Makatar Wae-hayee, Perapong Tekasakul and Chayut Nuntadusit

pp. 203 - 212

Abstract

The effect of jet arrangements on flow and heat transfer characteristics was experimentally and numerically investigated
for arrays of impinging jets. The air jets discharge from round orifices and perpendicularly impinge on a surface within a
rectangular duct. Both the in-line and staggered arrangements, which have an array of 6×4 nozzles, were examined. A jet-toplate distance (H) and jet-to-jet distance (S) were fixed at H=2D and S=3D, respectively (where D is the round orifice
diameter). The experiments were carried out at jet Reynolds number Re=5,000, 7,500 and 13,400. Temperature distributions on
the impingement surface were measured using a Thermochromic Liquid Crystal sheet, and Nusselt number distributions were
evaluated using an image processing method. The flow characteristics on the impingement surface were visualized using the
oil film technique. The numerical simulation employed to gain insight into the fluid flow of jets between the orifice plate and
the impingement wall was via computational fluid dynamics. The results reveal that the effect of crossflow on the impinging
jets for the staggered arrangement is stronger than that in the case of in-line arrangement. In the latter case of in-line arrangement, the crossflow could pass throughout the passage between the rows of jets, whereas in the former case the crossflow
was hampered by the downstream jets. The average Nusselt number of the in-line arrangement is higher than that of the
staggered arrangement by approx. 13-20% in this study. 

Keywords

• array of impinging jets
• in-line and staggered arrangement
• crossflow
• thermochromic liquid crystal sheet (TLCs)
• oil film technique
• CFD