Impingement heat transfer of staggered arrays of air jets confined in a channel

Abstract

Impingement heat transfer of circular air jets confined in a channel was experimentally investigated. The impingement plate was exerted with a constant surface heat flux. Five jets, including one center jet and four neighboring jets, in staggered arrays were considered. The considered jet Reynolds number ( Re) was in the range 5000–15,000; the jet height-to-jet diameter ratio ( H/ d) was in the range 1.0–4.0; the jet spacing-to-jet diameter ratio ( S/ d) was in the range 4.0–8.0; the jet plate width-to-jet diameter ratio ( W/ d) was in the range 6.25–18.75. Two jet plate length-to-jet diameter ratio ( L/ d), 31.7 and 83.3, were individually arranged. For the center jet with a specific Reynolds number, its stagnation Nusselt number was found to linearly increase with the jet Reynolds number of the four neighboring jets. For all the five jets with the same Reynolds number, the correlation result shows that the stagnation Nusselt number of the center jet is proportional to the 0.7 power of the Re and the −0.49 power of the W/ d. A weak dependence of the stagnation Nusselt number on H/ d, S/ d and L/ d was found.