An experimental and computational study of approach air distribution for slanted and A-shaped finned-tube heat exchangers

Abstract

One of the most influential factors of the performance of a finned-tube heat exchanger is the distribution of the air passing through it; therefore, it must be known in order to produce a highly efficient design. We examined two different common style air-to-refrigerant, finned-tube heat exchangers: a single-slab coil oriented at an angle of 65° to the duct wall and an A-shaped coil with an apex angle of 34°. We used particle image velocimetry (PIV) to measure their in-situ airflow distributions. The results show that the airflow distributions for both heat exchangers are highly nonuniform with different sections being subject to vastly different air velocities. We also used a momentum resistance-based computational fluid dynamics (CFD) approach to model the airflow distributions through these heat exchangers. The modeled results agreed with the measured values, with most of the simulated velocities falling within +/-10% of the measured velocities. The results of this study show that the velocity profile for any configuration is strongly influenced by the geometry of the heat exchanger and other features in its proximity and, therefore, each installation configuration will have its own unique velocity distribution. The information presented in this paper documents the maldistribution of airflowing through finned-tube heat exchangers and highlights the sources and magnitude of the nonuniformities.