Contributors to increased fan inlet temperature at an air-cooled steam condenser

Abstract

Current plant operating standards see the cooling performance of an air-cooled condenser (ACC) being calculated based on a reference air temperature measured near ground level (typically at z = 1.2 m). An increase in fan inlet temperatures above this reference temperature will result in a decrease in the ACC performance below its design value, and a subsequent reduction in turbine performance. Localised fan inlet temperature increases have traditionally been attributed to the presence of plume recirculation. A comparison of test data collected at an existing ACC and numerical data generated in a CFD analysis of the flow around the same ACC shows a discrepancy in the predicted effects of wind on fan inlet temperature. Careful analysis of the test data indicates the potential involvement of atmospheric temperature distributions in fan inlet temperature deviations. A numerical case study is conducted considering four differing atmospheric temperature distributions. It is found that such distributions, and atmospheric temperature inversions in particular, can cause measurable deviations of the fan inlet temperature from the z = 1.2 m reference value; and subsequently measurable deviations in plant behaviour from design. Selecting fan platform height as the reference elevation is shown to result in a better prediction of actual ACC performance for all atmospheric temperature distributions and wind conditions.