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Air-Side Velocity Distribution in Finned-Tube Heat Exchangers



David A. Yashar, Hong H. Cho


The performance of finned tube heat exchangers is greatly affected by the distribution of the air that passes through it. The air side velocity distribution is largely left unknown because it is difficult to measure accurately. In this study, we examined the air velocity distribution approaching finned-tube heat exchangers under three different common installation configurations and report the results. To this end we used a novel, laser based technique called Particle Image Velocimetry (PIV) to measure and characterize the velocity profile for three heat exchangers. The heat exchangers examined in this study include a vertically oriented single slab coil, a single slab coil placed at an angle of 65 to the duct wall, and an A-Shaped coil. The measurement results show that the velocity profile for any configuration is strongly influenced by the features within the duct and the orientation of the heat exchanger, and therefore it is generally not uniform. The information in this report documents the magnitude and type of this mal-distribution commonly realized in these systems, what features cause it, and which regions are most affected. Computational Fluid Dynamics (CFD) simulations were carried out to simulate the air flow through the test subjects used for the PIV measurements. We employed momentum resistance models to simplify the computational domains and reduce computer time. Our simulation results showed very good agreement with the measured velocity profiles in each case. This work verifies that CFD can be accurately applied as a tool to determine the velocity profile. CFD is preferred to laboratory experimentation because of its speed and simplicity.
Journal of Research (NIST JRES) - 7474
Report Number


Computational Fluid Dynamics (CFD), finned-tubeheat exchanger, Particle Image Velocimetry (PIV), velocity profile


Yashar, D. and Cho, H. (2007), Air-Side Velocity Distribution in Finned-Tube Heat Exchangers, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed May 30, 2024)


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Created December 17, 2007, Updated February 19, 2017