TRANSIENT LIQUID CRYSTAL TECHNIQUE FOR IMPINGING HEAT TRANSFER OF INLINE AND STAGGERED JET ARRAYS

摘要

The objective of the present experimental work is the study of local heat transfer performance over a target plate under impingement of inline and staggered jet arrays by a liquid crystal thermograph technique. Three jet-to-target spacings Z (= z/d) of 3, 6, and 9 with inline and staggered jet arrays were considered at jet Reynolds numbers Re = 1500, 3000, and 4500 in three different exit-flow orientations. The results show that the local heat transfer rates are characterized by obvious periodic-type variation of Nusselt number distributions. The downstream peaks are diminished with increasing cross-flow effect. The best heat transfer performance is obtained with the cross flow exiting from both ends of the impingement channel. The inline jet array produces relatively higher local and overall heat transfer rates than those of the staggered jet array. Additionally, in the present results of 3 ≤ Z ≤ 9, higher heat transfer rates are found for the system with a smaller jet-to-plate spacing.