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 in this study; a single slab coil oriented at an angle of 65º to the duct wall and an A-Shaped coil with an apex angle of 34º. We used Particle Image Velocimetry (PIV) to measure their in-situ air flow distributions. The results show that the air flow distributions for both of these heat exchangers are highly nonuniform with different sections subject to vastly different air velocities. We also used a momentum resistance based CFD approach to model the air flow distributions through these heat exchangers and the results agreed with the measured values, with most of the simulated velocities within 10 % of the measured velocities. The results of this study show that the velocity profile for any configuration is strongly influenced by the geometrical features 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 several features of inherently maldistributed air flowing through finned-tube heat exchangers and highlights its sources and magnitude.
Citation: Hvac&R Research
Pub Type: Journals
air flow distribution, finned tube heat exchanger, particle image velocimetry, momentum resistance CFD