Study of junction flows in louvered fin round tube heat exchangers using the dye injection technique

Journal Article · Mon Nov 15 04:00:00 EST 2010 · Experimental Thermal and Fluid Science

DOI:https://doi.org/10.1016/J.EXPTHERMFLUSCI.2010.05.006· OSTI ID:21350392

Huisseune, H; Willockx, A; De Paepe, M ^[1]; T'Joen, C ^[1]; De Jaeger, P ^[1]

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1. Department of Flow, Heat and Combustion Mechanics, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent (Belgium)

Detailed studies of junction flows in heat exchangers with an interrupted fin design are rare. However, understanding these flow structures is important for design and optimization purposes, because the thermal hydraulic performance of heat exchangers is strongly related to the flow behaviour. In this study flow visualization experiments were performed in six scaled-up models of a louvered fin round tube heat exchanger. The models have three tube rows in a staggered layout and differ only in their fin spacing and louver angle. A water tunnel was designed and built and the flow visualizations were carried out using dye injection. At low Reynolds numbers the streakline follows the tube contours, while at higher Reynolds numbers a horseshoe vortex is developed ahead of the tubes. The two resulting streamwise vortex legs are destroyed by the downstream louvers (i.e. downstream the turnaround louver), especially at higher Reynolds numbers, smaller fin pitches and larger louver angles. Increasing the fin spacing results in a larger and stronger horseshoe vortex. This illustrates that a reduction of the fin spacing results in a dissipation of vortical motion by mechanical blockage and skin friction. Furthermore it was observed that the vortex strength and number of vortices in the second tube row is larger than in the first tube row. This is due to the thicker boundary layer in the second tube row, and the flow deflection, which is typical for louvered fin heat exchangers. Visualizations at the tube-louver junction showed that in the transition part between the angled louver and the flat landing a vortex is present underneath the louver surface which propagates towards the angled louver. (author)

• OSTI ID: 21350392
• Journal Information: Experimental Thermal and Fluid Science, Journal Name: Experimental Thermal and Fluid Science Journal Issue: 8 Vol. 34; ISSN 0894-1777; ISSN ETFSEO
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
42 ENGINEERING
BOUNDARY LAYERS
CONFIGURATION
DESIGN
FINS
FLOW VISUALIZATION
FLUID FLOW
FRICTION
HEAT EXCHANGERS
Horseshoe vortices
Junction flow
Louvered fins
OPTIMIZATION
PERFORMANCE
REYNOLDS NUMBER
THERMAL HYDRAULICS
TUBES
VORTICES