Thefirst research in the pulsed impingement jet has been performed by Nevins andBall, they studied on the heat transfer of one pulsed jet on the flat surfaceand showed that heat transfer rate of pulsed jet is nearly equal with steadystate impingement jet. Tests for Reynolds number 1200

Pulsed jet impingement hasnot been studied for many years due to Nevins’s prediction about pulsed jeteffect, research in this field was stopped for two decades. In the late ’80 andearly 1990, several research groups started to study on the pulsed jetimpingement. Kataka and Sugaro investigated the effect of secondary flow on theheat transfer from the surface. They showed that heat transfer of stagnationpoint in impingement jet is affected by large structure of flow. Existence ofthese large structures reported in the oscillated flows. Azevedo et al 3investigated the impingement heat transfer for wide range of pulsedfrequencies. They generated the oscillated jet by ball valve which rotated withspecific frequency.

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Mladin and Zumbrunnen investigated the effect of profile,frequency and amplitude of pulsed jet on the instantaneous convection andaverage convection heat transfer for flat surface. They reported that there isa threshold Strohal number which is lower than this value there is no significantchange in heat transfer. They declared 0.26 as threshold Storhalnumber. Zumbrunnenand Aziz confirmed this found by investigation of heat transfer rate betweenwater jet and flat surface which is under heat flux constant. This experiment was donefor St>0.26 and increase by 100% in heat transfer was reported.  But Silver at el 6 use0.


Considered parameters included: average Reynolds number (100


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