Movement of impingement heat transfer by a single circular jet with a confined wall

Impingement heat transfer and flow in the radial and circumferential direct ions by a single circular laminar jet in a flow passage with a confined ins ulated wall were estimated numerically in a three-dimensional system and we re recognized by visualization of a thermosensitive liquid crystal. Local h eat transfer is divided into three regions. The first is a two-dimensional forced convection region whose structure is a co-axial circle. The second l aminar mixed-convection region begins with the onset of a buoyancy driven f low, which corresponds to thermal plumes rising from the heated impingement surface at discrete circumferential locations. The ascending and descendin g pair flows form longitudinal streak lines in the mixed convection region. The number of pairs is found to depend on the aspect ratio of circumferent ial length and distance between nozzle and impingement surface. The third i s a three-dimensional natural convection region similar to Benard convectio n which constructs several cells. The radial Nusselt number distribution av eraged along the circumferential direction is also presented corresponding to the flow. (C) 2001 Elsevier Science Ltd. All rights reserved.