In a packaged air-conditioning unit, a non-ideal airflow pattern arises due to the arrangement of the evaporator coil with respect to the fan. This can result in a reduction of heat transfer across the evaporator. The purpose of this study was to formulate a suitable CFD (computational fluid dynamics) model of the airflow and heat transfer inside the unit. This computational model provided a reasonable prediction of the airflow in the unit near the evaporator and the centrifugal fan. The CFD model was validated by comparing predicted flow characteristics to actual measurements of velocity components, pressure, and temperature of the air in the main regions of the unit. The overall model showed acceptable agreement with some experimental results. Variation of some geometric design parameters was modeled to predict their effect on the thermal and flow performance of the unit.