The use of air-cooled condensers (ACCs) has seen a large uptake in the petrochemical and power generating industry. Typical power plant ACCs utilise axial flow fans approximately 9 m in diameter situated 45 m above ground level. Previous studies have shown that ACCs are adversely affected by environmental conditions, including dry-blub temperature and cross-winds. The complex flow phenomena associated with ACCs under cross-wind conditions require careful consideration in ensuring adequate sizing is attained to meet the heat rejection demands. This has led to an increase in the development of modelling methodologies to adequately predict ACC performance for different environmental and changing heat load conditions. Computational fluid dynamics (CFD) is a toolkit that has been shown to adequately model air-side characteristics, whereas system level modelling software has also been shown to adequately model steam-side characteristics. This study builds on a previous study and aims to determine adequate discretization level of the heat exchanger in order to combine CFD and system-level modelling software to predict the performance of an ACC cell in an ACC bank. This co-simulation approach is applied by using ANSYS Fluent® R1 for the CFD computations and Flownex® 8 for the system-level model.

A single ACC cell situated on the periphery is considered for co-simulation in a 4x3 ACC bank situated 8 m above ground level. The axial flow fan is modelled using the Extended Actuator Disk Model (EADM) and the heat exchanger represented as a porous medium. An axial flow fan currently in use in the power generating industry, designated as the A-fan, is used. In accordance with findings from previous studies, the heat exchanger plenum is modelled using an A-frame configuration. The ACC support struts and fan walkway are also modelled as geometrical structures. Steam characteristics are represented using a 1-D, implicit solver and the steam is represented as a homogeneous two-phase mixture. The heat exchanger is discretised into sections of 3x3, 6x6 and 3x9 and the performance in the form of fan volumetric flow rate, fan power consumption, heat transfer rate and steam quality at the cell outlet is measured. The ACC is subjected to cross-winds of 0, 3, 6 and 9 m/s and a comparative performance analysis is undertaken to ascertain adequate level of discretization. The novelty of this co-simulated approach lies in the correct depiction of steam-side characteristics in the heat exchanger subjected to maldistributed inlet flow conditions present in cross-wind conditions. The model is also able to characterise ACC performance using steam outlet quality as the metric.


A Co-Simulation Approach to Modeling Air-Cooled Condensers in Windy Conditions

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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