Heat transfer of combined forced and natural convection from horizontal cylinder to air

✍ Scribed by Kenzo Kitamura; Kazuhiro Mototani; Fumiyoshi Kimura

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 686 KB
• Volume: 36
• Category: Article
• ISSN: 1099-2871
• DOI: 10.1002/htj.20180

✦ Synopsis

Experimental investigations have been carried out for combined convective flows of air induced around uniformly heated, horizontal cylinders. Three cases of aiding, opposing, and cross flows were examined. The experiments covered the ranges of the Reynolds and modified Rayleigh numbers of Re d = 50 to 900 and Ra d * = 5 × 10 4 to 3 × 10 6 . The flow fields around the cylinders were visualized with smoke. The results showed that separation points gradually shift from those of the forced convection to the top edge of the cylinder with increasing wall heat fluxes. The local heat transfer coefficients of the cylinders were also measured. Although the local coefficients show complex variations with the forced flow velocities and the wall heat fluxes, the overall coefficients become higher than those estimated from pure forced and natural convections throughout the cases of aiding, opposing, and cross flows. Moreover, it was confirmed that the overall Nusselt numbers as well as the separation points can be predicted with the non-dimensional parameter (Gr d * / Nu d Re d

2

).