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Visualization of Mechanical Processes: An International Online Journal
EFFECTS OF THE SWIRL-TYPE MIXED CONVECTION ON WALL HEAT TRANSFER IN A HORIZONTAL RECTANGULAR DUCT WITH HEATED AND COOLED SIDE WALLS AT VARIOUS ASPECT RATIOS
Graduate School of Medicine and Engineering, University of Yamanashi, Takeda 4-3-11, Kofu, Yamanashi 400-8511, Japan
Department of Education, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi, 400-8511, Japan
This paper describes the effect of aspect ratios on swirl-type mixed convection and heat transfer in a horizontal rectangular duct with heated and cooled side walls. The working fluid was water, and the range of the aspect ratio Ar was 0.2â‰¤Arâ‰¤10. The flow behavior was visualized by the dye-injection method and three-dimensional numerical analysis. In the numerical analysis, the dimensionless governing equations were solved using the simple algorithm and quick scheme through the control volume. The Reynolds number based on the hydraulic diameter Re at the inlet was 100, and the value of the Richardson number Ri (=Gr/Re2), where Gr is the Grashof number based on the height of the duct, was 16.16. The results show that the swirl flow was generated along the main flow direction. The absolute maximum vertical and horizontal velocities, Vmax and Wmax, exist near the wall, and these values were estimated using the modified Richardson number Ri*, which was taken as the modified Grashof number based on the hydraulic diameter. The pitch length of the swirl flow affected the aspect ratio, and was shortest near the range of Ar=0.5âˆ¼1. Moreover, an equation for predicting the pitch length was derived using the Vmax and Wmax, and the heat transfer behavior corresponding to the flow was discussed.
KEY WORDS: swirl-type mixed convection, horizontal rectangular duct, aspect ratio, pitch length, heat transfer, dye-injection method, numerical analysis
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