The characterization of the flow structure in test sections with complex geometries is a challenging task because of the difficulty of access and flow visualization. Even for optical flow velocimetry techniques, which are in general considered nonintrusive methods, the flow visualization can be an issue because of the poor visibility. The visibility deterioration is caused by a high seeding particle concentration, which is essential for techniques based on statistical methods, e.g. Particle Image Velocimetry. Furthermore, the inherent complex geometry of some equipment, such as tube bundle heat exchangers, requires the development of test sections composed entirely by transparent materials for optical techniques application. This paper presents an analysis of the performance of the Spatial Filter Velocimetry technique on external flows across tube bundles, in order to evaluate the benefits of using a technique that does not require a high particle concentration in a complex geometry test section. The experimental vector velocity fields were obtained in a tube array made of acrylic composed of 20 rows of 4 tubes, each with 20mm O.D. mounted in a normal triangular configuration and transversal pitch per diameter ratio of 1.25. The accuracy of SFV was evaluated by comparing the volumetric flow rates estimated by the experimental vector velocity fields with the volumetric flow rates measured by a volumetric flow meter. Moreover, a comparison between the velocity data with results obtained through CFD simulation is presented. The parameters of the turbulent model adopted for the CFD simulations were defined based on the velocity results obtained through SFV. In addition, the total pressure drops obtained from differential pressure transducers were compared with the results obtained through the CFD simulations. The experiments were conducted for Reynolds numbers of 909, 1842 and 3902. The results indicate that the SFV technique provides accurate results since the volumetric flow rates estimated by the experimental velocity field agrees with the measured volumetric flow rates within the uncertainty range of the volumetric flow meter. In addition, the velocity profiles obtained through the SFV technique agree with the CFD simulations results, which indicate consistent results for both. Therefore, the numerical and experimental results indicate that the Spatial Filter Velocimetry technique provides accurate velocity data and is suitable to be applied to complex geometries, especially in regions distant to the test section wall due to the satisfactory visibility. Moreover, the spatial and temporal resolution adopted in the experiments were sufficiently high to characterize the flow structure and provide detailed information for the turbulence characterization.


A Comparison of the Flow Structure in a Normal Triangular Tube Array Obtained Based on the Sfv Technique and on Cfd Analyses

Division / Sponsors: 
Heat Transfer Division (HTD), Fluids Engineering Division (FED)

Heat Transfer Summer Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2020/volume/83709

18th International Conference on Nanochannels, Microchannels, and Minichannels
Paper Proceedings: https://asmedigitalcollection.asme.org/ICNMM/ICNMM2020/volume/83693

Fluids Engineering Division Summer Meeting
Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2020/volume/83716

HT-ICNMM2020 - Virtual Conference, SHTC - Virtual Conference, FEDSM2020 - Virtual Conference

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