Experimental tests of jet impingement heat transfer on a flat surface were performed by using the infrared camera for the pulsed jets with a constant operating frequency of 10 Hz and duty cycle of 50%. Comparisons with continuous jets were made at the jet Reynolds numbers ranging from 5 000 to 20 000 and the dimensionless nozzle-to-surface distances ranging from 2 to 8. The results show that the pulsed jet possesses the same basic heat transfer features as the continuous jet impingement, such as increase of the convective heat transfer coefficient with the increase of jet Reynolds numbers and rapid decrease of the local convective heat transfer coefficient along the radial direction. However, different from the continuous jet, the pulsed jet produces some differences in heat transfer either at the stagnation point or the wall jet zone. This is tightly associated with the jet Reynolds number and nozzle-to-surface distance. In general, the pulsed jet impingement exhibits its advantage over the continuous jet at larger dimensionless nozzle-to-surface distances, especially at a high jet Reynolds number. At a small dimensionless nozzle-to-surface distance, the continuous jet is demonstrated to achieve better heat transfer than the pulsed jet. For Re=20 000, the pulsed jet produces a slight improvement of the region-averaged convective heat transfer relative to the continuous jet only when the specified region for average use has a large radius beyond three times of the jet-nozzle diameter.
LYU Yuanwei
,
ZHANG Jingzhou
,
TANG Chan
,
SHAN Yong
. Experiment of convective heat transfer of pulsed jet impingement on a flat surface[J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2018
, 39(4)
: 121695
-121695
.
DOI: 10.7527/S1000-6893.2017.21695
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