CFD modelling of the indoor unit of an air conditioner

Abstract

Air conditioning (AC) systems are crucial for maintaining thermal comfort and indoor air quality. With the growing demand for efficient cooling, understanding AC unit performance is crucial for improving efficiency and reducing operational costs. Monitoring airflow dynamics is key to optimizing system design and energy efficiency. This study investigates the airflow behaviour within a split-type indoor air conditioning (SAC) unit using computational fluid dynamics (CFD) modelling, supported by experimental validation. A two-dimensional transient CFD model was developed in ANSYS Fluent 2024 R2 software to simulate airflow at three different fan speeds. The CFD analysis revealed several critical airflow patterns within the indoor SAC unit, including three major recirculation zones: an eccentric vortex at the periphery of the impeller, a recirculation zone at the intake of the impeller near the rear wall and another at the unit outlet. The eccentric vortex, formed by the interaction between the rotating fan and the stationary vortex wall, created low-velocity regions and reversed flow. Additional recirculation zones formed due to flow disruptions caused by internal components including the rear and vortex walls, while stagnation regions around sharp geometries indicated potential obstructions or redirection of airflow. The recirculation zones contributed to the displacement of the eccentric vortex, thereby reducing discharge efficiency and affecting overall air delivery. The highest velocity occurred along the rear wall due to centrifugal force, resulting in a jet flow that remained attached to the rear wall. Although the shape of the jet flow deviated from typical CFD literature, it was supported by experimental observations, emphasizing the importance of realworld validation. Overall, this study demonstrates the effectiveness of CFD in capturing key airflow behaviours in indoor SAC units and provides a basis for further research on optimizing airflow performance.