The supercritical carbon dioxide Brayton power cycle is getting commercially attractive for power generation due to its numerous advantages like zero water discharge, compactness, and low environmental emission and potential to reach high thermal efficiency. A typical recuperated closed cycle consists of three heat exchangers (main heat exchanger, cooler, and recuperator) and two turbomachinery (turbine and compressor). The cooler using ambient air for cooling is the focus of this study. The steady-state air cooler model is set up to study the effect of air cooler size on cycle efficiency. The effect of change in the ambient air temperature on the air cooler pinch point for different air cooler sizes is analyzed using the transient air cooler model. The simulation is set up for the design of the approximately 100 MWe cycle with an operating temperature of 700 °C and a pressure of 250 bar. Transient calculations are done using LMS AMESim. LMS AMESim is the Siemens PLM commercially available software. This work thus serves as a framework to develop a basis for the design of the air cooler in the power cycle as a function of transient operating conditions.