Jet impingement heat transfer on target surfaces with longitudinal and transverse grooves

This work reports detailed impingement heat transfer measurements on grooved surfaces using transient liquid crystal method. These grooves are machined on the target surfaces with either parallel or orthogonal to the exit flow direction, and are aligned either with the jet holes (inline pattern) or between the jet holes (staggered pattern). The jet-to-target plate spacing (Z/d) is 3 and the average jet Reynolds numbers are from 2500 to 7700. Results show that heat transfer is enhanced near grooves. However, the grooves underneath the jet holes hinder the impingement flow and the jet impingement heat transfer is reduced. Although local heat transfer shows distinct distributions, there is no significant difference in overall-averaged Nusselt numbers on the grooved surfaces and the highest heat transfer enhancement by grooved surfaces is 15%.