Piezoelectric translational agitation for enhancing forced-convection channel-flow heat transfer

Piezoelectric translational agitator (PTA) is proposed and its heat transfer performance is demonstrated by experiments in a narrow channel. For the present study, this channel simulates a portion of an air-cooled heat sink. An oval loop shell structure successfully generates millimeter-range translational displacement to a blade attached to the shell. A PTA operating at 961 Hz as its second resonance mode with a 1.4 mm displacement under 60 Liters Per Minute (LPM) of cross flow achieved about 55% improvement in heat transfer coefficient compared to the non-agitated state. Pressure drop in the test section and the corresponding power required to drive the flow through the channel against the oscillating blade were measured. In addition, the PTAs were tested in the open channel without through-flow to examine the sole effect of agitation and to investigate the possibility of using it as a stand-alone cooling device. A total Reynolds number was defined to characterize the combined effects of cross flow and agitation. The Stanton number developed from the relationship between the total Reynolds number and heat transfer coefficients enables predicting operating performance.