Challenges in predicting steam-side pressure drop and heat transfer in air-cooled power plant condensers

Abstract

Conventional power plant condensers operate at unsustainably high cooling water consumption rates (2–28 m3 MW h−1). Dry air-cooled condensers (ACCs) can enable reduced water consumption in power plants. However, ACCs are rarely employed because of the substantial decreases in condenser performance and power plant efficiencies compared to wet-cooled systems. ACC studies typically focus on air-side transport, assuming that the effects of steam-side pressure drop and thermal resistance are small. The objective of the present investigation is to scrutinize this assumption – quantifying the influence of steam-side effects on ACC operation. A detailed model of a representative ACC is formulated. Model results demonstrate that condensation heat transfer and pressure drop are poorly characterized at ACC operating conditions. Predicted power plant efficiency varies by 0.7% with different condensation heat transfer models. Additionally, predicted plant efficiencies vary depending on which pressure drop correlation is employed. The differences are exacerbated at low steam saturation pressures (∼4 kPa), where the cycle efficiencies range from 36.0% and 37.7% between different pressure drop correlations. Results from this study indicate that both steam side and air-side effects must be considered to improve ACC performance. Some methods for enhancing in-tube condensation are mentioned, and future ACC research needs are discussed.