (ACCs). This study focuses on modelling a utility-scale ACC system at steady-state conditions applying a 1-D network modelling approach and using a component-level discretization approach. This allowed for each cell to be modelled individually, accounting for steam duct supply behavior, and for off-design conditions to be investigated. The developed methodology was based on existing empirical correlations for condenser cells and adapted to also model double row dephlegmators, previously not observed in literature. A large 64-cell ACC system was modelled, which had a fan inlet elevation of 54m and a 10.363m fan diameter. The model was validated to site data with agreement in results. The model was also compared to the existing lumped approach, and differences were observed due to the steam ducting distribution.
The effect of increasing ambient air temperature from 25 to 35 °C was investigated, with decreasing heat rejections and increasing backpressure observed. Condensers’ heat rejection decreased with higher air temperatures, while dephlegmators’ heat rejection increased due to the increased outlet vapor pressure and flow rates from condensers. Heat transfer coefficients were also investigated, with a decrease in overall heat transfer coefficient at higher air temperatures. Off-design conditions were simulated, including hot air recirculation and wind effects through edge cells which would be due to fan failure or crosswinds. Differences in performance were found between the developed model and existing lumped approach when considering wind effects which arose when comparing wind-affected cells and non-affected cells."