一様な鉛直下降流中に置かれた水平上向き加熱平板まわりの強制-自然共存対流の流動と伝熱(熱工学,内燃機関,動力など)

概要

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Experimental investigations have been carried out on combined convective flows induced around the upward-facing, horizontal heated plates placed in a vertical downward flow of forced convection. The experiments were performed both with water and air and in the ranges of the Reynolds and modified Rayleigh numbers as; 300<Re_w<5000, 10^7<Ra_w^*<10^<10> for water, and 200<Re_w<2000, 10^6<Ra_w^*<10^9 for air. The flow fields over plates are visualized with dye and smoke. The results showed that the longitudinal vortices of which axes are parallel to the flow direction appear over the plate when the buoyancy force is beyond critical, and that the onsets of the longitudinal vortices are expressed with the non-dimensional parameter as; Gr_w^*/Re_w^<2.5>=4.0 for water and Gr_w^*/Re_w^<2.5>=1.77 for air. The local heat transfer coefficients of the plate were also measured. The results showed that the coefficients are increased significantly from those of the laminar wedge flows of forced convection with increasing the buoyancy force. The mechanisms and the critical conditions for the enhancement of heat transfer were also discussed.
社団法人日本機械学会の論文
2009-11-25