Evolution and behavior of condensing steam flows under unsteadiness

Abstract

The primary cause of unsteadiness in a concentrated solar power (CSP) plant is cloud passing and the subsequent shadowing of its solar fields. The effects of these transients on a condenser pipe of an air-cooled condenser, typical of CSP applications, are numerically investigated. The parameters that are considered to be impacted by unsteadiness are the condenser inlet mass flow rate, the condenser inlet vapor quality and the ambient temperature. These perturbations are represented by downward step functions to reflect the unanticipated change due to cloud passing. Reasonable nominal values and reasonably large drops of 90%, 0.15 and 15 °C in the steam mass flow rate, vapor quality and ambient temperature, respectively, are identified and implemented into the transient simulations. The transient response of the fluidic and thermal characteristics of the condensing steam flows to the imposed perturbations are examined. Interestingly, prompt responses to the imposed perturbations are observed. The heat transfer coefficient increases sharply by around 160% and 150% upon the imposed perturbations in mass flow rate and ambient temperature, respectively, before reaching their corresponding quasi-steady state values. The findings have, therefore, implications in the design of air-cooled condensers which are subjected to sudden temporal variations in boundary conditions.